Dissertations / Theses on the topic 'And Astronomical Observations'
To see the other types of publications on this topic, follow the link: And Astronomical Observations.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'And Astronomical Observations.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Tshenye, Thapelo Obed. "Quality control of astronomical CCD observations." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/4409.
Full text
2
Eves, Benjamin Alistair Curtis. "Observations of magnetically driven events in astronomical systems." Thesis, Open University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434234.
Full text
3
Martin, Didier Dieudonné Elisabeth. "Development of superconducting tunnel junction arrays for astronomical observations." Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/58049.
Full text
4
Spreitzer, Teresa. "Construction and operation of a cloud detector to assist astronomical observations." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80879.
Full textAbstract:
The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a ground based gamma ray telescope which studies active galatic nuclei (AGNs). As a ground based experiment, data quality is directly related to atmospheric conditions. This thesis describes the process of verifying the reliability of astronomical weather predictions made by the Canadian Meteorological Service (CMS). This includes a description of the construction, calibration, and operation of a cloud detector at McGill University in Montreal, Canada. Cloud cover data was collected from the beginning of September, 2003, to the beginning of November 2003. These data were compared to cloud cover weather predictions made by the CMS. A blind analysis consisted of scaling the CMS and real data, and calculating the correlation coefficient between these two sets of data. The correlation between the predictions and real sky conditions was 0.4622, well above the 0.1% significance level of 0.1906 Thus the CMS is determined to be a reliable weather predictor, and useful to the STACEE group.
5
Hepworth, James Haydn. "Systems Development of a Two-Axis Stabilised Platform to Facilitate Astronomical Observations." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29449.
Full textAbstract:
Inertially Stabilised Platforms (ISPs) aim to control the line-of-sight between a sensor and a target. They perform two distinct operations; keeping track of the target as the sensor host and the target move in inertial space and attenuating rotational disturbances incurred to the sensor by host vehicle motion. This project aimed to develop a two-axis ISP for use in astronomical applications. It represents the initial development of all systems of a low-cost ISP designed for a 3.5” compound telescope. To achieve this, relevant literature describing the various components of an ISP were reviewed to inform the design, implementation and testing cycle which comprised most of the project. A set of system specifications was developed to guide design decisions. The performance of the implemented system was compared against these specifications once the project was complete. During the project, the electro-mechanical structure of the ISP was designed and implemented, including a mechanical assembly designed to mount a camera and inertially and geometrically model the specified telescope. This allowed the ISP to be tested at a lower cost than with the telescope itself. The associated electrical systems were specified and configured. An image processing script capable of detecting and locating the centre of the Moon in the camera field of view was written in Python and implemented on a Raspberry Pi Computer. A complete simulation model for the system was written in the simulation language, Simul_C_EM, and used to design various controllers for the ISP control system and help verify certain estimated system parameters such as gimbal friction. For each gimbal, PI controllers were designed to allow manual orientation control of the telescope, compensated P controllers were designed to achieve target tracking, and compensated PI controllers were designed to reject rotational disturbances. These were implemented in C on an STM32F0 microcontroller tasked with managing the various control and communications tasks required by the system. Finally, a user interface was written in LabVIEW to facilitate intuitive user control of the system and perform datalogging of the system runtime data. Testing of the system showed good correlation between the hardware and the simulated results indicating an accurate simulation model that can be used to test future design developments.
6
Travouilon, Tony Physics Faculty of Science UNSW. "Measurements of optical turbulence on the Antarctic Plateau and their impact on astronomical observations." Awarded by:University of New South Wales. Physics, 2005. http://handle.unsw.edu.au/1959.4/20852.
Full textAbstract:
Atmospheric turbulence results taken on the Antarctic plateau are presented in this thesis. Covering two high sites: South Pole and Dome C, this work describes their seeing and meteorological conditions. Using an acoustic sounder to study the turbulence profile of the first kilo- metre of the atmosphere and a Differential Image Motion Monitor (DIMM) to investigate the integrated seeing we are able to deduce important at- mospheric parameters such as the Fried parameter (r0) and the isoplanatic angle (??0). It was found that at the two sites, the free atmosphere (above the first kilometer) was extremely stable and contributed between 0.2" and 0.3" of the total seeing with no evidence of jet or vortex peaks of strong turbulence. The boundary layer turbulence is what differentiates the two sites. Located on the Western flank of the plateau, the South Pole is prone to katabatic winds. Dome C on the other hand is on a local maximum of the plateau and the wind conditions are amongst the calmest in the world. Also linked to the topography is the vertical extent of the temperature in- version that is required to create optical turbulence. At the South Pole the inversion reaches 300 m and only 30 m at Dome C. This difference results in relatively poor seeing conditions at the South Pole (1.8") and excellent at Dome C (0.27"). The strong correlation between the seeing and the ground layer meteorological conditions indicates that even better seeing could be found at Dome A, the highest point of the plateau. Having most of the turbulence near the ground is also incredibly ad- vantageous for adaptive optics. The isoplanatic angle is respectively 3.3" and 5.7" for the South Pole and Dome C. This is significantly larger than at temperate sites where the average isoplanatic angle rarely exceeds 2". This means that wider fields can be corrected without the complication of conjugation to specific layers. For such purpose the potential is even more interesting. We show that ground conjugated adaptive optics would decrease the natural seeing to 0.22" for a wide field of 10 and 0.47" for a field of 1" at the South Pole. At Dome C the results are less impressive due to the already excellent seeing, but a gain of 0.1"e can still be achieved over 1"e. These results show that high angular resolution observations can be done better on the Antarctic plateau than any other known site.
7
Carvalho, Fernando Pedro. "'Powellsnakes' : a fast Bayesian approach to discrete object detection in multi-frequency astronomical data sets." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/245147.
Full textAbstract:
In this work we introduce a fast Bayesian algorithm designed for detecting compact objects immersed in a diffuse background. A general methodology is presented in terms of formal correctness and optimal use of all the available information in a consistent unified framework, where no distinction is made between point sources (unresolved objects), SZ clusters, single or multi-channel detection. An emphasis is placed on the necessity of a multi-frequency, multi-model detection algorithm in order to achieve optimality. We have chosen to use the Bayes/Laplace probability theory as it grants a fully consistent extension of formal deductive logic to a more general inferential system with optimal inclusion of all ancillary information [Jaynes, 2004]. Nonetheless, probability theory only informs us about the plausibility, a ‘degree-of-belief ’, of a proposition given the data, the model that describes it and all ancillary (prior) information. However, detection or classification is mostly about making educated choices and a wrong decision always carries a cost/loss. Only resorting to ‘Decision Theory’, supported by probability theory, one can take the best decisions in terms of maximum yield at minimal cost. Despite the rigorous and formal approach employed, practical efficiency and applicability have always been kept as primary design goals. We have attempted to select and employ the relevant tools to explore a likelihood form and its manifold symmetries to achieve the very high computational performance required not only by our ‘decision machine’ but mostly to tackle large realistic contemporary cosmological data sets. As an illustration, we successfully applied the methodology to ESA’s (European Space Agency) Planck satellite data [Planck Collaboration et al., 2011d]. This data set is large, complex and typical of the contemporary precision observational cosmology state-of-the-art. Two catalogue products are already released: (i) A point sources catalogue [Planck Collaboration et al., 2011e], (ii) A catalogue of galaxy clusters [Planck Collaboration et al., 2011f]. Many other contributions, in science products, as an estimation device, have recently been issued [Planck et al., 2012; Planck Collaboration et al., 2011g,i, 2012a,b,c]. This new method is called ‘PowellSnakes’ (PwS).
8
Isaak, Katherine Gudrun. "Low-noise instrumentation and astronomical observations of high-redshift objects in submillimetre wavelengths." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364389.
Full text
9
Rojas, Folkers Eduardo. "Evaluation, design, and construction of the Wallace Astrophysical Observatory Camera for astronomical observations." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54464.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, June 2009."May 2008." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 53-54).
The goal of this thesis is to upgrade the scientific capabilities of the 24" Cassegrain reflector telescope at the George R. Wallace, Jr. Astrophysical Observatory (Wallace Observatory), part of Massachusetts Institute of Technology (MIT). The upgrade consists of evaluating, designing and constructing the Wallace Astrophysical Observatory Camera (WAOcam), optimized for 24" telescope. A full 3D model of the 24" telescope and dome was created to find the size restrictions for WAOcam. An optical model was also developed to maximize the field of view of the camera detector. WAOcam was designed using SolidWorks (3D modeling Software), the parts files from the designing process were also used to machine the instrument. The manufacturing of the WAOcam involved using the following: Computer Numerical Control (CNC) lathe, CNC mill, drill press, and a Waterjet (cutting machine). The manufacturing process also required learning of Omax (software for the Waterjet) and MasterCam 9.1 (software for the CNC lathe and CNC mill). The resulting product is WAOcam, which consists of three modules: 1) vacuum dewar (houses a CCD detector), 2) shutter (controls when light hits the camera detector), and 3) filter wheel (modifies the light before hitting the detector). The remaining work left on the WAOcam is the installation of two additional modules: 1) a four port instrument rotator and 2) a field rotator. This upgrade will allow for occultation observations, strip scanning surveys, and Kuiper Belt Object (KBOs) astrometry to be obtained using the 24" telescope.
by Folkers Eduardo Rojas.
S.B.
10
PENNING, WILLIAM ROY. "INVESTIGATIONS OF LONG-PERIOD DQ HERCULIS STARS." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/188161.
Full textAbstract:
The magnetic rotator model has long been the favored explanation for coherent photometric modulations in the DQ Herculis class of cataclysmic variables. However, to date, all evidence supporting this model has been of the indirect variety. Unlike their synchronously rotating cousins, the AM Herculis objects, DQ Herculis stars have not yet been discovered to emit polarized radiation. Therefore, in light of this crucial lack, the evidence used to place these objects in the magnetic cataclysmic variable category has been strictly circumstantial, based primarily on the coherence of the photometric periodicities. In this work, time-resolved spectroscopy of four long-period DQ Herculis stars is performed. In addition, two of the same objects are observed with a new, sensitive circular polarimeter. Chapters II and III describe these observations and the results of each. To summarize, coherent variations in the wavelength of emission lines were found with the spectroscopic observations. A model is put forth, explaining this phenomenon as being due to varying illumination from a bright spot on the primary. This, of course, adds strength to the magnetic rotator model. Secondly, circular polarization was definitely found in one object studied, and possibly in a second. Therefore, for the first time, there is direct evidence of the magnetic nature of these binaries. In Chapter IV, the model of the rotating bright spot illuminating the disk is explored in further detail, including modeling with a minicomputer. Afterward, a problem brought out by the low polarization coupled with large amplitude photometric variations and a cool spectrum is investigated, namely, is it possible to produce large amounts of cyclotron radiation without producing large amounts of circular polarization? The results tend to show that, for a large emitting area, the answer is yes. Chapter V is a summary of the rest of the work.
11
SYKES, MARK VINCENT. "INFRARED ASTRONOMICAL SATELLITE OBSERVATIONS OF ASTEROID DUST BANDS AND COMETARY DUST TRAILS (COLLISIONS, DEBRIS, SOLAR SYSTEM)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183974.
Full textAbstract:
Analysis of data from the Infrared Astronomical Satellite (IRAS) resulted in the discovery of bands of dust surrounding the inner solar system, consisting of asteroid collision debris (Low et al., 1984). Narrow trails of dust were also discovered tracking the orbits of a number of short-period comets (Sykes et al., 1986). Pairs of dust bands are the product of individual collisional events in the asteroid belt. A dynamical model is developed which shows how the orbits of debris from such collisions evolve to form a band pair. A model of the surface area evolution of such bands is also developed which, coupled with asteroid collision theories, indicates that some of the observed dust bands are the consequence of the disruption of ∼10 km diameter asteroids within the last ∼10⁷ years. Observations of other bands are consistant with more ancient disruptions of much larger asteroids, which resulted in the formation of the Koronis and Themis asteroid families. However, the hypothesis that all dust bands represent the small-particle (∼1 mm) members of the Hirayama families is inconsistent with the IRAS data. Dust particles composing the bands are small enough to have experienced some orbital decay due to Poynting-Robertson drag. From the above models, it is possible to account for the bulk of the zodiacal thermal emission, increasing the importance of asteroid collisions as a source of interplanetary dust. Lower limits on the ages of the major asteroid families are derived. Cometary dust trails consist of particles hundreds of microns and larger in diameter, ejected at low velocities (m/s) from the parent comet, and spreading out ahead and behind the comet's position along its orbital path, the initial stages in the evolution of meteor streams. Dust trails are found in association with short-period comets as diverse as P/Encke (perihelion distance, q = .33 AU) and P/Schwassmann-Wachmann 1 (q = 5.43 AU). Analysis of dust trails indicates possible differences in structure and composition among comet nuclei. Preliminary results from a survey of dust trails in the IRAS data indicate the presence of a large number of previously unobserved short-period comets.
12
Jeffers, Sandra Victoria. "Surface brightness distributions of late-type stars." Thesis, University of St Andrews, 2005. http://hdl.handle.net/10023/12941.
Full textAbstract:
The aim of this work has been to increase our understanding of the surface brightness distributions of late-type stars through Doppler imaging and eclipse mapping techniques. Combining spectroscopic and photometric observations with the technique of Doppler Imaging, I have reconstructed surface images of the G2V star He 699 (for 08 October 2000), which show high latitude and polar structures. In the case of the KOV star AB Dor, the Doppler images for January 1992 and November 1993 show a large polar cap with small dark features also present at intermediate to high latitudes. As the phase sampling of the observations was insufficient to apply the sheared-image method it was not possible to detect any differential rotation. In the second part of my thesis I determine the surface brightness distribution of the primary component of the RS CVn eclipsing binary SV Cam. I have used extrapolated size distributions of sunspots to an active star to synthesize images of stellar photospheres with high spot filling factors. The resulting surface images, reconstructed with the Maximum Entropy eclipse mapping technique, show large spurious spot features at the quadrature points. It is concluded that two-spot modelling or chi-squared minimisation techniques are more susceptible to spurious structures being generated by systematic errors, arising from incorrect assumptions about photospheric surface brightness, than simple Fourier analysis of the light-curves. Spectrophotometric data from 9 HST orbits, observed in November 2001, have been used to eclipse-map the primary component of SV Cam. In combination with its HIPPAR- COS parallax it is found that the surface flux in the eclipsed low-latitude region is about 30% lower than computed from the best fitting PHOENIX model atmosphere. This flux deficit can only be accounted for if about a third of the primary's surface is covered with unresolved spots. However, when the spottedness from the eclipsed region is applied to the entire surface of the primary star, there still remains an unaccounted flux deficit. The remaining flux deficit is explained by the presence of a large polar spot extending down to latitude 48+/-6 deg. When the Maximum Entropy eclipse mapping technique is used to fit SV Cam's lightcurve, the observed minus computed residuals show strong spurious peaks at the quadrature points. It is only possible to reduce these peaks with the addition of a polar cap and the reduction of the primary star's temperature, to account for the star being peppered with unresolvable spots. Motivated by this result we investigate the limb darkening of the primary component of SV Cam. The wavelength dependence of the limb darkening is analysed by sub-dividing the HST lightcurve into 10 bands of equal emission flux. Flux variations between the first and fourth contact of the primary eclipse indicate that the limb darkening decreases towards longer wavelengths, in accordance with published limb darkening laws. Comparing fits of ATLAS and PHOENIX model atmospheres we find a wavelength dependence of the best fitting model. Due to its smooth cutoff at the stellar limb, the spherical geometry of the PHOENIX model atmosphere gives the best fit during partial eclipse. Between the second and third contact the difference between spherical and plane-parallel geometry is less important.
13
Laag, Edward Aric. "Observations of starburst galaxies science and supporting technology /." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957320791&SrchMode=2&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268854875&clientId=48051.
Full textAbstract:
Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 16, 2010). Includes bibliographical references. Also issued in print.
14
Chantzos, Johanna [Verfasser], and Paola [Akademischer Betreuer] Caselli. "High resolution spectroscopy of molecules of astrophysical interest and radio astronomical observations of star forming regions / Johanna Chantzos ; Betreuer: Paola Caselli." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1209472864/34.
Full text
15
Neyskens, Pieter. "Exploring S stars: stellar parameters, abundances and constraints on the s-process from a new grid of model atmospheres." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209358.
Full textAbstract:
More than 80% of the stars in the Universe are expected to have initial masses below eight to ten times the mass of our sun. These low mass stars, including our sun, become cool red giants during one of the final evolutionary stages of their life: the Asymptotic Giant Branch (or AGB) phase. AGB stars are among the main producers of carbon and heavy (s-process) elements in the Universe. These elements are synthesized inside the star and mixed to the stellar atmosphere where stellar winds are responsible for the loss of more than 50% of the stellar mass, hence, AGB stars are strong polluters of the interstellar medium. The ejected material can clump together into dusty particles which may serve as ingredients for the birth of new stars and planets. When most of the AGB stellar envelope is lost, the AGB star stops releasing nuclear energy from interior processes and swaps its giant face for a planetary nebulae look, whereafter it fades away as a white dwarf.The dredge-up of carbon and s-process elements into the AGB atmosphere causes an important chemical anomaly among them: initial oxygen-rich stars (M stars) are transformed into carbon-rich stars (C stars). As a consequence, a group of oxygen-rich AGB stars exists which makes the transition between M and C stars. These transition stars are classified as S.
Although AGB stars are identified as producers of heavy elements, their nucleosynthesis and mixing processes are weakly constrained due to large uncertainties on their estimated temperature, gravity and chemical composition. Stronger constraints on the atmospheric parameter space, hence interior processes, of AGB stars can be obtained by investigating the atmosphere of S stars. Since they are transition objects on the AGB, they trace the rise of the s-process. S stars are less numerous than C stars, but their optical spectra are brighter making it easier to identify atomic and molecular lines. Therefore, S stars belong to the most interesting objects along the AGB to perform this task.
From a practical point of view, the spectra of S stars are extremely difficult to study since they are dominated by different, overlapping molecular bands, and the spectral shape may vary strongly from star to star due to their transition status. Therefore, tailored model atmospheres for S stars are of utmost importance to understand the spectroscopic, and even photometric, changes in terms of variations in the atmospheric parameters. A comparison between the models and observations aims not only at constraining the atmospheric parameter space of S stars, it will also test the reliability of 1D state-of-the-art model atmospheres for such complex stars.
From an evolutionary point of view, the S-star family is contaminated with stars who gained their atmospheric enrichment in heavy elements from a companion star. Evidences were found that these binary S stars are not at all located on the AGB, hence, they are labelled as extrinsic S stars while S stars on the AGB are labelled as intrinsic. The difference in evolutionary stages between intrinsic and extrinsic S stars was already found 20 years ago, however, a separation in terms of surface temperature, gravity and chemical composition is not well-established due to the lack of S-star model atmospheres. Such a distinction in atmospheric parameters will facilitate the discovery of these intruders and even help to calibrate stellar evolutionary models of single and binary stars.
To achieve these goals, the first step consists in the construction of a grid of model atmospheres for S stars. The grid will be used to quantify the influence of atmospheric parameters on the model structure and emergent flux. These results will be analyzed to derive precise atmospheric parameters of observed S stars, using a set of well-defined photometric and spectroscopic indices. Once the best model atmosphere has been selected for all observed S stars, their atmospheric parameters will be discussed in view of their evolutionary stage. The best-fitting model atmosphere will also be used to derive abundances from spectral syntheses. The abundance profiles are compared with stellar evolution model prediction to constrain nucleosynthesis and mixing processes inside S stars. Derived abundances of unstable elements will be used to estimate, for the first time, the age of AGB stars. Finally, their abundance profile will be discussed as a function of their time spent on the AGB.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
16
Clark, Stephen J. "The intuitive and the intellectual aspects of personal compositional voice and its complex and intuitive processes in relation to astronomical observations and elementary and advanced performers /." View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/38730.
Full textAbstract:
Thesis (Ph.D.) -- University of Western Sydney, 2008.A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy awarded by the School of Communication Arts, College of Arts, University of Western Sydney. Includes bibliography.
17
Trahin, Boris. "Étalonnage de l'échelle des distances dans l'ère Gaia : les étoiles pulsantes RR Lyrae et Céphéides." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEO018.
Full textAbstract:
Les étoiles pulsantes sont utilisées pour estimer les distances dans l’Univers, au moyen de la relation liant leur période de pulsation à leur magnitude absolue. La calibration de cette relation période-luminosité est réalisée via la détermination de distances indépendantes, notamment par la méthode de la parallaxe de pulsation. Cependant, la précision de cette méthode est aujourd’hui encore principalement limitée par le facteur de projection (p-facteur), un paramètre permettant de remonter à la vitesse pulsante de l’étoile à partir des vitesses radiales mesurées par spectroscopie. Mon travail de thèse a consisté à utiliser le code SPIPS (Spectro-Photo-Interferometry of Pulsating Stars) afin de parvenir à une détermination précise du p-facteur. Reprenant le principe de la parallaxe de pulsation, ce code permet d’obtenir une meilleure précision statistique des paramètres fondamentaux d’une étoile pulsante, grâce à une modélisation simultanée des observables spectroscopique, photométrique et interférométrique. L’utilisation de cette méthode en fixant une distance mesurée indépendamment permet alors de remonter à la valeur du p-facteur. En vue d’une utilisation à grande échelle du code SPIPS, j’ai effectué dans un premier temps un important travail d’optimisation et de collecte de données de la littérature. Ces catalogues ainsi que diverses observations réalisées tout au long de ces trois années (avec entre autres l’instrument PIONIER du VLTI) m’ont permis de construire une base de données complète et homogène de plus de 300 étoiles. L’objectif de ma thèse fût alors d’appliquer le code SPIPS à un large échantillon d’étoiles, en utilisant les parallaxes du second catalogue du satellite Gaia. Au moyen de ces parallaxes, j’ai tout d’abord pu calculer avec précision le p-facteur de quelques variables de type RR Lyrae. Appliqué dans un second temps à un plus grand échantillon de Céphéides, le code SPIPS m’a permis de déterminer une relation linéaire entre le p-facteur et la période de pulsation, aboutissant à un nouvel étalonnage de la relation période-luminosité. Ces résultats prometteurs du code SPIPS laissent envisager que les prochaines publications de données du satellite Gaia permettront de lever le voile sur la nature du p-facteur, remettant ainsi au premier plan la méthode de la parallaxe de pulsation dans l’étalonnage de l’échelle des distances et la détermination de la constante de HubblePulsating stars are used to determine distances in the Universe owing to the relation between their pulsation period and absolute magnitude. The calibration of this period-luminosity relation is performed through the determination of independant distances, in particular with the parallax of pulsation method. However, the accuracy of this method is still mainly limited by the projection factor, a parameter used to convert radial velocities measured from spectroscopy into the true pulsating velocity of the star. The objective of this thesis is to use the SPIPS (Spectro-Photo-Interferometry of Pulsating Stars) algorithm to precisely determine this p-factor. Based on the parallax of pulsation approach, this code allows to obtain a better precision on the fundamental parameters of a pulsating star, thanks to a simultaneous modeling of the observables (spectroscopy, photometry and interferometry). Using this method while fixing an independent distance estimate allowed me to retrieve the value of the p-factor. In view of a large scale use of the SPIPS code, I first did an important work of optimization and data collection. These catalogs as well as various observations I made throughout these three years (with among others the PIONIER instrument of the VLTI) allowed me to create a complete and heterogeneous database of more than 300 stars. I then apply the SPIPS algorithm to a large sample of stars using the parallaxes from the second data release of the Gaia satellite. Using these parallaxes, I was first able to accurately calculate the p-factor of some RR Lyrae type variables. Applied to a larger sample of Cepheids, the SPIPS code allowed me to determine a linear relation between the p-factor and the pulsation period, resulting in a new calibration of the period-luminosity relation. These promising results of the SPIPS code suggest that the future releases of the Gaia satellite will unveil the nature of the p-factor, bringing the parallax of pulsation method to the forefront of in the calibration of the distance scale and the determination of the Hubble constant
18
饒勇 and Yong Rao. "The astronomical observation system of 12" telescope: its automatic control system and astronomical application." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31214587.
Full text
19
Rao, Yong. "The astronomical observation system of 12" telescope : its automatic control system and astronomical application /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1877698X.
Full text
20
Jiang, Feng. "Capturing event metadata in the sky : a Java-based application for receiving astronomical internet feeds : a thesis presented in partial fulfilment of the requirements for the degree of Master of Computer Science in Computer Science at Massey University, Auckland, New Zealand." Massey University, 2008. http://hdl.handle.net/10179/897.
Full textAbstract:
When an astronomical observer discovers a transient event in the sky, how can the information be immediately shared and delivered to others? Not too long time ago, people shared the information about what they discovered in the sky by books, telegraphs, and telephones. The new generation of transferring the event data is the way by the Internet. The information of astronomical events is able to be packed and put online as an Internet feed. For receiving these packed data, an Internet feed listener software would be required in a terminal computer. In other applications, the listener would connect to an intelligent robotic telescope network and automatically drive a telescope to capture the instant Astrophysical phenomena. However, because the technologies of transferring the astronomical event data are in the initial steps, the only resource available is the Perl-based Internet feed listener developed by the team of eSTAR. In this research, a Java-based Internet feed listener was developed. The application supports more features than the Perl-based application. After applying the rich Java benefits, the application is able to receive, parse and manage the Internet feed data in an efficient way with the friendly user interface. Keywords: Java, socket programming, VOEvent, real-time astronomy
21
Court, A. J. "Hard X-ray astronomy from balloon altitudes." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377796.
Full text
22
Miret, Roig Núria. "COSMIC-DANCE : A comprehensive census of nearby star forming regions." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0327.
Full textAbstract:
Comprendre comment se forment les étoiles est l’une des questions fondamentales auxquelles l’astronomie entend répondre. Malheureusement, nous ne pouvons pas étudier la formation stellaire en temps réel et différentes méthodes indirectes doivent être utilisées pour faire la lumière sur ce sujet. L’objectif principal de cette thèse est de déterminer la fonction de masse initiale, la distribution de masse des étoiles à leur naissance, dans différentes associations et régions de formation d’étoiles. La fonction de masse est le produit direct de la formation stellaire et constitue donc un paramètre d’observation fondamental pour contraindre les théories de formation stellaire et sous-estellaire. Nous nous sommes concentrés sur l’amas ouvert de 30 Ma IC 4665 et la région de formation d’étoiles de 1 - 10 Ma de Upper Scorpius (USC) et r Ophiuchi (r Oph). Nous avons combiné l’astrométrie et la photométrie de Gaia Data Release 2 avec nos observations au sol pour préparer un catalogue profond et étendu de chaque région. Ensuite, nous avons calculé les probabilités d’appartenance en utilisanttoute l’astrométrie et la photométrie disponibles et identifié les membres à haute probabilité. Nous avons utilisé la liste finale des membres pour estimer la distribution de magnitude, et les fonctions de luminosité et masse de ces associations. Alors que la première a l’avantage d’être indépendante des modèles d’évolution, tandis que les fonctions de luminosité et de masse peuvent être utilisées pour contraindre les mécanismes de formation d’étoiles. L’étude d’IC 4556 nous a permis d’identifier des objets sous-stellaires, sans pour autant pouvoir fournir un recensement complet dans ce domaine de masse. Dans USC et r Oph, nous avons identifié une population très riche d’objets sous-stellaires, significativement plus nombreux que les prédictions des modèles de formation par effondrement de coeurs moléculaires, suggérant que la formation de naines brunes et d’objets de masses planétaires isolés par des phénomènes d’éjection dans des systèmes planétaires a une contribution importante et du même ordre que l’effondrement des coeurs moléculaires à la population finale d’objets dans un amas. L’âge est un paramètre fondamental pour étudier la formation et l’évolution des étoiles pour plusieurs raisons: premièrement puisqu’il établit une échelle de temps sur laquelle placer les observations. Deuxièmement car il est essentiel pour convertir les luminosités en masses, avec l’aide de modèles d’évolution stellaire. Les incertitudes sur l’age de USC et r Oph se traduisant en erreurs importantes dans notre estimation de la fonction de masse, j’ai développé une stratégie d’étude de "l’âge dynamique" au moyen d’une analyse orbitale de traçage des mouvements des membres d’associations jeunes. J’ai ainsi mis au point une stratégie incluant i) les observations et la recherche de données dans les archives publiques, ii) la réduction et l’analyse des spectres échelles obtenus; iii) et l’analyse dynamique, pour déterminer l’âge d’une association. La méthodologie, développée avec l’association b Pictoris (b Pic), est prête à être appliquée à d’autres régions et en particulier à USC et r Oph. Les membres que nous avons identifiés sont par ailleurs d’excellentes cibles pour des études complémentaires telles que la recherche de disques (produit également fondamental de la formation stellaire), d’exoplanètes, de système multiples, mais aussi pour la caractérisation des atmosphères et propriétés physiques des naines brunes et des planètes errantes. [...]Understanding how stars form is one of the fundamental questions which astronomy aims to answer. Currently, it is well accepted that the majority of stars form in groups and that their predominant mechanism of formation is the core-collapse. However, several mechanisms have been suggested to explain the formation of substellar objects, and their contribution is still under debate. The main goal of this thesis is to determine the initial mass function, the mass distribution of stars at birth time, in different associations and star-forming regions. The mass function constitutes a fundamental observational parameter to constrain stellar and substellar formation theories since different formation mechanisms predict different fraction of stellar and substellar objects. We used the Gaia Data Release 2 catalogue together with ground-based observations from the COSMIC-DANCe project to look for high probability members via a probabilistic model of the distribution of the observable quantities in both the cluster and background populations. We applied this method to the 30 Myr open cluster IC 4665 and the 1 - 10 Myr star-forming region Upper Scorpius (USC) and r Ophiuchi (r Oph). We found very rich populations of substellar objects which largely exceed the numbers predicted by core-collapse models. In USC, where our sensitivity is best, we found a large number of free-floating planets and we suggest that ejection from planetary systems must have a similar contribution than core-collapse in their formation. The age is a fundamental parameter to study the formation and evolution of stars and is essential to accurately convert luminosities to masses. For that, we also presented a strategy to study the dynamical traceback age of young local associations through an orbital traceback analysis. We applied this method to determine the age of the b Pictoris moving group and in the future, we plan to apply it to other regions such as USC. The members we identified with the membership analysis are excellent targets for follow-up studies such as a search for discs, exoplanets, characterisation of brown dwarfs and free-floating planets. I this thesis, we presented a search for discs hosted by members of IC 4665 and we found six excellent candidates to be imaged with ALMA or the JWST. The tools we developed, are ready to be used in other regions such as USC and r Oph, where we expect to find a larger number of disc-host stars
23
Leverington, David. "The cost and citation-based effectiveness of observational astronomical facilities since 1958." Thesis, Open University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363964.
Full text
24
Bellagamba, Fabio <1983>. "Testing future weak lensing surveys through simulations of observations." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4762/.
Full textAbstract:
Weak lensing experiments such as the future ESA-accepted mission Euclid aim to measure cosmological parameters with unprecedented accuracy. It is important to assess the precision that can be obtained in these measurements by applying analysis software on mock images that contain many sources of noise present in the real data. In this Thesis, we show a method to perform simulations of observations, that produce realistic images of the sky according to characteristics of the instrument and of the survey. We then use these images to test the performances of the Euclid mission. In particular, we concentrate on the precision of the photometric redshift measurements, which are key data to perform cosmic shear tomography. We calculate the fraction of the total observed sample that must be discarded to reach the required level of precision, that is equal to 0.05(1+z) for a galaxy with measured redshift z, with different ancillary ground-based observations. The results highlight the importance of u-band observations, especially to discriminate between low (z < 0.5) and high (z ~ 3) redshifts, and the need for good observing sites, with seeing FWHM < 1. arcsec. We then construct an optimal filter to detect galaxy clusters through photometric catalogues of galaxies, and we test it on the COSMOS field, obtaining 27 lensing-confirmed detections. Applying this algorithm on mock Euclid data, we verify the possibility to detect clusters with mass above 10^14.2 solar masses with a low rate of false detections.
25
Sasyn, Jan. "Staniční testování Mobilního automatizovaného astronomického systému." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226224.
Full textAbstract:
Subject of this master´s thesis is a station testing of Mobile automated astronomical system No. 1 (MAAS – 1). This system is used for measurement of astronomical coordinates by measurments of the stars. This thesis is focused on impact of some systematic effects, especially effects of inaccurate input geographic coordinates to resulting coordinates.
26
Santiago, Arthur Vinícius Resek. "O potencial da observação no ensino de astronomia: o estudo do conceito de energia." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/81/81131/tde-10092015-155110/.
Full textAbstract:
Considerando a forte relação entre a Astronomia e a Física, a pesquisa apresentada propõe focalizar uma atividade de ensino que, partindo da observação do céu, com motivação para compreendê-lo, indo além da admiração e do deslumbramento, leve à elaboração de conceitos da Física escolar. A pesquisa trata de investigar uma forma de desenvolver o conceito de energia partindo de uma observação astronômica, onde os aprendizes são participantes ativos no processo da sua aprendizagem. Foi desenvolvida uma sequência didática e aplicada a alunos do Ensino Médio de uma escola pública de São Paulo. O objetivo era motivar os alunos a observar um fenômeno celeste, as crateras lunares, para construir o conceito de energia mecânica, num processo com as etapas de: observação, obtenção de dados pertinentes e adequados, levantamento de hipóteses e verificação num experimento controlado no laboratório escolar. Todas as atividades foram registradas em áudio ou vídeo e, com base nas transcrições, foi realizada uma análise textual discursiva. A análise permitiu qualificar as observações sob diferentes aspectos, bem como revelar as concepções expressas na tentativa de modelar, no laboratório escolar, uma possível causa das crateras observadas. Em todo o trabalho foi notável o papel fundamental do professor como mediador; a atenção para acompanhar a argumentação dos alunos e orientar as atividades parece ter garantido resultados de aprendizagem. A teoria de Vigotski foi considerada para interpretar os resultados sobre a construção de conceitos. Como resultados foram obtidas categorias sobre como se dão as observações realizadas pelos alunos, saindo de uma Observação Primária, evoluindo até uma Observação Qualificada. E também quais as relações que se estabelecem ao investigar um problema para que o conceito de energia mecânica crie significado para o aluno, Relações entre as grandezas e o conceito, até a Relação de Terceiro Grau, entre conceito e fenômeno.In view of the strong relationship between Astronomy and Physics the proposed research aims to focus on a teaching activity that starts from the sky observation with an understanding motivation that lies beyond admiration and bewilderment and that may lead to the elaboration of school Physics concepts. The research deals with the investigation of a way of developping the concept of energy, starting from astronomical observations where students take active part in their learning process. A didactic sequence was elaborated and applied to secondary school students at a São Paulo public school. The objective was to motivate students to observe a celestial phenomenom, namely lunar craters, in order to build up the concept of mechanical energy in a process with the following steps: observation, obtention of related and adequate data, possible hypothesis and verification with a school laboratory controlled experiment. All activities were recorded in audio or video and with the aid of transcriptions a textual discursive analysis was effected. This analysis enabled a qualification of observations under several points of view as well as disclosing conceptions that were expressed in an atempt to model, in the school laboratory, a possible cause for the observed craters. The role played by the teacher during the whole process was essential as a moderator; his attention to follow the students argumentation and drive activities seems to have secured learning results. Vigotski theory was considered for interpreting results respect to construction of concepts. As results were obtained classes of observations made by the students, leaving a Primary Observation, evolving into a Qualified Observation. And what are the relationships that are established to investigate a problem that the mechanical energy concept create meaning to the student, relations between quantities and the concept, to the third degree of relationship, between concept and phenomenon.
27
Daigle, Olivier. "Spectro-imagerie optique à faible flux et comparaison de la cinématique Hα et HI d'un échantillon de galaxies proches." Aix-Marseille 1, 2010. http://www.theses.fr/2010AIX10141.
Full textAbstract:
Un nouveau contrôleur de EMCCD (Electron multiplying Charge Coupled Device) est présenté. Il permet de diminuer significativement le bruit qui domine lorsque la puce EMCCD est utilisé pour du comptage de photons: le bruit d'injection de charge. À l'aide de ce contrôleur, une caméra EMCCD scientifique a été construite, caractérisée en laboratoire et testée à l'observatoire du mont Mégantic. Cette nouvelle caméra permet, entre autres, de réaliser des observations de la cinématique des galaxies par spectroscopie de champ intégral par interférométrie de Fabry-Perot en lumière Ha beaucoup plus rapidement, ou de galaxies de plus faible luminosité, que les caméras à comptage de photon basées sur des tubes amplificateurs. Le temps d'intégration nécessaire à l'obtention d'un rapport signal sur bruit donné est environ 4 fois moindre qu'avec les anciennes caméras. Les applications d'un tel appareil d'imagerie sont nombreuses: photométrie rapide et faible flux, spectroscopie à haute résolution spectrale et temporelle, imagerie limitée par la diffraction à partir de télescopes terrestres (lucky imaging), etc. D'un point de vue technique, la caméra est dominée par le bruit de Poisson pour les flux lumineux supérieurs à 0. 002 photon/pixel/image. D'un autre côté, la raie d'hydrogène neutre (HI) à 21 cm a souvent été utilisée pour étudier la cinématique des galaxies. L'hydrogène neutre a l'avantage de se retrouver en quantité détectable au-delà du disque optique des galaxies. Cependant, la résolution spatiale de ces observations est moindre que leurs équivalents réalisés en lumière visible. Lors de la comparaison des données HI, avec des données à plus haute résolution, certaines différences étaient simplement attribuées à la faible résolution des observations HI. Le projet THINGS (The HI Nearby Galaxy Survey a observé plusieurs galaxies de l'échantillon SINGS (Spitzer Infrared Nearby Galaxies Survey). Les données cinématiques du projet THIGNS seront comparées aux données cinématiques obtenues en lumière Ha, afin de déterminer si la seule différence de résolution spatiale peut expliquer les différences observées. Les résultats montrent que des différences intrinsèques aux traceurs utilisées (hydrogène neutre ou ionisé), sont responsables de dissemblances importantes. La compréhension de ces particularités est importante: la distribution de la matière sombre, dérivée de la rotation des galaxies, est un test de certains modèles cosmologiquesA new EMCCD (Electron multiplying Charge Coupled Device) controller is presented. It allows the EMCCD to be used for photon counting by drastically taking down its dominating source of noise : the clock induced charges. A new EMCCD camera was built using this controller. It has been characterized in laboratory and tested at the observatoire du mont Mégantic. When compared to the previous generation of photon counting cameras based on intensifier tubes, this new camera renders the observation of the galaxies kinematics with an integral field spectrometer with a Fabry-Perot interferometer in Ha light much faster, and allows fainter galaxies to be observed. The integration time required to reach a given signal-to-noise ratio is about 4 times less than with the intensifier tubes. Many applications could benefit of such a camera: fast, faint flux photometry, high spectral and temporal resolution spectroscopy, earth-based diffraction limited imagery (lucky imaging), etc. Technically, the camera is dominated by the shot noise for flux higher than 0. 002 photon/pixel/image. The 21 cm emission line of the neutral hydrogen (HI) is often used to map the galaxies kinematics. The extent of the distribution of the neutral hydrogen in galaxies, which goes well beyond the optical disk, is one of the reasons this line is used so often. However, the spatial resolution of such observations is limited when compared to their optical equivalents. When comparing the HI data to higher resolution ones, some differences were simply attributed to the beam smearing of the HI caused by its lower resolution. The THINGS (The HI Nearby Galaxy Survey) project observed many galaxies of the SINGS (Spitzer Infrared Nearby Galaxies Survey) project. The kinematics of THINGS will be compared to the kinematic data of the galaxies obtained in Ha light. The comparison will try to determine whether the sole beam smearing is responsible of the differences observed. The results shows that intrinsic dissimilarities between the kinematical tracers used are responsible of some of the observed disagreements. The understanding of theses differences is of a high importance as the dark matter distribution, inferred from the rotation of the galaxies, is a test to some cosmological models
28
Jalovecký, Martin. "Analýza přesnosti výsledků astronomického určení polohy." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225609.
Full textAbstract:
This diploma thesis is focused on the analysis of results accuracy of astronomical positioning. It describes observation methods and the latest surveying systems used in geodetic astronomy. Further in the thesis there is the description of surveying system MAAS-1. Subject of the elaboration is the data obtained by measuring with this system. Testing is focused on digital camera. There is also an analysis of the results of geographical coordinates, depending on the accuracy of determining the angled pixel size and also on the accuracy of the input coordinates.
29
Marinoni, Silvia <1975>. "Procedures of quality control and data analysis of multi-site ground-based observations for the absolute flux calibration of Gaia." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3707/.
Full textAbstract:
The Gaia space mission is a major project for the European astronomical community. As challenging as it is, the processing and analysis of the huge data-flow incoming from Gaia is the subject of thorough study and preparatory work by the DPAC (Data Processing and Analysis Consortium), in charge of all aspects of the Gaia data reduction. This PhD Thesis was carried out in the framework of the DPAC, within the team based in Bologna. The task of the Bologna team is to define the calibration model and to build a grid of spectro-photometric standard stars (SPSS) suitable for the absolute flux calibration of the Gaia G-band photometry and the BP/RP spectrophotometry. Such a flux calibration can be performed by repeatedly observing each SPSS during the life-time of the Gaia mission and by comparing the observed Gaia spectra to the spectra obtained by our ground-based observations. Due to both the different observing sites involved and the huge amount of frames expected (≃100000), it is essential to maintain the maximum homogeneity in data quality, acquisition and treatment, and a particular care has to be used to test the capabilities of each telescope/instrument combination (through the “instrument familiarization plan”), to devise methods to keep under control, and eventually to correct for, the typical instrumental effects that can affect the high precision required for the Gaia SPSS grid (a few % with respect to Vega). I contributed to the ground-based survey of Gaia SPSS in many respects: with the observations, the instrument familiarization plan, the data reduction and analysis activities (both photometry and spectroscopy), and to the maintenance of the data archives. However, the field I was personally responsible for was photometry and in particular relative photometry for the production of short-term light curves. In this context I defined and tested a semi-automated pipeline which allows for the pre-reduction of imaging SPSS data and the production of aperture photometry catalogues ready to be used for further analysis. A series of semi-automated quality control criteria are included in the pipeline at various levels, from pre-reduction, to aperture photometry, to light curves production and analysis.
30
Garcia, Garcia Carlos. "Theories of gravitation confronted with cosmological observations." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/670878.
Full textAbstract:
This thesis studies Dark Energy, a central topic of Modern Cosmology, from different points of view. It covers from models and parametrizations to likelihood approximations for the observations of the Large Scale Structure (LSS) of the Universe, which are vital for model constraining, as well as for our study of the S8 tension.
The studied model is the α-attractors dark energy model, which reproduces current observations thanks to its capability to mimic a cosmological constant. It is inspired on the Planck-favored inflationary class of models α-attractors and links the inflationary and dark energy periods with the same scalar field. Fortunately, next-generation surveys might be able to distinguish it from ΛCDM by up to 3σ of confidence.
Nevertheless, in order to make the most of forthcoming data, we need a formalism that allows us to test models in an efficient way. This could be a observational and theoretical constrained parametrization. We show the case of w0 -wa for thawing quintessence. This parametrization is able to reproduce the observables from recombination to the present when chosen smartly. In addition, their probability distributions built from purely theoretical considerations allow us to restrict the observational bounds to the theoretically motivated area. This work shows how we can work with very general theories such as Horndeski.
However, the observational constraints also depend on the correct estimation of their likelihood. Therefore, we have developed (and implemented in NaMaster, from LSST DESC) the Narrow Kernel Approximation (NKA) for the Gaussian (not causally connected) part of the LSS pseudo-Cl covariance matrix. This allows to reproduce accurately the cosmological parameters’ posterior distribution while reducing the computational cost from O(lmax6) (exact computation) to O(lmax3). For sure, the exact computation will be intractable for the next-generation LSS observations, which will resolve really small scales.
The NKA has allowed us to start our study of the origin of the S8 tension reported by KiDS-450. With data of LSS from DES and data of CMB from Planck, we want to obtain the temporal evolution of S8 and compare it with that given by KiDS-450 data.
Summing up, this thesis has covered dark energy models and developed accurate methods to test their viability in an efficient way. Furthermore, it has gone closer to data and developed the NKA that allows to accurately estimate the LSS likelihood, making it possible for us to study the origin of the S8 tension.Esta tesis estudia la energía oscura, un tema central en la Cosmología Moderna, desde diferentes puntos de vista. Cubre desde modelos y parametrizaciones, hasta aproximaciones de la likelihood de observaciones de la Estructura a Gran Escala del Universo (LSS), vitales para constreñir los modelos, como para nuestro estudio de la tensión en S8. El modelo estudiado es el de energía oscura de α-attractors, que reproduce las observaciones actuales al poder asemejarse a una constante cosmológica. Inspirado en la clase de modelos de inflación favorecidos por Planck, α-attractors, enlaza el periodo de inflación y energía oscura mediante el mismo campo escalar. Afortunadamente, las misiones futuras podrían diferenciarlo de ΛCDM con hasta 3σ de confianza. No obstante, aprovechar al máximo los datos futuros requiere un formalismo que nos permita comprobar la viabilidad de los modelos eficientemente, como una parametrización acotada observacional y teóricamente. Mostramos el caso de w0-wa para quintaesencia de tipo thawing, que reproduce los observables desde recombinación hasta hoy, si se eligen apropiadamente. Construidas sus distribuciones de probabilidad bajo condiciones puramente teóricas, nos permiten restringir las cotas observacionales a la zona teóricamente motivada. Este trabajo es una muestra de cómo podemos trabajar con teorías muy generales como Horndeski. Pero las cotas observacionales dependen también de una correcta estimación de su likelihood. Por ello, hemos desarrollado (e implementado en NaMaster, del LSST DESC) la Narrow Kernel Approximation (NKA) para la parte gausiana (causalmente no conectada) de la covarianza de los pseudo-Cl de LSS. Ésta permite obtener con exactitud las cotas en los parámetros cosmológicos, al tiempo que reduce el coste computacional de O(lmax⁶) (cómputo exacto) a O(lmax3). Claramente, el cómputo exacto es inviable para las observaciones futuras de LSS que resolverán escalas muy pequeñas. La NKA nos ha permitido empezar a estudiar el origen de la tensión en S8 reportada por KiDS-450. Con datos de LSS de DES y del CMB de Planck, pretendemos obtener la evolución temporal de S8 y compararla con la dada por los datos de KiDS-450. En resumen, esta tesis ha trabajado en modelos de energía oscura y desarrollado métodos precisos para comprobar su viabilidad de manera eficiente. Además, se ha acercado a los datos y desarrollado la NKA que permite estimar precisamente la likelihood para LSS; permitiéndonos estudiar el origen de la tensión en el parámetro S8.
31
Simon, Paula Cristina da Silva Gonçalves. "Ensino de astronomia para os anos iniciais : uma proposta a partir da observação da lua." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/9062.
Full textAbstract:
Submitted by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T17:44:07Z
No. of bitstreams: 1
DissPCSGS.pdf: 4962933 bytes, checksum: 743628f59c577aa14f19c97309925d35 (MD5)Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T17:44:15Z (GMT) No. of bitstreams: 1 DissPCSGS.pdf: 4962933 bytes, checksum: 743628f59c577aa14f19c97309925d35 (MD5)
Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-23T17:44:21Z (GMT) No. of bitstreams: 1 DissPCSGS.pdf: 4962933 bytes, checksum: 743628f59c577aa14f19c97309925d35 (MD5)
Made available in DSpace on 2017-08-23T17:44:27Z (GMT). No. of bitstreams: 1 DissPCSGS.pdf: 4962933 bytes, checksum: 743628f59c577aa14f19c97309925d35 (MD5) Previous issue date: 2016-12-14
Não recebi financiamento
This research presents results of an investigation of educational pedagogy done with a group of second grade students from an Elementary School. The investigation involved observations of the Moon and educational activities used to teach about Moon phases. An overview of the academic literature on the teaching of the theme of the Moon and its phases was conducted, with a bibliographical review of theses and dissertations, journal articles, papers presented at selected conferences, and some international papers on this topic. From the literature review, it was found that there are few studies that actually address of how observation of the Moon in the sky can be used to effectively teach Moon phases to elementary school students. In this study, students observed and recorded the appearance of the Moon and its place in the sky through drawings. The drawings included the position of the Moon relative to the horizon and used observations made at the school and at their homes during part of a lunar month. Using these initial Moon observations and the student drawings, there were discussions in the classroom designed to consolidate student knowledge. In this research, the data were obtained through interviews, class records, and student observations notebooks. A control group was not used. The researcher was also the teacher of the class where the research was developed. The student observations made it possible for the students to perceive the Moon's apparent motion, as well as its change of appearance over several nights. Through classroom discussions centered on the observations, it was clear that the observations helped develop student concept knowledge of Moon phases that would be difficult to develop from classroom experiences that did not include observations. This experiential connection from the observation of the Moon fostered a relationship with the knowledge implied to the reality of nature. For the initial years, in the Astronomy teaching, this is an important link that can promote the learning of such contents, from the senses of the child and the teacher intervention in a flexible and open way.
Esta pesquisa apresenta resultados de uma investigação desenvolvida com uma turma de alunos do segundo ano do Ensino Fundamental envolvendo a observação da Lua. Inicialmente, com o objetivo de apresentar um panorama das pesquisas sobre o tema Lua e suas fases, foi feita uma revisão bibliográfica a partir de teses e dissertações, artigos de periódicos, trabalhos apresentados em eventos selecionados e alguns trabalhos internacionais. Como resultado, verificou-se que poucos são os trabalhos que utilizam a observação da Lua no céu como parte da metodologia para o ensino e a aprendizagem do tema. Como objetivo de pesquisa, foi proposta e estudada uma metodologia na qual os alunos observaram e registraram a Lua por meio de desenhos, incluindo o horizonte, na escola e em suas casas, ao longo de parte de uma lunação. Priorizando a observação do céu, a partir dos desenhos, houve discussões em sala que foram conduzidas objetivando a sistematização do conhecimento. Com uma pesquisa experimental, sem grupo de controle, os dados foram obtidos por meio de entrevistas, registros de aulas e cadernos de observações dos alunos. A pesquisadora também foi a professora da turma onde a pesquisa foi desenvolvida. A observação do céu possibilitou a percepção pelos alunos do movimento aparente da Lua, bem como sua mudança de aspecto ao longo de várias noites. Por meio das discussões em sala de aula, com o uso dos registros, foi evidenciado que o conhecimento da observação desenvolve um saber a partir da vivência que transcende os limites dados ao conteúdo em sala de aula, possibilitando discussões pouco valorizadas no ensino da Lua e suas fases. Essa conexão experiencial a partir da observação da Lua fomenta uma relação com o conhecimento implicado à realidade da natureza. Para os anos iniciais, no ensino de Astronomia, esta é uma vinculação importante que pode promover a aprendizagem de tais conteúdos, a partir dos sentidos da criança e da intervenção docente de modo flexível e aberto.
32
Bretones, Paulo Sergio. "A astronomia na formação continuada de professores e o papel da racionalidade pratica para o tema da observação do ceu." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/287062.
Full textAbstract:
Orientador: Mauricio CompianiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociencias
Made available in DSpace on 2018-08-07T04:54:40Z (GMT). No. of bitstreams: 1 Bretones_PauloSergio_D.pdf: 3534457 bytes, checksum: ebaa76eeee724fe3a3d1e6dc753b9edf (MD5) Previous issue date: 2006
Resumo: Este trabalho analisa o avanço propiciado por um projeto de fonnação continuada para professores do ensino fundamental com o tema observação do céu em Astronomia, levando-se em conta as especificidades do conhecimento, o referencial do professor reflexivo e as práticas de tutoria. Para isto, foi realizado um curso de Astronomia para professores de Ciências e Geografia de 5' a 8' séries, com 46 horas, promovido em 2002 pelo Instituto Superior de Ciências Aplicadas (ISCA) em Limeira. Após o curso foi estabelecido um grupo de estudos e realizadas cinco reuniões.Os dados foram obtidos por meio de avaliações, entrevistas, relatos dos participantes e registros das aulas e reuniões. São apresentados movimentos de sugestões de atividades extrac1asse, ações pessoais dos participantes sem seus alunos, relatos de ações extrac1asse e desenvolvimento de conteúdos astronômicos em aula, ações na prática pedagógica e reflexões dos participantes junto ao professor/pesquisador na avaliação de tais movimentos.Foram investigadas as mobilizações em ações e concepções dos participantes e o papel da, racional idade prática ao longo do programa.Verificou-se que o tema da observação do céu tem caracteristicas específicas na Astronomia que levam a uma prática escolar também específica em que os conteúdos e procedimentos por serem calcados na observação e sua representação solicitam uma prática escolar baseada na racionalidade prática. Mesmo um curso de fonnação de professores baseado inicialmente na racionalidade técnica, ao dar conta da observação do céu, adentra na racionalidade prática e no desenvolvimento próprio de princípios que norteiam a aquisição e o ensino dos conhecimentos referentes à observação do céu. Também se verificou que, para a observação do céu, o modelo da racionalidade prática no referencial do professor reflexivo e ações de tutoria levam à aquisição de conhecimentos, mudanças de concepções e ações extraclasse. Evidenciaram-se os aspectos da prática como ponto de partida, eixo e sua relação com a teoria. Particularmente ao conteúdo de movimento diário da esfera celeste, estabeleceram-se os princípios de relação da altura do pólo com a latitude geográfica, obliqüidade, continuidade do movimento, circularidade, tridimencionalidade e ciclicidade. Também se evidenciaram os aspectos de criatividade e desenvolvimento do pensamento prático dos participantes, com fatores que levam à caracterização de saberes plurais, que têm temporal idade e mostrando que a aquisição de conhecimento é seletiva, ou seja, situada e hierarquizada
Abstract: This work analyzes the advance spread by a project il! the continuing education training of high school teachers who teach the fundamentaIs of Astronomical sky observation, taking into account specitic knowledge, the reflective teacher &amework and tutoring practice.Base on this, a 46 hour Astronomy course was offered to Science and Geography teachers in the four last years of high school organized in 2002 by the Instituto Superior de Ciências Aplicadas in Limeira, Brazil. Following the course a study group was established and tive meetings were held.The data was obtained through assessments, interviews, and accounts by the teachers and records from the classes and meetings. Examples are: suggestions, personal actions of the teachers without their students, accounts of extracurricular activities and development of astronomical contents in class, actions in the pedagogical practices and reflections of the teachers with the teacher/researcher towards the assessment of such changes are shown.The actions and conceptual changes and the role of the practical rationality were then investigated. It was established that sky observation has specitic features that lead to an equally specific school practice, in which the contents and procedures based on observations and their representation point towards a more practical rationality. Even in a training course for teachers based on technical rationality, the introduction of sky observation deepens the practical rationality and the development of principIes that guide the acquisition and the teaching of knowledge about sky observation.It was also established that for sky observation the model of practical rationality, within the reflective teacher theoretical &amework and tutorial actions, leads to knowledge acquisition, conceptual changes and extracurricular activities.It was clear that the aspects of practice act as starting point, axis, and a relation with the theory. In particularly with regard to the daily motion of celestial sphere content, the principIes of relation of the elevation of the celestial pole to geographic latitude was established, obliquity, continuity of motion, circularity, tri-dimensionality and cyclicity. AIso established were the aspects of creativity and development of practical thinking of the participants, with factors that lead to the characterization of pluraIs knowledge, that have temporality and show that the knowledge acquisition is selective or situated and hierarchical
Doutorado
Doutor em Ensino e História de Ciências da Terra
33
Aleksic, Jelena. "Optimized DarkMatter Searches in Deep Observations of Segue 1 with MAGIC." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/117858.
Full textAbstract:
Existe una impresionante cantidad de evidencia, a todas las escalas, en favor de la existencia de la materia oscura - la componente del Universo invisible, no bariónica, que representa casi el 85% de su masa total. Aunque su existencia se postuló por primera vez hace más de 80 años, la naturaleza de la materia oscura sigue siendo hoy en día un misterio. Encontrar y entender la respuesta a esta pregunta es una de las tareas más importantes y emocionantes de la ciencia moderna.
En el contexto de nuestra visión cosmológica actual del Universo, la materia oscura es considerada como un nuevo tipo de partícula, que interactúa débilmente con la materia ordinaria y la radiación. Además, esta nueva partícula es probablemente fría (no relativista), no bariónica, producida térmicamente en el Universo temprano y estable en escalas cosmológicas. Nuestra búsqueda de la partícula de materia oscura se lleva a cabo en paralelo con tres enfoques diferentes: la detección de la materia oscura producida en colisionadores, la detección directa de materia oscura por su interacciones en los experimentos subterráneos, y la búsqueda indirecta en el espacio de tierra y los observatorios de Partículas del modelo estándar creados en la aniquilación de materia oscura o la decadencia.
Esta última estrategia es el tema de esta tesis. Los resultados presentados aquí son de búsquedas indirectas de la materia oscura en la galaxia esferiodal enana Segue 1, realizadas con los telescopios MAGIC de luz Cherenkov. El objetivo es reconocer los rayos gamma altamente energéticos producidos en la aniquilación o la desintegración de las partículas de materia oscura. Para ello, utilizamos algunas de las características espectrales únicas de los rayos gamma procedentes de dichos procesos. Un método de análisis específico, llamado el método de full likelihood, ha sido desarrollado para optimizar la la sensibilidad del análisis para las señales de materia oscura.
El esquema de la Tesis se podría resumir de la siguiente manera:
• Capítulo 1 presenta el paradigma de la materia oscura: cuáles son las evidencias astrofísicas y cosmológicas que sustentan la existencia de la materia oscura y cómo pueden conciliarse con nuestra actual imagen de la evolución del Universo. El capítulo termina con una revisión de algunos de los candidatos más motivados para partícula de materia oscura, con una discusión detallada sobre aquellos que son de especial interés para este trabajo.
• Capítulo 2 está dedicado a describir las búsquedas de materia oscura. Se inicia con la presentación de las diferentes estrategias que emplean actualmente los diversos experimentos, incluyendo los resultados más destacaddos, para continuar con la descripción más detallada de las búsquedas indirectos. Se presta especial atención a las fotones de alta energía como mensajeros de búsqueda, contestando a las preguntas de qué señal se debe esperar, dónde buscarla y con qué instrumentos.
• Capítulo 3 presenta el instrumento utilizado en este trabajo para las búsquedas de materia oscura - los telescopios MAGIC. El capítulo se divide en dos partes: la primera describe las propiedades técnicas del sistema; la segunda, la caracterización de su cadena de análisis estándar.
• Capítulo 4 presenta la contribución científica original de este trabajo - el desarrollo del método de full likelihood, un método de análisis optimizado para el reconocimiento de las características espectrales que se esperan de los fotones originados por la materia oscura. En primer lugar, se presenta formalmente el método, y a continuación se procede a la caracterización de su comportamiento para un conjunto predefinido de condiciones, y se evalúa su rendimiento para determinadas formas espectrales.
• Capítulo 5 presenta los resultados de este trabajo. En primer lugar, la motivación tras la selección de la galaxia Segue 1 como el candidato óptimo para las búsqueda de materia oscura con MAGIC. A continuación, se resumen los detalles de las observaciones realizadas y de la reducción de datos. Sigue el análisis de datos usando el método de full likelihood. Por último, el capítulo termina con los límites obtenidos en este trabajo para diferentes modelos de aniquilación de la materia oscura.
Se presenta breve resumen de los puntos más relevantes de esta Tesis en las conclusiones.There is an impressive amount of evidence, on all scales, favouring the existence of dark matter - an invisible, non-baryonic component of the Universe that accounts for almost 85% of its total mass density. Although its existence was for the first time postulated more than 80 years ago, the nature of dark matter still remains a mystery. Finding and understanding the answer to this question is one of the most important and exciting tasks of modern science. In the context of our current cosmological view of the Universe, dark matter is considered to be a new type of massive particle, that interacts weakly with ordinary matter and radiation. In addition, this new particle is most likely cold, non-baryonic, produced thermally in the early Universe and stable on cosmological scales. Our search for dark matter particle is carried out in parallel by three different approaches: detection of dark matter produced in colliders, direct detection of dark matter scattering off ordinary matter in underground experiments, and indirect search with space and ground-based observatories for Standard Model particles created in dark matter annihilation or decay. This last strategy is the subject of this Thesis. Results presented here are from indirect searches for dark matter in dwarf spheroidal galaxy Segue 1, carried out with the Imaging Air Cherenkov Telescopes called MAGIC. The objective is to recognize highly energetic photons, produced in annihilation or decay of dark matter particles, by some characteristic spectral features unique for gamma rays of dark matter origin. An dedicated analysis approach, called the full likelihood method, has been developed to optimize the sensitivity of the analysis for such dark matter signatures. The outline of the Thesis could be summarized as follows: • Chapter 1 introduces the dark matter paradigm: what are the astrophysical and cosmological evidence supporting the existence of dark matter, and how can they be reconciled with our current image of the evolution of the Universe. The Chapter ends with review of some of the best motivated candidates for dark matter particle, with detailed discussion about those that are of particular interest for this work. • Chapter 2 is devoted to dark matter searches. It begins with presentation of different strategies currently employed by various experiments and their most worth noting results, to continue with more detailed description of indirect searches. Special attention is devoted to the highly energetic photons as search messengers: what signal should be expected, where to look for it and with which instruments. • Chapter 3 introduces this work's tool for dark matter searches - the MAGIC Telescopes. Chapter is divided into two parts: one, describing the technical properties of the system, and the other, characterizing its standard analysis chain. • Chapter 4 presents the original scientific contribution of this work - the development of the full likelihood approach, an analysis method optimized for recognition of spectral features expected from photons of dark matter origin. First, the method is introduced, then characterized for the pre-defined sets of conditions and its performance evaluated for particular spectrum examples. • Chapter 5 brings the results of this work. First, the motivation behind the Segue 1 galaxy as the optimal dark matter candidate for searches with MAGIC is presented. Then, details of the carried observations and data reduction are summarized. This is followed by the full likelihood analysis of the data. Finally, this Chapter ends with the constraints obtained from this work for different models of dark matter annihilation decay. Brief summary of the most relevant points of this Thesis is presented in Conclusions.
34
Oliveira, Fabiana Andrade de [UNESP]. "Investigando o desenvolvimento de práticas reflexivas de professores em um curso de formação continuada em astronomia voltado à observação do céu." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/145005.
Full textAbstract:
Submitted by FABIANA ANDRADE DE OLIVEIRA null (anafabi.ufms@gmail.com) on 2016-12-02T17:47:28Z
No. of bitstreams: 1
dissertacao_Fabiana final.pdf: 1471587 bytes, checksum: bd3d8d957ce22f22a6e2cb7ee20840b9 (MD5)Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-12-06T11:34:35Z (GMT) No. of bitstreams: 1 oliveira_fa_me_bauru.pdf: 1471587 bytes, checksum: bd3d8d957ce22f22a6e2cb7ee20840b9 (MD5)
Made available in DSpace on 2016-12-06T11:34:35Z (GMT). No. of bitstreams: 1 oliveira_fa_me_bauru.pdf: 1471587 bytes, checksum: bd3d8d957ce22f22a6e2cb7ee20840b9 (MD5) Previous issue date: 2016-03-11
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A presença de dificuldades associadas ao ensino de astronomia nas escolas, a falta de contato de professores com esta Ciência durante a formação inicial e a necessidade de formar indivíduos cientes a respeito do céu noturno, levaram a necessidade de um curso de formação continuada com ênfase na observação do céu. Esta pesquisa envolve o estudo de um curso de formação continuada em astronomia com relação ao desenvolvimento profissional reflexivo de professores. Nesse sentido, buscamos responder à questão principal: Que indícios do desenvolvimento de práticas reflexivas emergem durante um curso de formação continuada em astronomia? Com efeito, os movimentos realizados em prol de um diálogo entre teoria e prática deram-se a partir do trabalho colaborativo entre os professores e pesquisadora, sendo o processo reflexivo sustentado sob três aspectos: uma situação prática desses professores, reflexões em coletivo e apresentação de pesquisas acadêmicas sobre ensino de astronomia. Os dados foram constituídos a partir de um questionário e grupos focais realizados em dois encontros com os professores. Apoiando-se metodologicamente na Análise de Conteúdo, os resultados apontam para indícios da contribuição do curso com relação ao desenvolvimento de práticas reflexivas. Dessa forma, ultimamos que as condições de reflexão em coletivo mostraram-se efetivas ao permitir que situações reais de ensino fossem discutidas e estudadas entre os pares, possibilitando também o envolvimento dos professores nas decisões em relação ao curso. Alguns deles acreditam que as teorias não atendem às suas necessidades formativas, uma vez que estão distantes dos problemas que vivenciam na prática. Em contrapartida, outros professores entendem que há fatores limitantes quanto às condições de estudo e melhorias profissionais. Na visão de alguns professores as atividades práticas desenvolvidas ao longo dos encontros foram relevantes, pois consistem em estratégias e metodologias que viabilizam a abordagem da astronomia no contexto da sala de aula. Os resultados desta pesquisa mostram que os professores apresentam preocupações de ordem prática, relacionadas ao contexto da sala de aula e à aprendizagem dos alunos.
There are some difficulties associated with the teaching of astronomy in schools, the lack of contact of teachers with this Science during initial formation and the need to train individuals aware of the night sky, led to the need for a continuing education course with emphasis on watching the sky. This research involves the study of a continuing astronomy training course in relation to the reflective professional development of teachers. In this sense, we seek to answer the main question: What signs of the development of reflexive practices emerge during a course of continuing formation in astronomy? In fact, the movements carried out in favor of a dialogue between theory and practice were based on collaborative work between teachers and researcher, and the reflexive process was sustained under three aspects: a practical situation of these teachers, reflections in collective and presentation of Academic research on astronomy teaching. The data were constituted from a questionnaire and focus groups conducted in two meetings with the teachers. By supporting methodologically in Content Analysis, the results point to indications of the course's contribution to the development of reflective practices. Thus, we conclude that the conditions of collective reflection have proved to be effective in allowing real teaching situations to be discussed and studied among peers, thus enabling the involvement of teachers in decisions related to the course. Some of them believe that the theories do not meet their training needs, since they are far from the problems they experience in practice. On the other hand, other teachers understand that there are limiting factors regarding the conditions of study and professional improvements. In the view of some teachers, the practical activities developed during the meetings were relevant, since they consist of strategies and methodologies that enable the approach of astronomy in the context of the classroom. The results of this research show that teachers present practical concerns related to the context of the classroom and student learning.
35
Añez, López José Ignacio. "Observational and theoretical perspective of massive star formation." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/671784.
Full textAbstract:
In this thesis, we are aimed to better understand the massive star formation process paying special attention to the role of the magnetic field. To do this, we will carry out a multi-scale analysis with a double approach, theoretical and observational.
a) The role of the magnetic field in the fragmentation process: the case of G14.225-0.506
In this first work, we study the fragmentation of an infrared dark cloud that has a filamentary structure and two hubs. We will pay special attention to the magnetic field present in the environment of the hubs and we will try to relate it to the different levels of fragmentation that these hubs present.
In order to carry out this study, we present the result of the CSO observations at 350 um, towards both hubs, North and South, in the infrared dark cloud G14.225-0.506 (from here G14.2). We also show the analysis of polarization and intensity gradient making use of the method developed by Koch et al. 2012, Koch et al. 2012b.
In the N-hub we find a magnetic field with a uniform distribution along the east-west direction.
However, in the southern hub the B-field shows a bimodal distribution. The intensity-gradient in the N-hub shows a single local minimum. In the S-hub, the intensity gradient reveals two minima reflecting the bimodal distribution of the magnetic field where each component points to each of the minima of the intensity gradient.
Analysis of the maps |delta| and Sigma_B in the N-hub indicates that, in the vicinity of the hub, gravity dominates the magnetic field. We have also estimated the intensity of the magnetic field finding higher values in the N-hub than in the S-hub. This supports the idea that the different levels of fragmentation exhibited by hubs depend on differences in magnetic field.
b) Modeling the accretion disk around the high-mass protostar GGD 27-MM1
In this second project, we descend to accretion disk scales to understand how massive stars form and evolve. In this work we have used ALMA observations at a wavelength of 1.14~mm with very high angular resolution that resolve the disk around the massive star GGD27-MM1.
Motivated by the similarity of this system to those found in low mass, we have modeled the emission of the disk using the models developed by D'Alessio et al. 2006 for low mass stars. The main objective is to investigate whether the assumptions that are valid for disks around low-mass stars could be extrapolated to the case of massive stars.
As a result we have found a very massive disk of about ~5 Msun which represents around 25 % of the stellar mass. This mass is consistent with the calculated dynamic mass. The disk has a radius of ~170 au with a 49º of inclination. We have compared the temperature and density structure obtained with our model with potential functions and show that the GGD~27--MM1 system is a potential template for future similar studies in other high-mass protostars.
Specifically, we have found a flared disk with a maximum scale height of ~13 au and a temperature profile that goes from ~150 K on the outside of the disk to ~ 1400 K on the inner edge of the disk.
Analysis of the Toomre parameter Q evaluated at the midplane temperature of the disk indicates that the disk is stable up to a radius 100 au.
This work shows that D'Alessio's models can be used as a first approximation and also obtain various observational predictions.En esta tesis, pretendemos contribuir a explicar el proceso de formación de estrellas masivas prestando especial atención al papel del campo magnético. Para ello, realizaremos un análisis multiescala con una doble aproximación, teórica y observacional. Por un lado investigaremos el proceso de acrecimiento a través de un disco de acrecimiento entorno a una estrella de alta masa. a) El papel del campo magnético en el proceso de fragmentación: el caso de G14.225-0.506 En este primer trabajo, estudiamos la fragmentación de una nube oscura infrarroja que presenta una estructura filamentaria y dos hubs. Prestaremos especial atención al campo magnético presente en el entorno de los hubs y trataremos de relacionarlo con los distintos niveles de fragmentación que presentan estos hubs. Para poder llevar a cabo este estudio presentamos el resultado de las observaciones del CSO a 350 masas solares, hacia ambos hubs, Norte y Sur, en la nube oscura infrarroja G14.225-0.506 (desde aquí G14.2). También mostramos el análisis de la polarización y gradiente de intensidad haciendo uso del método desarrollado por (Koch et al. 2012, Koch et al. 2012b). b) El modelado del disco de acrecimiento entorno a la protoestrella masiva GGD 27-MM1 En este segundo proyecto, descendemos hasta escalas de discos de acrecimiento para entender como las estrellas masivas se forman y evolucionan. En este trabajo hemos usado observaciones de ALMA a una longitud de onda de 1.14 mm con muy alta resolución angular (aproximadamente 40 mili-segundos de arco) que resuelven el disco entorno a la estrella masiva GGD27-MM1. El disco se dispone perpendicularmente al espectacular chorro de 10 pc de longitud que emana de la fuente, conocido como HH80-81. Motivados por el parecido de este sistema a los que encontramos en baja masa, hemos modelado la emisión del disco haciendo uso de los modelos desarrollados por D'Alessio et al. 2006 para estrellas de baja masa.
36
Cea, del Pozo Elsa de. "Some observational and theoretical aspects of cosmic-ray diffusion." Doctoral thesis, Universitat Autònoma de Barcelona, 2011. http://hdl.handle.net/10803/51003.
Full textAbstract:
La Tesis contiene ciertos estudios relacionados con la difusión de rayos cósmicos. Está dividida en dos partes, una describe los modelos sobre la fenomenología de difusión de rayos cósmicos, y otra presenta las observaciones realizadas usando el experimento MAGIC y simulaciones del futuro Array de Telescopios Cherenkov (CTA, por sus siglas en inglés).
En la primera parte, se introduce la teoría general más aceptada sobre la difusión de rayos cósmicos. Se cree que los remanentes de supernova (SNR) son uno de los escenarios más probables de aceleración de rayos cósmicos, tanto en procesos leptónicos como hadrónicos. El mecanismo de aceleración de partículas en cada SNR se asume que es aceleración por choque difuso (diffusive shock acceleration). Para obtener confirmación observacional de la aceleración de protones y otros núcleos, y distinguirlos de la emisión leptónica, se deben aislar los efectos de los múltiples mensajeros producidos por partículas secundarias. Partiendo de ahí, se desarrolla un modelo sobre los alrededores del SNR IC443 que explica la fenomenología de alta energía: los rayos cósmicos escapan del remanente, los más energéticos alcanzan antes la nube molecular situada delante de la misma y los menos energéticos aún permanecen confinados a los restos del SNR. Los resultados contrastados con las últimas observaciones obtenidas de la fuente explican su aparente desplazamiento cuando se observa a alta y a muy alta energía.
También se presenta un modelo multi-frecuencia y multi-mensajero (fotones de todo el espectro electromagnético y neutrinos) de la emisión difusa de la galaxia con un estallido de formación estelar M82. Las predicciones para rayos gamma se comparan con (y explican satisfactoriamente) las posteriores detecciones en el rango energético comprendido entre los giga- y los tera-electronvoltios de las galaxias M82 y NGC 253, realizadas por el satélite Fermi y los experimentos en tierra H.E.S.S. y VERITAS.
En la segunda parte de la Tesis, se describe la técnica de detección de rayos gamma desde tierra a través de la radiación Cherenkov. Esta técnica es explotada, entre otros, por el experimento MAGIC. Algunas de las observaciones realizadas por la estudiante con este telescopio se presentan como parte de esta Tesis. En primer lugar, se muestran los límites superiores (upper limits) al flujo de rayos gamma obtenidos con MAGIC-I sobre dos fuentes detectadas por el experimento Milagro y que se corresponden con dos fuentes brillantes del satélite Fermi en la región del SNR G65.1+0.6. Se cree que puedan tratarse de dos púlsares que inyectan energía y partículas en la nebulosa pulsada que las rodea. También se presentan resultados preliminares de observaciones en estéreo (con los dos telescopios MAGIC) del SNR IC443. El número de horas obtenido resulta insuficiente para completar el estudio morfológico dependiente de la energía para el que se enfocaba la obtención de estos datos, pero nuevas observaciones están previstas para el futuro.
Finalmente, se introducen por primera vez algunas simulaciones realizadas con el futuro CTA y ciertos estudios espectrales sobre particulares casos científicos. En concreto, dichos estudios se centraron en los objetos ya discutidos en el resto de la Tesis, como el SNR IC443, las galaxias con estallido de formación estelar M82 y NGC 253, y nubes moleculares iluminadas por rayos cósmicos escapados de SNRs cercanos. El observatorio CTA representa el futuro de las observaciones de rayos gamma desde tierra, y prevé que se unan las colaboraciones de todas las instalaciones de telescopios actuales. El rango de energías se verá ampliado, la sensibilidad aumentará un orden de magnitud y la resolución angular se mejorará respecto a los experimentos existentes hoy en día. Esta Tesis representa, pues, sólo el principio de lo que queda por venir.This Thesis deals with certain aspects on cosmic-ray diffusion. It is divided in two parts, one describes phenomenological models of cosmic-ray diffusion, and the other presents observations taken with the MAGIC experiments and simulations of the future Cherenkov Telescope Array (CTA). In the first part, the generally accepted theory for cosmic-ray diffusion is introduced. Supernova remnants (SNRs) are believed to be the more likely scenarios of cosmic-ray acceleration, considering both hadronic and leptonic processes. The mechanism for particle acceleration in each SNR is assumed to be diffusive shock acceleration (DSA). To obtain the observational confirmation of proton and nuclei acceleration, and distinguish it from leptonic emission, the effects of multiple messengers produced by secondary particles must be isolated. Following this, a model for the neighborhood of the SNR IC443 is developed, explaining the high energy phenomenology: cosmic rays escape from the remnant, the most energetic ones reach first the molecular cloud located in front of it and the least energetic ones still remain confined on the shell of the SNR. The results are confronted with the latest observations that are obtained from this source. The apparent displacement between high and very high energy detected sources is explained thanks to this model. Moreover, a multi-frequency and multi-messenger model (i.e., photons from the whole electromagnetic spectrum and neutrinos) for the diffuse emission coming from the starburst galaxy M82 is presented. The gamma-ray predictions are compared to the posterior detections in the energy range between the giga- and the tera-electronvolts of the starburst galaxies M82 and NGC 253, observed by the satellite Fermi and the ground-based experiments H.E.S.S. and VERITAS. The model explains rather satisfactorily these detections at high and very high energy. In the second part of the Thesis, the technique for the gamma-ray detection at ground level through Cherenkov radiation is described. This Cherenkov technique is used in the MAGIC experiment, among others. Some of the observations taken by the student with this telescope facility are presented as part of this Thesis. First, the upper limits to the gamma-ray flux coming from two sources in the region of the SNR G65.1+0.6 when observed with MAGIC-I are shown. These two sources were previously detected by the Milagro experiment and are associated with two bright sources in the Fermi catalog. One of the possible explanations is that these sources are two pulsars powering the pulsar wind nebula that surrounds them. Furthermore, preliminar results of the stereo observations (using the two MAGIC telescopes) of the SNR IC443 are presented. The goal for these observations is performing an energy-dependent morphological study. So far, the obtained number of hours is not enough, although new observations are planned for the near future. Finally, some simulations for the future CTA are presented for the first time, together with several spectral studies regarding interesting scientific cases. In particular, those studies are focused on objects that have been already mentioned in this Thesis, like the SNR IC443 and the starburst galaxies M82 and NGC 253, and also on molecular clouds that are illuminated by cosmic rays which escaped from nearby SNRs. The CTA observatory represents the future of the ground-based gamma-ray observations, and it is likely to include every collaboration from the existing telescope facilities nowadays. The energy range will be widened, the sensitivity will be one order of magnitude improved and the angular resolution will be enhanced respect to the existing experiments up to now. Thus, the present Thesis is just the tip of the iceberg of what is yet to come.
37
Martín, Rodríguez Jonatan. "Theory & observations of the PWN-SNR complex." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/283894.
Full textAbstract:
In this work, we study theoretical and observational issues about pulsars (PSRs), pulsar
wind nebulae (PWNe) and supernova remnants (SNRs). In particular, the spectral modeling
of young PWNe and the X-ray analysis of SNRs with magnetars comparing their characteristics
with those remnants surrounding canonical pulsars.
The spectra of PWNe range from radio to γ-rays. They are the largest class of identified
Galactic in γ-rays increasing the number from 1 to ∼30 during the last years. We have developed
a detailed spectral code which reproduces the electromagnetic spectrum of PWNe in
free expansion (tage .10 kyr). We shed light and try to understand issues on time evolution
of the spectra, the synchrotron self-Compton dominance in the Crab Nebula, the particle
dominance in PWNe detected at TeV energies and how physical parameters constrain the
detectability of PWNe at TeV. We make a systematic study of all Galactic, TeV-detected,
young PWNe which allows to find correlations and trends between parameters. We also
discuss about the spectrum of those PWNe not detected at TeV and if models with low magnetized
nebulae can explain the lack of detection or, on the contrary, high-magnetization
models are more favorable.
Regarding the X-ray analysis of SNRs, we use X-ray spectroscopy in SNRs with magnetars
to discuss about the formation mechanism of such extremely magnetized PSRs. The
alpha-dynamo mechanism proposed in the 1990’s produces an energy release that should
have influence in the energy of the SN explosion. We extend the work done previously done
by Vink & Kuiper (2006) about the energetics of the SN explosion looking for this energy
release and we look for the element ionization and the X-ray luminosity and we compare
our results with other SNRs with an associated central source.
38
Soler, Daniel Rutkowski. "Astronomia no currículo do Estado de São Paulo e nos PCN: um olhar para o tema observação do céu." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/81/81131/tde-25022013-133229/.
Full textAbstract:
A atividade de se observar o Céu é de suma importância para a obtenção de informações sobre a grande maioria dos objetos celestes, particularmente os de fora do Sistema Solar: não existem ainda meios tecnológicos que nos permitam obter tais informações in loco, seja por meio de sondas robóticas, seja por meio de naves tripuladas. Sob este ponto de vista, é então relevante oferecer a crianças e jovens a oportunidade de participarem de atividades didáticas de Observação do Céu, propiciando, assim, o estabelecimento de um primeiro contato sistemático deles com o Céu e, consequente e essencialmente, com todo o Universo que existe fora de nosso planeta. Neste trabalho estamos preocupados, particularmente, com o ensino sobre a Observação do Céu: estamos interessados em tratar sobre propostas didáticas, nas quais se ensine sobre como observar o Céu. Nosso principal objeto de estudo é o atual Currículo do Estado de São Paulo, mais especificamente os chamados Cadernos do Professor, que integram o conjunto de materiais didáticos vinculados a esse Currículo. Nesta dissertação nos propusemos a avaliar as atividades didáticas de Observação do Céu que são propostas junto aos Cadernos do Professor para as disciplinas de Ciências do Ensino Fundamental e Física do Ensino Médio. Essa avaliação foi feita a partir de dois pontos de vista. No primeiro, a análise se deu a respeito dos conteúdos presentes nas atividades, os quais foram comparados, por meio de Mapas Conceituais, com aqueles presentes nos Parâmetros Curriculares Nacionais. O segundo ponto de vista para a avaliação se deu a respeito da estrutura das atividades. Para subsidiar tal análise foi feito um estudo junto a pesquisas da área de Ensino de Astronomia a partir da qual foram elencadas 6 dimensões ligadas à proposição de atividades didáticas de Observação do Céu - \"Objetos e fenômenos observáveis\"; \"Condições de observação, planejamento e preparação\"; \"Público alvo, contexto e interatividade do público\"; \"Objetivos maiores da observação\"; \"Registros das observações\"; e \"Tipos de observação e instrumentos\" -, as quais foram tratadas como parâmetros importantes na construção de propostas dessa natureza, sendo então utilizadas como categorias de análise daquelas presentes nos Cadernos do Currículo do Estado. Os principais resultados mostram que os conteúdos ligados à prática de Observação do Céu, tanto nos PCN quanto nos Cadernos do Currículo do Estado são significativamente semelhantes, inclusive a presença restrita ao Ensino Fundamental. Além disso, as atividades de Observação do Céu dos Cadernos parecem apresentar coerência interna e tendem a contemplar os resultados de pesquisas em Educação em Astronomia.The activity of observing the Sky is very important to obtain information about the vast majority of celestial objects, particularly those from outside our Solar System: there are no technological means nowadays that allow us to obtain such information on-site, whether through robotic probes or by manned spacecraft. Under this view, it is therefore important to offer children and teenagers the opportunity to participate in didactic activities of the Sky Observation, thus allowing them to have a first systematic contact with the Sky, consequently and essentially with the whole Universe that exists outside our planet. In this work we are concerned particularly with the teaching about the Sky Observation: we are interested in dealing with proposals about teaching, in which one teaches \'how to observe the Sky\'. Our main object of study is the current Curriculum of the State of São Paulo, more specifically the Teacher\'s textbooks, which constitute the set of educational materials related to such Curriculum. In this dissertation we propose to evaluate the didactic activities of Sky Observation that are proposed in the Teacher\'s textbooks for the discipline of Science in Elementary School and for Physics in High School. This evaluation was made from two viewpoints. First, the analysis was about the content present in the activities, which were compared with the National Curriculum Parameters by means of Concept Maps. The second point of the evaluation was made regarding the structure of activities. To support this analysis, a study was done with some research of the area of Astronomy Teaching from which we listed 6 dimensions related to the proposition of didactic activities about Sky Observation - \"Objects and observable phenomena\"; \"Conditions of observation, planning and preparation\", \"Audience, context and audience interactivity\", \"Main objectives of observation\"; \"Records of observations\"; and \"Types of observation and instruments\" - which were treated as important parameters in building such proposals, then being used as analytical categories of those present in the textbooks of the Curriculum of the State. The main results show that the contents linked to the practice of Sky Observation, both the PCN and the Curriculum of the State are significantly similar, even the restricted theme of Sky Observation to elementary schools. Moreover, the activities of the Sky Observation in the textbook seem to have internal consistency and tend to contemplate the results of research in Astronomy Education.
39
Domingo, Santamaría Eva. "(gamma)-ray emission from regions of star formation: Theory and observations with the MAGIC Telescope." Doctoral thesis, Universitat Autònoma de Barcelona, 2006. http://hdl.handle.net/10803/3374.
Full textAbstract:
Es el propósito de esta tesis estudiar la posibilidad de que regiones con importante actividad en formación estelar sean fuentes de rayos gamma para los actuales y futuros detectores, ya sean detectores de rayos gamma con base en satélites como telescopios Cherenkov situados en la superficie terrestre.Tras una evaluación fenomenológica positiva de que la emisión de rayos gamma procedente de galaxias con elevada actividad en formación estelar (como las llamadas starburst o las galaxias ultra luminosas en el infrarrojo) esté cerca de la sensibilidad de los actuales detectores de rayos gamma, se han desarrollado y presentado modelos detallados de la emisión difusa multifrecuencia procedente de los dos mejores candidatos, NGC 253 y Arp 220. Se predice que ambas galaxias serán detectables para GLAST, el próximo satélite de rayos gamma con una sensibilidad sin precedentes, y por HESS y MAGIC, los actuales telescopios Cherenkov con mayor sensibilidad, en caso de que éstos dediquen suficiente tiempo de observación a estas galaxias.
En la parte teórica de la tesis se describe también un modelo que propone la emisión de importantes flujos de rayos gamma en regiones de formación estelar dentro de nuestra Galaxia, como serían las asociaciones de estrellas jóvenes del tipo OB. El modelo considera la emisión de rayos gamma a energías cercanas a los TeV mediante interacciones hadrónicas en el sí de vientos estelares de algunas de las estrellas de la asociación, prediciendo a la vez que la emisión a bajas energías está sustancialmente suprimida debido al efecto de modulación que la población de rayos cósmicos primarios sufre al penetrar en el viento estelar. Se discuten brevemente los mejores candidatos entre las asociaciones OB galácticas conocidas.
Finalmente, la tesis recoge un primer análisis de los datos tomados por el Telescopio MAGIC durante la observación de dos regiones de formación estelar. Por una parte, la galaxia ultra luminosa en el infrarrojo más cercana, Arp 220. Por otra parte, TeV J2032+4130, que aún hoy en día sigue siendo una fuente no identificada, y cuyo origen se ha relacionado con la poderosa asociación estelar Cygnus OB2 en repetidas ocasiones. Ninguna de las observaciones ha implicado detección, en consecuencia, se han impuesto límites superiores al flujo de rayos gamma procedente de las fuentes observadas. Sin embargo, a pesar de las pocas horas de observación incluidas en el presente análisis, los límites superiores impuestos por el Telescopio MAGIC para la fuente TeV J2032+4130 están prácticamente al nivel del flujo que el experimento HEGRA detectó para dicha fuente, de manera que un análisis extendido al conjunto completo de datos disponibles, así como futuras observaciones de más larga exposición con el Telescopio MAGIC, podrían proveer resultados interesantes.
Was the aim of this thesis to study the possibility that regions with important activity in star formation may appear as sources of gamma-rays for the current and near future gamma-ray detectors, both ground and space-satellite based.
After a phenomenological positive evaluation of the fact that the gamma-ray emission from galaxies prone of star formation processes (as starburst or ultra luminous infrared galaxies) may be close to the flux sensitivities of the current gamma-ray telescopes, detailed models of the multiwavelength diffuse emission from the two best candidates, NGC 253 and Arp 220, have been presented. It is predicted that they will be detectable by GLAST, the next largest gamma-ray satellite, and by HESS and MAGIC, the current more sensitive Cherenkov Telescopes, in case enough observation time is devoted.
On the other hand, within this thesis it is described a model which proposes the emission of important fluxes of gamma-rays from regions of star formation within our Galaxy, as the stellar association of young OB stars. The model considers the emission of gamma-rays close to TeV energies by hadronic interactions within the stellar winds of some of the stars of the association, predicting at the same time that the emission at lower energies is substantially suppressed due to the modulation effects that the incoming population of primary cosmic rays suffers when penetrating the winds. The best candidates among the galactic OB associations are briefly discussed.
Finally, a first analysis of the data taken by the MAGIC Telescope when observing two of these regions of star formation is described. On one hand, the closest ultra luminous infrared galaxy, Arp 220. On the other, TeV J2032+4130, which is still an unidentified source whose origin has been several times related to the powerful stellar OB association Cygnus OB2. Any of both observations has implied detection, and upper limits to the gamma-ray flux have been imposed. However, although the few hours of observation included in the present analysis, the MAGIC upper limits for TeV J2032+4130 are nearly at the level of the flux detected by the HEGRA experiment, so an analysis extended to the complete set of data available as well as deeper observations of this source with the MAGIC Telescope can provide promising results.
40
Marcote, Martin Benito. "Non-thermal emission from high-energy binaries through interferometric radio observations." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/336664.
Full textAbstract:
High-mass binary systems involve extreme environments that produce non-thermal emission from radio to gamma rays. Only three types of these systems are known to emit persistent gamma-ray emission: colliding-wind binaries, high-mass X-ray binaries and gamma-ray binaries. This thesis is focused on the radio emission of high-mass binary systems through interferometric observations, and we have explored several of these sources with low- and high-frequency radio observations, and very high-resolution VLBI ones.
We have studied the gamma-ray binary LS 5039 at low and high frequencies, and we have determined its spectra and light-curves in the frequency range of 0.15—15 GHz by analyzing radio observations from the VLA, GMRT and WSRT. We have observed that its spectrum is persistent along the time on day, month and year timescales, exhibiting a turnover at 0.5 GHz. The obtained quasi-simultaneous spectra reveal subtle differences between them. Synchrotron self-absorption can explain the observed spectra, but the Razin effect is necessary at some epochs. This is the first time that this effect is reported in a gamma-ray binary. With all these data and a simple model, we have estimated the physical properties of the radio emitting region, providing an estimation of its size, the magnetic field, the electron density, and the mass-loss rate of the companion star.
We have also explored the low-frequency emission of the gamma-ray binary LS I +61 303 through GMRT and LOFAR observations. We have detected for the first time a gamma-ray binary at a frequency as low as 150 MHz. We have also determined the light-curves of the source at 150, 235 and 610 MHz. These light-curves are modulated with the orbital and superorbital period, with a quasi-sinusoidal modulation along the orbital phase. The shifts observed between the orbital phases at which the maximum emission takes place at different frequencies have been modeled with a simple model, suggesting an expanding emitting region, with an expansion velocity close to the stellar wind one.
The gamma-ray binary HESS J0632+057 has been explored with a very high-resolution EVN observation to unveil the evolution of its radio emission along the orbit. However, the source was not detected, setting an upper-limit which is one order of magnitude below the radio emission detected in previous observations.
We have discovered a new colliding wind binary (HD 93129A) through a multiwavelength campaign with optical and LBA radio data. We have resolved the radio emission from the wind collision region, observing the expected bow-shaped structure. This source is one of the earliest, hottest, and most massive binary systems discovered up to now. We provide a rough estimation of the wind momentum rates ratio based on the observed structure. We have also observed an increase of the radio emission during the last years, as the system approaches to the periastron passage, which is estimated to take place in ~2024.
Finally, we performed radio observations on two new sources that were hypothesized to be gamma-ray binaries. On one hand, the star TYC 4051-1277-1 was initially proposed to be associated with a non-thermal radio source, but he have concluded that the radio emission is originated by a quasar. On the other hand, MWC 656 has been discovered to be the first Be/BH binary system. However, its radio emission remains undetected.
Based on these results, we have improved the knowledge of several high-energy binary systems through their radio emission, conducting for the first time detailed low-frequency estudies on these types of sources.Las binarias de alta energía son sistemas que producen emisión de rayos X y/o rayos gamma, debido a la presencia de un entorno suficientemente energético como para acelerar partículas hasta velocidades relativistas. Sólo tres tipos de binarias han sido detectadas en rayos gamma de forma persistente: binarias con colisión de vientos, binarias de rayos X de alta masa o binarias de rayos gamma. Todas ellas involucran una estrella masiva (con una masa superior a 8 veces la masa solar) y a otra estrella masiva o a un objeto compacto. Esta tesis está centrada en el estudio de la emisión radio de estos sistemas a través de observaciones con radio interferómetros. Se han estudiado dos binarias de rayos gamma a bajas frecuencias (LS 5039 y LS I +61 303), obteniendo sus curvas de luz y espectros. Éstos nos han permitido determinar propiedades físicas de la región emisora, como el campo magnético, la tasa de pérdida de masa, o la velocidad de expansión de dicha región. También hemos revelado la presencia del efecto Razin en la parte absorbida del espectro de LS 5039, siendo la primera vez que se detecta en una binaria de rayo gamma. Además, se ha detectado por primera vez una binaria de rayos gamma, LS I +61 303, a una frecuencia tan baja como 150 MHz. También se ha estudiado la binaria de rayos gamma HESS J0632+057 con observaciones radio de muy alta resolución, aunque la misma no ha sido detectada. Se ha descubierto una nueva binaria con colisión de vientos, HD 93129A, a través de observaciones radio de muy alta resolución y observaciones ópticas. Por último, se han llevado a cabo observaciones radio de dos fuentes que eran candidatas a ser binarias de rayos gamma.
41
Moldón, Vara Francisco Javier. "Structure and nature of gamma-ray binaries by means of VLBI observations." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/96996.
Full textAbstract:
Gamma-ray binaries are extreme systems that produce non-thermal emission from radio to very-high-energy (above TeV) gamma rays, with the energy output in the spectral energy distribution (SED) dominated by the MeV–GeV photons. Their broadband emission is usually modulated by the orbital cycle of the system, which suggests that the physical conditions are also periodic and reproducible. The diversity of systems, together with the reproducibility of the conditions within each system, makes gamma-ray binaries excellent physical laboratories in which high energy particle acceleration, diffusion, absorption, and radiation mechanisms can be explored. Nevertheless, the number of known gamma-ray binaries is still very limited, and only a six binary systems have been classified as gamma-ray binaries. These systems produce outflows of relativistic particles emitting synchrotron radio emission that extend up to several astronomical units, which correspond to projected angular scales of a few milliarcseconds (mas) at typical distances of 2-3 kpc. Very Long Baseline Interferometry (VLBI) provide mas resolution and therefore can be used to directly see this radio outflow. In this thesis we present VLBI observations of five of the six gamma-ray binaries known. We have revealed for the first time the radio structure of two gamma-ray binaries, and found periodic changes in the structure of other two. Based on these results, we have established the basic properties and behaviour of the radio emission of gamma-ray binaries on AU scales, and we have contributed to find characteristics that are common to all of them.En los últimos años se ha producido una mejora significativa de los instrumentos que permiten observar fenómenos astrofísicos en rayos gamma de alta y muy alta energía. Gracias a estos avances, se ha podido detectar emisión de rayos gamma en sistemas binarios. Tan sólo seis sistemas binarios han sido clasificados como estrellas binarias de rayos gamma (tres de ellos aún son candidatos). Estos sistemas producen chorros de material relativista que a su vez producen grandes cantidades de energía en todo el espectro electromagnético, desde ondas radio hasta emisión de rayos gamma hasta energías del teraelectronvolt (TeV). Estos chorros se desplazan a alta velocidad produciendo estructuras en escalas de varias unidades astronómicas (UA). Estas estructuras pueden ser observadas directamente mediante técnicas de interferometría radio de muy larga línea de base (VLBI). En esta tesis nos centramos en el estudio de las propiedades morfológicas y astrométricas de binarias de rayos gamma observadas mediante VLBI. De las seis binarias conocidas, se han observado cinco de ellas. Los resultados principales son los siguientes. Se ha detectado estructura extendida en escalas de 120 UA en el sistema binario PSR B1259-63. Esta ha sido la primera evidencia observacional de que púlsares jóvenes no acretantes interaccionando con estrellas jóvenes pueden producir emisión radio extendida. Se ha descubierto que la emisión del sistema LS 5039 muestra cambios periódicos en su morfología, que son estables en escalas de varios años. También se ha determinado el movimiento propio de este sistema y se ha obtenido su trayectoria galáctica en el pasado. Se ha confirmado que el sistema LS I +61 303 muestra variabilidad orbital periódica, aunque presenta cambios significativos en ciertas fases orbitales. Se ha encontrado un desplazamiento del pico de la emisión a varias frecuencias, así como un cambio en sus posiciones relativas. Se ha descubierto emisión extendida procedente de la fuente de rayos gamma HESS J0632+057, y se ha confirmado inequívocamente su asociación con el sistema binario MWC 148. Por último, no se ha encontrado contrapartida radio a la fuente de rayos gamma AGL 2241+4454, cuya contrapartida óptica ha sido propuesta en el sistema MWC 656. Estos resultados permiten sentar las bases de la estructura en escalas de varias UA de los sistemas binarios de rayos gamma, así como su comportamiento en función de la fase orbital. Las características comunes halladas en estos sistemas ha permitido encontrar enlaces observacionales entre estos sistemas, dando consistencia a este particular grupo de estrellas que presentan emisión en rayos gamma.
42
Molina, Lumbreras Edgar. "Modeling and observations of relativistic outflows in high-energy binary systems." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/672686.
Full textAbstract:
Some binary systems consisting of a compact object, which can be either a neutron star or a black hole, and typically a non-degenerate companion star, have been shown to emit broadband radiation from radio up to gamma-ray frequencies. These systems are normally classified as X-ray or gamma-ray binaries, depending on the frequency at which their emission has its maximum. Unlike with stars, a big part of the observed emission cannot be explained by thermal radiation, and therefore non-thermal radiative processes need to be invoked. The interactions between the star and the compact object may result in the launching of outflows of plasma originating around the compact object position. These outflows can attain speeds close to the speed of light, and be an efficient site for acceleration of charged particles up to relativistic energies. A part of the non-thermal emission observed from X-ray and gamma-ray binaries comes precisely from the non-thermal radiative cooling of these accelerated particles. Additionally, when the companion star is very massive, it produces a strong stellar wind that interacts with the aforementioned relativistic outflows, modifying both their dynamical and radiative evolution.
The main theoretical objective of this thesis is the study the interactions between the outflows of X-ray and gamma- ray binary systems and the stellar wind of a massive companion star. For this purpose, we developed versatile semi- analytical models that give a complete view of these interactions for different kinds of systems. The results of the theoretical modeling include broadband spectral energy distributions and light curves that are directly comparable with the observational data. Radio sky maps are also obtained for the large-scale emission of the outflows. The latter allows to directly visualize the dynamical effect of the stellar wind in the outflow trajectory, which acquires a helical or spiral-like pattern. This modified trajectory gives rise to asymmetries in the light curves at different energy ranges, as well as changes in the spectral energy distributions mostly due to variations of angle-dependent processes influencing the outflow emission.
From the observational point of view, this thesis focuses on the analysis of the potential very high-energy gamma-ray emission above 100 GeV of the X-ray binary MAXI J1820+070, as seen by the MAGIC telescopes. The analysis is done through a custom software developed by MAGIC, which allows to reconstruct the arrival direction and energy of a gamma ray from the Cherenkov light emitted by the electromagnetic cascade that the gamma ray generates when it enters the atmosphere of the Earth. The observational results consist on a multiwavelength study of MAXI J1820+070 in the form of light curves and spectral energy distributions that use data from a number of telescopes at radio, optical, X-ray and gamma-ray frequencies. The source is not detected in gamma-rays above 100 MeV, and only flux upper limits can be given for those energies. Nevertheless, the obtained upper limits, together with the observed fluxes at other frequencies, are enough to constrain significantly the properties of a potential gamma-ray emitter in MAXI J1820+070.
In conclusion, this thesis deepens in our understanding of the interactions between the stellar wind and the outflows of high-energy binary systems. It shows that these interactions must be taken into account in order to properly characterize the subset of those binary systems hosting a massive companion star, in which a powerful stellar wind is present. In this thesis, it is also shown that observations in high-energy and very high-energy gamma rays of X-ray and gamma-ray binary systems allow to set meaningful limits to the outflow properties, even when the sources are not detected and only upper limits in the flux are obtained.A la nostra Galàxia, existeixen sistemes binaris formats per un objecte compacte i una estrella companya típicament no degenerada que emeten a freqüències des de ràdio fins a raigs gamma. Les interaccions entre l'estrella i l'objecte compacte poden resultar en el llançament d'outflows de plasma originats al voltant de l'objecte compacte, els quals poden adquirir velocitats properes a la de la llum. Quan l'estrella companya és molt massiva, aquesta genera un fort vent estel·lar que interacciona amb els outflows i els afecta tant dinàmicament com radiativa. El principal objectiu d'aquesta tesi des del punt de vista teòric és l'estudi de les interaccions entre els outflows de sistemes binaris i el vent estel·lar d'una companya massiva. Per això, hem desenvolupat una sèrie de models semi- analítics que donen una visió completa d'aquestes interaccions en diferents tipus d'escenaris. Els resultats de la modelització teòrica inclouen prediccions per a les distribucions espectrals d'energia i corbes de llum, així com mapes ràdio per a l'emissió a gran escala dels outflows. En relació a la part observacional, aquesta tesi es focalitza en l'anàlisi de l'emissió potencial de raigs gamma de molt alta energia de la binària MAXI J1820+070, observada amb els telescopis MAGIC. Els resultats observacionals consisteixen en un estudi multifreqüència de la font de ràdia a raigs gamma. Tot i que la font no es detecta per sobre dels 100 MeV, els resultats obtinguts permeten limitar les propietats d'un emissor potencial de raigs gamma a MAXI J1820+070. En conclusió, aquesta tesi profunditza en el coneixement de les interaccions entre el vent estel·lar i els outflows de sistemes binaris d'altes energies. També es conclou que les observacions en raigs gamma de sistemes binaris permeten limitar de manera important les propietats dels outflows, fins i tot quan les fonts no son detectades.
43
Tescaro, Diego. "TeV γ-ray observation of nearby Active Galactic Nuclei with the MAGIC telescope: exploring the high energy region of the multiwavelength picture." Doctoral thesis, Universitat Autònoma de Barcelona, 2010. http://hdl.handle.net/10803/3428.
Full textAbstract:
Los primeros tres capítulos de la tesis proporcionan una introducción a los temas defísica discutidos en la tesis. La tesis empieza con las nociones básicas sobre rayos cósmicos (capítulo 1),describiendo los resultados de la joven rama de investigación de astrofísica conocidacon el nombre de "Gamma-ray Astronomy" (capitulo 2), y finalmente enfocando ladiscusión en los objetos astrofísicos sobre que la tesis se centra: los núcleos activos degalaxias (capitulo 3). La tesis sigue con tres capítulos que discuten las técnicas experimentales para elestudio de los rayos gamma.La técnicas de detección de rayos gamma, y los distintos tipos de detectores, sonanalizados primero (capitulo 4), prestando una atención especial a la explicación de latécnica de detección conocida como "IACT". Los telescopios MAGIC (capitulo 5) y susubsecuente cadena de análisis de datos (capitulo 6) son el tema de los siguientes capítulos, siendo los datos experimentales de la tesis tomados con precisamente estedetector (en el marco de trabajo de la colaboración MAGIC).
Los dos capítulos siguientes relatan los resultados astrofísicos obtenidos durante la miinvestigación doctoral.Las medidas del flujo de rayos gammas en la banda "VHE" (muy alta energía) desdetres famosos objetos astrofísicos (extra-galácticos), Markarian 421 y Markarian 501, enel marco de las mas completas campañas multifrecuencias realizadas en esto objetos (capitulo 7), y Messier 87, durante una fase muy activa en la banda de energía gamma(capitulo 8).
Finalmente dos apéndices describen las dos mas relevantes tareas técnicas en queestuve involucrado durante mi doctorado. La primera es el desarrollo de una nueva técnica de análisis por los datos de MAGIC,técnica que usa el tiempo de llegada de las señales ademas de su intensidad (apéndiceA). La segunda es el desarrollo del software de adquisición de datos para el telescopioMAGIC-II (apéndice B), el segundo telescopio del sistema de detección conocido ahoracomo: 'MAGIC Florian Goebel Telescopes'.
The first three chapters of this thesis provide an introduction to the relevant physics topics discussed, starting from the basic notions and open questions about the Cosmic Rays (chapter 1), going through the achievements of the young branch of Astrophysics known as gamma-ray Astronomy (chapter 2), and focusing finally on the astrophysicalobjects which are the subject of this thesis: the Active Galactic Nuclei (chapter 3).
We propose then three chapters that discuss the experimental approach to the subject.The gamma-ray detection techniques and the type of detectors are first discussed(chapter 4), paying special attention to the explanation of the IACT technique.The MAGIC telescope(-s) (chapter 5) and its data analysis procedure (chapter 6) arethen discussed in detail, since the astrophysical measurements shown on this thesis areobtained in this framework.
The next two chapters report on the physics results obtained in the course of my research. The measurement of the VHE gamma-ray flux of three famous extragalactic sources,namely Markarian 421 and Markarian 501, in the context of the up to date mostcomplete multiwavelength campaigns ever organized on this type of objects (chapter 7),and Messier 87 during an important flaring activity (chapter 8).
Finally, two appendices describe the most relevant technical developments to which Iwas committed during my PhD.The first is the development of a novel method for the analysis of the MAGIC telescopedata which makes use of the time information in the Cherenkov images (appendix A).The second is the development of the data acquisition software for MAGIC-II (appendix B), the second telescope of the 'MAGIC Florian Goebel Telescopes' array.
44
Costa, Gleice Kelen Dornelles. "A observação do céu nos livros didáticos de ciências aprovados no PNLD/2017." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/81/81131/tde-23112018-142104/.
Full textAbstract:
A atividade de observação do céu remonta à antiguidade e sua presença na educação básica é defendida por distintos pesquisadores. O caráter observacional pode ser uma estratégia didática para que o aluno amplie a percepção do seu entorno astronômico, sendo capaz de reconhecer fenômenos que fazem parte de seu cotidiano, com ou sem o uso de instrumentos. No entanto, as atividades de observação direta do céu requerem tempos (duração e horários das atividades) e espaços (a céu aberto, fora da sala de aula) que fogem do sistema tradicional escolar, além da necessidade de condições atmosféricas para tal. Esta pesquisa visa compreender a natureza das atividades de observação do céu no Ensino Fundamental II, na disciplina de Ciências, por meio da análise de livros didáticos. Este material didático constituiu-se como um elemento de grande importância dentro do contexto escolar, influenciando o trabalho do professor e acompanhando os alunos em suas atividades, tanto na escola como em casa. Foram analisadas nove coleções de livros didáticos de ciências distribuídos nacionalmente através do Programa Nacional do Livro Didático/2017. A análise foi subsidiada pela elaboração de um conjunto de elementos considerados fundamentais para a construção de uma atividade de observação do céu na escola, presentes nos trabalhos de pesquisadores da área de educação em Astronomia. Esses elementos estruturam o conjunto de atividades que envolvem a observação em seus distintos momentos: antes, durante e após a atividade de observação do céu. Desta forma, foram construídas oito categorias que subsidiaram a análise: Material, Pré-observação, Estratégias para observar e acompanhar astros ou fenômenos, Natureza da observação, Pós-observação, Espaço, Subsídios e Complementos. Na análise, percebeu-se que tópicos de Astronomia estão concentrados nos livros de sexto ano, e que ocupam uma parte considerável do material didático desta série, considerando que estão incluídos conteúdos de outras áreas do conhecimento como Biologia, Física, Geociências, Química. Tópicos de Astronomia desaparecem no sétimo e oitavo anos, retornando no nono ano, em geral, com outras características dentro de Gravitação. As propostas didáticas de observação aparecem quase que exclusivamente no sexto ano e são centradas em curtos períodos de tempo, dificultando a percepção de fenômenos cíclicos promovendo observações contemplativas. Além disso, as atividades geralmente são propostas para serem realizadas fora do espaço escolar, dificultando a participação in loco do professor, necessitando para tal um maior detalhamento da proposta e uma grande autonomia discente. Ainda que as atividades de observação estejam presentes nos LD elas ainda estão distantes das propostas feitas pelos pesquisadores da área que sugerem observações sistemáticas para melhor compreensão, tornando-as experiências próprias, em que a aprendizagem ocorre no tempo do fenômeno e também próprio de cada aluno.Observation of the cosmos dates back to antiquity, and its perpetual presence in basic education is defended by researchers. The observational character can be used as a didactic strategy for the student to enhance the perception of their astronomical environment, being able to recognize phenomena that are part of their daily life, either with or without the use of instruments. However, direct sky observation activities require time (times and schedules of events) and locations (outdoors, outside the classroom) that contrast from the traditional school system, in addition to required atmosphere conditions. This research intends to analyze and understand the nature of the activities when observing the sky while in Elementary School, in the discipline of Sciences for the final years, through textbook study. This material constitutes an element of significant importance within the school context, influencing the work of the teacher and student activity, both at school and at home. Nine collections of science textbooks, distributed nationally through the National Textbook Program / 2017, were analyzed. The analysis was subsidized by the construction of a set of elements considered fundamental for the implementation of an activity of observation of the sky in the school, present in the works of researchers in the area of education in Astronomy. These elements make up the structure of the set of observational activities that range in time from moments before, during and after the sky observation activity. In this way, eight categories were constructed and subsidized the analysis: Material, Pre-observation, Strategies to observe and follow stars or phenomena, Nature of observation, Post-observation, Space, Subsidies and Complements. In the analysis, it was noticed that topics of Astronomy are concentrated in the books of sixth year, and that they occupy a considerable bulk of it, while noting that contents of other areas of education include Biology, Physics, Geosciences, Chemistry. Astronomy topics disappear in the seventh and eighth years and return in the ninth year, usually within Gravitation. The presence of observation are also implemented almost exclusively in the sixth year, which are focused on short periods of time, thereby making it difficult to perceive cyclical phenomena promoting contemplative observations. In addition, these exercises are usually intended to be carried out outside of the school grounds, making it difficult for the teacher to participate, and requiring greater student autonomy. Although the activities of observation are present in the LD, they are still far from the proposals made by the researchers of the area that suggest systematic observations for a better understanding, becoming the own experiences, in which the learning occurs in the time of the phenomenon and also own of each student
45
Carvalho, Tassiana Fernanda Genzini de. "Da divulgação ao ensino: um olhar para o céu." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/81/81131/tde-06102016-113657/.
Full textAbstract:
A psicologia histórico-cultural surgiu no início do século XX, na União Soviética, baseada principalmente nos pressupostos marxistas sobre a constituição do gênero humano. A principal contribuição que trouxe mostra que a relação do homem com o mundo não é uma relação direta da sua observação desinteressada, não é uma situação simples de estímulo-resposta, mas é mediada pela atividade num contexto social. O conceito de atividade não é o mesmo do senso comum e está inserido dentro da Teoria da Atividade, desenvolvida a partir dos trabalhos de Vigotski, por Leontiev e outros autores. A atividade dentro dessa teoria é sempre motivada por uma necessidade humana, construída socialmente, e acontece por meio de ações, ligadas a objetivos definidos, e por operações, ligadas às condições concretas de realização. Estudamos neste trabalho a evolução da relação do ser humano com o céu, e como a atividade \"observar o céu\" foi transformando a natureza e a própria essência do homem, como uma perspectiva singular. Com isso pudemos compreender de que forma os documentos curriculares, as pesquisas em ensino de astronomia e os profissionais da educação básica concretizam atividades de ensino para a \"observação do céu\", como perspectivas particulares de manifestação da história dessa ação, dentro do ensino da astronomia. Percebemos que esse tema está em ascensão nas propostas educativas e que tanto os currículos quanto os pesquisadores e professores reconhecem a importância da observação do céu para a constituição dos seres humanos; no entanto, apesar de constar das propostas curriculares e do conteúdo das pesquisas, a \"observação do céu\" ainda não é uma realidade nas práticas escolares, provavelmente por encontrar condições concretas pouco favoráveis, principalmente uma formação inadequada dos professores e a falta de materiais e infraestrutura necessárias para o trabalho na sala de aula. Fizemos uma análise, relacionando o movimento histórico lógico dos conceitos sobre o céu e o \"objeto de ensino céu\", procurando a essência desse conceito ao longo do seu desenvolvimento. Sugerimos uma proposta de situação desencadeadora de ensino, baseada nos resultados empíricos de nossa pesquisa sobre o conhecimento dos professores e a disponibilidade para ensinar astronomia, como é proposta pelos currículos. Essa proposta permitiria aos educandos tanto a apropriação da cultura humana desenvolvida ao longo da história, quanto desenvolver suas potencialidades como ser humano, como perspectiva universal, a qual favorece a construção de um pensamento teórico, num movimento de ascensão do abstrato ao concreto, definido na teoria que fundamenta este trabalho.Cultural-historical psicology appeared early in the 20th century, in the Soviet Union, based mainly on marxist principles relative to the human gender. Its main contribution shows that the relation between man and the world is not a direct consequence of uninterested observation, it is not a simple stimulus-reaction situation, but it is mediated by activity within a social context. The activity concept does not have the common sense meaning but it is inserted in the Activity Theory that was based on the work of Vigotski, Leontiev and other authors. According to this theory, activity is always motivated by a human necessity that is built up socially by means of actions connected to well defined objectives and by operations connected to concrete realization conditions. In this work we studied the evolution of human beings in relation to the sky and how the \"sky observation\" activity has been transforming nature and the very essence of man, as a singular perspective. Under this point of view we can explain curricular documents, research on astronomy teaching and teaching activities for \"sky observation\" elaborated by education professionals, as a particular perspective of the history of this action in astronomy teaching. We noticed that this subject is becoming more important in educational proposals and that curricula as well as investigators and teachers admit the importance of sky observation for building up of human beings; however in spite of appearing in curricular proposals and in the \"sky observation\" research content it is still not a reality in school practice, probably because of rather unfavorable conditions ,such as teachers inadequate formation and the lack of materials and infrastructure that are essential for school room work. We made an analysis relating logical historical progress about sky concepts and about the \"sky teaching object\", in search of the essence of this concept along its development. We suggest a teaching proposal based on empirical results of our investigation about teachers knowledge and the possibility of teaching astronomy as proposed by curricula. We hope this proposal may enable students to acquire the human culture developed in the course of history besides developing their potential as human beings in a universal perspective that enables the construction of a feeling from theoretical ideas in an abstract to concrete ascension motion, as defined by the theory on which this work is based.
46
López, Coto Rubén. "Very-high-energy -ray observations of pulsar wind nebulae and cataclysmic variable stars with MAGIC and development of trigger systems for IACTs." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/299795.
Full textAbstract:
La historia de la astronomía es tan antigua como alcanzan nuestros registros. Todas
las civilizaciones han estado interesadas en el estudio del cielo nocturno, sus objetos
y fenómenos. Estas observaciones se realizaron a simple vista hasta el comienzo
del siglo XVII, cuando Galileo Galilei empezó a usar un instrumento desarrollado
recientemente llamado telescopio. Desde entonces, el rango de longitudes de onda
accesible ha ido creciendo, con una explosión en el siglo XX gracias al desarrollo de
instrumentos para observar los diferentes rangos: antenas (radio y submilimétrico),
telescopios (óptico e infrarrojo) y satélites (ultravioleta, rayos X y rayos gamma de
baja energía). Las últimas longitudes de onda del espectro electromagntico a las que
se han accedido han sido los rayos gamma de muy alta energía. En este rango, los
flujos son tan bajos que no pueden ser observados por instrumentos espaciales, cuyas
áreas de colcción típicas son del orden de O(1) m2. Para detectar esta radiación,
usamos la conocida como “imaging atmospheric Cherenkov technique”, basada en la
detección de los flashes de luz Cherenkov que los rayos gamma de muy alta energía
producen cuando interaccionan con la atmósfera. Este campo es muy joven, con
la primera fuente descubierta en 1989 por el pionero telescopio Whipple. Es muy
dinámico, con más de 150 fuentes detectadas hasta la fecha, la mayoría de ellas por
MAGIC, HESS y VERITAS, que forman la generación actual de estos instrumentos.
Finalmente, el campo es también muy prometedor, con la preparación de la siguiente
generación de telescopios de este tipo: CTA, una matriz de telescopios que se espera
completar en 2020.
El trabajo presentado en esta tesis comprende todos los esfuerzos que he realizado
para hacer que la astronomía de rayos gammas usando telescopios Cherenkov avance.
La Parte I de la tesis es una introducción al universo no térmico, la técnica de “imaging
atmospheric Cherenkov” y los IACTs MAGIC and CTA. La Parte II comprende
todo el trabajo técnico realizado para conseguir bajar el umbral de energía de los
IACTs. Esta parte incluye la simulación, caracterización y test del sistema de trigger
analógico dise˜nado para alcanzar el umbral de energía más bajo posible con los
LSTs de CTA. Junto a este trabajo, se ha buscado mejorar el sistema de trigger del
telescopio MAGIC simulando, testando y poniendo en marcha un nuevo concepto de
sistema de trigger estéreo para MAGIC . Este nuevo sistema, que usa la información
de la posición de las cascadas en cada una de las cámaras de MAGIC para eliminar
ruido, se denomina “Topo-trigger”.
La parte científica de la tesis trata de fuentes galácticas observadas con los telescopiosMAGIC
En la Parte III hablo del análisis de la emisión de rayos gamma de muy alta energía de pleriones: El descubrimiento de emisión de rayos gamma de muy alta
energía del desconcertante plerión 3C 58, probable remanente de la SN 1181 AD y
el plerión más débil detectado a estas energías hasta la fecha; la caracterización de
la cola de emisión a las más altas energías detectadas desde la nebulosa del Cangrejo
observándola a los más altos ángulos zenitales posibles; y el estudio de una
componente adicional debido al efecto Compton inverso en los estallidos de rayos
gamma reportados por el satélite Fermi-LAT en el régimen de sincrotrón. La Parte
IV incluye la búsquedas de rayos gamma de muy alta energía de estrellas variables
cataclísmicas. En un contexto multibanda, estudiamos la naturaleza de la emisión de
rayos gamma de alta energía previamente declarada de la variable cataclísmica AE
Aqr. También realizamos observaciones de novas y una nova enana para desvelar
los mecanismos de aceleración que tienen lugar en este tipo de objetos y descubrir
una componente hadrónica putativa de la emisión de rayos gamma de baja energía.
Un capítulo de conclusiones resume todo el trabajo realizado y los prospectos relacionados
con los temas tratados en esta tesis.The history of astronomy is as ancient as the reach of our written records. All the human civilizations have been interested in the study and interpretation of the night sky and its objects and phenomena. These observations were performed with the naked eye until the beginning of the 17th century, when Galileo Galilei started to use an instrument recently developed called telescope. Since then, the range of accessible wavelengths has been increasing, with a burst in the 20th century with the developing of instruments to observe them: antennas (radio and submillimeter), telescopes (optical, IR) and satellites (UV, X-rays and soft gamma rays). The last wavelength range accessed was the Very-High-Energy (VHE) gamma rays. At this range fluxes are so low that it is not possible to use space-based instruments with typical collection areas of O(1) m2. We must resort to the imaging atmospheric Cherenkov technique, which is based on the detection of the flashes of Cherenkov light that VHE gamma rays produce when they interact with the Earth’s atmosphere. The field is very young, with the first source discovered in 1989 by the pioneering Whipple telescope. It is very dynamic with more than 150 sources detected to date, most of them by MAGIC, HESS and VERITAS, that make up the current generation of instruments. Finally, the field is also very promising, with the preparation of a next generation of imaging atmospheric Cherenkov telescopes: CTA, that is expected to start full operation in 2020. The work presented in this thesis comprises my e orts to take the ground-based -ray astronomy one step forward. Part I of the thesis is an introduction to the nonthermal universe, the imaging atmospheric Cherenkov technique and the Imaging Atmospheric Cherenkov Telescopes (IACTs) MAGIC and CTA. Part II deals with several ways to reduce the trigger threshold of IACTs. This includes the simulation, characterization and test of an analog trigger especially designed to achieve the lowest possible energy threshold with the LSTs of CTA. Together with this work, the trigger of the MAGIC telescopes was improved. We have simulated, tested and commissioned a new concept of stereoscopic trigger. This new system, that uses the information of the position of the showers on each of the MAGIC cameras, is dubbed “Topo-trigger”. The scientific fraction of the thesis deals with galactic sources observed with the MAGIC telescopes. In Part III, I talk about the analysis of the VHE -ray emission of Pulsar Wind Nebulae (PWNe): the discovery of VHE -ray emission from the puzzling PWN 3C 58, the likely remnant of the SN 1181 AD and the weakest PWN detected at VHE to date; the characterization of the VHE tail of the Crab nebula by observing it at the highest zenith angles; and the search for an additional inverse Compton component during the Crab nebula flares reported by Fermi-LAT in the synchrotron regime. Part IV is concerned with searches for VHE -ray emission of cataclysmic variable stars. I studied, on a multiwavelength context, the VHE -ray nature of the previously claimed pulsed -ray emission of the cataclysmic variable AE Aqr. I also performed observations of novae and a dwarf nova to pinpoint the acceleration mechanisms taking place in this kind of objects and to discover a putative hadronic component of the soft -ray emission. A conclusion chapter summarizes all the work performed and lists prospects related with the topics treated in this thesis.
47
Fors, Aldrich Octavi. "New Observational Techniques and Analysis Tools for Wide Field CCD Surveys and High Resolution Astrometry." Doctoral thesis, Universitat de Barcelona, 2006. http://hdl.handle.net/10803/745.
Full textAbstract:
The aim of this thesis is two-fold. First it provides a general methodology for applying image deconvolution to wide-field CCD imagery. Second, two new CCD observational techniques and two data analysis tools are proposed for the first time in the context of high resolution astrometry, in particular for lunar occultations and speckle interferometry observations.In the first part of the thesis a wavelet-based adaptive image deconvolution algorithm (AWMLE) has been applied to two sets of survey type CCD data: QUasar Equatorial Survey Team project(QUEST and Near-Earth Space Surveillance Terrestrial(NESS-T). Richardson-Lucy image deconvolution has also been used with Flagstaff Transit Telescope (FASTT)imagery. Both the obtaining and performance of those images were accomplished by following a new methodology which includes accurate image calibration, source detection and centering, and correct assessment procedures of the performance of the deconvolution. Results show that AWMLE deconvolution can increase limiting magnitude up to 0.6 mag and improve limiting resolution 1 pixel with respect to original image. These studies have been conducted in the context of programs dedicated to macrolensing search (QUEST) and NEOs discovery(NESS-T). Finally, astrometric accuracy of FASTT images have not been found to change significantly after deconvolution. In the same way, no positional bias towards the centre of the pixel has been observed.
In the second part of the thesis a new observational technique based on CCD fast drift scanning has been proposed, implemented and assessed for lunar occultations (LO) and speckle interferometry observations.
In the case of LO, the technique yielded positive detection of binaries up to 2 milliarcseconds of projected separation and stellar diameters measurements in the 7 milliarcsecond regime. The proposed technique implies no optical or mechanical additional adjustments and can be applied to nearly all available full frame CCDs. Thus, it enables all kind of professional and high-end amateur observatories for LO work. Complementary to this work, a four-year LO program (CALOP) at Calar Alto Observatory spanning 71.5 nights of observation and 388 recorded events has been conducted by means of CCD and MAGIC IR array cameras at OAN 1.5m and CAHA 2.2m telescopes. CALOP results include the detection of one triple system and 14 new and 1 known binaries in the near-IR, and one binary in the visible. Their projected separations range from 90 to 2 milliarcseconds with brightness ratios up to 1:35 in the K band. Several angular diameters have been also measured in the near-IR. The performance of CALOP has been calibrated in terms of limiting magnitude (K down to 9.0) and limiting angular resolution (1-3 milliarcseconds).
In addition, the binary detection probability of the program has found to be about 4%. Finally, a new wavelet-based method for extracting and characterizing LO lightcurves in an automated fashion was proposed, implemented and applied to CALOP database. This pipeline addresses the need of disposing of preliminary results in immediate basis for future programs which will provide larger number of events.
In the case of speckle interferometry, CCD fast drift scanning technique has been validated with the observation of four binary systems with well determined orbits. The results of separation, position angle and magnitude difference are in accordance with published measurements by other observers and predicted orbits. Error estimates for these have been found to be 0.017 arcseconds, 1.5 degrees and 0.34 mag, respectively. These are in the order of other authors and can be considered as successful for a first trial of this technique.
Finally, a new approach for calibrating speckle transfer function from the binary power spectrum itself has been introduced. It does not require point source observations, which gives a more effective use of observation time. This new calibration method appears to be limited to zenith angles above 30 degrees when observing with no refraction compensation devices.
En aquest treball s'han dissenyat i desenvolupat una sèrie de noves tècniques observacionals i eines d'anàlisi de dades en dues àrees ben diferenciades. D'una banda, la deconvolució d'imatges CCD de gran camp (tipus survey). D'altra banda, l'astrometria d'alta resolució, i en particular les tècniques observacionals d'ocultacions lunars i interferometria speckle.
Quant a la primera, s'han aplicat dos algorismes de deconvolució (màxima versemblança Richardson-Lucy (MLE) i la seva variant adaptativa basada en wavelets (AWMLE)) a dades de tres projectes survey: el Flagstaff Transit Telescope (FASTT), el QUasar Equatorial Survey Team (QUEST) i el Near-Earth Space Surveillance Terrestrial (NESS-T). Els tres han vist restringida la seva magnitud i resolució límits a causa del mètode d'adquisició drift scanning (per a FASTT i QUEST) o la molt curta relació focal de l'instrument (NESS-T). S'ha proposat i implementat una nova metodologia per a l'aplicació de l'AWMLE i MLE per a les anteriors imatges. Aquesta permet avaluar la millora aportada per la deconvolució en termes d'increment de magnitud i resolució límits. A més, resulta del tot general i és exportable a altres dades survey. Els resultats obtinguts mostren que AWMLE permet aconseguir un increment en la magnitud límit de 0.6 mag i una millora en la resolució límit d'1.0 pixel. A més, s'ha comprovat que tals tendències són assimtòticament independents a partir d'un nombre d'iteracions suficientment gran. Paral·lelament, s'ha comprovat que la deconvolució MLE sobre dades FASTT no afecta significativament a la precisió astromètrica ni introdueix cap biaix posicional cap al centre del píxel.
Quant a les ocultacions lunars, s'ha ideat, desenvolupat, implementat i avaluat una nova tècnica d'observació CCD per a ocultacions lunars. Éstà basada en el mètode d'adquisició "drift scanning" i permet mostrejar la intensitat de l'objecte ocultat cada 2ms. La tècnica permet a pràcticament qualsevol observatori (professional o amateur) afrontar programes d'ocultacions lunars amb propòsits de contribució científica. Paral·lelament, s'ha portat a terme un programa d'observació d'ocultacions lunars (anomenat CALOP) que durant 4 anys i 71.5 nits s'ha portat a terme a l'Observatorio Astronómico de Calar Alto, operant tant en el visible amb CCD com en l'IR amb la càmera MAGIC. Com a resultat, s'han aconseguit mesurar 3 diàmetres estel·lars de l'ordre de 7 mil.lisegons d'arc i detectar 15 nous sistemes binaris i un triple amb separacions angulars de fins a 2 mil.lisegons d'arc. Finalment, s'ha desenvolupat i implementat un nou algorisme de reducció automàtica d'ocultacions basat en wavelets. Tal algorisme ha estat aplicat satisfactòriament en la reducció del conjunt d'ocultacions (400) registrades en el programa CALOP, i permet afrontar la reducció de futures campanyes d'observació massiva.
Quant a la interferometría speckle, s'ha ideat, desenvolupat, implementat i avaluat una nova tècnica d'observació CCD per a aquest tipus d'observacions d'alta resolució espacial. Éstà basada en el mètode d'adquisició drift scanning i permet mostrejar la intensitat de l'objecte dins de l'interval de coherència atmosfèrica. S'ha validat amb la mesura de 4 sistemes binaris d'òrbita coneguda. Els resultats de separació angular, angle de posició i diferència de magnitud estan d'acord amb els publicats per autors anteriors. La tècnica permet a pràcticament qualsevol observatori (professional o amateur) afrontar programes "speckle" amb propòsits de contribució científica. Finalment, s'ha ideat, implementat i validat una nova tècnica de autocalibració de dades speckle que permet estalviar temps d'observació.
48
Juráň, Jakub. "Vývoj systému řízení astronomického dalekohledu s možností sledování družic." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377003.
Full textAbstract:
The focus of this thesis is a development of an electronic guiding unit for a mount of an astronomical telescope allowing observations of artificial satellites orbiting the Earth. It contains a theoretical study of methods developed for the description of positions of objects observable on the celestial sphere, including systems used for storage of this information and regaining it in order to point the telescope in a specific direction. The work includes an analysis of the present supply of commercial devices, followed by a detailed description of the design developed here and its components. Finally, there is outline of possibilities of a future development of the system, focusing on software components.
49
Buxton, Michelle Maree. "Optical and infrared observations of low-mass X-ray binaries with black hole candidates." Phd thesis, 2002. http://hdl.handle.net/1885/148662.
Full text
50
Lamb, Masen. "On the calibration and use of Adaptive Optics systems: RAVEN observations of metal-poor stars in the Galactic Bulge and the application of focal plane wavefront sensing techniques." Thesis, 2017. https://dspace.library.uvic.ca//handle/1828/8368.
Full textAbstract:
Adaptive optics holds a fundamental role in the era of thirty meter class telescopes; this technology has gained such import that is incorporated into all first light instruments of both the upcoming E-ELT and TMT telescopes. Moreover, each of these telescopes are planning to use advanced forms of adaptive optics to exploit unprecedented scientific niches, such as Multi-Conjugate Adaptive Optics and Multi-Object Adaptive Optics. The complexity of these systems requires careful preliminary considerations, such as demonstration of the technology on existing telescopes and effective calibration procedures. In this thesis I address these two considerations through two different approaches. First, I demonstrate the use of the Multi-Object Adaptive Op- tics demonstrator RAVEN to gather high-resolution spectroscopy for the first time with this technology, and I identify some of the most metal-poor stars in the Galactic bulge to date. Secondly, I develop two focal plane wavefront sensing techniques to calibrate the internal aberrations of RAVEN and explore their applications to other adaptive optics systems.

I analyze spectra of individual stars in two Globular Clusters to establish infrared techniques that can be used with the RAVEN instrument. Detailed chemical abundances for five stars in NGC 5466 and NGC 5024, are presented from high-resolution optical (from the Hobby-Eberley Telescope) and infrared spectra (from the SDSS- III APOGEE survey). I find [Fe/H] = -1.97 ± 0.13 dex for NGC 5466, and [Fe/H] = -2.06 ± 0.13 dex for NGC 5024, and the typical abundance pattern for globular clusters for the remaining elements, e.g. both show evidence for mixing in their light element abundance ratios (C, N), and asymptotic giant branch contributions in their heavy element abundances (Y, Ba, and Eu). These clusters were selected to examine chemical trends that may correlate them with the Sgr dwarf galaxy remnant, but at these low metallicities no obvious differences from the Galactic abundance pattern are found. Regardless, I compare my results from the optical and infrared analyses to find that oxygen and silicon abundances determined from the infrared spectral lines are in better agreement with the other α-element ratios and with smaller random errors.
Using the aforementioned infrared techniques, I derive the chemical abundances for five metal-poor stars in and towards the Galactic bulge from the H-band spectroscopy taken with RAVEN at the Subaru 8.2-m telescope. Three of these stars are in the Galactic bulge and have metallicities between -2.1 < [Fe/H] < -1.5, and high [α/Fe] ∼ +0.3, typical of Galactic disc and bulge stars in this metallicity range; [Al/Fe] and [N/Fe] are also high, whereas [C/Fe] < +0.3. An examination of their orbits suggests that two of these stars may be confined to the Galactic bulge and one is a halo trespasser, though proper motion values used to calculate orbits are quite uncertain. An additional two stars in the globular cluster M22 show [Fe/H] values consistent to within 1σ , although one of these two stars has [Fe/H] = -2.01 ± 0.09, which is on the low end for this cluster. The [α/Fe] and [Ni/Fe] values differ by 2, with the most metal-poor star showing significantly higher values for these elements. M22 is known to show element abundance variations, consistent with a multipopulation scenario though our results cannot discriminate this clearly given our abundance uncertainties. This is the first science demonstration of multi-object adaptive optics with high-resolution infrared spectroscopy, and we also discuss the feasibility of this technique for use in the upcoming era of 30-m class telescope facilities.
Lastly, I develop two focal plane wavefront sensing techniques to calibrate the non-common path aberrations (NCPA) in adaptive optics systems. I first demonstrate these techniques in a detailed simulation of the future TMT instrument NFIRAOS. I then validate these techniques on an experimental bench subject to NFIRAOS-like wavefront errors. The two techniques are subsequently used to identify and correct the NCPA on both RAVEN and the NFIRAOS test-bench knowns as HeNOS. The application of these techniques is also explored on the VLT/SPHERE system to identify what is known as the ‘Low Wind Effect’ (LWE). I first quantify the LWE in simulation and then validate the technique on an experimental bench. I then estimate the LWE from on-sky data taken with the VLT/SPHERE adaptive optics system. Lastly, I apply my focal plane wavefront sensing techniques to estimate residual mirror co-phasing errors seen on Keck with the NIRC2 adaptive optics system data. I first demonstrate the ability of my techniques to quantify these errors in a simulation of Keck/NIRC2 data. I then apply their capabilities to estimate the mirror co-phasing errors of Keck with on-sky data.Graduate