To see the other types of publications on this topic, follow the link: Star system spectroscopy.
Dissertations / Theses on the topic 'Star system spectroscopy'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 27 dissertations / theses for your research on the topic 'Star system spectroscopy.'
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
Mukai, K. "Spectroscopic studies of AM her type systems." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376952.
Full text
2
Hansson, Annie. "Stark Spectroscopy, Lifetimes and Coherence Effects in Diatomic Molecular Systems." Doctoral thesis, Stockholm : Department of Physics, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-650.
Full text
3
Froning, Cynthia Suzanne. "The near-infrared properties of compact binary systems /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Full text
4
Blakelock, Carolyn J. "Time-resolved spectroscopy of the AM Herculis-type binary systems QQ VUL and EF ERI." Virtual Press, 1998. http://liblink.bsu.edu/uhtbin/catkey/1115429.
Full textAbstract:
Cataclysmic variable stars (CVs) are interacting binary systems. One of the stars (referred to as the primary) is a white dwarf, the other (referred to as the secondary) is usually a late main sequence star such as a red dwarf. Due to the closeness of the two stars, the white dwarf accretes gasses from the secondary. If the white dwarf does not possess a strong magnetic field, these gasses go into orbit, forming an accretion disk around the primary. If the white dwarf does possess a strong magnetic field, the gasses cannot form an accretion disk because they are entrained by the magnetic field lines. Cataclysmic variable stars in which the magnetic field is strong enough to prevent the formation of the accretion disk are called AM Herculis-type systems, after their prototype. In this study, the time-resolved spectroscopy of two AM Herculis-type binary systems, QQ Vul and EF Eri, are analyzed. In addition, Doppler Tomography, an analysis technique previously applied primarily to cataclysmic variable stars with accretion disks, is applied to these systems.Department of Physics and Astronomy
5
Bruno, Giovanni. "Characterization of transiting exoplanets : analyzing the impact of the host star on the planet parameters." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4746/document.
Full textAbstract:
Dans le cadre de ma thèse, j’ai analysé les spectres de neuf étoiles Kepler obtenus avec les relevés de vitesse radiale (VR). Cela a permis la caractérisation de leur compagnons planétaires. J’ai analysé les spectres de 21 autres étoiles CoRoT et Kepler, probablement hôtes de naines M à faible masse. Cela a permis d’'élargir l'échantillon des étoiles à faible masse avec masse et rayon mesurés. J’ai calculé l’indice d’activité chromosphérique de 31 étoiles observées avec SOPHIE/OHP, en aidant l’étude des interactions étoile-planète. J’ai étudié le comportement de SOPHIE à bas signal à bruit (S/B). J’ai déterminé l’intervalle de S/B dans lequel un spectre stellaire est fiable pour la mesure des paramètres stellaires.Dans le cadre du consortium SOPHIE, j’ai suivi l’analyse complète du système Kepler-117. Ce système multi-planétaire montre variations des périodes orbitaux dues aux échanges dynamiques entre les planètes (TTV). Pour déterminer les paramètres du système, un approche spécifique a été développé pour l’ajustement simultané de transits, VR et TTV (Bruno et al. 2015).Finalement, je me suis intéressé à l’activité stellaire dans la photométrie de transit. J’ai impl ́ementé deux logiciels de modélisation de tâches stellaires dans un code MCMC, en ajoutant l’évolution des tâches dans l’un d’eux. J’ai appliqué les logiciels au Soleil, à CoRoT-7 et à CoRoT-2. J’ai amené un étude détaillé de la courbe de lumière de CoRoT-2, et exploré les effets des tâches dans les paramètres du transit (Bruno et al., en prep.). Avec la méthode FF’ (Aigrain et al. 2012), j’ai contribué à l’exploration du lien entre la signature des tâches de CoRoT-7 et dans la photométrie et dans les VRDuring my PhD, I analyzed the spectra of nine Kepler stars obtained by radial velocity (RV) observations. This allowed the characterization of their planetary companions. I analyzed the spectra of twenty-one other CoRoT and Kepler stars, likely orbited by low-mass M dwarfs. This helped widening the sample of low-mass stars with measured mass and radius. I calculated the chromospheric activity indfex of thirty-one stars observed with SOPHIE/OHP, helping the study of star-planet interactions. I studied the behavior of SOPHIE in low signal-to-noise ratio (SNR) regime. I determinhed the SNR range in which a stellar spectrum is reliable for the measure of the stellar parameters.Within the SOPHIE consortium, I followed the complete analysis of the Kepler-117 system. This multi-planetary system presents variations in the planetary orbital periods due to their mutual dynamical interacion (TTVs). To fit the system parameters, a specific fitting approach including TTV modeling was developed. We derived the system parameters by the simultaneous fit of transits, RVs, and TTVs (Bruno et al. 2015).Finally, I addressed the problem of stellar activity in transit photometry. I implemented two starspot modeling codes into an MCMC algorithm, adding spot evolution to oneof them. I applied the codes to the Sun, CoRoT-7, and CoRoT-2. I carried an extensive study on the light curve of CoRoT-2, and explored the effects of the spots on the transit parameters (Bruno et al., in prep.). With the FF’ method (Aigrain et al. 2012), I contributed to explore the connection between the photometric and RV signature of starspots in CoRoT-7
6
Johnson-Groh, Mara, Christian Marois, Rosa Robert J. De, Eric L. Nielsen, Julien Rameau, Sarah Blunt, Jeffrey Vargas, et al. "Integral Field Spectroscopy of the Low-mass Companion HD 984 B with the Gemini Planet Imager." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623816.
Full textAbstract:
We present new observations of the low-mass companion to HD 984 taken with the Gemini Planet Imager (GPI) as a part of the GPI Exoplanet Survey campaign. Images of HD 984 B were obtained in the J (1.12-1.3 mu m) and H (1.50-1.80 mu m) bands. Combined with archival epochs from 2012 and 2014, we fit the first orbit to the companion to find an 18 au (70-year) orbit with a 68% confidence interval between 14 and 28 au, an eccentricity of 0.18 with a 68% confidence interval between 0.05 and 0.47, and an inclination of 119 degrees with a 68% confidence interval between 114 degrees and 125 degrees. To address the considerable spectral covariance in both spectra, we present a method of splitting the spectra into low and high frequencies to analyze the spectral structure at different spatial frequencies with the proper spectral noise correlation. Using the split spectra, we compare them to known spectral types using field brown dwarf and low-mass star spectra and find a best-fit match of a field gravity M6.5 +/- 1.5 spectral type with a corresponding temperature of 2730(-180)(+120)K. Photometry of the companion yields a luminosity of log(L-bol/L-circle dot) = -2.88 +/- 0.07 dex with DUSTY models. Mass estimates, again from DUSTY models, find an age-dependent mass of 34 +/- 1 to 95 +/- 4 M-Jup. These results are consistent with previous measurements of the object.
7
Silverman, Lisa Nicole. "Stark spectroscopy as a probe of charge reorganization in chemical and biological systems /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
8
Hełminiak, K. G., M. Kuzuhara, K. Mede, T. D. Brandt, R. Kandori, T. Suenaga, N. Kusakabe, et al. "SEEDS DIRECT IMAGING OF THE RV-DETECTED COMPANION TO V450 ANDROMEDAE, AND CHARACTERIZATION OF THE SYSTEM." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622454.
Full textAbstract:
We report the direct imaging detection of a low-mass companion to a young, moderately active star V450. And, that was previously identified with the radial velocity (RV) method. The companion was found in high-contrast images obtained with the Subaru Telescope equipped with the HiCIAO camera and AO188 adaptive optics system. From the public ELODIE and SOPHIE archives we extracted available high-resolution spectra and RV measurements, along with RVs from the Lick planet search program. We combined our multi-epoch astrometry with these archival, partially unpublished RVs, and found that the companion is a low-mass star, not a brown dwarf, as previously suggested. We found the best-fitting dynamical masses to be m(1) = 1.141(-0.091)(+0.037)and m(2) = 0.279(-0.020)(+0.023) M-circle dot. We also performed spectral analysis of the SOPHIE spectra with the iSpec code. Hipparcos time-series photometry shows a periodicity of P = 5.743 day, which is also seen in the SOPHIE spectra as an RV modulation of the star A. We interpret it as being caused by spots on the stellar surface, and the star to be rotating with the given period. From the rotation and level of activity, we found that the system is 380(-100)(+220) Myr old, consistent with an isochrone analysis (220(-90)(+2120) Myr). This work may serve as a test case for future studies of low-mass stars, brown dwarfs, and exoplanets by combination of RV and direct imaging data.
9
Arenas, Villarroel Jose L. "Spectroscopy of the nova-like system UX UMa and three classical novae : V603 Aql, BT Mon and V1425 Aql." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341306.
Full text
10
Kellogg, Kendra, L. Prato, Guillermo Torres, G. H. Schaefer, I. Avilez, D. Ruíz-Rodríguez, L. H. Wasserman, et al. "The TWA 3 Young Triple System: Orbits, Disks, Evolution." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625499.
Full textAbstract:
We have characterized the spectroscopic orbit of the TWA 3A binary and provide preliminary families of probable solutions for the TWA 3A visual orbit, as well as for the wide TWA 3A-B orbit. TWA 3 is a hierarchical triple located at 34 pc in the similar to 10 Myr old TW Hya association. The wide component separation is 1."55; the close pair was first identified as a possible binary almost 20 years ago. We initially identified the 35-day period orbital solution using high-resolution infrared spectroscopy that angularly resolved the A and B components. We then refined the preliminary orbit by combining the infrared data with a reanalysis of our high-resolution optical spectroscopy. The orbital period from the combined spectroscopic solution is similar to 35 days, the eccentricity is similar to 0.63, and the mass ratio is similar to 0.84; although this high mass ratio would suggest that optical spectroscopy alone should be sufficient to identify the orbital solution, the presence of the tertiary B component likely introduced confusion in the blended optical spectra. Using millimeter imaging from the literature, we also estimate the inclinations of the stellar orbital planes with respect to the TWA 3A circumbinary disk inclination and find that all three planes are likely misaligned by at least similar to 30 degrees. The TWA 3A spectroscopic binary components have spectral types of M4.0 and M4.5; TWA 3B is an M3. We speculate that the system formed as a triple, is bound, and that its properties were shaped by dynamical interactions between the inclined orbits and disk.
11
Martinez, Arturo O., Ian J. M. Crossfield, Joshua E. Schlieder, Courtney D. Dressing, Christian Obermeier, John Livingston, Simona Ciceri, et al. "Stellar and Planetary Parameters for K2's Late-type Dwarf Systems from C1 to C5." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623204.
Full textAbstract:
The NASA K2 mission uses photometry to find planets transiting stars of various types. M dwarfs are of high interest since they host more short-period planets than any other type of main-sequence star and transiting planets around M dwarfs have deeper transits compared to other main-sequence stars. In this paper, we present stellar parameters from K and M dwarfs hosting transiting planet candidates discovered by our team. Using the SOFI spectrograph on the European Southern Observatory's New Technology Telescope, we obtained R approximate to 1000 J-, H-, and K-band (0.95-2.52 mu m) spectra of 34 late-type K2 planet and candidate planet host systems and 12 bright K4-M5 dwarfs with interferometrically measured radii and effective temperatures. Out of our 34 late-type K2 targets, we identify 27 of these stars as M dwarfs. We measure equivalent widths of spectral features, derive calibration relations using stars with interferometric measurements, and estimate stellar radii, effective temperatures, masses, and luminosities for the K2 planet hosts. Our calibrations provide radii and temperatures with median uncertainties of 0.059 R-circle dot (16.09%) and 160 K (4.33%), respectively. We then reassess the radii and equilibrium temperatures of known and candidate planets based on our spectroscopically derived stellar parameters. Since a planet's radius and equilibrium temperature depend on the parameters of its host star, our study provides more precise planetary parameters for planets and candidates orbiting late-type stars observed with K2. We find a median planet radius and an equilibrium temperature of approximately 3 R-circle plus and 500 K, respectively, with several systems (K2-18b and K2-72e) receiving near-Earth-like levels of incident irradiation.
12
Garcia, E. Victor, Thayne Currie, Olivier Guyon, Keivan G. Stassun, Nemanja Jovanovic, Julien Lozi, Tomoyuki Kudo, et al. "SCExAO AND GPI Y JH BAND PHOTOMETRY AND INTEGRAL FIELD SPECTROSCOPY OF THE YOUNG BROWN DWARF COMPANION TO HD 1160." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623097.
Full textAbstract:
We present high signal-to-noise ratio, precise Y JH photometry and Y band (0.957-1.120 mu m) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5(-0.5)(+1.0), where the blue edge of our Y band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B has an effective temperature of 3000-3100 K, a surface gravity of log g - 4-4.5, a radius of. 1.55 +/- 0.10 R-J, and a luminosity of log L/L circle dot - 2.76 +/- 0.05. Neither the primary's Hertzspring-Russell diagram position nor atmospheric modeling of HD 1160 B show evidence for a subsolar metallicity. Interpretation of the HD 1160 B spectroscopy depends on which stellar system components are used to estimate the age. Considering HD 1160 A, B and C jointly, we derive an age of 80-125 Myr, implying that HD 1160 B straddles the hydrogen-burning limit (70-90 M-J) If we consider HD 1160 A alone, younger ages (20-125 Myr) and a brown dwarf-like mass (35-90 M-J) are possible. Interferometric measurements of the primary, a precise Gaia parallax, and moderate-resolution spectroscopy can better constrain the system's age and how HD 1160 B fits within the context of (sub) stellar evolution.
13
Christiansen, Jessie L., Andrew Vanderburg, Jennifer Burt, B. J. Fulton, Konstantin Batygin, Björn Benneke, John M. Brewer, et al. "Three’s Company: An Additional Non-transiting Super-Earth in the Bright HD 3167 System, and Masses for All Three Planets." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625817.
Full textAbstract:
HD 3167 is a bright (V = 8.9), nearby KO star observed by the NASA K2 mission (EPIC 220383386), hosting two small, short-period transiting planets. Here we present the results of a multi-site, multi-instrument radial-velocity campaign to characterize the HD 3167 system. The masses of the transiting planets are 5.02 +/- 0.38 M-circle plus for HD 3167 b, a hot super-Earth with a likely rocky composition (rho(b) = 5.6(-1.43)(+2.15) g cm(-3)), and 9.80(-1.24)(+1.30) M-circle plus for HD 3167 c, a warm sub-Neptune with a likely substantial volatile complement (rho(c) = 1.97(-0.59)(+0.94) g cm(-3)). We explore the possibility of atmospheric composition analysis and determine that planet c is amenable to transmission spectroscopy measurements, and planet b is a potential thermal emission target. We detect a third, non-transiting planet, HD 3167 d, with a period of 8.509 +/- 0.045 d (between planets b and c) and a minimum mass of 6.90 +/- 0.71 M-circle plus. We are able to constrain the mutual inclination of planet d with planets b and c: we rule out mutual inclinations below 1.degrees 3 because we do not observe transits of planet d. From 1.degrees 3 to 40 degrees, there are viewing geometries invoking special nodal configurations, which result in planet d not transiting some fraction of the time.
14
De, Rosa Robert J., Julien Rameau, Jenny Patience, James R. Graham, René Doyon, David Lafrenière, Bruce Macintosh, et al. "SPECTROSCOPIC CHARACTERIZATION OF HD 95086 b WITH THE GEMINI PLANET IMAGER." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621382.
Full textAbstract:
We present new H (1.51.8 mu m) photometric and K-1 (1.92.2 mu m) spectroscopic observations of the young exoplanet HD 95086 b obtained with the Gemini Planet Imager. The Hband magnitude has been significantly improved relative to previous measurements, whereas the lowresolution K-1 (lambda/delta lambda approximate to 66) spectrum is featureless within the measurement uncertainties and presents a monotonically increasing pseudocontinuum consistent with a cloudy atmosphere. By combining these new measurements with literature L' photometry, we compare the spectral energy distribution (SED) of the planet to other young planetarymass companions, field brown dwarfs, and to the predictions of grids of model atmospheres. HD 95086 b is over a magnitude redder in K-1 - L' color than 2MASS J120733463932539 b and HR 8799 c and d, despite having a similar L' magnitude. Considering only the near-infrared measurements, HD 95086 b is most analogous to the brown dwarfs 2MASS J2244316+204343 and 2MASS J21481633+4003594, both of which are thought to have dusty atmospheres. Morphologically, the SED of HD 95086 b is best fit by low temperature (T-eff = 8001300 K), low surface gravity spectra from models which simulate high photospheric dust content. This range of effective temperatures is consistent with field L/T transition objects, but the spectral type of HD 95086 b is poorly constrained between early L and late T due to its unusual position the colormagnitude diagram, demonstrating the difficulty in spectral typing young, low surface gravity substellar objects. As one of the reddest such objects, HD 95086 b represents an important empirical benchmark against which our current understanding of the atmospheric properties of young extrasolar planets can be tested.
15
Sinukoff, Evan, Andrew W. Howard, Erik A. Petigura, Joshua E. Schlieder, Ian J. M. Crossfield, David R. Ciardi, Benjamin J. Fulton, et al. "ELEVEN MULTIPLANET SYSTEMS FROM K2 CAMPAIGNS 1 AND 2 AND THE MASSES OF TWO HOT SUPER-EARTHS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621388.
Full textAbstract:
We present a catalog of 11 multiplanet systems from Campaigns 1 and 2 of the K2 mission. We report the sizes and orbits of 26 planets split between seven two-planet systems and four three-planet systems. These planets stem from a systematic search of the K2 photometry for all dwarf stars observed by K2 in these fields. We precisely characterized the host stars with adaptive optics imaging and analysis of high-resolution optical spectra from Keck/HIRES and medium-resolution spectra from IRTF/SpeX. We confirm two planet candidates by mass detection and validate the remaining 24 candidates to >99% confidence. Thirteen planets were previously validated or confirmed by other studies, and 24 were previously identified as planet candidates. The planets are mostly smaller than Neptune (21/26 planets), as in the Kepler mission, and all have short periods (P < 50 days) due to the duration of the K2 photometry. The host stars are relatively bright (most have Kp < 12.5 mag) and are amenable to follow-up characterization. For K2-38, we measured precise radial velocities using Keck/HIRES and provide initial estimates of the planet masses. K2-38b is a short-period super-Earth with a radius of 1.55 +/- 0.16 R-circle plus, a mass of 12.0 +/- 2.9M(circle plus), and a high density consistent with an iron-rich composition. The outer planet K2-38c is a lower-density sub-Neptune-size planet with a radius of 2.42 +/- 0.29 R-circle plus and a mass of 9.9 +/- 4.6M(circle plus) that likely has a substantial envelope. This new planet sample demonstrates the capability of K2 to discover numerous planetary systems around bright stars.
16
Ramm, David John. "A spectroscopic study of detached binary systems using precise radial velocities." Thesis, University of Canterbury. Physics and Astronomy, 2004. http://hdl.handle.net/10092/1525.
Full textAbstract:
Spectroscopic orbital elements and/or related parameters have been determined for eight binary systems, using radial-velocity measurements that have a typical precision of about 15 ms⁻¹. The orbital periods of these systems range from about 10 days to 26 years, with a median of about 6 years. Orbital solutions were determined for the seven systems with shorter periods. The measurement of the mass ratio of the longest-period system, HD217166, demonstrates that this important astrophysical quantity can be estimated in a model-free manner with less than 10% of the orbital cycle observed spectroscopically.\\ Single-lined orbital solutions have been derived for five of the binaries. Two of these systems are astrometric binaries: β Ret and ν Oct. The other SB1 systems were 94 Aqr A, θ Ant, and the 10-day system, HD159656. The preliminary spectroscopic solution for θ Ant (P~18 years), is the first one derived for this system. The improvement to the precision achieved for the elements of the other four systems was typically between 1--2 orders of magnitude. The very high precision with which the spectroscopic solution for HD159656 has been measured should allow an investigation into possible apsidal motion in the near future. In addition to the variable radial velocity owing to its orbital motion, the K-giant, ν Oct, has been found to have an additional long-term irregular periodicity, attributed, for the time being, to the rotation of a large surface feature.\\ Double-lined solutions were obtained for HD206804 (K7V+K7V), which previously had two competing astrometric solutions but no spectroscopic solution, and a newly discovered seventh-magnitude system, HD181958 (F6V+F7V). This latter system has the distinction of having components and orbital characteristics whose study should be possible with present ground-based interferometers. All eight of the binary systems have had their mass ratio and the masses of their components estimated.\\ The following comments summarize the motivation for getting these results, and the manner in which the research was carried out. \\ The majority of stars exist in binary systems rather than singly as does the Sun. These systems provide astronomers with the most reliable and proven means to determine many of the fundamental properties of stars. One of these properties is the stellar mass, which is regarded as being the most important of all, since most other stellar characteristics are very sensitive to the mass. Therefore, empirical masses, combined with measurements of other stellar properties, such as radii and luminosities, are an excellent test for competing models of stellar structure and evolution.\\ Binary stars also provide opportunities to observe and investigate many extraordinary astrophysical processes that do not occur in isolated stars. These processes often arise as a result of direct and indirect interactions between the components, when they are sufficiently close to each other. Some of the interactions are relatively passive, such as the circularization of the mutual orbits, whilst others result from much more active processes, such as mass exchange leading to intense radiation emissions. \\ A complete understanding of a binary system's orbital characteristics, as well as the measurement of the all-important stellar masses, is almost always only achieved after the binary system has been studied using two or more complementary observing techniques. Two of the suitable techniques are astrometry and spectroscopy. In favourable circumstances, astrometry can deduce the angular dimensions of the orbit, the total mass of the system, and sometimes, its distance from us. Spectroscopy, on the other hand, can determine the linear scale of the orbit and the ratio of the stellar masses, based on the changing radial velocities of both stars. When a resolved astrometric orbital solution is also available, the velocities of both stars can allow the binary system's parallax to be determined, and the velocities of one star can provide a measure of the system mass ratio.\\ Unfortunately, relatively few binary systems are suited to these complementary studies. Underlying this difficulty are the facts that, typically, astrometrically-determined orbits favour those with periods of years or decades, whereas spectroscopic orbital solutions are more often measured for systems with periods of days to months. With the development of high-resolution astrometric and spectroscopic techniques in recent years, it is hoped that many more binary systems will be amenable to these complementary strategies.\\ Several months after this thesis began, a high-resolution spectrograph, HERCULES, commenced operations at the Mt John University Observatory, to be used in conjuction with the 1-metre McLellan telescope. For late-type stars, the anticipated velocity precision was ≲10 ms⁻¹. The primary goals of this thesis were: 1.~to assess the performance of HERCULES and the related reduction software that subsequently followed, 2.~to carry out an observational programme of 20 or so binary systems, and 3.~to determine the orbital and stellar parameters which characterize some of these systems. The particular focus was on those binaries that have resolved or unresolved astrometric orbital solutions, which therefore may be suited to complementary investigations.\\ HERCULES was used to acquire spectra of the programme stars, usually every few weeks, over a timespan of about three years. High-resolution spectra were acquired for the purpose of measuring precise radial velocities of the stars. When possible, orbital solutions were derived from these velocities, using the method of differential corrections.
17
Neves, Vasco de Matos Ferreira Mendes. "Abundances of elements in exoplanet host stars." Master's thesis, Universidade de Aveiro, 2008. http://hdl.handle.net/10773/15237.
Full textAbstract:
Mestrado em FísicaIn this work we present an uniform study of the chemical abundances of 12 elements (Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg and Al) derived from the spectra of 451 stars of one of the HARPS GTO planet search programs, which has 66 planet bearing stars. The main goal of this study is the investigation of the possible differences between the abundances of the stars with and without planets. We have confirmed that there is an overabundance of metallicity in planet host stars, common to all species, as expected. We have also found that there is no difference in the galactic chemical evolution trends between stars with and without planets, as observed in the [X/Fe] vs. [Fe/H] plots. The stars that harbour planetary companions simply seem to be in the high metallicity tail of the distribution. We have only found one case of clear overabundance for a fixed [Fe/H] (HD147513) where the pollution scenario might be important. This particular star needs to be investigated in a future work. We also need to explore the possibility of the existence of a different population of stars with high [X/Fe] ratios in the region of [Fe/H] < 0 that was detected in the plots of [X/Fe] vs [Fe/H].
Neste trabalho apresentamos um estudo uniforme de abundâncias químicas de 12 elementos (Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg e Al) a partir dos espectros de 451 estrelas de um dos programas HARPS GTO de procura de exoplanetas. Destas estrelas, 66 têm planetas confirmados. O objectivo principal deste trabalho é a investigação das possíveis diferenças entre as abundâncias químicas de estrelas com e sem planetas. Confirmámos que existe uma maior abundância química de todos os elementos nas estrelas com planetas, como era esperado. Constatámos também, através da análise dos gráficos de [X/Fe] vs. [Fe/H], que não existem diferenças nas tendências da evolução química da galáxia entre estrelas com e sem planetas. As estrelas que têm planetas parecem estar apenas no extremo de maior metalicidade da distribuição. Encontrámos apenas um caso em que se verifica uma maior abundância de alguns elementos para um [Fe/H] fixo (HD147513), onde o cenário de enriquecimento químico por poluição poderá ser importante. Este caso em particular precisa de ser investigado num trabalho futuro. É necessário também explorar a possível existência de uma população diferente de estrelas com maior metalicidade na região de [Fe/H] < 0 detectada nos gráficos de [X/Fe] vs. [Fe/H].
18
Fischer, Patrick D., Heather A. Knutson, David K. Sing, Gregory W. Henry, Michael W. Williamson, Jonathan J. Fortney, Adam S. Burrows, et al. "HST HOT-JUPITER TRANSMISSION SPECTRAL SURVEY: CLEAR SKIES FOR COOL SATURN WASP-39b." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621278.
Full textAbstract:
We present the. Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) optical transmission spectroscopy of the cool Saturn-mass exoplanet WASP-39b from 0.29-1.025 mu m, along with complementary transit observations from Spitzer IRAC at 3.6 and 4.5 mu m. The low density and large atmospheric pressure scale height of WASP-39b make it particularly amenable to atmospheric characterization using this technique. We detect a Rayleigh scattering slope as well as sodium and potassium absorption features; this is the first exoplanet in which both alkali features are clearly detected with the extended wings predicted by cloud-free atmosphere models. The full transmission spectrum is well matched by a clear H-2-dominated atmosphere, or one containing a weak contribution from haze, in good agreement with the preliminary reduction of these data presented in Sing et al.. WASP-39b is predicted to have a pressure-temperature profile comparable to that of HD 189733b and WASP-6b, making it one of the coolest transiting gas giants observed in our HST STIS survey. Despite this similarity, WASP-39b appears to be largely cloud-free, while the transmission spectra of HD 189733b and WASP-6b both indicate the presence of high altitude clouds or hazes. These observations further emphasize the surprising diversity of cloudy and cloud-free gas giant planets in short-period orbits and the corresponding challenges associated with developing predictive cloud models for these atmospheres.
19
Ozbey, Mehtap. "The Optical Spectroscopic And Photometric Observations Of The Optical Counterparts To The Be/x-ray Binary Systems: Gro J2058+42 And V0332+53." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609774/index.pdf.
Full textAbstract:
The spectroscopic and photometric observations of the optical
counterparts to the Be/X-ray binary systems GRO J2058+42 and V0332+53 (BQ Cam), taken with RTT150 (Russian-Turkish 1.5 meter Telescope), are presented in this study. The distance, color and the reddening estimates for both sources, obtained via photometric observations, are consistent with the previous results. The results of our spectroscopic observations performed between May 2006 and June 2008 for optical counterpart to GRO J2058+42 indicate that the double-peaked emission line profile turns into a single-peaked
emission after the last outburst of the system. Furthermore, the spectra of the source show clear evidence for the changes in the ratio of the double peaks of H alpha emission line indicative of the precession of the high-density regions confined in the disk. Unlike the spectra of counterpart to GRO J2058+42, the spectra of BQ Cam, taken between September 2006 and December 2007, exhibit single-peaked H alpha and HeI (Lambda 7065 Angstrom) emission lines. In addition, the equivalent width values of H alpha emission lines, shifts from the the laboratory wavelengths for H alpha and HeI emission lines and the variation in optical brightness of BQ Cam show a close correlation.
20
Dallow, Andrew Thomas. "Investigating the Enigmatic Orbit of the Suspected 2.5 MJ Planet in the Nu Octantis Binary System." Thesis, University of Canterbury. Physics and Astronomy, 2012. http://hdl.handle.net/10092/10364.
Full textAbstract:
ν Octantis is a spectroscopic binary with a semi-major axis and period of 2.55 AU and 2.9 years, respectively. Ramm et al. (2009) discovered a 52 ms^(-1) radial-velocity (RV) perturbation with a period of 417 days in this system. All evidence, both photometric and spectroscopic, suggests the perturbation is the result of a 2.5 MJ planet orbiting the primary star. However, when assuming a “normal” prograde coplanar orbit, celestial mechanics predicts this orbit is unstable, contradicting the observed stability.
Simulations by Eberle and Cuntz (2010) showed a retrograde orbit for the planet to be stable for at least 10^7 years. In this thesis, we performed a 10^8 -yr simulation of the retrograde orbit, and found it remained stable. Simulations over a range of planetary semi-major axes, eccentricities, and primary/secondary masses showed that stable retrograde orbits are not possible past a semi-major axis of 1.315 +/- 0.092 AU . Therefore, planetary retrograde orbits are most likely inherently more stable than prograde orbits owing to the absence of stability at known mean-motion resonances.
Eccentricity simulations showed that the period of the planet's dominant eccentricity variation is related to the planet's semi-major axis by a second order exponential. However, retrograde orbits tend to have longer eccentricity periods than prograde orbits at the same semi-major axis. There is also evidence that this eccentricity period is connected to the orbital stability.
By fitting a keplerian to both Ramm et al. (2009) and current radial velocities, the period of the ν Octantis binary was determined to be 1050.04 +/- 0.02 days with an eccentricity of 0.2359 +/- 0.001 . The planetary orbital solution for just the data reduced in this thesis gave a period of 416.9 +/- 2.1 days and an eccentricity of 0.099 +/- 0.015 , with an RMS scatter of 9.6 ms^(-1). Therefore, the orbital elements are within 1σ of the Ramm et al. (2009) elements. Assuming a retrograde coplanar orbit about the primary star then the planet has a mass of M_pl = 2.3 M_J and a semi-major axis of a_pl = 1.21 +/- 0.09 AU.
21
Lothringer, Joshua D., Björn Benneke, Ian J. M. Crossfield, Gregory W. Henry, Caroline Morley, Diana Dragomir, Travis Barman, et al. "An HST/STIS Optical Transmission Spectrum of Warm Neptune GJ 436b." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/626526.
Full textAbstract:
GJ 436b is a prime target for understanding warm Neptune exoplanet atmospheres and a target for multiple James Webb Space Telescope (JWST) Guaranteed Time Observation programs. Here, we report the first space-based optical transmission spectrum of the planet using two Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) transit observations from 0.53 to 1.03 mu m. We find no evidence for alkali absorption features, nor evidence of a scattering slope longward of 0.53 mu m. The spectrum is indicative of moderate to high metallicity (similar to 100-1000x solar), while moderate-metallicity scenarios (similar to 100x. solar) require aerosol opacity. The optical spectrum also rules out some highly scattering haze models. We find an increase in transit depth around 0.8 mu m in the transmission spectra of three different sub-Jovian exoplanets (GJ 436b, HAT-P-26b, and GJ 1214b). While most of the data come from STIS, data from three other instruments may indicate this is not an instrumental effect. Only the transit spectrum of GJ 1214b is well fit by a model with stellar plages on the photosphere of the host star. Our photometric monitoring of the host star reveals a stellar rotation rate of 44.1 days and an activity cycle of 7.4 years. Intriguingly, GJ 436 does not become redder as it gets dimmer, which is expected if star spots were dominating the variability. These insights into the nature of the GJ 436 system help refine our expectations for future observations in the era of JWST, whose higher precision and broader wavelength coverage will shed light on the composition and structure of GJ 436b's atmosphere.
22
Gullikson, Kevin Carl. "Towards spectroscopic detection of low mass ratio stellar binary systems." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-08-6275.
Full textAbstract:
Detection of the emission from the secondary component in a binary system can be extremely challenging, but equally rewarding. In the case of intermediate to high-mass binaries, detection of close companions can inform formation theories. In the extreme low mass-ratio case, where the secondary component is in fact a planet, detection of the emission in high resolution spectroscopy can be used to determine the true planet mass. In this thesis, we describe a technique to detect the thermal emission from the secondary component of a low mass-ratio binary system. We apply this technique to archived observations of early B-type stars using VLT/CRIRES, and simulate future observations of planetary systems with IGRINS, a near-infrared spectrograph being built now.text
23
Veicht, Aaron Michael. "Through the Forest of Speckles: Robust Spectroscopy of Extremely Faint Companions of Nearby Stars." Thesis, 2016. https://doi.org/10.7916/D8TT4QWM.
Full textAbstract:
The discovery and characterization of exoplanetary systems is a new exciting field. At just over two decades old, it has already fundamentally reshaped our knowledge of planet and solar system formation. We now know that there is a vast diversity of planetary systems, in highly varied, even bizarre, configurations. Known planetary bodies span all masses from objects less massive and smaller than Earth to objects as large as the smallest stars or brown dwarfs. They exhibit periods of but a few hours to periods spanning millennia, from nearly perfectly circular orbits to highly elliptical, from fluffy gas giants to dense rocky worlds, from purely metallic worlds to water worlds. Exoplanets come in all sizes, compositions and varieties. These new discoveries have fundamentally changed the way we approach planetary science. With such a great diversity in exoplanets, we look extend our knowledge to including understanding their individual composition. We wish to understand the climate of these exoplanets and to resolve the differences between, for example, Earth-like and Venus-like planets.
To facilitate these discoveries several methods of exoplanery detection and characterization have been developed. Among them are indirect methods that infer the existence of exoplanets from their influence on their star, and direct methods that detect the light from the exoplanets themselves. Direct detection of exoplanets allows not only for a determination of the existence of the object, but also for the determination of its composition and climate through the measurement of its atmosphere's chemical composition. Using purely high-contrast direct imaging methods, coarse spectra can now be measured for exoplanets with a relative brightness 10⁻⁴-10⁻⁵ below that of the host star. Below this contrast level the companion is at the same level of brightness as the noise caused by optical defects and wave front errors in the observed light, called speckles.
In this thesis, I demonstrate the usage and optimization of a new novel technique, S4_Spectrum, to model and remove speckle noise from directly imaged systems. S4_Spectrum is capable of reducing 99% of the speckle noise. This allows for the detection and spectral characterization of exoplanets as faint as 10⁻⁶-10⁻⁷ times the brightness of their host stars. This represents two orders of magnitude gain in sensitivity. I present the design of one of these high-contrast systems, Project 1640, as well as the data collection method, including the data pipeline and analysis techniques. Also, I describe the S4_Spectrum technique in detail, as implemented in Project 1640, and present its operation and optimization. Additionally, I present the application of this new tool to obtain several spectral characterizations of objects found in the Project 1640 survey.
24
Themeẞl, Nathalie. "Asteroseismic inferences from red-giant stars." Doctoral thesis, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E5F1-E.
Full text
25
Jofré, Jorge Emiliano. "Estrellas evolucionadas con planetas : abundancias químicas y propiedades planetarias." Doctoral thesis, 2015. http://hdl.handle.net/11086/2865.
Full textAbstract:
Tesis (Doctor en Astronomía)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía y Física, 2015.Actualmente es un hecho aceptado que las estrellas de secuencia principal que albergan planetas gigantes son, en promedio, más ricas en metales que aquéllas sin planetas detectados. Sin embargo, en el caso de las estrellas evolucionadas, especialmente las gigantes, los resultados han sido más dispares o controversiales por lo que el tema permanece abierto. Por otro lado, aún se debate fuertemente si las estrellas de secuencia principal con planetas gigantes poseen menor abundancia de litio que aquéllas sin planetas detectados. El estudio de las abundancias químicas de varios elementos, como así también la exploración de sus relaciones con las propiedades planetarias cuenta con varios antecedentes en estrellas de secuencia principal con planetas, pero sólo se ha realizado ocasionalmente en estrellas evolucionadas con planetas. Este tipo de estudios es fundamental tanto para identificar las variables observables que controlan el proceso de formación y evolución de los sistemas planetarios, como también para estudiar el efecto de la formación planetaria en la estructura y evolución de las estrellas huéspedes. Así, en este trabajo presentamos parámetros fundamentales y abundancias químicas de 15 elementos para una muestra de 223 estrellas evolucionadas, incluyendo 86 con planetas. A partir de estos parámetros analizamos: i) diferencias químicas entre estrellas con y sin planetas; ii) diferencias entre las propiedades de los planetas alrededor de gigantes y subgigantes; y iii) correlaciones entre las propiedades planetarias y las abundancias químicas de sus estrellas huéspedes.
26
Lovos, Flavia Virginia. "Estudio de variabilidad fotométrica en estrellas de tipo T Tauri." Doctoral thesis, 2019. http://hdl.handle.net/11086/14315.
Full textAbstract:
Tesis (Doctor en Astronomía)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2019.Las estrellas jóvenes de tipo T Tauri tienen la edad adecuada para el inicio del proceso de formación planetaria de acuerdo a los modelos más aceptados en la actualidad. Sin embargo éstas presentan algunos desafíos para la técnica clásica de detección de planetas extrasolares mediante tránsitos planetarios. Principalmente las T Tauri manifiestan diversas formas de variabilidad que, mayormente, se evidencian en sus curvas de luz. En este trabajo se presenta un análisis y caracterización de la variabilidad fotométrica de 52 estrellas T Tauri australes, a partir de datos propios obtenidos desde el CASLEO y de la EABA, como primer paso para comprender cómo esta variabilidad puede influir en la detectabilidad de potenciales embriones planetarios transitantes. Entre los tipos de variabilidad observados, el más frecuente se debe a la presencia de manchas sobre la superficie estelar, así como otros relacionados con procesos de acreción y/o obscurecimiento por polvo en discos circunestelares.
Young pre-main sequence stars of T Tauri type have appropriate ages for the beginning of the planetary formation process according to the currently most accepted models. However, T Tauri stars offer some challenges for the classical techniques of extrasolar planets detection by means of planetary transits. Principally, T Tauri stars have different types of variability that are mostly evident in their light curves. In this work is presented an analysis and characterization of the photometric variability of 52 southern T Tauri stars, from data obtained from the CASLEO and the EABA observatories, as a first step to learn how such variability may affect the detectability of transiting planetary embryos. Among the types of variabilities, the most frequent are due to the presence of spots on the stellar surfaces, as well as others related to processes of accretion and/or darkening by dust in the circumstellar disks.
Lovos, Flavia Virginia. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.
27
Petrucci, Romina Paola. "Estudio de variaciones en los tiempos de mínimo en estrellas con planetas transitantes del Hemisferio Sur." Doctoral thesis, 2015. http://hdl.handle.net/11086/2868.
Full textAbstract:
Tesis (Doctor en Astronomía)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía y Física, 2015.En este trabajo presentamos los resultados del monitoreo y análisis homogéneo de tránsitos de planetas que orbitan alrededor de estrellas del Hemisferio Sur. El propósito principal de este seguimiento fotométrico es el de buscar variaciones en los tiempos de mínimo (TTVs) que pudieran atribuirse a la presencia de otros cuerpos de masa planetaria no detectados, ligados gravitacionalmente al sistema. Para ello realizamos observaciones con los telescopios argentinos Horacio Ghielmetti (THG) de 40 cm localizado en el Complejo Astronómico El Leoncito (CASLEO) y el telescopio de 1.54 m ubicado en la Estación Astrofísica de Bosque Alegre (EABA). Dado que se requieren muchos datos para llevar a cabo análisis de TTVs confiables, sólo estudiamos las 3 estrellas de nuestra muestra inicial que presentaron más de 10 observaciones entre propias y extraídas de la literatura. Como subproducto del análisis de variaciones en los tiempos de mínimo, para cada uno de nuestros objetos computamos nuevas efemérides y re-determinamos los parámetros físicos de la estrella y el planeta. Considerando que los puntos analizados comprenden como mínimo 3 años de observaciones, además de estudiar las variaciones a largo plazo de los tiempos de mínimo, evaluamos las variaciones en la inclinación de la órbita (i) y la profundidad del tránsito (k) que también pudieran atribuirse a la presencia de otro cuerpo de masa planetaria en el sistema.