Дисертації з теми "TeV gamma ray astrophysics"
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Bowden, Christopher Charles Geoffrey. "A search for TeV gamma ray emission from X-ray binary stars." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5631/.
Повний текст джерелаZhou, Hao. "Search for TeV gamma-ray sources in the galactic plane with the HAWC observatory." Thesis, Michigan Technological University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10004778.
Повний текст джерелаCosmic rays, with an energy density of ∼ 1eVcm–3, play an important role in the evolution of our Galaxy. Very high energy (TeV) gamma rays provide unique information about the acceleration sites of Galactic cosmic rays. The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is an all-sky surveying instrument sensitive to gamma rays from 100,GeV to 100,TeV with a 2steradian instantaneous field of view and a duty cycle of >95%. The array is located in Sierra Negra, Mexico at an elevation of 4,100m and was inaugurated in March 2015. Thanks to its modular design, science operation began in Summer 2013 with one third of the array. Using this data, a survey of the inner Galaxy region of Galactic longitude l ∈ [+15°, +50°] and latitude b ∈ [–4°, +4°] is performed. To address the ambiguities arising from unresolved sources in the data, a maximum likelihood technique is used to identify point source candidates. Ten sources and candidate sources are identified in this analysis. Eight of these are associated with known TeV sources but not all have differential fluxes compatible with previous measurements. Three sources are detected with significances >5σ after accounting for statistical trials, and are associated with known TeV sources. With data taken with the full array and improved reconstruction algorithms, the significance on the Crab nebula increases from 3.1σ√day to 5.5σ√day, which allows more sensitive sky surveys and more precise spectral and morphological analyses on individual sources.
Giebels, Berrie. "A contribution to gamma-ray astronomy of GeV-TeV Active Galaxies with Fermi and H.E.S.S." Habilitation à diriger des recherches, Ecole Polytechnique X, 2011. http://tel.archives-ouvertes.fr/tel-00672596.
Повний текст джерелаGabici, Stefano. "Gamma ray astronomy and the origin of galactic cosmic rays." Habilitation à diriger des recherches, Université Paris-Diderot - Paris VII, 2011. http://tel.archives-ouvertes.fr/tel-00719791.
Повний текст джерелаParent, Damien. "Observations de pulsars avec le Fermi Gamma-ray Space Telescope." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2009. http://tel.archives-ouvertes.fr/tel-00461405.
Повний текст джерелаAndersson, Tom. "Inverse Compton gamma-rays from Markarian 421 : A study of GeV and TeV emission from Mrk 421 based on Fermi-LAT and H.E.S.S. data." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-57861.
Повний текст джерелаKnödlseder, Jürgen. "The origin of 26Al in the Galaxy." Phd thesis, Université Paul Sabatier - Toulouse III, 1997. http://tel.archives-ouvertes.fr/tel-00145359.
Повний текст джерелаmeasurements of the 1.809 MeV gamma-ray line arising from the decay of
radioactive 26Al.
The COMPTEL telescope aboard the Compton Gamma-Ray Observatory, launched on
April 5, 1991, permits for the first time an extensive investigation of the
1.8 MeV radiation throughout the entire sky.
The aim of this thesis is to infer the galactic distribution of 26Al from
these measurements and to identify the dominant sources of this
radioactive isotope.
The first part of the thesis is dedicated to the reconstruction of
the 1.8 MeV intensity distribution from the measured data.
It is demonstrated that the use of conventional deconvolution
algorithms, like maximum likelihood or maximum entropy inversion,
leads to lumpy, noise-dominated intensity distributions.
Nevertheless, simulations can help to assess the uncertainties in the
reconstructed images, which permits the scientific exploitation of the
recovered skymaps.
Alternatively, a multiresolution approach is proposed, which largely
reduces the uncertainties in the reconstructed 1.8 MeV intensity
distribution.
In summary, 1.8 MeV emission is mainly concentrated towards the
galactic plane, which clearly demonstrates that the bulk of 26Al is of
galactic rather than local origin.
However, distinct emission features towards Cygnus, Carina, and the
Auriga-Camelopardalis-Perseus region are inconsistent with a smooth
galactic 1.8 MeV emission profile, pointing towards a massive star
origin of 26Al.
The second part of the thesis consists of a multi-wavelength
comparison of COMPTEL 1.8 MeV data which aims in the
identification of the origin of galactic 26Al.
For the comparison, a rigorous Bayesian analysis is applied, which
is the only consistent framework that allows inference based on the
comparison.
It turned out that the 1.8 MeV distribution follows very closely
the distribution of free electrons in the Galaxy which is traced by
thermal bremsstrahlung, observable in the microwave domain.
The similarity of the 1.8 MeV intensity distribution to the
thermal bremsstrahlung distribution implies a direct proportionality
between the 26Al and the massive star column densities, which strongly
supports that massive stars are the origin of galactic 26Al.
In particular, ONeMg-novae and AGB stars can be excluded as dominant
26Al sources since their galactic distribution is not expected to
correlate with the distribution of free electrons.
The correlation between 26Al and free electrons established, the
analysis of 1.8 MeV gamma-ray line emission can complement our knowledge
about star formation and the distribution of ionized gas throughout
the entire Galaxy.
While COMPTEL made the first step in providing the first all-sky map
in the light of the 1.809 MeV line, INTEGRAL, the next generation gamma-ray spectrometer, will allow a detailed study of current star formation
in the Galaxy.
Rogers, Martin John. "Gamma-ray evidence for cosmic-ray sources." Thesis, Durham University, 1988. http://etheses.dur.ac.uk/6343/.
Повний текст джерелаZabalza, de Torres Victor. "The keV-TeV connection in gamma-ray binaries." Doctoral thesis, Universitat de Barcelona, 2011. http://hdl.handle.net/10803/33649.
Повний текст джерелаLes binàries de raigs gamma són sistemes binaries formats per una estrella jove i massiva i un objecte compacte, que pot ser un púlsar jove o un forat negre, que emeten radiació fins a desenes de TeV i mostren variabilitat orbital en totes les bandes d'emissió, des de radio fins a raigs gamma. En el cas de tres de les quatre binàries de raigs gamma detectades avui dia, se'n desconeix la natura de l'objecte compacte. En aquesta tesi presentem un estudi de les binàries de raigs gamma mitjançant tres treballs complementaris que involucren l'estudi simultani d'aquestes fonts en raigs X i raigs gamma de molt alta energia. En primer lloc presentem el descobriment d'emissió en raigs X i raigs gamma de molt alta energia correlades en el temps al sistema LS I +61 303. Aquesta correlació ens indica que l'emissió en les dues bandes pot provenir d'una única població d'electrons, i ho confirmem mitjançant la realització d'un model teòric de radiació que ens permet restringir significativament les propietats físiques de l'emissor no tèrmic de la font. En cas que la font energètica dels sistemes sigui un púlsar, la interacció entre els vents de l'estrella i el púlsar dona lloc a una regió d'interacció on el vent xocat del púlsar accelera partícules i emet des de radio fins a raigs gamma. A l'espectre de raigs X, però, no es detecta l'emissió tèrmica del vent xocat de l'estrella, que s'escalfa fins a desenes de milers de graus. Això ens ha permès estudiar la forma de la regió d'interacció, determinada principalment per la potència del púlsar, i fer un càlcul teòric de l'emissió en raigs X tèrmics. Hem aplicat aquest model al sistema LS 5039 i hem pogut determinar la potència del púlsar, fet important per a la modelització de l'emissió no tèrmica de la font. Finalment, presentem la cerca d'emissió de raigs gamma provinent de sistemes binaris fins ara no detectats. Una campanya simultània en raigs X i raigs gamma ens va permetre seleccionar les dades de molt alta energia del microquàsar Sco X-1 en funció de l'estat d'acreció sobre l'objecte compacte. Tot i no detectar la font en raigs gamma, els límits superiors obtinguts permeten restringir les propietats físiques de Sco X-1 rellevants per a l'emissió en molt alta energia.
Mannings, Vincent. "TeV gamma-ray emission from accreting binary pulsars." Thesis, Durham University, 1990. http://etheses.dur.ac.uk/6297/.
Повний текст джерелаKerschhaggl, Matthias. "The TeV gamma-ray binary PSR B1259-63." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16165.
Повний текст джерелаPSR B1259-63 is a binary system where a 48 ms pulsar orbits a massive Be star. The system exhibits variable, non-thermal radiation around periastron visible from radio to very high energies (VHE; E>100 GeV). This thesis presents VHE data from PSR B1259-63 as taken during the years 2005, 2006 and before as well as shortly after the 2007 periastron passage. These data extend the knowledge of the lightcurve of this object to all phases of the binary orbit. Observations of VHE gamma-rays with the H.E.S.S. telescope array were performed. Gamma-ray events in an energy range of 0.5-70 TeV were recorded. VHE gamma-ray emission from PSR B1259-63 was detected with an overall significance of 9.5 standard deviations using 55 h of exposure, obtained in 2007. The monthly flux of gamma-rays during the observation period was measured, yielding VHE lightcurve data for the early pre-periastron phase of the system for the first time. PSR B1259-63 was also monitored in 2005 and 2006, far from periastron passage, comprising 8.9 h and 7.5 h of exposure, respectively. No significant excess of gamma-rays is seen in those observations. The firm detection of VHE photons emitted at a true anomaly of -0.35 of the pulsar orbit, i.e. already ~50 days prior to the periastron passage, disfavors the stellar disc target scenario as a primary emission mechanism, based on current knowledge about the companion star''s disc inclination, extension, and density profile. In a phenomenological study indirect evidence that PSR B1259-63 could in fact be a periodical VHE emitter is presented using the TeV data discussed in this work. Moreover, model calculations based on inverse compton (IC) scattering of shock accelerated pulsar wind electrons were performed. The model presented accounts for non-radiative losses possibly at work in the region where the pulsar wind is shocked by stellar outflows. The presented results show a peculiar non-radiative cooling profile around periastron dominating the VHE emission.
Aoi, Junichi. "Exploring the Gamma Ray Bursts from GeV-TeV spectra." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142363.
Повний текст джерелаGuillemot, Lucas. "Détections de pulsars milliseconde avec le FERMI Large Area Telescope." Phd thesis, Bordeaux 1, 2009. http://tel.archives-ouvertes.fr/tel-00432706.
Повний текст джерелаGraham, Lilian Joan. "Ultra high energy gamma ray point sources and cosmic ray anisotropy." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/5594/.
Повний текст джерелаHall, C. J. "An imaging high energy gamma ray telescope." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374748.
Повний текст джерелаHungerford, Aimee L. "Gamma-ray lines from asymmetric supernovae." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290114.
Повний текст джерелаZhu, Sylvia Jiechen. "Precursors in gamma-ray bursts observed by Fermi." Thesis, University of Maryland, College Park, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10011526.
Повний текст джерелаGamma-ray bursts (GRBs) are some of the most energetic explosions in the universe. They come from the core collapses of massive stars and the mergers of compact objects, and are observed as bright flashes of gamma rays (prompt emission) followed by long-lived, fading emission (afterglow) across the electromagnetic spectrum. The instruments on the Fermi Gamma-ray Space Telescope provide excellent observations of GRBs across a large energy range. The Gamma-ray Burst Monitor (GBM, 8 keV to 40 MeV) is currently the most prolific detector of GRBs, and the Large Area Telescope (LAT, ∼20 MeV to >300 GeV) has opened up the field of GRB observations to high-energy gamma rays.
In this thesis, I present studies on improving the LAT’s capability to detect GRBs onboard in realtime, and analyses of both a single, extraordinary burst (the record-breaking GRB 130427A) and the population of GBM GRBs with precursors in their lightcurves. In a small fraction of GRBs, a dim peak appears before the much brighter peaks that are normally observed during the prompt emission. I explore whether the properties of GRBs with precursors suggests that precursors have a distinct physical origin from the rest of the prompt emission, and discuss the implications for models of GRB precursor emission.
Samuelsson, Filip. "Multi-messenger emission from gamma-ray bursts." Licentiate thesis, KTH, Partikel- och astropartikelfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-273383.
Повний текст джерела”Multi-messenger astronomy” (mångbudbärarastronomi, fri översättning) är ett väldigt aktuellt område inom astrofysiken just nu. En meddelare är någonting som bär på information. Olika meddelartyper inom astrofysiken är fotoner, kosmisk strålning, neutriner och gravitations vågor. Dessa har alla unik och olika typ av information som kompletterar varandra. Idén bakom multi-meddelare-astronomi är att ju fler olika meddelartyper vi kan upptäcka från samma event, desto mer komplett blir vår fysikaliska tolkning. I denna avhandling studerar jag multi-meddelare emission från gammablixtar (GRBs), de mest ljusstarka företeelser vi känner till i Universum. Mer specifikt, så studerar jag kopplingen mellan GRBs och ultraenergetisk kosmisk strålning (UHECRs). Ursprunget till UHECRs är fortfarande okänt trots långt pågående forskning. GRBs har länge varit en av de mest lovande accelerationskandidaterna men än så länge finns inga fasta bevis. I Paper I och Paper II studerar vi den möjliga GRB-UHECR kopplingen genom att studera den elektromagnetiska strålningen från elektronerna som även de skulle bli accelererade tillsammans med UHECRs. Min slutsats är att strålningen från elektronerna inte matchar observationer från GRBs, vilket talar emot att en majoritet av UHECRs kommer från GRBs.
Carraminana, Alberto. "Very high energy gamma ray astronomy and non pulsating low mass X-ray binaries." Thesis, Durham University, 1991. http://etheses.dur.ac.uk/6241/.
Повний текст джерелаHills, Graeme Lawrence. "The application of polarimetric techniques to gamma ray astronomy." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243187.
Повний текст джерелаLaskar, Tanmoy. "The Diversity and Versatility of Gamma-Ray Bursts." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467212.
Повний текст джерелаAstronomy
Baring, Matthew Geoffrey. "Pair plasmas in astrophysics." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279144.
Повний текст джерелаValan, Vlasta. "Thermal components in the early X-ray afterglow of gamma-ray bursts." Licentiate thesis, KTH, Partikel- och astropartikelfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217103.
Повний текст джерелаQC 20171031
Gil, A. "The development of an imaging low energy gamma ray telescope." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376039.
Повний текст джерелаYearworth, M. "A coded aperture telescope for low energy gamma-ray astronomy." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377798.
Повний текст джерелаSchroedter, Martin. "The very high energy gamma-ray spectra of AGN." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290128.
Повний текст джерелаBorgonovo, Luis. "Spectral and Temporal Studies of Gamma-Ray Bursts." Doctoral thesis, Stockholm : Department of Astronomy, Stockholm University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6793.
Повний текст джерелаZhou, Bei. "Theory and Phenomenology of the Neutrino and Gamma-ray Universe." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595530334835854.
Повний текст джерелаChadwick, Mary Paula. "Very high energy cosmic gamma rays from radio and X-ray pulsars." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6720/.
Повний текст джерелаBradbury, Stella Marie. "Atmospheric Cerenkov astronomy of cataclysmic variables & other potential gamma ray sources." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5632/.
Повний текст джерелаHouston, Brian P. "The role of gamma-ray sources in relation to the observed diffuse emission and the cosmic ray origin problem." Thesis, Durham University, 1985. http://etheses.dur.ac.uk/7236/.
Повний текст джерелаFong, Wen-fai. "Unveiling the Progenitors of Short-duration Gamma-ray Bursts." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11665.
Повний текст джерелаAstronomy
Fegan, Stephen. "A very high energy gamma-ray survey of unidentified EGRET sources." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280605.
Повний текст джерелаOwens, Alan. "High resolution gamma-ray astronomy in the energy range 0.05 to 10 MeV." Thesis, Durham University, 1985. http://etheses.dur.ac.uk/6755/.
Повний текст джерелаDickinson, James Edwin. "A ground based gamma ray telescope of high sensitivity and low energy threshold." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5279/.
Повний текст джерелаRadhi, Fahmi Sha'ban. "Studies of 76Se and 75As by gamma-ray spectroscopy and interacting Boson (-Fermion) models." Thesis, Royal Holloway, University of London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338872.
Повний текст джерелаPalladino, Kimberly Jackson. "The ANITA-I Limit on Gamma Ray Burst Neutrinos." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1253644232.
Повний текст джерелаGrube, Jeffrey. "X-ray and Gamma-ray Study of TeV Blazars with RXTE, XMM-Newton, and the Whipple 10 m Telescope." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485170.
Повний текст джерелаMcCutcheon, Michael Warren. "Search for VHE gamma-ray emission from the globular cluster M13 with Veritas." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107625.
Повний текст джерелаLes amas globulaires, tels que M13, sont des amas d'étoiles très denses et sont connus pour contenir beaucoup plus de pulsars milliseconde par unité de masse que la galaxie dans son ensemble. Ces pulsars sont concentrés dans les régions centrales d'amas globulaires et sont supposés générer des vents relativistes d'électrons. Ces électrons énergétiques peuvent alors interagir avec le champ intense de photons optiques, qui est soutenu par les nombreuses étoiles normales de l'amas, afin de générer des rayons gamma de Très Haute Énergie (THE). Dans la présente thèse, ce modèle d'émission, mis en oeuvre par Bednarek & Sitarek (2007), est décrit et justifié de manière plus détaillée et des données, recueillies à partir d'observations de M13, ont été analysées dans le but de confronter ce modèle. Aucune preuve d'émission des rayons gamma THE de M13 n'a été trouvée. Une limite supérieure intégrale et décorrélée est déterminée, soit 0.306 * 10^−12 cm^−2 s^−1 en dessus de 0.8 TeV, à un niveau de confiance de 95%. Des limites supérieures spectrales sont également déterminées et comparées aux courbes d'émission présentées dans Bednarek & Sitarek (2007). L'examen détaillé des paramètres du modèle révèle que les courbes attendues étaient fondées sur des estimations trop optimistes de plusieurs de ces paramètres. Néanmoins, le modèle peut être lié aux théories existantes des vents des pulsars et, ce faisant, à travers ces observations, on trouve que l'accélération des électrons dans les vents des pulsars millisecondes (en dehors des cylindres lumièriques des pulsars) aux énergies TeV est à exclure, selon des hypothèses auto-cohérentes des propriétés de cette population des pulsars millisecondes.
Knight, Peter John. "The effects of mis-alignment and background noise in a low energy gamma-ray telescope." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303074.
Повний текст джерелаDuncan, Nicole. "Gamma-Ray Observations of Solar Flares with RHESSI Imaging Spectroscopy and the GRIPS instrument." Thesis, University of California, Berkeley, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10620536.
Повний текст джерелаSolar flares can release ~1e33 ergs of power, accelerate particles to relativistic speeds, heat plasma to ~15 million K and catastrophically reorganize 1e5 km long field structures in 100s–1000s of seconds. Magnetic reconnection of large-scale field structures in the corona are thought to power flares, but the precise mechanisms that convert the stored magnetic energy into particle kinetic energy are poorly understood.
Flare spectra in the 20 keV–10 MeV energy range are rich with information that provide a window into the underlying physics of flare particle acceleration. This hard X-ray (HXR)/gamma-ray emission can be used to understand electron and ion dynamics, particle abundances and the ambient plasma conditions in solar flares. Enhanced imaging, spectroscopy and polarimetry of flare emissions in this energy range are needed to address the current era of particle acceleration and transport questions, including: What causes the spatial separation between HXR emission generated by relativistic electrons and the gamma-ray line emission from energetic ions? How anisotropic are the relativistic electrons, and why can they dominate in the corona? How do the compositions of accelerated and ambient material vary with space and time, and why?
The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) instrument, launched in 2002, provided the first combined imaging and high-resolution spectroscopy in the HXR/gamma-ray range. RHESSI's volumes of detailed study on electron-associated emission < 1 MeV is in contrast to comparatively few ion-associated gamma-ray observations. Over the past two solar cycles RHESSI has imaged only five flares at the 2.2 MeV neutron-capture line and has been able to resolve ion lines in ~30 events. My research aims to expand this small set gamma-ray flare observations by (1) using new techniques to study flares obscured by high-background counts in the existing RHESSI dataset and (2) providing new observations through the development and flight of the Gamma-Ray Imager/Polarimeter for Solar Flares (GRIPS) instrument.
Larsson, Josefin Boel Herta. "Black holes in high-energy astrophysics : active galactic nuclei and gamma-ray bursts." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612515.
Повний текст джерелаMorgan, Adam Nolan. "Classification, Follow-Up, and Analysis of Gamma-Ray Bursts and their Early-Time Near-Infrared/Optical Afterglows." Thesis, University of California, Berkeley, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3739716.
Повний текст джерелаIn the study of astronomical transients, deriving knowledge from discovery is a multifaceted process that includes real-time classification to identify new events of interest, deep, multi-wavelength follow-up of individual events, and the global analysis of multi-event catalogs. Here we present a body of work encompassing each of these steps as applied to the study of gamma-ray bursts (GRBs). First, we present our work on utilizing machine-learning algorithms on early-time metrics from the Swift satellite to inform the resource allocation of follow-up telescopes in order to optimize time spent on high-redshift GRB candidates. Next, we show broadband observations and analysis of the early-time afterglow of GRB 120119A, utilizing data obtained with a dozen telescope facilities both in space and on the ground. This event exhibits extreme red-to-blue color change in the first few minutes after the trigger at levels unseen in prior afterglows, and our model fits of this phenomenon reveal the best support yet for the direct detection of dust destruction in the local environment of a GRB. Finally, we present results from the PAIRITEL early-time near-infrared (NIR) afterglow catalog. The 1.3 meter PAIRITEL has autonomously observed 14 GRBs in under 3 minutes after the burst, yielding a homogenous sample of early-time JHKs light curves. Our analysis of these events provides constraints on the early-time NIR GRB afterglow luminosity function and gives insight into the importance of dust extinction in the suppression of some optical afterglows.
Su, Meng. "Discovery of Giant Gamma-ray Bubbles in the Milky Way." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10429.
Повний текст джерелаAstronomy
Vitale, Vincenzo. "Search for multi-TeV gamma ray emission from the SN1006 remnant with the HEGRA CT1 telescope." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972197214.
Повний текст джерелаBeckmann, Volker. "Unification of Active Galactic Nuclei at X-rays and soft gamma-rays." Habilitation à diriger des recherches, Université Paris-Diderot - Paris VII, 2010. http://tel.archives-ouvertes.fr/tel-00601042.
Повний текст джерелаThe study of the evolutionary behaviour of X-ray selected blazars (Beckmann & Wolter 2001; Beckmann et al. 2002, 2003b; Beckmann 2003) shows that their evolution is not as strongly negative as indicated by previous studies. The overall luminosity function is consistent with no evolution in the 0.1−2.4 keV band as seen by ROSAT/PSPC. There is still a difference compared to the luminosity function of FSRQ and LBL, which seem to show a positive evolution, indicating that they have been more luminous and/or numerous at cosmological distances. We indicated a scenario in order to explain this discrepancy, in which the high luminous FSRQ develop into the fainter LBL and finally into the BL Lac objects with high frequency peaks in their spectral energy distribution but overall low bolometric luminosity.
Studying the variability pattern of hard X-ray selected Seyfert galaxies, we actually found differences between type 1 and type 2 objects, in the sense that type 2 seemed to be more variable (Beckmann et al. 2007a). This breaking of the unified model is caused by the different average luminosity of the absorbed and unabsorbed sources, as discussed in Sect. 4.7.3. This can be explained by a larger inner disk radius when the AGN core is most active (the so-called receding disc model).
The work on the sample characteristics of hard X-ray detected AGN also led to the proof that the average intrinsic spectra of type 1 and type 2 objects are the same when reflection processes are taken into account (Beckmann et al. 2009d). This also explains why in the past Seyfert 2 objects were seen to have harder X-ray spectra than Seyfert 1, as the stronger reflection hump in the type 2 objects makes the spectra appear to be flatter, although the underlying continuum is the same.
Further strong evidence for the unification scheme comes from the observation of a fundamental plane which connects type 1 and type 2 objects smoothly (Beckmann et al. 2009d). In addition, in the case of the Seyfert 1.9 galaxy MCG-05-23-016 I showed that the spectral energy distribution of this source and its accretion rate is similar to that of a Galactic binary (Beckmann et al. 2008a).
Throughout the studies I have shown that the intrinsic spectral shape appears to be very stable on weeks to year time scale (Beckmann et al. 2004d, 2005b, 2007b, 2008a). This implies that the overall geometry of the AGN over these time scales did not change dramatically. The variations in intensity can then be explained in two ways: either the amount of material emitting the hard X-rays varies, or the amount of plasma visible to the observer varied, e.g. through different orientation of the disk with respect to the observer. In an upcoming paper we will show though, that NGC 4151 indeed also shows different spectral states, similar to the low-hard versus high-soft spectra in Galactic black hole binaries (Lubinski et al. 2010). A similar result seems to emerge from our INTEGRAL studies on NGC 2110 (Beckmann & Do Cao 2011). For INTEGRAL's AO-8 I have submitted a proposal in order to study spectral states in the Seyfert 2 galaxy NGC 2992, which seems to show a state change over the past 5 years as seen in Swift/BAT longterm monitoring.
The work on the luminosity function of AGN at hardest X-rays (Beckmann et al. 2006d) had a large impact on our understanding of the cosmic X-ray background. As this was the first study of its kind, it showed for the first time that indeed the fraction of highly obscured Compton thick AGN is much lower than expected before the launch of INTEGRAL and Swift. The X-ray luminosity function we revealed is indeed not consistent with the source population seen by INTEGRAL (Beckmann et al. 2006a, 2009d; Sazonov et al. 2007) and Swift (Tueller et al. 2008) being the only contributors to the cosmic hard X-ray background. Thus other sources outside the parameter space observable by these missions have to contribute significantly to the cosmic X-ray background. Our work on the luminosity function triggered several other studies on this issue. The subsequent derived luminosity functions by other groups (Sazonov et al. 2007; Tueller et al. 2008; Paltani et al. 2008) are consistent with our findings.
This also gave rise to an increased interest in the exact shape of the Cosmic X-ray background around its peak at 30 keV, triggering several attempts to a new measurement. Background studies were presented based on a Earth-occultation observation by INTEGRAL (Churazov et al. 2007, 2008; Türler et al. 2010) and by Swift (Ajello et al. 2008).
The understanding of the emission processes in AGN requires knowledge over a wide range of the spectral energy distribution (SED). In studies using CGRO/EGRET and Fermi/LAT data I derived the SED for blazars and non-blazars towards the gamma-ray range (Beckmann 2003; Beckmann et al. 2004b, 2010b). The work on the LAT data not only presented the gamma-ray detection of five gamma-ray blazars (QSO B0836+710, RX J1111.5+3452, H 1426+428, RX J1924.8-2914, and PKS 2149-306) for the first time, but also showed the potential in the combination of INTEGRAL and Fermi data. In the case of Cen A I derived the total energy output of the inverse Compton component based on the combined LAT, ISGRI, and JEM-X data, showing evidence for a spectral break at several hundred keV (Beckmann et al. 2010b).
In addition I successfully showed that gamma-ray blazars can be predicted through the study of their synchrotron branch at energies below 2 keV (Beckmann 2003 and this work).
Contributions of mine to research in fields other than AGN include the study of INTEGRAL detected gamma-ray bursts (e.g. Beckmann et al. 2003a, 2004a, 2008b, 2009a). Here and in collaboration with other colleagues I showed the potential of INTEGRAL data on GRB research. In the field of Galactic X-ray binaries I published one of the first Swift results on a newly discovered highly absorbed HMXB, IGR J16283-4838 (Beckmann et al. 2005a, 2006b). I also contributed significantly to analysis of many other Galactic sources, as shown in Section 4.6.1.
Doherty, Daniel Thomas. "Experimental studies for explosive nuclear astrophysics." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/18022.
Повний текст джерелаAbeysekara, A. U., S. Archambault, A. Archer, W. Benbow, R. Bird, M. Buchovecky, J. H. Buckley, et al. "A SEARCH FOR SPECTRAL HYSTERESIS AND ENERGY-DEPENDENT TIME LAGS FROM X-RAY AND TeV GAMMA-RAY OBSERVATIONS OF Mrk 421." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622634.
Повний текст джерелаLemoine-Goumard, Marianne. "Stéréoscopie de gerbes de gamma avec les télescopes H.E.S.S.: premières images de vestiges de supernovae au TeV." Phd thesis, Ecole Polytechnique X, 2006. http://tel.archives-ouvertes.fr/tel-00088492.
Повний текст джерелаCette thèse présente une nouvelle méthode de reconstruction des gerbes électromagnétiques qui utilise l'ensemble de l'information fournie par la stéréoscopie et la haute définition des caméras de H.E.S.S.. Cette nouvelle méthode permet d'obtenir une résolution angulaire meilleure que le dixième de degré, une résolution en énergie de l'ordre de 15% au zénith, ainsi qu'un rejet hadronique très efficace à partir d'une coupure sur la largeur transverse de la gerbe reconstruite, et qui ne dépend d'aucune simulation.
Une nouvelle méthode de soustraction du fond hadronique adaptée à l'étude des sources étendues a aussi été mise en oeuvre. Cette méthode ne fait aucune hypothèse sur la distribution du fond hadronique ni sur le contenu en gamma de la région du ciel étudiée. Elle permet d'obtenir, par un maximum de vraisemblance, deux cartes globales: l'une pour la distribution des gamma dans le champ de vue, et l'autre pour la distribution des hadrons.
Ces deux nouvelles méthodes ont été appliquées à l'analyse des vestiges de supernovae RX J1713.7-3946 et RX J0852.0-4622 (Vela Junior), et ont permis de résoudre leur morphologie pour la première fois dans le domaine gamma. L'étude de ces sources a un objectif fondamental: permettre de savoir si les vestiges de supernovae sont bien des accélérateurs des rayons cosmiques, au moins jusqu'au domaine du genou (5*10^15 eV). Une étude morphologique et spectrale de ces sources conjointement à une comparaison avec un modèle simple des émissions gamma (à partir d'électrons ou de protons accélérés dans les vestiges de supernovae) a permis de contraindre les paramètres des modèles leptoniques. Toutefois, ce modèle n'a pu être exclu. Les différents résultats obtenus sont discutés et comparés au cas d'un troisième vestige de supernova à coquille observé par H.E.S.S. mais non détecté: SN 1006.
Pinzke, Anders. "Gamma-Ray Emission from Galaxy Clusters : DARK MATTER AND COSMIC-RAYS." Doctoral thesis, Stockholms universitet, Fysikum, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-42453.
Повний текст джерелаAt the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted.