Dissertations / Theses on the topic 'Gamma Ray Bursts (GRBs)'
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Nakauchi, Daisuke. "Gamma-Ray Bursts from First Stars and Ultra-Long Gamma-Ray Bursts." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199100.
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Chapman, Robert. "Gamma-ray bursts in the local universe." Thesis, University of Hertfordshire, 2009. http://hdl.handle.net/2299/2809.
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With energy outputs >~10^51 erg in 0.1-1000 seconds, Gamma-ray Bursts (GRBs) are the most powerful events yet observed in the Universe. As such they are potential probes of the very early Universe, back to the era of re-ionisation and the first stars, but at the same time they have been observed to span a wide range in luminosity and redshift from the relatively local Universe (z~0.0085) out to z~6.29. GRBs divide into two classes based primarily on their duration as measured by T90 (the time taken to observe 90% of the total burst fluence). Long bursts (L-GRBs) have T90>~2 seconds, and shorts (S-GRBs) T90<~2 seconds. Though much has been learned regarding long duration GRBs since the first afterglow discovery in 1997 (including their likely association with massive core collapse supernovae), much remains unknown regarding short duration GRBs. In this work, after a brief historical introduction and review, we present analyses of the angular cross-correlation on the sky of short GRBs from the BATSE catalogue with galaxies in the local Universe sampled from the PSCz Redshift Survey and the Third Reference Catalogue of Bright Galaxies (RC3). In particular we show that 20%+/-8% (1 sigma) of all BATSE short duration bursts (localised to 10 degrees or better) show correlation with galaxy samples (morphological T-type<=4) within ~112 Mpc. Our statistics thus provide evidence that a substantial fraction of BATSE short GRBs show a tendency to be associated with large scale structure on the sky traced by a variety of galaxy types. Short GRBs are believed to be produced in the final merger of compact object (neutron star-neutron star or neutron star-black hole) binaries, though other possible progenitors are known to exist. The short initial spike of a giant flare from a Soft Gamma Repeater (SGR) such as the December 27th 2004 event from SGR1806-20 would have been detectable by BATSE as a short GRB if it occurred in a galaxy within ~30-50 Mpc (assuming a distance to SGR1806-20 of 15 kpc). Using the observed luminosities and rates of Galactic SGR giant flares, as well as theoretical predictions for the rate of binary mergers, we investigate the ability of plausible Luminosity Functions (LF), singly and in combination, to reproduce our observed correlations and a cosmological S-GRB population. We find the correlations are best explained by a separate population of lower luminosity S-GRBs, with properties consistent with them being due to giant flares from extra-galactic SGRs. Overall predicted number counts are a good fit to the observed BATSE number counts, and furthermore, the wider redshift distribution is consistent with the early Swift S-GRB redshift distribution. The three closest GRBs which have been observed to date were all long duration bursts, and we have therefore also searched for cross-correlation signals between the BATSE long GRBs and local galaxies. The three nearby bursts shared several similar properties such as being under-luminous, spectrally soft and of low variability. We have therefore also investigated a subset of L-GRBs with light curve properties similar to these known nearby bursts. The whole sample is found to exhibit a correlation level consistent with zero (1 sigma upper limit=10%, equivalent to 144 bursts) out to a radius of ~155 Mpc, but a spectrally soft, low observed fluence and low variability subset shows a correlation level of 28%+/-16% (=50+/-28 bursts) within 155 Mpc. These results are consistent with low-luminosity, low-variability bursts being a separate sub-class of L-GRBs which may be much more prevalent in the local Universe than their high-luminosity, cosmologically distant counterparts. To investigate this further, we once again examined plausible luminosity functions for single and dual high and low luminosity populations, based on observed intrinsic rates from the literature. The local population was once again found only to be produced to a sufficient level (while maintaining consistency with the observed overall number counts) by a separate low luminosity population with intrinsic rates several hundred times greater than their cosmological counterparts. Constraining the models via the Swift overall redshift distribution instead of threshold-adjusted BATSE number counts showed that the dual LF models were able to produce excellent fits to the entire redshift distribution while adequately reproducing a local population. Finally, suggestions are made as to the direction future work may follow in order to build on these initial investigations, as well as to how observations with future missions and detectors such as Fermi (formerly GLAST), Advanced LIGO and LOFAR may shed further light on nearby GRBs.
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Galante, Douglas. "Efeitos astrofísicos e astrobiológicos de Gamma-Ray Bursts." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/14/14131/tde-19062009-014454/.
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O presente trabalho tem o objetivo principal de compreender os possíveis efeitos da radiação energética de um evento de Gamma-Ray Burst (GRB) sobre o meio interestelar no entorno de seu local de geração e em planetas possivelmente iluminados. Gamma-Ray Bursts foram detectados pela primeira vez nos anos 60 e rapidamente atraíram a atenção da comunidade astrofísica, uma vez que as energias emitidas apenas em poderiam alcançar 1054erg, o equivalente a massa de repouso do Sol. Não se conhecia nenhum mecanismo tão eficiente para extrair energia gravitacional para produzir tal evento. Mais tarde, a possibilidade da emissão ser colimada abaixou a energia em para 5x1050erg, mas o mecanismo central de geração ainda não foi completamente desvendado, havendo muito espaço para alternativas exóticas. Estudamos os efeitos de um GRB sobre o meio interestelar, em uma tentativa de distinguir os remanescentes do GRB do gerado por múltiplas supernovas. Usamos argumentos energéticos e sobre a possibilidade de alterações químicas e isotópicas devido a reações fotonucleares. Também trabalhamos com as implicações biológicas da iluminação de planetas por um GRB, concluindo que os efeitos de tais eventos podem afetar seriamente a biosfera de um planeta mesmo a distâncias de ~10kpc.The present work has the main goal of understanding the possible effects of the hard gamma radiation produced during a Gamma-Ray Burst (GRB) event both on the interstellar medium surrounding the source of the burst and on planets possibly illuminated. Gamma-Ray Bursts were first detected on the 60s and quickly have attracted the attention of the astrophysical community, since the energies emitted just in could reach 1054erg, the rest mass of the Sun. No mechanism was known to be so efficient in extracting gravitational energy to produce such emission. Later on, the possibility of the emission being collimated has lowered the energy of the to 5x1051erg, but the central engine has not yet been completely understood, and there is still ample room for exotic alternatives. We have studied the effects of GRB on the ISM, in an attempt to distinguish the candidates of GRB remnants from those generated by multiple supernovae. We have used both energetic arguments and the possibility of chemical alterations due to photonuclear reactions. We have also worked on the biological implications of the illumination of planets by a GRB, concluding that the effects of such event could seriously harm the biosphere of a planet even at distances of ~10kpc.
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Olivo, Martino. "Neutrino emission from high-energy component gamma-ray bursts." Licentiate thesis, Uppsala universitet, Högenergifysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132961.
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Gamma-ray bursts (GRBs) are brief and sudden explosions radiating most of their energy in the soft γ-ray band ( 100 keV). In the context of multimessenger astroparticle physics recent observations of GRBs provide an excellent benchmark for testing theoretical models of high energy emission mechanisms. Acceleration of hadrons in the engine is expected to produce high energy neutrinos and gamma-rays simultaneously via π±/π0 decays, thus reinforcing the motivation for coincident searches in km3 neutrino telescopes. The Waxman-Bachall spectra and the corresponding expected neutrino rates in IceCube are derived here for GRB090510 amd GRB090902B recently detected by the Fermi Large Area Telescope. The implications of the significant detection of deviations from the Band function fit in photon spectra and a model that explains these extra-components in terms of π0-decay photons are presented here and the relevance to neutrino astronomy is shown.
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Casey, James David. "Search for high energy GRB neutrinos in IceCube." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53839.
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The IceCube Neutrino Observatory has reported the observation of 35 neutrino events above 30 TeV with evidence for an astrophysical neutrino flux using data collected from May 2010 to May 2013. These events provide the first high-energy astrophysical neutrino flux ever observed. The sources of these events are currently unknown. IceCube has looked for correlations between these events and a list of TeV photon sources including a catalog of 36 galactic sources and 42 extragalactic sources, correlations with the galactic plane and center, and spatial and temporal clustering. These searches have shown no significant correlations. The isotropic distribution of the event directions gives indications that the events could be extragalactic in nature and therefore may originate in the same processes that generate ultra-high-energy cosmic rays (UHECRs). The sources of these UHECRs are still unknown; however, gamma-ray bursts (GRBs) have been proposed as one possible source class. By determining the source of these high-energy neutrinos, it may be possible to determine the sources of UHECRs as well. This study is a search for directional and temporal correlation between 856 GRBs and the astrophysical neutrino flux observed by IceCube. Nearly 10,000 expanding time windows centered on the earliest reported time of the burst were examined. The time windows start at ±10 s and extend to ±15 days. We find no evidence of correlations for these time windows and set an upper limit on the fraction of the astrophysical flux that can be attributed to the observed GRBs as a function of the time window. GRBs can contribute at most 12% of the astrophysical neutrino flux if the neutrino-GRB correlation time is less than ≈20 hours, and no more than 38% of the astrophysical neutrino flux can be attributed to the known GRBs at time scales up to 15 days. We conclude that GRBs observable by satellites are not solely responsible for IceCube’s astrophysical neutrino flux, even if very long correlation time scales are assumed.
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Harstad, Emelie. "A Targeted LIGO-Virgo Search for Gravitational Waves Associated with Gamma-Ray Bursts Using Low-Threshold Swift GRB Triggers." Thesis, University of Oregon, 2013. http://hdl.handle.net/1794/13003.
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Gamma-ray bursts (GRBs) are short, intense flashes of 0.1-1 MeV electromagnetic radiation that are routinely observed by Earth orbiting satellites. The sources of GRBs are known to be extragalacitic and located at cosmological distances. Due to the extremely high isotropic equivalent energies of GRBs, which are on the order of Eiso~1054 erg, the gamma-ray emission is believed to be collimated, making them observable only when they are directed towards Earth. The favored progenitor models of GRBs are also believed to emit gravitational waves that would be observable by the current generation of ground-based interferometric gravitational wave detectors. The LIGO (Laser Interferometer Gravitational-Wave Observatory) and Virgo instruments operated near design sensitivity and collected more than a year of triple coincident data during the S5/VSR1 science run, which spanned the two year interval between November 2005 and October 2007. During this time, GRB detections were being made by the NASA/Goddard Swift Burst Alert Telescope at a rate of approximately 0.3 per day, producing a collection of triggers that has since been used in a coincident GRB-GW burst search with data from the LIGO-Virgo interferometer network. This dissertation describes the search for gravitational waves using the times and locations of 123 below-threshold potential GRB triggers from Swift over the same time period. Although most of the below-threshold triggers are likely false alarms, there is reason to believe that some are the result of actual faintly-observed GRB events. Recent GRB observations indicate that the local rate of low-luminosity GRBs is much higher than previously believed. This result, combined with the possibility of discovering a rare nearby GRB event accompanied by gravitational waves, is what motivates this search. The analysis results indicate no evidence for gravitational waves associated with any of the below-threshold triggers. A median distance lower limit of ~16 Mpc was derived for a typical neutron star-black hole coalescence progenitor assumption.
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Sears, Huei M. "Investigation of the Mass-Metallicity Relation of GRB Host Galaxies at z ~ 4.7." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1597762492071921.
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Kuehn, Frederick Gabriel. "Finding Gamma Ray Bursts at High Energies and Testing the Constancy of the Speed of Light." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1214582047.
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Bardho, Onelda. "Comprendre la physique des sursauts gamma grâce aux corrélations dans les données." Thesis, Nice, 2016. http://www.theses.fr/2016NICE4004/document.
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Les Sursauts de Rayonnement Gamma (GRBs) sont des flashs émanant du cosmos qui sont classés en deux groupes : les longs/doux et les courts/durs. Le lancement du satellite Swift a ouvert une nouvelle ère dans la recherche sur les GRBs. Cette thèse présente une étude détaillée du GRB 141221A qui montre une forte et inhabituelle hausse des valeurs des courbes de lumière dans le domaine optique lors de l'émission rémanente alors que dans le domaine des rayons X ces valeurs sont plus normales. GRB 141221A est un des GRBs qui mettent à l'épreuve les modèles car il exclut tout vent stellaire du progéniteur. Un regroupement des courbes de lumière dans le domaine X lors de l'émission rémanente GRBs a été observé avant le lancement de Swift. Cette classification a été débattue après le lancement de Swift. Nous avons construit un échantillon de 254 GRBs qui montre un éparpillement des distributions du flux à un jour. Cette distribution a été normalisée avec un décalage vers le rouge de 1. Nous avons investigué ce problème selon trois directions: un problème instrumental, un problème de calibration des données ou l'absence de regroupement. Coté instrument, le problème pourrait être observationnel, nous avons en effet observé des effets saisonniers durant les solstices et les équinoxes. Coté calibration des données, un tel problème pourrait avoir une influence sur les résultats de l'étude. La comparaison entre analyse manuelle et automatique des données telle que disponible sur le dépôt Swift-XRT montre de sérieux aléas sur les résultats. Les cas où l'analyse manuelle est judicieuse sont exposés. La dernière possibilité de l'absence de regroupement pourrait être un effet de sélectionGRBs are ashes of gamma-rays coming from cosmos. They are one of the most mysteriousevents we have been able to observe since their discovery. GRBs are classified into two groups: long/soft GRBs and short/hard GRBs. Their emission mechanism consists of two phases: prompt emission and afterglow emission. The launch of the Swift satellite opened a New Era in the GRBs research. Swift is able to provide accurate position for more GRBs than previous missions, thanks to its fast capabilities of slewing. Furthermore, the Swift shows that GRBs have a canonical behaviour for the X-ray afterglow light curves. The data analysis process remains the key point of GRBs studies. I present a detailed study of the peculiar GRB 141221A at different wavelengths. GRB 141221A shows an unusual steep rise in the optical light curve of the afterglow. The broad band spectral energy distribution, taken near the maximum of the optical emission, presents either a thermal component or a behaviourbreak. This burst displays unusual feature in the optical band, whereas the X-ray data is more common. GRB 141221A is one of the challenging bursts that excludes a stellar wind from the progenitor of the GRBs. A clustering in the X-ray afterglow light curves was observed before the launch of the Swift satellite. This feature has been debated after the launch of the Swift. We have built a sample which consists of 254 GRBs that shows a scattering of the data for the flux distribution at one day. This distribution was investigated with a normalization of light curves at redshift one. We have investigated the problem into three different directions
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Laskar, Tanmoy, Kate D. Alexander, Edo Berger, Wen-fai Fong, Raffaella Margutti, Isaac Shivvers, Peter K. G. Williams, et al. "A REVERSE SHOCK IN GRB 160509A." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/624020.
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We present the second multi-frequency radio detection of a reverse shock in a gamma-ray burst. By combining our extensive radio observations of the Fermi-Large Area Telescope gamma-ray burst 160509A at z - 1.17 up to 20 days after the burst with Swift X-ray observations and ground-based optical and near-infrared data, we show that the afterglow emission comprises distinct reverse shock and forward shock contributions: the reverse shock emission dominates in the radio band at. less than or similar to 10 days, while the forward shock emission dominates in the X-ray, optical, and near-infrared bands. Through multi-wavelength modeling, we determine a circumburst density of n(0) approximate to 10(-3) cm(-3), supporting our previous suggestion that a low- density circumburst environment is conducive to the production of long-lasting reverse shock radiation in the radio band. We infer the presence of a large excess X-ray absorption column, N-H approximate to 1.5. x 10(22) cm(-2), and a high rest-frame optical extinction, A(V) approximate to 3.4 mag. We identify a jet break in the X-ray light curve at t(jet) approximate to 6 days, and thus derive a jet opening angle of theta(jet) approximate to 4 degrees, yielding a beaming-corrected kinetic energy and radiated gamma-ray energy of E-K approximate to 4 x 10(50) erg and E-gamma approximate to 1.3 x 10(51) erg ( 1-10(4) keV, rest frame), respectively. Consistency arguments connecting the forward shocks and reverse shocks suggest a deceleration time of t(dec) approximate to 460 s approximate to T-90, a Lorentz factor of Gamma( t(dec)) approximate to 330, and a reverse-shock-to-forward-shock fractional magnetic energy density ratio of R-B equivalent to is an element of(B, RS)/is an element of(B, FS) approximate to 8. Our study highlights the power of rapid-response radio observations in the study of the properties and dynamics of gamma-ray burst ejecta.
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Drenkhahn, Georg. "Magnetically powered gamma-ray bursts." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/91783.
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Rau, Arne. "Gamma-ray bursts a population study /." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978976266.
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Lundman, Christoffer. "Photospheric emission in gamma-ray bursts." Licentiate thesis, KTH, Partikel- och astropartikelfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-101913.
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This thesis considers emission from gamma-ray bursts (GRBs), the most powerful explosions known in the Universe. Most GRBs are likely associated with the final stages of stellar evolution, where the core of a massive star collapses, and gives birth to a highly compact object such as a neutron star or black hole. The wide energy range of the Fermi Gamma-ray Space Telescope allows for unprecedented studies of GRBs. Fermi data is used to study the emission released at the photosphere of the relativistic outow ejected from the central compact object. The thesis present studies of two of the strongest GRBs ever detected; GRB 090902B (Papers I, II) and GRB 110721A (Paper III). Photospheric emission is identied and its properties are studied for both GRBs. For the first time, observational evidence is found for spectral broadening of photospheric emission. Motivated by these results, possible mechanisms to make the emission from the photosphere appear broader than the Planck spectrum are examined. Two separate theoretical explanations are presented. Apart from the possibility of energy dissipation below the photosphere (Paper II), geometrical effects in outflows with angle dependent properties is shown to significantly broaden the photospheric spectrum (Paper IV). Most importantly, the observed spectrum below the peak energy may become significantly softer inthe latter case. This thesis thus concludes that photospheric emission in GRBs may be more common than previously thought. This is because the emission spectrum from the jet photosphere does not necessarily need to be a Planck function. On the contrary it is shown that broader and/or multicomponent spectra naturally arise, consistent with what is generally observed. In particular, the thesis presents a new mechanism for spectral broadening due to geometrical effects, which must be taken into consideration in the study of GRB emission.QC 20120907
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Williamson, Andrew Robert. "Gravitational waves with gamma-ray bursts." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/96479/.
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Gravitational waves have now twice been detected emanating from the merging of binary black hole systems. In this thesis we detail the methods used to search for binary merger gravitational wave signals associated with short gamma-ray bursts, focusing on systems that include at least one neutron star. We first cover the background theory behind gravitational wave emission, the means of detection via interferometry, and the types of astrophysical sources that could be detected now or in the near future. We follow this with a review of gamma-ray burst theory and observations, focusing in particular those bursts with short durations. These are likely to be caused by the mergers of binaries that include a neutron star and a black hole, or two neutron stars - events of great interest to gravitational wave astronomy. We then discuss the methods used to search gravitational wave data in a targeted way, using the prior observation of a short gamma-ray bursts to focus the analysis and improve the chances of making a detection. We also summarise early searches of this kind and present the results of a search carried out on LIGO and Virgo data spanning 2005-2010, targeting short gamma-ray bursts detected by the InterPlanetary Network. We then turn our attention to the current, second generation of gravitational wave detectors. We present a detailed calculation of the prospects of success for the targeted short gamma-ray burst search technique, and find that we might reasonably expect to make up to a few detections per year around the turn of the decade. We then outline a new search structure for use during the second generation of detectors, and an astrophysical event alert system for the control rooms of gravitational wave observatories. We end with a presentation of the results of the new and improved search carried out during the first observing run of Advanced LIGO.
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Ramirez-Ruiz, Jorge Enrico. "A theory of gamma-ray bursts." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619958.
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Levan, Andrew J. "Gamma-ray bursts and their environments." Thesis, University of Leicester, 2005. http://hdl.handle.net/2381/30687.
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Gamma-ray Bursts (GRBs) are the most energetic explosive events known in the universe and manifest themselves as a brief flash of high energy (X-ray and gamma-ray) photons lasting for a few seconds. Subsequent to the prompt gamma-ray flash, longer lasting afterglow emission is seen at X-ray, optical and radio wavelengths. These afterglows have allowed the precise positioning of GRBs on the sky, redshift measurements and the identification of host galaxies. They have also demonstrated that GRBs with durations of > 2s are relativistically beamed jetted outflows associated with the collapse of massive stars in a type Ic supernova.;In this thesis I present observations of several GRB afterglows and a large survey of GRB host galaxies. The goal of the research is to better understand the connection between GRBs, stellar collapse and star formation. The work presented here demonstrates that GRBs are a diverse population, showing that the supernovae associated with GRBs can span an order of magnitude in absolute luminosity, and are sometimes invisible, even in deep searches.;This work has also located the first good example of a GRB which is heavily optically extinguished due to the presence of dust in its host galaxy, demonstrating that dust extinction can account for a fraction of the "dark bursts", which are invisible at optical wavelengths.;Finally, the connection of GRBs to star formation at large is addressed via a comparison of the properties of the host galaxies of GRBs and core collapse supernovae. I show that GRBs are much more concentrated on their host galaxy light than supernovae and, furthermore, have host galaxies significantly smaller and less luminous that those of SN. Jointly these results indicate that GRBs may originate in low metallicity environments, and come from the most massive stars. This result may have important consequence for the use of GRBs as probes of high redshift star formation.
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Yamazaki, Ryo. "Toward the Unified Theory of Long and Short Gamma-Ray Bursts, X-Ray Rich Gamma-Ray Bursts, and X-Ray Flashes." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147812.
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Alexander, K. D., T. Laskar, E. Berger, C. Guidorzi, S. Dichiara, W. Fong, A. Gomboc, et al. "A Reverse Shock and Unusual Radio Properties in GRB 160625B." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/626042.
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We present multi-wavelength observations and modeling of the exceptionally bright long gamma-ray burst GRB 160625B. The optical and X-ray data are well fit by synchrotron emission from a collimated blastwave with an opening angle of theta(j) approximate to 3 degrees.6 and kinetic energy of E-K approximate to 2 x 10(51) erg, propagating into a low-density (n approximate to 5 x 10(-5) cm(-3)) medium with a uniform profile. The forward shock is sub-dominant in the radio band; instead, the radio emission is dominated by two additional components. The first component is consistent with emission from a reverse shock, indicating an initial Lorentz factor of Gamma(0) greater than or similar to 100 and an ejecta magnetization of R-B approximate to 1-100. The second component exhibits peculiar spectral and temporal evolution and is most likely the result of scattering of the radio emission by the turbulent Milky Way interstellar medium (ISM). Such scattering is expected in any sufficiently compact extragalactic source and has been seen in GRBs before, but the large amplitude and long duration of the variability seen here are qualitatively more similar to extreme scattering events previously observed in quasars, rather than normal interstellar scintillation effects. High-cadence, broadband radio observations of future GRBs are needed to fully characterize such effects, which can sensitively probe the properties of the ISM and must be taken into account before variability intrinsic to the GRB can be interpreted correctly.
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Predoi, Valeriu. "Gravitational waves and short gamma ray bursts." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/39987/.
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Short hard gamma-ray bursts (GRB) are believed to be produced by compact binary coalescences (CBC) { either double neutron stars or neutron star{black hole binaries. The same source is expected to emit strong gravitational radiation, detectable with existing and planned gravitational wave observatories. The focus of this work is to describe a series of searches for gravitational waves (GW) from compact binary coalescence (CBC) events triggered by short gamma-ray burst detections. Specifically, we will present the motivation, frameworks, implementations and results of searches for GW associated with short gamma-ray bursts detected by Swift, Fermi{GBM and the InterPlanetary Network (IPN) gamma-ray detectors. We will begin by presenting the main concepts that lay the foundation of gravitational waves emission, as they are formulated in the theory of General Relativity; we will also brie y describe the operational principles of GW detectors, together with explaining the main challenges that the GW detection process is faced with. Further, we will motivate the use of observations in the electromagnetic (EM) band as triggers for GW searches, with an emphasis on possible EM signals from CBC events. We will briefly present the data analysis techniques including concepts as matched{filtering through a collection of theoretical GW waveforms, signal{to{ noise ratio, coincident and coherent analysis approaches, signal{based veto tests and detection candidates' ranking. We will use two different GW{GRB search examples to illustrate the use of the existing coincident and coherent analysis methods. We will also present a series of techniques meant to improve the sensitivity of existing GW triggered searches. These include shifting background data in time in order to obtain extended coincident data and setting a prior on the GRB inclination angle, in accordance with astrophysical observations, in order to restrict the searched parameter space. We will describe the GW data analysis and present results from a GW search around 12 short gamma-ray bursts detected by the InterPlanetary Network (IPN) between 2006 and 2007. The IPN{detected bursts usually have extended localization error boxes and a search for GW was performed at different sky locations across these error regions. Since no GW detection was made, we set upper limits on the distances to the GRB progenitors; we briefly discuss the implications that two IPN GRBs error regions overlap two nearby galaxies.
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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.
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Multi-messenger astronomy is a very hot topic in the astrophysical community. A messenger is something that carries information. Different astrophysical messenger types are photons, cosmic rays, neutrinos, and gravitational waves. They all carry unique and complementary information to one another. The idea with multi-messenger astronomy is that the more different types of messengers one can obtain from the same event, the more complete the physical picture becomes. In this thesis I study the multi-messenger emission from gamma-ray bursts (GRBs), the most luminous events known in the Universe. Specifically, I study the connection of GRBs to extremely energetic particles called ultra-high-energy cosmic rays (UHECRs). UHECRs have unknown origin despite extensive research. GRBs have long been one of the best candidates for the acceleration of these particles but a firm connection is yet to be made. In Paper I and Paper II, we study the possible GRB-UHECR connection by looking at the electromagnetic radiation from electrons that would also be accelerated together with the UHECR. My conclusion is that the signal from these electrons does not match current GRB observation, disfavoring that a majority of UHECRs comes from GRBs.”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.
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Ukwatta, T. N., K. Hurley, J. H. MacGibbon, D. S. Svinkin, R. L. Aptekar, S. V. Golenetskii, D. D. Frederiks, et al. "INVESTIGATION OF PRIMORDIAL BLACK HOLE BURSTS USING INTERPLANETARY NETWORK GAMMA-RAY BURSTS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621378.
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The detection of a gamma-ray burst (GRB) in the solar neighborhood would have very important implications for GRB phenomenology. The leading theories for cosmological GRBs would not be able to explain such events. The final bursts of evaporating primordial black holes (PBHs), however, would be a natural explanation for local GRBs. We present a novel technique that can constrain the distance to GRBs using detections from widely separated, non-imaging spacecraft. This method can determine the actual distance to the burst if it is local. We applied this method to constrain distances to a sample of 36 short-duration GRBs detected by the Interplanetary Network (IPN) that show observational properties that are expected from PBH evaporations. These bursts have minimum possible distances in the 10(13)-10(18) cm (7-10(5) au) range, which are consistent with the expected PBH energetics and with a possible origin in the solar neighborhood, although none of the bursts can be unambiguously demonstrated to be local. Assuming that these bursts are real PBH events, we estimate lower limits on the PBH burst evaporation rate in the solar neighborhood.
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Guthmann, Axel W. "Teilchenbeschleunigung an ultrarelativistischen Stossfronten und Gamma-Ray-Bursts." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=967133750.
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Borgonovo, 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.
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Schady, Patricia. "Prompt observations of Gamma-Ray Bursts with Swift." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1445047/.
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This thesis uses early-time and simultaneous data from all three instruments on-board Swift to explore how the conditions of long Gamma-Ray Bursts (GRBs) and their environment affect their observed prompt and afterglow properties. I firstly analyse two long GRBs with properties that distinguish them from the more standard class of long GRB XRF 050406 and GRB 061007. The X-Ray Flash XRF 050406 is a class of GRB with softer prompt emission spectra than is typically observed. At the time, Swift UVOT observations of XRF 050406 were the earliest to be taken of an XRF optical counterpart, and the temporal and spectral Swift multi-wavelength data indicate that the bursts' softness is due to a geometrical effect where the GRB is observed off-axis. GRB 061007 is the brightest GRB to be detected by Swift and is accompanied by an exceptionally luminous afterglow that had a V-band magnitude < 11.1 at 80 s after the prompt emission. Although several properties of GRB 061007 axe comparable to that of more standard GRBs, the brightness and the similarity in the decay rate of the X-ray, UV/optical and 7-ray emission from 100 s after the trigger require either an excessively large kinetic energy or highly collimated outflow. To study GRB local environments, I analyse the X-ray and UV/optical spectral energy distributions of seven GRBs, and determine the column density and dust extinction in the GRB local environment. Using the SMC, LMC and Milky Way extinction curves to model the host galaxy dust, I find the SMC model to provide the best fit to the majority of the sample, indicating that the local environments of long GRBs are characteristic of irregular, low metallicity galaxies. I investigate the factors that contribute to the extinction and absorption in GRB afterglows, and the implications for the host galaxy properties.
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Zhu, Sylvia Jiechen. "Precursors in gamma-ray bursts observed by Fermi." Thesis, University of Maryland, College Park, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10011526.
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Gamma-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.
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Tunnicliffe, Rachel L. "Constraining the progenitors of short gamma-ray bursts." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/60503/.
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So far the progenitors of short γ-ray bursts (SGRBs) have proved elusive. Their presence within both old and young environments and their bias against starforming regions provide tantalising evidence of a neutron star binary or neutron star - black hole merger origin. Within this thesis we study an array of characteristics of the population of SGRBs focussing in particular on their host environments and afterglow properties in the optical and X-ray bands. In particular we consider a set of SGRBs with no detectable host galaxy to deep limits and no clear host in the field from probabilistic arguments. These GRBs either represent a population at high redshift or with high offsets from low redshift hosts. Comparing the offsets of these GRBs from their potential hosts with random positions on the sky we find they are somewhat closer than expected, suggesting these GRBs are more likely to have been kicked from relatively local hosts. We also consider the issue of classification, given suggestions that the often used two second duration divide for SGRBs may produce a sample with a high contamination from collapsar objects or potentially a suggested third class of intermediate objects. We look at a sample of optically-detected SGRBs below the nominal two second divide and go on to consider properties of a larger sample of GRBs comparing varying duration bins. From constructed optical lightcurves and SEDs, we constrain the presence of extinction, jet breaks, supernovae and kilonovae. Though there is a suggestion that such a sample would be 40% contaminated from collapsar objects we find, from supernova constraints combined with duration and spectral hardness fits from Bromberg et al. (2013) that only 22% of objects in our sample could have been collapsars. The optical constraints placed on a kilonova (an r-process transient associated with neutron star mergers), suggest this transient is fainter than has sometimes been predicted but is consistent when considering additional opacities from the rprocess material which could cause strong reddening to the infra-red. Finally, we do not find evidence for a distinct class of intermediate GRBs, though there are likely additional progenitors which create GRB-like objects. At the intermediate duration we do find two unusual individual events not typical of LGRBs: GRBs 100816A and 060505. We find that GRB100816A is most likely a mis-classified SGRB, from its position within its host and the constraint on any associated supernova.
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Gompertz, Benjamin Paul. "The progenitors of extended emission gamma-ray bursts." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/32517.
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Gamma-ray bursts (GRBs) are the most luminous transient events in the Universe, and as such are associated with some of the most extreme processes in nature. They come in two types: long and short, nominally separated either side of a two second divide in gamma-ray emission duration. The short class (those with durations of less than two seconds) are believed to be due to the merger of two compact objects, most likely neutron stars. Within this population, a small subsection exhibit an apparent extra high-energy emission feature, which rises to prominence several seconds after the initial emission event. These are the extended emission (EE) bursts. This thesis investigates the progenitors of the EE sample, including what drives them, and where they fit in the broader context of short GRBs. The science chapters outline a rigorous test of the magnetar model, in which the compact object merger results in a massive, rapidly-rotating neutron star with an extremely strong magnetic field. The motivation for this central engine is the late-time plateaux seen in some short and EE GRBs, which can be interpreted as energy injection from a long-lived central engine, in this case from the magnetar as it loses angular momentum along open field lines. Chapter 2 addresses the energy budget of such a system, including whether the EE component is consistent with the rotational energy reservoir of a millisecond neutron star, and the implications the model has for the physical properties of the underlying magnetar. Chapter 3 proposes a potential mechanism by which EE may arise, and how both classes may be born within the framework of a single central engine. Chapter 4 addresses the broadband signature of both short and EE GRBs, and provides some observational tests that can be used to either support or contradict the model.
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Laskar, Tanmoy. "The Diversity and Versatility of Gamma-Ray Bursts." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467212.
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Gamma-ray bursts (GRBs) are the most energetic explosions in the Universe, thus providing a unique laboratory for the study of extreme astrophysical processes. In parallel, their large luminosity makes GRBs a premier probe of the early Universe. My thesis has explored and exploited both aspects of GRB science by addressing the following fundamental open questions: 1) what is the nature of the GRB ejecta?, 2) how does the GRB progenitor population evolve with redshift, and 3) how can GRBs be used to probe the high-redshift Universe? To answer these questions, I present the first multi-wavelength detection and modeling of a GRB reverse shock, a comprehensive analysis of the plateau phase of GRB light curves, studies of the evolution of the progenitor population to redshifts, z~9, and demonstrate the use of GRBs as probes of galaxy formation and evolution through the first galaxy mass-metallicity relation at z~3-5. I find support for baryonic ejecta in GRB~130427A, evidence that GRB jets contain a large amount of energy in slow-moving ejecta, and proof that the GRB progenitor population does not evolve to the highest redshifts at which it has yet been observed. Building on the decade of observations by the Swift GRB mission, future observations and modeling of GRBs and their host galaxies will provide clues to these and other open questions in GRB science, allowing for the first statistical studies of their progenitors and host environments to the epoch of reionization and beyond.Astronomy
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Panaitescu, Alin-Daniel. "Gamma-ray bursts and afterglows from relativistic fireballs." Adobe Acrobat reader required to view the full dissertation, 1999. http://www.etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-11/index.html.
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Ahlgren, Björn. "Subphotospheric dissipation in gamma-ray bursts observed by the Fermi Gamma-ray Space Telescope." Licentiate thesis, KTH, Partikel- och astropartikelfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202323.
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Gamma-ray bursts (GRBs) are the brightest events in the Universe, for a short time outshining the rest of the Universe combined, as they explode with isotropic equivalent luminosities up to $10^{54}$ erg s$^{-1}$. These events are believed to be connected to supernovae and to binary compact object mergers, such as binary neutron stars or neutron star -- black hole systems. The origin of the so-called prompt emission in GRBs remains an unsolved problem, although some progress is being made. Spectral analysis of prompt emission has traditionally been performed with the Band function, an empirical model with no physical interpretation, and it is just recently that physical models have started to be fitted to data. This thesis presents spectral analysis of GRB data from the Fermi Gamma-ray Space Telescope using a physical model for subphotospheric dissipation. The model is developed using a numerical code and implemented as a table model in {\scriptsize XSPEC}. Paper \rom{1} presents the model and provides a proof-of-concept of fitting GRB data with such a model. Specifically, two GRBs are fitted and compared with the corresponding Band function fits. In paper \rom{2}, a sample of 37 bursts are fitted with an extended version of the model and improved analysis tools. Overall, about a third of the fitted spectra can be described by the model. From these fits it is concluded that the scenario of subphotospheric dissipation can describe all spectral shapes present in the sample. The key characteristic of the spectra that are not fitted by the model is that they are very luminous. Within the context of the model, this suggests that the assumption of internal shocks as a dissipation mechanism cannot explain the full population of GRBs. Alternatively, additional emission components may required. The thesis concludes that subphotospheric dissipation is viable as a possible origin of GRB prompt emission. Furthermore, it shows the importance of using physically motivated models when analysing GRBs.QC 20170221
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Fong, W., R. Margutti, R. Chornock, E. Berger, B. J. Shappee, A. J. Levan, N. R. Tanvir, et al. "THE AFTERGLOW AND EARLY-TYPE HOST GALAXY OF THE SHORT GRB 150101B AT z = 0.1343." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622673.
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We present the discovery of the X-ray and optical afterglows of the short-duration GRB 150101B, pinpointing the event to an early-type host galaxy at z = 0.1343 +/- 0.0030. This makes GRB 150101B the most nearby short gamma-ray burst (GRB) with an early-type host galaxy discovered to date. Fitting the spectral energy distribution of the host galaxy results in an inferred stellar mass of approximate to 7 x 10(10) M-circle dot, stellar population age of approximate to 2-2.5 Gyr, and star formation rate of less than or similar to 0.4M(circle dot) yr(-1). The host of GRB 150101B is one of the largest and most luminous short GRB host galaxies, with a B-band luminosity of approximate to 4.3L(*) and half-light radius of approximate to 8 kpc. GRB 150101B is located at a projected distance of 7.35 +/- 0.07. kpc from its host center and lies on a faint region of its host rest-frame optical light. Its location, combined with the lack of associated supernova, is consistent with an NS-NS/NS-BH merger progenitor. From modeling the evolution of the broadband afterglow, we calculate isotropic-equivalent gamma-ray and kinetic energies of approximate to 1.3 x 10(49) erg and approximate to(6-14) x 10(51) erg, respectively, a circumburst density of approximate to(0.8-4) x 10(-5) cm(-3), and a jet opening angle of greater than or similar to 9 degrees. Using observations extending to approximate to 30 days, we place upper limits of less than or similar to(2-4) x 10(41) erg s(-1) on associated kilonova emission. We compare searches following previous short GRBs to existing kilonova models and demonstrate the difficulty of performing effective kilonova searches from cosmological short GRBs using current ground-based facilities. We show that at the Advanced LIGO/VIRGO horizon distance of 200 Mpc, searches reaching depths of approximate to 23-24 AB. mag are necessary to probe a meaningful range of kilonova models.
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Ioka, Kunihito. "Relativistic jets from magnetars towards understanding Gamma-Ray Bursts." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150815.
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Hurkett, Cheryl Pauline. "Gamma ray bursts : selected results from the Swift mission." Thesis, University of Leicester, 2009. http://hdl.handle.net/2381/4380.
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Gamma Ray Bursts (GRBs) are short, energetic events that mark the most violent explosions in the Universe. Current hypotheses associated them with the births of stellar-sized black holes or rapidly spinning, highly magnetized stars. The introduction to this work places GRBs in their historical and theoretical context and provides a description of the current models describing them. This study makes use of data from the Swift satellite. Chapter two is a multi-wavelength study of the high redshift GRB 050505, which indicates that this burst has properties consistent with the general lower z GRB sample. Furthermore there is evidence for a `jet-break' in the X-ray light curve; a phenomena rarely seen in Swift era bursts. The next two chapters investigate the presence of X-ray emission lines in GRB spectra. Chapter three provides a discussion of the pre-Swift observations and a comparison of three methods already extant in the literature for assessing the signiffcance of such spectral features. The detection limits for each method were determined for emission line strengths in bursts with spectral parameters typical of the Swift era sample. Chapter four applies these methods to a sample of 40 Swift bursts; no strong evidence was found for emission lines in early time X-ray spectra once host galaxy absorption was accurately modelled. Chapter five investigates the phenomena of `precursors' and `quiescent intervals', indicating a common origin for events normally ascribed to `prompt emission' and `flares', in line with previous studies, and extending it to cover `precursor' emission. Evidence was also found to reinforce (anti-)correlations seen between pulse temporal and energetic properties also seen in previous studies. The final chapter summarises the important results for each section and proposes future studies that could be conducted in each field.
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Fong, Wen-fai. "Unveiling the Progenitors of Short-duration Gamma-ray Bursts." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11665.
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Gamma-ray bursts (GRBs) are relativistic explosions which originate at cosmological distances, and are among the most luminous transients in the universe. Following the prompt gamma-ray emission, a fading synchrotron "afterglow" is detectable at lower energies. While long-duration GRBs (duration > 2 sec) are linked to the deaths of massive stars, the progenitors of short-duration GRBs (duration < 2 sec) have remained elusive. Theoretical predictions formulated over the past two decades have suggested that they are the mergers of two compact objects, involving either two neutron stars (NS-NS) or a neutron star and a black hole (NS-BH). Such merging systems are also important to understand because they are premier candidates for gravitational wave detections with upcoming facilities and are considered likely sites of heavy element nucleosynthesis. The launch of the Swift satellite in 2004, with its rapid multi-wavelength monitoring and localization capabilities, led to the first discoveries of short GRB afterglows and therefore robust associations to host galaxies. At a Swift detection rate of ~8 events per year, the growing number of well-localized short GRBs enables comprehensive population studies of their afterglows and environments for the first time. In this thesis, I undertake a multi-wavelength observational campaign to address testable predictions for the progenitors of short GRBs. From their local environments, I show that short GRBs explode in diffuse regions of their host galaxies and are weakly correlated with the distribution of stellar mass and star formation in their host galaxies. I study the host galaxy demographics for the entire population and find that ~20-40% of short GRBs originate from elliptical galaxies, implying an older stellar progenitor. From their afterglows, I present evidence that some short GRBs are collimated in narrow jets of ~5-10 degrees, directly affecting the true energy scale and event rate. Finally, taking advantage of a decade of broad-band afterglow observations at radio through X-ray wavelengths, I find that short GRBs have median isotropic-equivalent energies of ~10^51 erg and that their local environments have low densities, ~10^-3-10^-2 cm^-3. Taken together, this thesis comprises several lines of independent evidence to demonstrate that short GRBs originate from the mergers of two compact objects, and also provides the first constraints on the explosion properties for a large sample of events. With the direct detection of gravitational waves from compact object mergers on the horizon, these studies provide necessary inputs to inform the next decade of joint electromagnetic-gravitational wave search strategies.Astronomy
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McEvoy, Erica Lynn 1981. "Determining the jet opening-angle of gamma-ray bursts." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32718.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (leaves 25-28).
There is growing scientific agreement that at least some cosmic gamma-ray bursts (GRBs) coincide with the deaths of rapidly rotating massive stars - dubbed "hyper-novae." In 1987, a supernova (SN 1987A) was detected in the Large Magellanic Cloud - its progenitor was a blue, rapidly rotating supergiant that was probably a member of a binary system that underwent merger prior to the supernova event [1]. Was SN 1987A a (possibly failed) hypernova? Although no accompanying GRB was detected, there is evidence [2] that one may have occurred but was beamed in a direction away from the earth. If so, are massive binary systems the progenitors of hypernovae and, in turn, of GRBs? In this thesis, we use a phenomenological model to determine [theta], the opening angle of the beams of GRBs. Our basic underlying assumption is that objects like SN 1987A are hypernovae, i.e., that they produce certain GRBs. We calculate [theta] by deriving two expressions for the probability that a given GRB is detected, one based on the solid geometry implied by the beaming model and the other based on the number of GRBs observed over time. These expressions give the probability as a function of a few key physical variables. By obtaining realistic estimates of the physical variables, equating the two expressions, and performing a Monte-Carlo simulation, we obtain an estimate of the most probable value of [theta]. We find that [theta] = 6.203⁰ ± 1.620⁰. Because this result is well in agreement with values inferred from the observed properties of GRBs [3]; and with values calculated based on the structured jet model of GRBs [4], we conclude that our underlying assumption - that SN 1987A was a hypernova - is at the very least plausible.
by Erica Lynn McEvoy.
S.B.
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Cenko, Stephen Bradley Harrison Fiona A. Harrison Fiona A. Kulkarni S. R. "The energetics and environments of Swift gamma-ray bursts /." Diss., Pasadena, Calif. : California Institute of Technology, 2009. http://resolver.caltech.edu/CaltechETD:etd-06272008-153145.
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Aoi, Junichi. "Exploring the Gamma Ray Bursts from GeV-TeV spectra." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142363.
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Valan, 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.
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Gamma-ray bursts (GRBs) are still puzzling scientists even 40 years after their discovery. Questions concerning the nature of the progenitors, the connection with supernovae and the origin of the high-energy emission are still lacking clear answers. Today, it is known that there are two populations of GRBs: short and long. It is also known that long GRBs are connected to supernovae (SNe). The emission observed from GRBs can be divided into two phases: the prompt emission and the afterglow. This thesis presents spectral analysis of the early X-ray afterglow of GRBs observed by the {\it Swift} satellite. For the majority of GRBs the early X-ray afterglows are well described by an absorbed power-law model. However, there exists a number of cases where this power-law component fails in fully describing the observed spectra and an additional blackbody component is needed. In the paper at the end of this thesis, a time-resolved spectral analysis of 74 GRBs observed by the X-ray telescope on board {\it Swift} is presented. Each spectrum is fitted with a power-law and a power-law plus blackbody model. The significance of the added thermal component is then assessed using Monte Carlo simulations. Six new cases of GRBs with thermal components in their spectra are presented, alongside three previously reported cases. The results show that a cocoon surrounding the jet is the most likely explanation for the thermal emission observed in the majority of GRBs. In addition, the observed narrow span in radii points to these GRBs being produced in similar environments.QC 20171031
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Deprez, Hannah. "Investigating the Time Evolution of X-Ray Absorption in Gamma-Ray Bursts." Thesis, KTH, Fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277830.
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Willis, Dave. "Mass modelling techniques for gamma ray burst missions." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274467.
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Iyyani, Shabnam. "Photospheric emission in gamma ray bursts : Analysis and interpretation of observations made by the Fermi gamma ray space telescope." Doctoral thesis, Stockholms universitet, Fysikum, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-116244.
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The large flashes of radiation that are observed in GRBs are generally believed to arise in a relativistic jetted outflow. This thesis addresses the question of how and where in the jet this radiation is produced. It further explores the jet properties that can be inferred from the observations made by the Fermi GST that regularly observes GRBs in the range 8 keV - 300 GeV. In my analysis I focus on the observational effects of the emission from the jet photosphere. I show that the photosphere has an important role in shaping the observed radiation spectrum and that its manifestations can significantly vary between bursts. For bursts in which the photospheric emission component can be identified, the dynamics of the flow can be explored by determining the jet Lorentz factor and the position of the jet nozzle. I also develop the theory of how to derive the properties of the outflow for general cases. The spectral analysis of the strong burst GRB110721A reveals a two-peaked spectrum, with the peaks evolving differently. I conclude that three main flow quantities can describe the observed spectral behaviour in bursts: the luminosity, the Lorentz factor, and the nozzle radius. While the photosphere can appear like a pure blackbody it can also be substantially broadened, due to dissipation of the jet energy below the photosphere. I show that Comptonisation of the blackbody can shape the observed spectra and describe its evolution. In particular this model can very well explain GRB110920A which has two prominent breaks in its spectra. Alternative models including synchrotron emission leads to severe physical constraints, such as the need for very high electron Lorentz factors, which are not expected in internal shocks. Even though different manifestations of the photospheric emission can explain the data, and lead to ambiguous interpretations, I argue that dissipation below the photosphere is the most important process in shaping the observed spectral shapes and evolutions.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: In press. Paper 5: Submitted.
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Tam, Pak-hin. "A study of the optical afterglows of gamma-ray bursts." Thesis, Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B31367677.
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Naumann-Godó, Melitta. "Sensitivity of the ANTARES neutrino telescope to gamma-ray bursts." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983803072.
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Campisi, Maria Angela. "Gamma-ray Bursts and their Host Galaxies from Cosmological Simulation." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-110091.
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Taylor, Paul A. "Understanding long-duration gamma-ray bursts : modelling collapsars with SPH." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497107.
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McEvoy, Erica Lynn 1981. "Determining the jet opening angle of cosmic gamma-ray bursts." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33943.
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Littlejohns, Owen Madoc. "Modelling the prompt and afterglow emission of gamma-ray bursts." Thesis, University of Leicester, 2013. http://hdl.handle.net/2381/27949.
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This thesis studies the broadband behaviour of GRBs by fitting a detailed spectral/temporal model to both the prompt and afterglow hard and soft X-ray emission observed by the Swift satellite. The prompt emission is decomposed into pulses which are fitted individually while the afterglow is modelled using a smoothly varying broad pulse which evolves into a power-law decay at late times. Using this model a comprehensive study of GRB 080310 is presented and followed by similar analyses of GRB 061121, GRB 080810 and GRB 081008. The optical behaviour is found to be inconsistent with the high-energy model: a spectral break between the X-ray and optical band is necessary and for many prompt pulses the self-absorption mechanism is required. The latter three bursts have optical afterglows that are shown to be inconsistent with those fitted to the X-ray regime, peaking earlier in the lower energy bands and requiring a low-energy spectral break. The prompt optical emission seen from GRB 061121 has pulse-like features which match reasonably well with contemporaneous high-energy features, but have longer durations. The same model was used to study the expected evolution of GRB properties when moved to higher redshifts. Using a sample of bright Swift GRBs, the changes in measured duration with redshift were found to be driven by a combination of time dilation, gradual loss of pulse tails and sudden loss of pulses as the flux falls below instrumental sensitivity. A realistic sample of synthetic bursts is produced which, when simulated at high redshift, are found to be significantly longer in duration that the observed high redshift GRBs. Also demonstrated is that several bright bursts seen by Swift could be detected if they occurred at a redshift > 10 encouraging the use of GRBs as probes of the early Universe.
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Jonsson, Teodor, and Oscar Wistemar. "Exploring Absorption in the Host Galaxies of Gamma-Ray Bursts." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276423.
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Gamma-ray bursts (GRB) are extremely high energy pulses that are connected to supernovae and black hole formation. They are divided into two forms, long and short GRBs. The emission of a GRB are split into two phases, the prompt emission primarily observed in gamma-rays and the afterglow which is synchrotron radiation sent out when the relativistic jet collides with the circumstellar medium. It is known that the X-ray emission is absorbed, however we can not say how this absorption is distributed between the host galaxy and the Intergalactic medium (IGM). In this paper we will use X-ray spectral analysis of long GRBs at different redshifts using X-ray data from the Swift telescope to investigate the time evolution of the absorption. Constant evolution points to the majority of the absorption taking place in the IGM and for decreasing, close to the GRB. Spectra will be fitted with an absorbed power-law using chi-square statistics. The results will show one clear case of constant behaviour and two GRBs that seem constant but with bad statistics. One GRB shows a clear decreasing behaviour. Two GRBs show nonphysical behaviour which indicates that the absorbed power-law might not be the correct model for these GRBs. Given the uncertainties in the analysis we may conclude that the majority of the GRBs we analysed exhibit a constant behaviour which would indicate a dominant portion of the absorption occurring within the IGM.Gammablixtar är extremt högenergetiska pulser som är sammankopplade med supernovor och formeringen av svarta hål. De är indelade i två typer, långa och korta gammablixtar. Utstrålningen från gammablixtar är uppdelade i två olika faser, prompt emission som huvudsakligen observeras i gammastrålning och efterglöden som är då den relativistiska jetstrålen kolliderar med det omkringliggande materialet. Det kan observeras att röntgenstrålningen absorberas, däremot kan vi inte säga hur denna absorption är fördelad mellan det intergalaktiska mediet(IGM) och värdgalaxen. Den här rapporten kommer använda spektralanalys av av gammablixtar vid olika rödskifte genom att använda röntgen data från Swift teleskopet för att undersöka tidsevolutionen av absorptionen. Konstant evolution tyder på att majoriteten av absorptionen sker i IGM medans för avtagande nära gammablixten. Spektrum kommer anpassas till en absorberad power-law med användande av chi-kvadrat statistiska metoder. Resultatet kommer att uppvisa ett tydligt fall med konstant beteende och två som verkar konstanta men med dålig statistik. En gammablixt visar tydligt avtagande beteende. Två stycken uppvisar icke-fysikaliskt beteende vilket kan vara en indikation på att den absorberade potenslagen vi använder ej är den korrekta modellen. Givet osäkerheten i analysen så kan vi dra slutsatsen att majoriteten av gamma-blixtarna vi analyserat uppvisar konstant beteende vilket indikerar att absorptionen är dominant inom det intergalaktiska mediet.
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Bloom, Joshua Simon Harrison Fiona A. "Towards an understanding of the progenitors of gamma-ray bursts /." Diss., Pasadena, Calif. : California Institute of Technology, 2002. http://resolver.caltech.edu/CaltechETD:etd-01062003-061357.
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林敬偉 and King-wai Lam. "Time delay and broadening of gamma ray bursts in various energy bands." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31213200.
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