Journal articles on the topic 'Gamma Ray Bursts (GRBs)'
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1
PIRAN, TSVI. "GAMMA-RAY BURSTS." International Journal of Modern Physics A 17, no. 20 (August 10, 2002): 2727–31. http://dx.doi.org/10.1142/s0217751x02011680.
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Gamma-Ray Bursts (GRBs) are the most relativistic objects discovered so far. I describe here two aspects of the relativistic nature of GRBs. Their likely association with the formation of black holes and their possible role as sources of gravitational radiation.
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Castro-Tirado, Alberto J. "Gamma-ray Bursts." International Astronomical Union Colloquium 192 (2005): 459–66. http://dx.doi.org/10.1017/s0252921100009544.
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SummarySince their discovery in 1967 Gamma-ray bursts (GRBs) have been puzzling to astrophysicists. With the advent of a new generation of X–ray satellites in the late 90’s, it was possible to carry out deep multi-wavelength observations of the counterparts associated with the long duration GRBs class just within a few hours of occurrence, thanks to the observation of the fading X-ray emission that follows the more energetic gamma-ray photons once the GRB event has ended. The fact that this emission (the afterglow) extends at longer wavelengths, led to the discovery of optical/IR/radio counterparts in 1997-2003, greatly improving our understanding of these sources. The classical, long duration GRBs, have been observed to originate at cosmological distances in a range of redshifts with 0.1685 ≤ z ≤ 4.50 implying energy releases of ~ 1051 ergs. The recent results on GRB 021004 and GRB 030329 confirm that the central engines that power these extraordinary events are due to be collapse of massive stars rather than the merging of compact objects as previously also suggested. Short GRBs still remain a mystery as no counterparts have been detected so far.
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Lamb, D. Q. "Gamma-ray bursts and cosmology." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1854 (February 13, 2007): 1363–76. http://dx.doi.org/10.1098/rsta.2006.1979.
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I review the current status of the use of gamma-ray bursts (GRBs) as probes of the early Universe and cosmology. I describe the promise of long GRBs as probes of the high redshift ( z >4) and very high redshift ( z >5) Universe, and several key scientific results that have come from observations made possible by accurate, rapid localizations of these bursts by Swift. I then estimate the fraction of long GRBs that lie at very high redshifts and discuss ways in which it may be possible to rapidly identify—and therefore study—a larger number of these bursts. Finally, I discuss the ways in which both long and short GRBs can be made ‘standard candles’ and used to constrain the properties of dark energy.
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Zhang, Zhibin, Yongfeng Huang, and Hongchao Liu. "On the Reclassification of Short GRBs." Proceedings of the International Astronomical Union 8, S290 (August 2012): 361–63. http://dx.doi.org/10.1017/s1743921312020418.
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AbstractBy collecting 17 short gamma-ray bursts with necessary data, we find a correlation of Lp ∝ Ep,i1.7, which is very consistent with that derived from a greatly expanded sample of 148 Swift long gamma-ray bursts. It is argued that the radiation mechanism of both long and short gamma-ray bursts should be similar, i.e., of quasi-thermal origin caused by the photosphere and the dissipation occurring very near the central engine. In addition, we suggest that the Ep,i-Lp relation can be used to identified a burst among normal short bursts, short bursts with extended emission and long bursts with short-hard properties. We also find the ratio of peak energy to fluence in the prompt γ-ray band is a prospective discriminator, similar to the traditional duration time.
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Chandra, Poonam. "Gamma-Ray Bursts: A Radio Perspective." Advances in Astronomy 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/2967813.
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Gamma-ray bursts (GRBs) are extremely energetic events at cosmological distances. They provide unique laboratory to investigate fundamental physical processes under extreme conditions. Due to extreme luminosities, GRBs are detectable at very high redshifts and potential tracers of cosmic star formation rate at early epoch. While the launch ofSwiftandFermihas increased our understanding of GRBs tremendously, many new questions have opened up. Radio observations of GRBs uniquely probe the energetics and environments of the explosion. However, currently only 30% of the bursts are detected in radio bands. Radio observations with upcoming sensitive telescopes will potentially increase the sample size significantly and allow one to follow the individual bursts for a much longer duration and be able to answer some of the important issues related to true calorimetry, reverse shock emission, and environments around the massive stars exploding as GRBs in the early Universe.
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Řípa, Jakub, and Arman Shafieloo. "Update on testing the isotropy of the properties of gamma-ray bursts." Monthly Notices of the Royal Astronomical Society 486, no. 3 (April 26, 2019): 3027–40. http://dx.doi.org/10.1093/mnras/stz921.
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Abstract Previously, we proposed a novel method to inspect the isotropy of the properties of gamma-ray bursts (GRBs), such as their duration, fluences and peak fluxes at various energy bands and different time-scales, complementary to existing studies of the spatial distribution of GRBs by other authors. The method was then applied to the Fermi Gamma-ray Burst Monitor (GBM) Burst Catalog containing 1591 GRBs. Except for one particular direction where we noticed some hints of violation from statistical isotropy, the rest of the data showed consistency with isotropy. In this work, we apply our method, with some minor modifications, to the updated Fermi GBM data sample containing 2266 GRBs, which is thus ∼40 per cent larger. We also test two other major GRB catalogues: the Burst And Transient Source Experiment (BATSE) Current GRB Catalog of the Compton Gamma Ray Observatory (CGRO), containing ∼2000 bursts, and the Swift Burst Alert Telescope (BAT) GRB Catalog, containing ∼1200 bursts. The new results using the updated data are consistent with our previous findings and we find no statistically significant anisotropic feature in the observed properties of these samples of all GRBs.
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Vasquez, Nicolas A., and Christian Vasconez. "Classification of long Gamma Ray Bursts using cosmologically corrected temporal estimators." Proceedings of the International Astronomical Union 7, S279 (April 2011): 417–18. http://dx.doi.org/10.1017/s1743921312013622.
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AbstractThe canonical classification of GRBs establishes two types of bursts, long and short. Although an intermediate class of GRBs was suggested, its existence is not yet conclusive. In the present work, we explore the temporal classification of GRBs in the burst frame, because in recent years the statistics of bursts with known redshifts has increased. We studied a sample of Swift GRBs with known redshifts to determine three different time estimators: autocorrelation functions, emission times and duration times. In order to look for a subclass in long GRBs, we studied the distribution of the cosmologically corrected time estimators. The distribution of time estimators of the sample suggests an internal division of long GRBs. The proposed bimodality is also supported in the isotropic luminosity - time estimator planes and we discuss some possible implications of the classification of GRBs in the burst frame.
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GEHRELS, N., and J. K. CANNIZZO. "GAMMA-RAY BURSTS — OBSERVATIONS." International Journal of Modern Physics D 19, no. 06 (June 2010): 977–84. http://dx.doi.org/10.1142/s021827181001710x.
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We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. The Fermi observatory is observing 250 bursts per year with its medium-energy GRB instrument and about 10 bursts per year with its high-energy LAT instrument. In addition, rapid-response telescopes on the ground are providing new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and high-energy emission.
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Gehrels, Neil. "Swift observations of gamma-ray bursts." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1854 (February 9, 2007): 1119–28. http://dx.doi.org/10.1098/rsta.2006.1975.
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Since its launch on 20 November 2004, the Swift mission has been detecting approximately 100 gamma-ray bursts (GRBs) each year, and immediately (within approx. 90 s) starting simultaneous X-ray and UV/optical observations of the afterglow. It has already collected an impressive database, including prompt emission to higher sensitivities than BATSE, uniform monitoring of afterglows and a rapid follow-up by other observatories notified through the GCN. Advances in our understanding of short GRBs have been spectacular. The detection of X-ray afterglows has led to accurate localizations and the conclusion that short GRBs can occur in non-star-forming galaxies or regions, whereas long GRBs are strongly concentrated within the star-forming regions. This is consistent with the NS merger model. Swift has greatly increased the redshift range of GRB detection. The highest redshift GRBs, at z ∼5–6, are approaching the era of reionization. Ground-based deep optical spectroscopy of high redshift bursts is giving metallicity measurements and other information on the source environment to a much greater distance than other techniques. The localization of GRB 060218 to a nearby galaxy, and the association with SN 2006aj, added a valuable member to the class of GRBs with detected supernova.
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Liu, Xiang. "Simple Reduction of Gamma-Ray Bursts." Symposium - International Astronomical Union 214 (2003): 333–34. http://dx.doi.org/10.1017/s0074180900194689.
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We try to explain the different type of GRBs from their properties, most likely the long duration GRBs are the NS-NS collision, short duration ones are the WD-WD collision, and intermediate ones are the NS-WD collision.
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Levan, Andrew J. "Short gamma-ray bursts near and far." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1854 (February 9, 2007): 1315–21. http://dx.doi.org/10.1098/rsta.2006.1981.
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Progress in understanding the nature of short gamma-ray bursts (GRBs) has been rapid since the discovery of the first afterglows in mid-2005. The emerging picture appears to be of short GRBs, which originate at moderate redshift (a few tenths) and appear in galaxies of all ages. This discovery has been used to argue for their origin in compact binary mergers. However, this population does not describe all short bursts. Here, I will present results of observations of several short GRBs, which challenge the conclusions drawn from the early observations. The observations show that some short GRBs originate in the very low redshift Universe (below 100 Mpc), while some may also lie at redshifts comparable with the long GRBs (i.e. z >2). I will discuss the properties of these bursts and the implications they have for the progenitors of short GRBs.
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Tanvir, N. R. "Gamma-ray Bursts Progress and Problems." Proceedings of the International Astronomical Union 12, S324 (September 2016): 49–53. http://dx.doi.org/10.1017/s1743921317001788.
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AbstractOur understanding of gamma-ray bursts (GRBs) has come a long way in the past fifty years since their first detection. We now know that GRBs arise in distant galaxies and that there are at least two distinct sub-classes, the long-duration class being produced by some rare massive star core collapse and the short-duration class likely by compact binary mergers involved neutron stars. In both cases, the final remnant will be a stellar-mass black-hole or a massive neutron star. The bursts themselves are associated with ultra-relativistic jetted outflows created by these events, and their afterglows by the impact of these outflows on the surrounding circumburst material. Increasingly GRBs are also being used as probes of the universe, both for understanding galaxy evolution back to the era of reionization, and for the physics of gravitational wave sources. However, many aspects of GRBs remain poorly understood, some pointers to which are given here.
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Totani, Tomonori. "Gamma-Ray Bursts as Cosmological Probes." Proceedings of the International Astronomical Union 7, S279 (April 2011): 241–47. http://dx.doi.org/10.1017/s1743921312012999.
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AbstractThe status and prospects for gamma-ray bursts (GRBs) as cosmological probes are reviewed. Long duration GRBs can potentially be used as an indicator of star formation rate (SFR), though GRB rate might be systematically different from SFR, by the effect of e.g. metallicity. There are several papers claiming that the cosmic GRB rate history is different from that of SFR in the sense that GRB rate is relatively higher than SFR at higher redshifts, which may be explained by the metallicity effect. However, considering the large uncertainties about the efficiency of GRB afterglow detection and redshift determination, it would be conservative to state that the observed GRB rate is roughly consistent with the star formation history. GRBs can also be used as a unique and powerful tool to reveal the reionization history. However, there is practically no progress in this direction since the first GRB-based useful constraint on reionization in 2005 (GRB 050904). The bottleneck now is the insufficient sensitivity of near-infrared spectroscopy, even with 8m class telescopes. The planned 30m class telescopes will bring the next breakthruough. Finally, GRBs can potentially be used as a standard candle to study cosmology by a geometrical test. However, there are still many steps for GRBs to overcome before it produces a result that has strong impact on the cosmology community in the precision cosmology era.
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Fryer, Chris L., Amy Y. Lien, Andrew Fruchter, Giancarlo Ghirlanda, Dieter Hartmann, Ruben Salvaterra, Phoebe R. Upton Sanderbeck, and Jarrett L. Johnson. "Properties of High-redshift Gamma-Ray Bursts." Astrophysical Journal 929, no. 2 (April 1, 2022): 111. http://dx.doi.org/10.3847/1538-4357/ac5d5c.
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Abstract The immense power of gamma-ray bursts (GRBs) makes them ideal probes of the early universe. By using absorption lines in the afterglows of high-redshift GRBs, astronomers can study the evolution of metals in the early universe. With an understanding of the nature of GRB progenitors, the rate and properties of GRBs observed at high redshift can probe the star formation history and the initial mass function of stars at high redshift. This paper presents a detailed study of the dependence on metallicity and mass of the properties of long-duration GRBs under the black hole accretion disk paradigm to predict the evolution of these properties with redshift. These models are calibrated on the current GRB observations and then used to make predictions for new observations and new missions (e.g., the proposed Gamow mission) studying high-redshift GRBs.
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GHISELLINI, GABRIELE. "EXTRAGALACTIC GAMMA-RAYS: GAMMA RAY BURSTS AND BLAZARS." International Journal of Modern Physics A 20, no. 29 (November 20, 2005): 6991–7000. http://dx.doi.org/10.1142/s0217751x05030673.
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The extragalactic gamma-ray sky is dominated by two classes of sources: Gamma-Ray Bursts (GRBs) and radio loud active galactic nuclei whose jets are pointing at us (blazars). We believe that the radiation we receive from them originates from the transformation of bulk relativistic energy into random energy. Although the mechanisms to produce, collimate and accelerate the jets in these sources are uncertain, it is fruitful to compare the characteristics of both classes of sources in search of enlightening similarities. I will review some general characteristics of radio loud AGNs and GRBs and I will discuss the possibility that both classes of sources can work in the same way. Finally, I will discuss some recent exciting prospects to use blazars to put constraints on the cosmic IR-Optical-UV backgrounds, and to use GRBs as standard candles to measure the Universe.
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Kaper, Lex. "Gamma-ray bursts: the most powerful cosmic explosions." Symposium - International Astronomical Union 212 (2003): 106–14. http://dx.doi.org/10.1017/s0074180900211704.
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With the detection of gamma-ray burst (GRB) afterglows, the cosmological origin of GRBs has been firmly established. Recent observations suggest that (long-duration) GRBs are due to the collapse of a massive star forming a black hole. Besides theoretical arguments, observational evidence supporting this hypothesis comes from the coincidence of several GRBs with a supernova. Also, all accurately located GRBs are contained in the optical (restframe UV) extent of distant, blue galaxies. Some of these host galaxies show relatively high star-formation rates, which is expected when massive stars and GRBs are physically linked. Alternatively, GRBs can be produced by the merging of a binary neutron star system, such as the Hulse-Taylor binary pulsar. Very likely GRBs trace the massive-star populations in distant galaxies. With their enormous brightness, GRBs are powerful probes of the early universe, providing information on the properties of their host galaxies, the cosmic star-formation history, and potentially the first generations of massive stars.
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Asano, Katsuaki, and Kohta Murase. "Gamma-Ray Bursts as Multienergy Neutrino Sources." Advances in Astronomy 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/568516.
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We review theoretical models for nonelectromagnetic emission, mainly neutrinos and cosmic rays, from gamma-ray bursts (GRBs). In various stages of the relativistic jet propagation, cosmic-ray ion acceleration and subsequent neutrino emission are expected. GRBs are popular candidate sources of the highest-energy cosmic rays, and their prompt phase has been most widely discussed. IceCube nondetection of PeV neutrinos coincident with GRBs has put interesting constraints on the standard theoretical prediction. The GRB-UHECR hypothesis can critically be tested by future observations. We also emphasize the importance of searches for GeV-TeV neutrinos, which are expected in the precursor/orphan or prompt phase, and lower-energy neutrinos would be more guaranteed and their detections even allow us to probe physics inside a progenitor star. Not only classical GRBs but also low-power GRBs and transrelativistic supernovae can be promising sources of TeV-PeV neutrinos, and we briefly discuss implications for the cumulative neutrino background discovered by IceCube.
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Wang, Yun, Lu-Yao Jiang, and Jia Ren. "GRB 201104A: A “Repetitive” Short Gamma-Ray Burst?" Astrophysical Journal 935, no. 2 (August 1, 2022): 179. http://dx.doi.org/10.3847/1538-4357/ac82ec.
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Abstract Gamma-ray bursts (GRBs) are divided into short gamma-ray bursts (SGRBs) and long gamma-ray bursts (LGRBs) based on the bimodal distribution of their durations. LGRBs and SGRBs are typically characterized by different statistical characteristics. Nevertheless, there are some samples that challenge such a framework, such as GRB 060614, a long-duration burst with short-burst characteristics. Furthermore, GRBs are generally considered to be an event with no periodic or repetitive behavior, since the progenitors usually undergo destructive events, such as massive explosions or binary compact star mergers. In this work, we investigated Fermi data for possible quasiperiodic oscillations and repetitive behaviors of GRBs using timing analysis methods and report a special event GRB 201104A, which is a long-duration burst with the characteristics of an SGRB, and it exhibits a “repetitive” behavior. We propose that such a situation may arise from lensed SGRBs and attempt to verify it by Bayesian inference. In addition, we extend the spectral analysis to Bayesian inference. In spite of the existence of at least two distinct time periods with a nearly identical spectrum, there is no strong evidence that they result from a lensing GRB. Taking the gravitational-lensing scenario out of consideration, a long burst would resemble a short burst in its repetitive behavior, which presents a challenge for the current classification scheme.
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GEHRELS, NEIL. "SWIFT OBSERVATIONS OF GAMMA-RAY BURSTS." International Journal of Modern Physics D 17, no. 09 (September 2008): 1311–17. http://dx.doi.org/10.1142/s0218271808012863.
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The Swift mission, launched on 20 November 2004, is detecting ~ 100 gamma-ray bursts (GRBs) each year, and immediately (within ~ 90 s) starting X-ray and UV/optical observations of the afterglow. It has already collected an impressive database including prompt emission to higher sensitivities than BATSE, uniform monitoring of afterglows, and rapid follow-up by other observatories notified through the Gamma-ray bursts Coordinates Network (GCN). The X-ray afterglows have been found to have complex temporal shapes including tails emission from the prompt phase and bright flares. X-ray and optical afterglow detections from short bursts have led to accurate localizations. It is found that they can occur in non-star forming galaxies or regions, whereas long GRBs are strongly concentrated within star forming regions. This is consistent with the NS merger model. Swift has greatly increased the redshift range of GRB detection. The highest redshift GRBs, at z ~ 5-6, are approaching the era of reionization. Ground-based deep optical spectroscopy of high redshift bursts is giving metallicity measurements and other information on the source environment to much greater distance than other techniques. The localization of GRB 060218 in a nearby galaxy, and association with SN 2006aj, added a valuable member to the class of GRBs with detected supernova. The prospects for future progress are excellent given the > 10 year orbital lifetime of the Swift satellite.
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Burbidge, Geoffrey. "Gamma-ray bursts, QSOs and active galaxies." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1854 (February 13, 2007): 1357–61. http://dx.doi.org/10.1098/rsta.2006.1969.
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The similarity of the absorption spectra of gamma-ray burst (GRB) sources or afterglows with the absorption spectra of quasars (QSOs) suggests that QSOs and GRB sources are very closely related. Since most people believe that the redshifts of QSOs are of cosmological origin, it is natural to assume that GRBs or their afterglows also have cosmological redshifts. For some years a few of us have argued that there is much optical evidence suggesting a very different model for QSOs, in which their redshifts have a non-cosmological origin, and are ejected from low-redshift active galaxies. In this paper I extend these ideas to GRBs. In 2003, Burbidge (Burbidge 2003 Astrophys. J. 183 , 112–120) showed that the redshift periodicity in the spectra of QSOs appears in the redshift of GRBs. This in turn means that both the QSOs and the GRB sources are similar objects ejected from comparatively low-redshift active galaxies. It is now clear that many of the GRBs of low redshift do appear in, or very near, active galaxies. A new and powerful result supporting this hypothesis has been produced by Prochter et al . (Prochter et al . 2006 Astrophys. J. Lett . 648 , L93–L96). They show that in a survey for strong MgII absorption systems along the sightlines to long-duration GRBs, nearly every sightline shows at least one absorber. If the absorbers are intervening clouds or galaxies, only a small fraction should show absorption of this kind. The number found by Prochter et al . is four times higher than that normally found for the MgII absorption spectra of QSOs. They believe that this result is inconsistent with the intervening hypothesis and would require a statistical fluctuation greater than 99.1% probability. This is what we expect if the absorption is intrinsic to the GRBs and the redshifts are not associated with their distances. In this case, the absorption must be associated with gas ejected from the QSO. This in turn implies that the GRBs actually originate in comparatively low-redshift active galaxies and are ejected in the same way as are the QSOs. This relates these phenomena to a supernova origin for the GRBs. The current situation based on the latest observational data will be discussed.
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Fishman, Gerald J. "Gamma-Ray Burst Observations with BATSE." Symposium - International Astronomical Union 188 (1998): 159–62. http://dx.doi.org/10.1017/s0074180900114664.
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Gamma-ray bursts (GRBs) will be recorded as one of the outstanding new phenomena discovered in astronomy this century. About once per day, a burst of gamma rays appears from a random direction on the sky. Often, the burst outshines all other sources of gamma-rays in the sky, combined. This paper reviews some of the key observed phenomenon of bursts in the hard x-ray/gamma-ray region, as observed with the BATSE experiment on the Compton Gamma Ray Observatory. The observed time profiles, spectral properties and durations of gamma-ray bursts cover a wide range. Recent breakthroughs in the observation of gamma-ray burst counterparts and afterglows in other wavelength regions have marked the beginning of a new era in gamma-ray burst research. Those observations are described in following papers in these proceedings.
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Mazzali, Paolo A. "Supernovae and Gamma-ray Bursts." Proceedings of the International Astronomical Union 7, S279 (April 2011): 75–82. http://dx.doi.org/10.1017/s1743921312012720.
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AbstractThe properties of the Supernovae discovered in coincidence with long-duration Gamma-ray Bursts and X-Ray Flashes are reviewed, and compared to those of SNe for which GRBs are not observed. The SNe associated with GRBs are of Type Ic, they are brighter than the norm, and show very broad absorption lines in their spectra, indicative of high expansion velocities and hence of large explosion kinetic energies. This points to a massive star origin, and to the birth of a black hole at the time of core collapse. There is strong evidence for gross asymmetries in the SN ejecta. The observational evidence seems to suggest that GRB/SNe are more massive and energetic than XRF/SNe, and come from more massive stars. While for GRB/SNe the collapsar model is favoured, XRF/SNe may host magnetars.
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Frontera, Filippo. "X-ray Emission from Gamma-Ray Bursts." International Astronomical Union Colloquium 192 (2005): 467–74. http://dx.doi.org/10.1017/s0252921100009556.
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Minaev, Pavel, Alexei Pozanenko, and Sergei Molkov. "Precursors of short gamma-ray bursts detected by the INTEGRAL observatory." International Journal of Modern Physics D 27, no. 10 (July 2018): 1844013. http://dx.doi.org/10.1142/s0218271818440133.
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We have analyzed the light curves of 527 short gamma-ray bursts (GRBs) registered by the SPI-ACS, SPI and IBIS/ISGRI experiments of INTEGRAL observatory totally to search for precursors. Both the light curves of each 527 individual burst and the averaged light curve of 372 brightest SPI-ACS bursts have been analyzed. In a few cases, we have found and investigated precursor candidates using SPI-ACS, SPI and IBIS/ISGRI of INTEGRAL, GBM and LAT of Fermi data. No convincing evidence for the existence of precursors of short GRBs has been found. A statistical analysis of the averaged light curve for the sample of brightest short bursts has revealed no regular precursor. Upper limits for the relative intensity of precursors have been estimated. We show that the fraction of short GRBs with precursors is less than 0.4% of all short bursts, detected by INTEGRAL.
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Watson, D., J. P. U. Fynbo, C. C. Thöne, and J. Sollerman. "No supernovae detected in two long-duration gamma-ray bursts." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1854 (February 12, 2007): 1269–75. http://dx.doi.org/10.1098/rsta.2006.1994.
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There is strong evidence that long-duration gamma-ray bursts (GRBs) are produced during the collapse of a massive star. In the standard version of the collapsar model, a broad-lined and luminous Type Ic core-collapse supernova (SN) accompanies the GRB. This association has been confirmed in observations of several nearby GRBs. Recent observations show that some long-duration GRBs are different. No SN emission accompanied the long-duration GRBs 060505 and 060614 down to limits fainter than any known Type Ic SN and hundreds of times fainter than the archetypal SN 1998bw that accompanied GRB 980425. Multi-band observations of the early afterglows, as well as spectroscopy of the host galaxies, exclude the possibility of significant dust obscuration. Furthermore, the bursts originated in star-forming galaxies, and in the case of GRB 060505, the burst was localized to a compact star-forming knot in a spiral arm of its host galaxy. We find that the properties of the host galaxies, the long duration of the bursts and, in the case of GRB 060505, the location of the burst within its host, all imply a massive stellar origin. The absence of an SN to such deep limits therefore suggests a new phenomenological type of massive stellar death.
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Piran, Tsvi, and Yi-Zhong Fan. "Gamma-ray burst theory after Swift." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1854 (February 9, 2007): 1151–62. http://dx.doi.org/10.1098/rsta.2006.1987.
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Afterglow observations in the pre-Swift era confirmed to a large extend the relativistic blast wave model for gamma-ray bursts (GRBs). Together with the observations of properties of host galaxies and the association with (type Ic) SNe, this has led to the generally accepted collapsar origin of long GRBs. However, most of the afterglow data was collected hours after the burst. The X-ray telescope and the UV/optical telescope onboard Swift are able to slew to the direction of a burst in real time and record the early broadband afterglow light curves. These observations, and in particular the X-ray observations, resulted in many surprises. While we have anticipated a smooth transition from the prompt emission to the afterglow, many observed that early light curves are drastically different. We review here how these observations are changing our understanding of GRBs.
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Dado, Shlomo, and Arnon Dar. "The Maximum Isotropic Equivalent Energy of Gamma-Ray Bursts." Astrophysical Journal Letters 940, no. 1 (November 1, 2022): L4. http://dx.doi.org/10.3847/2041-8213/ac98c8.
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Abstract In the cannonball model of gamma-ray bursts (GRBs), a highly relativistic jet of plasmoids of ordinary stellar matter that is ejected during stellar collapse or shortly after by fallback matter, produces simultaneously a GRB and a cosmic-ray burst by scattering light and charged particles in its path. This association and the observed knee at ∼1 TeV in the energy spectrum of Galactic cosmic-ray electrons imply a maximum peak energy ∼2.25 MeV in the energy spectrum of GRBs in the 1 keV–10 MeV band. Such a peak energy and the Amati correlation in GRBs imply a maximum isotropic equivalent energy release of ∼3.8 × 1054 erg in GRBs, in the 1 keV–10 MeV band. Both predictions are in good agreement with up-to-date observations.
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Ouyed, Rachid, Denis Leahy, Jan Staff, and Brian Niebergal. "Quark-Nova Explosion inside a Collapsar: Application to Gamma Ray Bursts." Advances in Astronomy 2009 (2009): 1–10. http://dx.doi.org/10.1155/2009/463521.
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If a quark-nova occurs inside a collapsar, the interaction between the quark-nova ejecta (relativistic iron-rich chunks) and the collapsar envelope leads to features indicative of those observed in Gamma Ray Bursts. The quark-nova ejecta collides with the stellar envelope creating an outward moving cap (Γ∼1–10) above the polar funnel. Prompt gamma-ray burst emission from internal shocks in relativistic jets (following accretion onto the quark star) becomes visible after the cap becomes optically thin. Model features include (i) precursor activity (optical, X-ray,γ-ray), (ii) promptγ-ray emission, and (iii) afterglow emission. We discuss SN-less long duration GRBs, short hard GRBs (including association and nonassociation with star forming regions), dark GRBs, the energetic X-ray flares detected in Swift GRBs, and the near-simultaneous optical andγ-ray prompt emission observed in GRBs in the context of our model.
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Noda, Koji, and Robert Daniel Parsons. "Gamma-Ray Bursts at TeV Energies: Observational Status." Galaxies 10, no. 1 (January 5, 2022): 7. http://dx.doi.org/10.3390/galaxies10010007.
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Gamma-ray bursts (GRBs) are some of the most energetic events in the Universe and are potential sites of cosmic ray acceleration up to the highest energies. GRBs have therefore been a target of interest for very high energy gamma-ray observatories for many years, leading to the recent discovery of a number of bursts with photons reaching energies above 100 GeV. We summarize the GRB observational campaigns of the current generation of very high energy gamma-ray observatories as well as describing the observations and properties of the GRBs discovered so far. We compare the properties of the very high energy bursts to the total GRB distribution and make predictions for the next generation of very high energy gamma-ray observations.
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Sakamoto, Takanori, Yuuki Yoshida, and Motoko Serino. "Investigation of Similarity in the Spectra between Short- and Long-Duration Gamma-ray Bursts." Galaxies 6, no. 4 (October 3, 2018): 106. http://dx.doi.org/10.3390/galaxies6040106.
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We investigated the spectral properties of the prompt emission for short- and long-duration gamma-ray bursts (GRBs) using the Fermi Gamma-ray Burst Monitor data. In particular, we focused on comparing the spectral properties of short GRBs and the initial 2 s of long GRBs, motivated by the previous study of Ghirlanda et al. (2009). We confirmed the similarity in the low energy photon index α between short GRBs and the initial 2 s of long GRBs. Since about a quarter of our spectra of both short GRBs and the initial 2 s of long GRBs show α to be shallower than - 2 / 3 , it is difficult to understand in the context standard synchrotron emission.
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AMATI, LORENZO, and MASSIMO DELLA VALLE. "MEASURING COSMOLOGICAL PARAMETERS WITH GAMMA RAY BURSTS." International Journal of Modern Physics D 22, no. 14 (December 2013): 1330028. http://dx.doi.org/10.1142/s0218271813300280.
Full textAbstract:
In a few dozen seconds, gamma ray bursts (GRBs) emit up to ~1054 erg in terms of an equivalent isotropically radiated energy E iso , so they can be observed up to z ~ 10. Thus, these phenomena appear to be very promising tools to describe the expansion rate history of the universe. Here, we review the use of the Ep,i–E iso correlation of GRBs to measure the cosmological density parameter ΩM. We show that the present data set of GRBs, coupled with the assumption that we live in a flat universe, can provide independent evidence, from other probes, that ΩM ~ 0.3. We show that current (e.g. Swift, Fermi/GBM, Konus-WIND) and forthcoming gamma ray burst (GRB) experiments (e.g. CALET/GBM, SVOM, Lomonosov/UFFO, LOFT/WFM) will allow us to constrain ΩM with an accuracy comparable to that currently exhibited by Type Ia supernovae (SNe–Ia) and to study the properties of dark energy and their evolution with time.
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Levan, Andrew. "Constraining gamma-ray burst progenitors." Proceedings of the International Astronomical Union 7, S279 (April 2011): 95–101. http://dx.doi.org/10.1017/s1743921312012756.
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AbstractThe past decade has seen great progress towards the unmasking of the progenitors of gamma-ray bursts, starting with the unambiguous detection of a supernova in the light of the long-GRB 030329 almost ten years ago, and the discovery of the first afterglows to short-GRBs in 2005. Here I review progress towards unveiling the progenitors of both long and short-duration GRBs. Furthermore, I examine the diverse broader population of GRBs and high energy transients, and suggest that a full consideration of this parameter space leads to the conclusion that additional progenitor models are likely to be needed, if we are to understand the complete view of GRBs and the transient high-energy sky.
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Willingale, Richard, and Paul T. O'Brien. "The late X-ray afterglow of gamma-ray bursts." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1854 (February 13, 2007): 1189–95. http://dx.doi.org/10.1098/rsta.2006.1996.
Full textAbstract:
We have developed a functional fit which can be used to represent the entire temporal decay of the X-ray afterglow of gamma-ray bursts (GRBs). The fit delineates and parameterizes well-defined phases for the decay: the prompt emission; an initial steep decay; a shallow plateau phase; and finally, a powerlaw afterglow. For 20% of GRBs, the plateau phase is weak, or not seen, and the initial powerlaw decay becomes the final afterglow. We compare the temporal decay parameters and X-ray spectral indices for 107 GRBs discovered by Swift with the expectations of the standard fireball model including a search for possible jet breaks. For approximately 50% of GRBs, the observed afterglow is in accord with the model, but for the rest the temporal and spectral properties are not as expected. We identify a few possible jet breaks, but there are many examples where such breaks are predicted but are absent. We also find that the start time of the final afterglow decay, T a , is associated with the peak of the prompt γ -ray emission spectrum, E peak , just as optical jet-break times, t j , are associated with E peak in the Ghirlanda relation.
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King, Andrew. "Gamma-ray burst models." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1854 (February 9, 2007): 1277–80. http://dx.doi.org/10.1098/rsta.2006.1978.
Full textAbstract:
I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts.
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Chattopadhyay, Tanmoy, Soumya Gupta, Shabnam Iyyani, Divita Saraogi, Vidushi Sharma, Anastasia Tsvetkova, Ajay Ratheesh, et al. "Hard X-Ray Polarization Catalog for a Five-year Sample of Gamma-Ray Bursts Using AstroSat CZT Imager." Astrophysical Journal 936, no. 1 (August 25, 2022): 12. http://dx.doi.org/10.3847/1538-4357/ac82ef.
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Abstract The Cadmium Zinc Telluride Imager (CZTI) on board AstroSat has been regularly detecting gamma-ray bursts (GRBs) since its launch in 2015. Its sensitivity to polarization measurements at energies above 100 keV allows CZTI to attempt spectropolarimetric studies of GRBs. Here, we present the first catalog of GRB polarization measurements made by CZTI during its first five years of operation. This includes the time-integrated polarization measurements of the prompt emission of 20 GRBs in the energy range 100–600 keV. The sample includes the bright GRBs that were detected within an angle range of 0°–60° and 120°–180° where the instrument has useful polarization sensitivity and is less prone to systematics. We implement a few new modifications in the analysis to enhance the polarimetric sensitivity of the instrument. The majority of the GRBs in the sample are found to possess less/null polarization across the total bursts’ duration in contrast to a small fraction of five GRBs that exhibit high polarization. The low polarization across the bursts might be due either to the burst being intrinsically weakly polarized or to a varying polarization angle within the burst even when it is highly polarized. In comparison to POLAR measurements, CZTI has detected a larger number of cases with high polarization. This may be a consequence of the higher energy window of CZTI observations, which results in the sampling of a shorter duration of burst emissions than POLAR, thereby probing emissions with less temporal variation in polarization properties.
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Marquez, Kauan D., and Débora P. Menezes. "Gamma Ray Bursts and Stellar Evolution." International Journal of Modern Physics: Conference Series 45 (January 2017): 1760008. http://dx.doi.org/10.1142/s2010194517600084.
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The phenomenon that originates gamma ray bursts (GRBs) remains undefined. In this work the conversion of a hadronic star into a quark star is discussed as one of the possible causes of GRBs. Effective models are used to describe the compact stars and to obtain their equations of state. Macroscopic properties, such baryonic and gravitational masses, of both types of stars are then obtained from the solution of the hydrostatic equilibrium equations. The relation between this values allows to calculate the amount of energy possibly released in this process. The obtained results are then compared to actual GRB observational data, and are within the observational order of magnitude.
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Merck, M., D. L. Bertsch, B. L. Dingus, C. E. Fichtel, R. C. Hartman, S. D. Hunter, G. Kanbach, et al. "Observations of High-energy Gamma-ray Bursts with EGRET." International Astronomical Union Colloquium 151 (1995): 358–62. http://dx.doi.org/10.1017/s0252921100035351.
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Gamma Ray Bursts (GRBs) have puzzled astronomers since their discovery more than 20 years ago. As no counterparts at wavelengths other than X- and γ-rays have yet been found the identification of the sources is still missing. Theoretical explanations range from colliding comets (1993) and merging neutron stars (1982) to more exotic objects, such as superconducting cosmic strings (1988). Data accumulated until now still do not discriminate between these models, although results from the BATSE (Burst and Transient Source Experiment) instrument aboard the Compton Gamma Ray Observatory (CGRO) strongly favor extragalactic models.The Energetic Gamma Ray Experiment Telescope (EGRET) aboard CGRO has s ofar detected photons from 5 GRBs with its spark chamber. These are the highest energy γ-rays associated with GRBs to date. In this work we review previously published data and summarize the properties of these events. Elsewhere we present possible constraints from the data on the models proposed to explain GRBs.
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RUFFINI, REMO. "BLACK HOLES, SUPERNOVAE AND GAMMA RAY BURSTS." International Journal of Modern Physics D 22, no. 11 (September 2013): 1360009. http://dx.doi.org/10.1142/s0218271813600092.
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We review recent progress in our understanding of the nature of Gamma Ray Bursts (GRBs) and in particular, of the relationship between short GRBs and long GRBs. The first example of a short GRB is described. The coincidental occurrence of a GRB with a supernova (SN) is explained within the induced gravitational collapse (IGC) paradigm, following the sequence: (1) an initial binary system consists of a compact carbon–oxygen (CO) core star and a neutron star (NS); (2) the CO core explodes as a SN, and part of the SN ejecta accretes onto the NS which reaches its critical mass and collapses to a black hole (BH) giving rise to a GRB; (3) a new NS is generated by the SN as a remnant. The observational consequences of this scenario are outlined.
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Levesque, Emily M. "Host Galaxies of Gamma-Ray Bursts." Proceedings of the International Astronomical Union 7, S279 (April 2011): 167–74. http://dx.doi.org/10.1017/s1743921312012872.
Full textAbstract:
AbstractHost galaxies are an excellent means of probing the natal environments that generate gamma-ray bursts (GRBs). Recent work on the host galaxies of short-duration GRBs has offered new insights into the parent stellar populations and ages of their enigmatic progenitors. Similarly, surveys of long-duration GRB (LGRB) host environments and their ISM properties have produced intriguing new results with important implications for long GRB progenitor models. These host studies are also critical in evaluating the utility of LGRBs as potential tracers of star formation and metallicity at high redshifts. I will summarize the latest research on LGRB host galaxies, and discuss the resulting impact on our understanding of these events' progenitors, energetics, and cosmological applications.
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Shibata, R., T. Murakami, Y. Ueda, A. Yoshida, F. Tokanai, C. Otani, N. Kawai, and K. Hurley. "Possible X-Ray Counterparts to Gamma-Ray Bursts, GRB930131 and GRB940217." Symposium - International Astronomical Union 188 (1998): 459–60. http://dx.doi.org/10.1017/s0074180900116018.
Full textAbstract:
We made a search of quiescent X-ray counterparts of two Gamma-Ray Bursts (GRBs), GRB930131 and GRB940217. These GRBs were detected with BATSE, EGRET, COMPTEL on board CGRO together with the GRB detector on Ulysses spacecraft, then they were localized in small error regions. These observations showed that the bursts were remarkably bright accompanying delayed high energy gamma-rays. ASCA observations have found a single X-ray source for each GRB on the possible location determined with the above instruments.
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Tunnicliffe, Rachel L., and Andrew Levan. "GRB 100816A and the nature of intermediate duration gamma-ray bursts." Proceedings of the International Astronomical Union 7, S279 (April 2011): 415–16. http://dx.doi.org/10.1017/s1743921312013610.
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AbstractGamma-ray bursts are normally split into two classes, primarily determined by their observed duration, so called long (> 2s) and short (< 2s) GRBs. There have been many claims of a third duration class, with emission lasting for intermediate periods between 2 - 5s, although the reality of this class remains controversial. Here, we investigate this further utilising the 2.9s duration, spectrally hard GRB 100816A. This burst lies well offset from its host galaxy, has no evidence for an associated supernova (albeit to only moderately constraining limits), and has properties which appear to be genuinely intermediate between long- and short- population bursts. We extend this analysis by comparing the physical locations of a population of intermediate duration GRBs with those of short-GRBs and long-GRBs, concluding that the intermediate sample is indistinguishable from the long-GRB population, whose locations are very different from other transients.
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Gendre, B., Q. T. Joyce, N. B. Orange, G. Stratta, J. L. Atteia, and M. Boër. "Can we quickly flag ultra-long gamma-ray bursts?" Monthly Notices of the Royal Astronomical Society 486, no. 2 (April 13, 2019): 2471–76. http://dx.doi.org/10.1093/mnras/stz1036.
Full textAbstract:
Abstract Ultra-long gamma-ray bursts are a class of high-energy transients lasting several hours. Their exact nature is still elusive, and several models have been proposed to explain them. Because of the limited coverage of wide-field gamma-ray detectors, the study of their prompt phase with sensitive narrow-field X-ray instruments could help in understanding the origin of ultra-long GRBs. However, the observers face a true problem in rapidly activating follow-up observations, due to the challenging identification of an ultra-long GRB before the end of the prompt phase. We present here a comparison of the prompt properties available after a few tens of minutes of a sample of ultra-long GRBs and normal long GRBs, looking for prior indicators of the long duration. We find that there is no such clear prior indicator of the duration of the burst. We also found that statistically, a burst lasting at least 10 and 20 minutes has respectively $28{{\ \rm per\ cent}}$ and $50{{\ \rm per\ cent}}$ probability to be an ultralong event. These findings point towards a common central engine for normal long and ultra-long GRBs, with the collapsar model privileged.
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Zhang, Z. B., and C. S. Choi. "The duration properties of Swift Gamma-Ray Bursts." Proceedings of the International Astronomical Union 4, S252 (April 2008): 431–32. http://dx.doi.org/10.1017/s1743921308023429.
Full textAbstract:
AbstractWe report the systematic analysis of the durations for Swift gamma-ray bursts (GRBs) and compare the results with those of pre-Swift data. We show that the durations of Swift bursts also have two log-normal distributions that are clearly divided at T90 = 2 s. Their intrinsic durations also show a bimodal distribution but shift systematically toward the smaller value compared with the observed one. This study confirms the spectra of short GRBs are in general harder than the long GRBs and shows that this trend becomes weak in the source frame.
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Deng, Q., Z. B. Zhang, X. J. Li, H. Y. Chang, X. L. Zhang, H. Y. Zhen, H. Sun, Q. Pan, and X. F. Dong. "Reclassifying Swift Gamma-Ray Bursts with Diverse Duration Distributions." Astrophysical Journal 940, no. 1 (November 1, 2022): 5. http://dx.doi.org/10.3847/1538-4357/ac9590.
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Abstract We select the largest sample of Swift gamma-ray bursts (GRBs) so far to reexamine the classification in terms of time duration, hardness ratio, and physical collapse model. To analyze the sample selection effect, we divide the observed Swift GRB sample into four subsamples according to signal-to-noise level, spectral quality, and extended emission. First, we find that only the sample of Swift GRBs with well-measured peak energy can be evidently divided into two types at a boundary of ∼1 s, and other data sets are well described by three Gaussian functions. Using Swift GRBs with known redshift, a Kolmogorov–Smirnov test shows the intrinsic duration distributions of five data sets are equally distributed. Second, we ascertain in the plane of hardness ratio versus duration that the hardness ratio of short GRBs is significantly higher than those of middle classes and long GRBs, while the latter two components are the same in statistics, implying the so-called middle class to be artificial. Third, we apply a collapse model to discriminate the boundaries between collapse and noncollapse Swift bursts. It is interesting to find that a significant fraction, ≥30%, of Swift short GRBs could have originated from the collapsing progenitors, while all long GRBs are produced from the collapsars only. Finally, we point out that short GRBs with extended emission are the main contributors to the noncollapsar population with longer duration.
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Woosley, S. E., and A. Heger. "Supernovae, Gamma-Ray Bursts and Stellar Rotation." Symposium - International Astronomical Union 215 (2004): 601–12. http://dx.doi.org/10.1017/s0074180900196275.
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One of the most dramatic possible consequences of stellar rotation is its influence on stellar death, particularly of massive stars. If the angular momentum of the iron core when it collapses is such as to produce a neutron star with a period of 5 ms or less, rotation will have important consequences for the supernova explosion mechanism. Still shorter periods, corresponding to a neutron star rotating at break up, are required for the progenitors of gamma-ray bursts (GRBs). Current stellar models, while providing an excess of angular momentum to pulsars, still fall short of what is needed to make GRBs. The possibility of slowing young neutron stars in ordinary supernovae by a combination of neutrino-powered winds and the propeller mechanism is discussed. The fall back of slowly moving ejecta during the first day of the supernova may be critical. GRBs, on the other hand, probably require stellar mergers for their production and perhaps less efficient mass loss and magnetic torques than estimated thus far.
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Zhang, Shuai, Lang Shao, Bin-Bin Zhang, Jin-Hang Zou, Hai-Yuan Sun, Yu-jie Yao, and Lin-lin Li. "A Tight Three-parameter Correlation and Related Classification on Gamma-Ray Bursts." Astrophysical Journal 926, no. 2 (February 1, 2022): 170. http://dx.doi.org/10.3847/1538-4357/ac4753.
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Abstract Gamma-ray bursts (GRBs) are widely believed to be from massive collapsars and/or compact binary mergers,which, accordingly, would generate long and short GRBs, respectively. The details on this classification scheme have been in constant debate given more and more observational data available to us. In this work, we apply a series of data mining methods to studying the potential classification information contained in the prompt emission of GRBs detected by the Fermi Gamma-ray Burst Monitor. A tight global correlation is found between fluence (f), peak flux (F), and prompt duration (T 90) which takes the form of log f = 0.75 log T 90 + 0.92 log F − 7.14 . Based on this correlation, we can define a new parameter L = 1.66 log T 90 + 0.84 log f − 0.46 log F + 3.24 by linear discriminant analysis that would distinguish between long and short GRBs with much less ambiguity than T 90. We also discussed the three subclasses scheme of GRB classification derived from clusters analysis based on a Gaussian mixture model, and suggest that, besides SGRBs, LGRBs may be divided into long-bright gamma-ray bursts (LBGRBs) and long-faint gamma-ray bursts (LFGRBs), LBGRBs have statistical higher f and F than LFGRBs; further statistical analysis found that LBGRBs also have higher number of GRB pulses than LFGRBs.
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Bucciantini, Niccolò. "Magnetars and Gamma Ray Bursts." Proceedings of the International Astronomical Union 7, S279 (April 2011): 289–96. http://dx.doi.org/10.1017/s1743921312013075.
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AbstractIn the last few years, evidences for a long-lived and sustained engine in Gamma Ray Bursts (GRBs) have increased the attention to the so called millisecond-magnetar model, as a competitive alternative to the standard collapsar scenario. I will review here the key aspects of the millisecond magnetar model for Long Duration Gamma Ray Bursts (LGRBs). I will briefly describe what constraints present observations put on any engine model, both in terms of energetics, outflow properties, and the relation with the associated Supernova (SN). For each of these I will show how the millisecond magnetar model satisfies the requirements, what are the limits of the model, how can it be further tested, and what observations might be used to discriminate against it. I will also discuss numerical results that show the importance of the confinement by the progenitor star in explaining the formation of a collimated outflow, how a detailed model for the evolution of the central engine can be built, and show that a wide variety of explosive events can be explained by different magnetar parameters. I will conclude with a suggestion that magnetars might be at the origin of the Extended Emission (EE) observed in a significant fraction of Short GRBs.
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Ghirlanda, G., F. Nappo, G. Ghisellini, A. Melandri, G. Marcarini, L. Nava, O. S. Salafia, S. Campana, and R. Salvaterra. "Bulk Lorentz factors of gamma-ray bursts." Astronomy & Astrophysics 609 (January 2018): A112. http://dx.doi.org/10.1051/0004-6361/201731598.
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Knowledge of the bulk Lorentz factor Γ0 of gamma-ray bursts (GRBs) allows us to compute their comoving frame properties shedding light on their physics. Upon collisions with the circumburst matter, the fireball of a GRB starts to decelerate, producing a peak or a break (depending on the circumburst density profile) in the light curve of the afterglow. Considering all bursts with known redshift and with an early coverage of their emission, we find 67 GRBs (including one short event) with a peak in their optical or GeV light curves at a time tp. For another 106 GRBs we set an upper limit tpUL. The measure of tp provides the bulk Lorentz factor Γ0 of the fireball before deceleration. We show that tp is due to the dynamics of the fireball deceleration and not to the passage of a characteristic frequency of the synchrotron spectrum across the optical band. Considering the tp of 66 long GRBs and the 85 most constraining upper limits, we estimate Γ0 or a lower limit Γ0LL. Using censored data analysis methods, we reconstruct the most likely distribution of tp. All tp are larger than the time Tp,γ when the prompt γ-ray emission peaks, and are much larger than the time Tph when the fireball becomes transparent, that is, tp>Tp,γ>Tph. The reconstructed distribution of Γ0 has median value ~300 (150) for a uniform (wind) circumburst density profile. In the comoving frame, long GRBs have typical isotropic energy, luminosity, and peak energy ⟨ Eiso ⟩ = 3(8) × 1050 erg, ⟨ Liso ⟩ = 3(15) × 1047 erg s-1, and ⟨ Epeak ⟩ = 1(2) keV in the homogeneous (wind) case. We confirm that the significant correlations between Γ0 and the rest frame isotropic energy (Eiso), luminosity (Liso), and peak energy (Ep) are not due to selection effects. When combined, they lead to the observed Ep−Eiso and Ep−Liso correlations. Finally, assuming a typical opening angle of 5 degrees, we derive the distribution of the jet baryon loading which is centered around a few 10-6M⊙.
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Vásconez, Christian, Nicolás Vásquez, and Ericson López. "Testing the bimodal distribution of long gamma-ray bursts in the cosmological rest-frame." Proceedings of the International Astronomical Union 8, S288 (August 2012): 298–99. http://dx.doi.org/10.1017/s1743921312017024.
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AbstractAmong the several methods of classifying gamma-ray bursts (GRBs), the duration parameter has lead to the canonical classification of GRBs of long and shorts. However, the canonical classification of bursts has recently seen the emergence of a third type of GRB, which is present in a recent large burst sample from the Swift observatory. The high redshifts and the cosmological distances are directly confirmed for long bursts only, while for the short ones there is only indirect evidence for their cosmological origin. Cosmological objects should not only be redshifted in energy but also extended in time because of the expansion of the Universe. Meanwhile, an anticorrelation between the hardness and the duration is found for this subclass in contrast to the short and the long groups (Horvath et al. (2010)). Despite the differences among these three groups, it is not yet clear whether the third group represents a physically different phenomenon. In this scenario, we want to study the bimodal distribution of long bursts, focusing their temporal properties in the source location (burst frame). We have determined a temporal estimator in the cosmological rest-frame from a sample of 60 Swift's GRBs. If GRBs are at cosmological distances, then the burst profiles should be stretched in time due to cosmological time dilation by an amount proportional to the redshift, 1 + z (Chang (2001)). Complementary, we use the hardness ratio between the soft emission (15–50keV) and hard X-ray emission (50–150keV) in order to analyze the bimodal distribution of long bursts in the time-energy plane.
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Bouwhuis, Mieke, Keith W. Bannister, Jean-Pierre Macquart, R. M. Shannon, David L. Kaplan, John D. Bunton, Bärbel S. Koribalski, and M. T. Whiting. "A search for fast-radio-burst-like emission from Fermi gamma-ray bursts." Monthly Notices of the Royal Astronomical Society 497, no. 1 (July 6, 2020): 125–29. http://dx.doi.org/10.1093/mnras/staa1889.
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ABSTRACT We report the results of the rapid follow-up observations of gamma-ray bursts (GRBs) detected by the Fermi satellite to search for associated fast radio bursts. The observations were conducted with the Australian Square Kilometre Array Pathfinder at frequencies from 1.2 to 1.4 GHz. A set of 20 bursts, of which four were short GRBs, were followed up with a typical latency of about 1 min, for a duration of up to 11 h after the burst. The data were searched using 4096 dispersion measure trials up to a maximum dispersion measure of 3763 pc cm−3, and for pulse widths w over a range of duration from 1.256 to 40.48 ms. No associated pulsed radio emission was observed above $26 \, {\rm Jy\, ms}\, (w/1\, {\rm ms})^{-1/2}$ for any of the 20 GRBs.