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jet breaks in gamma-ray burst (grb) afterglows provide a direct probe of their collimation angle. modeling a jet break requires an understanding of the jet spreading process, whereby the jet transitions from a collimated outflow into the spherical sedov-taylor solution at late times. currently, direct numerical calcula... | on the deceleration and spreading of relativistic jets. i. jet dynamics |
one of the most exciting near-term prospects in physics is the potential discovery of gravitational waves by the advanced ligo and virgo detectors. to maximize both the confidence of the detection and the science return, it is essential to identify an electromagnetic counterpart. this is not trivial, as the events are ... | optimization of the swift x-ray follow-up of advanced ligo and virgo gravitational wave triggers in 2015-16 |
the external forward shock emitting the gamma-ray burst (grb) afterglow is collisionless, and it is mediated by the weibel instability which generates the magnetic field. the grb afterglow shows that the magnetic field in the large downstream region is much stronger than the shock-compressed preshock field. however, pa... | weibel-mediated shocks propagating into inhomogeneous electron-positron plasmas |
we model the possible afterglow of the fermi gamma-ray burst monitor (gbm) event associated with ligo detection gw150914, under the assumption that the gamma-rays are produced by a short grb-like relativistic outflow. we model gw150914-gbm as both a weak, on-axis short grb and normal short grb seen far off-axis. given ... | modeling the afterglow of the possible fermi-gbm event associated with gw150914 |
we present optical photometry of the afterglow of the long grb 180205a with the coatli telescope from 217 s to about 5 days after the swift/bat trigger. we analyze this photometry in conjunction with the x-ray light curve from swift/xrt. the late-time light curves and spectra are consistent with the standard forward-sh... | late central-engine activity in grb 180205a |
multi-wave band synchrotron linear polarization of gamma-ray burst (grb) afterglows is studied under the assumption of an anisotropic turbulent magnetic field with a coherence length of the plasma skin-depth scale in the downstream of forward shocks. we find that for typical grbs, in comparison to optical polarization,... | multi-wave band synchrotron polarization of gamma-ray burst afterglows |
long-duration grb 200829a was detected by fermi-gbm and swift-bat/xrt, and then rapidly observed by other ground-based telescopes. it has a weak γ-ray emission in the very early phase and is followed by a bright spiky γ-ray emission pulse. the radiation spectrum of the very early emission is best fitted by a power-law ... | grb 200829a: external-shock origin of the very early prompt emission? |
in the past decades, an external forward shock model has been successfully developed to explain the main features of the afterglow emission of gamma-ray bursts (grbs). in the numerical modeling of the grb afterglow, some approximations have been made for simplicity, and different groups developed their codes. a robust ... | prospects of calibrating afterglow modeling of short grbs with gravitational wave inclination angle measurements and resolving the hubble tension with a gw-grb association event |
we collected the optical light-curve data of 227 gamma-ray bursts (grbs) observed with the tarot, coatli, and ratir telescopes. these consist of 133 detections and 94 upper limits. we constructed average light curves in the observer and rest frames in both x-rays (from swift/x-ray telescope) and the optical. our analys... | understanding the nature of the optical emission in gamma-ray bursts: analysis from tarot, coatli, and ratir observations |
prompt γ-ray and early x-ray afterglow emissions in gamma-ray bursts (grbs) are characterized by a bursty behavior and are often interspersed with long quiescent times. there is compelling evidence that x-ray flares are linked to prompt γ-rays. however, the physical mechanism that leads to the complex temporal distribu... | a common stochastic process rules gamma-ray burst prompt emission and x-ray flares |
the unusual multiwavelength lightcurves of grb 101225a are revisited by assuming that they are from an off-axis grb powered by a newborn magnetar. we show that grb 101225a's optical afterglow lightcurve is fitted with the forward shock model by parameterizing its jet structure as a gaussian function with a half-opening... | grb 101225a as orphan dipole radiation of a newborn magnetar with precession rotation in an off-axis gamma-ray burst |
the recent ligo/virgo detection of gravitational radiation from gw170817 bears the clear signature of a binary neutron star merger and has validated a number of theoretical predictions. high-energy radiation in the form of a short gamma-ray burst was observed 1.7 s following the merger, and an extended optical/infrared... | impact of gw170817 for the nuclear physics of the eos and the r-process |
we show the existence of two families of short gamma-ray bursts (grbs), both originating from the merger of binary neutron stars (nss): family-1 with {e}{iso}\lt {10}52 erg, leading to a massive ns as the merged core, and family-2 with {e}{iso}\gt {10}52 erg, leading to a black hole (bh). following the identification o... | grb 140619b: a short grb from a binary neutron star merger leading to black hole formation |
gamma-ray bursts (grbs) categorically produce broad-band afterglow emission, but in some cases, emission in the optical band is dimmer than expected based on the contemporaneously observed x-ray flux. this phenomenon, aptly dubbed 'optical darkness', has been studied extensively in long grbs (associated with the explos... | optical darkness in short-duration γ-ray bursts |
afterglows not associated with any gamma-ray bursts (grbs) are called orphan afterglows. the detection of such afterglows is an important goal in many sky survey programs. recently, a promising orphan afterglow candidate, at2021any, was found by the zwicky transient facility. in this work, we performed multi-wavelength... | possible origin of at2021any: a failed gamma-ray burst from a structured jet |
grb 190114c is an unusual gamma-ray burst (grb) due to its detection at sub-tev energies by magic, seen at redshift z = 0.42. this burst is one of the brightest grb detected by fermi. a joint gbm-lat analysis of the prompt emission reveals the presence of sub-gev spectral cutoff when the lat low-energy event (lle) data... | magical grb 190114c: implications of cutoff in the spectrum at sub-gev energies |
the mechanisms of particle acceleration and radiation, as well as magnetic field build-up and decay in relativistic collisionless shocks, are open questions with important implications to various phenomena in high-energy astrophysics. while the weibel instability is possibly responsible for magnetic field build-up and ... | particle acceleration, magnetization and radiation in relativistic shocks |
we present x-ray and multiband optical observations of the afterglow and host galaxy of grb 180418a, discovered by swift/bat and fermi/gbm. we present a reanalysis of the gbm and bat data deriving durations of the prompt emission of t90 ≈ 2.56 and 1.90 s, respectively. modeling the fermi/gbm catalog of 1405 bursts (200... | grb 180418a: a possibly short gamma-ray burst with a wide-angle outflow in a faint host galaxy |
gw170817 was the first ever joint detection of gravitational waves (gw) from a binary neutron star (bns) merger with the detections of short γ-ray burst (sgrb) counterparts. analysis of the multiband afterglow observations of over more than a year revealed that the outflow from the merger end product was consistent wit... | prospects of joint detections of neutron star mergers and short grbs with gaussian structured jets |
given an increasing number of gamma-ray bursts accompanied by potential kilonovae, there is a growing importance to advance modelling of kilonova afterglows. in this work, we investigate how the presence of two electron populations that follow a maxwellian (thermal) and a power-law (non-thermal) distribution affect kil... | modelling kilonova afterglows: effects of the thermal electron population and interaction with grb outflows |
we present the results of an intensive multi-epoch radio frequency campaign on the energetic and nearby grb 171010a with the karl g. janksy very large array and arcminute microkelvin imager large array. we began observing grb 171010a a day after its initial detection, and were able to monitor the temporal and spectral ... | a detailed radio study of the energetic, nearby, and puzzling grb 171010a |
we report in this work the creation of new heavy and efficient tb3al5o12:ce (tbag:ce) single crystalline film (scf) scintillators, grown by lpe method from pbo-b2o3 based flux onto y3al5o12 (yag) and gd3ga2.5al2.5o12 (gagg) substrates, for different optoelectronic applications. the luminescent and scintillation propert... | scintillating screens based on the lpe grown tb3al5o12:ce single crystalline films |
we present very early ground-based optical follow-up observations of gamma-ray burst (grb) 140423a, which was discovered by the swift/burst alert telescope (bat) and by the fermi/gamma-ray burst monitor. its broadband afterglow was monitored by the swift/x-ray telescope and ground-based optical telescopes from t0 + 70.... | grb 140423a: a case of stellar wind to interstellar medium transition in the afterglow |
context. the gamma-ray bursts hosts (grbhs) are excellent targets to study the extinction properties of dust and its effects on the global emission of distant galaxies. the dust extinction curve is measured along the grb afterglow line of sight and the analysis of the spectral energy distribution (sed) of the host gala... | investigation of dust attenuation and star formation activity in galaxies hosting grbs |
on 2011 march 28, the swift burst alert telescope triggered on an object that had no analog in over six years of swift operations. follow-up observations by the swift x-ray telescope (xrt) found a new, bright x-ray source covering three orders of magnitude in flux over the first few days, that was much more persistent ... | the definitive x-ray light curve of swift j164449.3+573451 |
we present time-resolved spectral analysis of the steep decay segments of 29 bright x-ray flares of gamma-ray bursts (grbs) observed with the swift/x-ray telescope, and model their light curves and spectral index evolution behaviors with the curvature effect model. our results show that the observed rapid flux decay an... | the history of grb outflows: ejection lorentz factor and radiation location of x-ray flares |
tidal disruption events (tdes) that occur in active galactic nuclei (agns) with dusty tori are a special class of sources. tdes can generate ultrafast and large opening-angle wind, which will almost inevitably collide with the pre-existing agn dusty tori a few years later after the tde outburst. the wind-torus interact... | years delayed gamma-ray and radio afterglows originated from tde wind-torus interactions |
the central engine of gamma-ray bursts (grbs) remains an open and cutting-edge topic in the era of multimessenger astrophysics. x-ray plateaus appear in some grb afterglows, which are widely considered to originate from the spindown of magnetars. according to the stable magnetar scenario of grbs, an x-ray plateau and a... | evidence of x-ray plateaus driven by the magnetar spindown winds in gamma-ray burst afterglows |
it has been observationally established that supernovae (sne) of type ic produce long duration gamma ray bursts (grbs) and that neutron star mergers generate short hard grbs. sn-less grbs presumably originate in a phase transition of a neutron star in a high mass x-ray binary. how these phenomena actually generate grbs... | critical tests of leading gamma ray burst theories ii |
we use joint observations by the swift x-ray telescope (xrt) and the fermi large area telescope (lat) of gamma-ray burst (grb) afterglows to investigate the nature of the long-lived high-energy emission observed by fermi lat. joint broadband spectral modeling of xrt and lat data reveals that lat nondetections of bright... | investigating the nature of late-time high-energy grb emission through joint fermi/swift observations |
thunderstorms are known to create terrestrial gamma ray flashes (tgfs) which are microsecond-long bursts created by runaway of thermal electrons from propagating lightning leaders, as well as gamma ray glows that possibly are created by relativistic runaway electron avalanches (rrea) that can last for minutes or more a... | tgf afterglows: a new radiation mechanism from thunderstorms |
high-redshift gamma-ray bursts (grbs) beyond redshift {∼}6 are potentially powerful tools to probe the distant early universe. their detections in large numbers and at truly high redshifts call for the next generation of high-energy wide-field instruments with unprecedented sensitivity at least one order of magnitude h... | perspectives on gamma-ray burst physics and cosmology with next generation facilities |
x-ray flares were discovered in the afterglow phase of gamma-ray bursts (grbs) by the swift satellite a decade ago and are known as a canonical component in grb x-ray afterglows. in this paper, we constrain the lorentz factors of grb x-ray flares using two different methods. for the first method, we estimate the lower ... | constraints on the bulk lorentz factors of grb x-ray flares |
we present a detailed prompt emission and early optical afterglow analysis of the two very-high-energy (vhe) detected bursts grb 201015a and grb 201216c, and their comparison with a subset of similar bursts. time-resolved spectral analysis of multistructured grb 201216c using the bayesian binning algorithm revealed tha... | prompt emission and early optical afterglow of very-high-energy detected grb 201015a and grb 201216c: onset of the external forward shock |
gamma-ray bursts (grbs), as extremely energetic explosions in the universe, are widely believed to consist of two stages: the prompt phase and the subsequent afterglow. recent studies indicate that some high-energy photons are emitted earlier at source than the prompt phase. due to the light speed variation, these high... | novel pre-burst stage of gamma-ray bursts from machine learning |
long-duration gamma-ray bursts (grbs) are generally related to the core-collapse of massive stars. in the collapsar scenario, a rotating stellar-mass black hole (bh) surrounded by a hyperaccretion disk has been considered as one of the plausible candidates of grb central engines. in this paper, we work on a sample incl... | testing blandford-znajek mechanism in black hole hyperaccretion flows for long-duration gamma-ray bursts |
the zwicky transient facility recently announced the detection of an optical transient at2020blt at redshift z = 2.9, consistent with the afterglow of an on-axis gamma-ray burst. however, no prompt emission was observed. we analyse at2020blt with detailed models, showing the data are best explained as the afterglow of ... | low-efficiency long gamma-ray bursts: a case study with at2020blt |
we present synthetic radio images of the grb 170817a afterglow, computed from moving-mesh hydrodynamic simulations of binary neutron star merger outflows. having expanded for nearly a year, the merger remnant is expected to subtend ∼5 mas on the sky, potentially resolvable by very long baseline radio imaging techniques... | radio sky maps of the grb 170817a afterglow from simulations |
the afterglow emission from gamma-ray bursts (grbs) is a valuable source of information to understand the physics of these energetic explosions. the fireball model has become the standard to describe the evolution of the afterglow emission over time and frequency. because of recent developments in the theory of aftergl... | a new approach to modelling gamma-ray burst afterglows: using gaussian processes to account for the systematics |
the prompt emission of the long, smooth, and single-pulsed gamma-ray burst, grb 141028a, is analyzed under the guise of an external shock model. first, we fit the γ-ray spectrum with a two-component photon model, namely, synchrotron+blackbody, and then fit the recovered evolution of the synchrotron νfνpeak to an analyt... | an external shock origin of grb 141028a |
the central engine and jet composition of gamma-ray bursts (grbs) remain mysterious. here we suggest that observations on the polarization evolution of early optical afterglows may shed light on these questions. we first study the dynamics of a reverse shock and a forward shock that are generated during the interaction... | polarization evolution of early optical afterglows of gamma-ray bursts |
we numerically simulate the gamma-ray burst (grb) afterglow emission with a one-zone time-dependent code. the temporal evolutions of the decelerating shocked shell and energy distributions of electrons and photons are consistently calculated. the photon spectrum and light curves for an observer are obtained taking into... | temporal evolution of the gamma-ray burst afterglow spectrum for an observer: gev-tev synchrotron self-compton light curve |
evidence for the central engine of gamma-ray bursts (grbs) has been collected in the neil gehrels swift data. for instance, some grbs show an internal x-ray plateau followed by very steep decay, which is difficult interpret within the framework of a black hole (bh) central engine, but is consistent within a rapidly spi... | the second plateau in x-ray afterglow providing additional evidence for rapidly spinning magnetars as the grb central engine |
the transition from prompt to afterglow emission is one of the most exciting and least understood phases in gamma-ray bursts (grbs). correlations among optical, x-ray, and gamma-ray emission in grbs have been explored, to attempt to answer whether the earliest optical emission comes from internal and/or external shocks... | modeling the prompt optical emission of grb 180325a: the evolution of a spike from the optical to gamma rays |
long gamma-ray bursts show an afterglow emission in the x-rays, optical, and radio wavelengths with luminosities that fade with time with a nearly identical power-law behavior. in this talk, i present an analytic treatment that shows that this afterglow is produced by synchrotron radiation from the supernova ejecta ass... | on the origin of the long gamma-ray burst afterglow as synchrotron radiation from binary-driven hypernovae |
we present optical and near-infrared (nir) photometric observations of grb 191016 with the coatli,ddoti, and ratir ground-based telescopes over the first three nights. we present the temporal evolution of the optical afterglow and describe five different stages that were not completely characterized in previous works, ... | grb 191016a: the onset of the forward shock and evidence of late energy injection |
we summarize the basic observational properties of gamma-ray bursts (grbs), including prompt emission properties, afterglow properties, and classification schemes. we also briefly comment on the current physical understanding of these properties. | grb observational properties |
polarization measurements from relativistic outflows are a valuable tool to probe the geometry of the emission region and the microphysics of the particle distribution. indeed, the polarization level depends on (i) the local magnetic field orientation, (ii) the geometry of the emitting region with respect to the line o... | linear and circular polarization in ultra-relativistic synchrotron sources - implications to grb afterglows |
we study the ensemble of linear polarization measurements in the optical afterglows of long-duration gamma-ray bursts. we assume a non-sideways-expanding top-hat jet geometry and use the relatively large number of measurements under the assumption that they represent a statistically unbiased sample. this allows us to c... | polarization constraints on the geometry of the magnetic field in the external shock of gamma-ray bursts |
early optical observations of gamma-ray bursts can significantly contribute to the study of the central engine and physical processes therein. however, of the thousands observed so far, only a few have data at optical wavelengths in the first minutes after the onset of the prompt emission. here we report on grb 190106a... | photometric and spectroscopic observations of grb 190106a: emission from reverse and forward shocks with late-time energy injection |
in this work, we study the distribution of temporal power-law decay indices, α, in the gamma-ray burst (grb) afterglow phase, fitted for 176 grbs (139 long grbs, 12 short grbs with extended emission, and 25 x-ray flashes) with known redshifts. these indices are compared with the temporal decay index, αw , derived with ... | study of grb light-curve decay indices in the afterglow phase |
we present new jansky very large array observations of five pre-swift gamma-ray bursts for which an ultraluminous [star formation rate (sfr) >100 m⊙ yr-1] dusty host galaxy had previously been inferred from radio or submillimetre observations taken within a few years after the burst. in four of the five cases, we no... | late-time vla reobservations rule out ulirg-like host galaxies for most pre- swift long-duration gamma-ray bursts |
we compute the linear polarization during the afterglow phase of gamma-ray bursts, for both on-axis and off-axis observers. we use numerical simulations of the deceleration of a relativistic jet, and compute the polarization by post-processing the results of the numerical simulations. in our simulations, we consider a ... | numerical simulations of polarization in gamma-ray burst afterglows |
binary neutron star (ns) mergers may result in remnants of supra-massive or even stable ns, which have been supported indirectly by observed x-ray plateau of some gamma-ray burst (grb) afterglows. recently, xue et al. (2019) discovered an x-ray transient cdf-s xt2 that is powered by a magnetar from merger of double ns ... | the electromagnetic and gravitational-wave radiations of x-ray transient cdf-s xt2 |
radiation transport codes are often used in astrophysics to construct spectral models. in this work, we demonstrate how producing these models for a time series of data can provide unique information about supernovae (sne). unlike previous work, we specifically concentrate on the method for obtaining the best synthetic... | extracting high-level information from gamma-ray burst supernova spectra |
emission from gamma-ray bursts is thought to be powered mainly by synchrotron radiation from energetic electrons. the same electrons might scatter these synchrotron seed photons to higher (>10 gev) energies, building a distinct spectral component (synchrotron self-compton, ssc). this process is expected to take plac... | gamma-ray bursts at the highest energies |
context. a total of four long-duration gamma-ray bursts (grbs) have been confirmed at very high-energy (≥100gev) with high significance, and any possible peculiarities of these bursts will become clearer as the number of detected events increases. multi-wavelength follow-up campaigns are required to extract information... | vlbi observations of grb 201015a, a relatively faint grb with a hint of very high-energy gamma-ray emission |
unveiling the mystery of gamma-ray bursts (grbs) has been the target of many multi-waveband observational and theoretical efforts during the last decades. the results collected by current and past space-based instruments have provided important insights into the mechanisms at the origin of their prompt and afterglow ph... | the detection of grbs at vhe: a challenge lasting for more than two decades, what is next? |
grb 030329 displays one clear and, possibly, multiple less intense fast-rising (δt/t ~ 0.3) jumps in its optical afterglow light curve. the decay rate of the optical light curve remains the same before and after the flux jumps. this may be the signature of energy injection into the shocked material at the front of the ... | the signature of refreshed shocks in the afterglow of grb 030329 |
for a sample of swift and fermi gamma-ray bursts, we show that the minimum variability timescale and the spectral lag of the prompt emission is related to the bulk lorentz factor in a complex manner. for small γ's, the variability timescale exhibits a shallow (plateau) region. for large γ's, the variability timescale d... | gamma-ray bursts: temporal scales and the bulk lorentz factor |
giant flares (gfs) are unusual bursts from soft gamma-ray repeaters (sgrs) that release an enormous amount of energy in a fraction of a second. the afterglow emission of these sgr-gfs or gf candidates is a highly beneficial means of discerning their composition, relativistic speed and emission mechanisms. grb 200415a i... | magnetar giant flare originating from grb 200415a: transient gev emission, time-resolved ep - l iso correlation and implications |
correlations between optical flashes and gamma-ray emissions in gamma-ray bursts (grbs) have been searched in order to clarify the question of whether these emissions occur at internal and/or external shocks. among the most powerful grbs ever recorded are grb 080319b and grb 130427a, which at early phases presented bri... | the origin of the optical flashes: the case study of grb 080319b and grb 130427a |
grb 170817a is the first short gamma-ray burst (grb) with direct detection of the gravitational-wave radiation and also the spectroscopically identified macronova emission (i.e., at 2017gfo). the prompt emission of this burst, however, is underluminous in comparison with the other short grbs with known redshift. in thi... | how special is grb 170817a? |
simultaneous swift and fermi observations of gamma-ray bursts (grbs) offer a unique broadband view of their afterglow emission, spanning more than 10 decades in energy. we present the sample of x-ray flares observed by both swift and fermi during the first three years of fermi operations. while bright in the x-ray band... | swift and fermi observations of x-ray flares: the case of late internal shock |
gamma-ray burst grb 140430a was detected by the swift satellite and observed promptly with the imaging polarimeter ringo3 mounted on the liverpool telescope, with observations beginning while the prompt γ-ray emission was still ongoing. in this paper, we present densely sampled (10-s temporal resolution) early optical ... | limits on optical polarization during the prompt phase of grb 140430a |
context. grb 210731a was a long-duration (t90 = 22.5 s) gamma-ray burst discovered by the burst alert telescope (bat) aboard the neil gehrels swift observatory. swift triggered the wide-field, robotic meerlicht optical telescope in sutherland; it began observing the bat error circle 286 s after the swift trigger and di... | the triple-peaked afterglow of grb 210731a from x-ray to radio frequencies |
the early optical emission of gamma-ray bursts (grbs) gives an opportunity to understand the central engine and first stages of these events. about 30% of grbs present flares whose origin is still a subject of discussion. we present optical photometry of grb 180620a with the coatli telescope and ratir instrument. coatl... | grb 180620a: evidence for late-time energy injection |
the current status of observations and theoretical models of gamma-ray bursts and some other related transients, including ultra-long bursts and tidal disruption events, is reviewed. we consider the impact of multi-wavelength data on the formulation and development of theoretical models for the prompt and afterglow emi... | gamma-ray bursts and fast transients. multi-wavelength observations and multi-messenger signals |
gw170817/grb 170817a probably marks a double neutron star (ns) coalescence. extended emission {t}s≃ (0.67+/- 0.03) s post-merger shows an estimated energy output { \mathcal e }≃ (3.5+/- 1) % {m}⊙ {c}2 determined by response curves to power-law signal injections, where c is the velocity of light. it provides calorimetri... | multi-messenger extended emission from the compact remnant in gw170817 |
grb 160325a is the only bright burst detected by astrosat czt imager in its primary field of view to date. in this work, we present the spectral and polarimetric analysis of the prompt emission of the burst using astrosat, fermi, and niel gehrels swift observations. the prompt emission consists of two distinct emission... | spectropolarimetric analysis of prompt emission of grb 160325a: jet with evolving environment of internal shocks |
we analyze the early growth stage of direct-collapse black holes (dcbhs) with ∼105 m ⊙, which are formed by collapse of supermassive stars in atomic-cooling halos at z ≳ 10. a nuclear accretion disk around a newborn dcbh is gravitationally unstable and fragments into clumps with a few × 10 m ⊙ at ∼0.01-0.1 pc from the ... | stellar tidal disruption events by direct-collapse black holes |
grb 160625b is an extremely bright outburst with well-monitored afterglow emission. the geometry-corrected energy is high, up to ∼5.2 × 1052 erg or even ∼8 × 1052 erg, rendering it the most energetic grb prompt emission recorded so far. we analyzed the time-resolved spectra of the prompt emission and found that in some... | evaluating the bulk lorentz factors of outflow material: lessons learned from the extremely energetic outburst grb 160625b |
during a compact binary merger involving at least one neutron star (ns), a small fraction of the gravitational energy could be liberated in such a way to accelerate a small fraction (∼10-6) of the ns mass in an isotropic or quasi-isotropic way. in presence of certain conditions, a pair-loaded fireball can form, which u... | jet-driven and jet-less fireballs from compact binary mergers |
this paper presents data on the simultaneous and complementary observations of the gamma-ray burst (grb) grb 161017a for optical, x-ray, and gamma wavelengths obtained by the russian multi-messenger lomonosov space observatory and supplemented by additional data from the swift satellite as well as the ground-based mast... | prompt and follow-up multi-wavelength observations of the grb 161017a |
intense flares that occur at late times relative to the prompt phase have been observed by the swift satellite in the x-ray afterglows of gamma-ray bursts (grbs). here, we present a detailed analysis on the fall back accretion process to explain the intense flare phase in the very early x-ray afterglow light curves. to... | fall back accretion and energy injections in gamma-ray bursts |
gamma-ray bursts (grbs) central engines and jet production mechanisms are still open questions. assuming that the shallow decay segments of canonical x-ray afterglow light curves of swift grbs are attributed to the magnetic dipole (md) radiations of newly born magnetars, we derive the parameters of the magnetars and ex... | magnetar as central engine of gamma-ray bursts: central engine-jet connection, wind-jet energy partition, and origin of some ultra-long bursts |
we report our observations of very bright prompt optical and reverse shock (rs) optical emission of grb 140512a and analyze its multi-wavelength data observed with the swift and fermi missions. it is found that the joint optical-x-ray-gamma-ray spectrum with our first optical detection (r = 13.09 mag) at {t}0+136 s dur... | very bright prompt and reverse shock emission of grb 140512a |
grb 140903a, a short duration γ-ray burst (sgrb) detected by swift, is characterized by its long-lasting radio emission among sgrbs. in addition to the ∼ {10}6 s radio afterglow emission, the afterglow of grb 140903a displays a plateau from 103 s to 7× {10}3 {{s}} in the x-rays. in this work, we attribute the x-ray pla... | the interpretation of the multi-wavelength afterglow emission of short grb 140903a |
the emission region of γ-ray bursts (grbs) is poorly constrained. the uncertainty on the size of the dissipation site spans over 4 orders of magnitude (1012-1017 cm) depending on the unknown energy composition of the grb jets. the joint multiband analysis from soft x-rays to high energies (up to ~1 gev) of one of the m... | constraints on the physics of the prompt emission from distant and energetic gamma-ray burst grb 220101a |
following the detection of a long grb 190919b by integral (international gamma-ray astrophysics laboratory), we obtained an optical photometric sequence of its optical counterpart. the light curve of the optical emission exhibits an unusually steep rise ∼100 s after the initial trigger. this behaviour is not expected f... | grb 190919b: rapid optical rise explained as a flaring activity |
a large-scale ordered magnetic field plays a very important role in the formation and acceleration of a gamma-ray burst (grb) jet. during the grb prompt phase, some dissipation processes may occur and disturb the magnetic field, making the field become random to some extent. therefore, a mixed magnetic field consisting... | polarization with a three-dimensional mixed magnetic field and its application to grb 170817a |
bimodal spectral energy distributions (seds) of gamma-ray burst (grb) afterglow of grbs 190114c, 130427a, and 180720b confirm that they are originated from the synchrotron emission (syn) and synchrotron self-compton scattering (ssc) process of electrons accelerated in the jets. the radiation mechanism and the physics o... | do afterglow synchrotron radiations follow the lp,iso-ep,z-γ0 relation of gamma-ray bursts? the cases of grbs 190114c, 130427a, and 180720b |
early afterglow observations of gamma-ray bursts (grbs) are valuable for exploring the properties of their jets and ambient medium. we report our photometric and spectroscopic observations of grb 210104a and discuss its jet properties with multiwavelength data. our spectroscopic observation reveals several absorption f... | photometric and spectroscopic observations of grb 210104a: bright reverse-shock emission and dense circumburst environment |
bright x-ray flares are routinely detected by the swift satellite during the early afterglow of gamma-ray bursts, when the explosion ejecta drives a blast wave into the external medium. we suggest that the flares are produced as the reverse shock propagates into the tail of the ejecta. the ejecta is expected to contain... | x-ray flares from dense shells formed in gamma-ray burst explosions |
we observed the afterglow of grb 130427a with the reionization and transients infrared camera (ratir) instrument on the 1.5 m harold l. johnson telescope of the observatorio astronómico nacional in sierra san pedro mártir. our homogenous grizy jh photometry extends from the night of the burst to three years later. we f... | photometric observations of supernova 2013cq associated with grb 130427a |
we present the light curves and spectra of 24 afterglows that have been monitored by fermi-lat at 0.1-100 gev over more than a decade. all light curves (except 130427) are consistent with a single power law starting from their peaks, which occur in most cases before the burst end. the light curves display a brightness-... | seven-year collection of well-monitored fermi-lat gamma-ray burst afterglows |
the multimessenger observation of gamma-ray burst (grb) 170817a from the nearby binary neutron star merger gw170817 demonstrated that low-energy gamma-ray emission can be observed at relatively large angles from grb jet axes. if such structured emission is typical, then the currently known sample of short grbs with no ... | radio forensics could unmask nearby off-axis gamma-ray bursts |
the broadband afterglow of gw170817/grb 170817a is believed to be from an off-axis structured jet. the central engine of a gamma-ray burst usually launches a pair of outflows that move oppositely. it is reasonable to consider the emission from double-sided structured jets, with a near-jet moving toward us and a counter... | late-time afterglow from double-sided structured jets: application to grb 170817a |
grb 201015a is a peculiarly low luminosity, spectrally soft gamma-ray burst (grb), with t90 = 9.8 ± 3.5 s (time interval of detection of 90 per cent of photons from the grb), and an associated supernova (likely to be type ic or ic-bl). grb 201015a has an isotropic energy $e_{\gamma , \rm iso}$$= 1.75 ^{+0.60} _{-0.53} ... | grb 201015a and the nature of low-luminosity soft gamma-ray bursts |
on 2017 august 17, advanced ligo and virgo observed gw170817, the first gravitational-wave (gw) signal from a binary neutron star merger. it was followed by a short-duration gamma-ray burst, grb 170817a, and by a non-thermal afterglow emission. in this work, a combined simultaneous fit of the electromagnetic (em, speci... | joint analysis of gravitational-wave and electromagnetic data of mergers: breaking an afterglow model degeneracy in gw170817 and in future events |
the brightness of the multi-wavelength afterglow of grb 170817a is increasing unexpectedly even ∼160 days after the associated gravitational burst. here we suggest that the brightening can be caused by a late-time energy injection process. we use an empirical expression to mimic the evolution of the injection luminosit... | continued brightening of the afterglow of gw170817/grb 170817a as being due to a delayed energy injection |
gamma-ray bursts have been widely argued to originate from binary compact object mergers or core collapse of massive stars. jets from these systems may have two components: an inner, narrow sub-jet and an outer, wider sub-jet. such a jet subsequently interacts with its ambient gas, leading to a reverse shock (rs) and a... | gamma-ray burst optical afterglows with two-component jets: polarization evolution revisited |
recent detection of sub-tev emission from gamma-ray bursts (grbs) represents a breakthrough in the grb study. the multiwavelength data of the afterglows of grb 190114c support the synchrotron self-compton (ssc) origin for its sub-tev emission. we present a comparative analysis on the ssc emission of grb afterglows in t... | very-high-energy emission and cascade radiation of gamma-ray burst afterglows: homogeneous versus wind external media |
a stellar-mass black hole (bh) surrounded by a neutrino-dominated accretion flow (ndaf) has been discussed in a number of works as the central engine of gamma-ray bursts (grbs). it is widely believed that ndaf cannot liberate enough energy for bright grbs. however, these works have been based on the assumption of a “no... | numerical and analytical solutions of neutrino-dominated accretion flows with a non-zero torque boundary condition and its applications in gamma-ray bursts |
the gamma-ray burst grb 180720b is very peculiar. on one hand, some interesting features have been found by performing the detailed time-resolved spectral analysis in the prompt phase. first, the “flux-tracking” pattern is exhibited both for the low energy spectral index α and the peak energy epin the band function. se... | origin for the prompt spectral evolution characteristics and high energy emission during the x-ray flare in grb 180720b |
tidal disruption events (tdes) occurring in active galactic nuclei (agns) are a special class of sources with outstanding scientific significance. tdes can generate ultrafast winds, which should almost inevitably collide with the preexisting agn dusty tori. we perform analytical calculations and simulations on the wind... | years-delayed x-ray afterglows of tdes originated from wind-torus interactions |
we report the detections of molecular hydrogen (h2), vibrationally-excited h2 (h2∗), and neutral atomic carbon (c i), an efficient tracer of molecular gas, in two new afterglow spectra of grbs 181020a (z = 2.938) and 190114a (z = 3.376), observed with x-shooter at the very large telescope (vlt). both host-galaxy absorp... | new constraints on the physical conditions in h2-bearing grb-host damped lyman-α absorbers |
we investigate signatures of population iii (popiii) stars in the metal-enriched environment of gamma-ray bursts (grbs) originating from population ii-i (popii/i) stars by using abundance ratios derived from numerical simulations that follow stellar evolution and chemical enrichment. we find that at z > 10 more than... | popiii signatures in the spectra of popii/i grbs |
the recently discovered rapid transient gn-z11-flash has been suggested to be the prompt-emission ultraviolet (uv) flash associated with a gamma-ray burst (grb) serendipitously exploding in the ultra-high-z galaxy gn-z11. we here place the flash into the context of the early uv emission of grbs, and find it is in agree... | gn-z11-flash in the context of gamma-ray burst afterglows |
we report the insight-hxmt observations on both the prompt emission and the afterglow of the record-breaking grb 221009a (gcn 32632, atel #15650). insight-hxmt is mainly composed of three x-ray telescopes: the high energy x-ray telescope (he, liu et al. 2022, scpma, 63, 249503), the medium energy x-ray telescope (me, c... | insight-hxmt observation on the prompt emission and afterglow of grb 221009a |
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