The multi-messenger observation of compact binary coalescence promises great scientific treasure. However, a synthetic observation from both gravitational wave and electromagnetic channels remains challenging. Relying on the day-to-week long macronova emission, GW170817 remains the only event with successful electromagnetic followup. In this manuscript, we explore the possibility of using the early stage X-ray afterglow to search for the electromagnetic counterpart of gravitational wave events. Two algorithms, the sequential observation and the local optimization are considered and applied to three simulated events. We consider the proposed Einstein probe as a candidate X-ray telescope. Benefiting from the large field of view and high sensitivity, we find that the sequential observation algorithm not only is easy to implement, but also promises a good chance of actual detection.
Assuming neutron star (NS) or neutron star/stellar-mass black hole (BH) mergers as progenitors of the short gamma ray bursts, we derive and demonstrate a simple analysis tool for modelling the efficiency of recovering on-axis optical afterglows triggered by a candidate gravitational wave event detected by the Advanced LIGO and Virgo network. The coincident detection efficiency has been evaluated for different classes of operating telescopes using observations of gamma ray bursts. We show how the efficiency depends on the luminosity distribution of the optical afterglows, the telescope features…
Thermal radiation, peaking in soft X-rays, has now been detected in a handful of GRB afterglows and has to date been interpreted as shock break-out of the GRB's progenitor star. We present a search for thermal emission in the early X-ray afterglows of a sample of Swift bursts selected by their brightness in X-rays at early times. We identify a clear thermal component in eight GRBs and track the evolution. We show that at least some of the emission must come from highly relativistic material since two show an apparent super-luminal expansion of the thermal component. Furthermore we determine ve…
Recently, Keane et al. reported the discovery of a fading radio transient following FRB 150418, and interpreted it as the afterglow of the FRB. Williams \& Berger, on the other hand, suggested that the radio transient is analogous to a group of variable radio sources, so that it could be a coincident AGN flare in the observational beam of the FRB. A new observation with VLA showed a re-brightening, which is consistent with the AGN picture. Here, using the radio survey data of Ofek et al., we statistically examine the chance coincidence probability to produce an event like the FRB 150418 transi…
Ultrarelativistic gamma-ray burst (GRB) jets are strong gravitational wave (GW) sources with memory-type signals. The plateau (or shallow decay) phases driven by the energy injection might appear in the early X-ray afterglows of GRBs. In this paper, we investigate the GW signal as well as X-ray afterglow emission in the framework of GRB jets with energy injection, and both short- and long-duration GRBs are considered. We find that, regardless of the case, because of the antibeaming and time delay effects, a rising slope emerging in the waveform of GW signal due to the energy injection lags far…
The nature of the shallow decay phase in the X-ray afterglow of the gamma-ray burst (GRB) is not yet clarified. We analyze the data of early X-ray afterglows of 26 GRBs triggered by Burst Alert Telescope onboard Neil Gehrels Swift Observatory and subsequently detected by Fermi Large Area Telescope (LAT) and/or Imaging Atmospheric Cherenkov Telescopes. It is found that 9 events (including 2 out of 3 very-high-energy gamma-ray events) have no shallow decay phase and that their X-ray afterglow light curves are well described by single power-law model except for the jet break at later epoch. The r…
Recently, ground-based Imaging Atmospheric Cherenkov Telescopes have reported the detection of very-high-energy (VHE) gamma-rays from some gamma-ray bursts (GRBs). One of them, GRB~190829A, was triggered by the Swift satellite, and about 20000 s after the burst onset the VHE gamma-ray emission was detected by H.E.S.S. with ~ 5 sigma significance. This event had unusual features of having much smaller isotropic equivalent gamma-ray energy than typical long GRBs and achromatic peaks in X-ray and optical afterglow at about 1400 s. Here we propose an off-axis jet scenario that explains these obser…
Compact object mergers are promising candidates for the progenitor system of short gamma-ray bursts (GRBs). Using gravitational wave (GW) triggers to identify a merger, any electromagnetic (EM) counterparts from the jet can be used to constrain the dynamics and structure of short GRB jets. GW triggered searches could reveal a hidden population of optical transients associated with the short-lived jets from the merger object. If the population of merger-jets is dominated by low-Lorentz-factors, then a GW triggered search will reveal the on-axis orphan afterglows from these failed GRBs. By consi…
Following the historical observation of GW170817 and its electromagnetic follow-up, new neutron star merger afterglows are expected to be observed as counterparts to gravitational wave signals during the next science runs of the gravitational interferometer network. The diversity of the observed population of afterglows of these future events is subject to various factors, which are (i) intrinsic, such as the energy of the ejecta, (ii) environmental, such as the ambient medium density or (iii) observational, such as the viewing angle and distance of the source. Through prescribing a population…
The optical emission of GRB 110205A is distinguished by two flares. In this work we examine two possible scenarios for the optical afterglow emission. In the first scenario, the first optical flare is the reverse shock emission of the main outflow and the second one is powered by the prolonged activity of central engine. We however find out that it is rather hard to interpret the late ($t>0.1$ day) afterglow data reasonably unless the GRB efficiency is very high ($\sim 0.95$). In the second scenario, the first optical flare is the low energy prompt emission and the second one is the reverse sh…
Following the historical observations of GW170817 and its multi-wavelength afterglow, more radio afterglows from neutron star mergers are expected in the future as counterparts to gravitational wave inspiral signals. We wish to describe these events using our current knowledge of the population of neutron star mergers coming from gamma-ray burst science, and taking into account the sensitivities of current and future gravitational wave and radio detectors. We combine analytical models for the merger gravitational wave and radio afterglow signals to a population model prescribing the energetics…
We verified the off-axis jet model of X-ray flashes (XRFs) and examined a discovery of off-axis orphan gamma-ray burst (GRBs) afterglows. The XRF sample was selected on the basis of the following three factors: (1) a constraint on the lower peak energy of the prompt spectrum $E^{src}_{obs}$, (2) redshift measurements, and (3) multi-color observations of an earlier (or brightening) phase. XRF020903 was the only sample selected basis of these criteria. A complete optical multi-color afterglow light curve of XRF020903 obtained from archived data and photometric results in literature showed an ach…
GRB 210731A was a long-duration 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 seconds after the Swift trigger and discovered the optical afterglow of GRB 210731A in its first 60-second q-band exposure. Multi-colour observations of the afterglow with MeerLICHT revealed a light curve that showed three peaks of similar brightness within the first four hours. We present the results of our follow-up campaign and int…
We present LOFAR imaging observations from the April/May 2020 active episode of magnetar SGR 1935+2154. We place the earliest radio limits on persistent emission following the low-luminosity fast radio burst FRB 200428 from the magnetar. We also perform an image-plane search for transient emission and find no radio flares during our observations. We examine post-FRB radio upper limits in the literature and find that all are consistent with the multi-wavelength afterglow predicted by the synchrotron maser shock model interpretation of FRB 200428. However, early optical observations appear to ru…
The X-ray afterglow of GRB 130831A shows an "internal plateau" with a decay slope of $\sim$ 0.8, followed by a steep drop at around $10^5$ s with a slope of $\sim$ 6. After the drop, the X-ray afterglow continues with a much shallower decay. The optical afterglow exhibits two segments of plateaus separated by a luminous optical flare, followed by a normal decay with a slope basically consistent with that of the late-time X-ray afterglow. The decay of the internal X-ray plateau is much steeper than what we expect in the simplest magnetar model. We propose a scenario in which the magnetar underg…
Fast radio bursts (FRBs) are radio transients lasting only about a few milliseconds. They seem to occur at cosmological distances. We propose that these events can be originated in the collapse of the magnetosphere of Kerr-Newman black holes (KNBHs). We show that the closed orbits of charged particles in the magnetosphere of these objects are unstable. After examining the dependencies on the specific charge of the particle and the spin and charge of the KNBH, we conclude that the resulting timescale and radiation mechanism fit well with the extant observations of FRBs. Furthermore, we argue th…
The early X-ray afterglow of gamma-ray bursts revealed by Swift carried many surprises. We focus in this paper on the plateau phase whose origin remains highly debated. We confront several newly discovered correlations between prompt and afterglow quantities (isotropic emitted energy in gamma-rays, luminosity and duration of the plateau) to several models proposed for the origin of plateaus in order to check if they can account for these observed correlations. We first show that the scenario of plateau formation by energy injection into the forward shock leads to an efficiency crisis for the p…
We investigate a model for the shallow decay phases of Gamma-ray Burst (GRB) afterglows discovered by Swift/XRT in the first hours following a GRB event. In the context of the fireball scenario, we consider the possibility that long-lived energy injection from a millisecond spinning, ultramagnetic neutron star (magnetar) powers afterglow emission during this phase. We consider the energy evolution in a relativistic shock subject to both radiative losses and energy injection from a spinning down magnetar in spherical symmetry. We model the energy injection term through magnetic dipole losses an…
To reveal and understand astrophysical processes responsible for the Gamma Ray Burst (GRB) phenomenon, it is crucial to discover and understand relations between their observational properties. The presented study is performed in the GRB rest frames and it uses a sample of 62 long GRBs from our sample of 77 Swift GRBs with known redshifts. Following the earlier analysis of the afterglow {\it characteristic luminosity $L^*_a$ -- break time $T^*_a$} correlation for a sample of long GRBs \citep{Dainotti2010} we extend it to correlations between the afterglow and the prompt emission GRB physical p…
Tidal torques from a binary black hole (BHBH) empty out the central regions in any circumbinary gaseous accretion disk. The balance between tidal torques and viscosity maintain the inner edge of the disk at a radius r ~ 1.5a -- 2a, where a is the binary semimajor axis. Eventually, the inspiraling binary decouples from disk and merges, leaving behind a central hollow ("donut hole") in the disk orbiting the remnant black hole. We present a simple, time-dependent, Newtonian calculation that follows the secular (viscous) evolution of the disk as it fills up the hollow down to the black hole innerm…
A planned rapid submillimeter (submm) Gamma Ray Burst (GRBs) follow-up observations conducted using the Greenland Telescope (GLT) is presented. The GLT is a 12-m submm telescope to be located at the top of the Greenland ice sheet, where the high-altitude and dry weather porvides excellent conditions for observations at submm wavelengths. With its combination of wavelength window and rapid responding system, the GLT will explore new insights on GRBs. Summarizing the current achievements of submm GRB follow-ups, we identify the following three scientific goals regarding GRBs: (1) systematic dete…
We introduce the Australia Telescope Compact Array (ATCA) rapid-response mode by presenting the first successful trigger on the short-duration gamma-ray burst (GRB) 181123B. Early-time radio observations of short GRBs may provide vital insights into the radio afterglow properties of Advanced LIGO- and Virgo-detected gravitational wave events, which will in turn inform follow-up strategies to search for counterparts within their large positional uncertainties. The ATCA was on target within 12.6 hr post-burst, when the source had risen above the horizon. While no radio afterglow was detected dur…
High-redshift gamma-ray bursts (GRBs) provide a powerful tool to probe the early universe, but still for relatively few do we have good observations of the afterglow. We here report the optical and near-infrared observations of the afterglow of a relatively high-redshift event, GRB\,220101A, triggered on New Year's Day of 2022. With the optical spectra obtained at XL2.16/BFOSC and NOT/ALFOSC, we determine the redshift of the burst at $z= 4.615$. Based on our optical and near-infrared data, combined with the X-ray data, we perform multiband fit with the python package \emph{afterglowpy}. A jet-…
We examine the the emission from optically bright gamma-ray burst (GRB) afterglows as the Ultraviolet and Optical Telescope (UVOT) on the Neil Gehrels Swift Observatory first begins observing, following the slew to target the GRB, while the pointing of the Swift satellite is still settling. We verify the photometric quality of the UVOT settling data using bright stars in the field of view. In the majority of cases we find no problems with the settling exposure photometry, but in one case we excise the first second of the exposure to mitigate a spacecraft attitude reconstruction issue, and in a…
Afterglows of gamma-ray bursts are observed to produce light curves with the flux following power law evolution in time. However, recent observations reveal bright flares at times on the order of minutes to days. One proposed explanation for these flares is the interaction of a relativistic blast wave with a circumburst density transition. In this paper, we model this type of interaction computationally in one and two dimensions, using a relativistic hydrodynamics code with adaptive mesh refinement called ram, and analytically in one dimension. We simulate a blast wave traveling in a stellar w…
Afterglows of gamma-ray bursts are observed to produce light curves with the flux following power law evolution in time. However, recent observations reveal bright flares at times on the order of minutes to days. One proposed explanation for these flares is the interaction of a relativistic blast wave with a circumburst density transition. In this paper, we model this type of interaction computationally in one and two dimensions, using a relativistic hydrodynamics code with adaptive mesh refinement called RAM, and analytically in one dimension. We simulate a blast wave traveling in a stellar w…
In the second work of this series, we explore the optimal search strategy for serendipitous and gravitational-wave-triggered target-of-opportunity (ToO) observations of kilonovae and optical short-duration gamma-ray burst (sGRB) afterglows from binary neutron star (BNS) mergers, assuming that cosmological kilonovae are AT2017gfo-like (but with viewing-angle dependence) and that the properties of afterglows are consistent with those of cosmological sGRB afterglows. A one-day cadence serendipitous search strategy with an exposure time of $\sim30\,$s can always achieve an optimal search strategy …
Swift observations suggest that the central compact objects of some gamma-ray bursts (GRBs) could be newly born millisecond magnetars. Therefore, by considering the spin evolution of the magnetars against r-mode instability, we investigate the role of the magnetars in GRB X-ray afterglow emission. Besides modifying the conventional energy injection model, we pay particular attention to the internal X-ray afterglow emission, whose luminosity is assumed to track the magnetic dipole luminosity of the magentars with a certain fraction. Following a comparison between the model and some selected obs…
First Results from the PanRadio Gamma-Ray Burst Collaboration: The 400-day Afterglow of GRB 230815A
David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto（多伦多大学天文学与天体物理系）；Dunlap Institute for Astronomy and Astrophysics, University of Toronto（多伦多大学邓普勒天文与天体物理研究所）；Racah Institute of Physics, The Hebrew University of Jerusalem（耶路撒冷希伯来大学拉卡物理研究所）；International Centre for Radio Astronomy Research, Curtin University（科廷大学国际射电天文研究中心）；Department of Physics, George Washington University（乔治华盛顿大学物理系）；Aix Marseille Université, CNRS, CNES, LAM（艾克斯马赛大学）；Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research（麻省理工学院卡弗里天体物理学与空间研究研究所）；Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México（墨西哥国立自治大学核科学研究所）；INAF - Osservatorio Astronomico di Brera（意大利国家天体物理研究所布雷拉天文台）
Broadband Modelling of GRB 230812B Afterglow: Implications for VHE $γ$-ray Detection with IACTs
Indian Institute of Technology Indore（印度印多尔理工学院）；Gran Sasso Science Institute（格兰萨索科学研究所）；INFN - Laboratori Nazionali del Gran Sasso（意大利国家核物理研究所-格兰萨索国家实验室）；INFN - Sezione di Padova（意大利国家核物理研究所帕多瓦分部）；INAF - Osservatorio Astronomica di Brera（意大利国家天体物理研究所布雷拉天文台）；INFN, Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）
GRB 230812B后glow的宽带建模揭示了VHE γ射线探测的重要性，展示了通过ICATs在不同波段识别光谱成分的潜力。
The fraction of long duration gamma ray bursts (GRBs) without an associated bright supernovae (SNe) at small redshifts $(z<0.15)$ is comparable to that of GRBs associated with SNe. We show, that their X-ray afterglow and the X-ray afterglow of most of the nearby $(z<1)$ GRBs without a confirmed association with SNe, are well reproduced by the launch of highly relativistic jets in the SN-less birth of millisecond pulsars in neutron star mergers or through phase transition of neutron stars to quark stars following mass accretion in compact binaries. Such a large fraction of GRBs with pulsar-like…
We present radio, optical/NIR, and X-ray observations of the afterglow of the short-duration 130603B, and uncover a break in the radio and optical bands at 0.5 d after the burst, best explained as a jet break with an inferred jet opening angle of 4-8 deg. GRB 130603B is only the third short GRB with a radio afterglow detection to date, and the first time that a jet break is evident in the radio band. We model the temporal evolution of the spectral energy distribution to determine the burst explosion properties and find an isotropic-equivalent kinetic energy of (0.6-1.7) x 10^51 erg and a circu…
Among the large variety of astrophysical sources that we can observe, gamma-ray bursts (GRBs) are the most energetic of the whole Universe. The definition of a general picture describing the physics behind GRBs has always been a compelling task, but the results obtained so far from observations have revealed a puzzling landscape. The lack of a clear, unique paradigm calls for further observations and additional, independent techniques for this purpose. Polarimetry constitutes a very useful example as it allows us to investigate some features of the source such as the geometry of the emitting r…
The detection of electromagnetic radiation (EM) accompanying the gravitational wave (GW) signal from the binary neutron star (BNS) merger GW170817 has revealed that these systems constitute at least a fraction of the progenitors of short gamma-ray bursts (SGRBs). As gravitational wave detectors keep pushing their detection horizons, it is important to assess coupled GW/EM probabilities, and how to maximize observational prospects. Here we perform population synthesis calculations of BNS evolution with the code MOBSE, and seed the binaries in galaxies at three representative redshifts (z=0.01,0…
We present multiwavelength observations of the afterglow of GRB 130427A, the brightest (in total fluence) gamma-ray burst of the past 29 years. Optical spectroscopy from Gemini-North reveals the redshift of the GRB to be z=0.340, indicating that its unprecedented brightness is primarily the result of its relatively close proximity to Earth; the intrinsic luminosities of both the GRB and its afterglow are not extreme in comparison to other bright GRBs. We present a large suite of multiwavelength observations spanning from 300 s to 130 d after the burst and demonstrate that the afterglow shows r…
In any given 24-hour period, the Fermi-LAT detects photons with energies of order 100 GeV not associated with any known VHE emitter. The RA/Dec of these photons frequently falls into the field of view of VERITAS the following evening. A single photon in the LAT can potentially mean many detectable photons on the ground due to the superior collection area of the IACT (Imaging Atmospheric Cherenkov Technique) method. During the 2011-2012 observing season, VERITAS implemented a new target-of-opportunity (ToO) program to trigger VERITAS observations on a small sample of the highest energy LAT phot…
We present the Arcminute Microkelvin Imager (AMI) Large Array catalogue of 139 gamma-ray bursts (GRBs). AMI observes at a central frequency of 15.7 GHz and is equipped with a fully automated rapid-response mode, which enables the telescope to respond to high-energy transients detected by Swift. On receiving a transient alert, AMI can be on-target within two minutes, scheduling later start times if the source is below the horizon. Further AMI observations are manually scheduled for several days following the trigger. The AMI GRB programme probes the early-time (< 1 day) radio properties of GRBs…
We present X-ray and optical observations of the short duration gamma-ray burst GRB 071227 and its host at $z=0.381$, obtained using \textit{Swift}, Gemini South and the Very Large Telescope. We identify a short-lived and moderately bright optical transient, with flux significantly in excess of that expected from a simple extrapolation of the X-ray spectrum at 0.2-0.3 days after burst. We fit the SED with afterglow models allowing for high extinction and thermal emission models that approximate a kilonova to assess the excess' origins. While some kilonova contribution is plausible, it is not f…
Gamma-ray bursts and their afterglows are thought to be produced by an ultra-relativistic jet. One of the most important open questions is the outflow composition: the energy may be carried out from the central source either as kinetic energy (of baryons and/or pairs), or in electromagnetic form (Poynting flux). While the total observable flux may be indistinguishable in both cases, its polarization properties are expected to differ markedly. The prompt emission and afterglow polarization are also a powerful diagnostic of the jet geometry. Again, with subtle and hardly detectable differences i…
The afterglow of gamma-ray burst - supernova connections
Università di Camerino（卡梅里诺大学）；Al-Farabi Kazakh National University（阿里-法拉比哈萨克国立大学）；INAF - Catania Astrophysical Observatory（意大利国家天体物理研究所卡塔尼亚天文台）；ICRANet（国际相对论天体物理中心网络）；State Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所粒子天体物理国家重点实验室）；ICRA, Dipartimento di Fisica, Sapienza Universitá di Roma（罗马智慧大学物理系ICRA研究中心）；ICRANet-AI（国际相对论天体物理中心人工智能）；INAF – Osservatorio Astronomico d’Abruzzo（意大利国家天体物理研究所阿布鲁佐天文台）
A number of gamma-ray bursts (GRBs) exhibit the late simultaneous bumps in their optical and Xray afterglows around the jet break. Its origin is unclear. Based on the following two facts, we suggest that this feature may sound a transition of circum-burst environment from a free-wind medium to a homogeneous medium. (I) The late bump followed by a steep decay is strongly reminiscent of the afterglows of GRB 170817A, which is attributed to an off-axis observed external-forward shock (eFS) propagating in an interstellar medium. (II) Observations seem to feature a long shallow decay before the lat…
A plateau phase in the X-ray afterglow is observed in a significant fraction of gamma-ray bursts (GRBs). Previously, it has been found that there exists a correlation among three key parameters concerning the plateau phase, i.e., the end time of the plateau phase in the GRB rest frame ($T_{a}$), the corresponding X-ray luminosity at the end time ($L_{X}$) and the isotropic energy of the prompt GRB ($E_{γ,\rm{iso}}$). In this study, we systematically search through all the \emph{Swift} GRBs with a plateau phase that occurred between 2005 May and 2018 August. We collect 174 GRBs, with redshifts …
Gamma-ray bursts (GRBs) are some of the most extreme events in the Universe. As well as providing a natural laboratory for investigating fundamental physical processes, they might trace the cosmic star formation rate up to extreme redshifts and probe the composition of the intergalactic medium over most of the Universe's history. Radio observations of GRBs play a key part in determining their physical properties, but currently they are largely limited to follow-up observations of $γ$-ray-detected objects. The SKA will significantly increase our ability to study GRB afterglows, following up sev…
GRB 240205B: A Reverse Shock Detected in Rapid Response Radio Observations
University of New Mexico（新墨西哥大学）；Texas Tech University（德克萨斯理工大学）；Australia Telescope National Facility, CSIRO（澳大利亚望远镜国家设施，CSIRO）；George Washington University（乔治华盛顿大学）；Trottier Space Institute at McGill（麦吉尔大学特罗蒂尔空间研究所）；McGill University（麦吉尔大学）；International Centre for Radio Astronomy Research, Curtin University（国际射电天文研究中心，科廷大学）；The University of Sydney（悉尼大学）；CSIRO Space and Astronomy（CSIRO空间与天文学）；ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)（ARC引力波发现卓越中心（OzGrav））；David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto（多伦多大学大卫·邓拉普天体物理学系）
Many short Gamma-Ray Bursts (sGRBs) have a prolonged plateau in the X-ray afterglow lasting up to tens of thousands of seconds. A central engine injecting energy into the remnant may fuel the plateau. A simple analytic model describing the interaction of the magnetized relativistic wind from a rapidly-rotating magnetar with the surrounding environment can reproduce X-ray plateaux and instantaneous spectra. The model is analogous to classic, well-established models of young supernova remnants and applies the underlying physics to sGRB remnants. The light curve and spectra produced by the model …
We present detailed simulations of black hole-neutron star (BH-NS) mergers kilonova and gamma-ray burst (GRB) afterglow and kilonova luminosity function, and discuss the detectability of electromagnetic (EM) counterpart in connection with gravitational wave (GW) detections, GW-triggered target-of-opportunity observations, and time-domain blind searches. The predicted absolute magnitude of the BH-NS kilonovae at $0.5\,{\rm days}$ after the merger falls in $[-10,-15.5]$. The simulated luminosity function contains the potential viewing-angle distribution information of the anisotropic kilonova em…
We present a catalog of early-time (~10^2-10^4s) photometry and polarimetry of all Gamma-Ray Burst (GRB) optical afterglows observed with RINGO2 imaging polarimeter on the Liverpool Telescope. For the 19 optical afterglows observed, the following 9 were bright enough to perform photometry and attempt polarimetry: GRB 100805A, GRB 101112A, GRB 110205A, GRB 110726A, GRB 120119A, GRB 120308A, GRB 120311A, GRB 120326A and GRB 120327A. We present multi-wavelength light curves for these 9 GRBs, together with estimates of their optical polarization degrees and/or limits. We carry out a thorough inves…
Gamma-ray bursts (GRBs) are extremely high-energy events that can be observed at very high redshift. In addition to gamma rays, they can emit in X-ray, optical, and sometimes radio wavelengths. Here, following the approach in Srinivasaragavan et al. (2020); Dainotti et al. (2021b,c), and Dainotti et al (2022, submitted), we consider 82 GRBs from Dainotti et al. (2022a) that have been observed in optical wavelengths and fitted with a broken power law (BPL). We consider the relations between the spectral and temporal indices (closure relations; CRs) according to the synchrotron forward-shock mod…
The binary neutron star merger gravitational-wave signal GW170817 was followed by three electromagnetic counterparts, including a kilonova arising from the radioactivity of freshly synthesized $r$-process elements in ejecta from the merger. Finding kilonovae after gravitational-wave triggers is crucial for (i) the search for further counterparts, such as the afterglow, (ii) probing the diversity of kilonovae and their dependence on the system's inclination angle, and (iii) building a sample for multi-messenger cosmology. During the third observing run of the gravitational-wave interferometer n…
We analyze the emission plateaus in the X-ray afterglow lightcurves of gamma-ray bursts (GRBs) and in the optical lightcurves of Type II superpernovae (SNe IIP) in order to study whether they have similar late energy injection behaviors. We show that correlations of bolometric energies (or luminosities) between the prompt explosions and the plateaus for the two phenomena are similar. The Type II SNe are in the low energy end of the GRBs. The bolometric energies (or luminosities) in prompt phase E_{\rm expl} (or L_{\rm expl}) and in plateau phase E_{\rm plateau} (or L_{\rm plateau}) share relat…
The final inspiral of double neutron star and neutron star-black hole binaries are likely to be detected by advanced networks of ground-based gravitational wave (GW) interferometers. Maximizing the science returns from such a discovery will require the identification and localization of an electromagnetic (EM) counterpart. Here we critically evaluate and compare several possible counterparts, including short-duration gamma-ray bursts (SGRBs), "orphan" optical and radio afterglows, and ~day-long optical transients powered by the radioactive decay of heavy nuclei synthesized in the merger ejecta…
