Related papers: Modeling the early multiwavelength emission in GRB…
The extended high-energy gamma-ray (>100 MeV) emission which occurs well after the prompt gamma-ray bursts (GRBs) is usually explained as the afterglow synchrotron radiation. Here we report the analysis of the Fermi Large Area Telescope…
GRB 131231A was detected by the Large Area Telescope onboard Fermi Space Gamma-ray Telescope. The high energy gamma-ray ($> 100$ MeV) afterglow emission spectrum is $F_\nu \propto \nu^{-0.54\pm0.15}$ in the first $\sim 1300$ s after the…
Recent observations of Gamma-Ray Bursts (GRBs) by the Fermi Large Area Telescope (LAT) revealed a power law decay feature of the high energy emission (above 100 MeV), which led to the suggestion that it originates from a (probably…
The brightest Gamma-ray burst, GRB 221009A, has spurred numerous theoretical investigations, with particular attention paid to the origins of ultra-high energy TeV photons during the prompt phase. However, analyzing the mechanism of…
Fermi/LAT has detected long-lasting high-energy photons (>100 MeV) from gamma-ray bursts (GRBs), with the highest energy photons reaching about 100 GeV. One proposed scenario is that they are produced by high-energy electrons accelerated in…
We present a complete analysis of Fermi Large Area Telescope (LAT) data of GRB 221009A, the brightest Gamma-Ray Burst (GRB) ever detected. The burst emission above 30 MeV detected by the LAT preceded by 1 s the low-energy (< 10 MeV) pulse…
The dominant component of the (100 MeV - 50 GeV) GRB emission detected by LAT starts with a delay relative to the prompt soft (sub-MeV) gamma-rays and lasts long after the soft component fades. This has lead to the intriguing suggestion…
Recently, GRB 221009A, known as the brightest of all time (BOAT), has been observed across an astounding range of $\sim 18$ orders of magnitude in energy, spanning from radio to VHE bands. Notably, the Large High Altitude Air Shower…
We present the simultaneous Swift and Fermi observations of the bright GRB100728A and its afterglow. The early X-ray emission is dominated by a vigorous flaring activity continuing until 1 ks after the burst. In the same time interval high…
The detection in 10 bursts of an optical counterpart emission (i.e. during the prompt GRB phase) that is 10-10000 brighter than the extrapolation of the burst spectrum to optical frequencies suggests a synchrotron self-Compton origin for…
We present broadband (radio, optical, X-ray and GeV) fits to the afterglow light curves and spectra of three long-duration gamma-ray bursts (GRBs 080916C, 090902B, and 090926A) detected by the Gamma-Ray Burst Monitor (GBM) and Large Area…
We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. The early-time observations reveal multiple emission components that evolve independently, with a…
The optical light that is generated simultaneously with the x-rays and gamma-rays during a gamma-ray burst (GRB) provides clues about the nature of the explosions that occur as massive stars collapse to form black holes. We report on the…
We calculate the high energy (sub-GeV to TeV) prompt and afterglow emission of GRB 080319B that was distinguished by a naked-eye optical flash and by an unusual strong early X-ray afterglow. There are three possible sources for high energy…
The synchrotron optical flash caught in GRB 990123 overlaps with the MeV radiation front, and the optical-emitting electrons must also produce GeV-TeV emission by inverse Compton scattering of MeV photons. The ultra-high-energy flash can be…
Despite more than fifty years of gamma-ray burst (GRB) observations, several questions regarding the origin of the prompt emission, particularly at high energies, remain unresolved. We present a comprehensive analysis of 35 GRBs observed by…
One of the most energetic gamma-ray bursts GRB 110731A, was observed from optical to GeV energy range by Fermi and Swift Observatories, and by the MOA and GROND optical telescopes. The multiwavelength observations over different epochs…
We report on a new time-resolved analysis of the GRB 090926A broad-band spectrum during its prompt phase, and on its interpretation in the framework of prompt emission models. We characterize the high-energy extra component of GRB 090926A…
We study the emission of the short/hard GRB 090510 at energies > 0.1 GeV as observed by the Large Area Telescope (LAT) onboard the Fermi satellite. The GeV flux rises in time as t^2 and decays as t^-1.5 up to 200 s. The peak of the high…
The physical origin of the >0.1 GeV emission detected from Gamma-Ray Bursts (GRBs) by the Fermi satellite has not yet been completely understood. In this work we consider the GeV light curves of ten GRBs with measured redshift detected by…