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The Fermi satellite has been reporting the detailed temporal properties of gamma-ray bursts (GRBs) in an extremely broad spectral range, 8 keV - 300 GeV, in particular, the unexpected delays of the GeV emission onsets behind the MeV…

High Energy Astrophysical Phenomena · Physics 2009-12-18 Kenji Toma , Xue-Feng Wu , Peter Meszaros

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…

High Energy Astrophysical Phenomena · Physics 2015-05-20 Amanda Maxham , Bin-Bin Zhang , Bing Zhang

Currently, the best available probe of the early phase of gamma-ray burst (GRB) jet attributes is the prompt gamma-ray emission, in which several intrinsic and extrinsic variables determine GRB pulse evolution. Bright, usually complex…

Astrophysics · Physics 2009-11-10 J. P. Norris , J. T. Bonnell , D. Kazanas , J. D. Scargle , J. Hakkila , T. W. Giblin

Gamma-ray bursts (GRBs) were first detected thanks to their prompt emission, which was the only information available for decades. In 2010, while the high-energy prompt emission remains the main tool for the detection and the first…

High Energy Astrophysical Phenomena · Physics 2015-03-19 Jean-Luc Atteia , Michel Boër

The emission mechanism of the gamma-ray bursts (GRBs) is still a matter of debates. The standard synchrotron energy spectrum of cooling electrons F_E ~ E^{-1/2} is much too soft to account for the majority of the observed spectral slopes.…

Astrophysics · Physics 2009-11-10 Boris E. Stern , Juri Poutanen

It has been recently argued that low-luminosity gamma-ray bursts (LL-GRBs) are likely a unique GRB population. Here, we present systematic analysis of the lightcurve characteristics from X-ray to gamma-ray energy bands for the two…

Astrophysics · Physics 2009-11-13 Fu-Wen Zhang

The prompt emission mechanism of gamma-ray bursts (GRBs) is still unclear, and the time-resolved spectral analysis of GRBs is a powerful tool for studying their underlying physical processes. We performed a detailed time-resolved spectral…

High Energy Astrophysical Phenomena · Physics 2024-01-29 Wan-Kai Wang , Wei Xie , Zhi-Fu Gao , Shuo Xiao , Ai-Jun Dong , Bin Zhang , Qi-Jun Zhi

We discuss the preliminary results of spectral analysis simulations involving anticipated correlated multi-wavelength observations of gamma-ray bursts (GRBs) using Swift's Burst Alert Telescope (BAT) and the Gamma-Ray Large Area Space…

Astrophysics · Physics 2009-11-13 Michael Stamatikos , Takanori Sakamoto , David L. Band

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…

High Energy Astrophysical Phenomena · Physics 2015-06-18 W. T. Vestrand , J. Wren , A. Panaitescu , P. Wozniak , H. Davis , D. Palmer , G. Vianello , N. Omodei , S. Xiong , M. Briggs , M. Elphick , W. Rosing

The prompt emission of the long, smooth, and single-pulsed gamma-ray burst, GRB $\textit{141028A}$, is analyzed under the guise of an external shock model. First, we fit the $\gamma$-ray spectrum with a two-component photon model, namely…

High Energy Astrophysical Phenomena · Physics 2016-05-25 J. Michael Burgess , Damien Bégué , Felix Ryde , Nicola Omodei , Asaf Pe'er , J. L. Racusin , A. Cucchiara

The Gamma Ray Burst (GRB) 180720B is one of the brightest events detected by the Fermi satellite and the first GRB detected by the H.E.S.S. telescope above 100 GeV. We analyse the Fermi (GBM and LAT) and Swift (XRT and BAT) data and…

High Energy Astrophysical Phenomena · Physics 2020-04-22 M. Ronchi , F. Fumagalli , M. E. Ravasio , G. Oganesyan , M. Toffano , O. S. Salafia , L. Nava , S. Ascenzi , G. Ghirlanda , G. Ghisellini

Instruments such as the ROTSE, TORTORA, Pi of the Sky, MASTER-net, and others have recorded single-band optical flux measurements of gamma-ray bursts starting as early as $\thicksim$ 10 seconds after gamma-ray trigger. The earliest…

High Energy Astrophysical Phenomena · Physics 2023-02-21 Toktarkhan Komesh , Bruce Grossan , Zhanat Maksut , Ernazar Abdikamalov , Maxim Krugov , George F. Smoot

We constrain the distance of the Gamma-Ray Burst (GRB) prompt emission site from the explosion centre, R, by determining the location of the electron's self absorption frequency in the GRB prompt optical-to-X/gamma-ray spectral energy…

High Energy Astrophysical Phenomena · Physics 2014-03-11 Rong-Feng Shen , Bing Zhang

Relations linking the temporal or/and spectral properties of the prompt emission of gamma-ray bursts (hereafter GRBs) to the absolute luminosity are of great importance as they both constrain the radiation mechanisms and represent potential…

High Energy Astrophysical Phenomena · Physics 2015-05-30 S. Boci , M. Hafizi , R. Mochkovitch

The spectral evolution characteristics of the prompt emission in gamma-ray bursts (GRBs) have been extensively studied, but detailed investigations of spectral evolution in a GRB flare remain lacking. In this work, we present the first…

The Space-based multiband astronomical Variable Objects Monitor (SVOM), detected its first short gamma-ray burst, GRB 240715A, in-flight, which was jointly observed by Fermi. Based on observational data of SVOM/GRM and Fermi/GBM, we perform…

The time-integrated polarization degree (PD) at prompt optical band of gamma-ray burst (GRB) was predicted to be less than $20\%$, while the time-resolved one can reach as high as $75\%$ in photosphere model. Polarizations in optical band…

High Energy Astrophysical Phenomena · Physics 2024-05-13 Jia-Sheng Li , Mi-Xiang Lan , Hao-Bing Wang

Four years after the launch the Swift satellite the nature of the Gamma Ray Bursts (GRBs) broadband afterglow behaviour is still an open issue ad the standard external shock fireball models cannot easily explain the puzzling combined…

High Energy Astrophysical Phenomena · Physics 2009-08-05 M. Nardini , G. Ghisellini , G. Ghirlanda , A. Celotti

We describe our attempt to determine if gamma-ray burst (GRB) and afterglow emissions could both arise in external shocks for simple GRBs--bursts consisting of just a few peaks in their lightcurves. We calculate peak flux and peak frequency…

Astrophysics · Physics 2016-08-30 E. McMahon , P. Kumar , A. Panaitescu

For a sample of Swift and Fermi GRBs, 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 $\Gamma$'s, the variability timescale…

High Energy Astrophysical Phenomena · Physics 2015-05-27 E. Sonbas , G. A. MacLachlan , K. S. Dhuga , P. Veres , A. Shenoy , T. N. Ukwatta