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We revisit the physical origin of the achromatic peaks and breaks observed several thousand seconds after the burst in the multi-wavelength afterglows of XRF 080330 and GRB 080710. Using a numerical afterglow model that consistently…

High Energy Astrophysical Phenomena · Physics 2026-03-13 Kaori Obayashi , Ryo Yamazaki , Yo Kusafuka , Katsuaki Asano

We develop a model to explain the flaring activity in gamma-ray burst X-ray afterglows within the framework of slightly misaligned observers to structured jets. We suggest that flares could be the manifestation of prompt dissipation within…

High Energy Astrophysical Phenomena · Physics 2022-04-20 Raphaël Duque , Paz Beniamini , Frédéric Daigne , Robert Mochkovitch

The afterglow of a gamma-ray burst (GRB) is commonly thought to be due to continuous deceleration of a relativistically expanding fireball in the surrounding medium. Assuming that the expansion of the fireball is adiabatic and that the…

Astrophysics · Physics 2009-10-30 Z. G. Dai , T. Lu

We present a possible theoretical interpretation of the observed afterglow emission of long gamma-ray burst GRB 080710. While its prompt GRB emission properties are normal, the afterglow light curves in the optical and infrared bands are…

High Energy Astrophysical Phenomena · Physics 2024-01-10 Kaori Obayashi , Ayumu Toriyama , Mayu Murakoshi , Yuri Sato , Shuta J. Tanaka , Takanori Sakamoto , Ryo Yamazaki

We present prompt gamma-ray, early NIR/optical, late optical and X-ray observations of the peculiar GRB 070311 discovered by INTEGRAL, in order to gain clues on the mechanisms responsible for the prompt gamma-ray pulse as well as for the…

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…

High Energy Astrophysical Phenomena · Physics 2015-06-15 Mette Friis , Darach Watson

We use a large sample of GRB afterglow and prompt-emission data (adding further GRB afterglow observations in this work) to compare the optical afterglows (or the lack thereof) of Type I GRBs with those of Type II GRBs. In comparison to the…

We show that the absence of the bright optical flashes in most {\it Swift} Gamma-ray Burst (GRB) afterglows can be explained, if the reverse shock region is magnetized with a $\sigma \sim 1$, or the emission spectrum of the electrons…

Astrophysics · Physics 2009-11-13 Yi-Zhong Fan

In the internal shock scenario for GRBs we expect some fraction of the energy of the burst to be carried by slow moving shells that were ejected at late times. These slow shells collide with faster moving outer shells when the outer shells…

Astrophysics · Physics 2009-10-31 Pawan Kumar , Tsvi Piran

Based on recent models of relativistic jet formation by thermal energy deposition around black hole-torus systems, the relation between the on- and off-axis appearance of short, hard gamma-ray bursts (GRBs) is discussed in terms of…

Astrophysics · Physics 2009-11-13 H. -Th. Janka , M. -A. Aloy , P. A. Mazzali , E. Pian

We call "prompt" emission of Gamma Ray Bursts (GRBs) the erratic and violent phase of hard X-ray and soft gamma-ray emission, usually lasting for tens of seconds in long GRBs. However, the central engine of GRBs may live much longer.…

Cosmology and Nongalactic Astrophysics · Physics 2009-08-07 G. Ghisellini , M. Nardini , G. Ghirlanda

We discuss the prompt emission of the gamma-ray burst (GRB) 990510 and its subsequent X-ray afterglow from 8.0 to 44.3 hrs after the prompt emission, using observations with the Gamma-ray Burst Monitor and Narrow Field Instruments on…

Recent observations of the environments of gamma-ray bursts (GRBs) favour massive stars as their progenitors, which are likely to be surrounded by gas and dust. The visibility of the optical and UV emission of a GRB are expected to depend…

Astrophysics · Physics 2009-11-06 B. P. Venemans , A. W. Blain

(abridged) Afterglow light curves are constructed analytically for realistic gamma-ray burst remnants decelerating in either a homogeneous interstellar medium or a stellar wind environment, taking into account the radiative loss of the…

Astrophysics · Physics 2009-11-10 X. F. Wu , Z. G. Dai , Y. F. Huang , T. Lu

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

We present Follow-Up Network for Gamma-Ray Bursts (FUN GRB) Collaboration observations of the optical afterglow of GRB 021211 made between 143 seconds and 102 days after the burst. Our unique data set includes the earliest filtered…

The Swift XRT has been observing GRB afterglows since December 23, 2004. Three-quarters of these observations begin within 300 s of the burst onset, providing an unprecendented look at the behavior of X-ray emission from GRB afterglows in…

The interaction between the relativistic jet and the circumburst medium produces a multiwavelength afterglow of a gamma-ray burst (GRBs). In this work, we present multiwavelength properties of GRB~250101A based on the observations of Swift,…

Most GRB X-ray afterglow light curves are characterised by a plateau, followed by a normal power-law decay interpreted as afterglow emission. Despite the numerous alternative interpretations, the origin of the plateau remains unclear. In…

High Energy Astrophysical Phenomena · Physics 2025-11-12 C. Guidorzi , R. Maccary , M. Maistrello , S. Kobayashi , M. Bulla , F. Frontera

The power-law decay of the X-ray emission of GRB afterglows 050319, 050401, 050607, 050713A, 050802 and 050922C exhibits a steepening at about 1--4 hours after the burst which, surprisingly, is not accompanied by a break in the optical…

Astrophysics · Physics 2010-03-19 A. Panaitescu , P. Meszaros , D. Burrows , J. Nousek , N. Gehrels , P. O'Brien , R. Willingale