scholarly journals Probing the Environment in Gamma‐Ray Bursts: The Case of an X‐Ray Precursor, Afterglow Late Onset, and Wind Versus Constant Density Profile in GRB 011121 and GRB 011211

2005 ◽  
Vol 623 (1) ◽  
pp. 314-324 ◽  
Author(s):  
L. Piro ◽  
M. De Pasquale ◽  
P. Soffitta ◽  
D. Lazzati ◽  
L. Amati ◽  
...  
Keyword(s):  
Density Profile ◽  
Gamma Ray ◽  
Late Onset ◽  
Gamma Ray Bursts ◽  
Constant Density ◽  
X Ray

scholarly journals Late Afterglow Bump/Plateau around the Jet Break: Signature of a Free-to-shocked Wind Environment in Gamma-Ray Burst

2021 ◽  
Vol 922 (1) ◽  
pp. 22
Author(s):  
Xiao-Yan Li ◽  
Da-Bin Lin ◽  
Jia Ren ◽  
Shu-Jin Hou ◽  
Yu-Fei Li ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Jet Flow ◽  
Gamma Ray Bursts ◽  
Constant Density ◽  
Viewing Angle ◽  
Wind Environment ◽  
X Ray ◽  
Forward Shock ◽  
Characteristic Angle ◽  
Steep Decay

Abstract A number of gamma-ray bursts (GRBs) exhibit the simultaneous bumps in their optical and X-ray afterglows around the jet break. These bumps are similar to the afterglows of GRB 170817A, except preceded by a long shallow decay. Its origin is unclear. We suggest that these late simultaneous bumps may sound a transition of circumburst environment from a free-wind medium to a constant density medium, e.g., the shocked-wind medium. In this paper, we study the emission of an external-forward shock propagating in a free-to-shocked wind environment at different viewing angles. The late simultaneous bumps/plateaux followed by a steep decay are found in the optical and X-ray afterglows for high-viewing-angle observers. In addition, these theoretical bumps are preceded by a long plateau or shallow decay, which is formed during the external-forward shock propagating in the free-wind environment. For low-viewing-angle observers, the above bumps also appear but only in the situation where the structured jet has a low characteristic angle and the deceleration radius of the in-core jet flow is at around or beyond the free-wind boundary. We search GRBs for afterglows with the late simultaneous optical and X-ray bumps followed by a steep decay. GRBs 120326A, 100901A, 100814A, and 120404A are obtained. We find that an off-core (in-core) observed external-forward shock in a free-to-shocked wind environment can well explain the optical and X-ray afterglows in GRBs 120326A, 100901A, and 100814A (GRB 120404A).

The X-ray luminosity function of short gamma-ray bursts

2021 ◽  
Vol 366 (4) ◽  
Author(s):  
Zhi-Ying Liu ◽  
Fu-Wen Zhang ◽  
Si-Yuan Zhu
Keyword(s):  
Luminosity Function ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
X Ray

scholarly journals Interpreting the X-ray afterglows of gamma-ray bursts with radiative losses and millisecond magnetars

2020 ◽  
Vol 499 (4) ◽  
pp. 5986-5992
Author(s):  
Nikhil Sarin ◽  
Paul D Lasky ◽  
Gregory Ashton
Keyword(s):  
Gravitational Wave ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Dipole Radiation ◽  
X Ray ◽  
Radiative Efficiency ◽  
Central Engine ◽  
Radiative Losses ◽  
Wave Emission ◽  
Prompt Emission

ABSTRACT The spin-down energy of millisecond magnetars has been invoked to explain X-ray afterglow observations of a significant fraction of short and long gamma-ray bursts. Here, we extend models previously introduced in the literature, incorporating radiative losses with the spin-down of a magnetar central engine through an arbitrary braking index. Combining this with a model for the tail of the prompt emission, we show that our model can better explain the data than millisecond-magnetar models without radiative losses or those that invoke spin-down solely through vacuum dipole radiation. We find that our model predicts a subset of X-ray flares seen in some gamma-ray bursts. We can further explain the diversity of X-ray plateaus by altering the radiative efficiency and measure the braking index of newly born millisecond magnetars. We measure the braking index of GRB061121 as $n=4.85^{+0.11}_{-0.15}$ suggesting the millisecond-magnetar born in this gamma-ray burst spins down predominantly through gravitational-wave emission.

scholarly journals Optical Afterglows as Probes for the Central Engine and Fireball of Gamma-Ray Bursts

2012 ◽  
Vol 8 (S290) ◽  
pp. 263-264
Author(s):  
Liang Li ◽  
En-Wei Liang ◽  
He Gao ◽  
Bing Zhang
Keyword(s):  
Statistical Analysis ◽  
Gamma Rays ◽  
Density Profile ◽  
Gamma Ray ◽  
Ambient Medium ◽  
Gamma Ray Bursts ◽  
Prompt Gamma ◽  
Medium Density ◽  
Central Engine ◽  
Prompt Emission

AbstractWell-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are compiled from literature. We identify possible emission components based on our empirical fits and present statistical analysis for these components. We find that the flares are related to prompt emission, suggesting that they could have the same origin in different episodes. The shallow decay segment is not correlated with prompt gamma-rays. It likely signals a long-lasting injected wind from GRB central engines. Early after onset peak is closely related with prompt emission. The ambient medium density profile is likely n ∝ r−1. No correlation between the late re-brightening bump and prompt gamma-rays or the onset bump is found. They may be from another jet component.

scholarly journals Diverse Features of the Multiwavelength Afterglows of Gamma-Ray Bursts: Natural or Special?

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
J. J. Geng ◽  
Y. F. Huang
Keyword(s):  
Black Holes ◽  
Numerical Method ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Shock Model ◽  
Reverse Shock ◽  
X Ray ◽  
Electron Positron ◽  
Forward Shock ◽  
Electron Positron Pair

The detection of optical rebrightenings and X-ray plateaus in the afterglows of gamma-ray bursts (GRBs) challenges the generic external shock model. Recently, we have developed a numerical method to calculate the dynamics of the system consisting of a forward shock and a reverse shock. Here, we briefly review the applications of this method in the afterglow theory. By relating these diverse features to the central engines of GRBs, we find that the steep optical rebrightenings would be caused by the fall-back accretion of black holes, while the shallow optical rebrightenings are the consequence of the injection of the electron-positron-pair wind from the central magnetar. These studies provide useful ways to probe the characteristics of GRB central engines.

scholarly journals Statistical Study of the Swift X-Ray Flash and X-Ray Rich Gamma-Ray Bursts

2018 ◽  
Vol 866 (2) ◽  
pp. 97 ◽  
Author(s):  
Xiongwei Bi ◽  
Jirong Mao ◽  
Chuanxi Liu ◽  
Jin-Ming Bai
Keyword(s):  
Statistical Study ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
X Ray

Swift observations of gamma-ray bursts

2007 ◽  
Vol 365 (1854) ◽  
pp. 1119-1128 ◽  
Author(s):  
Neil Gehrels
Keyword(s):  
Gamma Ray ◽  
High Redshift ◽  
Gamma Ray Bursts ◽  
Optical Observations ◽  
Nearby Galaxy ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Other Information ◽  
Short Grbs

Since its launch on 20 November 2004, the Swift mission has been detecting approximately 100 gamma-ray bursts (GRBs) each year, and immediately (within approx. 90 s) starting simultaneous X-ray and UV/optical observations of the afterglow. It has already collected an impressive database, including prompt emission to higher sensitivities than BATSE, uniform monitoring of afterglows and a rapid follow-up by other observatories notified through the GCN. Advances in our understanding of short GRBs have been spectacular. The detection of X-ray afterglows has led to accurate localizations and the conclusion that short GRBs can occur in non-star-forming galaxies or regions, whereas long GRBs are strongly concentrated within the star-forming regions. This is consistent with the NS merger model. Swift has greatly increased the redshift range of GRB detection. The highest redshift GRBs, at z ∼5–6, are approaching the era of reionization. Ground-based deep optical spectroscopy of high redshift bursts is giving metallicity measurements and other information on the source environment to a much greater distance than other techniques. The localization of GRB 060218 to a nearby galaxy, and the association with SN 2006aj, added a valuable member to the class of GRBs with detected supernova.

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