Gamma-ray burst theory after Swift

2007 ◽  
Vol 365 (1854) ◽  
pp. 1151-1162 ◽  
Author(s):  
Tsvi Piran ◽  
Yi-Zhong Fan
Keyword(s):  
Blast Wave ◽  
Gamma Ray ◽  
Wave Model ◽  
Gamma Ray Bursts ◽  
Light Curves ◽  
Smooth Transition ◽  
Host Galaxies ◽  
Optical Telescope ◽  
X Ray ◽  
Prompt Emission

Afterglow observations in the pre-Swift era confirmed to a large extend the relativistic blast wave model for gamma-ray bursts (GRBs). Together with the observations of properties of host galaxies and the association with (type Ic) SNe, this has led to the generally accepted collapsar origin of long GRBs. However, most of the afterglow data was collected hours after the burst. The X-ray telescope and the UV/optical telescope onboard Swift are able to slew to the direction of a burst in real time and record the early broadband afterglow light curves. These observations, and in particular the X-ray observations, resulted in many surprises. While we have anticipated a smooth transition from the prompt emission to the afterglow, many observed that early light curves are drastically different. We review here how these observations are changing our understanding of GRBs.

Optical/UV afterglows: Swift UVOT overview

2007 ◽  
Vol 365 (1854) ◽  
pp. 1227-1234 ◽  
Author(s):  
Keith O Mason ◽  
Patricia Boyd ◽  
Mathew Page ◽  
Shashi Pandey ◽  
Pete Roming ◽  
...  
Keyword(s):  
Light Curve ◽  
Spectral Data ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Nearby Galaxy ◽  
Host Galaxies ◽  
Optical Telescope ◽  
X Ray ◽  
Diagnostic Power ◽  
Peculiar Case

The ultraviolet and optical telescope (UVOT) on Swift provides coverage of gamma-ray bursts and their afterglows in the 170–650 nm band, yielding multiwavelength data of considerable diagnostic power in conjunction with the Swift X-ray Telescope. The results from the first eighteen months of operation show a broad range of afterglow behaviour, with considerably more complexity in many bursts than would be expected from the simple fireball model for the explosion. We briefly illustrate the capabilities of UVOT for measuring the evolution of nearby supernovae by reference to the observations of GRB 060218, and discuss the peculiar case of GRB 060614, which apparently resides in a nearby galaxy but which did not show the expected supernova feature in its light curve due to radioactive nickel decay. We discuss how the combination of X-ray and UV/optical spectral data can be used to investigate the environment of GRB host galaxies.

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 Constraints on the circumburst environments of short gamma-ray bursts

2020 ◽  
Vol 495 (4) ◽  
pp. 4782-4799 ◽  
Author(s):  
Brendan O’Connor ◽  
Paz Beniamini ◽  
Chryssa Kouveliotou
Keyword(s):  
Gamma Ray ◽  
Galactic Halo ◽  
Gamma Ray Bursts ◽  
Light Curves ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Binary Neutron Star ◽  
Range Of Values ◽  
Short Grbs

ABSTRACT Observational follow up of well localized short gamma-ray bursts (SGRBs) has left $20\!-\!30{{\ \rm per\ cent}}$ of the population without a coincident host galaxy association to deep optical and NIR limits (≳26 mag). These SGRBs have been classified as observationally hostless due to their lack of strong host associations. It has been argued that these hostless SGRBs could be an indication of the large distances traversed by the binary neutron star system (due to natal kicks) between its formation and its merger (leading to an SGRB). The distances of GRBs from their host galaxies can be indirectly probed by the surrounding circumburst densities. We show that a lower limit on those densities can be obtained from early afterglow light curves. We find that ${\lesssim}16{{\ \rm per\ cent}}$ of short GRBs in our sample took place at densities ≲10−4 cm−3. These densities represent the expected range of values at distances greater than the host galaxy’s virial radii. We find that out of the five SGRBs in our sample that have been found to be observationally hostless, none are consistent with having occurred beyond the virial radius of their birth galaxies. This implies one of two scenarios. Either these observationally hostless SGRBs occurred outside of the half-light radius of their host galaxy, but well within the galactic halo, or in host galaxies at moderate to high redshifts (z ≳ 2) that were missed by follow-up observations.

X‐Ray Light Curves of Gamma‐Ray Bursts Detected with the All‐Sky Monitor on RXTE

2002 ◽  
Vol 141 (2) ◽  
pp. 415-428 ◽  
Author(s):  
D. A. Smith ◽  
A. Levine ◽  
H. Bradt ◽  
K. Hurley ◽  
M. Feroci ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Light Curves ◽  
X Ray ◽  
Sky Monitor

scholarly journals Statistical Analyses of the Energies of X-Ray Plateaus and Flares in Gamma-Ray Bursts

2022 ◽  
Vol 924 (2) ◽  
pp. 69
Author(s):  
Shuang-Xi Yi ◽  
Mei Du ◽  
Tong Liu
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Physical Origin ◽  
Radiation Mechanisms ◽  
Gaussian Distributions ◽  
Emission Energy ◽  
X Ray ◽  
Central Engine ◽  
Positive Correlations ◽  
Prompt Emission

Abstract Distinct X-ray plateau and flare phases have been observed in the afterglows of gamma-ray bursts (GRBs), and most of them should be related to central engine activities. In this paper, we collect 174 GRBs with X-ray plateau phases and 106 GRBs with X-ray flares. There are 51 GRBs that overlap in the two selected samples. We analyze the distributions of the proportions of the plateau energy E plateau and the flare energy E flare relative to the isotropic prompt emission energy E γ,iso. The results indicate that they well meet the Gaussian distributions and the medians of the logarithmic ratios are ∼−0.96 and −1.39 in the two cases. Moreover, strong positive correlations between E plateau (or E flare ) and E γ,iso with slopes of ∼0.95 (or ∼0.80) are presented. For the overlapping sample, the slope is ∼0.80. We argue that most of X-ray plateaus and flares might have the same physical origin but appear with different features because of the different circumstances and radiation mechanisms. We also test the applicabilities of two models, i.e., black holes surrounded by fractured hyperaccretion disks and millisecond magnetars, on the origins of X-ray plateaus and flares.

scholarly journals X-ray plateaus in gamma-ray bursts’ light curves from jets viewed slightly off-axis

2020 ◽  
Vol 492 (2) ◽  
pp. 2847-2857 ◽  
Author(s):  
Paz Beniamini ◽  
Raphaël Duque ◽  
Frédéric Daigne ◽  
Robert Mochkovitch
Keyword(s):  
Gamma Ray ◽  
Large Fraction ◽  
Gamma Ray Bursts ◽  
Point Of View ◽  
Light Curves ◽  
Late Time ◽  
X Ray ◽  
Narrow Region ◽  
Central Engine ◽  
Γ Rays

ABSTRACT Using multiple observational arguments, recent work has shown that cosmological gamma-ray bursts (GRBs) are typically viewed at angles within, or close to the cores of their relativistic jets. One of those arguments relied on the lack of tens-of-days-long periods of very shallow evolution that would be seen in the afterglow light curves of GRBs viewed at large angles. Motivated by these results, we consider that GRBs efficiently produce γ-rays only within a narrow region around the core. We show that, on these near-core lines of sight, structured jets naturally produce shallow phases in the X-ray afterglow of GRBs. These plateaus would be seen by a large fraction of observers and would last between 102–105 s. They naturally reproduce the observed distributions of time-scales and luminosities as well as the intercorrelations between plateau duration, plateau luminosity, and prompt γ-ray energy. An advantage of this interpretation is that it involves no late-time energy injection which would be both challenging from the point of view of the central engine and, as we show here, less natural given the observed correlations between plateau and prompt properties.

scholarly journals Indication of Two Classes in the Swift Short Gamma-Ray Bursts from the XRT X-Ray Afterglow Light Curves

2009 ◽  
Author(s):  
T. Sakamoto ◽  
N. Gehrels ◽  
Charles Meegan ◽  
Chryssa Kouveliotou ◽  
Neil Gehrels
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Light Curves ◽  
X Ray

scholarly journals UNDERLYING GLOBAL FEATURES OF THE X-RAY LIGHT CURVES OF SWIFT GAMMA-RAY BURSTS

2010 ◽  
Vol 719 (2) ◽  
pp. L172-L176 ◽  
Author(s):  
Lang Shao ◽  
Yi-Zhong Fan ◽  
Da-Ming Wei
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Light Curves ◽  
Global Features ◽  
X Ray
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