Unveiling the origin of X-ray flares in gamma-ray bursts

Chincarini, G.; Mao, J.; Margutti, R.; Bernardini, M. G.; Guidorzi, C.; Pasotti, F.; Giannios, Dimitrios; Valle, M. Della; Moretti, A.; Romano, P.; D’Avanzo, P.; Cusumano, G.; Giommi, P.

doi:10.1111/j.1365-2966.2010.17037.x

Cited by 179 publications

(300 citation statements)

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“…Because we are mainly interested in the behaviour of the underlying afterglow, the Gaussian function representing the flares was chosen for simplicity, and no physical meaning is attributed to them. A more detailed analysis of flaring activity in this and other events is reported in Chincarini et al (2010). Liang et al (2008) claimed a possible identification of a break in the Swift-XRT light-curve.…”

Section: Swift-xrtmentioning

confidence: 71%

Challenging gamma-ray burst models through the broadband dataset of GRB 060908

Covino¹,

Campana²,

Conciatore

et al. 2010

A&A

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Context. Multiwavelength observations of gamma-ray burst prompt and afterglow emission are a key tool to separate the various possible emission processes and scenarios proposed to interpret the complex gamma-ray burst phenomenology. Aims. We collected a large dataset on GRB 060908 in order to carry out a comprehensive analysis of the prompt emission as well as the early and late afterglow. Methods. Data from Swift-BAT, -XRT and -UVOT together with data from a number of different ground-based optical/near-infrared and millimeter telescopes allowed us to follow the afterglow evolution after about a minute from the high-energy event down to the host galaxy limit. We discuss the physical parameters required to model these emissions. Results. The prompt emission of GRB 060908 was characterised by two main periods of activity, spaced by a few seconds of low intensity, with a tight correlation between activity and spectral hardness. Observations of the afterglow began less than one minute after the high-energy event, when it was already in a decaying phase, and it was characterised by a rather flat optical/near-infrared spectrum which can be interpreted as due to a hard energy-distribution of the emitting electrons. On the other hand, the X-ray spectrum of the afterglow could be fit by a rather soft electron distribution. Conclusions. GRB 060908 is a good example of a gamma-ray burst with a rich multi-wavelength set of observations. The availability of this dataset, built thanks to the joint efforts of many different teams, allowed us to carry out stringent tests for various interpretative scenarios, showing that a satisfactorily modelling of this event is challenging. In the future, similar efforts will enable us to obtain optical/near-infrared coverage comparable in quality and quantity to the X-ray data for more events, therefore opening new avenues to progress gamma-ray burst research.

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Section: Swift-xrtmentioning

confidence: 71%

Challenging gamma-ray burst models through the broadband dataset of GRB 060908

Covino¹,

Campana²,

Conciatore

et al. 2010

A&A

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“…Also, the X-ray flares [see e.g. 97] in the early afterglow phase may be a signature of late internal shocks [98], which may drive turbulence. Unless R 10 15 cm (corresponding to a few seconds for the flare duration), the photopion production due to X-ray flares is not efficient enough to cool the UHECRs [99].…”

Section: Acceleration Site and Possible Neutrino Emissionmentioning

confidence: 99%

Ultrahigh-energy cosmic ray production by turbulence in gamma-ray burst jets and cosmogenic neutrinos

Asano

Mészáros

2016

Phys. Rev. D

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We propose a novel model to produce ultra-high-energy cosmic-rays (UHECRs) in gamma-ray burst (GRB) jets. After the prompt gamma-ray emission, hydrodynamical turbulence is excited in the GRB jets at or before the afterglow phase. The mildly relativistic turbulence stochastically accelerates protons. The acceleration rate is much slower than the usual first-order shock acceleration rate, but in this case it can be energy-independent. The resultant UHECR spectrum is so hard that the bulk energy is concentrated in the highest energy range, resulting in a moderate requirement for the typical cosmic ray luminosity of ∼ 10 53.5 erg s −1 . In this model, the secondary gamma-ray and neutrino emissions initiated by photopion production are significantly suppressed. Although the UHECR spectrum at injection shows a curved feature, this does not conflict with the observed UHECR spectral shape. The cosmogenic neutrino spectrum in the 10 17 -10 18 eV range becomes distinctively hard in this model, which may be verified by future observations.

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“…Thanks to the rapid-response capability and high sensitivity of the Swift satellite 17 , numerous unforeseen features have been discovered, one of which is that about half of the bursts have large, late-time X-ray flares with short rise and decay times 4,5 . Unexpected X-ray flares with an isotropicequivalent energy from 10 48 to 10 52 ergs have been detected for both long and short bursts 4,6,7 . The occurrence times of X-ray flares range from a few seconds to 10 6 seconds after the GRB trigger 8 .…”

mentioning

confidence: 97%

“…In particular, we compare the statistical properties of the energy release, duration-time and waiting-time distributions of GRB X-ray flares and solar flares. For X-ray flares of GRBs with known redshifts, we employ published and archival observed data that allow us to estimate the energy release, duration time and waiting time of each X-ray flare [4][5][6][7][8] . The total number of flares is 83, including 9 short-burst flares and 74 long-burst flares.…”

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confidence: 99%

Self-organized criticality in X-ray flares of gamma-ray-burst afterglows

2013

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X-ray flares detected in nearly half of gamma-ray-burst (GRB) afterglows are one of the most intriguing phenomena in highenergy astrophysics 1-8 . All of the observations indicate that the central engines of bursts, after the gamma-ray emission has ended, still have long periods of activity, during which energetic explosions eject relativistic materials, leading to late-time X-ray emission 2,9,10 . It is thus expected that X-ray flares provide important clues as to the nature of the central engines of GRBs, and more importantly, unveil the physical mechanism of the flares themselves, which has so far remained mysterious. Here we report statistical results of X-ray flares of GRBs with known redshifts, and show that X-ray flares and solar flares share three statistical properties: power-law frequency distributions for energies, durations and waiting times. All of the distributions can be well understood within the physical framework of a self-organized criticality (SOC) system. The statistical properties of X-ray flares of GRBs are similar to solar flares, and thus both can be attributed to a SOC process. Both types of flares may be driven by a magnetic reconnection process, but X-ray flares of GRBs are produced in ultra-strongly magnetized millisecond pulsars 11,12 or long-term hyperaccreting disks around stellar-mass black holes 13 .GRBs are flashes of gamma-rays occurring at cosmological distances with an isotropic-equivalent energy release from 10 51 to 10 54 ergs 9,10,14,15 . They can be sorted into two classes: shortduration hard-spectrum bursts (< 2 s) and long-duration softspectrum bursts 16 . Thanks to the rapid-response capability and high sensitivity of the Swift satellite 17 , numerous unforeseen features have been discovered, one of which is that about half of the bursts have large, late-time X-ray flares with short rise and decay times 4,5 . Unexpected X-ray flares with an isotropicequivalent energy from 10 48 to 10 52 ergs have been detected for both long and short bursts 4,6,7 . The occurrence times of X-ray flares range from a few seconds to 10 6 seconds after the GRB trigger 8 . Until now, the physical mechanism of X-ray flares has remained mysterious, although some models have been proposed 9,10 . Due to the 8-year observations of Swift, plentiful X-ray flare data have been collected. Here we investigate the frequency distributions of energies, durations and waiting times of GRB X-ray flares for the first time. On the other hand, it is well known that solar flares with a timescale of hours are explosive phenomena in the solar atmosphere with an energy release of about 10 28 -10 32 ergs, which are widely believed to be triggered by a magnetic reconnection process 18 . They have been observed in broadband electromagnetic waves, but we focus here on solar hard X-ray flares.Although X-ray flares are common phenomena in GRBs and the Sun, the flare energy spans about 20 orders of magnitude and an outstanding question appears, namely, do GRB X-ray flares and solar flares have a similar physical mechani...

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Unveiling the origin of X-ray flares in gamma-ray bursts

Cited by 179 publications

References 86 publications

Challenging gamma-ray burst models through the broadband dataset of GRB 060908

Challenging gamma-ray burst models through the broadband dataset of GRB 060908

Ultrahigh-energy cosmic ray production by turbulence in gamma-ray burst jets and cosmogenic neutrinos

Self-organized criticality in X-ray flares of gamma-ray-burst afterglows

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