Effects of a low electron distribution cutoff on multiwavelength spectra and light curves of GRB afterglows

Πετροπούλου, Μαρία; Mastichiadis, A.; Piran, Tsvi

doi:10.1051/0004-6361/201016088

Cited by 14 publications

(14 citation statements)

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“…Additionally, we have demonstrated that a flattening or rebrightening segment in the forward shock light curve is expected in the case of purely Maxwellian electron injection in a waveband where the observed flux gradually becomes dominated by the inverse Compton component, as described by Petropoulou et al (2011). Such flattenings are observed in a large fraction of X-ray light curves, but their physical origin is still under debate.…”

Section: Discussionmentioning

confidence: 89%

“…It is notable that a flattening or a slight rebrightening appears in all the cases with a Maxwellian electron injection. The flat segment is produced when the synchrotron component moves out of the observed energy range and is gradually replaced by the inverse Compton emission, similarly as described by Petropoulou et al (2011), who simulated the external shock emission from powerlaw electrons with a narrow energy distribution. A similar effect is also seen in the simulations of Stern & Poutanen (2004).…”

Section: Emission From a Maxwellian Distribution Of Injected Electronsmentioning

confidence: 99%

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Simulations of gamma-ray burst afterglows with a relativistic kinetic code

Pennanen

Vurm

Poutanen

2014

A&A

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Aims. This paper introduces a kinetic code that simulates gamma-ray burst (GRB) afterglow emission from the external forward shock and presents examples of some of its applications. One interesting research topic discussed in the paper is the high-energy radiation produced by Compton scattering of the prompt GRB photons against the shock-accelerated electrons. The difference between the forward shock emission in a wind-type and a constant-density medium is also studied, and the emission due to Maxwellian electron injection is compared to the case with pure power-law electrons. Methods. The code calculates the time-evolving photon and electron distributions in the emission region by solving the relativistic kinetic equations for each particle species. For the first time, the full relativistic equations for synchrotron emission/absorption, Compton scattering, and pair production/annihilation were applied to model the forward shock emission. The synchrotron self-absorption thermalization mechanism, which shapes the low-energy end of the electron distribution, was also included in the electron equation. Results. The simulation results indicate that inverse Compton scattering of the prompt GRB photons can produce a luminous TeV emission component, even when pair production in the emission region is taken into account. This very high-energy radiation may be observable in low-redshift GRBs. The test simulations also show that the low-energy end of a pure power-law distribution of electrons can thermalize owing to synchrotron self-absorption in a wind-type environment, but without an observable impact on the radiation spectrum. Moreover, a flattening in the forward shock X-ray light curve may be expected when the electron injection function is assumed to be purely Maxwellian instead of a power law. The flux during such a flattening is likely to be lower than the Swift/XRT sensitivity in the case of a constant-density external medium, but a wind environment may result in a higher flux during the shallow decay.

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Section: Discussionmentioning

confidence: 89%

Section: Emission From a Maxwellian Distribution Of Injected Electronsmentioning

confidence: 99%

Simulations of gamma-ray burst afterglows with a relativistic kinetic code

Pennanen

Vurm

Poutanen

2014

A&A

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“…Possible models include late-time energy injection [111,113,114], long-lasting central engine activity [115,116], time dependence of shock microphysics [117,118], viewing angle effects [119,120], shock coasting in a wind medium [121], or contribution from SSC emission [122]. These predict different high-energy emission signatures (e.g.…”

Section: Physics Of Grbsmentioning

confidence: 99%

Gamma-ray burst science in the era of the Cherenkov Telescope Array

Inoue

Granot

O’Brien

et al. 2013

Astroparticle Physics

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We outline the science prospects for gamma-ray bursts (GRBs) with the Cherenkov Telescope Array (CTA), the next-generation ground-based gamma-ray observatory operating at energies above few tens of GeV. With its low energy threshold, large effective area and rapid slewing capabilities, CTA will be able to measure the spectra and variability of GRBs at multi-GeV energies with unprecedented photon statistics, and thereby break new ground in elucidating the physics of GRBs, which is still poorly understood. Such measurements will also provide crucial diagnostics of ultra-high-energy cosmic ray and neutrino production in GRBs, advance observational cosmology by probing the high-redshift extragalactic background light and intergalactic magnetic fields, and contribute to fundamental physics by testing Lorentz invariance violation with high precision. Aiming to quantify these goals, we present some simulated observations of GRB spectra and light curves, together with estimates of their detection rates with CTA. Although the expected detection rate is modest, of order a few GRBs per year, hundreds or more high-energy photons per burst may be attainable once they are detected. We also address various issues related to following up alerts from satellites and other facilities with CTA, as well as follow-up observations at other wavelengths. The possibility of discovering and observing GRBs from their onset including short GRBs during a wide-field survey mode is also briefly discussed.

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“…This injection can take on all sorts of forms, including long-term source luminosity, 189,190 conversion of Poynting flux from the ejecta [165][166][167] or late time shells catching up. 201,[221][222][223] Alternative explanations not including jet dynamics are changing microphysics of the emission 219,224,225 or viewing angle effects. 226 An attractive candidate to provide long-term injection of energy is a magnetar, which would add energy into the system when shedding its rotational energy following its formation in the event that triggers the GRB.…”

Section: Persistent Injection Of Energymentioning

confidence: 99%

Gamma-ray burst afterglow blast waves

Eerten

2018

Int. J. Mod. Phys. D

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The various stages of baryonic gamma-ray burst afterglow blast waves are reviewed. These are responsible for the afterglow emission from which much of our understanding of gamma-ray bursts derives. Initially, the blast waves are confined to the dense medium surrounding the burster (stellar envelope or dense wind), giving rise to a jet-cocoon structure. A massive ejecta is released and potentially fed by ongoing energy release from the burster and a forward-reverse shock system is set up between ejecta and ambient density. Ultimately the blast wave spreads sideways and slows down, and the dominant afterglow emission shifts from X-rays down to radio. Over the past years significant progress has been made both observationally and theoretically/numerically in our understanding of these blast waves, unique in the universe due to their often incredibly high initial Lorentz factors of 100-1000. The recent discovery of a short gamma-ray burst counterpart to a gravitational wave detection (GW 170817) brings the promise of a completely new avenue to explore and constrain the dynamics of gamma-ray burst blast waves. January 8, 2018 1:34 WSPC/INSTRUCTION FILE vanEerten˙IJMPD˙review-arXiv 2 Hendrik van EertenWhat ultimately tipped the scales firmly in favor of extra-galactic models involving cataclysmic events produced by individual or merging stars, were the 1997 discoveries of afterglows and the redshift distance determinations that these made possible. 4, 5 GRB afterglows had been predicted by a class of models (most explicitly, the fireball model 6, 7 ) positing a sudden deposition of a huge amount of energy at the site of a neutron star merger or massive star collapse. This was argued to trigger an expanding relativistic blast wave, which would ultimately decelerate and produce counterpart emission at a range of frequencies (i.e. X-rays and optical, 8 radio 9 ), as the energies of shock-accelerated particles in the blast wave shifted to lower peak values. The far smaller directional error circles from afterglow X-ray and optical measurements relative to gamma rays made the first host galaxy association 10, 11 possible (GRB 970228), at which point the verdict was unambiguously in.The first detected afterglow was connected to a long GRB. It had already become clear that there existed a bimodality in the distribution of GRB durations, with separate long and short duration populations on either side of a divide at roughly 2 seconds. 12 The aforementioned host galaxy association of GRB 970228 and in particular the measurement of a supernova (SN) counterpart to nearby (uniquely so, at z = 0.0085) GRB 980425, 13 firmly established a massive star origin for the long GRBs. The predominant model for short GRBs is that these are launched during the merger of two neutron stars. 14,15 Until very recently, the peer-reviewed evidence for the short GRB scenario remained indirect, and was based on e.g. time-scale arguments, host galaxy types and measured offsets relative to host galaxies (for a recent review, see e.g. 16 ). However, shor...

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Effects of a low electron distribution cutoff on multiwavelength spectra and light curves of GRB afterglows

Cited by 14 publications

References 46 publications

Simulations of gamma-ray burst afterglows with a relativistic kinetic code

Simulations of gamma-ray burst afterglows with a relativistic kinetic code

Gamma-ray burst science in the era of the Cherenkov Telescope Array

Gamma-ray burst afterglow blast waves

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