Long‐Lag, Wide‐Pulse Gamma‐Ray Bursts

Norris, J. P.; Bonnell, J. T.; Kazanas, Demosthenes; Scargle, Jeffrey D.; Hakkila, Jon; Giblin, Timothy W.

doi:10.1086/430294

Cited by 252 publications

(435 citation statements)

References 42 publications

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“…The first two energy ranges were chosen as in Ackermann et al (2011). Following Norris et al (2005), we then fitted each light curve with a temporal profile that is defined as the product of two exponentials, i.e.,…”

Section: Estimation Of the Variability Timescalementioning

confidence: 99%

Time evolution of the spectral break in the high-energy extra component of GRB 090926A

Yassine

Piron

Mochkovitch

et al. 2017

A&A

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Aims. The prompt light curve of the long GRB 090926A reveals a short pulse ∼10 s after the beginning of the burst emission, which has been observed by the Fermi observatory from the keV to the GeV energy domain. During this bright spike, the high-energy emission from GRB 090926A underwent a sudden hardening above 10 MeV in the form of an additional power-law component exhibiting a spectral attenuation at a few hundreds of MeV. This high-energy break has been previously interpreted in terms of gamma-ray opacity to pair creation and has been used to estimate the bulk Lorentz factor of the outflow. In this article, we report on a new time-resolved analysis of the GRB 090926A broadband spectrum during its prompt phase and on its interpretation in the framework of prompt emission models. Methods. We characterized the emission from GRB 090926A at the highest energies with Pass 8 data from the Fermi Large Area Telescope (LAT), which offer a greater sensitivity than any data set used in previous studies of this burst, particularly in the 30−100 MeV energy band. Then, we combined the LAT data with the Fermi Gamma-ray Burst Monitor (GBM) in joint spectral fits to characterize the time evolution of the broadband spectrum from keV to GeV energies. We paid careful attention to the systematic effects that arise from the uncertainties on the LAT response. Finally, we performed a temporal analysis of the light curves and we computed the variability timescales from keV to GeV energies during and after the bright spike. Results. Our analysis confirms and better constrains the spectral break, which has been previously reported during the bright spike. Furthermore, it reveals that the spectral attenuation persists at later times with an increase of the break characteristic energy up to the GeV domain until the end of the prompt phase. We discuss these results in terms of keV−MeV synchroton radiation of electrons accelerated during the dissipation of the jet energy and inverse Compton emission at higher energies. We interpret the high-energy spectral break as caused by photon opacity to pair creation. Requiring that all emissions are produced above the photosphere of GRB 090926A, we compute the bulk Lorentz factor of the outflow, Γ. The latter decreases from 230 during the spike to 100 at the end of the prompt emission. Assuming, instead, that the spectral break reflects the natural curvature of the inverse Compton spectrum, lower limits corresponding to larger values of Γ are also derived. Combined with the extreme temporal variability of GRB 090926A, these Lorentz factors lead to emission radii R ∼ 10 14 cm, which are consistent with an internal origin of both the keV−MeV and GeV prompt emissions.

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Section: Estimation Of the Variability Timescalementioning

confidence: 99%

Time evolution of the spectral break in the high-energy extra component of GRB 090926A

Yassine

Piron

Mochkovitch

et al. 2017

A&A

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“…We expect that those fast-variability pulses shown in the GRB prompt emission/X-ray flare are produced by the extremely short-time activities of the microemitters. The gross profile (Norris et al 2005) with a long-time duration of prompt emission/X-ray flare is the superimposing factor of those fast-variability pulses. We can further quantify the parameters mentioned in Section 2.2.…”

Section: High-energy Emission Of Grb 100728amentioning

confidence: 99%

JITTER SELF-COMPTON PROCESS: GeV EMISSION OF GRB 100728A

Mao

Wang

2012

ApJ

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Jitter radiation, the emission of relativistic electrons in a random and small-scale magnetic field, has been applied to explain the gamma-ray burst (GRB) prompt emission. The seed photons produced from jitter radiation can be scattered by thermal/nonthermal electrons to the high-energy bands. This mechanism is called jitter self-Compton (JSC) radiation. GRB 100728A, which was simultaneously observed by Swift and Fermi, is a great example to constrain the physical processes of jitter and JSC. In our work, we utilize jitter/JSC radiation to reproduce the multiwavelength spectrum of GRB 100728A. In particular, due to JSC radiation, the powerful emission above the GeV band is the result of those jitter photons in the X-ray band scattered by the relativistic electrons with a mixed thermal-nonthermal energy distribution. We also combine the geometric effect of microemitters to the radiation mechanism, such that the "jet-in-jet" scenario is considered. The observed GRB duration is the result of summing up all of the contributions from those microemitters in the bulk jet.

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“…The continuous heating of seed thermal photons by a secondorder Compton process has also been considered (Thompson 1994;Giannios 2006), but this mechanism does not provide an obvious explanation for the correlation (eq. [51]) between pulse width and photon frequency, or for the lags of soft photons with respect to hard photons that are observed in some GRBs (especially those with broad pulses, e.g., Norris et al 2005).…”

Section: Implications For the Mechanism Of Particle Heatingmentioning

confidence: 99%

Thermalization in Relativistic Outflows and the Correlation between Spectral Hardness and Apparent Luminosity in Gamma‐Ray Bursts

Thompson¹,

Mészáros²,

Rees³

2007

ApJ

161

182

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We present an interpretation of the phenomenological relations between the spectral peak, isotropic luminosity, and duration of long gamma-ray bursts that have been discovered by Amati and coworkers, Ghirlanda and coworkers, Firmani and coworkers, and Liang & Zhang. In our proposed model, a jet undergoes internal dissipation which prevents its bulk Lorentz factor from exceeding 1/ ( being the jet opening angle) until it escapes from the core of its progenitor star, at a radius of order 10 10 cm; dissipation may continue at larger radii. The dissipated radiation will be partially thermalized, and we identify its thermal peak ( Doppler boosted by the outflow) with E pk . The radiation comes, in effect, from within the jet photosphere. The nonthermal, high-energy part of the GRB emission arises from Comptonization of this radiation by relativistic electrons and positrons outside the effective photosphere. This model can account naturally not only for the surprisingly small scatter in the various claimed correlations, but also for the normalization, as well as the slopes. It then has further implications for the jet energy, the limiting jet Lorentz factor, and the relation of the energy, opening angle and burst duration to the mass and radius of the stellar stellar progenitor. The observed relation between pulse width and photon frequency can be reproduced by inverse Compton emission at $10 14 cm from the engine, but there are significant constraints on the energy distribution and isotropy of the radiating particles.

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Long‐Lag, Wide‐Pulse Gamma‐Ray Bursts

Cited by 252 publications

References 42 publications

Time evolution of the spectral break in the high-energy extra component of GRB 090926A

Time evolution of the spectral break in the high-energy extra component of GRB 090926A

JITTER SELF-COMPTON PROCESS: GeV EMISSION OF GRB 100728A

Thermalization in Relativistic Outflows and the Correlation between Spectral Hardness and Apparent Luminosity in Gamma‐Ray Bursts

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