Larsson, J. 2011 GRB 061007的热谱成分

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这个暴用热谱拟合和用Band谱拟合一样好。

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Title:		Spectral components in the bright, long GRB 061007: properties of the photosphere and the nature of the outflow
Authors:		Larsson, J.; Ryde, F.; Lundman, C.; McGlynn, S.; Larsson, S.;
Affiliation:		AA(Department of Astronomy, Stockholm University,
Publication:		Monthly Notices of the Royal Astronomical Society, Volume 414, Issue 3, pp. 2642-2649. (MNRAS Homepage)
Publication Date:		07/2011
Origin:		WILEY
Astronomy Keywords:		radiation mechanisms: general, gamma-ray burst: individual: GRB 061007
Abstract Copyright:		© 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
DOI:		10.1111/j.1365-2966.2011.18582.x
Bibliographic Code:		2011MNRAS.414.2642L

Abstract

We present a time-resolved spectral analysis of the bright, long GRB 061007 (z= 1.261) using Swift and Suzaku data. We find that the prompt emission of the burst can be equally well explained by a photospheric component together with a power law as by a Band function, and we explore the implications of the former model. The photospheric component, which we model with a multicolour blackbody, dominates the spectra and has a very stable shape throughout the burst. This component provides a natural explanation for the hardness-intensity correlation seen within the burst and also allows us to estimate the bulk Lorentz factor and the radius of the photosphere. The power-law component dominates the fit at high energies and has a nearly constant slope of -1.5. We discuss the possibility that this component is of the same origin as the high-energy power laws recently observed in some Fermi bursts.

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Ryde, Felix 2011 伽马暴光球层的辐射的贡献

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认为光球辐射对非热成分的贡献也很大。

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Title:		Observational evidence of dissipative photospheres in gamma-ray bursts
Authors:		Ryde, Felix; Pe'Er, Asaf; Nymark, Tanja; Axelsson, Magnus; ...
Affiliation:		AA(Department of Physics, Royal Institute of Technology
Publication:		Monthly Notices of the Royal Astronomical Society, Volume 415, Issue 4, pp. 3693-3705. (MNRAS Homepage)
Publication Date:		08/2011
Origin:		WILEY
Astronomy Keywords:		radiation mechanisms: thermal, gamma-ray burst: general
Abstract Copyright:		© 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS
DOI:		10.1111/j.1365-2966.2011.18985.x
Bibliographic Code:		2011MNRAS.415.3693R

Abstract

The emission from a gamma-ray burst (GRB) photosphere can give rise to a variety of spectral shapes. The spectrum can retain the shape of a Planck function or it can be broadened and have the shape of a Band function. This fact is best illustrated by studying GRB090902B. The main gamma-ray spectral component is initially close to a Planck function, which can only be explained by emission from the jet photosphere. Later, the same component evolves into a broader Band function. This burst thus provides observational evidence that the photosphere can give rise to a non-thermal spectrum. We show that such a broadening is most naturally explained by subphotospheric dissipation in the jet. The broadening mainly depends on the strength and location of the dissipation, the magnetic field strength and the relation between the energy densities of thermal photons and electrons. We suggest that the evolution in spectral shape observed in GRB090902B is due to a decrease in the bulk Lorentz factor of the flow, leading to the main dissipation becoming subphotospheric. Such a change in the flow parameters can also explain the correlation observed between the peak energy of the spectrum and low-energy power-law slope, α, a correlation commonly observed in GRBs. We conclude that photospheric emission could indeed be a ubiquitous feature during the prompt phase in GRBs and play a decisive role in creating the diverse spectral shapes and spectral evolutions that are observed.

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