High-efficiency Photospheric Emission of Long-duration Gamma-ray Burst Jets: The Effect of the Viewing Angle

Type Journal Article
Names Davide Lazzati, Brian J. Morsony, Mitchell C. Begelman
Publication The Astrophysical Journal
Volume 732
Issue 1
Pages 34
Date May 1, 2011
Short Title High-efficiency Photospheric Emission of Long-duration Gamma-ray Burst Jets
URL http://adsabs.harvard.edu/abs/2011ApJ...732...34L
Library Catalog NASA ADS
Abstract We present the results of a numerical investigation of the spectra and light curves of the emission from the photospheres of long-duration gamma-ray burst jets. We confirm that the photospheric emission has high efficiency and show that the efficiency increases slightly with the off-axis angle. We show that the peak frequency of the observed spectrum is proportional to the square root of the photosphere's luminosity, in agreement with the Amati relation. However, a quantitative comparison reveals that the thermal peak frequency is too small for the corresponding total luminosity. As a consequence, the radiation must be out of thermal equilibrium with the baryons in order to reproduce the observations. Finally, we show that the spectrum integrated over the emitting surface is virtually indistinguishable from a Planck law, and therefore an additional mechanism has to be identified to explain the non-thermal behavior of the observed spectra at both high and low frequencies.
Tags Methods: Numerical, RADIATION MECHANISMS: THERMAL, gamma-ray burst: general, relativistic processes
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