HIGH-EFFICIENCY PHOTOSPHERIC EMISSION OF LONG-DURATION GAMMA-RAY BURST JETS: THE EFFECT OF THE VIEWING ANGLE
- Department of Physics, NC State University, 2401 Stinson Drive, Raleigh, NC 27695-8202 (United States)
- Department of Astronomy, University of Wisconsin-Madison, 2535 Sterling Hall, 475 N. Charter Street, Madison, WI 53706-1582 (United States)
- JILA, University of Colorado, 440 UCB, Boulder, CO 80309-0440 (United States)
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.
- OSTI ID:
- 21574650
- Journal Information:
- Astrophysical Journal, Vol. 732, Issue 1; Other Information: DOI: 10.1088/0004-637X/732/1/34; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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