The theory of spectral evolution of the grb prompt emission
Oct, 20055 pages
Published in:
- Astrophys.J. 637 (2006) 869-872
e-Print:
- astro-ph/0510472 [astro-ph]
DOI:
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Abstract: (arXiv)
We develop the theory of jitter radiation from GRB shocks containing small-scale magnetic fields and propagating at an angle with respect to the line of sight. We demonstrate that the spectra vary considerably: the low-energy photon index, , ranges from 0 to -1 as the apparent viewing angle goes from 0 to . Thus, we interpret the hard-to-soft evolution and the correlation of with the photon flux observed in GRBs as a combined effect of temporal variation of the viewing angle and relativistic aberration of an individual thin, instantaneously illuminated shell. The model predicts that about a quarter of time-resolved spectra should have hard spectra, violating the synchrotron line of death. The model also naturally explains why the peak of the distribution of is at . The presence of a low-energy break in the jitter spectrum at oblique angles also explains the appearance of a soft X-ray component in some GRBs and a relatively small number of them. We emphasize that our theory is based solely on the first principles and contains no {\it ad hoc} (phenomenological) assumptions.- gamma rays: bursts
- magnetic fields
- radiation mechanisms: nonthermal
- shock waves
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