1999/04/30 by Renyue Cen
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Gamma-ray bursts and supernovae #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1086/312034
ApJ(Letters), published, 13 latex pages plus 2 figures
openalex publication_date 1999/06/01 · arxiv created 1999/08/22 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
It is shown here that the differential Doppler shift of different patches of the blast-wave front in the fireball model at varying angles to the line of sight could provide an intrinsic smoothing mechanism for the spectra of gamma-ray bursts (GRBs) and the associated afterglows at lower energy bands. For the model parameters of interest, a blast-wave comoving frame monochromatic spectrum at ν is smoothed to have a half-width at half-maximum of ~(0.6-2.0)ν. Some other implications of this smoothing process are discussed. In particular, if the circumburster medium is uniform and electron and magnetic energies are fixed fractions of the total postshock energy with time, the observed GRB or afterglow spectra cannot be steeper than ν α with α=0.75-1.25, regardless of the intrinsic spectra in the comoving shock frame; i.e., a very steep electron distribution function (with p >3) could produce an observed spectrum with α~1. In addition, a generic fast-rise-slow-decay type of GRB temporal profile is expected.