1998/04/30 by C. D. Dermer, J. Chiang, M. Boettcher · 2 citations
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1086/306871
26 pages, including 4 figures, uses epsf.sty, rotate.sty; submitted to ApJ; revised version with extended introduction, redrawn figures, and corrections
arxiv created 1998/09/01 · arxiv updated 2009/12/01
A simple function for the spectral power P(ε,t) ≡ νL(ν) is proposed to model, with 9 parameters, the spectral and temporal evolution of the observed nonthermal synchrotron power flux from GRBs in the blast wave model. Here ε= hν/mec2 is the observed dimensionless photon energy and t is the observing time. Assumptions and an issue of lack of self-consistency are spelled out. The spectra are found to be most sensitive to the baryon loading, expressed in terms of the initial bulk Lorentz factor Γ0, and an equipartition term q which is assumed to be constant in time and independent of Γ0. Expressions are given for the peak spectral power Pp(t) = P(εp,t) at the photon energy ε= εp(t) of the spectral power peak. A general rule is that the total fireball particle kinetic energy E0 ∼ Π0 td, where td ∝ Γ0-8/3 is the deceleration time scale and Π0 ≡ P(εp,td) ∝ Γ08/3 is the maximum measured bolometric power output in radiation, during which it is carried primarily by photons with energy \cal E0 = εp(td) ∝ qΓ04.