2003/01/14 by E. Berger, S. R. Kulkarni, D. A. Frail · 1 citation
Physics and Astronomy · #Astro and Planetary Science #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/374892
published as Astrophys.J. 590 (2003) 379-385 · Submitted to ApJL; 17 pages; 2 tables; 2 figures
arxiv created 2003/01/14 · openalex publication_date 2003/06/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
We present a comprehensive sample of X-ray observations of 41 γ-ray burst (GRB) afterglows, as well as jet opening angles, θ j , for a subset with measured jet breaks. We show that there is a significant dispersion in the X-ray fluxes, and hence isotropic X-ray luminosities ( L X,iso ), normalized to t = 10 hr. However, there is a strong correlation between L X,iso and the beaming fractions, f b ≡ [1 - cos(θ j )]. As a result, the true X-ray luminosity of GRB afterglows, L X = f b L X,iso , is approximately constant, with a dispersion of only a factor of 2. Since e E b ∝ L X , the strong clustering of L X directly implies that the adiabatic blast wave kinetic energy in the afterglow phase, E b , is tightly clustered. The narrow distribution of L X also suggests that p ≈ 2, that inverse Compton emission does not in general dominate the observed X-ray luminosity, and that radiative losses at t < 10 hr are relatively small. Thus, despite the large diversity in the observed properties of GRBs and their afterglows, the energy imparted by the GRB central engine to the relativistic ejecta is approximately constant.