2005/11/30 by V. D' Alessio, V. D'Alessio, L. Piro +2 · 39 citations
Chemistry · Physics and Astronomy · #Afterglow #Astronomy #Astrophysics #Chemistry #Flux (metallurgy) #Galaxy #Gamma-ray burst #Gamma-ray bursts and supernovae #Luminosity #Optics #Physics #Redshift #Spectral line #Viewing angle #X-ray #astro-ph
paper · pdf · doi:10.1051/0004-6361:20054501
published in Astronomy and Astrophysics 460(3), 653-664 (EDP Sciences) · 18 pages, 12 color figures, 1 b/w figures, accepted to Astronomy and Astrophysics
arxiv created 2006/08/08 · openalex publication_date 2006/08/25 · arxiv updated 2015/06/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study the spectrum of the prompt emission and the X-ray and optical afterglow fluxes of 54 X-Ray Rich Gamma Ray Burst (XRRs) and X-Ray Flashes (XRFs), observed by BeppoSAX and HETE-2. A comparison is then performed with classical Gamma Ray Bursts (GRBs). The goal of this paper is to investigate the nature of XRRs/XRFs, as high redshift GRBs or off-axis GRBs, analyzing both their prompt and afterglow properties. We find that the XRR/XRF spectral indexes of the Band function are similar to those of classical GRBs, whereas the peak energy is lower by a factor of 4. We study the optical and X-Ray afterglow properties of the XRRs/XRFs; in particular we analyze the XRR 011030 afterglow. We find that the X-ray and optical flux distributions and the lightcurves of the XRRs/XRFs sample are consistent with those of classical GRBs; in particular, they show evidence of a break and no rising temporal slope. We compare these results with the afterglow predictions of the high redshift scenario, where XRFs are GRBs at higher redshift and of the off-axis scenario, where the observed differences are due to viewing angle effects. In this last framework, we consider jets with a homogeneous, a -2 power-law shaped and a Gaussian luminosity angular distribution. We find that the high redshift scenario can explain some events but not the total sample of XRRs/XRFs. The off-axis model may be consistent with our findings when a homogeneous jet is considered. However, given the uncertainties on the selection effects in our sample, a Gaussian jet viewed at small angles from the Gaussian core and a power-law shaped cannot be ruled out.