1999/02/03 by Davide Lazzati, S. Campana, Sergio Campana +2 · 2 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.1999.02517.x
5 pages, 1 figure, MNRAS letters in press
arxiv created 1999/02/03 · openalex publication_date 1999/04/07 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
The discovery of a powerful and transient iron line feature in the X-ray afterglow spectra of gamma-ray bursts would be a major breakthrough for understanding the nature of their progenitors. Piro et al. and Yoshida et al. report such a detection in the afterglows of GRB 970508 and GRB 970828, respectively. We discuss how such a strong line could be produced in the various scenarios proposed for the event progenitor. We show that the observed line intensity requires a large iron mass, concentrated in the vicinity of the burst. The previous explosion of a supernova, predicted in the ‘supranova’ scenario, is the most straightforward way to account for such a large amount of matter. We discuss three different physical processes that could account for the line: recombination, reflection and thermal emission. Among these, reflection and thermal emission may explain the observed line features; reflection should be important if the remnant is optically thick, while thermal lines can be produced only in a thin plasma. The recombination process requires extremely high densities to reprocess the burst photons efficiently, but could work during the X-ray afterglow. Future key observations for discerning the actual radiating process are discussed.