1999/07/27 by G. Ghisellini, Gabriele Ghisellini, Ghisellini, Gabriele
Engineering · Physics and Astronomy · #Advanced X-ray and CT Imaging #Astrophysics (astro-ph) #FOS: Physical sciences #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9907376
10 pages, 3 figures, invited paper at the XLIII meeting of the Italian Astronomical Society: "Revolutions in Astronomy" (May 1999)
arxiv created 1999/07/27 · openalex publication_date 1999/07/27 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Recent results of the hectic research activity about gamma-ray bursts will be reviewed, with emphasis about the emission processes at the origin of the observed gamma-rays. The conventional synchrotron shock scenario is found to have problems, due to the very short cooling times of the emitting electrons, which implies a predicted spectrum F(nu) proportional to nu^(-1/2), much steeper than what is observed. It is therefore compelling to look for alternative emission processes, such as quasi-thermal Comptonization, implying the presence of mildly or sub-relativistic electrons, producing, through multiple Compton scatterings, a spectrum proportional to nu0 ending with a Wien peak where photons and electron energies balance. The afterglow light, instead, can be indeed due to synchrotron radiation, and a confirmation of this is the recently detected optical linear polarization of the afterglow of GRB 990510. Some consequences of this discovery will be outlined. A quantum leap in our understanding of the physics of gamma-ray bursts is expected to come with SWIFT, a NASA-MIDEX dedicated satellite.