2001/02/28 by F. Frontera, L. Amati, M. Vietri +12 · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #Gamma-ray bursts and supernovae #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1086/319480
published as The Astrophysical Journal, Vol. 550, L47-L51, 2001 March 20 · 18 pages, 4 figures, published in The Astrophysical Journal Letters, relevant changes in the Discussion (section 4) with respect to previous version
arxiv created 2001/03/19 · openalex publication_date 2001/03/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We report on the prompt X- and γ-ray observations of GRB 990712 with the BeppoSAX Gamma-Ray Burst Monitor and Wide Field Camera 2. As a result of Sun constraints, we could not perform a follow-up observation with the BeppoSAX narrow-field instruments. The light curve of the prompt emission shows two pulses and a total duration of about 40 s in X-rays. In γ-rays, the event is even shorter. The 2-700 keV spectral emission with time shows a discontinuity in the peak energy E p of the EF ( E ) spectrum: E p is above our energy passband during the first pulse and goes down to ~10 keV during the second pulse. Another peculiarity is noted in this event for the first time: the evidence of a 2 s duration emission feature during the tail of the first pulse. The feature is consistent with either a Gaussian profile with centroid energy of 4.5 keV or a blackbody spectrum with kT bb ~ 1.3 keV. We discuss the possible origin of the feature. The most attractive possibility is that we are observing the thermal emission of a baryon-loaded expanding fireball when it becomes optically thin.