Gamma-Ray Bursts: Frontier astrophysics with the most extreme cosmic explosions

Abstract

This paper presents the main properties of Gamma-ray bursts (GRBs) and their connection with various topics of modern astrophysics. The future of the field is also addressed with a detailed presentation of the SVOM Sino-French mission and its scientific objectives. Keywords: Gamma-ray bursts, Cosmology, Gravity waves PoS(FRAPWS2014)026Gamma-Ray Bursts Jean-Luc Atteia Gamma-ray burstsGamma-ray bursts (GRBs) are powerful cosmic explosions produced at the end of the life of some massive stars, but also when two compact stars in a binary system merge after the dissipation of the angular momentum by gravitational waves. In both cases, the catastrophic event results in the birth of a fast rotating compact object (a black hole or a magnetar) which expels transient but very powerful relativistic jets in two opposite directions. If, by chance, one of these jets is directed towards the Earth, we observe a bright gamma-ray transient (the prompt GRB), which is followed by quickly fading afterglow emission at longer wavelengths (from X-rays to visible and radio). 1 While the brightness of GRBs allows their detection out to very large distances (up to redshift z = 8.3 for GRB 090423 [66,73]), we only detect the GRBs which emit a jet towards the Earth. Assuming an average opening angle of GRBs jets of a few degrees, the fraction of detectable GRBs amounts to 0.1 to 1%. This paper is divided into two parts. Section 1 provides a brief overview of the GRB phenomenon including some frontier topics that may interest the participants of this conference. Section 2 contains a brief description of the instruments and the scientific objectives of the future GRB mission SVOM, that will perpetuate GRB detection after Swift. The reader interested in getting a complete view of the field and its recent advances is invited to read the reviews listed in the bibliography [22,87,23,9,38,49]. The reader interested in an overview of the discoveries that have led to the solution of the so-called GRB mystery is invited to read the books of Vedrenne & Atteia [80] and of Kouveliotou, Wijers & Woosley [36]. Prompt emissionGRBs are transient events whose temporal evolution is divided into two steps: the prompt GRB and the afterglow. Figure 1 shows the main properties of the prompt GRB emission in hard X-rays: the light-curve of the bright nearby GRB 030329 at redshift z=0.17; the νFν spectrum of GRB 100724B peaking around E peak ∼ 500 keV; the isotropic distribution of GRBs on the sky [6], and the duration histogram which shows two peaks suggesting the existence of two classes, respectively called short and long GRBs. High-energy satellites play an essential role in the detection and classification of GRBs. The Large Area Detectors of BATSE, which have worked more than 9 years have shown that about 1000 GRBs cross the solar system each year (hereafter we call these bursts "classical GRBs", in contrast with X-Ray Flashes or low-luminosity GRBs described below). Since then, instruments like BeppoSAX WFC and HETE-2 WXM have extended GRB detection to soft ...