Lecture 5: Gamma-Ray Bursts Light extinction: GRBs are brief flashes of soft -ray radiation (100 keV), discovered in the 1970’s, the origin of which was not known until 1997 CGRO-BATSE CGRO spectrum of a GRB CGRO-BATSE (Fishman & Meegan 1995) Light curves of GRBs Fluence ~ 107 104 erg /cm 2 tvar 10ms 1, if cosmological relativistic conditions are implied: Lorentz factor The GRB distribution is isotropic long short Bimodal distribution of GRB durations Different progenitors: SNe vs binary NS mergers Duration (s) Kulkarni 2000 Precisione di BATSE 1 grado 1996-2002: The BeppoSAX revolution Wide Field Cameras Precisione delle WFC di BSAX Precisione di BATSE 1 grado GRB970228: first detection of X-ray and optical afterglow 8 hours 3 days Van Paradijs et al. 1997 t 1.3 Costa et al. 1997 6 months later “Firecone” model: relativistic shocks in a jet ~ 100 ~ 10 Early Multiwavelength Counterparts (z = 0.937) (z = 6.29) (z = 1.6) Bloom et al. 2008 Redshift Measurement Djorgovski et al. 1999 Bloom et al. 1998,1999 Host galaxies exhibit emission lines of star formation: [O II], [O III], Balmer and Paschen series Isotropic irradiated gamma–ray energy vs redshift Long GRB Short GRB GRB980425 Supernova 1998bw (Type Ic) z = 0.0085 Example of Supernova underlying GRB optical afterglow (z = 0.695) Galama et al. 1999 Light curves of Ic SNe: GRB-SNe, broad-lined SNe, normal SNe
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