Lecture 5: Gamma-Ray Bursts Light extinction:

GRBs are brief flashes of soft -ray radiation ( 100 keV), discovered in the 1970s, the origin of which was not known until 1997 CGRO-BATSE

CGRO spectrum of a GRB

Light curves of GRBs Fluence ~ if cosmological relativistic conditions are implied: Lorentz factor CGRO-BATSE (Fishman & Meegan 1995)

The GRB distribution is isotropic

Bimodal distribution of GRB durations short long Different progenitors: SNe vs binary NS mergers Kulkarni 2000 Duration (s)

Precisione di BATSE 1 grado

: The BeppoSAX revolution Wide Field Cameras

Precisione di BATSE 1 grado Precisione delle WFC di BSAX

8 hours3 days GRB970228: first detection of X-ray and optical afterglow 6 months later Costa et al Van Paradijs et al. 1997

Firecone model: relativistic shocks in a jet ~ 100 ~ 10

Early Multiwavelength Counterparts (z = 0.937) Bloom et al (z = 6.29) (z = 1.6)

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

GRB Supernova 1998bw (Type Ic) z =

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