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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
Light curves of GRBs
Fluence ~
if cosmological
relativistic conditions are implied:Lorentz factor
CGRO-BATSE (Fishman & Meegan 1995)
€
10−7 ÷10−4 erg /cm2
€
tvar ≈10ms
€
τ >>1,
The GRB distribution is isotropic
Bimodal distribution of GRBdurations
short
long
Different progenitors: SNevs binary NS mergers
Kulkarni 2000Duration (s)
Precisionedi BATSE
1 grado
1996-2002:The BeppoSAXrevolution
Wide Field Cameras
Precisionedi BATSE
1 grado
Precisione delleWFC di BSAX
8 hours 3 daysGRB970228: first detection of X-ray and optical afterglow
6 monthslater
Costa et al. 1997
Van Paradijs et al. 1997
€
t−1.3
“Firecone” model: relativistic shocks in a jet
~ 100 ~ 10
Early Multiwavelength Counterparts
(z = 0.937)
Bloom et al. 2008
(z = 6.29)
(z = 1.6)
Redshift Measurement
Djorgovski et al. 1999
Bloom et al. 1998,1999
Host galaxies exhibit emission lines of starformation: [O II], [O III], Balmer and Paschen series
Isotropic irradiated gamma–ray energy vs redshift
Long GRB
Short GRB
GRB980425Supernova 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