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)

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10−7 ÷10−4 erg /cm2

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tvar ≈10ms

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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

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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