Short hard bursts
S. R. Kulkarni
References
• This is a tutorial • Primary reference: E. Berger (2013) Annual
Review• GW perspective: Kalsiwal & Nissanke (2013)
Properties
• Defined primary by duration (T<2 s) and further refined by hardness ratio
• In the BATSE sample the rate of short hard bursts (SHBs) is one quarter that of the total population (the remaining are Long Soft bursts).
• Less fluence relative to long duration GRBs
Host Galaxies
• Found in all types of environments– Clusters of galaxies – Elliptical galaxies– Field star forming galaxies
• Interesting Clue: Association with ULRGs– GRB 100206A (dusty ULIRG, z=0.407)– GRB 120804A (dusty ULIRG, z=1.3)– But only 1% of mass is in ULIRGs
Comparing to other samples
• Long duration GRBs are primarily found in low mass star-forming galaxies
• SHBs appear to trace the field population of star forming galaxies
• Just like SN of type Ia, SHBs arise infield galaxies of both old population and young star forming field galaxies– However the SN rate is higher in star-forming
galaxies