GRB 120422A/SN 2012bz: Bridging the Gap between Low- And High-Luminosity GRBs

Understand

At low redshift, a handful of gamma-ray bursts (GRBs) have been discovered with peak luminosities ($L_{\rm iso} < 10^{48.5}~\rm{erg\,s}^{-1}$) substantially lower than the average of the more distant ones ($L_{\rm iso} > 10^{49.5}~\rm{erg\,s}^{-1}$).

• The properties of several low-luminosity (low-$L$) GRBs indicate that they can be due to shock break-out, as opposed to the emission from ultrarelativistic jets.
• Owing to this, it is highly debated how both populations are connected, and whether there is a continuum between them.
• The burst at redshift $z=0.283$ from 2012 April 22 is one of the very few examples of intermediate-$L$ GRBs with a $\gamma$-ray luminosity of $L\sim10^{48.9}~\rm{erg\,s}^{-1}$ that have been detected up to now.