The association of GRB 060218 with a supernova and the evolution of the shock wave

Although the link between long gamma-ray bursts (GRBs) and supernovae has been established, hitherto there have been no observations of the beginning of a supernova explosion and its intimate link to a GRB. In particular, we do not know how the jet that defines a gamma-ray burst emerges from the star's surface, nor how a GRB progenitor explodes. Here we report observations of the relatively nearby GRB 060218 (ref. 5) and its connection to supernova SN 2006aj (ref. 6). In addition to the classical non-thermal emission, GRB 060218 shows a thermal component in its X-ray spectrum, which cools and shifts into the optical/ultraviolet band as time passes. We interpret these features as arising from the break-out of a shock wave driven by a mildly relativistic shell into the dense wind surrounding the progenitor. We have caught a supernova in the act of exploding, directly observing the shock break-out, which indicates that the GRB progenitor was a Wolf-Rayet star.     

Gamma-ray bursts: huge explosion in the early Universe

Long gamma-ray bursts (GRBs) are bright flashes of high-energy photons that can last for tens of minutes; they are generally associated with galaxies that have a high rate of star formation and probably arise from the collapsing cores of massive stars, which produce highly relativistic jets (collapsar model). Here we describe gamma- and X-ray observations of the most distant GRB ever observed (GRB 050904): its redshift (z) of 6.29 means that this explosion happened 12.8 billion years ago, corresponding to a time when the Universe was just 890 million years old, close to the reionization era. This means that not only did stars form in this short period of time after the Big Bang, but also that enough time had elapsed for them to evolve and collapse into black holes.