Colloq Abstract - Bieteholz
Jan 26
11:00am Mountain
Michael Bietenholz (York U., HartRAO)
Resolving the Explosion of a Star: Recent Results in Supernova VLBI
Abstract
VLBI observations are the only way to spatially resolve young supernovae (SNe) farther than the Magellanic clouds. At present, we can resolve normal, non-relativistic SNe out to about the Virgo cluster and relativistic SNe about three times farther. The radio emission in SNe is produced as the expanding ejecta interact with the stellar wind of the progenitor. VLBI observations can therefore place important constraints on the nature of both the ejecta and the wind.
I will review recent results, in particular on SN 1986J, the only SN so far to show a central radio component in the VLBI images, which could be due to a newly-born pulsar or black hole, but could also be due to circumstellar interaction with a very anisotropic medium. VLBI observations can also be used to measure the speed of the expanding SN shock front, and thus determine whether the ejecta are relativistic or not. Relativistic ejecta are expected for long Gamma Ray Bursts (GRBs), which are associated with Type I b/c or stripped-envelope SNe, and VLBI observations can therefore help clarify the relationship between Type I b/c SNe and GRBs, as well as place limits on "orphan afterglows," or GRB events with jets directed far away from the line of sight. I will discuss recent radio observations of Type I b/c supernovae. So far, no direct confirmation of relativistic expansion has been found, but the prospect of imaging a relativistic supernova is an exciting new aspect of supernova research.
