Circumstellar Interaction in Young Radio Supernovae

Abstract

We give an overview of circumstellar interaction in young radio supernovae, as seen through the eyes of Very-long-baseline interferometry (VLBI) observations. The resolution attained by such observations (≲ 1 mas) is a powerful tool to probe the interaction that takes place after a supernova goes off. The direct imaging of supernovae has permitted, among other things, to estimate the deceleration of their expansion, and to obtain information on the ejecta and circumstellar density profiles. Unfortunately, only a handful of radio supernovae are close and bright enough as to permit their study with VLBI. We present here results from our high-resolution observations of the nearby radio supernovae SN 1979C, SN 1986J, SN 1993J, and SN 2001gd.