Supernova 1993J in M81
Abstract
Twenty-two consecutive VLBI images of supernova 1993J in the galaxy M81 spanning a period of 7 years show, in unprecedented detail, the dynamic evolution of the expanding radio shell of an exploded star. High precision astrometry using the phase-referenced data shows that the supernova expands isotropically, and that the geometric center of SN1993J has a formal proper motion of <700 km/s w.r.t. the core of the galaxy. Systematic changes in the images most likely reflect a pattern of inhomogeneities in the medium left over from the progenitor star, or possibly instabilities in the expanding shell. As the shockfront sweeps up the medium, it is progressively decelerated. After seven years the supernova had slowed down to less than half its original expansion velocity, and is likely now entering the early stages of the adiabatic phase common in much older supernova remnants in our own galaxy. We report on our latest results and discuss their physical implications.
- Publication:
-
Galaxies and their Constituents at the Highest Angular Resolutions
- Pub Date:
- January 2001
- Bibcode:
- 2001IAUS..205..380B