9 июля 2001 |
- Norbert Bartel (York University)
VLBI of a Supernova
A set of 24 consecutive VLBI images of supernova 1993J in the nearby
galaxy M81 from the time of explosion to the present show the dynamic
evolution of the expanding radio shell of an exploded star. High
precision astrometry reveals the position of the explosion center with
an accuracy of 160 AU and shows that the supernova expands isotropically
from it within 5.5%. The images display the complex, non-selfsimilar,
behaviour of the shock front as it interacts with the circumstellar
medium left over from the progenitor star. As the shock front sweeps up
the medium it is increasingly decelerated. After only five years the
supernova has slowed down to half of its original expansion velocity, which
suggests that its evolution is now considerably influenced by the swept-up
material. The results are important for determining characteristics of the
progenitor, the profiles of the ejecta and the circumstellar medium, the
physics of the shock front region and the direct dynamical distance to the host
galaxy. My presentation includes the video ``Supernova: Death of a Star''
which contains the VLBI images along with an animated explanatory
introduction.
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