The Changing Morphology and Increasing Deceleration of Supernova 1993J in M81
N. Bartel,
1*
M. F. Bietenholz,
1
M. P. Rupen,
2
A. J. Beasley,
2
D. A. Graham,
3
V. I. Altunin,
4
T. Venturi,
5
G. Umana,
6
W. H. Cannon,
17
J. E. Conway
8
Twenty consecutive Very Long Baseline Interferometry images of
supernova 1993J 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 that the supernova expands isotropically from its explosion center. Systematic changes in the
images may reflect a pattern of anisotropies and inhomogeneities in the
material left over from the progenitor star. As the shock front sweeps
up the material in the surrounding medium, it is increasingly
decelerated and influenced by the material. After 5 years, the
supernova has slowed to half of its original expansion velocity and may
have entered the early stages of the adiabatic phase common in much
older supernova remnants in the Milky Way Galaxy.
1 Department of Physics and Astronomy, York University,
Toronto M3J 1P3, Ontario, Canada.
2 National Radio Astronomy
Observatory, Socorro, NM 87801, USA.
3 Max-Planck-Institut
für Radioastronomie, D-53121 Bonn, Germany.
4 Jet
Propulsion Laboratory, California Institute of Technology, Pasadena, CA
91109, USA.
5 Instituto di Radioastronomia, CNR, 40129 Bologna, Italy.
6 Instituto di Radioastronomia, CNR, 96017 Noto, Italy.
7 Space Geodynamics Laboratory/CRESTech,
Toronto M3J 3K1, Ontario, Canada.
8 Onsala Space
Observatory, Chalmers University of Technology, S-43992 Onsala, Sweden.
*
To whom correspondence should be addressed. E-mail:
bartel{at}york.u.ca
