Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-01-14
Astronomy and Astrophysics
Astrophysics
To appear in Astronomy & Astrophysics. 6 pages, 3 figures, uses aa.cls style file
Scientific paper
10.1051/0004-6361:20011794
We observed SN1979C in M100 on 4 June 1999, about twenty years after explosion, with a very sensitive four-antenna VLBI array at the wavelength of 18cm. The distance to M100 and the expansion velocities are such that the supernova cannot be fully resolved by our Earth-wide array. Model-dependent sizes for the source have been determined and compared with previous results. We conclude that the supernova shock was initially in free expansion for 6 +/- 2 yrs and then experienced a very strong deceleration. The onset of deceleration took place a few years before the abrupt trend change in the integrated radio flux density curves. We estimate the shocked swept-up mass to be about 1.6 solar masses, assuming a standard density profile for the CSM. Such a swept-up mass for SN1979C suggests a mass of the hydrogen-rich envelope ejected at explosion no larger than $M_{\rm env} \sim$ 0.9 solar masses. If SN1979C originated in a binary star the low value of M_env suggests that the companion of the progenitor star stripped off most of the hydrogen-rich envelope mass of the presupernova star prior to the explosion.
Alberdi Antonio
Diamond Phil J.
Guirado Jose C.
Lara Liana
Marcaide Juan Maria
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