Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997a%26a...317..203r&link_type=abstract
Astronomy and Astrophysics, v.317, p.203-211
Astronomy and Astrophysics
Astrophysics
11
Ism: Supernova Remnants, Ism: Individual: Cas A, Stars: Mass Loss
Scientific paper
Very Large Array (VLA) observations of the λ21 cm H I line towards Cassiopeia A (Cas A) have been performed. The velocity interval observed was from -38 to -362(LSR)km/s, with a resolution of 2.6km/s and a beam size of 14.2"x11.4". Opacity images show the presence of a number of small absorption H I features in the velocity interval -62 to -69km/s (LSR) which, on the basis of several arguments, are postulated to be physically associated with Cas A. These cold H I knots have sizes of <0.1pc and show spatial substructure. Their velocities lie well outside the range of the intervening H I in the Perseus spiral arm, i.e. 0 to -55km/s. We demonstrate that the H I knots cannot be described as shocked interstellar cloudlets engulfed by the blast wave of the supernova remnant (SNR). Instead, we propose that these low velocity H I features are recombined wind driven clumps moving ahead of the supernova (SN) shock front. This hypothesis is supported by the ages derived for the knots, varying from 8x10^3^ to 5x10^4^years, which implies that these features were originally accelerated during the Wolf-Rayet (WR) phase of the precursor star.
Dubner Gloria M.
Goss William Miller
Reynoso Estela M.
Schwarz Ulrich J.
Winkler Frank P.
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