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JAC Seminar 2003-02-28 Purton
Friday 28 February at 1:30pm
Chris Purton - Dominion Radio Astrophyisical Observatory
"Photodissociation and youth
- finding stars right at the birthline"
ABSTRACT: "Early-type B stars produce significant amounts of radiation capable
of dissociating molecular hydrogen, with very little attendant ionising radiation.
Newly-formed stars of this type are expected to interact with their parent
molecular cloud and thus appear embedded in a substantial HI region, with
perhaps a small HII region close to the star at its core. Such systems, characterised
by a large HI/HII ratio, have been termed "dissociating stars", and some
have been found, although far fewer than predicted which is a bit puzzling.
Another puzzling aspect is the very young ages, <~10^4 years, of all
that have been found, as determined by comparing observed systems with photodissociation
models. The dissociating star BD +65d 1638, in the reflection nebula NGC
7129, provides a particularly good example of these characteristics, and
will be described in some detail. The combination of scarcity and youth
suggests a short-lived phenomenon, in which case the dissociating stars
which are observed must be right at the birthline, and have the potential
for informing us of the detailed processes which occur as a star emerges
from its cocoon."
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