Evolution of the Circumstellar Molecular Envelope. I. A BIMA CO Survey of Evolved Stars

Astronomy and Astrophysics – Astronomy

Scientific paper

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

31

Stars: Circumstellar Matter, Radio Lines: Stars, Stars: Agb And Post-Agb, Stars: Mass Loss

Scientific paper

This paper reports the results of a small imaging survey of eight evolved stars including two AGB stars (IRC +10216 and Mira), five proto-planetary nebula (PPN) candidates (AFGL 2688, IRAS 22272+5435, HD 161796, 89 Her, and HD 179821), and a planetary nebula (PN, NGC 7027). We present high-resolution 12CO J=1-->0 maps of their full molecular envelopes made by combining BIMA Millimeter Array and NRAO 12 m telescope observations. For the PPNe and PN, the neutral molecular envelopes are compared with images taken at optical, near-IR, and mid-IR wavelengths. Drawing from the literature, we augmented our BIMA survey sample to 38 well-studied sources with CO emission maps. We classified this sample of sources based on the kinematics and morphologies of the CO emission into three types: spherical/elliptical/shell sources, disk sources, and structured outflow sources. Confirming previous studies, we find strong evidence for the photodissociation of the molecular envelope as an object evolves from the AGB to PN stages. While the spherical AGB stars follow theoretical expectations for mass-loss rate versus envelope size, the post-AGB structured outflow sources have significantly higher mass-loss rates than expected probably because of their recent superwinds. We find evidence that the structured outflows are clearly younger than the AGB wind. The disk sources have little correlation between mass-loss rate and envelope size because their properties are determined more by the properties of the central stars and disk evolution than by the mass-loss rate history that shapes the spherical and structured-outflow sources.

No associations

LandOfFree

Say what you really think

Search LandOfFree.com for scientists and scientific papers. Rate them and share your experience with other people.

Rating

Evolution of the Circumstellar Molecular Envelope. I. A BIMA CO Survey of Evolved Stars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Evolution of the Circumstellar Molecular Envelope. I. A BIMA CO Survey of Evolved Stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evolution of the Circumstellar Molecular Envelope. I. A BIMA CO Survey of Evolved Stars will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFWR-SCP-O-1239374

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.