Carbon Stars with Excess Emission at 60-MICRON Wavelength

Details Carbon Stars with Excess Emission at 60-MICRON Wavelength Carbon Stars with Excess Emission at 60-MICRON Wavelength

Sep 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...276..367z&link_type=abstract

Astronomy and Astrophysics, Vol.276, NO. 2/SEPII, P. 367, 1993

Astronomy and Astrophysics

Astrophysics

20

Stars: Carbon, Stars: Circumstellar Matter, Stars: Evolution Of, Stars: Mass Loss

Scientific paper

The Infrared Astronomical Satellite (IRAS) discovered that, in a 12-25-60 μm color-color diagram, many optically identified carbon stars emit excess flux at 60 m wavelength. It is generally agreed that the excess flux is emitted by a "detached" remnant dust shell ejected in a bygone episode of relatively rapid mass loss while the star was on the asymptotic giant branch. However, the chemical composition (C/O greater or less than unity?) and the structure (geometrically thick or thin?) of the shells, and their relevance to derivation of carbon star lifetimes are all controversial so that the place of these stars in the larger scheme of stellar evolution is unclear.
Model fits to stars with extended far infrared and CO emission indicate that the detached circumstellar shells are geometrically thin rather than thick. Geometrically thin shells imply dimensions sufficiently small that HCN emission can be excited in the vicinity of the region that emits the excess 60 μm flux and published HCN data indicate that most of the shells have C/O > 1. Then carbon star lifetimes can be reconciled with the 105 - 106 yr estimates based on statistical and theoretical considerations rather than the significantly shorter lifetimes derived by various researchers who assume that the detached envelopes are all oxygen-rich. The underlying cause of the variable mass loss rates remains unclear; repeated helium shell flashes seem to be the most plausible explanation.

Affiliated with

Also associated with

No associations

Rating

Carbon Stars with Excess Emission at 60-MICRON Wavelength 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 Carbon Stars with Excess Emission at 60-MICRON Wavelength, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Carbon Stars with Excess Emission at 60-MICRON Wavelength will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1558872