Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992cait.reptq....p&link_type=abstract
Final Report, 15 Jun. 1989 - 30 Nov. 1991 California Inst. of Tech., Pasadena. Lab. of Physics.
Astronomy and Astrophysics
Astrophysics
A Stars, Astrophysics, Carbon Stars, Infrared Astronomy Satellite, Interplanetary Dust, Planetary Nebulae, Radiative Transfer, Red Giant Stars, Stellar Envelopes, Computer Programs, Distance, Distortion, Millimeter Waves, Stellar Mass Ejection, Submillimeter Waves, Surveys
Scientific paper
The research supported by the NASA ADP contract NAG5-1153 has been completed. The attached paper, which will be submitted for publication in the Astrophysical Journal in January 1992, presents the results of this work. Here is a summary of the project and its results. A set of computer programs was developed to process the raw 60 micron and 100 micron IRAS survey data. The programs were designed to detect faint extended emission surrounding a bright unresolved source. Candidate objects were chosen from a list of red giant stars and young planetary nebulae which have been detected in millimeter/submillimeter lines of CO. Of the 279 stars examined, 55 were resolved at 60 microns. The principle results of the study are given. The average age for the shells surrounding the 9 Mira-type stars which are extended is 6 x 104 yr. This suggests that the period during which these stars lose mass lasts for approx 105 yr. The oldest shell found surrounds U Ori, and the youngest surrounds Mira itself. Some shells appear to be detached from the central star. This phenomenon is more common among older stars, suggesting that the mass loss becomes more episodic as the star sheds its envelope. Although all 8 stars less distant than 200 pc are resolved in the IRAS 60 micron data, 29 stars within 500 pc were not. These stars probably have younger circumstellar shells than those which were resolved. Almost all the carbon stars with distances of 500 pc or less have resolved shells, while only 1/2 of the oxygen-rich stars do. The resolved carbon star shells also are older on average than the oxygen-rich ones. These facts imply that carbon stars have been losing mass for a longer period, on average, than oxygen-rich red giants.
Knapp Gillan R.
Phillips Thomas G.
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