Structure of circumstellar shell around the carbon star S Scuti

Details Structure of circumstellar shell around the carbon star S Scuti Structure of circumstellar shell around the carbon star S Scuti

Aug 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993pasj...45..573y&link_type=abstract

PASJ: Publications of the Astronomical Society of Japan (ISSN 0004-6264), vol. 45, no. 4, p. 573-585

Astronomy and Astrophysics

Astronomy

14

Carbon Stars, Emission Spectra, Radio Astronomy, Spectrum Analysis, Stellar Envelopes, Stellar Mass Ejection, Asymptotic Giant Branch Stars, Carbon Monoxide, Radio Telescopes, Stellar Evolution

Scientific paper

We have observed the carbon star S Sct in the CO J = 1-0 line with the 16 arcsecond beam of the 45-m radio telescope at Nobeyama Radio Observatory (NRO). The spectrum towards the star exhibits a sharp double spike, and the spectra at the offset positions (20, 40 and 60 arcseconds) show that the intensities and the velocity widths vary with the offset, indicating that the circumstellar envelope of S Sct is detached. Model calculations of the CO line intensities taking into account the non-LTE (Local Thermodynamical Equilibrium) effects lead us to conclude that the inner radius of the circumstellar shell of the star is 5.2 x 1017 cm, that the thickness of the circumstellar shell is less than or equal to 0.20 x 1017 cm (which is about a factor of 3 thinner than previous thought), and that the shell was formed by an extremely high-mass-loss event (a mass-loss rate of greater than or equal to 1.3 x 10-4 solar masses/yr) about 104 yr ago. The unusually high rate of mass loss could explain the fact that only three carbon stars with detached shells have ever been detected by CO observations. A new hypothesis concerning carbon star formation by Willems and de Jong (1988) suggests that optically bright carbon stars are objects in the intermediate phase between the termination of the oxygen-rich mass-loss phase and the beginning of the mass loss of the infrared carbon star phase. The derived time scale after the mass-loss termination of S Sct (104 yr) is similar to the estimated lifetime of optically bright carbon stars in their scenario.

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