Constraints on the properties of circumstellar shells from observations of thermal CO and SiO millimeter line emission

Abstract

view Abstract Citations (48) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Constraints on the properties of circumstellar shells from observations of thermal CO and SiO millimeter line emission. Lambert, D. L. ; Vanden Bout, P. A. Abstract An attempt to detect CO and SiO microwave emission from Betelgeuse and long-period variables (LPVs) is described. The absence of SiO 86 GHz emission from the Betelgeuse circumstellar shell is shown to require that either all Si is associated into silicate dust grains or SiO molecule formation is inhibited. The former explanation is consistent with published estimates of the column density of silicate grains. The latter explanation is supported by the absence of emission in the CO 115 GHz line. Circumstellar absorption lines are not present in the TiO y(0, 0) band near 7100 A. TiO, like SiO and CO, appears to be underabundant in the shell. The new detections of circumstellar microwave emission include an observation of the CO 115 GHz line from R Cas (the first LPV for which both SiO 86 GHz emission and CO 115 GHz emission are seen) and of the SiO 86 GHz line from the S star Cyg. The absence of the isotopic line 30SiO at 84 GHz shows that the shells around R Cas, R Leo, and Cyg have an optical depth in the 86 GHz line of r < 10. This suggests that the SiO molecules contain a minor fraction of the total Si and that a substantial fraction of the Si is in the silicate grains. The shell around R Leo has been detected through the K I fluorescent emission. This confirms that the shells are large. Subject headings: radio sources: lines - stars: abundances - stars: circumstellar shells - stars: long-period variables Publication: The Astrophysical Journal Pub Date: May 1978 DOI: 10.1086/156088 Bibcode: 1978ApJ...221..854L Keywords: Abundance; Millimeter Waves; Radio Sources (Astronomy); Stellar Envelopes; Thermal Emission; Variable Stars; Carbon Monoxide; Cosmic Dust; Granular Materials; Interstellar Matter; Silicon Oxides; Astrophysics; Carbon Monoxide:Circumstellar Shells; Circumstellar Shells:Long-Period Variables; Circumstellar Shells:M Supergiants; Circumstellar Shells:Sio; SiO: Circumstellar Shells full text sources ADS | data products SIMBAD (6)