A search for SiO, OH, CO and HCN radio emission from silicate-carbon stars.
Abstract
We report upper limits for radio emission of SiO at 86 and 43 GHz, of OH at 1612 and 1665/1667 MHz, of CO at 115 GHz and HCN at 88.6 GHz in the silicate-carbon stars. These upper limits of SiO imply that oxygen-rich material has not been detected within 2Rstar of a central star even though the detected emission from silicate dust grains, H2O and OH maser establishes the presence of oxygen-rich material from about tens to thousands of AU of a central star. The upper limit of the SiO abundance is consistent with that found in oxygen-rich envelopes. Upper limits of the mass loss rate (based on the CO data) are estimated to be between 10-6 to 10-7 solar mass/yr assuming a distance of 1.5 kpc for these stars. The absence of HCN microwave emission implies that no carbon-rich material can be detected at large distances (thousands of AU) from a central star. The lack of detections of SiO, CO, and HCN emission is most likely due to the large distances of these stars. A number of C stars were detected in CO and HCN, but only the M supergiant VX Sgr was detected in CO.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 1994
- Bibcode:
- 1994A&A...281..451L
- Keywords:
-
- Abundance;
- Asymptotic Giant Branch Stars;
- Carbon Stars;
- Radio Astronomy;
- Radio Emission;
- Radio Spectra;
- Stellar Envelopes;
- Stellar Spectra;
- Astronomical Spectroscopy;
- Carbon Monoxide;
- Cosmic Dust;
- Hydrocyanic Acid;
- Hydroxyl Radicals;
- Line Spectra;
- Silicon Oxides;
- Stellar Composition;
- Astronomy