Study of Circumstellar Envelopes Around Bright Carbon Stars. 1. Structure, Kinematics, and Mass Loss Rate.

摘要

We have performed a survey of circumstellar CO emission on a sample of bright carbon stars, which is relatively complete out to about 900 pc from the sun. In total, 68 detections were made. All objects within 600 pc of the sun were detected. The result suggests that the large majority of all carbon stars have circumstellar envelopes. The CO emitting parts of these envelopes appear to have angular sizes less than about 15 sec. The median gas expansion velocity is 12.5 km/s and the expansion velocity for the majority of the objects fall in the range 9 to 15 km/s. We find no significant differences between the expansion velocities estimated from the CO(1-0) and CO(2-1) lines. Relatively accurate stellar radial velocities have also been obtained. The mass loss rate estimated from the CO data correlates well with an infrared excess estimate. This has been used to obtain mass loss rates for the entire sample.