New observations of cool carbon stars in the halo

Abstract

We report new results of our search for rare, cool carbon stars located at large distances from the galactic plane. Eighteen new C stars were discovered. Six are remarkable by showing the two peculiarities of a strong infrared excess at 12 microns and a large height above the Galactic plane, from 1.7 to 6 kpc. The number of C stars with these properties has been increased to 16. Mass-loss rates were tentatively estimated by assuming that all these 16 stars are Miras and by using the correlation between Mdot and the K-12 colour index. It is found that several stars have large mass loss, with median Mdot around 4E-06 solar mass per year. It would be desirable to detect their CO emission ... Eight stars might be at more than 30 kpc from the Sun, and two at the unprecedented distance of 150 kpc (this abstract has been abridged).Comment: 15 pages; accepted by Astronomy and Astrophysic