Carbon stars in the IRTS survey

We have identified 139 cool carbon stars in the near-infrared spectro-photometric survey of the InfraRed Telescope in Space (IRTS) from the conspicuous presence of molecular absorption bands at 1.8, 3.1 and 3.8 microns. Among them 14 are new, bright (K ~ 4.0-7.0), carbon stars. We find a trend relating the 3.1 microns band strength to the K-L' color index, which is known to correlate with mass-loss rate. This could be an effect of a relation between the depth of the 3.1 microns feature and the degree of development of the extended stellar atmosphere where dust starts to form.