Distance determination of mass-losing stars

Based on the Principal Component Analysis on IRAS colors and the radio data , the distances to 183 mass-losing red giant stars were determined using th e radial velocity and Oort's galactic rotation model for a zero-point calib ration in the distance modulus. Also, based on the requirement of higher ac curacy of the distance determination, the mass-losing red giant stars were divided into two groups by means of the first-principal component represent ing an intrinsic photometric property of the expanding shell; then, the dis tances were estimated to be log d(kpc) = 0.458 p(2) + 0.09 +/- 0.13 for gro up 1 and log d(kpc) = 0.325 p(2) + 0.45 +/- 0.15 for group 2, where p(2) is the principal component corresponding to the distance, as obtained from th e IRAS flux, which was assumed to be inversely proportional to the square o f the distance. Thus,these two groups differ from each other not only by th eir photometric properties, but also by their average distances, by a facto r of about 2. Systematic differences exist between the two groups in their population characteristics and in their evolutionary stages.