Distance Determination of Mass-Losing Stars

Abstract

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 the radial velocity and Oort's galactic rotation model for a zero-point calibration in the distance modulus. Also, based on the requirement of higher accuracy of the distance determination, the mass-losing red giant stars were divided into two groups by means of the first-principal component representing an intrinsic photometric property of the expanding shell; then, the distances were estimated to be logd(kpc) = 0.458 p<i + 0.09 ± 0.13 for group 1 and logd(kpc) = 0.325 P2 + 0.45 ± 0.15 for group 2, where p<i is the principal component corresponding to the distance, as obtained from the IRAS flux, which was assumed to be inversely proportional to the square of the distance. Thus,these two groups differ from each other not only by their photometric properties, but also by their average distances, by a factor of about 2. Systematic differences exist between the two groups in their population characteristics and in their evolutionary stages.