LUMINOSITY AND VELOCITY DISTRIBUTION OF HIGH-LUMINOSITY RED STARS,NEAR THE SUN. I. THE VERY YOUNG DISK POPULATION.

Abstract

ABSTRACT The luminosities and space motions of the very young disk-population red stars near the sun are discussed on the basis of UBVRI photometry and accurate apparent motions. The sample includes all stars brighter than VE = 5" O as well as some objects apparently fainter because of interstellar reddening. The FK 4 system of proper motions, with corrections to Newcombe's precessional constant, is found to be preferred to the N 30 system. Very young disk stars are defined by the velocity distribution of the early B-type stars and about one-third of the sample of luminous red stars in this population belong to the Pleiades group. Approximately half of the remaining stars in the sample are probably members of another group with V = -18 km sec-1. The Pleiades group also contains the clusters NGC 2287 and NCC 2516 in addition to the a Persei cluster while the group with V = - 18 km sec -1 contains the clusters Collinder 121 and IC 2391. The very young disk population in this sample appears to be divided between objects of 5 and 9 solar masses in the ratio 3/2 with a half dozen stars of higher mass. Key words: stellar population - space motions - photometry