Ages and Structures of Stars in the H and χ Persei Association.

New spectral types determined from recent classification spectrograms for nine stars in the association surrounding h and x Persei are given, and the H-R diagram of the clusters and association is compared with evolutionary models of Iben and Stothers. Recent proper motion and radial velocity data are briefly drawn upon in a rediscussion of ages and structures of stars in the association. In the picture of the association which has resulted, x Persei is found to be 350 pc more distant than h Persei and five million years older. Distances found for and h Persei are, respectively, 2500 and 2150 pc, and ages determined are 11.5 and 6.4 million years. Surrounding x Persei appears to be an association of stars 65 pc in diameter (inner group) and of the age and distance of x Persei The M supergiants and extreme Be stars appear to be associated with the x Persei stellar population. Nuclear cluster h Persei appears to be associated with another, younger stellar population which extends over 200 pc and which is indicated to be at about the mean distance of the two clusters (outer group) Nine 0 stars are believed to define a third, very young stellar population which at least approximately shares the distance and extent of the outer group.