Dynamical models for M15 without a black hole

Abstract

The observed velocity dispersion and brightness profile of M15 were fitted with dynamical models that have no need for the central black hole suggested by Newell, Da Costa, and Norris (1976). The stellar mixture is the same as in other globular clusters, but M15 has a higher central concentration. In the present models the central brightness peak is caused by the gravitational effect of neutron stars; their number is in accord with a reasonable initial mass function and retention probability. Some modes of binary formation are discussed as a step toward possible explanation of the X-ray source in M15; but the results are inconclusive.