THE ASTRONOMICAL JOURNAL    VOLUME 107, NUMBER 5, PAGE 1745            MAY 1994

 GLOBULAR CLUSTER PHOTOMETRY WITH THE HUBBLE SPACE TELESCOPE. II. U, V, AND I
                              MEASUREMENTS OF M15

                                  BRIAN YANNY

           Institute for Advanced Study, Princeton, New Jersey 08540
                    Electronic mail: yanny@guinness.ias.edu

                             PURAGRA GUHATHAKURTA

Princeton University Observatory, Peyton Hall, Princeton, New Jersey 08544-1001
                   Electronic Mail: raja@astro.princeton.edu

                    JOHN N. BAHCALL AND DONALD P. SCHNEIDER

           Institute for Advanced Study, Princeton, New Jersey 08540
               Electronic mail: jnb@sns.ias.edu, dps@sns.ias.edu

                                   ABSTRACT
    
    The projected density distribution of resolved stars near the center of
    M15 is shown to be consistent with either a power-law cusp N(r) ~
    r^alpha, with alpha ~ -0.85 +/- 0.2, or with a King model with a core
    of radius <~ 2" (best fit r(core) = 1.3").  The inferred slope is in
    agreement with the theoretical value, alpha = -0.75, calculated by
    Bahcall and Wolf for the distribution of equal-mass stars surrounding a
    massive black hole and is also consistent with the radial profile
    expected from core collapse without a central black hole.  The object
    AC 214 is a candidate for the central density cusp.  Analysis of Monte
    Carlo simulations of the diffuse light indicates that, using current
    analysis techniques and available data, the residual light is not a
    reliable indicator of the true density distribution.  This is contrary
    to earlier work.  Photometric measurements in V and I of more than
    5x10^3 stars (and in U, V, and I of >~ 1500 stars) are used to
    construct color-magnitude diagrams in the central 1' of M15.  Fourteen
    blue straggler candidates are identified in the inner 20".  The central
    color gradient noticed by previous researchers is caused by a central
    depletion of bright red giant stars rather than an excess of blue
    stragglers or blue horizontal branch stars.