Globular Cluster Photometry with the Hubble Space Telescope. Vii. Color Gradients and Blue Stragglers in the Central Region of M30 (ngc 7099) from Wfpc2 Observations

We present F555W (V ), F439W (B), and F336W (U) photometry of 9507 stars in the central 2 of the dense, post core collapse cluster M30 (NGC 7099) derived from Hubble Space Telescope Wide Field/Planetary Camera 2 images. These data are used to study the mix of stellar populations in the central region of the cluster. Forty eight blue straggler stars are identified; they are found to be strongly concentrated towards the cluster center. The specific frequency of blue stragglers, FBSS ≡ N(BSS)/N(V < VHB + 2), is 0.25 ± 0.05 in the inner region of M30 (r < 20 ), significantly higher than the frequency found in other clusters: FBSS = 0.05 – 0.15. The shape of M30’s blue straggler luminosity function resembles the prediction of the collisional formation model and is inconsistent with the binary merger model, of Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Alfred P. Sloan Research Fellow