gr photometry of NGC 5053 blue stragglers

New deep color-magnitude (C-M) diagrams to 23mag, constructed from photometry of over 6000 stars on 4-shooter CCD frames, show that they form a well-defined sequence in the C-M diagram, extending up to ~2.2mag brighter than the main-sequence turnoff point. The 12 most luminous blue stragglers are found to be significantly more centrally concentrated than the cluster subgiants with magnitudes in the same interval (a similar result is known for the blue stragglers in the globular cluster NGC 5466).

Furthermore, they are also found to be more centrally concentrated than the 12 lower luminosity blue stragglers. Comparisons of the projected radial distributions of the bright and faint blue stragglers, with the radial distributions that are expected for stars of mass 0.8, 1.6, and 2.4M_{sun}_, (calculated using multimass King models) suggests that the brightest blue stragglers have an average mass of <M>=1.3+/0.3M_{sun}_, which is less than or comparable to twice the mean mass of a main-sequence turnoff star, and the lower luminosity blue stragglers have a mean mass similar to that of the main-sequence turnoff stars (i.e., M~0.8M_{sun}_).