Identification of Faint Chandra X-Ray Sources in the Core-collapsed Globular Cluster NGC 6752

Journal Article · Sat May 20 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA6C56· OSTI ID:22872687

Lugger, Phyllis M.; Cohn, Haldan N. ^[1]; Cool, Adrienne M. ^[2]; Heinke, Craig O. ^[3]; Anderson, Jay ^[4]

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1. Department of Astronomy, Indiana University, 727 E. Third Street, Bloomington, IN 47405 (United States)
2. Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132 (United States)
3. Department of Physics, University of Alberta, Edmonton, AB T6G 2G7 (Canada)
4. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

We have searched for optical identifications for 39 Chandra X-ray sources that lie within the 1.′9 half-mass radius of the nearby (d=4.0 kpc), core-collapsed globular cluster, NGC 6752, using deep Hubble Space Telescope ACS/WFC imaging in B {sub 435}, R{sub 625}, and Hα. Photometry of these images allows us to classify candidate counterparts based primarily on color–magnitude and color–color diagram location. The color–color diagram is particularly useful for quantifying the Hα-line equivalent width. In addition to recovering 11 previously detected optical counterparts, we propose 20 new optical IDs. In total, there are 16 likely or less certain cataclysmic variables (CVs), 9 likely or less certain chromospherically active binaries, 3 galaxies, and 3 active galactic nuclei. The latter three sources, which had been identified as likely CVs by previous investigations, now appear to be extragalactic objects based on their proper motions. As we previously found for NGC 6397, the CV candidates in NGC 6752 fall into a bright group that is centrally concentrated relative to the turnoff-mass stars and a faint group that has a spatial distribution that is more similar to that of the turnoff-mass stars. This is consistent with an evolutionary scenario in which CVs are produced by dynamical interactions near the cluster center and diffuse to larger radius orbits as they age.

• OSTI ID: 22872687
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 841; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
GALAXIES
GALAXY NUCLEI
IMAGES
MASS
NOVAE
ORBITS
PHOTOMETRY
PROPER MOTION
SPACE
SPATIAL DISTRIBUTION
TELESCOPES
X RADIATION
X-RAY SOURCES