A deep Chandra survey for faint X-ray sources in the Galactic globular cluster M30, and searches for optical and radio counterparts

Abstract

We present a deep ($\sim 330\mathrm{ks}$) {\it Chandra} survey of the Galactic globular cluster M30 (NGC 7099). Combining the new Cycle 18 with the previous Cycle 3 observations we report a total of 10 new X-ray point sources within the $1.03$ arcmin half-light radius, compiling an extended X-ray catalogue of a total of 23 sources. We incorporate imaging observations by the {\it Hubble Space Telescope} and the {\it Karl G. Jansky Very Large Array} from the MAVERIC survey to search for optical and radio counterparts to the new and old sources. Two X-ray sources are found to have a radio counterpart, including the known millisecond pulsar PSR J2140$-$2310A, the radio position of which also matches a previously reported faint optical counterpart which is slightly redder than the main sequence. We found optical counterparts to $18$ of the $23$ X-ray sources, identifying $2$ new cataclysmic variables (CVs), $5$ new CV candidates, $2$ new candidates of RS CVn type of active binary (AB), and $2$ new candidates of BY Dra type of AB. The remaining unclassified X-ray sources are likely background active galactic nuclei (AGN), as their number is consistent with the expected number of AGN at our X-ray sensitivity. Finally, our analysis of radial profiles of different source classes suggests that bright CVs are more centrally distributed than faint CVs in M30, consistent with other core-collapsed globular clusters.

24 pages, 12 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

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Cited by in corpus (7)

• A Census of X-ray Millisecond Pulsars in Globular Clusters
• Two New Black Widow Millisecond Pulsars In M28
• A Deep Search for Faint Chandra X-ray Sources, Radio Sources, and Optical Counterparts in NGC 6752
• The MAVERIC Survey: The first radio and X-ray limits on the detached black holes in NGC 3201
• Reevaluating the Origin of Detectable Cataclysmic Variables in Globular Clusters: Testing the Importance of Dynamics
• Exploration of faint X-ray and radio sources in the massive globular cluster M14: A UV-bright counterpart to Nova Ophiuchus 1938
• Far-ultraviolet investigation into the galactic globular cluster M30 (NGC 7099): II. Potential X-ray counterparts and variable sources