Exploration of faint X-ray and radio sources in the massive globular cluster M14: A UV-bright counterpart to Nova Ophiuchus 1938

Abstract

Using a 12 ks archival Chandra X-ray Observatory ACIS-S observation on the massive globular cluster (GC) M14, we detect a total of 7 faint X-ray sources within its half-light radius at a 0.5-7 keV depth of $2.5\times 10^{31}\mathrm{erg}{\mathrm{s}}^{-1}$. We cross-match the X-ray source positions with a catalogue of the Very Large Array radio point sources and a Hubble Space Telescope (HST) UV/optical/near-IR photometry catalogue, revealing radio counterparts to 2 and HST counterparts to 6 of the X-ray sources. In addition, we also identify a radio source with the recently discovered millisecond pulsar PSR 1737-0314A. The brightest X-ray source, CX1, appears to be consistent with the nominal position of the classic nova Ophiuchi 1938 (Oph 1938), and both Oph 1938 and CX1 are consistent with a UV-bright variable HST counterpart, which we argue to be the source of the nova eruption in 1938. This makes Oph 1938 the second classic nova recovered in a Galactic GC since Nova T Scorpii in M80. CX2 is consistent with the steep-spectrum radio source VLA8, which unambiguously matches a faint blue source; the steepness of VLA8 is suggestive of a pulsar nature, possibly a transitional millisecond pulsar with a late K dwarf companion, though an active galactic nucleus (AGN) cannot be ruled out. The other counterparts to the X-ray sources are all suggestive of chromospherically active binaries or background AGNs, so their nature requires further membership information.

17 pages, 14 figures, accepted for publication in MNRAS

References in corpus (33)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• A Radio Pulsar/X-ray Binary Link
• Formation and evolution of compact binaries in globular clusters: II. Binaries with neutron stars
• A radio pulsing white dwarf binary star
• Improved Mass and Radius Constraints for Quiescent Neutron Stars in Omega Cen and NGC 6397
• The radio/X-ray domain of black hole X-ray binaries at the lowest radio luminosities
• Formation and evolution of compact binaries in globular clusters: I.Binaries with white dwarfs
• Chandra X-Ray Observations of Nineteen Millisecond Pulsars in the Globular Cluster 47 Tucanae
• High precision X-ray logN-logS distributions: implications for the obscured AGN population
• Millisecond Pulsars and Black Holes in Globular Clusters
• FAST Globular Cluster Pulsar Survey: Twenty-Four Pulsars Discovered in Fifteen Globular Clusters
• Identification of Faint Chandra X-ray Sources in the Core-Collapsed Globular Cluster NGC 6397: Evidence for a Bimodal Cataclysmic Variable Population
• The Quiescent X-ray Spectrum of Accreting Black Holes
• X-ray and optical observations of M55 and NGC 6366: evidence for primordial binaries
• The MAVERIC Survey: Chandra/ACIS Catalog of Faint X-ray sources in 38 Galactic globular clusters
• A Census of X-ray Millisecond Pulsars in Globular Clusters
• Combined Chandra, XMM-Newton and Hubble Space Telescope observations of the Galactic globular cluster NGC 2808
• Radio Variability from a Quiescent Stellar Mass Black Hole Jet
• Identification of Faint Chandra X-ray Sources in the Core-Collapsed Globular Cluster NGC 6752
• Follow-up Studies of Five Cataclysmic Variable Candidates Discovered by LAMOST
• Revealing the Field Sub-subgiant Population Using a Catalog of Active Giant Stars and Gaia EDR3
• The MAVERIC Survey: Radio catalogs and source counts from deep Very Large Array imaging of 25 Galactic globular clusters
• Radio detection of an elusive millisecond pulsar in the Globular Cluster NGC 6397
• Radio and optical observations of the possible AE Aqr twin, LAMOST J024048.51+195226.9
• Observational evidence for the origin of X-ray sources in globular clusters
• A Deep Search for Faint Chandra X-ray Sources, Radio Sources, and Optical Counterparts in NGC 6752
• A deep Chandra survey for faint X-ray sources in the Galactic globular cluster M30, and searches for optical and radio counterparts
• Radio detections of two unusual cataclysmic variables in the VLA Sky Survey
• A complete census of $H\alpha$ emitters in NGC 6397
• HST observations of the globular cluster NGC 6402 (M14) and its peculiar multiple populations
• The MAVERIC survey: A catalogue of radio sources in southern globular clusters from the Australia Telescope Compact Array
• Identifications of Faint Chandra Sources in the Globular Cluster M3

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