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Oxford University Press, Monthly Notices of the Royal Astronomical Society, 3(442), p. 2381-2391, 2014

DOI: 10.1093/mnras/stu930

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The M 4 Core Project with HST - III. Search for variable stars in the primary field

Journal article published in 2014 by V. Nascimbeni ORCID, L. R. Bedin ORCID, D. C. Heggie, M. van den Berg, M. . Den, M. Giersz, G. Piotto ORCID, K. Brogaard, A. Bellini, A. P. Milone ORCID, R. M. Rich, D. Pooley, J. Anderson, L. Ubeda, S. Ortolani and other authors.
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

We present the results of a photometric search for variable stars in the core of the Galactic globular cluster Messier 4 (M 4). The input data are a large and unprecedented set of deep Hubble Space Telescope WFC3 images (large programme GO-12911; 120 orbits allocated), primarily aimed at probing binaries with massive companions by detecting their astrometric wobbles. Though these data were not optimized to carry out a time-resolved photometric survey, their exquisite precision, spatial resolution and dynamic range enabled us to firmly detect 38 variable stars, of which 20 were previously unpublished. They include 19 cluster-member eclipsing binaries (confirming the large binary fraction of M 4), RR Lyrae and objects with known X-ray counterparts. We improved and revised the parameters of some among published variables.