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arXiv · 1203.5971

A second neutron star in M4?

J. Kaluzny·A. Rozanska·M. Rozyczka·W. Krzeminski·I. B. Thompson
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Abstract

We show that the optical counterpart of the X-ray source CX 1 in M4 is a 20th magnitude star, located in the color-magnitude diagram on (or very close to) the main sequence of the cluster, and exhibiting sinusoidal variations of the flux. We find the X-ray flux to be also periodically variable, with X-ray and optical minima coinciding. Stability of the optical light curve, lack of UV-excess, and unrealistic mean density resulting from period-density relation for semidetached systems, speak against the original identification of CX 1 as a cataclysmic variable. We argue that the X-ray active component of this system is a neutron star (probably a millisecond pulsar).

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J. Kaluzny, A. Rozanska, M. Rozyczka, W. Krzeminski, I. B. Thompson. 2012-03-27. A second neutron star in M4?. https://doi.org/10.1088/2041-8205%2F750%2F1%2Fl3

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