A second neutron star in M4?
Solar and Stellar Astrophysics
2012-04-16 v1
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).
Cite
@article{arxiv.1203.5971,
title = {A second neutron star in M4?},
author = {J. Kaluzny and A. Rozanska and M. Rozyczka and W. Krzeminski and I. B. Thompson},
journal= {arXiv preprint arXiv:1203.5971},
year = {2012}
}
Comments
11 pages, 4 figures, accepted by ApJ Letters