A SECOND NEUTRON STAR IN M4?

Journal Article · Tue May 01 00:00:00 EDT 2012 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/750/1/L3· OSTI ID:22047872

Kaluzny, J; Rozanska, A; Rozyczka, M; Krzeminski, W ^[1]; Thompson, Ian B ^[2]

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1. Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland)
2. Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

We show that the optical counterpart of the X-ray source CX 1 in M4 is a {approx}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).

• OSTI ID: 22047872
• Journal Information: Astrophysical Journal Letters, Vol. 750, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASTRONOMY
ASTROPHYSICS
COLOR
COSMIC PHOTONS
COSMIC X-RAY SOURCES
DENSITY
DIAGRAMS
MAIN SEQUENCE STARS
NEUTRON STARS
PERIODICITY
PULSARS
STABILITY
VISIBLE RADIATION
X RADIATION