SIMBAD references

2000ApJ...530L..21D - Astrophys. J., 530, L21-L24 (2000/February-2)

Ultracompact X-ray binaries in globular clusters: variability of the optical counterpart of X1832-330 in NGC 6652.


Abstract (from CDS):

Evidence is emerging that the luminous X-ray sources in the cores of globular clusters may often consist of, or perhaps even as a class be dominated by, ultracompact (P≲1 hr) binary stars. To the two such systems already known, in NGC 6624 and NGC 6712, we now add evidence for two more. We detect large-amplitude variability in the candidate optical counterpart for the X-ray source in the core of NGC 6652. Although the available observations are relatively brief, the existing Hubble Space Telescope data indicate a strong 43.6 minute periodic modulation of the visible flux of semiamplitude 30%. Further, although the orbital period of the source in NGC 1851 is not yet explicitly measured, we demonstrate that previous correlations of optical luminosity with X-ray luminosity and accretion disk size, strengthened by recent data, strongly imply that the period of that system is also less than 1 hr. Thus, currently there is evidence that four of the seven globular cluster X-ray sources with constrained periods are ultracompact, a fraction far greater than that found in X-ray binaries the field.

Abstract Copyright:

Journal keyword(s): Galaxy: Globular Clusters: Individual: NGC Number: NGC 6652 - Stars: Neutron - Ultraviolet: Stars - X-Rays: Bursts - X-Rays: Stars

CDS comments: X 1832-330 = RX J183544.0-325929

Simbad objects: 25

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