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X-ray and Optical Eclipses in ULXs as Possible Indicators of Black Hole Mass

David Pooley·Saul Rappaport
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Abstract

Ultraluminous X-ray sources (ULXs) with 10^39 < L_x < 10^41 erg/s have been discovered in great numbers in external galaxies with ROSAT, Chandra, and XMM-Newton. The central question regarding this important class of sources is whether they represent an extension in the luminosity function of binary X-ray sources containing neutron stars and stellar-mass black holes (BHs), or a new class of objects, e.g., systems containing intermediate-mass black holes (100 - 1000 M_sun). We suggest searching for X-ray and optical eclipses in these systems to provide another diagnostic to help distinguish between these two possibilities. The sense of the effect is that ULXs with stellar-mass black hole accretors should be at least twice as likely to exhibit eclipses as intermediate-mass black hole systems - and perhaps much more than a factor of two. Among other system parameters, the orbital period would follow. This would provide considerable insight as to the nature of the binary.

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David Pooley, Saul Rappaport. 2005-09-20. X-ray and Optical Eclipses in ULXs as Possible Indicators of Black Hole Mass. https://doi.org/10.1086/498613

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