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Period derivative of the M15 X-ray Binary AC211/X2127+119

L. Homer·P. A. Charles
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Abstract

We have combined Rossi X-ray Timing Explorer observations of X2127+119, the low-mass X-ray binary in the globular cluster M15, with archival X-ray lightcurves to study the stability of the 17.1 hr orbital period. We find that the data cannot be fit by the Ilovaisky (1993) ephemeris, and requires either a 7sigma change to the period or a period derivative Pdot/P~9x10e-7 per year. Given its remarkably low L_X/L_opt such a Pdot lends support to models that require super-Eddington mass transfer in a q~1 binary.

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L. Homer, P. A. Charles. 1998-08-28. Period derivative of the M15 X-ray Binary AC211/X2127+119. https://doi.org/10.1016/s1384-1076(98)00026-8

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