X-ray and UV Variability in the Core of M15: the nature of X2127+119/AC211

P. A. Charles; W. I. Clarkson; L. van Zyl

doi:10.1016/s1384-1076(01)00087-2

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X-ray and UV Variability in the Core of M15: the nature of X2127+119/AC211

P. A. Charles·W. I. Clarkson·L. van Zyl

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Abstract

The prototypical post-core-collapse globular cluster M15 provides an ideal environment for the formation of exotic binaries, it being already known to contain a luminous LMXB (X2127+119, optically identified with the 17.1 hour eclipsing binary AC211) and six millisecond pulsars in the core. However, the X-ray properties of X2127+119 are strange in that it appears to be a high inclination accretion disc corona source (ADC) from which we only see scattered X-radiation, and yet it has produced extremely luminous type I X-ray bursts, which may or may not have come from AC211. We have therefore examined the 5-year RXTE/ASM light curve of this object in order to search for long-term modulations which might shed light on this unusual behaviour, and which led to our discovery of further X-ray bursts. Furthermore we have used archival HST UV images of the M15 core to search for other variable objects which might indicate the presence of a second LMXB. From these we have found one highly variable (> 5 mag) object which we interpret as a dwarf nova.

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P. A. Charles, W. I. Clarkson, L. van Zyl. 2001-10-11. X-ray and UV Variability in the Core of M15: the nature of X2127+119/AC211. https://doi.org/10.1016/s1384-1076(01)00087-2

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