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Time-resolved Spectroscopy of the M15 X-ray Binary AC211/X2127+119

M. A. P. Torres·P. J. Callanan·M. R. Garcia
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Abstract

We present time-resolved spectroscopy acquired during two epochs (spaced apart by ~15 days) of the eclipsing Low Mass X-ray Binary AC211/X2127+119 in the globular cluster M15. The spectra show variations in the HeII 4686 emission line not only modulated on the orbital period, but also on time-scales of a few days. During the first epoch of observation, the emission line shows a strong S-wave superimposed on the average double-peaked profile. The line exhibits no evidence of rotational disturbance at the orbital phases when the eclipse is observed in the optical continuum. During the second epoch, no double-peak or S-wave component is present. The HeI absorption lines detected by other authors are not present in our spectra. A Doppler image of the HeII 4686 for the first epoch supports the presence of the accretion disc. No hotspot is detected, although enhanced emission at V_X=30km/s, V_Y=160 km/s is observed. We discuss the implications of this emission in the context of an X-ray heated donor star, in which case a high mass ratio and neutron star primary are implied. Finally, we speculate on the possibility of a misaligned secondary star in AC211.

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M. A. P. Torres, P. J. Callanan, M. R. Garcia. 2003-02-05. Time-resolved Spectroscopy of the M15 X-ray Binary AC211/X2127+119. https://doi.org/10.1046/j.1365-8711.2003.06486.x

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