Open AccessTime‐resolved spectroscopy of the M15 X‐ray binary AC211/X2127+119
Author(s) -
Torres M. A. P.,
Callanan P. J.,
Garcia M. R.
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06486.x
Subject(s) - physics , astrophysics , neutron star , emission spectrum , orbital period , x ray binary , spectral line , spectroscopy , astronomy , eclipse , orbital elements , line (geometry) , stars , geometry , mathematics
We present time‐resolved spectroscopy acquired during two epochs (spaced apart by ∼15 d) of the eclipsing low‐mass X‐ray binary AC211/X2127+119 in the globular cluster M15. The spectra show variations in the He ii λ4686 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 He i absorption lines detected by other authors are not present in our spectra. A Doppler image of He ii λ4686 for the first epoch supports the presence of the accretion disc. No hotspot is detected, although enhanced emission at V X = 30 km s −1 , V Y = 160 km s −1 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.