UV spectroscopy of the X-ray binary AC211 ( = 4U2127 + 11) in M15⋆
Open Access
- 1 March 1992
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 255 (1) , 1-6
- https://doi.org/10.1093/mnras/255.1.1
Abstract
We present time-resolved International Ultraviolet Explorer observations of the low-mass X-ray binary AC211/4U2127 + 11 in the globular cluster M15 (NGC 7078). The spectra show He II 1640-Å emission, the flux of which is modulated on the 8.5-hr orbital period of AC211. This modulation, and the ratio of He II 1640 Å to He II 4686 Å and C IV 1550 Å imply that the He II lines originate in an accretion disc corona. In addition there are absorption lines typical of hot stars, but it is unclear whether they originate in AC211, or surrounding horizontal branch stars. Finally, we compare the reddening derived from the 2200-Å feature in our spectra with earlier determinations.Keywords
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