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arXiv · 1111.6775

A J-band detection of the donor star in the dwarf nova OY Carinae, and an optical detection of its `iron curtain'

C. M. Copperwheat·T. R. Marsh·S. G. Parsons·R. Hickman·D. Steeghs·E. Breedt·V. S. Dhillon·S. P. Littlefair·C. Savoury
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Abstract

Purely photometric models can be used to determine the binary parameters of eclipsing cataclysmic variables with a high degree of precision. However, the photometric method relies on a number of assumptions, and to date there have been very few independent checks of this method in the literature. We present time-resolved spectroscopy of the P=90.9 min eclipsing cataclysmic variable OY Carinae obtained with X-shooter on the VLT, in which we detect the donor star from K I lines in the J-band. We measure the radial velocity amplitude of the donor star K2 = 470.0 +/- 2.7 km/s, consistent with predictions based upon the photometric method (470 +/- 7 km/s). Additionally, the spectra obtained in the UVB arm of X-shooter show a series of Fe I and Fe II lines with a phase and velocity consistent with an origin in the accretion disc. This is the first unambiguous detection at optical wavelengths of the `iron curtain' of disc material which has been previously reported to veil the white dwarf in this system. The velocities of these lines do not track the white dwarf, reflecting a distortion of the outer disc that we see also in Doppler images. This is evidence for considerable radial motion in the outer disk, at up to 90 km/s towards and away from the white dwarf.

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C. M. Copperwheat, T. R. Marsh, S. G. Parsons, R. Hickman, D. Steeghs, E. Breedt, V. S. Dhillon, S. P. Littlefair, C. Savoury. 2011-11-29. A J-band detection of the donor star in the dwarf nova OY Carinae, and an optical detection of its `iron curtain'. https://doi.org/10.1111/j.1365-2966.2011.20282.x

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