Astron. Astrophys. 363, 1029-1039 (2000)

1. Introduction

Cataclysmic variables (CVs) are close binary systems consisting of a mass-accreting white dwarf and a mass donor secondary star which fills its Roche lobe. The accreting matter falls in a ballistic trajectory and can form an accretion disk around the white dwarf. Three subclasses are identified in non-magnetic CVs: novae, novalike stars, and dwarf novae. Dwarf novae display quasi-periodic outbursts that are believed to be caused by a thermal instability of the accretion disk (for a review see Warner 1995).

V893 Sco was originally discovered by Satyvoldiev (1972) as a suspected CV, but remained uncatalogued and unnoticed until 1998, when Katsumi Haseda, an amateur astronomer, re-discovered it in his photographic plates. This star was re-identified by Kato et al. (1998), who also utilized the fact that the object was detected by ROSAT as RXS 161516.2-283712 ( (J2000)).

The photometric behavior followed by Satyvoldiev (1982) was suggestive of repetitive dwarf nova outbursts. The object is usually around 13-14 mag in V-band and shows outbursts with an amplitude of around 2 mag, according to the current VSNET database ¹. Thorstensen (1999) obtained optical spectra of this object, and reported an orbital period of with a possible one-day alias of , i.e., just below the 2-3 h period "gap". The photometric study by Bruch et al. (2000) revealed shallow eclipses and the irregular flickering dominating the optical light curve.

We report in this paper our time-resolved spectroscopic and photometric observations of this object obtained in order to follow its orbital behavior and resolve its nature. The fact that the spectra are densely sampled in orbital phase permits us to perform a Doppler tomographic analysis of the emission lines (see e.g., Marsh & Horne 1988; Kaitchuck et al. 1994for more information).

© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000
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