V893 Scorpii:
The brightest eclipsing cataclysmic variabel below the period gap ⁽¹⁾

Albert Bruch - João E. Steiner - Clemens Gneiding

Laboratório Nacional de Astrofísica, C.P. 21, CEP 37500-000, Itajubá - MG, Brazil; albert@lna.br

Abstract:

We report about the first time resolved photometric observations of the bright dwarf nova V893 Sco. The optical light curves show eclipses recurring with a period of 1^h 49^m 23^s which are probably caused mainly by the hot spot while the accretion disk centre with the white dwarf remains uneclipsed. The light curves show considerable cycle to cycle variations concerning the mean magnitude, the strength of the orbital hump, the presence of an intermediate hump, and the amplitude and minimum depth of the eclipses. Light curves in the J and H bands are essentially constant without ellipsoidal variations of the secondary star. Surprisingly there is no sign of an eclipse at these wavelengths. V893 Sco exhibits a strong flickering activity with statistical properties which are remarkably stable when compared to other cataclysmic variables. The short time scale flickering (<0.01 P_orb ) is not confined to the accretion disk but contains a contribution from the hot spot. During one night an oscillation with a period of 5.71 +- 0.02  min was observed. A beat with the orbital period may also be present. A spectrum taken in the range of H shows the double peaked Balmer emission typical for high inclination dwarf novae and permits to predict the presence of a strong S-wave in time resolved spectroscopy, consistent with the prominent orbital hump in the light curves. The oscillations, the properties of the flickering, the presence of He II emission and the hard x-rays seen by ROSAT suggest a connection of V893 Sco to intermediate polars; but there is not yet conclusive evidence for such a classification.

Stars: variables: general - binaries: eclipsing - novae, cataclysmic variables - Stars: individual: V893 Sco