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Volume 398, Number 1, January IV 2003
Page(s) 267 - 275
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20021644

A&A 398, 267-275 (2003)
DOI: 10.1051/0004-6361:20021644

Discovery of a coherent 87.65-minute oscillation of the suspected cataclysmic variable NSV 2872 (Aur 2)

V. P. Kozhevnikov

Astronomical Observatory, Ural State University, Lenin Av. 51, Ekaterinburg, 620083, Russia
(Received 16 July 2002 / Accepted 7 November 2002 )

We report discovery of a low-amplitude optical oscillation at a period of 87.65 min of the suspected cataclysmic variable NSV 2872 . During a month of our observations the oscillation was strictly periodic while the amplitude appeared highly variable. Recently Liu & Hu (2000) revealed that the spectrum of this star is not typical of cataclysmic variables, and it is simply an early-K type star. In this connexion the observed oscillation seems rather puzzling. The period and amplitude of the oscillation are typical of the $\delta$ Sct variables, but both the spectrum and the colour of this star indicate that NSV 2872 is outside the instability strip. Our observations of NSV 2872 reveal sure signs of the flickering which is a hallmark of the cataclysmic variables though the activity of the flickering in this star seems rather low. Also the highly variable amplitude of the observed oscillation is typical of the intermediate polar subclass of cataclysmic variables. If NSV 2872 is considered as a cataclysmic variable, it is unlikely that the 87.65-min oscillation can be related to the orbital period of the system since cataclysmic variables with K type secondaries of normal chemical compositions can not have such short orbital periods. Hence, NSV 2872 is probably a new intermediate polar.

Key words: stars: individual: NSV 2872 -- stars: novae, cataclysmic variables -- stars: oscillations

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© ESO 2003