Cyclic period oscillation of the eclipsing dwarf nova DV UMa

Abstract

DV UMa is an eclipsing dwarf nova with an orbital period of $\sim 2.06$ h, which lies just at the bottom edge of the period gap. To detect its orbital period changes we present 12 new mid-eclipse times by using our CCD photometric data and archival data. Combining with the published mid-eclipse times in quiescence, spanning $\sim 30$ yr, the latest version of the $O-C$ diagram was obtained and analyzed. The best fit to those available eclipse timings shows that the orbital period of DV UMa is undergoing a cyclic oscillation with a period of $17.58(\pm 0.52)$ yr and an amplitude of $71.1(\pm 6.7)$ s. The periodic variation most likely arises from the light-travel-time effect via the presence of a circumbinary object because the required energy to drive the Applegate mechanism is too high in this system. The mass of the unseen companion was derived as $M_3\sin i^{\prime }=0.025(\pm 0.004)M_{\odot }$. If the third body is in the orbital plane (i.e. $i^{\prime }=i=82.9^{\circ }$) of the eclipsing pair, it would match to a brown dwarf. This hypothetical brown dwarf is orbiting its host star at a separation of $\sim 8.6$ AU in an eccentric orbit ($e=0.44$).

16 pages, 6 figures

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