# Cyclic period oscillation of the eclipsing dwarf nova DV UMa

## TL;DR

This study reveals that the orbital period of the eclipsing dwarf nova DV UMa undergoes a cyclic oscillation likely caused by a circumbinary brown dwarf companion, based on 30 years of eclipse timing data.

## Contribution

It presents the first detection of a cyclic orbital period variation in DV UMa and attributes it to a circumbinary brown dwarf, using combined new and archival eclipse timings.

## Key findings

- Orbital period oscillates with a 17.58-year cycle.
- The companion's mass is approximately 0.025 solar masses.
- The companion likely is a brown dwarf orbiting at 8.6 AU with eccentricity 0.44.

## Abstract

DV UMa is an eclipsing dwarf nova with an orbital period of $\sim2.06$ 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 $\sim30$ 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 $17.58(\pm0.52)$ yr and an amplitude of $71.1(\pm6.7)$ 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 $M_{3}\sin{i'}=0.025(\pm0.004)M_{\odot}$. If the third body is in the orbital plane (i.e. $i'=i=82.9^{\circ}$) of the eclipsing pair, it would match to a brown dwarf. This hypothetical brown dwarf is orbiting its host star at a separation of $\sim8.6$ AU in an eccentric orbit ($e=0.44$).