Cyclic period oscillation of the eclipsing dwarf nova DV UMa
  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 ($e=0.44$).
