Photometric Studies of the Intermediate Polar DO Dra in 2008 and 2019

Abstract

An analysis is presented of photometric observations of the intermediate polar DO Dra obtained during an epoch of significant reduction in its outburst activity for different average brightnesses of the system: 13m.6-12m.8 (2008) and 14m.7-14m.3 (2019). The observations in 2008 were made in the Johnson BVR system and in 2019, in integrated light. For the first time in quasi-simultaneous observations in the BVR bands, orbital modulation of the brightness was recorded in the form of a two-humped curve in each band, presumably caused by ellipsoidality of the secondary component. For six nights in the BVR bands (2008) and one night in integrated light (2019), stable quasiperiodic oscillations around 0.02 days were observed. On the night of JD 2458575 (2019) an increase in the brightness by 0m.7 was observed over 3 min, followed by exponential decay. The flare lasted about an hour within the first half of which oscillations with a period of about 0.006 days and an amplitude of 0m.1 were observed that may be related either to the rotation period of the white dwarf or to the quasiperiodic oscillations. The nature of the flare is not yet clear and possible reasons for this effect are examined in this article.