Investigation of WZ Sge-type Dwarf Nova ASASSN-19oc: Optical Spectroscopy and Multicolor Light Curve Analysis

Abstract

In this study, we present an investigation of the newly discovered dwarf nova ASASSN-19oc during its superoutburst on 2019 June 2. We carried out detailed UBVRcIc-photometric observations and also obtained a spectrum on day 7 of the outburst, which shows the presence of hydrogen absorption lines commonly found in dwarf nova outbursts. Analysis of photometric data reveals the occurrence of early superhumps in the initial days of observations, followed by ordinary and late superhumps. We have accurately calculated the period of the ordinary superhumps as Pord = 0.05681(10) days and determined the periods at different stages, as well as the rate of change of the superhump period (Pdot = /P = 8.1 × 10−5). Additionally, we have derived the mass ratio of the components (q = 0.09), and estimated the color temperature during the outburst as ∼11,000 K, the distance to the system (d = 560 pc) and absolute magnitude of the system in outburst (MV = 5.3). We have shown that outbursts of this star are very rare: based on brightness measurements on 600 archival photographic plates, we found only one outburst that occurred in 1984. This fact, as well as the properties listed above, convincingly shows that the variable ASASSN-19oc is a dwarf nova of WZ Sge type.