Long-lasting high state of the high-field polar AR UMa

Abstract

Using ASAS-SN Sky Patrol Photometic Database and Asteroid Terrestrial-impact Last Alert System (ATLAS) data, I found that the high-field polar AR UMa entered a long-lasting high state in 2022 October. This object is renowned for its small duty cycle, and short-lived high states have only been occasionally seen since the discovery. It appears that the present long-lasting high state is the first recorded one at least in the last 30 years and probably even more. Before entering the current long-lasting high state, this object showed three short-lived high states, which might have been precursors to the current state. Before these short-lived high states, the object had been in a low state for 8 years and probably more. I refined the orbital period to be 0.08050066(1) d. The object is still bright and current phenomenon provides a unique opportunity to study accretion processes onto a strongly magnetized white dwarf and to study the mechanism of maintaining the long-lasting high state.