Very low state in PY Per in 2022

TL;DR

This paper reports a prolonged low state in the Z Cam star PY Per in 2022, with observations indicating nearly halted mass transfer and potential links to recent superoutburst activity, suggesting PY Per is a VY Scl star.

Contribution

It provides the first detailed observation of a low state in PY Per, linking it to VY Scl stars and proposing a physical connection to recent superoutburst phenomena.

Findings

PY Per experienced a faint low state reaching 19.1 mag.

No dwarf nova outbursts occurred during the low state.

TESS data revealed ellipsoidal modulation consistent with secondary star effects.

Abstract

Using VSNET, VSOLJ, ASAS-SN and ATLAS observations, I found that the Z Cam star PY Per spent a long, faint low state reaching 19.1 mag at least between 2022 June and November. No dwarf nova outburst was recorded during this interval. TESS data during this low state showed two maxima in one orbital cycle and can be interpreted as an ellipsoidal modulation arising from the secondary. These observations suggest that the mass-transfer almost stopped during this low state and strengthen the identification of PY Per as a VY Scl star. PY Per had shown an unusual outburst resembling an SU UMa-type superoutburst less than half a year before (Kato 2022, arXiv:2204.12056) and these phenomena may have been physically related.