Periodic modulations during a long outburst in V363 Lyr

TL;DR

This study analyzes Kepler data of V363 Lyr, identifying persistent orbital periods and long outburst modulations, exploring their origins as superhumps or tidal effects, and discussing implications for the system's mass ratio and secondary star.

Contribution

It presents the first detailed analysis of V363 Lyr's long and short cadence Kepler data, revealing long-period modulations and proposing interpretations related to superhumps and tidal interactions.

Findings

Detected a persistent orbital period of 0.185723 days.

Observed a long outburst with embedded precursor and modulations at 0.1956 days.

Discussed possible origins of long-period variations as superhumps or tidal effects.

Abstract

I analyzed the Kepler long and short cadence data of V363 Lyr. A period of 0.185723(8) d was persistently detected and this is identified as the orbital period. V363 Lyr showed one long outburst accompanied by an "(embedded) precursor" during Kepler observations and modulations with a period of 0.1956(2) d, longer than the orbital one, were detected during this outburst. There are two possible interpretations of this period. The first one is superhumps despite that V363 Lyr is far above the period gap. This interpretation requires an evolved, undermassive secondary enabling a low mass ratio of q=0.15. The evolution of this long-period variations, however, does not follow the standard evolution of superhumps. The second one is that the precursor occurred when the disk reached the tidal truncation radius, as inferred from observations of IW And stars. In this case, the long-period variations could be interpreted as a variable stream impact on a precessing eccentric disk, which may have been formed by disturbances at the tidal truncation radius. This might lead to effective removal of the angular momentum which resulted in 0.3-0.4 mag brightening following the precursor. The fractional period excess suggests that q is just above the stability limit of the 3:1 resonance. In either cases, the nature of the secondary and the mass ratio need to be verified by spectroscopic observations.