The 2015 superoutburst of QZ Virginis: Detection of growing superhumps between the precursor and main superoutburst

TL;DR

This study presents detailed observations of the 2015 superoutburst of QZ Virginis, identifying long-lasting growing superhumps and estimating the system's mass ratio, providing insights into its evolutionary status.

Contribution

The paper reports the first detection of growing superhumps between the precursor and main superoutburst in QZ Virginis and links superhump duration to system parameters.

Findings

Detected superhumps with a period of 0.061181 days.

Estimated the mass ratio of QZ Vir as 0.108.

Long-lasting stage A superhumps suggest a specific evolutionary stage.

Abstract

We report on time-resolved photometry of the 2015 February-March superoutburst of QZ Virginis. The superoutburst consisted of a separated precursor, main superoutburst, and rebrightening. We detected superhumps with a period of 0.061181(42) d between the precursor and main superoutburst. Based on analyses of period changes and amplitudes of superhumps, the observed superhumps were identified as growing superhumps (stage A superhumps). The duration of stage A superhumps was about 5 d, unusually long for SU UMa-type dwarf novae. Using the obtained stage A superhump period, we estimated the mass ratio of QZ Vir to be 0.108(3). This value suggests that QZ Vir is an SU UMa-type dwarf nova evolving toward the period minimum. Based on the present and the previous observations regarding long-lasting stage A superhumps, a time scale of stage A superhumps is likely to be determined by the mass ratio of the system and the temperature of the accretion disk.