robust model for the origin of optical quasi-periodic variability in supersoft X-ray sources

Supersoft X-ray sources (SSSs) are known as possible progenitors of Type Iasupernovae. The quasi-periodic variability has been detected in the opticallight curves of SSSs. However, the exact origin of such quasi-periodicobservable features remains a mystery. In this paper, we aim to reproduce theobserved optical quasi-periodic variability of SSSs by proposing a white dwarf(WD) accretion model with a periodic mass transfer caused by the irradiation ofsupersoft X-ray onto the companion star. Methods. Assuming that a periodic masstransfer from the companion star to the WD can be caused while the supersoftX-ray irradiates the companion star, we used MESA to simulate the WD accretionprocess and the subsequent WD evolution by adopting a periodic jagged accretionrate. Comparing our results to the optical light curves of a well-observed SSSRX J0513.9-6951, we find that our models can reproduce the quasi-periodictransition between the optical high and low states of RX J0513.9-6951 becausethe periodic accretion rate can lead to the WD photosphere expands andcontracts periodically in our models. In addition, we find that thetransitional periods of the SSSs in our models strongly depend on the mass ofthe accreting WDs. The more massive the WD mass is, the shorter thetransitional period. Based on our results, we suggest that the periodic masstransfer caused by the irradiation of supersoft X-ray onto the companion starmay be the origin of the observed optical quasi-periodic variability in SSSs.In addition, our results indicate that the observed optical transition periodof a SSS may be useful for the rough estimate of the mass of an accreting WD.