Long‐Term Brightness Variations of Quiescent Dwarf Novae

Abstract

ABSTRACT Dwarf novae (DNe) are true laboratories for accretion physics, since their gas disks can be observed and modeled during both outburst and quiescence in the same star. Most of past research was dedicated to DNe outbursts while their quiescent state was widely neglected. We are complementing the only two previous studies existing in this field with a new systematic search for significant long‐term variability of DNe during quiescence, based on the Gaia alerts database. Two fitting approaches for the photometric data (magnitude vs. time) were used: a linear fit or a combined sinusoidal‐linear fit, depending on the observed variability of the target. We identified a total of 138 DNe with significant linear variability, with an average slope of 0.16 mag per year. Additionally, for other 49 DNe the sinusoidal fit revealed periods between 590 and 3320 days and average peak‐to‐peak sine amplitudes of ˜0.4 mag. In nearly all these targets, their long‐term variability is new, never reported previously. We estimate that about 10% of the DNe population reveals long‐term variations. The most probable explanation of these variations could be the changing magnetic field of the companion star, like the well‐known 11‐year cycle of solar activity.