TESS and ZTF Observations of an Eclipsing Z Cam-type Dwarf Nova IPHAS J051814.34+294113.2

Abstract We present an analysis of both Transiting Exoplanet Survey Satellite (TESS) and Zwicky Transient Facility (ZTF) observations of the eclipsing cataclysmic variable IPHAS J051814.34+294113.2 (IPHAS J0518). The TESS light curve shows numerous eclipses superimposed on two outbursts, and ZTF data show frequently outbursts recurring on average every 20.7 days and 12.9 days for long and short outbursts, respectively. This makes IPHAS J0518 to be identified as a possible Z Cam-type dwarf nova. Its quiescent magnitude is ∼16.7 in the g band. The orbital period is determined to be 4.95 hr. By combining the observed orbital period with the semiempirical relations of Knigge et al., we estimate the donor mass as M 2 = 0.48M ⊙. The eclipse phase measurements are used to constrain the binary parameters. The orbital inclination is limited in the range of 75.°3 ≤ i < 81.°7, and the mass ratio is derived as 0.33 < q ≤ 0.73. Furthermore, we analysis the accretion disk eclipse and find that the total disk eclipse is possible during quiescence, whereas during outburst the disk would be only partially obscured. This indicates that the disk will become larger as the outburst proceeds. We also study the changes of the eclipse depth against the out-of-eclipse flux in IPHAS J0518. The results show evidence of the expansion in the disk size and the variations in the radial-temperature gradient during outburst.