Period Bouncer Cataclysmic Variable EZ Lyn in Quiescence

Abstract

Abstract We report the study of the accretion disk structure of the period bouncer cataclysmic variable EZ Lyn (SDSS J080434.20+510349.2) in quiescence based on our new time-resolved photometric and spectroscopic observations and data extracted from archives. The object magnitude now is V = 17.95(5), close to its brightest before the first superoutburst in 2006. We confirmed the presence of the small eclipse in the optical light curve. The spectra obtained in quiescence at different epochs look similar. However, the contribution of the disk and intensities of emission lines are strongly varied. We singled out pure accretion disk spectra and found that the Balmer decrement Hα:Hβ:Hγ:Hδ = 1.61:1.0:0.76:0.59 is comparable with one at bright accretion disks in longer period cataclysmic variables. The decrement suggests that emission lines are excited collisionally in an optical thin part of the disk with average density and temperature of logN 0 = 12.5(2) and T = (10–15) × 103 K. Based on the photometric data and our modeling techniques, we redetermined the mass of M WD = 0.85(1) M ⊙ and the current effective temperature T WD,eff = 11,250(50) K of the white dwarf. The secondary has mass of M 2 = 0.042(14) M ⊙. The system inclination is 79.0°(2). The mass accretion rate is about M ̇ ≈ ( 0.3 – 3.0 ) × 10 − 12 M ⊙ yr−1. The disk luminosity, together with results from light-curve modeling, suggests a low effective temperature ∼2500 K of the continuum emitting region, where also the spiral arm pattern is hosted.