Characteristics of the Permanent Superhumps in V533 Herculis

Abstract

We analyze two sectors of TESS photometry of the nova-like cataclysmic variable star V533 Her. We detect a periodicity consistent with the binary orbital period and estimate a revised value of 3.53709(2) hr. We also detect a strong signal near a period of 3.8 h that we associate with positive superhumps. The superhump frequency varies over the TESS observations with the fractional difference between the superhump and orbital periods, $\hat{I}\mu$, ranging between $0.055\le \hat{I}\mu \le 0.080$. The superhump amplitude is correlated with its frequency such that the amplitude increases as $\hat{I}\mu$ decreases. Positive superhumps result from an instability that generates an eccentric accretion disk and $\hat{I}\mu$ is a measure of the disk precession rate in the binary rest frame. The observed correlation implies that as the disk precession rate slows, the disk eccentricity increases.

4 pages, 1 figure, accepted for publication in the RNAAS