TESS light curves of cataclysmic variables – III – More superhump systems among old novae and nova-like variables

Abstract

ABSTRACT Continuing previous work on the identification and characterization of periodic and non-periodic variations in long and almost uninterrupted high cadence light curves of cataclysmic variables observed by the Transiting Exoplanet Survey Telescope mission, the results on 23 nova-like variables and old novae out of sample of 127 such systems taken from the Ritter & Kolb catalogue are presented. All of them exhibit at least at some epochs either positive or negative (or both) superhumps, and in 19 of them superhumps were detected for the first time. The basic properties of the superhumps such as their periods, their appearance and disappearance, and their waveforms are explored. Together with recent reports in the literature, this elevates the number of known nova-like variables and old novae with superhumps by more than 50 per cent. The previous census of superhumps and the Stolz–Schoembs relation for these stars are updated. Attention is drawn to superhump properties in some stars that behave differently from the average, as well as to positive superhumps in high-mass ratio systems that defy theory. As a by-product, the orbital periods of 13 stars are either improved or newly measured, correcting previously reported erroneous values.