TESS light curves of cataclysmic variables I -- Unknown periods in long-known stars

TL;DR

This study uses TESS light curves to identify new periodic phenomena in cataclysmic variables, revealing that superhumps are common and providing new orbital period measurements, including the first detection of the white dwarf spin in TV Col.

Contribution

It presents the first systematic search for periodic variations in CVs using TESS data, discovering new superhumps and measuring orbital periods with improved accuracy.

Findings

Superhumps are common in the studied CVs.

New orbital periods are measured for 8 systems.

First optical detection of the white dwarf spin in TV Col.

Abstract

Cataclysmic variables (CVs) exhibit a plethora of variable phenomena many of which require long, uninterrupted light curves to reveal themselves in detail. The month long datasets provided by TESS are well suited for this purpose. TESS has the additional advantage to have observed a huge number of stars, among them many CVs. Here, a search for periodic variations in a sample of CVs of the novalike and old novae subtypes is presented. In 10 of the 15 targets either previously unseen positive or negative superhumps or unusual features in known superhumps are identified. The TESS light curves demonstrate that the occurrence of superhumps in these types of CVs is not an exception but quite common. For 8 systems new or improved values for the orbital period are measured. In TV Col the long-sought optical manifestation of the white dwarf spin period is first seen in form of its orbital sideband. The mystery of multiple photometric periods observed in CP Pup in the past is explained by irregularly occurring anomalous states which are reflected in the light curve.