Accretion States in Magnetic CVs: TESS and ground-based photometry

Recent work on magnetic CVs is presented, with a focus on accretion states observed in TESS photometry. TESS data consists of red/IR photometry consisting of a continuous data stream with 2 minute cadence. When possible the TESS data is supplemented by high-speed (1-5 sec cadence) photometry using the 2.1-m telescope of the McDonald Observatory. Asynchronous polars (AP) and intermediate polars (IPs) with slowing rotating white dwarfs, hereafter slowly rotating IPs, are especially useful targets for TESS studies. This is because APs and slowly rotating IPs have beat periods that last from days to weeks. TESS provides continuous coverage across the beat cycle for these binaries. In addition, since the TESS exposure time of 2-min is long compared to the spin periods of the rapidly rotating IPs, TESS is better suited to the study of IPs with longer white dwarf spin periods. In the Interactive Magnetic Value Model proposed to explain mass transfer variations in APs, the strong magnetic field of the white dwarf interacts with the moderate magnetic field of the rapidly spinning donor star. The superposition of the fields of both stars at the inner Lagrangian point (L1) may either inhibit or enhance mass transfer through L1, depending on the orientation of the resultant field. Rapid accretion rate variations are observed in polars, initiating high or low accretion states, and in some IPs, and may be explained by rapid changes in the magnetic field at L1 affecting the mass-transfer rate. A combination of published and new results on the following magnetic CVs are presented: BY Cam, CD Ind, V1500 Cyg, SDSS J134441.83+204408.3, Paloma, and J084617.11+245344.1.