Comparison of the disk precession models with the photometric behavior of TT Ari in 2021-2023

¹ Institut für Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
² Parallax Enterprise, Kazan, Russia
³ American Association of Variable Star Observers, 49 Bay State Road, Cambridge, MA 02138, USA
⁴ AstroMallorca, Palma, Balearic Islands, Spain
⁵ Space Physics and Astronomy research unit, PO Box 3000 FIN-90014 University of Oulu, Finland

Received: 20 March 2024
Accepted: 19 August 2024

Abstract

We present a comparative analysis of photometric observations of the cataclysmic variable TT Ari in its bright state obtained by the TESS orbital observatory in 2021 and 2023 and by ground-based amateur telescopes in 2022. The light curves from 2021 and 2022 are dominated by modulations with a period slightly shorter than the orbital one (negative superhumps), 0.13292 and 0.13273 d, respectively. From the data obtained in 2023, we see much stronger modulations appearing on a much longer timescale of a few days with an amplitude of up to 0.5 mag, compared to 0.2 mag in 2021. We also find the negative superhump variability with the period of 0.1338 d in the 2023 observations, but the significance of these negative superhumps is much lower than in the previous seasons. We detect less significant additional modulations with a period exceeding the orbital one (positive superhumps) in the observations from 2021 and 2022. Their periods are 0.15106 and 0.1523 d, respectively. We also find a previously unnoticed periodic signal corresponding to the orbital period of 0.13755 d in the TESS observations in 2021. Theoretical models of tidal precession of an elliptical disk predict a decrease in the precession period (and an increase in the period of the positive superhumps) with increasing disk radius, which is consistent with the observed photometric behavior of the system. This enables us to estimate the mass ratio q of the components in TT Ari to be in the range of 0.24–0.29. The tilted disk precession model predicts a period of nodal precession whose value is in general agreement with observations.