2022MNRAS.516.2775S

We present a detailed photometric study of the bright cataclysmic variable, BG Triangulum (BG Tri), using ground-based observations mainly from the Rozhen Observatory, the All-Sky Automated Survey for Supernovae (ASAS-SN), the Transiting Exoplanet Survey Satellite (TESS) and the Wide Angle Search for Planets (WASP). We report on the discovery of a negative superhump with P_–sh = 0.1515(2) d and a co-existing superorbital variation with P = 3.94(53) d in data from 2019 and 2020. A positive superhump with P_+sh = 0.1727(14) d is also discovered in data from 2006. The obtained negative superhump deficit ε_– = 0.044(1) and the positive superhump excess ε₊ = 0.090(9) give us an independent photometric evaluation of the mass ratio (q) of the system, which we find to be q_– = 0.37(2) and q₊ = 0.40(5), respectively. We also present a study of the quasi-periodic oscillations and stochastic variability (flickering) in BG Tri. The light curves show a rich mixture of simultaneously overlapping quasi-periods ranging from 5 to 25 min. The multicolour (UBVRI) photometric observations from the Rozhen Observatory reveal the typical increase of the flickering amplitudes to the shorter wavelengths. The recently introduced A₆₀ amplitude of the flickering light source in all studied photometric bands is systematically lower when the negative superhump is gone in season 2021.