Superhumps in the cataclysmic variable BG Triangulum

Abstract

We present a detailed photometric study of the bright cataclysmic variable BG Tri using ground-based observations mainly from Rozhen Observatory, ASAS-SN, TESS, and WASP sky surveys. We report the discovery of a negative superhump with P−sh = 0.1515(2) days and a co-existing superorbital variation with P = 3.94(53) days in data from 2019 and 2020. A positive superhump with P+sh = 0.1727(14) days 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 (QPOs) and stochastic variability (flickering) in BG Tri. The light curves show a rich mixture of simultaneously overlapping quasi-periods ranging from 5 to 25 minutes. The multi-colour (UBVRI) photometric observations from 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.