Accretion Geometry and Variability in QS Telescopii from multi-epoch Observations

Abstract We present phase-resolved photometry, spectroscopy, photopolarimetry, and circular spectropolarimetry of the polar QS Telescopii, obtained between 2017 and 2025 using the South African Astronomical Observatory (SAAO) 1.0-m and 1.9-m telescopes, the Transiting Exoplanet Survey Satellite (TESS), Asteroid Terrestrial-impact Last Alert System (ATLAS) and the Southern African Large Telescope (SALT). From ground-based photometry, we report the first detection of quasi-periodic oscillations (QPOs) in QS Tel, with timescales ranging between 2 and 11 minutes. This makes QS Tel one of only seven polars to show QPOs. The average spectra of QS Tel show broad and strong Balmer ($\rm H\delta$, $\rm H\gamma$, $\rm H\beta$ and $\rm H\alpha$) and He ii 4686 Å emission lines, along with weaker emission from He i at (6678 Å, 5017 Å, 4921 Å, 4712 Å, 4471 Å, and 4387 Å) and the Bowen fluorescence complex C iii/N iii at 4650 Å. For the first time detailed Doppler tomography of the $\rm H\alpha$ and He ii 4686 Å lines are presented which reveal emission from the irradiated face of the secondary star, the ballistic stream, the threading region and complex magnetically confined flows. The magnetically confined accretion stream splits into two distinct components coming from the same stream. One component appears near the threading region and the other component is seen along the high velocity in the magnetically confined accretion stream closer to the White Dwarf. Broad band photopolarimetry reveals circular polarisation reaching levels of +8%, however more detailed circular spectropolarimetry shows polarisation ranging from −10% to +25%, associated with two broad, phase-dependent cyclotron humps centred at ~4800 Å and ~6300 Å, consistent with a magnetic field strength of ~53 MG.