The polar IL Leo in a low accretion state

Abstract

We performed an optical study of the magnetic period-bouncer candidate IL Leo. Long-term photometric analysis over $\approx 20$ years reveals multiple state transitions. Modelling the ultraviolet and optical spectral energy distribution refined the white dwarf parameters, yielding a mass of $M_\textrm{wd} = 0.74 \pm 0.05 M_{\odot}$ and an effective temperature of $T_\mathrm{eff} = 12700 \pm 360$ K. We analyzed phase-resolved spectroscopy obtained with the 6-m BTA telescope and the VLT during the low state. Orbital variability of the H$\alpha$ emission, inferred from dynamical spectra and Doppler tomograms, suggests that it originates in the accretion stream. Zeeman splitting gives a mean magnetic field of $B = 40.7 \pm 0.5$ MG. Modelling two sets of cyclotron spectra determined a low-state accretion rate of $\dot{M} = (2.5 - 4.1) \times 10^{-13}~M_{\odot}$ yr$^{-1}$ and a magnetic field of $B_\mathrm{m} \approx 41$ MG near magnetic pole.