The polar IL Leo in a low accretion state

TL;DR

This study investigates the magnetic white dwarf IL Leo in a low accretion state through long-term photometry, spectral modeling, and spectroscopy, revealing its magnetic field, accretion rate, and system parameters.

Contribution

It provides detailed measurements of IL Leo's magnetic field, accretion rate, and white dwarf parameters during a low state, enhancing understanding of magnetic accretion in polars.

Findings

White dwarf mass of 0.74 solar masses

Magnetic field of approximately 41 MG

Low accretion rate of (2.5-4.1) x 10^{-13} solar masses per year

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.