Size of the accretion disc in the recurrent nova T CrB

Abstract

We present high-resolution (0.06 Å px${\hspace{0.17em}}^{-1}$) spectroscopic observations of the recurrent nova T Coronae Borealis obtained during the last 1.5 years (September 2022–January 2024), with the 2.0-m RCC telescope of the Rozhen National Astronomical Observatory, Bulgaria. Double-peaked emission is visible in the $H_{\alpha }$ line after the end of the superactive state. We subtract the red giant contribution and measure the distance between the peaks ($\Delta v_a$) of the line. For the period July 2023–January 2024, we find that $\Delta v_a$ is in range km s${\hspace{0.17em}}^{-1}$. Assuming that the emission is from the accretion disc around the white dwarf, we find average radius of the accretion disc $R_{\text{disc}}=89\pm 19$ R${\hspace{0.17em}}_{\odot }$, which is approximately equal to the Roche lobe size of the white dwarf. Our results indicate that tidal torque plays an important role but that the disc can extend up to the Roche lobe of the accreting star.