Size of the accretion disc in the recurrent nova T CrB

TL;DR

This study measures the size of the accretion disc in the recurrent nova T CrB using high-resolution spectroscopy, revealing it extends close to the Roche lobe, influenced by tidal forces.

Contribution

The paper provides the first direct measurement of the accretion disc size in T CrB, showing it reaches near the Roche lobe, highlighting the role of tidal torque.

Findings

Accretion disc radius is approximately 89 ± 19 solar radii.

Double-peaked H-alpha emission observed after superactive state.

Disc size suggests tidal forces significantly influence disc extent.

Abstract

We present high resolution (0.06 A/px) spectroscopic observations of the recurrent nova T Coronae Borealis obtained during the last 1.5 years (September 2022 -- January 2024), with the 2.0m RCC telecope 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 $90 < \Delta v_a < 120$ km/s. Assuming that the emission is from the accretion disc around the white dwarf, we find average radius of the accretion disc $R_{disc} = 89 \pm 19$ R$_\odot$, 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.