Connections Between Tilted Accretion Disks Around White Dwarfs and Substellar Companions

TL;DR

This study investigates whether brown dwarf donors in white dwarf systems can induce and sustain tilted accretion disks, finding that their low mass transfer rates are insufficient for observable disk tilts, explaining their observational scarcity.

Contribution

The paper assesses the potential of brown dwarf donors to cause disk tilt in white dwarf systems, providing quantitative thresholds and applying them to a specific model system.

Findings

Brown dwarf donors lack enough mass to induce disk tilt.

Minimum mass transfer rate for tilt is approximately 10^{-10} M_sun/yr.

SDSS 1035's transfer rate is too low for observable tilt.

Abstract

Accretion disks in white dwarf systems are believed to be tilted. In a recent publication, the lift force has been suggested to be a source to disk tilt, a source that is likely relevant to all accretion disk systems. Lift is generated by slightly different supersonic gas stream speeds flowing over and under the disk at the bright spot. In this conference proceeding, we focus on whether a brown dwarf donor star accreting onto a white dwarf primary has enough mass to contribute to disk tilt. We also would like to obtain whether a white dwarf - brown dwarf close binary system has enough mass to induce and maintain a disk tilt of four degrees. We adopt SDSS 103533.03+055158.4 as our model system which has a mass transfer rate of ((10\pm2) \times 10^{-12}) M$_{\odot}$ yr$^{-1}$. We find that the brown dwarf in SDSS 1035 does not have enough mass to contribute to disk tilt. We find a gross magnitude of the minimum mass transfer rate to be $\sim10^{-10}$M$_{\odot}$yr$^{-1}$. We conclude that SDSS 1035 does not seem to have a high enough mass transfer rate to induce and maintain an observable disk tilt. Hence one reason why brown dwarf donor systems may be so difficult to find could be due to their low mass transfer rates which do not induce observable dynamical effects that is typical in white dwarf-red dwarf CVs.