Asymmetric Illumination of a Circumbinary Disk in the Presence of a Low-Mass Companion

TL;DR

This study models how a low-mass companion influences the illumination asymmetry of a protoplanetary disk, revealing large-scale azimuthal brightness variations that can help detect such companions.

Contribution

It introduces hydrodynamic simulations showing how a low-mass companion causes asymmetric illumination patterns in a protoplanetary disk, aiding in companion detection.

Findings

Azimuthal illumination strongly depends on the orbital phase.

Bright and dark regions are asymmetric and oscillate with the orbital motion.

Asymmetries are more pronounced in the central disk regions.

Abstract

The model of an young star with a protoplanetary disk and a low-mass companion, which is moving on a circular orbit, inclined to the disk plane, is considered. The hydrodynamic models of such a system were calculated by SPH method. It was shown the distortions in the disk, caused by the orbital motion of the companion, lead to the strong dependence of illumination conditions of the disk on the azimuth (because of extinction between the star and the disk surface) and, therefore, it leads to the appearance of large-scale asymmetry in images of disks. The calculations showed the dependence of the illumination on the azimuth was stronger in the central part of the disk than on the periphery. Bright and dark domains are located not symmetry with respect to the line of nodes. The sizes and locations of the domains are depended on the model parameters as well as on the phase of the orbital period. The bright and dark domains do not follow the companion, but they make small amplitude oscillations with respect to some direction. The properties of the model, which were written above, open new opportunities of searching low-mass companions in the vicinity of young stars. The stars with protoplanetary disks, which are observed face-on or under the small inclination angle i, are the best ones for this purpose.