SPH simulations of structures in protoplanetary disks

TL;DR

This study uses SPH simulations to model how embedded low-mass companions affect protoplanetary disk structures, revealing periodic column density variations that can explain brightness cycles in young stars.

Contribution

The paper introduces a modified GADGET-2 code to simulate disk perturbations by low-mass companions, analyzing their impact on circumstellar extinction and brightness variations.

Findings

Periodic column density variations occur in disks.

Variations depend on system parameters and orientation.

Results can explain brightness cycles in UX Ori stars.

Abstract

The hydrodynamic models of the protoplanetary disk, which perturbed by the embeded low-mass companion, were calculated by our modification of GADGET-2 code. The cases of circular and eccentric orbits which can be coplanar or slightly inclined to the disk midplane were considered. The column density of test particles on the line of sight between the central star and observer was computed during the simulations. Then the column density of the circumstellar dust was calculated under the assumption that the dust and gas are well mixed with a mass ratio 1 : 100. To research the influence of the disk orientation relative to the observer on the circumstellar extinction the calculations were made for four angles of inclination of the line of sight to the disk midplane and eight directions along the azimuth. The column density in the circumstellar and circumbinary disk were computed separately. The calculations have shown the periodic variations of column density can arise both in the circumstellar and circumbinary disks. The amplitude and shape of the variation strongly depend on the parameters of the simulated system (eccentricity and inclination of the orbit, the mass ratio of the companion and star) and its orientation in space. The results of our simulations can be used to explain the cyclic variation of the brightness of young UX Ori type stars.