On the influence of component orbital motion on the photometric variability of DF Tau

TL;DR

This study analyzes 125 years of light curve data of young binary DF Tau, linking brightness changes to accretion rate variations and orbital motion, revealing discrepancies with theoretical models and localizing polarized light sources.

Contribution

It provides improved orbital parameters for DF Tau and investigates the relationship between brightness variability and orbital motion, challenging existing theoretical predictions.

Findings

Brightness variations linked to accretion rate changes.

Orbital parameters of DF Tau are substantially improved.

Discrepancies between observed variability and theoretical models.

Abstract

Based on the analysis of the long-term light curve of the young binary DF Tau spanning approximately 125 years, we infer that its brightness variations are associated with changes in the accretion rate from the circumstellar protoplanetary disk onto the primary. We have also substantially improved the orbital parameters of DF Tau, which enables us to align its secular light curve with the evolution of the binary's component separation. The relationship between the long-term brightness variations and the orbital motion of DF Tau, if present, appears to be inconsistent with theoretical predictions. Notably, similar discrepancies between theory and observations are also seen in other young binary systems. Furthermore, the source of the polarized radiation in the optical range is found to be located at a distance of $\lesssim 0.5^{\prime\prime}$ from the star, with the polarization variability showing no dependence on the orbital phase.