Brightness Oscillations in Models of Young Binary Systems with Low-Mass Secondary Components

TL;DR

This study models brightness oscillations in young binary star systems with low-mass companions, revealing how orbital inclination, orientation, and accretion influence observed light curves, aiding understanding of UX Ori star variability.

Contribution

The paper introduces hydrodynamic simulations of young binary systems to explain complex brightness variations, considering orbital parameters and accretion effects.

Findings

Brightness oscillations depend on orbital inclination and orientation.

Light curve shapes are influenced by accretion rates.

Model results help interpret cyclic activity of UX Ori stars.

Abstract

We consider a model for the cyclic brightness variations of a young star with a low-mass companion that accretes matter from the remnants of a protostellar cloud. At small inclinations of the binary orbit to the line of sight, the streams of matter and the density waves excited in the circumbinary disk can screen the primary component of the binary from the observer. To study these phenomena, we have computed grids of hydrodynamic models for binary systems by the SPH method based on which we have constructed the phase light curves as a function of the rotation angle of the apsidal line relative to the observer. The model parameters were varied within the following ranges: the component mass ratio q = 0.01-0.1 and the eccentricity e = 0-0.5. We adopted optical grain characteristics typical of circumstellar dust. Our computations have shown that the brightness oscillations with orbital phase can have a complex structure. The amplitudes and shapes of the light curves depend strongly on the inclination of the binary orbit and its orientation relative to the observer and on the accretion rate. The results of our computations are used to analyze the cyclic activity of UX Ori stars.