Dynamical Evolution of Viscous Disks around Be Stars. I: photometry

TL;DR

This study models the time-dependent behavior of gaseous disks around Be stars using photometric data and radiative transfer simulations, aiming to infer physical parameters of the disks and star.

Contribution

It introduces a detailed analysis of disk density evolution and photometric variability for different dynamical scenarios around Be stars, utilizing a 3-D non-LTE radiative transfer approach.

Findings

Lightcurves vary with mass loss history, inclination, and viscosity.

Photometric variability can diagnose disk and stellar parameters.

Different scenarios produce distinct observational signatures.

Abstract

Be stars possess gaseous circumstellar disks that modify in many ways the spectrum of the central B star. Furthermore, they exhibit variability at several timescales and for a large number of observables. Putting the pieces together of this dynamical behavior is not an easy task and requires a detailed understanding of the physical processes that control the temporal evolution of the observables. There is an increasing body of evidence that suggests that Be disks are well described by standard $\alpha$-disk theory. This paper is the first of a series that aims at studying the possibility of inferring several disk and stellar parameters through the follow-up of various observables. Here we study the temporal evolution of the disk density for different dynamical scenarios, including the disk build-up as a result of a long and steady mass injection from the star, the disk dissipation that occurs after mass injection is turned off, as well as scenarios in which active periods are followed by periods of quiescence. For those scenarios, we investigate the temporal evolution of continuum photometric observables using a 3-D non-LTE radiative transfer code. We show that lightcurves for different wavelengths are specific of a mass loss history, inclination angle and $\alpha$ viscosity parameter. The diagnostic potential of those lightcurves is also discussed.