A Multi-observing-technique Study of the Dynamical Evolution of the Viscous Disk around the Be Star $\omega$ CMa

TL;DR

This study uses multi-wavelength observations and modeling to analyze the dynamical evolution of the viscous disk around the Be star ω CMa, revealing qualitative agreement but quantitative discrepancies that suggest the need for model adjustments.

Contribution

It extends previous light curve modeling by incorporating diverse observational data, highlighting the importance of viscosity and disk truncation in disk evolution.

Findings

Models qualitatively match observed disk growth and decay trends.

Quantitative discrepancies suggest the need for higher viscosity or disk truncation.

Adjustments improve the agreement between models and observations.

Abstract

The observed emission lines of Be stars originate from a circumstellar Keplerian disk that are generally well explained by the Viscous Decretion Disk model. In an earlier work we performed the modeling of the full light curve of the bright Be star $\omega$ CMa (Ghoreyshi et al. 2018) with the 1-D time-dependent hydrodynamics code SINGLEBE and the Monte Carlo radiative-transfer code HDUST. We used the V -band light curve that probes the inner disk through four disk formation and dissipation cycles. This new study compares predictions of the same set of model parameters with time-resolved photometry from the near UV through the mid-infrared, comprehensive series of optical spectra, and optical broad-band polarimetry, that overall represent a larger volume of the disk. Qualitatively, the models reproduce the trends in the observed data due to the growth and decay of the disk. However, quantitative differences exist, e.g., an overprediction of the flux increasing with wavelength, too slow decreases in Balmer emission-line strength that are too slow during disk dissipation, and the discrepancy between the range of polarimetric data and the model. We find that a larger value of the viscosity parameter alone, or a truncated disk by a companion star, reduces these discrepancies by increasing the dissipation rate in the outer regions of the disk.