The Infrared Continuum Sizes of Be Star Disks

TL;DR

This study models the near-infrared emission from Be star disks using radiative transfer to estimate disk sizes and compare with observations, revealing how physical parameters influence disk appearance.

Contribution

It introduces a detailed radiative transfer model for Be star disks that matches observed infrared color excesses and interferometric sizes, advancing understanding of disk structure.

Findings

Model predictions align with observed infrared color excesses.

Disk size varies with wavelength and physical parameters.

Results are consistent with interferometric measurements.

Abstract

We present an analysis of the near-infrared continuum emission from the circumstellar gas disks of Be stars using a radiative transfer code for a parametrized version of the viscous decretion disk model. This isothermal gas model creates predicted images that we use to estimate the HWHM emission radius along the major axis of the projected disk and the spatially integrated flux excess at wavelengths of 1.7, 2.1, 4.8, 9, and 18 ?m. We discuss in detail the effect of the disk base density, inclination angle, stellar effective temperature, and other physical parameters on the derived disk sizes and color excesses. We calculate color excess estimates relative to the stellar V -band flux for a sample of 130 Be stars using photometry from 2MASS and the AKARI infrared camera all-sky survey. The color excess relations from our models make a good match of the observed color excesses of Be stars. We also present our results on the projected size of the disk as a function of wavelength for the classical Be star ? Tauri, and we show that the model predictions are consistent with interferometric observations in the H, K', and 12 \mu m bands.