Statistical Analysis of Interferometric Measurements of Axis Ratios for Classical Be Stars

TL;DR

This paper introduces a Bayesian statistical method to estimate the opening angles of classical Be star disks from interferometric measurements, revealing that most disks are thin and consistent with viscous disk models.

Contribution

It presents a novel Bayesian approach combined with Monte Carlo simulations to infer disk opening angles from interferometric data, advancing understanding of Be star disk geometries.

Findings

Disks in the K-, H-, and N-bands are predominantly thin with angles 0.15° to 4.0°.

Hα line measurements suggest slightly thicker, flaring disks with angles 3.7° to 14°.

Results support viscous disk models predicting flaring structures.

Abstract

This work presents a novel method to estimate the effective opening angle of CBe star disks from projected axis ratio measurements, obtained by interferometry using Bayesian statistics. A Monte Carlo scheme was used to generate a large set of theoretical axis ratios from disk models using different distributions of disk densities and opening angles. These theoretical samples were then compared to observational samples, using a two-sample Kolmogorov-Smirnov test, to determine which theoretical distribution best reproduces the observations. The results suggest that the observed ratio distributions in the K-, H-, and N-band can best be explained by the presence of thin disks, with opening half-angles of the order of 0.15$^{\circ}$ to 4.0$^{\circ}$. Results for measurements over the H$\alpha$ line point toward slightly thicker disks, 3.7$^{\circ}$ to 14$^{\circ}$, which is consistent with a flaring disk predicted by the viscous disk model.