X-ray Emission from Magnetically Torqued Disks of Oe/Be Stars

TL;DR

This paper investigates X-ray emissions from magnetically torqued disks in Oe/Be stars to test the magnetic channeling model, comparing predictions with observations from ROSAT and Chandra to understand disk formation mechanisms.

Contribution

It applies the Magnetically Torqued Disk model to predict X-ray emissions in Be stars and compares these predictions with observational data to evaluate the model's validity.

Findings

Model predictions align with ROSAT observations for some Be stars.

Magnetic field strength and stellar rotation significantly influence X-ray emission levels.

Chandra observations of $$ Oph provide detailed line profiles supporting the model.

Abstract

We focus attention on the Oe/Be stars to test the concept that the disks of these stars form by magnetic channeling of wind material toward the equator. Calculations are made of the X-rays expected from the Magnetically Torqued Disk (MTD) model for Be stars discussed by Cassinelli et al. (2002), by Maheswaran (2003), and by Brown et al. (2004). The dominant parameters in the model are the $\beta$ value of the velocity law, the rotation rate of the star, $S_o$, and the ratio of the magnetic field energy density to the disk gravitational energy density, $\gamma$. The model predictions are compared with the $ROSAT$ observations obtained for an O9.5 star $\zeta$ Oph from \Berghofer et al. (1996) and for 7 Be stars from Cohen et al. (1997). Extra considerations are also given here to the well studied Oe star $\zeta$ Oph for which we have $Chandra$ observations of the X-ray line profiles of the triad of He-like lines from the ion Mg XI.