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

Q. Li (1,3),
J.P. Cassinelli (2),
J. C. Brown (3),
W. L. Waldron (4),
N. A. Miller (5)

(1) Dept. of Astronomy, Beijing Normal University, Beijing 100875, China; qkli@bnu.edu.cn
(2) Dept. of Astronomy, University of Wisconsin-Madison, 53711; cassinelli@astro.wisc.edu
(3) Dept. of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, Scotland, UK; john@astro.gla.ac.uk, li@astro.gla.ac.uk
(4) Eureka Scientific, Inc., 2452 Delmer Street Suite 100, Oakland, CA 94602-3017; wwaldron@satx.rr.com
(5) Dept. of Physics and Astronomy, University of Wisconsin-Eau Claire, Eau Claire, WI, 54702; millerna@uwec.edu

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.

Reference: ApJ in press.
Status: Manuscript has been accepted

Weblink: http://arxiv.org/abs/astro-ph/0710.2633


Email: qkli@bnu.edu.cn