XXIX WS2017
Applications of

Radiative Transfer

to stellar and planetary atmospheres
Tenerife, Spain - 13-17 Nov. 2017

Poster abstract details

X-rays from Magnetic B-type Stars
Corinne Fletcher, Veronique Petit, David Cohen, Gregg Wade, Rich Townsend, Stan Owocki, Alexandre David-Uraz

Abstract

Recent surveys have found that $\sim 10$\% of OB-type stars contain strong, mostly dipolar magnetic fields with strength on the order of a kilogauss. The prominent idea describing the interaction between the stellar winds and the magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the ionized wind material is forced to move along the closed magnetic field loops and collides at the magnetic equator creating a shock ($\Delta v \sim 500-800$km/s). As the shocked material cools radiatively it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting the wind material confined by the magnetic fields of these stars. Some of these magnetic B-type stars are found to have very short rotational periods. The effects of the rapid rotation on the X-ray production within the magnetosphere have yet to be explored in detail. The added centrifugal force is predicted to cause faster wind outflows along the field lines, which could lead to higher shock temperatures and harder X-rays. However, this is not observed in all rapidly rotating magnetic B-type stars. In order to address this question from a theoretical point of view, we use the X-ray Analytical Dynamical Magnetosphere (XADM) model, developed for slow rotators and implement the physics of rapid rotation. Using X-ray spectroscopy from ESA’s XMM-Newton space telescope, we observed 5 rapidly rotating B-types stars to add to the previous list of observations. Comparing the observed X-ray luminosity and hardness ratio to that predicted by the XADM allows us to determine the role an added centrifugal acceleration plays in the magnetospheres of these stars.