massive stars; magnetic fields; stars; rotation; x-rays
Abstract :
[en] Recent spectropolarimetric surveys of bright, hot stars have found that ~10% of OB-type stars contain strong (mostly dipolar) surface magnetic fields (~kG). The prominent paradigm describing the interaction between the stellar winds and the surface magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the stellar wind plasma is forced to move along the closed field loops of the magnetic field, colliding at the magnetic equator, and creating a shock. As the shocked material cools radiatively it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and characterizing the hot wind material confined by the magnetic fields of these stars. Some 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 due to rapid rotation is predicted to cause faster wind outflows along the field lines, leading 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 from a theoretical point of view, we use the X-ray Analytical Dynamical Magnetosphere (XADM) model, originally developed for slow rotators, with an implementation of new rapid rotational physics. 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 the added centrifugal force plays in the magnetospheric X-ray emission of these stars.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Fletcher, C. L.; Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL, 32904, USA,
Petit, V.; Department of Physics and Astronomy, Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
Nazé, Yaël ; Université de Liège - ULiège > Groupe d'astrophysique des hautes énergies (GAPHE)
Wade, G. A.; Department of Physics, Royal Military College of Canada, PO Box 17000 Station Forces, Kingston, ON, Canada K7K 0C6
Townsend, R. H.; Department of Astronomy, University of Wisconsin-Madison, 5534 Sterling Hall, 475 N Charter Street, Madison, WI 53706, USA
Owocki, S. P.; Department of Physics and Astronomy, Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
Cohen, D. H.; Department of Physics and Astronomy, Swarthmore College, 500 College Ave., Swarthmore, PA 19081, USA
David-Uraz, A.; Department of Physics and Astronomy, Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
Shultz, M.; Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala 75120, Sweden)
Language :
English
Title :
Investigating the Magnetospheres of Rapidly Rotating B-type Stars
Publication date :
01 November 2017
Event name :
IAU Symposium 329, The Lives and Death-Throes of Massive Stars
