X-RAY EMISSION FROM MAGNETIC MASSIVE STARS
- GAPHE, Département AGO, Université de Liège, Allée du 6 Août 17, Bat. B5C, B-4000 Liège (Belgium)
- Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 32901 (United States)
- Department of Physics and Astronomy, University of Delaware, Bartol Research Institute, Newark, DE 19716 (United States)
- Department of Physics and Astronomy, Swarthmore College, Swarthmore, PA 19081 (United States)
- Penn State Worthington Scranton, Dunmore, PA 18512 (United States)
Magnetically confined winds of early-type stars are expected to be sources of bright and hard X-rays. To clarify the systematics of the observed X-ray properties, we have analyzed a large series of Chandra and XMM-Newton observations, corresponding to all available exposures of known massive magnetic stars (over 100 exposures covering ∼60% of stars compiled in the catalog of Petit et al.). We show that the X-ray luminosity is strongly correlated with the stellar wind mass-loss rate, with a power-law form that is slightly steeper than linear for the majority of the less luminous, lower- M-dot B stars and flattens for the more luminous, higher- M-dot O stars. As the winds are radiatively driven, these scalings can be equivalently written as relations with the bolometric luminosity. The observed X-ray luminosities, and their trend with mass-loss rates, are well reproduced by new MHD models, although a few overluminous stars (mostly rapidly rotating objects) exist. No relation is found between other X-ray properties (plasma temperature, absorption) and stellar or magnetic parameters, contrary to expectations (e.g., higher temperature for stronger mass-loss rate). This suggests that the main driver for the plasma properties is different from the main determinant of the X-ray luminosity. Finally, variations of the X-ray hardnesses and luminosities, in phase with the stellar rotation period, are detected for some objects and they suggest that some temperature stratification exists in massive stars' magnetospheres.
- OSTI ID:
- 22340139
- Journal Information:
- Astrophysical Journal, Supplement Series, Vol. 215, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0067-0049
- Country of Publication:
- United States
- Language:
- English
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