X-ray emission from magnetic massive stars
Sep 5, 201431 pages
Published in:
- Astrophys.J.Suppl. 215 (2014) 1, 10
- Published: Oct 30, 2014
e-Print:
- 1409.1690 [astro-ph.SR]
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Abstract: (IOP)
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- B stars and flattens for the more luminous, higher- 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.Note:
- 31p, 11 figures, 8 tables - including online material and erratum, accepted for publication by ApJ
- X-rays: stars
- Stars: magnetic field
- Stars: early-type
References(69)
Figures(15)