HEAD 2000, November 2000
Session 42. Stars and Stellar Coronae
Display, Friday, November 10, 2000, 8:00am-6:00pm, Bora Bora Ballroom

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[42.12] Direct Detection of Stellar Winds from Late-Type Dwarfs via Charge Transfer X-Ray Emission

B.J. Wargelin, J.J. Drake, V.L. Kashyap (CfA)

Despite the fact that the overwhelming majority of stars are of late spectral type (F-M) and lie on the main sequence, we know nothing about their stellar winds. Existing measurements of winds extend down to a few \times 10-10\ M\odot/year (vs. the solar rate of ~2 \times 10-14\ M\odot/year), and only apply to high-mass O and B stars, red giants, and supergiants. Attempts to detect winds from late-type dwarf stars have to date resulted only in loose upper limits of order 10-12 to 10-11\ M\odot/year.

Recent x-ray detections of comets have led to suggestions that charge transfer between highly-charged ions in the solar wind and neutral gases in cometary atmospheres may be responsible for the observed emission, a hypothesis that has been confirmed by Chandra observations of Comet LINEAR 1999 S4. It has also been proposed that charge transfer between the solar wind and the local ISM may produce much of the soft x-ray background observed by ROSAT and various rocket experiments. We show that the same process may be observable in nearby star systems using large-area high-resolution observatories such as Chandra, which would provide hitherto inaccessible information on wind and magnetosphere geometry, ion composition, and mass loss rates. This work is supported by Chandra X-ray Center NASA contract NAS8-39073.

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