AAS 201st Meeting, January, 2003
Session 33. Stars Dead or Alive
Oral, Monday, January 6, 2003, 2:00-3:30pm, 606-607

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[33.07] Chandra and XMM-Newton X-Ray Spectroscopy of the Hot Corona of YY Mensae

M. Audard (Columbia University), M. Güdel (Paul Scherrer Institut), S.L. Skinner (CASA/University of Colorado), R. Pallavicini (Palermo Observatory), S.A. Drake (NASA/GSFC), R. Mewe (SRON-Utrecht)

We present Chandra and XMM-Newton X-ray spectra of the rapidly rotating K giant YY Mensae (d = 290 pc). YY Men is a member of a loosely-defined class of rapidly rotating single cool giant stars (``FK Com stars''), whose outstanding property is a projected equatorial velocity measured up to 110 km/s, in contrast with the expected maximum of 6 km/s for giants. One of the leading theories to explain the extreme properties of FK Com stars suggests that they were formed by coalescence of a contact binary when one of the components entered into the giant stage. Previous observations have shown that its corona displays plasma with a very hot temperature of about 3 keV, with probably no or very little plasma at temperatures below 1 keV. The new X-ray observatories now provide excellent high-resolution X-ray spectra to study the coronal properties of this extreme coronal source. The X-ray spectrum is dominated by a strong continuum and by bright emission lines, mostly from H-like transitions and Fe XXIV lines. Thanks to its wavelength range and its sensitivity, the Reflection Grating Spectrometer onboard XMM-Newton provides important information on the presence of cool coronal plasma, mostly seen at wavelengths between 20 and 40~Å. Simultaneous EPIC CCD spectra also constrain the high-temperature component of the emission measure distribution. The Chandra High-Energy Transmission Grating Spectrometer data are ideal to study at very high resolution the short wavelength range of this hot coronal source. We derive the coronal emission measure distribution, elemental abundances, and density estimates.

We acknowledge support by SAO grant GO2-3016X.

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.