Institut für Astronomie und Astrophysik Abteilung Astronomie Sand 1, D-72076 Tübingen, Germany
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Preprint 12/04

Turning cool star X-ray spectra upside down

K. Werner (1), J.J. Drake (2)

(1) Institute for Astronomy and Astrophysics, University of Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Harvard-Smithsonian Center for Astrophysics, MS 3, 60 Garden Street, Cambridge, MA 02138, USA

To be published in: Proc. 13th Cool Stars Workshop, eds. F. Favata et al., ESA-SP

Abstract. H1504+65 is a young white dwarf with an effective temperature of 200,000 K and is the hottest post-AGB star ever analysed with detailed model atmospheres. Chandra LETG+HRC-S spectra have revealed the richest X-ray absorption line spectrum recorded from a stellar photosphere to date. The line forming regions in this extremely hot photosphere produce many transitions in absorption that are also observed in emission in cool star coronae. We have performed a detailed comparison of Chandra spectra of H1504+65 with those of Procyon and alpha Cen A and B. State of the art non-LTE model spectra for the hot white dwarf have enabled us to identify a wealth of absorption lines from highly ionised O, Ne and Mg. In turn, these features have allowed us to identify coronal lines whose origins were hitherto unknown.
 

Preprint (201 kb PDF file including figures)
Astrophysics (astro-ph): astro-ph/0410701

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