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Institut für Astronomie und Astrophysik

Abteilung Astronomie

Sand 1, D-72076 Tübingen, Germany
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Preprint 16b/04

Turning cool star X-ray spectra upside down

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

(1) Institut für Astronomie und Astrophysik. Univ. Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Harvard-Smithsonian Center for Astrophysics, MS 3, 60 Garden St., Cambridge, MA 02138, USA

To be published in: X-ray Diagnostics for Astrophysical Plasmas, American Institute of Physics Conference Proceedings

Abstract. H1504+65 is a young white dwarf with Teff=200000 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. NLTE model spectra for the 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.
Key words: stars: atmospheres - stars: coronae - X-rays: stars

Preprint (39 kb PDF file including figures)

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