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Astron. Astrophys. 321, 850-858 (1997)


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Coronal X-ray emission of HD 35850: the ASCA view

G. Tagliaferri 1, S. Covino 1, T.A. Fleming 2, M. Gagné 3, R. Pallavicini 4, F. Haardt 5 and Y. Uchida 6

1 Osservatorio Astronomico di Brera, via E. Bianchi 46, I-22055 Merate (LC), Italy
2 Steward Observatory, University of Arizona, Tucson, Arizona, USA
3 JILA, University of Colorado, Boulder, CO 80309-0440, USA
4 Osservatorio Astronomico G.S. Vaiana, Palermo, Italy
5 Institute of Theoretical Physics, Chalmers University Technology, S-41296 Göteborg, Sweden
6 Science University of Tokyo, Tokyo, Japan

Received 6 September 1996 / Accepted 5 November 1996

Abstract

We present the analysis of the X-ray data of the young active star HD 35850 obtained with ASCA and ROSAT. Our main goal was to see if there is a difference in the elemental abundances of active stars between young and more evolved objects. A two temperature plasma with subsolar abundances, of the order of [FORMULA], is required to fit the SIS spectra. Similar results are obtained from a ROSAT PSPC observation. Metal abundances of 0.2 - 0.4 the solar value are required to fit both the ASCA and ROSAT data together. From a simultaneous SIS0+SIS1 spectral fit, with 2T plasma models and abundances free to vary in non-solar proportions, we find that, besides N, O and Ne for which we find very low values, all other elements have values relative to solar abundances around 0.2-0.3. These subsolar abundances are in line with those typically observed in more evolved, active stars like RS CVn and Algol-type binaries.

The two temperature values required to fit the ASCA SIS spectra are about 0.5 and 1.0 keV. These temperatures, especially the higher one, are lower with respect to the values found for the RS CVn and Algol binaries or for the young star AB Dor, but higher than other single G/K stars. All our data show that this single, late F-type star is actually a very active source, indirectly confirming that this fast rotating star is probably a young object. In the simultaneous fit of the ASCA+ROSAT data, a third temperature is required. However this is not just an addition of a softer component, but is more a redistribution of the dominant temperatures. Indeed, the range spanned by the three temperatures, from 5 to 15 million degrees, is not very large.

Key words: X-ray: stars – stars: abundances – stars: activity – stars: coronae – stars: individual: HD 35850

Send offprint requests to: G. Tagliaferri

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998

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