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Astron. Astrophys. 330, 139-144 (1998)


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X-ray spectroscopy of the active giant [FORMULA]  Ceti: the SAX LECS view

A. Maggio 1, F. Favata 2, G. Peres 1 and S. Sciortino 1

1 Istituto e Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy
2 Astrophysics Division - Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands

Received 27 August 1997 / Accepted 12 September 1997

Abstract

We present an X-ray observation of the active giant [FORMULA]  Cet, performed with the Low Energy Concentrator Spectrometer (LECS) on-board the SAX satellite. The resulting X-ray spectrum is well fit by an optically-thin plasma model with two discrete temperatures, and the inferred coronal metallicity is compatible both with the abundances derived from a re-analysis of the ASCA SIS spectrum of the same object, adopting the same plasma emission code (MEKAL), and with accurate photospheric abundances recently reported in the literature. The remarkable similarity between the X-ray spectrum of [FORMULA]  Cet and the one of the active binary Capella, also observed by SAX, rises again the issue of how some putative He-burning clump giants, like [FORMULA]  Cet, manage to retain (or regain) a relatively high X-ray activity level. Some implications of the new Hipparcos parallaxes, relevant for the coronal properties of [FORMULA]  Cet and the Hyades giants, are also discussed.

Key words: stars: individual: fi Cet – stars: abundances – stars: activity – stars: late-type – X-rays: stars

Send offprint requests to: A. Maggio
(amaggio@oapa.astropa.unipa.it)

© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998
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