EDP Sciences
Free access
Volume 399, Number 1, February III 2003
Page(s) 279 - 285
Section Formation and evolution of planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20021764

A&A 399, 279-285 (2003)
DOI: 10.1051/0004-6361:20021764

Beppo SAX observations of CF Tucanae and TY Pyxidis

E. Franciosini1, R. Pallavicini1 and G. Tagliaferri2

1  INAF/Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
2  INAF/Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (LC), Italy

(Received 24 September 2002 / Accepted 14 November 2002)

We present the results of BeppoSAX observations of the RS CVn binary systems CF Tuc and TY Pyx. A long-duration flare was detected on CF Tuc just at the beginning of the observation; a second smaller flare occurred about half a period later. The light curve of TY Pyx shows a significant orbital modulation of the quiescent emission with possible evidence for eclipses, and strong flares. We find that the coronae of the two stars are very similar: both systems have quiescent temperatures of $\sim $10 and 20-25 MK, with only a factor of two difference in the emission measures. During the flares, temperatures of $\sim $30-40 MK are reached; these temperatures are not high enough to give detectable hard X-ray emission in the PDS. Both stars have subsolar coronal metallicities: we confirm the very low coronal abundance of CF Tuc ( $Z\sim 0.1{-}0.2 \, Z_{\odot}$), while for TY Pyx we find $Z\sim 0.5{-}0.6 \, Z_{\odot}$. For both stars the coronal metallicities are in good agreement with their measured photospheric abundances.

Key words: stars: binaries: close -- stars: activity -- stars: coronae -- stars: individual: CF Tuc -- stars: individual: TY Pyx -- X-rays: stars

Offprint request: E. Franciosini, francio@astropa.unipa.it

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