BeppoSAX observations of CF Tucanae and TY Pyxidis

Abstract

We present the results of BeppoSAX observations of the RS CVn binary systems CF Tuc and TY Pyx. A long- durationflare was detected on CF Tucjust at the beginning of the observation; a second smaller flareoccurred 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 ∼10 and 20-25 MK, with only a factor of two difference in the emission measures. During the flares, temperatures of ∼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 ∼ 0.1−0.2Z� ), while for TY Pyx we find Z ∼ 0.5−0.6Z� . For both stars the coronal metallicities are in good agreement with their measured photospheric abundances.