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Astron. Astrophys. 345, 514-520 (1999)


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A BeppoSAX observation of HD 9770: a visual triple system containing a recently discovered short-period eclipsing binary

G. Tagliaferri 1, S. Covino 1, G. Cutispoto 2 and R. Pallavicini 3

1 Brera Astronomical Observatory, Via Bianchi 46, I-22055 Merate, Italy
2 Catania Astrophysical Observatory, V.le A. Doria 6, I-95125 Catania, Italy
3 Palermo Astronomical Observatory, P.za del Parlamento 1, I-90134 Palermo, Italy

Received 25 August 1998 / Accepted 15 February 1999

Abstract

We have studied the coronal X-ray emission of the recently discovered short-period eclipsing binary HD 9770 with the Beppo SAX satellite. The data from the Low Energy and Medium Energy Concentrator Spectrometers (LECS & MECS) onboard Beppo SAX allow studying the spectrum of this star from 0.1 to 8 keV, confirming that this is a very active coronal source, with strong flaring activity. The X-ray emission most likely originates from the eclipsing binary itself, rather than from the other visual component of the system. The X-ray light curves could be modulated with the orbital period of the eclipsing binary, with a hint for a different orbital modulation of the cooler and hotter plasma. The X-ray spectrum is characterized by hot plasma, with the Fe K complex at 6.7 keV clearly detected in the MECS spectrum, and it is well fitted by a 2-temperature optically thin plasma model with low metal abundances ([FORMULA]). These results are in line with those found for many other active stars. As expected, during the flare the X-ray emission is dominated by hotter plasma with a temperature [FORMULA] keV. There is an indication that the metal abundance may be somewhat higher during the flare.

Key words: stars: activity – stars: binaries: eclipsing – stars: coronae – stars: flare – stars: individual: HD 9770 – X-rays: stars

Send offprint requests to: G. Tagliaferri

© European Southern Observatory (ESO) 1999

Online publication: April 19, 1999

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