A BeppoSAX Observation of HD9770: a Visual Triple System Containing a Recently Discovered Short-Period Eclipsing Binary

Abstract

We have studied the coronal X-ray emission of the recently discovered short-period eclipsing binary HD 9770 with the BeppoSAX satellite. The data from the Low Energy and Medium Energy Concentrator Spectrometers (LECS & MECS) onboard BeppoSAX 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 ($\sim 0.3 Z_\odot$). 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 $> 4$ keV. There is an indication that the metal abundance may be somewhat higher during the flare.