CORONAL X-RAY-EMISSION OF HD-35850 - THE ASCA VIEW

We present the analysis of the X-rap data of the young active star HD 35850 obtained with ASCA and ROSAT. Our main goal was to see if there is a difference in the elemental abundances of active stars between yo ung and mure evolved objects, A two temperature plasma with subsolar a bundances, of the order of Z = 0.15 - 0.3, is required to fit the SIS spectra. Similar results In obtained from a ROSAT PSPC observation. Me tal abundances of 0.2 - 0.4 the solar value are required to fit both t he ASCA and ROSAT data together. From a simultaneous SIS0+SIS1 spectra l fit. with 2T plasma models and abundances free to vary in non-solar proportions, we find that. besides N, O and Ne for which we find very low values. all other elements have values relative to solar abundance s around 0.2-0.3. These subsolar abundances are in line with those typ ically observed in more evolved. active stars like RS CVn and Algol-ty pe binaries. The two temperature values required to fit the ASCA SIS s pectra are about 0.5 and 1.0 keV. These temperatures, especially the h igher one. are lower with respect to the values found for the RS CVn a nd Algol binaries or for the young star AB Dor. but higher than other single G/K stars. All our data show that this single, late F-tvpe star is actually a very active source, indirectly confirming that this fas t rotating star is probably a young object. In the simultaneous fit of the ASCA+ROSAT data, a third temperature is required. However this is not just an addition of a setter component, but is more a redistribut ion of the dominant temperatures. Indeed. the range spanned by the thr ee temperatures, from 5 to 15 million degrees, is not very large.