THE EXTREME-ULTRAVIOLET CORONAL SPECTRUM OF THE SOLAR-TYPE STAR CHI-1ORIONIS

We present an extreme ultraviolet coronal spectrum of the solar-type s tar chi(1) Ori (G0 V), one of the first spectra obtained as a guest ob servation using the Extreme Ultraviolet Explorer (EUVE). This star is younger and more active than the Sun. Since no large-scale hare activi ty was evident in the simultaneous deep-survey EUV photometry, we simu lated the spectrum using a solar active region differential emission m easure (DEM) together with the plasma emissivity code of Mewe, Gronens child, & van den Oord (1985). The spectral simulation was normalized t o the soft X-ray flux (0.1-2.4 keV) observed during the ROSAT all-sky survey and also the EUVE all-sky survey Lexan/B filter count rate to g enerate predicted counts in spectral bins in order to identify lines a nd line blends in the observed spectrum. The difference between these two normalizations was found to be less than 20%. We also compare both the observed and simulated spectra to the Capella observations of Dup ree et al. (1993). The accuracy of the emission code and of this spect ral simulation is demonstrated by its excellent fit to the high signal -to-noise ratio data in the short-wavelength spectrum of Capella. For chi(1) Ori we conclude the following: (1) apart from the He II lines, we do not see many of the expected lines forming at log T less than or equal to 6.2; (2) in the range log T = 6.3-6.8 we find reasonable agr eement with a spectrum simulating the DEM of a solar active region; an d (3) material appears to be present at temperature as hot as log T = 7.2 (Fe XXIV).