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Session 78 - Stars - Young and Old, Large and Small.
Display session, Wednesday, January 15
We report on moderate (\lambda/\Delta\lambda = 20,000) and high (\lambda/\Delta\lambda = 90,000) resolution spectra of the 104 day period Capella binary system (HD 34029). These spectra were obtained with the HST Goddard High Resolution Spectrometer on 1995 September 9 and 1996 April 9. The observations include a long duration moderate resolution spectrum of the coronal Fe XXI 1354 Å\ line and one moderate resolution and one high resolution echelle spectrum of the He II 1640 Å\ line. Our data set also includes lines of C II, O III, N IV, and O V.
Our objective in observing the Fe XXI line, which is formed at T=10^7 K, was to infer the contribution of each star's corona. This is feasible because the GHRS can easily resolve the 50 km s^-1 radial velocity separation of the stars. Present day X-ray instruments and even the upcoming XMM and AXAF spectrometers cannot resolve the emission from each star. We will report on the relative contribution of each star and the Doppler shift and line width for each star. With these data we can estimate the X-ray luminosities of the G1 III and G8 III stars individually.
We observed the He II 1640 Å\ line twice with a time separation of 7 months corresponding to almost exactly 2 orbital periods. The profiles are nearly identical, except for a large difference in flux at the expected velocty of the G8 III star. We will discuss the relative emission from each star and the roles of collisional excitation and photoionization/recombination in producing the 1640 Å\ emission from each star.
This work is supported by grant GO-05886.01.94A to the University of Colorado.
Program listing for Wednesday