ORFEUS-SPAS II observations of Algol-type interacting binaries

The first results from ORFEUS-SPAS II observations of five Algol-type binary systems obtained during the shuttle mission STS-80 in 1996 November/December are reported. Single spectra covering 900-1220 Angstrom of AU Mon, Z Vul, U CrB, and TX UMa were acquired with the Berkeley spectrograph. TT Hya was observed at three phases (0.19, 0.63, and 0.95) to study mass flow and to investigate asymmetry in the circumstellar material in the system. O VI was not detected in any of the binaries, which allows us to place an upper limit on T,,, in the high-temperature plasma seen in Algol-type binaries. Circumstellar material, presumably associated with the accretion disk, was detected in Fe III (UV1) in AU Mon. We estimate a particle density in the range 10(8)-10(9) cm(-3) for the region of the disk sampled during the observations. Evidence for mass infall was found in the phase 0.95 spectrum of TT Hya. From the additional (redshifted) absorption in N II (1085 Angstrom) and N I (1135 Angstrom), we find evidence for superionization in this plasma and estimate a lower limit of 10( )(-12)M. yr(-1) for the current infall rate.