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Session 77 - Binary Stars.
Display session, Wednesday, January 15
Metropolitan Ballroom,
Mass transfer during the evolution of intermediate-mass stars in a close binary system can result in a rejuvenated and spun-up secondary star which can appear as a rapidly rotating Be star. Models suggest that many bright Be stars may be binaries with unseen, stripped-down, helium star companions (the progenitors of Be/X-ray binaries). Here we describe the first unambiguous detection of the UV spectrum of such a hot remnant for the case of the Be-binary system, Phi Per (P = 127 d), based on high S/N observations made with the Goddard High Resolution Spectrograph aboard Hubble Space Telescope. We present the individual spectra of the Be star primary and hot subdwarf secondary (reconstructed using a Doppler tomography algorithm) in the 1374 and 1647 Angstrom regions, and we derive estimates of the binary mass ratio, UV flux ratio, and projected rotational velocities. We discuss the temperature, gravity, and chemical abundances of the companion, and the evolutionary state of the binary system.
Support for this work was provided by NASA through grant numbers GO-6046 and GO-6714 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
