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M.A. Iping-Petterson (Eleanor Roosevelt High School), R.C. Iping (CUA & NASA's GSFC), G. Sonneborn (NASA's GSFC), D. Massa (SGT Inc. & NASA's GSFC), E. M. Schlegel (Harvard-Smithsonian CfA), D. Gruber (San Diego), J. Hutchings (Herzberg Institute of Astrophysics NRC of Canada/DAO)
The high-mass eclipsing X-ray binary system SMC X-1/Sk 160 was observed for almost one complete orbit (3.892 days) with the Far Ultraviolet Spectroscopic Explorer (FUSE) on 19-23 July 2003. The X-ray pulsar with a pulse period of P=0.71 sec is eclipsed by the supergiant, a B0 Ib for ~0.6 day. Spectra covering 905-1180 Å\ with a spectral resolution of ~0.05 Å\ were obtained for a total of 148 ksec covering orbital phases from 0.20, through conjunction of the pulsar (phase 0.5), ending at phase 0.06, near the end of the X-ray source eclipse. We present an initial analysis of the significant changes in the O VI 1032-1038 absorption formed in the stellar wind of the B0 I primary as a function of orbital phase.
The O VI doublet is a coronal line that samples gas near ~3 x 105 K, assuming collisional equilibrium, but is expected to be present under photoionization conditions up to ~106 K, when the X-ray source ionizes the wind around most of the orbit as is the case in SMC X-1. O VI is especially critical since it is the highest ionization stage (O V I.P.=114 eV) of any strong resonance line longward of the Lyman limit, and consequently is the best diagnostic for studying the kinematics of the highly ionized gas in the SMC X-1 system. The O VI variations are compared with those of N V 1238-1242 Å\ and C IV 1548-1550 Å\ from archival HST and IUE spectra.
R.C. Iping acknoledges support of NASA grant NAG5-11137 to Catholic University of America.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.