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[53.03] Phase-Dependent Changes in O VI and Other Stellar Wind Lines in SMC X-1

G. Sonneborn (NASA's GSFC), R. C. Iping (CUA & NASA's GSFC), D. L. Massa (SGT Inc., & NASA's GSFC), D. Gruber (UCSD), E. M. Schlegel (CfA), J. B. Hutchings (HIA-NRC)

The accretion-powered high-mass X-ray binary SMC X-1/Sk 160 was observed for one complete orbit (3.89 days) with the Far Ultraviolet Spectroscopic Explorer (FUSE) to study how the strong X-ray source modulates the stellar wind of the B0 I primary. The observations were obtained primarily on 2003 July 19-23, with additional observations on 2003 Oct 27 and 2004 Aug 23 filling some phase gaps and duplicating others. Interstellar lines of molecular hydrogen and O VI 1032 from foreground Milky Way and SMC gas were modelled and used to correct the observed stellar O VI 1032 P-Cygni line profiles. The O VI absorption shows that the wind is highly asymmetry around the orbit. The line is at maximum strength during the eclipse of the pulsar (phase 0.0), with a total column density of N(O VI) = 7E17 cm^-2. The O VI line virtually disappears near phase 0.4. The terminal velocity (700 km/s) drops to near zero at phase 0.3-0.4. These results are qualitatively consistent with 3D-hydrodynamic models of the disrupted stellar wind of SMC X-1 (Blondin and Woo 1995, ApJ, 445, 889). Archival HST/STIS spectra of SMC X-1 obtained in 2000 and 2001 show that the N V 1238-42 and C IV 1548-50 stellar wind features have phase dependences similar to that seen in O VI. The line profile variations do not appear to be correlated with X-ray high or low states of the 60-day super-orbital period. Other stellar wind lines in the FUSE spectrum of SMC X-1 (S IV 1073, P V 1117, Si IV 1122, C III 1176) show much smaller orbital modulation effects than are seen in O VI. These lines are present at approximately the same strength at all phases.

This work was supported in part by NASA grant NNG04GK79G to Catholic University of America for FUSE GI program D175.

The author(s) of this abstract have provided an email address for comments about the abstract: george.sonneborn-1@nasa.gov

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.