[Previous] | [Session 97] | [Next]
W.P. Blair, S.D. Friedman (JHU/CAS), K.R. Sembach (STScI), G. Hebrard, R. Ferlet (IAP/CNRS)
We report observations of a nearby bright cataclysmic variable star, IX Velorum, obtained with the Far Ultraviolet Spectroscopic Explorer satellite (FUSE). IX Velorum is a nova-like CV, and hence is observed normally in the high flux state. Because the UV light comes from the rapidly rotating inner accretion disk, any `photospheric' lines are smeared out, providing a smoothly undulating continuum against which to measure interstellar medium absorption lines. We see a number of lines from D~I, O~I, and other ISM species in this sight line.
At a distance of about 95 pc, this sight line samples primarily the local ISM, which has been measured with a number of FUSE spectra to nearby white dwarf stars as well. However, the sight line to IX Vel is only 2.12\circ away from the well-studied sight line to \gamma2 Velorum (cf. Fitzpatrick & Spitzer 1994, ApJ, 427, 232; Sonneborn et al. 2000, ApJ, 545, 277), which is at a distance of about 250 pc. Hence, assuming transverse variations are small in the local ISM on the sampled scales, we can deconvolve the \gamma2 Vel sight line into local (<100 pc) and more distant (100 -- 250 pc) components.
Comparison with archival HST/STIS E140M data for IX Vel shows the local sight line to be dominated by two components out of the seven identified in the \gamma2 Vel sight line by Fitzpatrick & Spitzer. Since the D/H value derived for the entire \gamma2 Vel sight line is on the high side for relatively local gas (2.18+0.36-0.31 \times 10-5), we can investigate whether this value is appropriate for the local ISM components or only for the more distant part of the sight line. If the local gas has similar composition to other local ISM sight lines, the more distant part may have an even higher D/H value than that measured by Sonneborn et al. (2000).
This work is supported by NASA Contract NAS5-32985 to the Johns Hopkins University.
The author(s) of this abstract have provided an email address for comments about the abstract: wpb@pha.jhu.edu