Interstellar deuterium, nitrogen, and oxygen abundances toward BD+28°4211:: Results from the FUSE mission

High-resolution far-UV spectra of the O-type subdwarf BD + 28degrees4211 were obtained with the Far Ultraviolet Spectroscopic Explorer ( FUSE) to measure the interstellar deuterium, nitrogen, and oxygen abundances in this direction. The interstellar D I transitions are analyzed down to Lyiota at 920.7 Angstrom. The star was observed several times at different target offsets in the direction of spectral dispersion. The aligned and co-added spectra have high signal-to-noise ratios (S/N = 50-100). D I, N I, and O I transitions were analyzed with curve-of-growth and profile fitting techniques. A model of interstellar molecular hydrogen on the line of sight was derived from H-2 lines in the FUSE spectra and used to help analyze some features where blending with H-2 was significant. The H I column density was determined from high-resolution Hubble Space Telescope Space Telescope Imaging Spectrograph spectra of Lyalpha to be log N(H I) = 19.846 +/- 0.035 (2 sigma), which is higher than is typical for sight lines in the local interstellar medium (ISM) studied for D/H. We found that D/H = (1.39 +/- 0.21) x 10(-5) (2 sigma) and O/H = (2.37 +/- 0.55) x 10(-4) (2 sigma). O/H toward BD + 28 degrees4211 appears to be significantly below the mean O/H ratio for the ISM and the Local Bubble.