The Deuterium, Oxygen, and Nitrogen Abundance toward LSE 44

We present measurements of the column densities of interstellar D I, O I, N I, and H2 made with the Far Ultraviolet Spectroscopic Explorer (FUSE) and of H I made with the International Ultraviolet Explorer (IUE) toward the sdO star LSE 44 [(l, b) = (313.°37, + 13.°49); d = 554 ± 66 pc; z = +129 ± 15 pc]. This target is among the seven most distant Galactic sight lines for which these abundance ratios have been measured. The H I column density was estimated by fitting the damping wings of interstellar Lyα. The column densities of the remaining species were determined with profile fitting analyses and supplemented with curve-of-growth analyses for O I and H2. We find log N(D ) = 15.87 ± 0.08, log N(O ) = 17.57, log N(N ) = 16.43 ± 0.14, and log N(H ) = 20.52 (all errors 2 σ). This implies that D/H = (2.24) × 10-5, D/O = (1.99) × 10-2, D/N = (2.75) × 10-1, and O/H = (1.13) × 10-3. Of the most distant Galactic sight lines for which the deuterium abundance has been measured, LSE 44 is one of the few with D/H higher than the Local Bubble value, but D/O toward all these targets is below the Local Bubble value and more uniform than the D/H distribution.