D ec 2 00 2 Interstellar Deuterium , Nitrogen , and Oxygen Abundances Toward GD 246 , WD 2331 − 475 , HZ 21 , and Lan 23 : Results from the FUSE Mission 1

The interstellar abundances of D I, N I, and O I in the local ISM are studied using high-resolution spectra of four hot white dwarfs. The spectra of GD 246, WD 2331−475, HZ 21, and Lan 23 were obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE ) in the wavelength range 905 – 1187 Å. The line of sight to GD 246 probes the Local Interstellar Cloud and at least one other H I cloud inside the Local Bubble, which contains most of the gas seen along this line of sight. The column densities of H I, C II*, S II, and Si II are measured using archival Hubble Space Telescope STIS echelle-mode observations. The H I column density is determined by fitting the strong damping wings of interstellar Lyα using a model atmosphere to account for the stellar continuum. The sightline-averaged ratios for GD 246 are: D I/H I = (1.51 ± 0.39 0.33) × 10 , O I/H I = (3.63 ± 0.77 0.67)× 10 , and D I/O I = (4.17 ± 1.20 1.00)× 10 −2 (uncertainties are 2σ). This line of sight provides the fourth reliable FUSE measurement of the Local Bubble D/H ratio. For the WD 2331−475 line of sight we find sightlineaveraged ratios: D I/O I = (5.13 ± 2.20 1.69)×10 −2 and D I/N I = (4.57 ± 1.88 1.45)×10 . Toward HZ 21 the sightline-averaged ratios are: D I/O I = (4.57 ± 2.22 1.63) × 10 −2 and D I/N I = (4.27 ± 1.96 1.44) × 10 . In the higher column density sightline to Lan 23 the sightline-averaged ratios are: D I/O I = (3.24 ± 3.27 2.06) × 10 −2 and Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by The Johns Hopkins University under NASA contract NAS5-32985. Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218 Institut d ́Astrophysique de Paris, 98 boulevard Arago, F-75014 Paris, France Current Address: Center for Astrophysics and Space Sciences, University of California at San Diego, C-0424, La Jolla, CA, 92093 Primary affiliation: Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, BC V8W 3P6, Canada