Deuterium Abundance toward WD 0621-376: Results from the FUSE Mission
Sembach, K. R.; Moos, H. W.; Chayer, P.; Hébrard, G.; Lehner, N.; Gry, C.; Désert, J. -M.; Howk, J. C.
United States, France, Canada
Abstract
Far Ultraviolet Spectroscopic Explorer observations are presented for WD 0621-376, a DA white dwarf star in the local interstellar medium (LISM) at a distance of about 78 pc. The data have a signal-to-noise ratio of ~20-40 per 20 km s-1 resolution element and cover the wavelength range 905-1187 Å. LISM absorption is detected in the lines of D I, C II, C II*, C III, N I, N II, N III, O I, Ar I, and Fe II. This sight line is partially ionized, with an ionized nitrogen fraction of greater than 0.23. We determine the ratio D/O=(3.9+1.3-1.0)×10-2 (2 σ). Assuming a standard interstellar oxygen abundance, we derive D/H~1.3×10-5. Using the value of N(H I) derived from Extreme Ultraviolet Explorer data gives a similar D/H ratio. The D I/N I ratio is (3.3+1.0-0.8)×10-1 (2 σ).