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J. Dupuis (CSA), C.M. Oliveira (JHU), G. Hebrard (IAP), H.W. Moos, P. Sonnentrucker (JHU)
Deuterium is a relic of the big bang nucleosynthesis and its primeval abundance is extremely sensitive to physical conditions encountered in the early Universe. Measuring the present-epoch abundance of deuterium is critical to better understand how it was affected by chemical evolution of the Galaxy. FUSE measurements of deuterium abundance over several lines of sight have shown how uniform the D/H ratio is within the Local Bubble but also shown that substantial variability is observed over larger distances. To further explore this question we determine the D/H, N/H, D/O, and O/H ratios along the line of sight to the hot DA star REJ1738+665 (l = 96.89 deg, b = 31.95 deg) using FUSE and HST/STIS spectra. With a distance of 243 pc and log N(H) = 19.83 +/- 0.05 (1 sigma) this sightline probes mostly gas located outside of the Local Bubble (LB).
We derive D/H = (1.78 + 0.28 -0.25)E-5, N/H = (5.89 + 1.02 - 0.91)E-5, O/H = (3.24 + 0.56 -0.50)E-4, and D/O = (5.50 + 0.85 - 0.77)E-2. The D/H and O/H ratios are consistent, at the 1 sigma level, with values determined for the LB by other authors. However, D/O determined here is more than 2 sigma away from the LB value and is one of the highest D/O ratios in the literature.
We discuss the ratios derived for this sightline and put them in the context of other ratios in the literature.
This work is based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. Financial support to U.S. participants has been provided through NASA contract NAS5-32985. JD also acknowledges funding from LTSA grant NAG5-11844.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.