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E.B. Jenkins, T.M. Tripp, P.R. Wozniak (Princeton Obs.), U.J. Sofia (Villanova), G. Sonneborn (NASA-Goddard)
The Interstellar Medium Absorption Profile Spectrograph (IMAPS) recorded the L\delta and L\epsilon D and H absorption features in the spectrum of \delta Ori A during the ORFEUS-SPAS II mission in late 1996. The resolution of 4 {\rm km~s}-1 provides a substantial improvement over previous spectra recorded by the Copernicus satellite. Our 90% confidence interval for the deuterium column density toward \delta Ori A is 0.96 < N({\rm D~I}) < 1.45\times 1015{\rm cm}-2. To derive the ratio of atomic D to H, we evaluated the damped L\alpha profile recorded in many high-dispersion spectra of \delta Ori A in the IUE archive and used the dispersion of the results to help us estimate the probable systematic errors. From this exercise, we conclude that N({\rm H I})=1.54 ±0.08 \times 1020{\rm cm}-2. Combining the D and H results gives {\rm D/H}=7.5+1.9-1.4\times 10-6, a finding that is lower than 1.5\times 10-5 reported for lines of sight to cool stars within the local region and also IMAPS results for \gamma2 Vel and \zeta Pup reported by Sonneborn, et al (another abstract in this session). Our conclusion that D/H could vary in the interstellar medium in the local region of our Galaxy is consistent with independent findings by Vidal-Madjar, et al. (1998: Astr. Ap. 338, 694) for the line of sight to G191-B2B.
The author(s) of this abstract have provided an email address for comments about the abstract: ebj@astro.princeton.edu