D/H-ratio: Observations with ORFEUS II
Werner, K.; Grewing, M.; Appenzeller, I.; Krautter, J.; Mandel, H.; Widmann, H.; Kappelmann, N.; Gringel, W.; Barnstedt, J.; Haas, C.; Hopfensitz, W.; Gölz, M.; Fromm, A.; Krämer, G.; Lindenberger, A.
Germany, France
Abstract
During the second flight of the ORFEUS-SPAS satellite (Nov./Dec. 96) high resolution (λ/{Deltalambda} = 10,000) Echelle-spectra of BD +28^\circ 4211 in the wavelength regime 912 - 1400 Angstroms have been taken. Deuterium can be clearly identified in the ORFEUS-II Echelle-spectra of this star. For the first time it was possible to take spectra of faint, not redshifted objects in the far ultraviolet with a sufficient spectral resolution to study the deuterium column density in the whole spectral range of the Lyman-series down to the Lyman-limit. We obtained a value of log(N_D) = 14.7 (+/- 0.3) towards BD +28^\circ 4211. The hydrogen column density has been determined using ORFEUS Echelle- and IUE-spectra of {Ly-alpha} (log(N_H) = 19.8 (+/- 0.2)). Thus a value of 8 x 10^-6 can be obtained for the D/H-ratio on the line-of-sight towards BD +28^\circ 4211.