Observations of interstellar hydrogen and deuterium toward Alpha Centauri A.

Abstract

The authors present a composite profile of the Lyα emission line of α Cen A, obtained from 10 individual spectra with the high-resolution spectrograph aboard the satellite. There is excellent overall agreement with two previous Copernicus observations. Interstellar deuterium is detected, and a lower limit is set on the deuterium to hydrogen ratio of n_DI/n_HI > 8×10^-6. In addition, the deuterium bulk velocity appears blueshifted by 8 ± 2 km s^-1 with respect to interstellar hydrogen, suggesting a nonuniform medium along the line of sight.