Absolute vacuum ultraviolet oscillator strengths in Co II and the interstellar cobalt abundance

We report the first laboratory measurements of 10 absolute oscillator strengths (f-values) for vacuum ultraviolet lines of Co 11. The oscillator strengths are measured with the High-Sensitivity Absorption Spectroscopy Experiment at the University of Wisconsin. The measurements serve as a test of theoretical work on Co II f-values and set an absolute scale for relative oscillator strengths from spectra taken with the Hubble Space Telescope. Observations of interstellar absorption in the direction of p Oph A result in the determination of the f-value for an additional line. The set of absolute f-values is used to derive the interstellar abundance of cobalt toward p Oph A and Oph. Cobalt is found to be less severely depleted onto grains than earlier analyses based on available theoretical /-values suggested. As a consequence of this revision, the correspondence between depletion and condensation temperature is somewhat weakened.