Abundance and Isotopic Composition of Platinum in χ Lupi and HR 7775 Derived with the Help of New Laboratory Spectra of Pt II
Johansson, Sveneric; Wahlgren, Glenn M.; Leckrone, David S.; Kalus, Gabriele; Thorne, Anne P.; Brandt, Jack C.
Sweden, United States, United Kingdom
Abstract
The platinum isotope anomaly observed in the chemically peculiar HgMn star χ Lupi has been confirmed by analysis with new high-resolution laboratory spectra recorded with the VUV Fourier transform spectrometer at Lund University. The χ Lupi platinum composition is shown to be a mixture of isotopes 196 and 198. Recent observations made with the Hubble Space Telescope Goddard High-Resolution Spectrograph (HST/GHRS) of a similar temperature HgMn star, HR 7775, have also been analyzed; these show that line profiles of Pt II are best fitted by the terrestrial isotopic mixture. Fits of synthetic spectra to the observations yield a logarithmic abundance of platinum of log NPt = +6.05 for χ Lupi and log NPt = +6.50 for HR 7775, on a scale of log NH = +12.00.
Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.