Atomic Data for the Re II UV 1 Multiplet and the Rhenium Abundance in the HgMn-type Star χ Lupi

Abstract

We report new laboratory spectroscopic analyses that have been conducted to acquire wavelength and oscillator strength data for lines of the Re II UV 1 multiplet. Wavelengths were determined to a sub-milliangstrom accuracy for the hyperfine and isotopic structure components from laboratory spectra obtained with the Lund VUV Fourier Transform Spectrometer. An absolute atomic transition probability is reported for Re II 2275.253 Å, obtained from its upper level lifetime and an experimentally determined branching fraction. The radiative lifetime of the z⁷P^o₂ level was found to be 4.47 +/- 0.22 ns by the method of laser-induced fluorescence. With the new atomic data, synthetic spectra were generated to fit a Hubble Space Telescope Goddard High Resolution Spectrograph echelle mode spectrum of the chemically peculiar HgMn-type star χ Lupi. The weakness of the λ2275.253 Å feature only allowed for the determination of an upper limit to the rhenium abundance, which was found to be consistent with the meteoritic value. Thus, in χ Lupi, rhenium appears to be several orders of magnitude less abundant than the apparent surficial abundances of the slightly heavier elements Pt, Au, Hg, and Tl.

Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.