The Bismuth Abundance in the HgMn Stars χ Lupi and HR 7775 and Improved Atomic Data for Selected Transitions of Bii, Biii, and Biiii

Abstract

High-resolution spectra of the chemically peculiar HgMn stars chi Lupiand HR 7775, obtained with the Hubble Space Telescope/Goddard HighResolution Spectrograph, are investigated for their abundance of bismuthby comparison with LTE synthetic spectrum modeling. HR 7775, previouslyknown from International Ultraviolet Explorer spectra to display stronglines of Bi II, is determined to have bismuth present at an enhancementlevel of nearly 5 orders of magnitude from the lines Bi IIlambdalambda1436, 1902 and Bi III lambda1423. The bismuthenhancement for chi Lupi is found to be near a level of 1.5 dex, andan ionization anomaly between Bi+ and Bi++ isapparent. HR 7775 abundance enhancements of the heavy elements platinum,[Pt/H]=4.7 dex, and gold, [Au/H]=3.8 dex, have also been determined. Newlaboratory measurements for wavelengths and hyperfine structure patternsof Bi I/Bi II/Bi III lines are presented, as well as the results ofcalculations for hyperfine structure constants and oscillator strengthsfor selected lines of Bi II and Bi III. Based on observations with theNASA/ESA Hubble Space Telescope, obtained at the Space Telescope ScienceInstitute, which is operated by the Association of Universities forResearch in Astronomy, Inc., under NASA contract NAS5-26555. (Less)