Laboratory and Stellar Spectra in High Resolution: Studies of Fe, Pt and Tl in Peculiar Stars

The near-infrared spectrum of upsilon Sagittarii has been registered using the SOFIN high resolution spectrometer on the Nordic Optic Telescope, La Palma. For the first time 4f-5g transitions of Fe II in any astrophysical spectrum have been identified. Optical region spectra with the high resolution SOFIN spectrograph have been analysed for determination of elemental abundances and spectral line identification in the chemically peculiar HgMn star HR7775 as a complementary study to the analysis of HST/GHRS spectra. High resolution laboratory spectra of platinum and thallium recorded with the VUV-Fourier transform spectrometer at Lund University have been used to confirm the platinum and thallium isotope anomalies in the chemically peculiar HgMn star chi Lupi. Accurate wavelengths of the Pb II resonance lines have been determined with high resolution spectra recorded with the VUV-Fouriere transform spectrometer at Imperial College in London

Hyperfine structure and isotope shift in Tl II with astrophysical applications

Fourier transform (FT) spectra of Tl II with resolved hyperfine structure (hfs) have been analyzed in the region 1790-3400 Angstrom. Measured isotope shifts (IS) for two transitions, including the S-1-P-3 intercombination line to the ground state at 1908.6 Angstrom are reported. Accurate Ritz wavelengths for isotope and hyperfine components of the S-1-P-1 resonance line at 1321.6 Angstrom are given. The accuracy is better than 0.3 m Angstrom for measured wavelengths and better than 0.4 m Angstrom for the Ritz wavelengths. Theoretical multi-configuration Dirac-Fock (MCDF) calculations, including core polarization, show that the LS-allowed 1321.6 Angstrom transition is a factor of 30 stronger than the intercombination line at 1908.6 Angstrom. The application of the new Tl II data to astrophysical spectra obtained with the Hubble Space Telescope is discussed

Revised and Extended Analysis of the Ag II Spectrum and Term System

The Ag II spectrum emitted from hollow cathode discharges has been recorded in the region 940–8500 Šwith Fourier transform and high dispersion photographic instruments. 311 lines have been classified and measured at high accuracy (±0.03–0.003 cm-1 above 2000 Ŭ ±0.002–0.0005 Šin the VUV region). Improved energy level values have been derived from the lines, and 24 new odd levels have been found. The level structure has been interpreted by ab initio and parametric calculations

Abundance and isotopic anomalies of thallium in the atmosphere of the HgMn star chi Lupi

We announce the detection of two fully resolved hyperfine components of the intercombination line of Tl II (Z = 81) at 1908.6 Angstrom in the ultraviolet spectrum of the sharp-lined, nonmagnetic, chemically peculiar star chi Lupi (BB.5pHgMn + A2 Vm). The wavelengths and profiles of these absorption lines strongly suggest that they arise from the heaviest isotope, Tl-205. The echelle observations were obtained with the Hubble Space Telescope Goddard High Resolution Spectrograph (HST/GHRS). Spectrum synthesis fits to the line profiles yield a logarithmic overabundance of thallium, relative to the solar system abundance, of +3.8 dex. We believe this to be the first detection of thallium in a star other than the Sun. It is also the first time hyperfine structure has been resolved in the satellite ultraviolet spectrum of an astrophysical source. The large overabundance and the presence of only the heaviest isotope of the element continue the pattern observed previously in chi Lup for platinum (Z = 78), gold (Z = 79), and mercury (Z = 80)