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Astron. Astrophys. 363, 815-820 (2000)

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Analysis of the hyperfine and isotopic structure of Ga II in the optical spectrum of [FORMULA] Cnc and HR 7775

K. Nielsen, H. Karlsson and G.M. Wahlgren

Atomic Spectroscopy Group, Department of Physics, University of Lund Box 118, 221 00 Lund, Sweden (krister.nielsen@fysik.lu.se)

Received 11 April 2000 / Accepted 3 July 2000

Abstract

Spectra of the HgMn stars [FORMULA] Cnc and HR 7775 have been analyzed, under the assumption of local thermodynamic equilibrium (LTE), with respect to the abundance and isotopic mixture of gallium. The primary purpose of the investigation was to level the contradictory results obtained using spectral lines in different spectral regions (Smith, 1996). The analysis has been performed by GaII lines in the optical region including hyperfine and isotopic components from new Fourier Transform Spectrometer measurements (Karlsson & Litzen, 2000). Gallium has, for both stars, been determined to be overabundant by two orders of magnitude compared to the sun, using oscillator strengths derived by Ryabchikova & Smirnov (1994). The difference in abundance obtained using spectral lines in the UV and the visual spectral region is unexplainable by accounting for hyperfine and isotopic structure. Astrophysical log gf values have been determined for the GaII 5p - 5d transitions at 5360, 5363 and 5421 Å.

Key words: atomic processes – line: profiles – stars: abundances – stars: chemically peculiar – stars: individual:  Cnc, HR 7775

Send offprint requests to: K. Nielsen

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© European Southern Observatory (ESO) 2000

Online publication: December 11, 2000
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