Astron. Astrophys. 343, 297-302 (1999)

New Zr II oscillator strengths and the zirconium conflict in the HgMn star Lupi

C.M. Sikström ¹, H. Lundberg ², G.M. Wahlgren ^1,3, Z.S. Li ², C. Lyngå ², S. Johansson ¹ and D.S. Leckrone <sup>4

1</sup> Atomic Spectroscopy, Department of Physics, University of Lund, Sölvegatan 14, S-223 62 Lund, Sweden (e-mail: carl_martin.sikstrom@fysik.lu.se)
² Atomic Physics, Lund Institute of Technology, Professorsgatan 1, S-223 62 Lund, Sweden
³ Comp. Sciences Corp., Code 681, GSFC, Greenbelt, MD 20771, USA
⁴ Laboratory for Astronomy and Solar Physics, NASA/GSFC, Code 681, Greenbelt, MD 20771, USA

Received 16 September 1998 / Accepted 17 November 1998

Abstract

Lifetimes on the sub-nanosecond scale for the levels v², v² and v² in the 4d5s5p configuration in Zr II have been measured, using the method of laser-induced fluorescence. Combined with branching fractions obtained with the Lund Ultraviolet (UV) Fourier Transform Spectrometer (FTS), experimental oscillator strengths have been derived. From Hubble Space Telescope /Goddard High-Resolution Spectrograph spectra, the zirconium abundance in the HgMn star Lupi has been determined from Zr II and Zr III lines. More than an order of magnitude difference in the Zr II abundance has been derived from these ionization stages. The difference is much too large to be explained by uncertainties in the oscillator strengths. Possible explanations of this difference have to be found in the stellar models, such as the influence of non-LTE or diffusion.

Key words: atomic data line: identification methods: laboratory stars: abundances stars: individual: O Lupi ultraviolet: stars

Send offprint requests to: C.M. Sikström

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Contents

• 1. Introduction
• 2. Branching fractions
• 3. Radiative lifetimes
• 4. Oscillator strengths
• 5. Astrophysical applications
• 6. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999
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