Stellar laboratories. X. New Cu IV-VII oscillator strengths and the first detection of copper and indium in hot white dwarfs

Abstract

Context. Accurate atomic data is an essential ingredient for the calculation of reliable non-local thermodynamic equilibrium (NLTE) model atmospheres that are mandatory for the spectral analysis of hot stars.
Aims: We aim to search for and identify for the first time spectral lines of copper (atomic number Z = 29) and indium (Z = 49) in hot white dwarf (WD) stars and to subsequently determine their photospheric abundances.
Methods: Oscillator strengths of Cu IV-VII were calculated to include radiative and collisional bound-bound transitions of Cu in our NLTE model-atmosphere calculations. Oscillator strengths of In IV - VI were compiled from the literature.
Results: We newly identified 1 Cu IV, 51 Cu V, 2 Cu VI, and 5 In V lines in the ultraviolet (UV) spectrum of DO-type WD RE 0503-289. We determined the photospheric abundances of 9.3 × 10^-5 (mass fraction, 132 times solar) and 3.0 × 10^-5 (56 600 times solar), respectively; we also found Cu overabundances in the DA-type WD G191-B2B (6.3 × 10^-6, 9 times solar).
Conclusions: All identified Cu IV-VI lines in the UV spectrum of RE 0503-289 were simultaneously well reproduced with our newly calculated oscillator strengths. With the detection of Cu and In in RE 0503-289, the total number of trans-iron elements (Z > 28) in this extraordinary WD reaches an unprecedented number of 18.

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 NAS5-26666.

Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer.

Tables A.13-A.16 are only available via the German Astrophysical Virtual Observatory (GAVO) service TOSS (http://dc.g-vo.org/TOSS)