Stellar laboratories: VIII. New Zr IV - VII, Xe IV - V, and Xe VII oscillator strengths and the Al, Zr, and Xe abundances in the hot white dwarfs G191-B2B and RE0503-289
<i>Context. <i/>For the spectral analysis of high-resolution and high-signal-to-noise spectra of hot stars, state-of-the-art non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that is used for the...
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| Main Authors: | , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
16 March 2017
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| In: |
Astronomy and astrophysics
Year: 2017, Volume: 599 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201629794 |
| Online Access: | Verlag, kostenfrei, Volltext: http://dx.doi.org/10.1051/0004-6361/201629794
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| Author Notes: | T. Rauch, S. Gamrath, P. Quinet, L. Löbling, D. Hoyer, K. Werner, J.W. Kruk, and M. Demleitner |
| Summary: | <i>Context. <i/>For the spectral analysis of high-resolution and high-signal-to-noise spectra of hot stars, state-of-the-art non-local thermodynamic equilibrium (NLTE) model atmospheres are mandatory. These are strongly dependent on the reliability of the atomic data that is used for their calculation. <i>Aims. <i/>To search for zirconium and xenon lines in the ultraviolet (UV) spectra of G191−B2B and RE 0503−289, new Zr iv-vii, Xe iv-v, and Xe vii oscillator strengths were calculated. This allows, for the first time, determination of the Zr abundance in white dwarf (WD) stars and improvement of the Xe abundance determinations. <i>Methods. <i/>We calculated Zr iv-vii, Xe iv-v, and Xe vii oscillator strengths to consider radiative and collisional bound-bound transitions of Zr and Xe in our NLTE stellar-atmosphere models for the analysis of their lines exhibited in UV observations of the hot WDs G191−B2B and RE 0503−289. <i>Results. <i/>We identified one new Zr iv, 14 new Zr v, and ten new Zr vi lines in the spectrum of RE 0503−289. Zr was detected for the first time in a WD. We measured a Zr abundance of −3.5 ± 0.2 (logarithmic mass fraction, approx. 11 500 times solar). We identified five new Xe vi lines and determined a Xe abundance of −3.9 ± 0.2 (approx. 7500 times solar). We determined a preliminary photospheric Al abundance of −4.3 ± 0.2 (solar) in RE 0503−289. In the spectra of G191−B2B, no Zr line was identified. The strongest Zr iv line (1598.948 Å) in our model gave an upper limit of −5.6 ± 0.3 (approx. 100 times solar). No Xe line was identified in the UV spectrum of G191−B2B and we confirmed the previously determined upper limit of −6.8 ± 0.3 (ten times solar). <i>Conclusions. <i/>Precise measurements and calculations of atomic data are a prerequisite for advanced NLTE stellar-atmosphere modeling. Observed Zr iv-vi and Xe vi-vii line profiles in the UV spectrum of RE 0503−289 were simultaneously well reproduced with our newly calculated oscillator strengths. |
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| Item Description: | Gesehen am 24.10.2017 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201629794 |