Extended analysis of four-times ionized barium: (Ba V)

Sharma, Manoj K.; Rahimullah, K; Tauheed, A.

doi:10.1016/j.jqsrt.2013.08.014

Cited by 3 publications

(2 citation statements)

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“…To our knowledge, the only available data were recently published by Sharma et al (2014) and Sharma et al (2013) for Ba v and Ba vii, respectively. More precisely, these authors reported oscillator strengths and transition probabilities computed using rather limited configuration interaction models based on the Hartree-Fock approach due to Cowan (1981) combined with a semi-empirical least-squares fit of radial energy parameters.…”

Section: Introductionmentioning

confidence: 99%

“…More precisely, these authors reported oscillator strengths and transition probabilities computed using rather limited configuration interaction models based on the Hartree-Fock approach due to Cowan (1981) combined with a semi-empirical least-squares fit of radial energy parameters. In order to get a uniform set of oscillator strengths for all the transitions of Ba ions observed in the present work, we decided to perform new calculations including a larger amount of electron correlation and hence improving the previous investigations of Sharma et al (2013Sharma et al ( , 2014. The method adopted here was the relativistic Hartree-Fock (HFR) approach with core-polarization corrections (see e.g., Quinet et al 1999Quinet et al , 2002 2 5p6s6p, 5s5p 3 4f, 5s5p 3 5f, 5s5p 3 6f, and 5s5p 3 6p for the even parity.…”

Section: Introductionmentioning

confidence: 99%

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Stellar laboratories

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Context. For the spectral analysis of high-resolution and high-signal-to-noise (S/N) 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.Aims. Reliable Ba v-vii oscillator strengths are used to identify Ba lines in the spectra of the DA-type white dwarf G191−B2B and the DO-type white dwarf RE 0503−289 and to determine their photospheric Ba abundances.Methods. We newly calculated Ba v-vii oscillator strengths to consider their radiative and collisional bound-bound transitions in detail in our NLTE stellar-atmosphere models for the analysis of Ba lines exhibited in high-resolution and high-S/N UV observations of G191−B2B and RE 0503−289.Results. For the first time, we identified highly ionized Ba in the spectra of hot white dwarfs. We detected Ba vi and Ba vii lines in the Far Ultraviolet Spectroscopic Explorer (FUSE) spectrum of RE 0503−289. The Ba vi/Ba vii ionization equilibrium is well reproduced with the previously determined effective temperature of 70 000 K and surface gravity of log g = 7.5. The Ba abundance is 3.5 ± 0.5 × 10 −4 (mass fraction, about 23 000 times the solar value). In the FUSE spectrum of G191−B2B, we identified the strongest Ba vii line (at 993.41 Å) only, and determined a Ba abundance of 4.0 ± 0.5 × 10−6 (about 265 times solar). Conclusions. Reliable measurements and calculations of atomic data are a pre-requisite for stellar-atmosphere modeling. Observed Ba vi-vii line profiles in two white dwarfs' (G191−B2B and RE 0503−289) far-ultraviolet spectra were well reproduced with our newly calculated oscillator strengths. This allowed to determine the photospheric Ba abundance of these two stars precisely.

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Section: Introductionmentioning

confidence: 99%