Hot DA white dwarf model atmosphere calculations: including improved Ni PI cross-sections

Preval, S. P.; Barstow, M. A.; Badnell, N. R.; Hubený, I.; Holberg, J. B.

doi:10.1093/mnras/stw2800

Cited by 6 publications

(8 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At peak abundance temperature, Wu et al 's DR rate coefficients are larger than ours by a factor ∼ 3. A similar discrepancy was described in Preval et al [48], where other ions considered by Wu et al were also much larger than our own results.…”

Section: -Likesupporting

confidence: 89%

Dielectronic recombination of the open 4d-shell of tungsten: W³⁷⁺–W²⁸⁺

Preval¹,

Badnell²,

O’Mullane³

2018

J. Phys. B: At. Mol. Opt. Phys.

View full text Add to dashboard Cite

Tungsten is an important element for magnetically confined fusion plasmas but has the potential to cool, or even quench the plasma due to it being an efficient radiator. Total and level-resolved dielectronic recombination (DR) rate coefficients, for all ionization stages, are essential to model tungsten. We describe a set calculations performed using the distorted wave code autostructure for the tungsten ions W 37+ to W 28+ . We demonstrate the importance of relativistic configuration mixing in such calculations. In particular, we show that the partial DR rate coefficients calculated in level and configuration resolution can differ by as little as 5%, and up to as much as 75%. Using the new data, we calculate a revised steady-state ionization fraction for tungsten. We find that, relative to the ionization fraction calculated using the recombination rate coefficients of Putterich et al (Plasma Phys. Control. Fusion, 50, 085016), the peak temperatures of W 37+ to W 28+ ionization states are shifted to lower temperatures spanning 0.9-1.6keV. This temperature range is important for understanding the performance of large tokamaks, such as ITER, because the temperatures in the pedestal, edge, scrape-off-layer and divertor region fall in this range.

show abstract

Section: -Likesupporting

confidence: 89%

Dielectronic recombination of the open 4d-shell of tungsten: W³⁷⁺–W²⁸⁺

Preval¹,

Badnell²,

O’Mullane³

2018

J. Phys. B: At. Mol. Opt. Phys.

View full text Add to dashboard Cite

show abstract

“…Firstly, the models calculated in this work included more model atoms/ions than the B14 work, and covered a wider range of ionization states. Secondly, the Ni ions in this work used the photoionization cross sections calculated by Preval et al (2017) using autostructure (Badnell 2011), whereas the B14 models used hydrogenic photoionization cross sections. Thirdly, the model grids used in the B14 study were not calculated based on an iterative scheme.…”

Section: Discussion: Discrepancies In Wd0621-376mentioning

confidence: 99%

“…For Ni, the atomic data also originates from Kurucz (1992), and the PICS for Ni vii were calculated using an hydrogenic approximation. For Ni iv-vi we use the PICs calculated by Preval et al (2017).…”

Section: Stellar Atmosphere Modelsmentioning

confidence: 99%

A far-UV survey of three hot, metal-polluted white dwarf stars: WD0455−282, WD0621−376, and WD2211−495

Preval

Barstow

Bainbridge

et al. 2019

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Using newly obtained high-resolution data (R ∼ 1 × 10 5 ) from the Hubble Space Telescope, and archival UV data from the Far Ultraviolet Spectroscopic Explorer we have conducted a detailed UV survey of the three hot, metal-polluted white dwarfs WD0455-282, WD0621-376, and WD2211-495. Using bespoke model atmospheres we measured T eff , log g, and photospheric abundances for these stars. In conjunction with data from Gaia we measured masses, radii, and gravitational redshift velocities for our sample of objects. We compared the measured photospheric abundances with those predicted by radiative levitation theory, and found that the observed Si abundances in all three white dwarfs, and the observed Fe abundances in WD0621-376 and WD2211-495, were larger than those predicted by an order of magnitude. These findings imply not only an external origin for the metals, but also ongoing accretion, as the metals not supported by radiative levitation would sink on extremely short timescales. We measured the radial velocities of several absorption features along the line of sight to the three objects in our sample, allowing us to determine the velocities of the photospheric and interstellar components along the line of sight for each star. Interestingly, we made detections of circumstellar absorption along the line of sight to WD0455-282 with three velocity components. To our knowledge, this is the first such detection of multi-component circumstellar absorption along the line of sight to a white dwarf.

show abstract

“…The so-called EUV problem, that is, the discrepancy between model and observation in this wavelength range (cf., Hoyer et al 2017) is, however, not significantly reduced. We note that Preval et al (2017) showed recently that improved, larger photoionization cross-section of Ni can reduce this discrepancy.…”

Section: Resultsmentioning

confidence: 76%

Stellar laboratories

Rauch¹,

Gamrath

Quinet

et al. 2020

A&A

View full text Add to dashboard Cite

IX. New Se v, Sr ivvii, Te vi, and I vi oscillator strengths and the Se, Sr, Te, and I abundances in the hot white dwarfs G191−B2B and RE 0503−289 ⋆,⋆⋆,⋆⋆⋆ ABSTRACT Context. To analyze spectra of hot stars, advanced non-local thermodynamic equilibrium (NLTE) model-atmosphere techniques are mandatory. Reliable atomic data is crucial for the calculation of such model atmospheres.Aims. We aim to calculate new Sr iv-vii oscillator strengths to identify for the first time Sr spectral lines in hot white dwarf (WD) stars and to determine the photospheric Sr abundances. To measure the abundances of Se, Te, and I in hot WDs, we aim to compute new Se v, Te vi, and I vi oscillator strengths. Methods. To consider radiative and collisional bound-bound transitions of Se v, Sr ivvii, Te vi, and I vi in our NLTE atmosphere models, we calculated oscillator strengths for these ions.Results. We newly identified four Se v, 23 Sr v, 1 Te vi, and three I vi lines in the ultraviolet (UV) spectrum of RE 0503−289. We measured a photospheric Sr abundance of 6.5 +3.8 −2.4 × 10 −4 (mass fraction, 9 500 -23 800 times solar). We determined the abundances of Se (1.6 +0.9 −0.6 × 10 −3 , 8 000 -20 000), Te (2.5 +1.5 −0.9 × 10 −4 , 11 000 -28 000), and I (1.4 +0.8 −0.5 × 10 −5 , 2 700 -6 700). No Se, Sr, Te, and I line was found in the UV spectra of G191−B2B and we could determine only upper abundance limits of approximately 100 times solar. Conclusions. All identified Se v, Sr v, Te vi, and I vi lines in the UV spectrum of RE 0503−289 were simultaneously well reproduced with our newly calculated oscillator strengths.

show abstract

Hot DA white dwarf model atmosphere calculations: including improved Ni PI cross-sections

Cited by 6 publications

References 18 publications

Dielectronic recombination of the open 4d-shell of tungsten: W³⁷⁺–W²⁸⁺

Dielectronic recombination of the open 4d-shell of tungsten: W³⁷⁺–W²⁸⁺

A far-UV survey of three hot, metal-polluted white dwarf stars: WD0455−282, WD0621−376, and WD2211−495

Stellar laboratories

Contact Info

Product

Resources

About

Hot DA white dwarf model atmosphere calculations: including improved Ni PI cross-sections

Cited by 6 publications

References 18 publications

Dielectronic recombination of the open 4d-shell of tungsten: W37+–W28+

Dielectronic recombination of the open 4d-shell of tungsten: W37+–W28+

A far-UV survey of three hot, metal-polluted white dwarf stars: WD0455−282, WD0621−376, and WD2211−495

Stellar laboratories

Contact Info

Product

Resources

About

Dielectronic recombination of the open 4d-shell of tungsten: W³⁷⁺–W²⁸⁺

Dielectronic recombination of the open 4d-shell of tungsten: W³⁷⁺–W²⁸⁺