On Stark line shifts in spectra of very hot stars

Kršljanin, V.; Dimitrijević, M. S.

doi:10.1007/3-540-55256-1_339

Cited by 4 publications

(4 citation statements)

References 5 publications

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“…On the other hand, we show that introducing Stark shifts in line profile modelling helped reduce the scatter in line velocity measurements to well within the expected accuracy of the echelle spectra. Investigations of the effect of pressure shifts on radial velocity measurements are relatively rare but their effect have been predicted (e.g., Hammond 1989;Kršljanin & Dimitrijević 1992). A lack of radial velocity variations between two epochs that are 123 days apart also rules out a close binary scenario for the origin of the accreted material.…”

Section: Discussionmentioning

confidence: 99%

Pressure shifts and abundance gradients in the atmosphere of the DAZ white dwarf GALEX J193156.8+011745★

Vennes¹,

Kawka²,

Németh³

2011

Monthly Notices of the Royal Astronomical Society

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We present a detailed model atmosphere analysis of high‐dispersion and high signal‐to‐noise ratio spectra of the heavily polluted DAZ white dwarf GALEX J1931+0117. The spectra obtained with the Very Large Telescope (VLT)‐Kueyen/UV‐Visual Echelle Spectrograph show several well‐resolved Si ii spectral lines enabling a study of pressure effects on line profiles. We observed large Stark shifts in silicon lines in agreement with theoretical predictions and laboratory measurements. Taking into account Stark shifts in the calculation of synthetic spectra, we reduced the scatter in individual line radial velocity measurements from ∼3 to ≲1 km s−1. We present revised abundances of O, Mg, Si, Ca and Fe based on a critical review of line‐broadening parameters and oscillator strengths. The new measurements are generally in agreement with our previous analysis with the exception of magnesium with a revised abundance of a factor of 2 lower than previously estimated. The magnesium, silicon and iron abundances exceed solar abundances, but the oxygen and calcium abundances are below solar. Also, we compared the observed line profiles to synthetic spectra computed with variable accretion rates and vertical abundance distributions assuming diffusive steady state. The inferred accretion rates vary from for calcium to 2 × 109 g s−1 for oxygen. We find that the accretion flow must be oxygen rich while being deficient in calcium relative to solar abundances. The lack of radial velocity variations between two measurement epochs suggests that GALEX J1931+0117 is probably not in a close binary and that the source of the accreted material resides in a debris disc.

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Section: Discussionmentioning

confidence: 99%

Pressure shifts and abundance gradients in the atmosphere of the DAZ white dwarf GALEX J193156.8+011745★

Vennes¹,

Kawka²,

Németh³

2011

Monthly Notices of the Royal Astronomical Society

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“…For the evaluation and modelling of the stellar atmospheric physical properties and abundance determinations, astrophysicists require Stark broadening data for a large number of transitions in many atoms. Knowledge of Stark shifts can make possible accurate determination of the gravitational red shifts in spectra of white dwarfs [17][18][19]. granular motion [15,16].…”

Section: Introductionmentioning

confidence: 99%

Modified semiempirical Stark shifts of ArII lines

Kršljanin

Dimitrijević

1989

Z Phys D - Atoms, Molecules and Clusters

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“…The effect of pressure shifts are apparent in several strong silicon lines. This effect predicted by Hammond (1989) and Kršljanin & Dimitrijević (1992) also impacts radial velocity measurements. A lack of radial velocity variations between two epochs that are 123 days apart rules out a close binary scenario for the origin of the accreted material.…”

Section: Discussionmentioning

confidence: 82%

Accretion and Diffusion in the DAZ White Dwarf GALEX J1931+0117

Vennes¹,

Kawka²,

Németh³

et al. 2011

AIP Conference Proceedings

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Abstract.We present an analysis of high-dispersion and high signal-to-noise ratio spectra of the DAZ white dwarf GALEX J1931+0117. The spectra obtained with the VLT-Kueyen/UV-Visual Echelle Spectrograph show several well-resolved Si II spectral lines enabling a study of pressure effects on line profiles. We observed large Stark shifts in silicon lines in agreement with laboratory measurements. A model atmosphere analysis shows that the magnesium, silicon and iron abundances exceed solar abundances, while the oxygen and calcium abundances are below solar. Also, we compared the observed line profiles to synthetic spectra computed with variable accretion rates and vertical abundance distributions assuming diffusion steady-state. The inferred accretion rates vary fromṀ = 2 × 10 6 for calcium to 2 × 10 9 g s −1 for oxygen and indicate that the accretion flow is dominated by oxygen, silicon and iron while being deficient in carbon, magnesium and calcium. The lack of radial velocity variations between two measurement epochs suggests that GALEX J1931+0117 is probably not in a close binary and that the source of the accreted material resides in a debris disc.

show abstract

On Stark line shifts in spectra of very hot stars

Cited by 4 publications

References 5 publications

Pressure shifts and abundance gradients in the atmosphere of the DAZ white dwarf GALEX J193156.8+011745★

Pressure shifts and abundance gradients in the atmosphere of the DAZ white dwarf GALEX J193156.8+011745★

Modified semiempirical Stark shifts of ArII lines

Accretion and Diffusion in the DAZ White Dwarf GALEX J1931+0117

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