Stark Broadening of In II Spectral Lines

Dimitrijević, M. S.; Sahal‐Bréchot, S.

doi:10.1238/physica.regular.065a00083

Cited by 8 publications

(5 citation statements)

References 32 publications

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“…In option 2, we adopted the oscillator strengths from Kurucz & Bell (1995) and the classical line broadening parameter while neglecting pressure shifts. Kurucz & Bell (1995) agreement although the pressure shifts calculated by Dimitrijević & Sahal-Bréchot (1992) are a factor of 3 smaller than measured (Srećković & Djeniže 1993). Because the measured Ca iiλ3933 shift is relatively small (see Vennes, Kawka, & Németh 2010a) it may not be measurable in our spectra and the lack of accuracy in these parameters would not affect the abundance and radial velocity analysis.…”

Section: Si IImentioning

confidence: 76%

See 1 more Smart Citation

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: Si IImentioning

confidence: 76%

“…As part of option 1, we adopt the theoretical broadening and shift parameters of Dimitrijević & Sahal‐Bréchot (1992), and in option 2, we adopt again the compilation of Kurucz & Bell (1995) without pressure shifts.…”

Section: Analysis and 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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“…The theory also predicts that the widths of the hydrogen series in the blue and in the Johnson U -band (λ ≈ 3200 Å−4000 Å) should be much larger than the widths of the nearby resonance lines of Ca II H and K, which are not broadened due to energy level splittings with a linear (hydrogenic) dependence on the perturbing field. The impact broadening of Ca II H and K by ambient electrons have been calculated by Griem (1974), Dimitrijević & Sahal-Bréchot (1992), and Dimitrijevic & Sahal-Brechot (1993). At the highest electron densities in the condensations, the Lorentzian FWHM values 12 are only 1 − 1.5 × 10 −3 Å.…”

Section: Comparisons Of Ca II K Hα Hβ and Hγmentioning

confidence: 98%

The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope

Kowalski,

Allred,

Carlsson

et al. 2022

Preprint

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Red-shifted components of chromospheric emission lines in the hard X-ray impulsive phase of solar flares have recently been studied through their 30 s evolution with the high resolution of IRIS. Radiative-hydrodynamic flare models show that these redshifts are generally reproduced by electronbeam generated chromospheric condensations. The models produce large ambient electron densities, and the pressure broadening of hydrogen Balmer series should be readily detected in observations. To accurately interpret upcoming spectral data of flares with the DKIST, we incorporate non-ideal, non-adiabatic line broadening profiles of hydrogen into the RADYN code. These improvements allow time-dependent predictions for the extreme Balmer line wing enhancements in solar flares. We study two chromospheric condensation models, which cover a range of electron beam fluxes (1 − 5 × 10 11 erg s −1 cm −2 ) and ambient electron densities (1 − 60 × 10 13 cm −3 ) in the flare chromosphere. Both models produce broadening and redshift variations within 10 s of the onset of beam heating. In the chromospheric condensations, there is enhanced spectral broadening due to large optical depths at Hα, Hβ, and Hγ, while the much lower optical depth of the Balmer series H12−H16 provides a translucent window into the smaller electron densities in the beam-heated layers below the condensation. The wavelength ranges of typical DKIST/ViSP spectra of solar flares will be sufficient to test the predictions of extreme hydrogen wing broadening and accurately constrain large densities in chromospheric condensations.

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“…For example, we adopted log Γ = −7.562 for Ca iλ4226 and log Γ = −7.76 for Ca H&K at T = 10 000 K, and α = 0.238 for Ca iλ4226 and α = 0.223 for Ca H&K. Stark broadening widths for Ca i and Ca ii lines were obtained from Dimitrijević & Sahal-Bréchot (1999) and Dimitrijević & Sahal-Bréchot (1992), respectively. Additional parameters (Stark and collisions with hydrogen) were obtained from the compilation of Kurucz & Bell (1995).…”

Section: Heavy Element Line Profilesmentioning

confidence: 99%

VLT/X-shooter observations and the chemical composition of cool white dwarfs

Kawka

Vennes

2012

A&A

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We present a model atmosphere analysis of cool hydrogen-rich white dwarfs observed at the Very Large Telescope (VLT) with the X-shooter spectrograph. The intermediate-dispersion and high signal-to-noise ratio of the spectra allowed us to conduct a detailed analysis of hydrogen and heavy element line profiles. In particular, we tested various prescriptions for hydrogen Balmer line broadening parameters and determined the effective temperature and surface gravity of each star. The spectra of three objects (NLTT 1675, 6390, and 11393) show heavy elements (Mg, Al, Ca, or Fe). Our abundance analysis revealed a relatively high iron-to-calcium ratio in NLTT 1675 and NLTT 6390. We also present an analysis of spectropolarimetric data obtained at the VLT using the focal reducer and low dispersion spectrograph (FORS). We establish strict upper limits to the magnetic field strengths in three of the DAZ white dwarfs and determine the longitudinal magnetic field strength in the DAZ NLTT 10480. The class of DAZ white dwarfs comprises objects that are possibly accreting material from their immediate circumstellar environment and the present study helps to establish the class properties.

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Stark Broadening of In II Spectral Lines

Cited by 8 publications

References 32 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★

The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope

VLT/X-shooter observations and the chemical composition of cool white dwarfs

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