Lyman Gamma Satellites Due to H-H+ Collisions: Application to FUSE Observations of Hot White Dwarfs

Allard, N. F.; Bourdreux, S.; Kielkopf, John F.; Hébrard, G.; Désert, Jean-Michel; Ferlet, R.; Vidal‐Madjar, A.; Hubený, I.; Peek, James M.

doi:10.1007/978-94-010-0215-8_47

Cited by 3 publications

(5 citation statements)

References 2 publications

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“…Comparison of our quantal results with the semi-classical ones (Allard et al 2003) shows a global agreement for the shape of the satellite as well as for the decrease of its intensity with increasing temperatures. Some expected discrepancies appear at low temperatures, however they decrease slowly when the temperature increases.…”

Section: Discussion and Concluding Remarkssupporting

confidence: 71%

“…The computed quantum results are compared in figure 6 with the semi-classical results of Allard et al (2003) Both results give a similar behaviour of the satellite: it appears clearly that the quantum results confirms the decreasing of absorption with increasing temperatures: this justifies the importance at low temperatures of the Boltzmann factor taken into account recently in the expression of the semi-classical approach. However, the quantum abosorption coefficient is systematically lower than the semi-classical one, the difference between them decreases slowly for increasing temperatures and is less than 20 per cent at the typical temperatures of white dwarfs.…”

Section: Comparison Of Quantal and Semi-classical Resultsmentioning

confidence: 52%

“…Some expected discrepancies appear at low temperatures, however they decrease slowly when the temperature increases. Among several possible sources of differences, the first one, namely, the one-perturber approach, assumed in the present quantum calculations is valid for the density N considered in Allard et al (2003): if we compare the potential range of the relevant electronic states ( 20 Å) to N − 1 3 , it appears that the number of perturbers in the interaction sphere is much less than 1 (this could be different for higher lines as larger distances are involved). Thus, the difference may be due to the validity limit of the use of classical rectilinear trajectories in the semi-classical calculations.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

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Quantum non-adiabatic study of the quasi-molecular satellites of the Lyman line perturbed by H

Lique¹,

Tchang-Brillet²,

Spielfiedel³

et al. 2004

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

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In the so-called one-perturber approach, free-bound and free-free transitions contribute to absorption in the wings of atomic lines perturbed by collisions. Perturbation theory for the interaction of light with a binary collisional complex is applied to the calculation of the absorption coefficient. The initial and final wavefunctions of the binary complex are quite general, taking into account non-adiabatic effects between the adiabatic electronic states. Application to the calculation of the Lyman α quasi-molecular satellite due to H-H collisions is presented. We compare the results that include rotational coupling between the upper B 1 + u and C 1 u states with the results obtained in an adiabatic approach. It is shown that no significant difference between these results is obtained so that the total absorption coefficient may be calculated by summing up the contributions of the different electronic transitions calculated in the Born-Oppenheimer approximation. As expected, discrepancies between quantal and semi-classical results appear at low temperatures, which are slowly reduced as the temperature increases.

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Section: Discussion and Concluding Remarkssupporting

confidence: 71%

Section: Comparison Of Quantal and Semi-classical Resultsmentioning

confidence: 52%

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

See 1 more Smart Citation

Quantum non-adiabatic study of the quasi-molecular satellites of the Lyman line perturbed by H

Lique¹,

Tchang-Brillet²,

Spielfiedel³

et al. 2004

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

View full text Add to dashboard Cite

show abstract

“…This might explain in part why the fits shown in previous investigations (Koester et al 1998;Wolff et al 2001;Hébrard et al 2003, for examples) appear somewhat better. Another improvement would be to include a variable dipole moment in the calculations of the satellites of Lyman-γ as suggested by Allard et al (2003). This may enhance the strength of the Lyman-γ satellites and help improve the fit shown on Fig.…”

Section: Discussion and Summarymentioning

confidence: 99%

Far Ultraviolet Spectroscopic ExplorerObservation of the Ultramassive White Dwarf PG 1658+441

Dupuis¹,

Chayer²,

Vennes³

et al. 2003

ApJ

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We present an analysis of the Far Ultraviolet Spectroscopic Explorer (FUSE) spectrum of the ultramassive (M = 1.31 M ⊙ ), magnetic (B s = 2.3 MG) white dwarf PG 1658+441. The far ultraviolet (FUV) spectrum exhibits very broad Lyman lines and quasi-molecular Lyman β satellites, but weak Lyman γ satellites may also be present. PG 1658+441 is the hottest white dwarf known to show these satellite features. We fit the Lyman lines with stellar models and obtain atmospheric parameters consistent with a published analysis of the Balmer lines. By averaging results obtained for the different FUSE segments, we determine T eff = 29, 620 ± 500 K and log g = 9.31 ± 0.07. The models match the data over large portions of the spectrum but discrepancies remain near the satellite features. Finally, no trace elements have been identified in the FUV spectrum, and we provide abundance upper limits for

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“…This feature, due to a Lyman γ satellite, is now included in our calculations. We have shown that a larger temperature is required to get it detectable (Allard et al 2002).…”

Section: Comparison With Theoretical Spectramentioning

confidence: 90%

Quasi-molecular lines in Lyman wings of cool DA white dwarfs

Hébrard

Allard

Hubený³

et al. 2002

A&A

Self Cite

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Abstract. We present new theoretical calculations of the total line profiles of Lyman α and Lyman β which include perturbations by both neutral hydrogen and protons and all possible quasi-molecular states of H 2 and H + 2 . They are used to improve theoretical modeling of synthetic spectra for cool DA white dwarfs. We compare them with FUSE observation of G 231-40. The appearance of the line wings between Lyman α and Lyman β is shown to be sensitive to the relative abundance of hydrogen ions and neutral atoms, and thereby to provide a temperature diagnostic for stellar atmospheres and laboratory plasmas.

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Lyman Gamma Satellites Due to H-H+ Collisions: Application to FUSE Observations of Hot White Dwarfs

Cited by 3 publications

References 2 publications

Quantum non-adiabatic study of the quasi-molecular satellites of the Lyman line perturbed by H

Quantum non-adiabatic study of the quasi-molecular satellites of the Lyman line perturbed by H

Far Ultraviolet Spectroscopic ExplorerObservation of the Ultramassive White Dwarf PG 1658+441

Quasi-molecular lines in Lyman wings of cool DA white dwarfs

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