In Memoriam: James O. Hornkohl

Parigger, Christian G.; Nemes, L.

doi:10.15226/2576-4934/1/2/00105

Cited by 1 publication

(1 citation statement)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, measurements of the relative line shapes of hydrogen Balmer lines formed at high electron densities can be used to discriminate between theoretical line-profile models. However, few laboratory experiments push into high n e ( 10 17 cm −3 ) for the investigation of H line shapes (e.g., Morris & Krey 1968;Parigger et al 2003Parigger et al , 2008Djurović et al 2005Djurović et al , 2009, and none of these measure multiple lines in the same plasma. Simultaneous measurements of multiple lines is highly desirable because it alleviates potential systematic uncertainties and promotes measurement accuracy.…”

Section: Introductionmentioning

confidence: 99%

LABORATORY MEASUREMENTS OF WHITE DWARF PHOTOSPHERIC SPECTRAL LINES: Hβ

Falcon

Rochau

Bailey

et al. 2015

ApJ

View full text Add to dashboard Cite

We spectroscopically measure multiple hydrogen Balmer line profiles from laboratory plasmas to investigate the theoretical line profiles used in white dwarf atmosphere models. X-ray radiation produced at the Z Pulsed Power Facility at Sandia National Laboratories initiates plasma formation in a hydrogen-filled gas cell, replicating white dwarf photospheric conditions. Here we present timeresolved measurements of Hβ and fit this line using different theoretical line profiles to diagnose electron density, n e , and n = 2 level population, n 2 . Aided by synthetic tests, we characterize the validity of our diagnostic method for this experimental platform. During a single experiment, we infer a continuous range of electron densities increasing from n e ∼ 4 to ∼ 30 × 10 16 cm −3 throughout a 120-ns evolution of our plasma. Also, we observe n 2 to be initially elevated with respect to local thermodynamic equilibrium (LTE); it then equilibrates within ∼ 55 ns to become consistent with LTE. This supports our electron-temperature determination of T e ∼ 1.3 eV (∼ 15, 000 K) after this time.At n e 10 17 cm −3 , we find that computer-simulation-based line-profile calculations provide better fits (lower reduced χ 2 ) than the line profiles currently used in the white dwarf astronomy community. The inferred conditions, however, are in good quantitative agreement. This work establishes an experimental foundation for the future investigation of relative shapes and strengths between different hydrogen Balmer lines.

show abstract

Section: Introductionmentioning

confidence: 99%