Journal Article

The emission line near 1319 Å in solar and stellar spectra

C. Jordan

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 1, pages 634-641
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18428.x
The emission line near 1319 Å in solar and stellar spectra

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An emission line at ≃1319Å is one of the strongest unidentified lines in the ultraviolet spectra of cool dwarf stars. In most lists of solar and stellar lines it is identified as a transition in N i, although its intensity would then be anomalous and the wavelength does not precisely fit that expected for N i. The line is also observed in giant stars but becomes very weak in supergiants, relative to photoexcited lines of neutral atoms. The measured wavelength of the line in stellar spectra is 1318.94 ± 0.01 Å. Observations of giant stars provide further information that shows that this line is not due to N i. It is proposed that the line is due to a decay from the 3p3(2Do)3d 1Do2 level of S i, above the first ionization limit. The previous tentative assignment of this upper level to an S i line at ≃1309.3Å then needs to be revised. The 1309.3-Å line is identified here for the first time in an astrophysical source. The 3d 1Do2 level could, in principle, be populated by collisions from nearby autoionizing levels that are shown to have large number densities, through population by low-temperature dielectronic capture. Spin–orbit interaction with the autoionizing 3d 3Do2 level might also lead to dielectronic capture into the 3d 1Do2 level. A line at 1309.87 Å observed in cool giant stars is identified as a transition in P ii, pumped by the O i resonance lines.

Keywords: line: formation; line: identification; stars: chromospheres; stars: late-type

Journal Article.  8384 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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