Orbitally modulated photoexcited Si I emission in the eclipsing composite-spectrum binary [zeta] Aurigae

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dc.creator Harper, G. M.
dc.creator Griffin, R. E. M.
dc.creator Bennett, Philip Desmond, 1952-
dc.creator O’Riain, N.
dc.date.accessioned 2018-02-13T14:01:22Z
dc.date.available 2018-02-13T14:01:22Z
dc.date.issued 2016-02-21
dc.identifier.issn 0035-8711
dc.identifier.uri http://library2.smu.ca/handle/01/27273
dc.description Publisher's Version/PDF
dc.description.abstract We examine the little-known phenomenon of orbitally modulated Si I emission at [lambda] 3905.523 [angstrom] and [lambda] 4102.936 [angstrom] in composite-spectrum binaries, with specific reference to [zeta] Aurigae (K4 Ib + B5 V). The emission is detected in the isolated spectrum of the B-type dwarf secondary, and while [lambda] 4102 [angstrom] is heavily blended with H[delta], [lambda] 3905 [angstrom] falls in the B-star’s featureless continuum. The narrowness of the emission (v [subscript turb] [similar or equal to] 6 km s[superscript-1]) demonstrates that it originates in the upper photosphere or deep chromosphere of the K star primary. We propose that photoexcitation by the hot star’s UV continuum, followed by recombination and cascades, leads to resonant scattering and subsequent pumping of lower opacity transitions in the singlet and triplet systems of Si I. This process channels the UV continuum into select narrow emission lines. We have also identified weaker photoexcited emission of Fe II at [lambda] 3938.289 [angstrom]. The strengths, positions, and widths of the [lambda] 3905 [angstrom] emission line vary with orbital phase owing to changes in the dilution of the irradiating flux and in the geometrical aspect of the irradiated hemisphere. Utilizing the inherent spatial resolution provided by the illuminated patch, and assuming that the K star is spherical with isotropic emission, yields vsin i [similar to] 5.7 km s[superscript-1]. Evidence of tidal distortion was deduced from the timing of the rapidly rising phase of the emission just after periastron. Increasing the diagnostic potential requires radiative transfer modelling of the formation and centre-to-limb variation of the emission. en_CA
dc.language.iso en en_CA
dc.publisher Oxford University Press en_CA
dc.relation.uri https://dx.doi.org/10.1093/mnras/stv2668
dc.rights This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
dc.subject.lcsh Eclipsing binaries
dc.subject.lcsh Double stars -- Spectra
dc.title Orbitally modulated photoexcited Si I emission in the eclipsing composite-spectrum binary [zeta] Aurigae en_CA
dc.type Text en_CA
dcterms.bibliographicCitation Monthly Notices of the Royal Astronomical Society 456(2), 1346-1358. (2016) en_CA


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This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
 
Published Version: https://dx.doi.org/10.1093/mnras/stv2668
 
 

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