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Emission lines in the atmosphere of the irradiated brown dwarf WD0137-349B

Longstaff, E.S.; Casewell, S.L.; Wynn, G.A.; Maxted, P.F.L.; Helling, Ch.

Emission lines in the atmosphere of the irradiated brown dwarf WD0137-349B Thumbnail


Authors

E.S. Longstaff

S.L. Casewell

G.A. Wynn

Ch. Helling



Abstract

We present new optical and near-infrared spectra of WD0137-349; a close white dwarf–brown dwarf non-interacting binary system with a period of ˜114 min. We have confirmed the presence of Ha emission and discovered He, Na, Mg, Si, K, Ca, Ti and Fe emission lines originating from the brown-dwarf atmosphere. This is the first brown-dwarf atmosphere to have been observed to exhibit metal emission lines as a direct result of intense irradiation. The equivalent widths of many of these lines showa significant difference between the day-side and night-side of the brown dwarf. This is likely an indication that efficient heat redistribution may not be happening on this object, in agreement with models of hot Jupiter atmospheres. The Ha line strength variation shows a strong phase dependency as does the width.We have simulated the Ca II emission lines using a model that includes the brown-dwarf Roche geometry and limb darkening, and we estimate the mass ratio of the system to be 0.135 ± 0.004. We also apply a gas-phase equilibrium code using a prescribed DRIFT-PHOENIX model to examine how the chemical composition of the brown-dwarf upper atmosphere would change given an outward temperature increase, and discuss the possibility that this would induce a chromosphere above the brown-dwarf atmosphere.

Journal Article Type Article
Acceptance Date Jul 13, 2017
Online Publication Date Jul 15, 2017
Publication Date 2017-10
Publicly Available Date Mar 29, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 471
Issue 2
Pages 1728 - 1736
DOI https://doi.org/10.1093/mnras/stx1786
Keywords binaries, close, brown dwarfs, white dwarfs
Publisher URL https://doi.org/10.1093/mnras/stx1786

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