IR excesses around nearby Lambda Boo stars are caused by debris discs rather than ISM bow waves

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DOIResolve DOI: http://doi.org/10.1093/mnras/stv2696
AuthorSearch for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for:
TypeArticle
Journal titleMonthly Notices of the Royal Astronomical Society
ISSN0035-8711
1365-2966
Volume456
Issue1
Pages459476
SubjectChemically peculiar stars; Circumstellar matter
AbstractLambda Boo stars are predominately A-type stars with solar abundant C, N, O, and S, but up to 2 dex underabundances of refractory elements. The stars’ unusual surface abundances could be due to a selective accretion of volatile gas over dust. It has been proposed that there is a correlation between the Lambda Boo phenomenon and IR excesses which are the result of a debris disc or interstellar medium (ISM) interaction providing the accreting material. We observe 70 or 100 and 160-μm excess emission around nine confirmed Lambda Boo stars with the Herschel Space Observatory, to differentiate whether the dust emission is from a debris disc or an ISM bow wave. We find that 3/9 stars observed host well-resolved debris discs. While the remaining 6/9 are not resolved; they are inconsistent with an ISM bow wave based on the dust emission being more compact for its temperature and predicted bow-wave models produce hotter emission than what is observed. We find the incidence of bright IR excesses around Lambda Boo stars is higher than normal A-stars. To explain this, given our observations, we explore Poynting–Robertson drag as a mechanism of accretion from a debris disc but find it insufficient. As an alternative, we propose the correlation is due to higher dynamical activity in the discs currently underway. Large impacts of planetesimals or a higher influx of comets could provide enough volatile gas for accretion. Further study on the transport of circumstellar material in relation to the abundance anomalies are required to explain the phenomenon through external accretion.
Publication date
PublisherOxford Unversity Press
LanguageEnglish
AffiliationNational Science Infrastructure; National Research Council Canada
Peer reviewedYes
NPARC number23000037
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Record identifierdd99afbd-a1a3-4266-a75a-8b3f29cf8d2a
Record created2016-05-31
Record modified2016-05-31
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