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Spectroscopic confirmation of M-dwarf candidate members of the Beta Pictoris and AB Doradus Moving Groups

Spectroscopic confirmation of M-dwarf candidate members of the Beta Pictoris and AB Doradus Moving Groups Thumbnail


Abstract

Optical spectroscopic observations are reported for 24 and 23, nearby, proper-motion-selected M-dwarf candidate members of the Beta Pictoris and AB Doradus moving groups (BPMG and ABDMG). Using kinematic criteria, the presence of both Halpha emission and high X-ray-to-bolometric luminosity, and position in absolute colour-magnitude diagrams, 10 and 6 of these candidates are confirmed as likely members of the BPMG and ABDMG respectively. Equivalent widths or upper limits for the Li I 6708A line are reported and the lithium depletion boundary (LDB) age of the BPMG is revisited. Whilst non-magnetic evolutionary models still yield an estimated age of 21 +/- 4 Myr, models that incorporate magnetic inhibition of convection imply an older age of 24 +/- 4 Myr. A similar systematic increase would be inferred if the stars were 25 per cent covered by dark magnetic starspots. Since young, convective M-dwarfs are magnetically active and do have starspots, we suggest that the original LDB age estimate is a lower limit. The LDB age of the ABDMG is still poorly constrained -- non-magnetic evolutionary models suggest an age in the range 35-150 Myr, which could be significantly tightened by new measurements for existing candidate members.

Journal Article Type Article
Acceptance Date Oct 28, 2015
Online Publication Date Nov 29, 2015
Publication Date Jan 21, 2016
Publicly Available Date Mar 28, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 455
Issue 3
Pages 3345-3358
DOI https://doi.org/10.1093/mnras/stv2431
Keywords stars, kinematics, pre-main-sequence, late-type
Publisher URL http://dx.doi.org/10.1093/mnras/stv2431

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