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Dynamical masses of M-dwarf binaries in young moving groups II. Toward empirical mass-luminosity isochrones
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy. Queens University Belfast, UK.
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Number of Authors: 92018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 620, article id A33Article in journal (Refereed) Published
Abstract [en]

Low-mass stars exhibit substantial pre-main sequence evolution during the first similar to 100 Myr of their lives. Thus, young M-type stars are prime targets for isochronal dating, especially in young moving groups (YMGs), which contain large amounts of stars in this mass and age range. If the mass and luminosity of a star can both be directly determined, this allows for a particularly robust isochronal analysis. This motivates in-depth studies of low-mass binaries with spatially resolvable orbits, where dynamical masses can be derived. Here we present the results of an observing campaign dedicated to orbital monitoring of AB Dor Ba/Bb, which is a close M-dwarf pair within the quadruple AB Dor system. We have acquired eight astrometric epochs with the SPHERE /ZIMPOL and NACO instruments, which we combine with literature data to improve the robustness and precision for the orbital characterization of the pair. We find a system mass 0.66(-0.12)(+0.12) M-circle dot and bolometric luminosities in log L/L-circle dot of 2 .02 +/- 0.02 and 2 .11 +/- 0.02 for AB Dor Ba and Bb, respectively. These measurements are combined with other YMG pairs in the literature to start building a framework of empirical isochrones in mass-luminosity space. This can be used to calibrate theoretical isochrones and to provide a model-free basis for assessing relative stellar ages. We note a tentative emerging trend where the youngest moving group members are largely consistent with theoretical expectations, while stars in older associations such as the AB Dor moving group appear to be systematically underluminous relative to isochronal expectations.

Place, publisher, year, edition, pages
2018. Vol. 620, article id A33
Keywords [en]
binaries: visual, stars: low-mass, stars: pre-main sequence
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-162752DOI: 10.1051/0004-6361/201833375ISI: 000451249600001OAI: oai:DiVA.org:su-162752DiVA, id: diva2:1274864
Available from: 2019-01-03 Created: 2019-01-03 Last updated: 2019-01-03Bibliographically approved

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