Dynamical masses of M-dwarf binaries in young moving groups: II – Toward empirical mass-luminosity isochrones. (arXiv:1811.11802v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Janson_M/0/1/0/all/0/1">Markus Janson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Durkan_S/0/1/0/all/0/1">Stephen Durkan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonnefoy_M/0/1/0/all/0/1">Mickael Bonnefoy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodet_L/0/1/0/all/0/1">Laetitia Rodet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kohler_R/0/1/0/all/0/1">Rainer Kohler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lacour_S/0/1/0/all/0/1">Sylvestre Lacour</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brandner_W/0/1/0/all/0/1">Wolfgang Brandner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Henning_T/0/1/0/all/0/1">Thomas Henning</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Girard_J/0/1/0/all/0/1">Julien Girard</a>
Low-mass stars exhibit substantial pre-main sequence evolution during the
first ~100 Myrs 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 Msun and bolometric luminosities in
log(L/Lsun) 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.
Low-mass stars exhibit substantial pre-main sequence evolution during the
first ~100 Myrs 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 Msun and bolometric luminosities in
log(L/Lsun) 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.
http://arxiv.org/icons/sfx.gif
