The Gaia Ultra-Cool Dwarf Sample — II: Structure at the end of the main sequence. (arXiv:1902.07571v1 [astro-ph.SR])

The Gaia Ultra-Cool Dwarf Sample — II: Structure at the end of the main sequence. (arXiv:1902.07571v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Smart_R/0/1/0/all/0/1">R. L. Smart</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Marocco_F/0/1/0/all/0/1">F. Marocco</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sarro_L/0/1/0/all/0/1">L. M. Sarro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barrado_D/0/1/0/all/0/1">D. Barrado</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beamin_J/0/1/0/all/0/1">J. C. Beamin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Caballero_J/0/1/0/all/0/1">J. A. Caballero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jones_H/0/1/0/all/0/1">H. R. A. Jones</a>

We identify and investigate known late M, L and T dwarfs in the Gaia second
data release. This sample is being used as a training set in the Gaia data
processing chain of the ultra cool dwarfs work package. We find 695 objects in
the optical spectral range M8 to T6 with accurate Gaia coordinates, proper
motions, and parallaxes which we combine with published spectral types and
photometry from large area optical and infrared sky surveys. We find that 100
objects are in 47 multiple systems, of which 27 systems are published and 20
are new. These will be useful benchmark systems and we discuss the requirements
to produce a complete catalog of multiple systems with an ultra cool dwarf
component. We examine the magnitudes in the Gaia passbands and find that the
GBP magnitudes are unreliable and should not be used for these objects. We
examine progressively redder colour magnitude diagrams and see a notable
increase in the main sequence scatter and a bivariate main sequence for old and
young objects. We provide an absolute magnitude spectral sub-type calibration
for G and GRP passbands along with linear fits over the range M8 L8 for other
passbands.

We identify and investigate known late M, L and T dwarfs in the Gaia second
data release. This sample is being used as a training set in the Gaia data
processing chain of the ultra cool dwarfs work package. We find 695 objects in
the optical spectral range M8 to T6 with accurate Gaia coordinates, proper
motions, and parallaxes which we combine with published spectral types and
photometry from large area optical and infrared sky surveys. We find that 100
objects are in 47 multiple systems, of which 27 systems are published and 20
are new. These will be useful benchmark systems and we discuss the requirements
to produce a complete catalog of multiple systems with an ultra cool dwarf
component. We examine the magnitudes in the Gaia passbands and find that the
GBP magnitudes are unreliable and should not be used for these objects. We
examine progressively redder colour magnitude diagrams and see a notable
increase in the main sequence scatter and a bivariate main sequence for old and
young objects. We provide an absolute magnitude spectral sub-type calibration
for G and GRP passbands along with linear fits over the range M8 L8 for other
passbands.

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