Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
M. Kenworthy, K.-H. Hofmann, L. Close,
P. Hinz, E. Mamajek, D. Schertl,
G. Weigelt, R. Angel, Y. Balega, J. Hinz, and G. Rieke
Gliese 569B: A young multiple brown dwarf
system?
Astrophysical Journal (Letters) 554, L67-L70
(2001)
Abstract.
The nearby late M star Gliese 569B was recently found by adaptive
optics
imaging to be a double with separation ~1 AU. To explore the orbital
motion and
masses, we have undertaken a high resolution (~0.05 arcsec) astrometric
study.
Images were obtained over 1.5 years with bispectrum speckle
interferometry at
the 6.5m MMT and 6m SAO telescopes. Our data show motion corresponding
to more
than half the orbital period, and constrain the total mass to be >
0.115
M_solar, with a most probable value of 0.145 M_solar. Higher masses
cannot be
excluded without more extended observations, but from statistical
analysis we
find an 80% probability that the total mass is less than 0.21 M_solar.
An infrared spectrum of the blended B double obtained with the MMT has
been
modeled as a blend of two different spectral types, chosen to be
consistent
with the measured J and K band brightness difference of a factor ~2.
The
blended fit is not nearly as good as that to a pure M8.5+ template.
Therefore
we hypothesize that the brighter component likely has two unresolved
components
with near equal masses, each the same as the fainter component.
If Gl 569B is a triple our dynamical limits suggest each component has
a
mass of 50 (+23/-4) M_jupiter. We infer an age for the system of 300
Myr, from
its kinematic motion which places its as a member of the Ursa Major
moving
group. All the above parameters are consistent with the latest DUSTY
evolutiuon
models for brown dwarfs.
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