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| Paper: |
Rotational Velocities of Very Low Mass Binaries |
| Volume: |
448, 16th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun |
| Page: |
147 |
| Authors: |
Konopacky, Q. M.; Ghez, A. M.; Macintosh, B. A.; White, R. J.; Barman, T. S.; Rice, E. L.; Hallinan, G. |
| Abstract: |
We present rotational velocities for individual components
of eleven very low mass (VLM) binaries with spectral types
between M7.5 and L4. These results are based on observations
taken with the near-infrared spectrograph, NIRSPEC, and the
Keck II laser guide star adaptive optics (LGS AO) system. The
binaries were targeted as part of a dynamical mass program,
and their orbital inclinations are used to translate vsini
into a rotational velocity for each component. We find that
the observed sources tend to be rapid rotators (vsini > 10 km
s-1), consistent with previous measurements for ultracool
objects. Five systems have component vsini's
that are statistically different, with three binaries having
velocity differences greater than 25 km s-1. To bring these
discrepant rotational velocities into agreement would require
their rotational axes to be inclined between 10 to 40°
with respect to each other, and that at least one
component has a significant inclination with respect to the
orbital plane. Alternatively, each component could be rotating
at a different rate, even though they have similar spectral
types. Both differing rotational velocities and inclinations
have interesting implications for binary star formation. Two
of the binaries with large differences in rotational velocity
are also known radio sources, LP 349-25AB and 2MASS 0746+20AB.
LP 349-25B is rotating at ∼95 km s-1, within a factor of ∼3 of
the break up speed, and is one of the most rapidly rotating
VLM objects known. |
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