Saurav Dhital, Andrew A. West, Keivan G. Stassun, John J. Bochanski, Angela P. Massey, Fabienne A. Bastien
We report the results from spectroscopic observations of 113 ultra-wide,
low-mass binary systems, composed largely of M0--M3 dwarfs, from the SLoWPoKES
catalog of common proper motion pairs identified in the Sloan Digital Sky
Survey. Radial velocities of each binary member were used to confirm that they
are co-moving and, consequently, to further validate the high fidelity of the
SLoWPoKES catalog. Ten stars appear to be spectroscopic binaries based on broad
or split spectral features, supporting previous findings that wide binaries are
likely to be hierarchical systems. We measured the H{\alpha} equivalent width
of the stars in our sample and found that components of 81% of the observed
pairs has similar H{\alpha} levels. The difference in H{\alpha} equivalent
width amongst components with similar masses was smaller than the range of
H{\alpha} variability for individual objects. We confirm that the Lepine et al.
{\zeta}(CaH2+CaH3, TiO5) index traces iso-metallicity loci for most of our
sample of M dwarfs. However, we find a small systematic bias in {\zeta},
especially in the early-type M dwarfs. We use our sample to recalibrate the
definition of {\zeta}. While representing a small change in the definition, the
new {\zeta} is a significantly better predictor of iso-metallicity for the
higher mass M dwarfs.
View original:
http://arxiv.org/abs/1112.2670
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