Kyle A. McCarthy, Russel J. White
We present moderate resolution (R $\sim$ 3575) optical spectra of 19 known or
suspected members of the AB Doradus and $\beta$ Pictoris Moving Groups,
obtained with the DeVeny Spectrograph on the 72-inch Perkins telescope at
Lowell Observatory. For 4 of 5 recently proposed members, signatures of youth
such as Li\,I 6708 \AA\, absorption and H$\alpha$ emission further strengthen
the case for youth and membership. Effective temperatures are determined via
line ratio analyses for the 11 F, G and early K stars observed, and via
spectral comparisons for the 8 late-K and M stars observed. We assemble updated
candidate membership lists for these Moving Groups that account for known
binarity. We then use temperature, luminosity, and distance estimates to
predict angular diameters for these stars; the motivation is to identify stars
that can be spatially resolved with long-baseline optical/infrared
interferometers in order to improve age estimates for these Groups and to
constrain evolutionary models at young ages. Considering the portion of the sky
accessible to northern hemisphere facilities (DEC $> -30$), 6 stars have
diameters large enough to be spatially resolved ($\theta > 0.4$ mas) with the
CHARA Array; this subsample includes the low mass M2.5 member of AB Dor, GJ
393, which is likely to still be pre-main sequence. For southern hemisphere
facilities (DEC $< +30$), 18 stars have diameters larger than this limiting
size, including the low mass debris disk star AU Mic (0.72 mas). However, the
longest baselines of southern hemisphere interferometers (160-m) are only able
to resolve the largest of these, the B6 star $\alpha$ Gru (1.17 mas); proposed
long-baseline stations may alleviate the current limitations.
View original:
http://arxiv.org/abs/1201.6600
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