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Stellar Diameters and Temperatures. II. Main-sequence K- and M-stars
López-Morales, Mercedes; Muirhead, Philip S.; Kane, Stephen R. +21 more
We present interferometric angular diameter measurements of 21 low-mass, K- and M-dwarfs made with the CHARA Array. This sample is enhanced by adding a collection of radius measurements published in the literature to form a total data set of 33 K-M-dwarfs with diameters measured to better than 5%. We use these data in combination with the Hipparco…
A Revised Age for Upper Scorpius and the Star Formation History among the F-type Members of the Scorpius-Centaurus OB Association
Mamajek, Eric E.; Pecaut, Mark J.; Bubar, Eric J.
We present an analysis of the ages and star formation history of the F-type stars in the Upper Scorpius (US), Upper Centaurus-Lupus (UCL), and Lower Centaurus-Crux (LCC) subgroups of Scorpius-Centaurus (Sco-Cen), the nearest OB association. Our parent sample is the kinematically selected Hipparcos sample of de Zeeuw et al., restricted to the 138 F…
Fundamental Properties of Stars Using Asteroseismology from Kepler and CoRoT and Interferometry from the CHARA Array
Kawaler, S. D.; Thompson, M. J.; Christensen-Dalsgaard, J. +37 more
We present results of a long-baseline interferometry campaign using the PAVO beam combiner at the CHARA Array to measure the angular sizes of five main-sequence stars, one subgiant and four red giant stars for which solar-like oscillations have been detected by either Kepler or CoRoT. By combining interferometric angular diameters, Hipparcos paral…
Verifying Asteroseismically Determined Parameters of Kepler Stars Using Hipparcos Parallaxes: Self-consistent Stellar Properties and Distances
Christensen-Dalsgaard, J.; Weiss, A.; García, R. A. +24 more
Accurately determining the properties of stars is of prime importance for characterizing stellar populations in our Galaxy. The field of asteroseismology has been thought to be particularly successful in such an endeavor for stars in different evolutionary stages. However, to fully exploit its potential, robust methods for estimating stellar param…
Distance and Kinematics of the Red Hypergiant VY CMa: Very Long Baseline Array and Very Large Array Astrometry
Menten, K. M.; Zhang, B.; Reid, M. J. +1 more
We report astrometric results of phase-referencing very long baseline interferometry observations of 43 GHz SiO maser emission toward the red hypergiant VY Canis Majoris (VY CMa) using the Very Long Baseline Array (VLBA). We measured a trigonometric parallax of 0.83 ± 0.08 mas, corresponding to a distance of 1.20+0.13 -0.10 k…
A Spitzer MIPS Study of 2.5-2.0 M ⊙ Stars in Scorpius-Centaurus
Chen, Christine H.; Mamajek, Eric E.; Su, Kate Y. L. +2 more
We have obtained Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) 24 µm and 70 µm observations of 215 nearby, Hipparcos B- and A-type common proper-motion single and binary systems in the nearest OB association, Scorpius-Centaurus. Combining our MIPS observations with those of other ScoCen stars in the literature…
Active Learning to Overcome Sample Selection Bias: Application to Photometric Variable Star Classification
Miller, Adam A.; Bloom, Joshua S.; Richards, Joseph W. +6 more
Despite the great promise of machine-learning algorithms to classify and predict astrophysical parameters for the vast numbers of astrophysical sources and transients observed in large-scale surveys, the peculiarities of the training data often manifest as strongly biased predictions on the data of interest. Typically, training sets are derived fr…
New Evidence Supporting Cluster Membership for the Keystone Calibrator Delta Cephei
Gieren, W.; Turner, D.; Majaess, D.
New and existing UBVJHKs , spectroscopic, NOMAD, Hubble Space Telescope, and revised Hipparcos observations are employed to determine properties for δ Cep and its host star cluster. The multi-faceted approach ensured that uncertainties were mitigated (σ/d ~ 2%). The following fundamental parameters were inferred for δ Cep: E(B - V) = 0.…
Identification of Galactic Bulge Survey X-Ray Sources with Tycho-2 Stars
Maccarone, T. J.; Torres, M. A. P.; Nelemans, G. +6 more
We identify 69 X-ray sources discovered by the Galactic Bulge Survey (GBS) that are coincident with or very close to bright stars in the Tycho-2 catalog. Additionally, two other GBS sources are resolved binary companions to Tycho-2 stars where both components are separately detected in X-rays. Most of these are likely to be real matches, but we id…
Discovery of the Host Cluster for the Fundamental Cepheid Calibrator Zeta Geminorum
Gieren, W.; Balam, D.; Lane, D. +2 more
New and existing CORAVEL, UBVJHKs , HST, HIP/Tycho, ARO, KPNO, and DAO observations imply that the fundamental Cepheid calibrator ζ Gem is a cluster member. The following parameters were inferred for ζ Gem from cluster membership and are tied to new spectral classifications (DAO) established for 26 nearby stars (e.g., HD53588/B7.5IV, HD…