Search Publications
The Rotation-Activity Correlations in K and M Dwarfs. II. New Constraints on the Dynamo Mechanisms in Late-K and M Dwarfs Before and At the Transition to Complete Convection
Mullan, D. J.; Gebran, M.; Houdebine, E. R. +2 more
We study the rotation-activity correlations (RACs) in a sample of stars from spectral type dK4 to dM4. We study RACs using chromospheric data and coronal data. We study the Ca II line surface fluxes-P/\sin I RACs. We fit the RACs with linear homoscedastic and heteroscedastic regression models. We find that these RACs differ substantially from one …
The Surface Brightness-color Relations Based on Eclipsing Binary Stars: Toward Precision Better than 1% in Angular Diameter Predictions
Gieren, Wolfgang; Pietrzyński, Grzegorz; Maxted, Pierre F. L. +7 more
In this study we investigate the calibration of surface brightness-color (SBC) relations based solely on eclipsing binary stars. We selected a sample of 35 detached eclipsing binaries with trigonometric parallaxes from Gaia DR1 or Hipparcos whose absolute dimensions are known with an accuracy better than 3% and that lie within 0.3 kpc from the Sun…
Absolute Magnitudes of Seismic Red Clumps in the Kepler Field and SAGA: The Age Dependency of the Distance Scale
Zhao, G.; Casagrande, L.; Bovy, J. +4 more
Red clump stars are fundamental distance indicators in astrophysics, although theoretical stellar models predict a dependence of absolute magnitudes with age. This effect is particularly strong below ∼2 Gyr, but even above this limit a mild age dependence is still expected. We use seismically identified red clump stars in the Kepler field for whic…
Testing Metal-Poor Stellar Models and Isochrones with HST Parallaxes of Metal-Poor Stars
McArthur, B. E.; Benedict, G. F.; Sarajedini, A. +7 more
Hubble Space Telescope (HST) fine guidance sensor observations were used to obtain parallaxes of eight metal-poor ([Fe/H] < -1.4) stars. The parallaxes of these stars determined by the new Hipparcos reduction average 17% accuracy, in contrast to our new HST parallaxes, which average 1% accuracy and have errors on the individual parallaxes rangi…
VLBA Trigonometric Parallax Measurement of the Semi-regular Variable RT Vir
Menten, Karl M.; Honma, Mareki; Reid, Mark J. +4 more
We report a trigonometric parallax measurement of 22 GHz H2O masers toward the semi-regular variable RT Vir from multi-epoch Very Long Baseline Array observations. The parallax of 4.417 ± 0.134 mas, corresponding to a distance of 226 ± 7 pc, is significantly different from the Hipparcos parallax, but is consistent with a distance derive…
Double Stars and Astrometric Uncertainties in Gaia DR1
Makarov, Valeri V.; Frouard, Julien; Fabricius, Claus
A significant number of double stars with separations up to 2.5 arcsec are present in the Gaia Data Release 1 astrometric catalogs. Limiting our analysis to a well-studied sample of 1124 doubles resolved by Hipparcos, provided with individual Tycho component photometry and cross-matched with the TGAS catalog, we estimate a rate of at least 3% for …
Accurate Orbital Solution for the New and Metal-poor Eclipsing Binary Tycho 5227-1023-1
Munari, U.; Zwitter, T.; Traven, G. +1 more
The orbit and physical parameters of the previously unsolved double-lined eclipsing binary Tyc 5227-1023-1, discovered during the search for RR Lyr variable candidate members of the Aquarius stream, are derived using high-resolution échelle spectroscopy and V,{I}\prime photometry. A synthetic spectral analysis of both components has be…