Search Publications
The Peculiar Solar Composition and Its Possible Relation to Planet Formation
Gustafsson, B.; Yong, D.; Asplund, M. +1 more
We have conducted a differential elemental abundance analysis of unprecedented accuracy (~0.01 dex) of the Sun relative to 11 solar twins from the Hipparcos catalog and 10 solar analogs from planet searches. We find that the Sun shows a characteristic signature with a ≈20% depletion of refractory elements relative to the volatile elements in compa…
The Extreme Microlensing Event OGLE-2007-BLG-224: Terrestrial Parallax Observation of a Thick-Disk Brown Dwarf
Lee, C. -U.; Fouque, P.; Bennett, D. P. +75 more
Parallax is the most fundamental technique for measuring distances to astronomical objects. Although terrestrial parallax was pioneered over 2000 years ago by Hipparchus (ca. 140 B.C.E.) to measure the distance to the Moon, the baseline of the Earth is so small that terrestrial parallax can generally only be applied to objects in the Solar System.…
Galactic Globular and Open Clusters in the Sloan Digital Sky Survey. II. Test of Theoretical Stellar Isochrones
Beers, Timothy C.; Masseron, Thomas; Pinsonneault, Marc H. +6 more
We perform an extensive test of theoretical stellar models for main-sequence (MS) stars in ugriz, using cluster fiducial sequences obtained in the previous paper of this series. We generate a set of isochrones using the Yale Rotating Evolutionary Code with updated input physics, and derive magnitudes and colors in ugriz from MARCS model atmosphere…
Deep 2MASS Photometry of M67 and Calibration of the Main-Sequence J - KS Color Difference as an Age Indicator
Kirkpatrick, Allison; Dotter, Aaron; Sarajedini, Ata
We present an analysis of Two Micron All Sky Survey (2MASS) calibration photometry of the old open cluster M67 (NGC 2682). The proper-motion-cleaned color-magnitude diagram (CMD) resulting from these data extends ~3 mag deeper than one based on data from the point source catalog. The CMD extends from above the helium-burning red clump to a faint l…
The Velocity Distribution of Nearby Stars from Hipparcos Data. I. The Significance of the Moving Groups
Bovy, Jo; Hogg, David W.; Roweis, Sam T.
We present a three-dimensional reconstruction of the velocity distribution of nearby stars (lsim100 pc) using a maximum likelihood density estimation technique applied to the two-dimensional tangential velocities of stars. The underlying distribution is modeled as a mixture of Gaussian components. The algorithm reconstructs the error-deconvolved d…
2MASS 22344161+4041387AB: A Wide, Young, Accreting, Low-Mass Binary in the LkHα233 Group
Shkolnik, Evgenya; Cushing, Michael C.; Dupuy, Trent J. +6 more
We report the discovery of a young, 0farcs16 binary, 2M2234+4041AB, found as the result of a Keck laser guide star adaptive optics imaging survey of young field ultracool dwarfs. Spatially resolved near-infrared photometry and spectroscopy indicate that the luminosity and temperature ratios of the system are near unity. From optical and near-infra…
V3885 Sagittarius: A Comparison with a Range of Standard Model Accretion Disks
Szkody, Paula; Sion, Edward M.; Godon, Patrick +3 more
A \widetilde{χ}^2 analysis of standard model accretion disk synthetic spectrum fits to combined Far Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph spectra of V3885 Sagittarius, on an absolute flux basis, selects a model that accurately represents the observed spectral energy distribution. Calculation of the synthetic s…
Hipparcos Calibration of the Tip of the Red Giant Branch
Bedding, Timothy R.; Tabur, Vello; Kiss, László L.
We have detected the tip of the red giant branch (TRGB) in the solar neighborhood using near-infrared photometry from the Two Micron All Sky Survey and DIRBE catalogs, and revised Hipparcos parallaxes. We confirm that the revised Hipparcos parallaxes are superior to the original ones, and that this improvement is necessary to detect the TRGB. We f…
G 112-29 (=NLTT 18149): A Very Wide Companion to GJ 282 AB with a Common Proper Motion, Common Parallax, Common Radial Velocity, and Common Age
Costero, R.; Poveda, A.; Echevarría, J. +2 more
We have made a search for common proper motion (CPM) companions to the wide binaries in the solar vicinity. We found that the binary GJ 282AB has a very distant CPM companion (NLTT 18149) at a separation s = 1fdg09. Improved spectral types and radial velocities are obtained, and ages determined for the three components. The Hipparcos trigonometric…
HR 8257: A Three-Dimensional Orbit and Basic Properties
Torres, Guillermo; Fekel, Francis C.; Boden, Andrew F. +1 more
We have used interferometric and spectroscopic observations of HR 8257 to determine a three-dimensional orbit of the system. The orbit has a period of 12.21345 days and an eccentricity of 0.2895. The masses of the F0 and F2 dwarf components are 1.56 and 1.38 M sun, respectively, with fractional errors of 1.4%. Our orbital parallax of 13…