Search Publications
The Effective Temperature Scale of FGK Stars. II. Teff:Color:[Fe/H] Calibrations
Meléndez, Jorge; Ramírez, Iván
We present up-to-date metallicity-dependent temperature versus color calibrations for main-sequence and giant stars based on temperatures derived with the infrared flux method (IRFM). Seventeen colors in the photometric systems UBV, uvby, Vilnius, Geneva, RI(Cousins), DDO, Hipparcos-Tycho, and Two Micron All Sky Survey (2MASS) have been calibrated…
Ice Age Epochs and the Sun's Path through the Galaxy
Gies, D. R.; Helsel, J. W.
We present a calculation of the Sun's motion through the Milky Way over the last 500 million yr. The integration is based on estimates of the Sun's current position and speed from measurements with Hipparcos and on a realistic model for the Galactic gravitational potential. We estimate the times of the Sun's past spiral arm crossings for a range o…
Modeling Complete Distributions with Incomplete Observations: The Velocity Ellipsoid from Hipparcos Data
Hogg, David W.; Johnston, Kathryn V.; Blanton, Michael R. +1 more
An algorithm is developed to model the three-dimensional velocity distribution function of a sample of stars using only measurements of each star's two-dimensional tangential velocity. The algorithm works with ``missing data'': it reconstructs the three-dimensional distribution from data (velocity measurements) that all have one dimension that is …
The Age and Progenitor Mass of Sirius B
Holberg, J. B.; Liebert, James; Williams, Kurtis A. +2 more
The Sirius AB binary system has masses that are well determined from many decades of astrometric measurements. Because of the well-measured radius and luminosity of Sirius A, we employed the TYCHO stellar evolution code to determine the age of the Sirius AB binary system accurately, at 225-250 Myr. Note that this fit requires the assumption of sol…
Absolute Proper Motion of the Sagittarius Dwarf Galaxy and of the Outer Regions of the Milky Way Bulge
Girard, Terrence M.; van Altena, William F.; López, Carlos E. +1 more
We have determined the absolute proper motion of the Sagittarius dwarf spheroidal galaxy (Sgr) from the Southern Proper Motion Catalog 3, by selecting red giant candidates from the Two Micron All Sky Survey. We obtain µlcosb=-2.35+/-0.20 and µb=2.07+/-0.20 mas yr-1. Using the same procedure, we also det…
Interstellar Ca II Line Intensities and the Distances of the OB stars
Galazutdinov, G. A.; Han, Inwoo; Strobel, A. +4 more
We show that the equivalent widths of the well-known interstellar Ca II H and K lines can be used to determine the distances to OB stars in our Galaxy. The equivalent widths, measured in the spectra of 147 early-type stars, are strongly related to the Hipparcos parallaxes of those objects. The lines fitted to the parallax-equivalent width data are…
Absolute Proper Motion of the Canis Major Dwarf Galaxy Candidate
Rix, Hans-Walter; Peñarrubia, Jorge; Girard, Terrence M. +4 more
We have measured the absolute proper motion of the candidate Canis Major dwarf galaxy (CMa), at (l,b)=(240°,-8°). Likely main-sequence stars in CMa have been selected from a region in the color-magnitude diagram that has very little contamination from known Milky Way components. We obtain µlcosb=-1.47+/-0.37 and µb
Direct Evidence for a Polar Spot on SV Camelopardalis
Jeffers, S. V.; Collier Cameron, A.; Barnes, J. R. +2 more
We have used spectrophotometric data from the Hubble Space Telescope (HST) to eclipse-map the primary component of the RS CVn binary SV Cam over nine HST orbits. We find from these observations and the Hipparcos parallax that the surface flux in the eclipsed low-latitude region of the primary is about 30% lower than that computed from a PHOENIX mo…