Search Publications
The Galactic Disk Mass Budget. I. Stellar Mass Function and Density
Chabrier, Gilles
In this paper, we use the general theory worked out within the past few years for the structure and the evolution of low-mass stars to derive the stellar mass function in the Galactic disk down to the vicinity of the hydrogen-burning limit from the observed nearby luminosity functions. The accuracy of the mass-magnitude relationships derived from …
First Results from the Anglo-Australian Planet Search: A Brown Dwarf Candidate and a 51 Peg-like Planet
Butler, R. Paul; Vogt, Steven S.; Henry, Gregory W. +5 more
We report results from the Anglo-Australian Planet Search, a survey for planets around 200 solar-type stars in the southern hemisphere that is being carried out on the 3.9 m Anglo-Australian Telescope. Limiting Doppler precisions of 3 m s-1 have been demonstrated from the first 2.5 years of operation, making this the highest-precision planet searc…
Models for Old, Metal-poor Stars with Enhanced α-Element Abundances. III. Isochrones and Isochrone Population Functions
VandenBerg, Don A.; Bergbusch, Peter A.
An isochrone population function (IPF) gives the relative distribution of stars along an isochrone. IPFs contain the information needed to calculate both luminosity functions and color functions, and they provide a straightforward way of generating synthetic stellar populations. An improved algorithm for interpolating isochrones and IPFs, based on…
The White Dwarf Distance to the Globular Cluster 47 Tucanae and its Age
Zoccali, M.; Bragaglia, A.; Rich, R. M. +9 more
We present a new determination of the distance (and age) of the Galactic globular cluster 47 Tucanae (NGC 104) based on the fit of its white dwarf (WD) cooling sequence with the empirical fiducial sequence of local WD with known trigonometric parallax, following the method described by Renzini and collaborators. Both the cluster and the local WDs …
Oxygen in the Very Early Galaxy
Basri, Gibor; Israelian, Garik; Rebolo, Rafael +4 more
Oxygen abundances in a sample of ultra-metal-poor subdwarfs have been derived from measurements of the oxygen triplet at 7771-5 Å and OH lines in the near-UV performed in high-resolution and high signal-to-noise ratio spectra obtained with WHT/UES, Keck I/HIRES, and VLT/UVES. Our Fe abundances were derived in LTE and then corrected for non-LTE (NL…
Oxygen Abundances in Metal-poor Stars (-2.2<[Fe/H]<-1.2) from Infrared OH Lines
Meléndez, Jorge; Barbuy, Beatriz; Spite, François
Infrared OH lines at 1.55-1.56 µm in the H band were obtained with the Phoenix high-resolution spectrograph at the 2.1 m telescope of the Kitt Peak National Observatory for a sample of 14 metal-poor stars. Detailed analyses of the sample stars have been carried out, deriving stellar parameters based on two methods: (a) spectroscopic paramete…
Observational Tests and Predictive Stellar Evolution
Liebert, James; Mamajek, E. E.; Arnett, David +1 more
We compare 18 binary systems with precisely determined radii and masses from 23 to 1.1 Msolar and stellar evolution models produced with our newly revised code TYCHO. ``Overshooting'' and rotational mixing were suppressed in order to establish a baseline for isolating these and other hydrodynamic effects. Acceptable coeval fits are foun…
Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions
Han, Inwoo; Gatewood, George; Black, David C.
As a first step in the implementation of an astrometric survey, we have reduced the Hipparcos intermediate astrometric data (IAD) for 30 stars that currently exhibit small-amplitude periodic radial velocity variations. We consider only systems with periods longer than 10 days, where the motion is attributed to the presence of an ``extrasolar plane…
Analysis of the Hipparcos Observations of the Extrasolar Planets and the Brown Dwarf Candidates
Mazeh, Tsevi; Zucker, Shay
We analyzed the Hipparcos astrometric observations of 47 stars that were discovered to harbor giant planets and 14 stars with brown dwarf secondary candidates. The Hipparcos measurements were used together with the corresponding stellar radial velocity data to derive an astrometric orbit for each system. To find out the significance of the derived…
Interferometric Astrometry with Hubble Space Telescope Fine Guidance Sensor 3: The Parallax of the Cataclysmic Variable TV Columbae
McArthur, B. E.; Benedict, G. F.; Franz, O. G. +14 more
TV Col is a 13th magnitude intermediate polar cataclysmic variable with multiple periods found in the light curves. Past estimates predicted a distance of 400 pc to greater than 500 pc. Recently completed Hubble Space Telescope fine guidance sensor interferometric observations allow us to determine the first trigonometric parallax to TV Col. This …