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The WFC3 Galactic Bulge Treasury Program: A First Look at Resolved Stellar Population Tools
Thomas M. Brown, Kailash Sahu, Manuela Zoccali +12
[Abridged] When WFC3 is installed on HST, the community will have powerful new tools for investigating resolved stellar populations. The WFC3 Galactic Bulge Treasury program will o…
Fiducial Stellar Population Sequences for the u'g'r'i'z' System
James L. Clem, Don A. VandenBerg, Peter B. Stetson
We describe an extensive observational project that has obtained high-quality and homogeneous photometry for a number of different Galactic star clusters (including M 92, M 13, M 3…
On the Use of Blanketed Atmospheres as Boundary Conditions for Stellar Evolutionary Models
Don A. VandenBerg, Bengt Edvardsson, Kjell Eriksson +1
Stellar models have been computed for stars having [Fe/H] = 0.0 and -2.0 to determine the effects of using boundary conditions derived from the latest MARCS model atmospheres. The…
A Constraint on Z_\odot from Fits of Isochrones to the Color-Magnitude Diagram of M67
Don A. VandenBerg, Bengt Gustafsson, Bengt Edvardsson +2
The mass at which a transition is made between stars that have radiative or convective cores throughout the core H-burning phase is a fairly sensitive function of Z (particularly t…
On the Calibration of the Temperatures and Colors of Stellar Models for Lower Mass Stars
Don A. VandenBerg
The temperatures and colors of stellar models are much less secure than predicted luminosities; consequently, it is important to ensure that the models which are used to interpret…
The Victoria-Regina Stellar Models: Evolutionary Tracks and Isochrones for a Wide Range in Mass and Metallicity that Allow for Empirically Constrained Amounts of Convective Core Overshooting
Don A. VandenBerg, Peter A. Bergbusch, Patrick D. Dowler
Seventy-two grids of stellar evolutionary tracks, along with the capability to generate isochrones and luminosity/color functions from them, are presented in this investigation. Si…
Stellar Cluster Fiducial Sequences with the Advanced Camera for Surveys
Thomas M. Brown, Henry C. Ferguson, Ed Smith +6
We present color-magnitude diagrams of five Galactic globular clusters and one Galactic open cluster spanning a wide range of metallicity (-2.1 < [Fe/H] < +0.3), as observed in the…
A Star Catalog for the Open Cluster NGC188
Peter B. Stetson, Robert D. McClure, Don A. VandenBerg
We present new BVRI broad-band photometry for the old open cluster NGC188 based upon analysis of 299 CCD images either obtained by us, donated by colleagues, or retrieved from publ…
Models for Solar Abundance Stars with Gravitational Settling and Radiative Accelerations: Application to M67 and NGC188
G. Michaud, O. Richard, J. Richer +1
Evolutionary models taking into account radiative accelerations, thermal diffusion, and gravitational settling for 28 elements, including all those contributing to OPAL stellar opa…
Empirically Constrained Color-Temperature Relations. II. uvby
J. L. Clem, D. A. VandenBerg, F. Grundahl +1
(Abriged) A new grid of theoretical color indices for the Stromgren uvby photometric system has been derived from MARCS model atmospheres and SSG synthetic spectra for cool dwarf a…
The Age of the Oldest Stars in the Local Galactic Disk From Hipparcos Parallaxes of G and K Subgiants
A. Sandage, L. M. Lubin, D. A. VandenBerg
We review the history of the discovery of field subgiant stars and their importance in the age dating of the Galactic disk. We use the cataloged data from the Hipparcos satellite i…
Evidence for a Significant Intermediate-Age Population in the M31 Halo from Main Sequence Photometry
Thomas M. Brown, Henry C. Ferguson, Ed Smith +5
We present a color-magnitude diagram (CMD) for a minor-axis field in the halo of the Andromeda galaxy (M31), 51 arcmin (11 kpc) from the nucleus. These observations, taken with the…
Models of Metal Poor Stars with Gravitational Settling and Radiative Accelerations: I. Evolution and Abundance Anomalies
O. Richard, G. Michaud, J. Richer +3
Evolutionary models have been calculated for Pop II stars of 0.5 to 1.0 from the pre-main-sequence to the lower part of the giant branch. Rosseland opacities and radiative…
Str{ö}mgren Color-Temperature Relations for Cool Stars
James L. Clem, D. A. VandenBerg, F. Grundahl +1
A new extensive grid of synthetic Str{ö}mgren colors and bolometric corrections is presented for F-M type dwarf and giant stars having 3000K T 8000K, 0.0…
Models for Old, Metal-Poor Stars with Enhanced alpha-Element Abundances. III. Isochrones and Isochrone Population Functions
Peter A. Bergbusch, Don A. VandenBerg
An improved algorithm for interpolating isochrones and isochrone population functions (IPFs), based on the scheme introduced by Bergbusch & VandenBerg (1992, APJS, 81, 163), is des…
Exploring Star Clusters Using Stromgren uvby Photometry
F. Grundahl, D. A. VandenBerg, P. B. Stetson +3
We illustrate the application of high precision Stromgren uvby photometry to open and globular clusters (GCs). It is shown how such data can be used to determine cluster ages, inde…
Ages for Globular Clusters in the Outer Galactic Halo: The Second Parameter Clusters Palomar~3, Palomar~4 and Eridanus
Peter B. Stetson, Michael Bolte, William E. Harris +9
We have used the WFPC2 camera on the Hubble Space Telescope to obtain photometry of the outer-halo globular clusters Palomar 3, Palomar 4, and Eridanus. These three are classic exa…
The Open Cluster NGC 7789: II. CCD VI Photometry
Munhwan Gim, Don. A. VandenBerg, Peter B. Stetson +2
A (V,V - I)--diagram for the intermediate-age open cluster NGC 7789 has been derived from CCD observations of more than 15,000 stars within ~ 18 arcmin of the cluster center. From…
Stromgren Photometry of Globular Clusters: The Distance and Age of M13, Evidence For Two Populations of Horizontal-Branch Stars
Frank Grundahl, Don A. VandenBerg, Michael I. Andersen
We present deep CCD photometry of the globular cluster M13 (NGC 6205) in the Stromgren uvby-Beta system, and determine a foreground reddening of E(b-y)= 0.015mag. From a fit to the…
NGC 2419, M92, and the Age Gradient in the Galactic Halo
W. E. Harris, R. A. Bell, D. A. VandenBerg +7
The WFPC2 camera on HST has been used to obtain deep main sequence photometry of the low-metallicity ([Fe/H]=-2.14), outer-halo globular cluster NGC 2419. A differential fit of the…
Formation of the Milky Way
J. E. Hesser, P. B. Stetson, W. E. Harris +9
We review observational evidence bearing on the formation of a prototypical large spiral galaxy, the Milky Way. New ground- and space-based studies of globular star clusters and dw…
The Relative Ages of Galactic Globular Clusters
Peter B. Stetson, Don A. VandenBerg, Michael Bolte
We discuss the present state of knowledge and thought concerning the spread in age found among Galactic globular clusters, with some discussion of the implications for what happene…
Episodic Star Formation in the Carina dSph Galaxy
T. A. Smecker-Hane, P. B. Stetson, J. E. Hesser +1
We present photometry for stars in the Carina dwarf spheroidal galaxy that is unprecedented in depth, accuracy and spatial coverage. Our data demonstrate that Carina has had a surp…
Hubble Space Telescope Observations of White Dwarfs in the Globular Cluster M4
Harvey B. Richer, Gregory G. Fahlman, Rodrigo A. Ibata +9
With the Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope, we have discovered in M4 (NGC 6121, C 1620-264) the first extensive sequence of cooling white dwarfs s…