Publications (31)
The radius discrepancy in low mass stars: single vs. binaries
F. Spada, P. Demarque, Y. -C. Kim +1
A long-standing issue in the theory of low mass stars is the discrepancy between predicted and observed radii and effective temperatures. In spite of the increasing availability of…
Li Abundances in Halo Stars: Testing Stellar Evolution Models and the Primordial Li Abundance
Brian Chaboyer, P. Demarque
A large number of stellar evolution models with [Fe/H] = -2.3 and -3.3 have been calculated in order to determine the primordial Li abundance and to test current stellar evolut…
Modeling Convective Core Overshoot and Diffusion in Procyon Constrained by Asteroseismic Data
D. B. Guenther, P. Demarque, M Gruberbauer
We compare evolved stellar models, which match Procyons mass and position in the HR diagram, to current ground-based asteroseismic observations. Diffusion of helium and metals alon…
ROTATION, DIFFUSION, AND OVERSHOOT IN THE SUN: EFFECTS ON THE OSCILLATION FREQUENCIES AND THE NEUTRINO FLUX
Brian Chaboyer, P. Demarque, D. B. Guenther +1
We have studied the importance of the combined effects of rotation, diffusion, and convective overshoot on the p-mode oscillation spectrum and the neutrino flux of the standard sol…
Asteroseismology of delta Scuti stars - a parameter study and application to seismology of FG Virginis
M. R. Templeton, S. Basu, P. Demarque
We assess the potential of asteroseismology for determining the fundamental properties of individual Scuti stars. We computed a grid of evolution and adiabatic pulsation model…
Simulating the outer layers of Procyon A: a comparison with the Sun
F. J. Robinson, P. Demarque, D. B. Guenther +2
Compared to the Sun, the atmospheric structure and convective flow in Procyon A exhibit the following characteristics: (1) the highly superadiabatic transition layer (SAL) is locat…
Globular Cluster Ages and the Formation of the Galactic Halo
Brian Chaboyer, P. Demarque, Ata Sarajedini
Main sequence turnoff magnitudes from the recent set of Yale isochrones (Chaboyer \ea 1995) have been combined with a variety of relations for the absolute magnitude of RR Lyr star…
Inclusion of turbulence in solar modeling
L. H. Li, F. J. Robinson, P. Demarque +2
The general consensus is that in order to reproduce the observed solar p-mode oscillation frequencies, turbulence should be included in solar models. However, until now there has n…
Testing intermediate-age stellar evolution models with VLT photometry of LMC clusters. I. The data
C. Gallart, M. Zoccali, G. Bertelli +6
This is the first of a series of three papers devoted to the calibration of a few parameters of crucial importance in the modeling of the evolution of intermediate-mass stars, with…
Testing intermediate-age stellar evolution models with VLT photometry of LMC clusters. II. Analysis with the Yale models
J. -H. Woo, C. Gallart, P. Demarque +2
We present an analysis of CMDs of three intermediate-age LMC clusters, namely NGC 2173, SL 556 and NGC 2155. The main goal of our project is to investigate the amount of convective…
Testing the entropy calibration of the radii of cool stars: models of alpha Centauri A and B
F. Spada, P. Demarque
We present models of alpha Centauri A and B implementing an entropy calibration of the mixing-length parameter alpha_MLT, recently developed and successfully applied to the Sun (Sp…
The Age Of Globular Clusters In Light Of Hipparcos: Resolving the Age Problem?
Brian Chaboyer, P. Demarque, Peter J. Kernan +1
We review five independent techniques which are used to set the distance scale to globular clusters, including subdwarf main sequence fitting utilizing the recent Hipparcos paralla…
Asteroseismology and interferometry of the red giant star epsilon Oph
A. Mazumdar, A. Merand, P. Demarque +16
The GIII red giant star epsilon Oph has been found to exhibit several modes of oscillation by the MOST mission. We interpret the observed frequencies of oscillation in terms of the…
Improved calibration of the radii of cool stars based on 3D simulations of convection: implications for the solar model
F. Spada, P. Demarque, S. Basu +1
Main sequence, solar-like stars (M < 1.5 Msun) have outer convective envelopes that are sufficiently thick to affect significantly their overall structure. The radii of these stars…
Stellar Models with Microscopic Diffusion and Rotational Mixing I: Application to the Sun
Brian Chaboyer, P. Demarque, M. H. Pinsonneault
The Yale stellar evolution code has been modified to include the combined effects of diffusion and rotational mixing on H, He and the trace elements He, Li, Li,…
Short-Period Variables in the Local Group Dwarf Galaxies Tucana and LGS3
E. J. Bernard, M. Monelli, C. Gallart +16
We present preliminary results concerning the search for short-period variable stars in Tucana and LGS3 based on very deep HST/ACS imaging. In the fraction of the observed field we…
YREC: The Yale Rotating Stellar Evolution Code
P. Demarque, D. B. Guenther, L. H. Li +2
The stellar evolution code YREC is outlined with emphasis on its applications to helio- and asteroseismology. The procedure for calculating calibrated solar and stellar models is d…
Mass Loss On the Horizontal Branch: an Application to NGC6791
H. Yong, P. Demarque, S. Yi
The presence of a substantial number of hot stars in the extremely metal-rich} open cluster NGC6791 has been a mystery. If these hot stars are in their core helium burning phase, t…
Stellar Models with Microscopic Diffusion and Rotational Mixing II: Application to Open Clusters
Brian Chaboyer, P. Demarque, M. H. Pinsonneault
Stellar models with masses ranging from 0.5 to were constructed in order to compare to young cluster observations of Li and of rotation velocities. The amount of Li d…
The Yale-Potsdam Stellar Isochrones (YaPSI)
F. Spada, P. Demarque, Y. -C. Kim +2
We introduce the Yale-Potsdam Stellar Isochrones (YaPSI), a new grid of stellar evolution tracks and isochrones of solar-scaled composition. In an effort to improve the Yonsei-Yale…
The effect of turbulent pressure on the p-mode frequencies in stellar models
P. Demarque, L. H. Li, F. J. Robinson +4
We have constructed models for the sun at three stages of its evolution: a zero-age main sequence model, the present sun, and a subgiant model. For each model, the turbulent pressu…
A cgi synthetic CMD calculator for the YY Isochrones
P. Demarque, S. N. Virani, E. J. Murphy +3
We describe a web-based cgi calculator for constructing synthetic color-magnitude diagrams for a simple stellar population (SSP) using the Yonsei-Yale (YY) isochrone data base. Thi…
Radiative hydrodynamics in the highly super adiabatic layer of stellar evolution models
F. J. Robinson, P. Demarque, S. Sofia +3
We present results of three dimensional simulations of the uppermost part of the sun, at 3 stages of its evolution. Each model includes physically realistic radiative-hydrodynamics…
Solar-like oscillations in cluster stars
D. Stello, S. Basu, T. R. Bedding +21
We present a brief overview of the history of attempts to obtain a clear detection of solar-like oscillations in cluster stars, and discuss the results on the first clear detection…
Towards Better Age Estimates for Stellar Populations: The Y^2 Isochrones for Solar Mixture
S. Yi, P. Demarque, Y. -C. Kim +4
We have constructed a new set of isochrones, called the Y^2 Isochrones, that represent an update of the Revised Yale Isochrones (RYI), using improved opacities and equations of sta…
The Pulsation Properties of Procyon A
Brian Chaboyer, P. Demarque, D. B. Guenther
A grid of stellar evolution models for Procyon A has been calculated. These models include the best physics available to us (including the latest opacities and equation of state) a…
3D convection simulations of the outer layers of the Sun using realistic physics
F. J. Robinson, P. Demarque, L. H. Li +4
This paper describes a series of 3D simulations of shallow inefficient convection in the outer layers of the Sun. The computational domain is a closed box containing the convection…
2-D Stellar Evolution Code Including Arbitrary Magnetic Fields. I. Mathematical Techniques and Test Cases
L. H. Li, P. Ventura, S. Basu +2
A high-precision two-dimensional stellar evolution code has been developed for studying solar variability due to structural changes produced by varying internal magnetic fields of…
2D solar modeling
P. Ventura, V. Penza, L. Li +3
Understanding the reasons of the cyclic variation of the total solar irradiance is one of the most challenging targets of modern astrophysics. These studies prove to be essential a…
The Evolution of Procyon A
Brian Chaboyer, P. Demarque, D. B. Guenther
A grid of stellar evolution models for Procyon A has been calculated. These models include the best physics available to us (including the latest opacities and equation of state) a…
Ages of Galactic Globular Clusters from the New Yale Isochrones
Brian Chaboyer, P. Demarque, D. B. Guenther +2
A new grid of theoretical isochrones based on the Yale stellar evolution code using the OPAL and Kurucz opacities has been constructed. The grid of isochrones spans a wide range of…