Geneva Stellar Models

Geneva Stellar Models
Name	Geneva Stellar Models
Institution	University of Geneva
Principal investigators	André Maeder, Georges Meynet, Sylvie Ekström
First release	1970s
Languages	Fortran
Field	Astrophysics, Stellar astrophysics, Computational physics
Website	Geneva Observatory

Geneva Stellar Models

The Geneva Stellar Models are a suite of theoretical stellar evolution calculations developed at the University of Geneva by teams including André Maeder, Georges Meynet, and collaborators. They provide evolutionary tracks and isochrones used by researchers studying star clusters, galactic evolution, supernovae, and extragalactic astronomy. The project integrates observational constraints from facilities like the Hubble Space Telescope, the European Southern Observatory, and the Very Large Telescope to inform prescriptions for rotation, mass loss, and nucleosynthesis.

Overview

Geneva models compute the internal structure and surface properties of stars across masses and metallicities, producing outputs for luminosity, effective temperature, surface abundances, and angular momentum. They are applied to interpret data from surveys such as Gaia, Sloan Digital Sky Survey, Kepler, and TESS and to compare against spectroscopic analyses from instruments on Very Large Telescope and Subaru Telescope. The models have informed interpretations of phenomena observed in environments ranging from the Small Magellanic Cloud and Large Magellanic Cloud to the Milky Way bulge and globular cluster systems.

History and Development

Development began at the Geneva Observatory in the 1970s, building on earlier stellar structure work by researchers linked to institutions such as Institut d'Astrophysique de Paris and Observatoire de Paris. Key advances were introduced in successive decades: inclusion of improved opacities from collaborations with teams tied to Los Alamos National Laboratory and Lawrence Livermore National Laboratory; convection treatments influenced by work at Princeton University and Cambridge University; and updated nuclear reaction rates from laboratories like Brookhaven National Laboratory and TRIUMF. The 1990s and 2000s saw major revisions with rotationally-induced mixing pioneered by investigators connected to ETH Zurich and Max Planck Institute for Astrophysics. Recent updates have incorporated constraints from missions such as Hipparcos and Gaia.

Physical Inputs and Assumptions

Geneva computations adopt microphysics inputs—equations of state, radiative opacities, and nuclear reaction networks—sourced from collaborations with groups at Los Alamos National Laboratory, Lawrence Livermore National Laboratory, NIST, and CERN. Convective transport uses prescriptions developed in dialogue with research at University of Cambridge and Princeton University, while rotational mixing incorporates angular momentum transport concepts paralleling results from Max Planck Institute for Astrophysics and Harvard-Smithsonian Center for Astrophysics. Mass-loss rates are tied to empirical studies from teams at Observatoire de Paris and California Institute of Technology and to theoretical winds from groups at University of Colorado Boulder. Opacity tables reference work by collaborations that include CEA Saclay and Ohio State University.

Model Grids and Parameters

The model grids span initial masses from low-mass stars relevant to globular cluster populations up to very massive stars tied to Wolf–Rayet star progenitors, and metallicities spanning values characteristic of the Small Magellanic Cloud, Large Magellanic Cloud, and solar neighborhood. Grids include rotating and non-rotating sequences with parameters chosen to match observational surveys such as VLT-FLAMES and Gaia-ESO Survey. Outputs are provided as evolutionary tracks, isochrones, and surface abundance predictions compatible with tools used by researchers at Max Planck Institute for Astronomy, University of Cambridge, Harvard University, and California Institute of Technology.

Key Predictions and Applications

Geneva tracks predict lifetimes, chemical yields, and pre-supernova structures that feed into simulations at institutions like Institute for Advanced Study and Lawrence Berkeley National Laboratory. They have been used to interpret the progenitors of core-collapse supernovae observed by teams at Palomar Observatory and Keck Observatory, to model the integrated light of stellar populations for extragalactic studies by groups at Space Telescope Science Institute and University College London, and to predict rotational velocity distributions compared with surveys run by European Southern Observatory and ESO-MUSE. The models inform nucleosynthetic yield tables employed in galactic chemical evolution codes developed at University of Cambridge, Max Planck Institute for Astrophysics, and University of Tokyo.

Comparisons with Other Stellar Evolution Codes

Geneva outputs are routinely compared with results from codes developed by teams at California Institute of Technology (e.g., Modules for Experiments in Stellar Astrophysics collaborators), Padova Observatory/Trieste Astronomical Observatory isochrones, the MESA community centered on University of California, Santa Barbara, and models from Bonn University and Monash University. Comparative studies benchmark treatments of rotation against work from Max Planck Institute for Astrophysics and mass-loss prescriptions against results from Princeton University and University of Michigan. Such comparisons guide cross-calibration used by consortia including the European Space Agency and the National Aeronautics and Space Administration.

Limitations and Uncertainties

Uncertainties arise from inputs tied to experiments at Brookhaven National Laboratory and Lawrence Livermore National Laboratory (nuclear rates), opacity determinations linked to CEA Saclay, and prescriptions for angular momentum transport debated in literature from Max Planck Institute for Astrophysics and Harvard-Smithsonian Center for Astrophysics. Treatment of magnetic fields, multi-dimensional convection, and binary interactions remains less developed compared with efforts at MPI für Astrophysik teams and binary evolution groups at Radboud University Nijmegen and University of Basel. Observational calibration using datasets from Gaia, Hubble Space Telescope, and Keck Observatory continually refines model inputs but residual systematic uncertainties affect age and yield inferences for studies led by Institute of Astronomy, Cambridge and Steward Observatory.

Category:Stellar evolution