Red giant STARS are often used as a diagnostic of galactic histories because they are bright, plentiful in all galaxies regardless of current star formation rate, and particularly visible in…

This is a $405,459.00 grant awarded by NASA to the University of Florida for research related to improving models of red giant stars. The research aims to:

1. Identify discrepancies between published red giant star models and observational data, and provide tools to estimate uncertainties in age estimates from these models.

2. Use the open-source MESA stellar evolution code to explore how uncertainties in stellar physics impact common red giant diagnostics.

3. Generate calibrated, publicly available red giant star models that are more consistent with observational data than current models.

This work is intended to support NASA's studies of galaxy formation and evolution using observations from the upcoming James Webb Space Telescope mission. The grant does not have a set-aside designation, and the University of Florida is the sole awardee. This award leverages UF's expertise in astrophysics research and its capabilities in supporting NASA and other federal agencies through contracts and grants.

Red giant STARS are often used as a diagnostic of galactic histories because they are bright, plentiful in all galaxies regardless of current star formation rate, and particularly visible in wavelengths not obscured by dust. In the future, NASA s jwst mission intends to expand these studies of how galaxies form and evolve to a wider range of galaxies across cosmic time. However, all of this work relies on accurate models of red giant STARS that can convert the observed light into estimates of compositions and ages. Unfortunately, work by NASA s kepler, K2, and now tess missions studying STARS in the nearby universe have demonstrated that current models of red giant STARS are significantly offset from reality. Using a combination of asteroseismic masses and radii as well as ground-based spectroscopy, fundamental parameters are now available for thousands of red giant STARS. Preliminary work comparing these results to model predictions has demonstrated that these offsets between models and data are age and metallicity dependent, which raises concerns for future extrapolations of these models to lower metallicity galaxies earlier in cosmic time as well as our ability to accurately estimate ages for even the most well studied STARS. We therefore propose to: - identify the current discrepancies between published grids of models, document these differences as a function of mass and metallicity, and provide an easy to use open source tool to estimate current uncertainties on the inferences of ages from observational data - leverage the existing open source stellar evolution code mesa to thoroughly explore how uncertainties in stellar physics cause variation in commonly used diagnostics such as the temperature of the giant branch, the location of the red clump, the luminosity of the red giant branch tip, the location of the red giant branch bump, and the chemical mixing at the first dredge up. - use currently available data to generate publicly available calibrated models that are significantly more consistent with the properties of real red giant STARS than any current models. These better models will then represent a tool for a wide variety of astrophysical studies to interpret data from our own milky way (kepler, K2, tess, spherex) and in other galaxies (HST, jwst) through data from both individual STARS and through stellar population synthesis.