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.
$405,459FY2022National Aeronautics and Space AdministrationNASA
University Of Florida, Gainesville FL