GGrantIndex
← Search

ASTEROSEISMIC ANALYSES OF STARS OFTEN YIELD CONFLICTING SETS OF SOLUTIONS TO THE OBSERVATIONS. THE DICHOTOMIES ARISE FROM TENSIONS BETWEEN CLASSICAL OBSERVABLES SUCH AS PHOTOMETRY SPECTROSCOPY AND ABUNDANCE ANALYSIS VERSUS THE SEISMIC OBSERVABLES OF DOZENS OF P- AND G-MODE FREQUENCIES. THIS IN TURN IS A TENSION BETWEEN STELLAR ATMOSPHERE MODELS AND INTERIOR STRUCTURE MODELS. F-STARS AND SUB-GIANTS SEEM MOST PRONE TO THIS BUT SUB-GIANTS THANKS TO THEIR MIXED G- AND P-MODES ALSO HAVE THE PROMISE OF SHOWING US STELLAR INTERIORS IN UNPRECEDENTED DETAIL. METHODS HAVE BEEN DEVELOPED TO RESOLVE SUCH CONFLICTS BUT ONLY DO SO BY INJECTING UNWANTED BIAS INTO THE ANALYSIS. THE PROPOSED PROJECT WILL INSTEAD ADDRESS THE ROOT CAUSE OF THE PROBLEM WHICH IS A CONFLICT BETWEEN THE MODELING OF CLASSIC AND SEISMIC OBSERVABLES. THE SOLAR ABUNDANCE PROBLEM POINTS TO THE SAME TENSION BETWEEN ATMOSPHERIC AND INTERIOR MODELS AND IS LIKELY TO ALSO APPLY TO OTHER STARS. ONE SOLUTION MADE MORE PROBABLE BY RECENT EXPERIMENTS ON IRON UNDER SOLAR CONDITIONS IS AN INCREASE OF INTERIOR OPACITY. THIS WILL BE ADDRESSED BY A NEW OPACITY CALCULATION BY A. PRADHAN'S GROUP AT OHIO STATE UNIV. (OUTSIDE THIS PROJECT) BASED ON A NEW EQUATION OF STATE BEING DEVELOPED BY THE PI. THESE WILL FORM THE ATOMIC PHYSICS FOUNDATION OF THE PROJECT PROPOSED HERE. THE ATMOSPHERIC STRUCTURE PRODUCING THE CLASSIC OBSERVABLES IS GREATLY AFFECTED BY THE 3D NATURE OF CONVECTION IN LATE-TYPE STARS. THE PROPOSED PROJECT WILL THEREFORE CENTER AROUND THE CALCULATION OF A NEW GRID OF REALISTIC 3D SIMULATIONS OF DEEP STELLAR ATMOSPHERES. IT WILL SPAN FROM M DWARFS TO EARLY A STARS ON THE MAIN SEQUENCE AND UP TO GIANTS WITH LOGG=0. THE GRID WILL INITIALLY SPAN METALLICITIES OF [FE/H] = [-1.0 -0.5 0.0 +0.2] WITH SOME ADDITIONAL SIMULATIONS TO EXPLORE DEPENDENCIES ON HELIUM CONTENT. THE GRID WILL EMPLOY THE NEW EQUATION OF STATE AND OPACITIES MENTIONED ABOVE AND A NUMBER OF IMPROVEMENTS TO THE HYDRODYNAMICS. WE WILL ALSO CHANGE THE FILE FORMAT TO MAKE THE FILES MORE IMMEDIATELY ACCESSIBLE AS WE PLAN TO GIVE THE COMMUNITY ACCESS TO THE FULL SIMULATION RESULTS AND SUPPORTING CODE. TO PERFORM ASTEROSEISMIC ANALYSIS THE ATMOSPHERE SIMULATIONS NEED TO BE CONNECTED WITH INTERIOR AND EVOLUTION MODELS. THESE MODELS WILL USE THE SAME NEW ATOMIC PHYSICS AS THE 3D ATMOSPHERES THE PHOTOSPHERIC TRANSITION RESULTING FROM THE 3D RADIATIVE TRANSFER IN THE CONVECTING SIMULATIONS THE CONVECTIVE EXPANSION OF THE ATMOSPHERE AND A MIXING-LENGTH PARAMETER THAT REPRODUCE THE BOTTOM OF THE SIMULATIONS. THE SEISMIC MODELING WILL BUILD ON THE PI'S CURRENT EFFORTS TO EVALUATE THE COMPONENTS OF THE ASTEROSEISMIC SURFACE EFFECT ARISING FROM DIRECT INTERACTIONS BETWEEN CONVECTION AND OSCILLATION MODES. THE RESULT WILL BE AN UNPRECEDENTED LEVEL OF CONSISTENCY AND QUALITY IN ALL THE STEPS OF THE MODELING AND AN ELIMINATION OF THE CLASSIC BREAK BETWEEN ATMOSPHERE AND INTERIOR MODELS. THE ASTEROSEISMIC MODELING PORTAL (AMP) BY TEAM-MEMBER T. METCALFE WILL COMBINE THESE CHANGES TO THE STELLAR STRUCTURE AND SEISMIC MODELING TO PERFORM SEARCHES FOR THE BEST FIT MODELS TO BOTH SEISMIC AND CLASSIC OBSERVATIONS OF STARS. THE RESULT WILL BE ROBUST AND UNAMBIGUOUS MATCHING THE QUALITY OF KEPLER AND K2 OBSERVATIONS. SUCH AN IMPROVED FOCUS OF KEPLER/K2 WILL ENABLE INVESTIGATIONS INTO MORE SUBTLE PHENOMENA AND POSSIBLY BREAK SOME OF THE CURRENT DEGENERACY BETWEEN STELLAR PARAMETERS WE TRY TO SOLVE FOR. OUR RESULTS WILL BE APPLIED TO A SAMPLE OF PARTICULARLY DIFFICULT OR INTERESTING KEPLER AND K2 TARGETS. OUR PROJECT WILL ADVANCE THE SCIENCE GOALS OF NASA'S ASTROPHYSICS PROGRAM AND IN PARTICULAR THAT OF THE K2 MISSION AND THE SOON TO BE LAUNCHED TESS MISSION. THE SAME PHYSICS APPLIES TO THE SUN AND WE WILL THEREFORE ALSO SUPPORT THE SCIENCE GOALS OF THE HELIOPHYSICS PROGRAM AND THE SOHO AND SDO MISSIONS.

$409,192FY2020National Aeronautics and Space AdministrationNASA

Space Science Institute, Boulder CO

Investigators

View source on USAspending →
ASTEROSEISMIC ANALYSES OF STARS OFTEN YIELD CONFLICTING SETS OF SOLUTIONS TO THE OBSERVATIONS. THE DICHOTOMIES ARISE FROM TENSIONS BETWEEN CLASSICAL OBSERVABLES SUCH AS PHOTOMETRY SPECTROSCOPY AND ABUNDANCE ANALYSIS VERSUS THE SEISMIC OBSERVABLES OF DOZENS OF P- AND G-MODE FREQUENCIES. THIS IN TURN IS A TENSION BETWEEN STELLAR ATMOSPHERE MODELS AND INTERIOR STRUCTURE MODELS. F-STARS AND SUB-GIANTS SEEM MOST PRONE TO THIS BUT SUB-GIANTS THANKS TO THEIR MIXED G- AND P-MODES ALSO HAVE THE PROMISE OF SHOWING US STELLAR INTERIORS IN UNPRECEDENTED DETAIL. METHODS HAVE BEEN DEVELOPED TO RESOLVE SUCH CONFLICTS BUT ONLY DO SO BY INJECTING UNWANTED BIAS INTO THE ANALYSIS. THE PROPOSED PROJECT WILL INSTEAD ADDRESS THE ROOT CAUSE OF THE PROBLEM WHICH IS A CONFLICT BETWEEN THE MODELING OF CLASSIC AND SEISMIC OBSERVABLES. THE SOLAR ABUNDANCE PROBLEM POINTS TO THE SAME TENSION BETWEEN ATMOSPHERIC AND INTERIOR MODELS AND IS LIKELY TO ALSO APPLY TO OTHER STARS. ONE SOLUTION MADE MORE PROBABLE BY RECENT EXPERIMENTS ON IRON UNDER SOLAR CONDITIONS IS AN INCREASE OF INTERIOR OPACITY. THIS WILL BE ADDRESSED BY A NEW OPACITY CALCULATION BY A. PRADHAN'S GROUP AT OHIO STATE UNIV. (OUTSIDE THIS PROJECT) BASED ON A NEW EQUATION OF STATE BEING DEVELOPED BY THE PI. THESE WILL FORM THE ATOMIC PHYSICS FOUNDATION OF THE PROJECT PROPOSED HERE. THE ATMOSPHERIC STRUCTURE PRODUCING THE CLASSIC OBSERVABLES IS GREATLY AFFECTED BY THE 3D NATURE OF CONVECTION IN LATE-TYPE STARS. THE PROPOSED PROJECT WILL THEREFORE CENTER AROUND THE CALCULATION OF A NEW GRID OF REALISTIC 3D SIMULATIONS OF DEEP STELLAR ATMOSPHERES. IT WILL SPAN FROM M DWARFS TO EARLY A STARS ON THE MAIN SEQUENCE AND UP TO GIANTS WITH LOGG=0. THE GRID WILL INITIALLY SPAN METALLICITIES OF [FE/H] = [-1.0 -0.5 0.0 +0.2] WITH SOME ADDITIONAL SIMULATIONS TO EXPLORE DEPENDENCIES ON HELIUM CONTENT. THE GRID WILL EMPLOY THE NEW EQUATION OF STATE AND OPACITIES MENTIONED ABOVE AND A NUMBER OF IMPROVEMENTS TO THE HYDRODYNAMICS. WE WILL ALSO CHANGE THE FILE FORMAT TO MAKE THE FILES MORE IMMEDIATELY ACCESSIBLE AS WE PLAN TO GIVE THE COMMUNITY ACCESS TO THE FULL SIMULATION RESULTS AND SUPPORTING CODE. TO PERFORM ASTEROSEISMIC ANALYSIS THE ATMOSPHERE SIMULATIONS NEED TO BE CONNECTED WITH INTERIOR AND EVOLUTION MODELS. THESE MODELS WILL USE THE SAME NEW ATOMIC PHYSICS AS THE 3D ATMOSPHERES THE PHOTOSPHERIC TRANSITION RESULTING FROM THE 3D RADIATIVE TRANSFER IN THE CONVECTING SIMULATIONS THE CONVECTIVE EXPANSION OF THE ATMOSPHERE AND A MIXING-LENGTH PARAMETER THAT REPRODUCE THE BOTTOM OF THE SIMULATIONS. THE SEISMIC MODELING WILL BUILD ON THE PI'S CURRENT EFFORTS TO EVALUATE THE COMPONENTS OF THE ASTEROSEISMIC SURFACE EFFECT ARISING FROM DIRECT INTERACTIONS BETWEEN CONVECTION AND OSCILLATION MODES. THE RESULT WILL BE AN UNPRECEDENTED LEVEL OF CONSISTENCY AND QUALITY IN ALL THE STEPS OF THE MODELING AND AN ELIMINATION OF THE CLASSIC BREAK BETWEEN ATMOSPHERE AND INTERIOR MODELS. THE ASTEROSEISMIC MODELING PORTAL (AMP) BY TEAM-MEMBER T. METCALFE WILL COMBINE THESE CHANGES TO THE STELLAR STRUCTURE AND SEISMIC MODELING TO PERFORM SEARCHES FOR THE BEST FIT MODELS TO BOTH SEISMIC AND CLASSIC OBSERVATIONS OF STARS. THE RESULT WILL BE ROBUST AND UNAMBIGUOUS MATCHING THE QUALITY OF KEPLER AND K2 OBSERVATIONS. SUCH AN IMPROVED FOCUS OF KEPLER/K2 WILL ENABLE INVESTIGATIONS INTO MORE SUBTLE PHENOMENA AND POSSIBLY BREAK SOME OF THE CURRENT DEGENERACY BETWEEN STELLAR PARAMETERS WE TRY TO SOLVE FOR. OUR RESULTS WILL BE APPLIED TO A SAMPLE OF PARTICULARLY DIFFICULT OR INTERESTING KEPLER AND K2 TARGETS. OUR PROJECT WILL ADVANCE THE SCIENCE GOALS OF NASA'S ASTROPHYSICS PROGRAM AND IN PARTICULAR THAT OF THE K2 MISSION AND THE SOON TO BE LAUNCHED TESS MISSION. THE SAME PHYSICS APPLIES TO THE SUN AND WE WILL THEREFORE ALSO SUPPORT THE SCIENCE GOALS OF THE HELIOPHYSICS PROGRAM AND THE SOHO AND SDO MISSIONS. · GrantIndex