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Travis Metcalfe (NCAR) PowerPoint Presentation
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Travis Metcalfe (NCAR)

Travis Metcalfe (NCAR)

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Travis Metcalfe (NCAR)

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  1. First results from the Asteroseismic Modeling Portal Travis Metcalfe (NCAR) Collaborators: Michaël Bazot, Tim Bedding, Alfio Bonanno, Isa Brandão, Bill Chaplin, Jørgen Christensen-Dalsgaard, Orlagh Creevey, Maria Pia Di Mauro, Gülnur Dogan, Savita Mathur, Matthew Woitaszek, KASC WG1

  2. Drinking from a Firehose

  3. Ghost in the Machine • Stellar evolution tracks from ASTEC, pulsation analysis with ADIPLS • Parallel genetic algorithm optimizes globally, local analysis + SVD for errors • Stellar age from match to large separation, correct surface effects empirically 0.75 < M< 1.75 0.002 < Z< 0.05 0.22 < Y< 0.32 1.0 <a< 3.0 Metcalfe et al. (2009)

  4. Fitting for stellar age • Large frequency spacing <Dn> decreases almost monotonically with age • Binary decision tree to fit age from the observed large frequency spacing • Calculates only radial modes until final step, scales surface effects Christensen-Dalsgaard (2004)

  5. Correcting for surface effects • Incomplete modeling of surface convection zone leads to systematic errors • Calibrated with difference between fit to “Model S” and BiSON radial modes • Global fit to BiSON data, including scaled empirical correction for all modes

  6. Results from Sun-as-a-star data • Fit to 36 frequencies with l= 0-2 and constraints on temperature, luminosity • GA matches observed oscillation frequencies to better than about +2% • Temperature and age within +0.1%, luminosity and radius within +0.4%

  7. What is AMP? • Web interface to specify observations with errors, or upload as a text file • Specify parameter values to run one instance of the model, results archived • Source code available for those with access to large cluster or supercomputer http://amp.ucar.edu/ Woitaszek et al. (2009)

  8. How does AMP work? 128-way parallel 0.5-2.0 sets/week

  9. a Cen A & B Data: de Meulenaer et al. (2010), Kjeldsen et al. (2005)

  10. b Hyi & t Cet Data: Brandao et al. (2011), Teixeira et al. (2009)

  11. Gemma & KOI-975 Data: Chaplin et al. (2010), Howell et al. (2011)

  12. Overview & Future • AMP works: objective global stellar modeling for theorists and observers. Reliable spectroscopy is essential, and conflicts are generally obvious. • Dirt under the rug: some data sets do not yield satisfactory fits (c2 ~25). Why? Problems with the data (e.g. mode identification), deficiencies in the models (e.g. missing ingredients) or both. • Future validation: remaining ground-based data, dozens of Kepler targets, a few CoRoT stars.