A new correction of stellar oscillation frequencies for near-surface effects

By W. Ball, Laurent Gizon. 2014

155 citations recorded by the source corpus.

Context. Space-based observations of solar-like oscillations present an opportunity to constrain stellar models using individual mode frequencies. However, current stellar models are inaccurate near the surface, which introduces a systematic di erence that must be corrected. Aims. We introduce and evaluate two parametrizations of the surface corrections based on formulae given by Gough (1990, LNP, 367, 283). The first we call a cubic term proportional to 3 =I and the second has an additional inverse term proportional to 1 =I, where andI are the frequency and inertia of an oscillation mode. Methods. We first show that these formulae accurately correct model frequencies of two di erent solar models (Model S and a calibrated MESA model) when compared to observed BiSON frequencies. In particular, even the cubic form alone fits significantly better than a power law. We then incorporate the parametrizations into a modelling pipeline that simultaneously fits the surface e ects and the underlying stellar model parameters. We apply this pipeline to synthetic observations of a Sun-like stellar model, solar observations degraded to typical asteroseismic uncertainties, and observations of the well-studied CoRoT target HD 52265. For comparison, we also run the pipeline with the scaled power-law correction proposed by Kjeldsen et al. (2008, ApJ, 683, L175). Results. The fits to synthetic and degraded solar data show that the method is unbiased and produces best-fit parameters that are consistent with the input models and known parameters of the Sun. Our results for HD 52265 are consistent with previous modelling e orts and the magnitude of the surface correction is similar to that of the Sun. The fit using a scaled power-law correction is significantly worse but yields consistent parameters, suggesting that HD 52265 is su ciently Sun-like for the same power-law to be applicable. Conclusions. We find that the cubic term alone is suitable for asteroseismic applications and it is easy to implement in an existing pipeline. It reproduces the frequency dependence of the surface correction better than a power-law fit, both when comparing calibrated solar models to BiSON observations and when fitting stellar models using the individual frequencies. This parametrization is thus a useful new way to correct model frequencies so that observations of individual mode frequencies can be exploited.

Subfields: Astronomy and Astrophysics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/c40a13bbc5ccea1af3b6514024631e75ff844034

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In Astronomy and Astrophysics

1. D. Huber
2. Matteo Cantiello
3. B. Paxton
4. W. Chaplin
5. T. Bedding
6. A. Miglio
7. P. Marchant
8. J. Fuller

In Statistical and Nonlinear Physics

1. B. Paxton
2. R. Townsend
3. Matteo Cantiello
4. D. Huber
5. Dean M. Townsley
6. P. Marchant
7. W. Ball
8. R. Farmer

Citations in the corpus

• Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic LEGACY Sample. II. Radii, Masses, and Ages (2016, methodology): “The free adjustable parameters to find the best-fitting 6 model were age, initial metallicity, initial helium, the mixing-length, the overshooting efficiency, and the two terms in the Ball & Gizon (2014) surface correction.”
• MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA): BINARIES, PULSATIONS, AND EXPLOSIONS (2015, methodology): “…using the downhill simplex algorithm rather than the Hooke-Jeeves algorithm; oscillation frequencies are calculated using GYRE rather than ADIPLS; and the surface corrections to frequencies are evaluated using equation 4 of Ball & Gizon (2014) rather than with the Kjeldsen et al. (2008) scheme.”
• Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic LEGACY Sample. I. Oscillation Mode Parameters (2016, unknown): “…ratios are useful for model fitting, where they can be used instead of individual frequencies (Lebreton & Goupil 2014; Silva Aguirre et al. 2015) because they are largely insensitive to the stellar surface layers (Kjeldsen et al. 2008a; Ball & Gizon 2014; Roxburgh 2015; Ball et al. 2016).”