MESA meets MURaM

Surface effects in main-sequence solar-like oscillators computed using three-dimensional radiation hydrodynamics simulations

W. H. Ball, B. Beeck, R. H. Cameron, Laurent Gizon

    Research output: Contribution to journalArticle

    Abstract

    Context. Space-based observations of solar-like oscillators have identified large numbers of stars in which many individual mode frequencies can be precisely measured. However, current stellar models predict oscillation frequencies that are systematically affected by simplified modelling of the near-surface layers. Aims. We use three-dimensional radiation hydrodynamics simulations to better model the near-surface equilibrium structure of dwarfs with spectral types F3, G2, K0 and K5, and examine the differences between oscillation mode frequencies computed in stellar models with and without the improved near-surface equilibrium structure. Methods. We precisely match stellar models to the simulations' gravities and effective temperatures at the surface, and to the temporally- and horizontally-averaged densities and pressures at their deepest points. We then replace the near-surface structure with that of the averaged simulation and compute the change in the oscillation mode frequencies. We also fit the differences using several parametric models currently available in the literature. Results. The surface effect in the stars of solar-type and later is qualitatively similar and changes steadily with decreasing effective temperature. In particular, the point of greatest frequency difference decreases slightly as a fraction of the acoustic cut-off frequency and the overall scale of the surface effect decreases. The surface effect in the hot, F3-type star follows the same trend in scale (i.e. it is larger in magnitude) but shows a different overall variation with mode frequency. We find that a two-term fit using the cube and inverse of the frequency divided by the mode inertia is best able to reproduce the surface terms across all four spectral types, although the scaled solar term and a modified Lorentzian function also match the three cooler simulations reasonably well. Conclusions. Three-dimensional radiation hydrodynamics simulations of near-surface convection can be averaged and combined with stellar structure models to better predict oscillation mode frequencies in solar-like oscillators. Our simplified results suggest that the surface effect is generally larger in hotter stars (and correspondingly smaller in cooler stars) and of similar shape in stars of solar type and cooler. However, we cannot presently predict whether this will remain so when other components of the surface effect are included.

    Original languageEnglish (US)
    Article numberA159
    JournalAstronomy and Astrophysics
    Volume592
    DOIs
    StatePublished - Aug 1 2016

    Fingerprint

    hydrodynamics
    oscillators
    radiation
    simulation
    stellar models
    oscillation
    stars
    coolers
    oscillations
    effect
    stellar structure
    hot stars
    inertia
    surface layer
    acoustics
    surface layers
    temperature
    convection
    cut-off
    gravity

    Keywords

    • Asteroseismology
    • Stars: oscillations

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    MESA meets MURaM : Surface effects in main-sequence solar-like oscillators computed using three-dimensional radiation hydrodynamics simulations. / Ball, W. H.; Beeck, B.; Cameron, R. H.; Gizon, Laurent.

    In: Astronomy and Astrophysics, Vol. 592, A159, 01.08.2016.

    Research output: Contribution to journalArticle

    @article{88028848b2864e058628e772d464c0c2,
    title = "MESA meets MURaM: Surface effects in main-sequence solar-like oscillators computed using three-dimensional radiation hydrodynamics simulations",
    abstract = "Context. Space-based observations of solar-like oscillators have identified large numbers of stars in which many individual mode frequencies can be precisely measured. However, current stellar models predict oscillation frequencies that are systematically affected by simplified modelling of the near-surface layers. Aims. We use three-dimensional radiation hydrodynamics simulations to better model the near-surface equilibrium structure of dwarfs with spectral types F3, G2, K0 and K5, and examine the differences between oscillation mode frequencies computed in stellar models with and without the improved near-surface equilibrium structure. Methods. We precisely match stellar models to the simulations' gravities and effective temperatures at the surface, and to the temporally- and horizontally-averaged densities and pressures at their deepest points. We then replace the near-surface structure with that of the averaged simulation and compute the change in the oscillation mode frequencies. We also fit the differences using several parametric models currently available in the literature. Results. The surface effect in the stars of solar-type and later is qualitatively similar and changes steadily with decreasing effective temperature. In particular, the point of greatest frequency difference decreases slightly as a fraction of the acoustic cut-off frequency and the overall scale of the surface effect decreases. The surface effect in the hot, F3-type star follows the same trend in scale (i.e. it is larger in magnitude) but shows a different overall variation with mode frequency. We find that a two-term fit using the cube and inverse of the frequency divided by the mode inertia is best able to reproduce the surface terms across all four spectral types, although the scaled solar term and a modified Lorentzian function also match the three cooler simulations reasonably well. Conclusions. Three-dimensional radiation hydrodynamics simulations of near-surface convection can be averaged and combined with stellar structure models to better predict oscillation mode frequencies in solar-like oscillators. Our simplified results suggest that the surface effect is generally larger in hotter stars (and correspondingly smaller in cooler stars) and of similar shape in stars of solar type and cooler. However, we cannot presently predict whether this will remain so when other components of the surface effect are included.",
    keywords = "Asteroseismology, Stars: oscillations",
    author = "Ball, {W. H.} and B. Beeck and Cameron, {R. H.} and Laurent Gizon",
    year = "2016",
    month = "8",
    day = "1",
    doi = "10.1051/0004-6361/201628300",
    language = "English (US)",
    volume = "592",
    journal = "Astronomy and Astrophysics",
    issn = "0004-6361",
    publisher = "EDP Sciences",

    }

    TY - JOUR

    T1 - MESA meets MURaM

    T2 - Surface effects in main-sequence solar-like oscillators computed using three-dimensional radiation hydrodynamics simulations

    AU - Ball, W. H.

    AU - Beeck, B.

    AU - Cameron, R. H.

    AU - Gizon, Laurent

    PY - 2016/8/1

    Y1 - 2016/8/1

    N2 - Context. Space-based observations of solar-like oscillators have identified large numbers of stars in which many individual mode frequencies can be precisely measured. However, current stellar models predict oscillation frequencies that are systematically affected by simplified modelling of the near-surface layers. Aims. We use three-dimensional radiation hydrodynamics simulations to better model the near-surface equilibrium structure of dwarfs with spectral types F3, G2, K0 and K5, and examine the differences between oscillation mode frequencies computed in stellar models with and without the improved near-surface equilibrium structure. Methods. We precisely match stellar models to the simulations' gravities and effective temperatures at the surface, and to the temporally- and horizontally-averaged densities and pressures at their deepest points. We then replace the near-surface structure with that of the averaged simulation and compute the change in the oscillation mode frequencies. We also fit the differences using several parametric models currently available in the literature. Results. The surface effect in the stars of solar-type and later is qualitatively similar and changes steadily with decreasing effective temperature. In particular, the point of greatest frequency difference decreases slightly as a fraction of the acoustic cut-off frequency and the overall scale of the surface effect decreases. The surface effect in the hot, F3-type star follows the same trend in scale (i.e. it is larger in magnitude) but shows a different overall variation with mode frequency. We find that a two-term fit using the cube and inverse of the frequency divided by the mode inertia is best able to reproduce the surface terms across all four spectral types, although the scaled solar term and a modified Lorentzian function also match the three cooler simulations reasonably well. Conclusions. Three-dimensional radiation hydrodynamics simulations of near-surface convection can be averaged and combined with stellar structure models to better predict oscillation mode frequencies in solar-like oscillators. Our simplified results suggest that the surface effect is generally larger in hotter stars (and correspondingly smaller in cooler stars) and of similar shape in stars of solar type and cooler. However, we cannot presently predict whether this will remain so when other components of the surface effect are included.

    AB - Context. Space-based observations of solar-like oscillators have identified large numbers of stars in which many individual mode frequencies can be precisely measured. However, current stellar models predict oscillation frequencies that are systematically affected by simplified modelling of the near-surface layers. Aims. We use three-dimensional radiation hydrodynamics simulations to better model the near-surface equilibrium structure of dwarfs with spectral types F3, G2, K0 and K5, and examine the differences between oscillation mode frequencies computed in stellar models with and without the improved near-surface equilibrium structure. Methods. We precisely match stellar models to the simulations' gravities and effective temperatures at the surface, and to the temporally- and horizontally-averaged densities and pressures at their deepest points. We then replace the near-surface structure with that of the averaged simulation and compute the change in the oscillation mode frequencies. We also fit the differences using several parametric models currently available in the literature. Results. The surface effect in the stars of solar-type and later is qualitatively similar and changes steadily with decreasing effective temperature. In particular, the point of greatest frequency difference decreases slightly as a fraction of the acoustic cut-off frequency and the overall scale of the surface effect decreases. The surface effect in the hot, F3-type star follows the same trend in scale (i.e. it is larger in magnitude) but shows a different overall variation with mode frequency. We find that a two-term fit using the cube and inverse of the frequency divided by the mode inertia is best able to reproduce the surface terms across all four spectral types, although the scaled solar term and a modified Lorentzian function also match the three cooler simulations reasonably well. Conclusions. Three-dimensional radiation hydrodynamics simulations of near-surface convection can be averaged and combined with stellar structure models to better predict oscillation mode frequencies in solar-like oscillators. Our simplified results suggest that the surface effect is generally larger in hotter stars (and correspondingly smaller in cooler stars) and of similar shape in stars of solar type and cooler. However, we cannot presently predict whether this will remain so when other components of the surface effect are included.

    KW - Asteroseismology

    KW - Stars: oscillations

    UR - http://www.scopus.com/inward/record.url?scp=84984607306&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=84984607306&partnerID=8YFLogxK

    U2 - 10.1051/0004-6361/201628300

    DO - 10.1051/0004-6361/201628300

    M3 - Article

    VL - 592

    JO - Astronomy and Astrophysics

    JF - Astronomy and Astrophysics

    SN - 0004-6361

    M1 - A159

    ER -