---
res:
  bibo_abstract:
  - "Context. In the convective envelopes of relatively cool (surface temperature
    ≲6700 K) stars, oscillations are excited by turbulent convection. In these so-called
    solar-like oscillators, radial oscillation modes appear at nearly equally spaced
    frequencies. This spacing is referred to as the ‘large-frequency separation’.
    Deviations from equally spaced frequencies are a result of the internal structure
    of a star being different from a sphere of ideal gas at constant temperature.
    Hence, these deviations provide information on the internal structure of the star.\r\n\r\nAims.
    In this work, we investigate the second-order (quadratic) deviation from uniform
    spacing, referred to as curvature. We aim to provide homogeneous values for observed
    red-giant stars, understand differences between the results from observations
    and predictions from stellar models, and reveal the connection between curvature
    and stellar structure.\r\n\r\nMethods. We used Kepler data of red-giant stars
    and computed the curvature for several thousand stars. We compared these to the
    curvature derived from MESA models. We subsequently investigated the trends and
    differences between results from observations and models. Finally, we computed
    sensitivity kernels to identify the stellar region(s) to which the curvature is
    most sensitive and performed a glitch analysis.\r\n\r\nResults. We found that
    the curvature is sensitive to evolutionary phase and mass. Interestingly, the
    observed values and values from models show some discrepancies. Including the
    surface effect in the model frequencies reduces the discrepancies, though it introduces
    a frequency-dependent over- or under-estimation of the curvature from the models
    compared to the observations. From the kernels, we confirmed that the curvature
    is mostly sensitive to the near-surface layers of the star. The glitch analysis
    shows that in theory this provides information on the location and strength of
    the He I and H I ionisation layers.\r\n\r\nConclusions. The curvature provides
    a probe into the near-surface structure of the star. The deviations between the
    curvature derived from observations and models call for improvements in the near-surface
    layers of stellar models.@eng"
  bibo_authorlist:
  - foaf_Person:
      foaf_givenName: S.
      foaf_name: Hekker, S.
      foaf_surname: Hekker
  - foaf_Person:
      foaf_givenName: Y.
      foaf_name: Elsworth, Y.
      foaf_surname: Elsworth
  - foaf_Person:
      foaf_givenName: S.
      foaf_name: Basu, S.
      foaf_surname: Basu
  - foaf_Person:
      foaf_givenName: F.
      foaf_name: Ahlborn, F.
      foaf_surname: Ahlborn
  - foaf_Person:
      foaf_givenName: W. H.
      foaf_name: Ball, W. H.
      foaf_surname: Ball
  - foaf_Person:
      foaf_givenName: E. P.
      foaf_name: Bellinger, E. P.
      foaf_surname: Bellinger
  - foaf_Person:
      foaf_givenName: Lynn
      foaf_name: Buchele, Lynn
      foaf_surname: Buchele
      foaf_workInfoHomepage: http://www.librecat.org/personId=158c74c1-eed5-11ef-8c05-e45f52925cdc
  - foaf_Person:
      foaf_givenName: F.
      foaf_name: Espinoza-Rojas, F.
      foaf_surname: Espinoza-Rojas
  bibo_doi: 10.1051/0004-6361/202557690
  bibo_volume: 709
  dct_date: 2026^xs_gYear
  dct_isPartOf:
  - http://id.crossref.org/issn/0004-6361
  - http://id.crossref.org/issn/1432-0746
  dct_language: eng
  dct_publisher: EDP Sciences@
  dct_title: The sensitivity and behaviour of the curvature in the échelle diagram
    of red-giant stars@
...