Query : 2017A&A...600A.128B

2017A&A...600A.128B - Astronomy and Astrophysics, volume 600A, 128-128 (2017/4-1)

Surface-effect corrections for oscillation frequencies of evolved stars.


Abstract (from CDS):

Context. Accurate modelling of solar-like oscillators requires that modelled mode frequencies are corrected for the systematic shift caused by improper modelling of the near-surface layers, known as the surface effect. Several parametrizations of the surface effect are now available but they have not yet been systematically compared with observations of stars showing modes with mixed g- and p-mode character.
Aims. We investigate how much additional uncertainty is introduced to stellar model parameters by our uncertainty about the functional form of the surface effect. At the same time, we test whether any of the parametrizations is significantly better or worse at modelling observed subgiants and low-luminosity red giants.
Methods. We model six stars observed by Kepler that show clear mixed modes. We fix the input physics of the stellar models and vary the choice of surface correction between five parametrizations.
Results. Models using a solar-calibrated power law correction consistently fit the observations more poorly than the other four corrections. Models with the remaining four corrections generally fit the observations about equally well, with the combined surface correction by Ball & Gizon perhaps being marginally superior. The fits broadly agree on the model parameters within about the 2σ uncertainties, with discrepancies between the modified Lorentzian and free power law corrections occasionally exceeding the 3σ level. Relative to the best-fitting values, the total uncertainties on the masses, radii and ages of the stars are all less than 2, 1 and 6 per cent, respectively.
Conclusions. A solar-calibrated power law, as formulated by Kjeldsen et al. (2008ApJ...683L.175K), appears unsuitable for use with more evolved solar-like oscillators. Among the remaining surface corrections, the uncertainty in the model parameters introduced by the surface effects is about twice as large as the uncertainty in the individual fits for these six stars. Though the fits are thus somewhat less certain because of our uncertainty of how to manage the surface effect, these results also demonstrate that it is feasible to model the individual mode frequencies of subgiants and low-luminosity red giants, and hence also use these individual stars to help to constrain stellar models.

Abstract Copyright: © ESO, 2017

Journal keyword(s): asteroseismology - stars: oscillations - stars: oscillations

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 HD 52265 PM* 07 00 18.0357152121 -05 22 01.778490073   6.845 6.282     G0V 301 1
2 2MASS J18441281+4332024 RG* 18 44 12.8098541028 +43 32 02.365801764   10.756 9.676 9.465   K1IV 31 0
3 TYC 3541-1117-1 RG* 18 59 09.8408917479 +46 17 05.702397367   11.99 10.99     ~ 20 0
4 TYC 3124-433-1 * 19 04 54.5386095429 +40 55 39.842039550   12.59 11.36     K2 20 0
5 TYC 3555-1403-1 * 19 20 52.7237209312 +51 28 18.245887116   10.68 9.78     K0III-IV 31 0
6 HD 182736 Er* 19 24 03.3794425774 +44 56 00.735214599   7.82 7.01     G8IV 66 0
7 BD+44 3244 * 19 46 17.8467474629 +44 49 39.612542675   10.24 9.51     G5IV-V 37 0

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