Grid-based seismic modelling at high and low signal-to-noise ratios

Abstract

Context. Recently, the CoRoT target HD 175272 (F5V), which shows a weak signal of solar-like oscillations, was modelled by a differential asteroseismic analysis (Ozel et al. 2013, A&A, 558, A79) relative to a seismically similar star, HD 181420 (F2V), for which there is a clear signature of solar-like oscillations. The results provided by Ozel et al. indicate the possibility of HD 175272 having subsolar mass, while being of the order of 1000 K hotter than the Sun. This seems unphysical -standard stellar evolution theory generally does not predict solar-metallicity stars of subsolar mass to be hotter than about 6000 K -and calls for a reanalysis of this star. Aims. We aim to compare the performance of differential asteroseismic analysis with that of grid-based modelling. Methods. We use two sets of stellar model grids and two grid-fitting methods to model HD 175272 and HD 181420 using their effective temperatures, metallicities, large frequency separations (Δν), and frequencies of maximum oscillation power (ν max ) as observational constraints.Results. We find that we are able to model both stars with parameters that are both mutually compatible and comparable with other modelling efforts. Hence, with modest spectroscopic and asteroseismic inputs, we obtain reasonable estimates of stellar parameters. In the case of HD 175272, the uncertainties of the stellar parameters from our grid-based modelling are smaller, and hence more physical, than those reported in the differential analysis. For both stars, the models have significantly lower values of ν max than the reported observed values. Furthermore, when using the asymptotic large frequency separation as opposed to the scaling relation to compute Δν, we find that our modelling results are significantly more self-consistent when ν max is ignored. Conclusions. Grid-based modelling is a useful tool even in cases of weak solar-like oscillations. It provides more precise and more realistic results than obtained with differential seismology. The difference in the observed and modelled values of ν max indicates that the four observational constraints are not fully consistent with the stellar models used here, with ν max most likely to be the inconsistent constraint for these two stars.

Convective boundary mixing in low- and intermediate-mass stars – I. Core properties from pressure-mode asteroseismology

“…The supplementary star-by-star analysis of CoRoT and RV targets makes reference to the following work not cited in the main manuscript: 2000), Gizon et al (2013), Grevesse & Sauval (1998), Grevesse & Noels (1993), Hekker & Ball (2014), Høg et al (2000), Joyce & Chaboyer (2018), Kallinger et al (2010), Lebreton & Goupil (2012), Liebert et al (2013), Metcalfe et al (2009), Skrutskie et al (2006 and Thévenin et al (2006).…”

Asteroseismology of main-sequence F stars with Kepler: overcoming short mode lifetimes

“…For HD 181420, the underlying frequencies (see Barban et al 2009;Gaulme et al 2009) performed better than the ridge centroid frequencies with the Compton et al (2018) approach. The ridge centroid method produces a slightly underestimated stellar mass with a large uncertainty (1.27 ± 0.07 M ) compared to other independent analyses (1.3 -1.45 M , see Hekker & Ball 2014). Additionally, the magnitude of the relative surface correction at ν max is more reasonable from the individual mode frequencies ((−4.2 ± 3.3) · 10 −3 ) than the ridge centroid frequencies ((3.8 ± 3.2) · 10 −3 ), primarily because the former is negative.…”

“…Kallinger et al 2010;Salabert et al 2011;Mazumdar et al 2012;Liu et al 2014). HD 181420 has also been studied a number of times (see Barban et al 2009;Gaulme et al 2009;Ozel et al 2013;Hekker & Ball 2014). For the analysis of HD 181420, neither scenario was clearly preferred based on the fit of the models to the observed data.…”

Weighing stars from birth to death: mass determination methods across the HRD

“…In analogy with the more traditional stellar modelling by isochrone fitting techniques (Sect. 5.3), several asteroseismic GBM pipelines have been developed relying on Monte Carlo (Stello et al 2009;Basu et al 2012;Hekker and Ball 2014) and/or Bayesian methods (Kallinger et al 2010;Gruberbauer et al 2012;Silva Aguirre et al 2015;Serenelli et al 2017a;Rodrigues et al 2017;Lebreton and Reese 2020). The main difference with isochrone fitting techniques is that the likelihood function is computed using T eff , ½Fe/H, Dm and m max in this case.…”