Grid-based seismic modelling at high and low signal-to-noise ratios HD 181420 and HD 175272 [SSA]

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) 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. (2013) 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 6000K — 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. 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. Conclusions: Grid-based modelling provides more precise and more realistic results than obtained with differential seismology.

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S. Hekker and W. Ball
Mon, 17 Mar 14