Differential asteroseismic study of seismic twins observed by CoRoT

Abstract

Context. The CoRoT short asteroseismic runs give us the opportunity to observe a large variety of late-type stars through their solarlike oscillations. We report the observation and modeling of the F5V star HD 175272. Aims. Our aim is to define a method for extracting as much information as possible from a noisy oscillation spectrum. Methods. We followed a differential approach that consists of using a well-known star as a reference to characterize another star. We used classical tools such as the envelope autocorrelation function to derive the global seismic parameters of the star. We compared HD 175272 with HD 181420 through a linear approach, because they appear to be asteroseismic twins. Results. The comparison with the reference star enables us to substantially enhance the scientific output for HD 175272. First, we determined its global characteristics through a detailed seismic analysis of HD 181420. Second, with our differential approach, we measured the difference of mass, radius and age between HD 175272 and HD 181420. Conclusions. We have developed a general method able to derive asteroseismic constraints on a star even in case of low-quality data. This method can be applied to stars with interesting properties but low signal-to-noise ratio oscillation spectrum, such as stars hosting an exoplanet or members of a binary system.

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

“…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.…”

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

“…Comparisons with 40 independently-derived radii and surface gravities have shown Table 1. Observed parameters of HD 181420 (F2V) and HD 175272 (F5V) taken from Ozel et al (2013 Miglio et al 2012). Secondly, the ∆ν scaling relation is derived in the asymptotic regime where the radial order n is much larger than the degree l, i.e.…”

“…Recently, Ozel et al (2013) proposed to derive stellar param-60 eters for a star with a weak oscillation signal by computing linear differences with respect to the stellar parameters in a second star with a strong oscillation signal and similar observable parameters (e.g. ∆ν, ν max , T eff , [Fe/H]).…”

“…∆ν, ν max , T eff , [Fe/H]). Ozel et al (2013) referred to this method as differential seismology and applied it to the seismically similar stars HD 175272 (F5V) and HD 181420 (F2V) (Bruntt 2009;Barban et al 2009;Huber et al 2012) using CE-SAM models. HD 175272 was observed by CoRoT for 27 days and shows oscillations at a low signal-to-noise ratio.…”

“…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.…”