Solar-like oscillations in HD 181420: data analysis of 156 days of CoRoT data

Context. The estimate of solar-like oscillation properties, such as their frequencies, amplitudes and lifetimes, is challenging because of their low amplitudes and will benefit from long and uninterrupted observing runs. The space telescope CoRoT allows us to obtain high-performance photometric data over a long and quasi continuous period. Among its main targets are stars for which we expect solar-like oscillations. Aims. HD 181420, an F2 main sequence star, has been observed by CoRoT during its first long run covering about 156 days. With this unprecedently high-quality set of data, our aim is to derive the p-mode parameters that can be used to probe the stellar interior. Methods. The CoRoT data obtained on HD 181420 is analysed using a classical Fourier approach for the search for the p mode signature. The p-mode parameters are then derived using global fitting of the power spectrum by a Lorentzian model, as used widely in the solar case. Results. From the p-mode frequencies, the mean value of the large spacing is estimated to be 75 ${\rm \mu Hz}$. The p-mode amplitudes are slightly less than 4 ppm with a line width of about 8 ${\rm \mu Hz}$ at the maximum of the p modes. The inclination angle is estimated to be around $45 \degr$. The large mode line-width combined with the observed mode spacing make it difficult to identify the $\ell=2$ modes and to estimate the rotational splitting. We explore two scenarios for the identification of the modes.