Seismic and spectroscopic characterization of the solar-like pulsating CoRoT target HD 49385
Résumé
Context. The star HD 49385 is the first G-type solar-like pulsator observed in the seismology field of the space telescope CoRoT. The satellite collected 137 days of high-precision photometric data on this star, confirming that it presents solar-like oscillations. HD 49385 was also observed in spectroscopy with the NARVAL spectrograph in January 2009.
Aims: Our goal is to characterize HD 49385 using both spectroscopic and seismic data.
Methods: The fundamental stellar parameters of HD 49385 are derived with the semi-automatic software VWA, and the projected rotational velocity is estimated by fitting synthetic profiles to isolated lines in the observed spectrum. A maximum likelihood estimation is used to determine the parameters of the observed p modes. We perform a global fit, in which modes are fitted simultaneously over nine radial orders, with degrees ranging from l = 0 to l = 3 (36 individual modes).
Results: Precise estimates of the atmospheric parameters (Teff, [M/H], log g) and of the nu sin i of HD 49385 are obtained. The seismic analysis of the star leads to a clear identification of the modes for degrees l = 0,1,2. Around the maximum of the signal (nu ~= 1013 muHz), some peaks are found significant and compatible with the expected characteristics of l = 3 modes. Our fit yields robust estimates of the frequencies, linewidths and amplitudes of the modes. We find amplitudes of ~5.6 ± 0.8 ppm for radial modes at the maximum of the signal. The lifetimes of the modes range from one day (at high frequency) to a bit more than two days (at low frequency). Significant peaks are found outside the identified ridges and are fitted. They are attributed to mixed modes.
Aims: Our goal is to characterize HD 49385 using both spectroscopic and seismic data.
Methods: The fundamental stellar parameters of HD 49385 are derived with the semi-automatic software VWA, and the projected rotational velocity is estimated by fitting synthetic profiles to isolated lines in the observed spectrum. A maximum likelihood estimation is used to determine the parameters of the observed p modes. We perform a global fit, in which modes are fitted simultaneously over nine radial orders, with degrees ranging from l = 0 to l = 3 (36 individual modes).
Results: Precise estimates of the atmospheric parameters (Teff, [M/H], log g) and of the nu sin i of HD 49385 are obtained. The seismic analysis of the star leads to a clear identification of the modes for degrees l = 0,1,2. Around the maximum of the signal (nu ~= 1013 muHz), some peaks are found significant and compatible with the expected characteristics of l = 3 modes. Our fit yields robust estimates of the frequencies, linewidths and amplitudes of the modes. We find amplitudes of ~5.6 ± 0.8 ppm for radial modes at the maximum of the signal. The lifetimes of the modes range from one day (at high frequency) to a bit more than two days (at low frequency). Significant peaks are found outside the identified ridges and are fitted. They are attributed to mixed modes.