The Asteroseismology Program

CoRoT is performing an 'exploratory' program towards the detection and classification of stellar oscillations in a large variety of stars. The 'central' program is centered on the detailed observations of a few selected stars to study the hydrodynamics of a star's internal layers and the physical state of its nucleus.

The 'Exploratory' Program

Since CoRoT is the one of the first missions dedicated to asteroseismology, the exploratory program will determine the ranges of stellar parameters across which stellar oscillations can be detected; then the relations between the amplitudes of the oscillations will be studied, and their characteristics.

Although there are several theoretical predictions about the amplitude relations among the various oscillations caused by convective motions, there are many unknown aspects, especially the treatment of super-adiabatic layers and the amount of turbulent motions.

In consequence, one needs to observe a sample of objects with a large variety of stellar parameters, like mass, age, chemical composition, rotational state etc, where only a modest signal to noise ratio is needed. A frequency resolution of 0.5 microHz (that is, one period in about 20 days) will be sufficient, corresponding to observations that last 10-20 days. Stars with magnitudes of about 9 will be bright enough for these studies, which will allow the observations of several stars simultaneously in the same field of view.

About ten stars has been observed with a total observing time up to four months. COROT, together with Kepler,  are currently the only projects that allow to observe tens of stars simultaneously for asteroseismic data.

The 'Central' Program

This program is more ambitious for which it needs more time then the exploratory one. It is the second phase in the development of asteroseismology from space. A small sample of stars with a very high precision, which have been selected to have maximum diagnostic value, are being observed. For the selection of these stars the results from the exploratory program are taken into account.

Being based on the case of our Sun (the only star about which we have these data now), we require a precision of the frequencies to 0.1 microHz (1 period in about 100 days) to have access to the profile of the modes and the rotational divisions, and for a precise measurement for the modal frequencies.

For a star of 6th magnitude, the detection threshold will be below one part in a million. For stars slightly brighter then the Sun (Spectral class A and F), it will be possible to measure the size of the convective nucleus, the size of the external convective layers and their helium content. The rotational profile of Delta-Scuti stars may be measured as well. More than 10  stars have been already observed for 5 months each, with several more stars in the same field of view. This is allowing us to measure the age of the stars with a precision that might reach 0.1% !