Activity, rotation, and star-planet interaction of CoRoT-6

Modeling of the photospheric activity of the star and use the maps of the active regions to study stellar differential rotation and the star-planet interaction. Individual active regions have lifetimes up to 30-40 days. Most of them form and decay within five active longitudes whose different migration rates are attributed to the stellar differential rotation with a lower limit of ~0.12.

Associated publications

See also "Host stars"

Evidence for granulation in early A-type stars, Kallinger & Matthews (ApJ, 711, L35, 2010)

Stars with spectral types earlier than about F0 on (or close) to the main sequence have long been believed to lack observable surface convection, although evolutionary models of A-type stars do predict very thin surface convective zones. teh signature of granulation has been observed in two delta Scuti stars of spectral type A2 observed by CoRoT: HD 174936 (SRc01) and HD50844 (IRa01). Recent analyses of the data indicated up to some 1000 frequencies which were interpreted as individual pulsation modes. This interpretation requires a large number of nonradial modes of very high degree (l) but which should have very low amplitudes due to cancellation effects in disk-integrated photometry. An alternative model assumes that most of the peaks in the Fourier spectra are the signature of non-white granulation background noise, which leaves less than about 100 frequencies as candidates for stellar p-modes. This would be consistent with only low degree observable pulsation modes. Furthermore, the granulation time scales are consistent with scaling relations for cooler stars with known surface convection.

Associated publications

Very special system of two late B stars

The CoRoT lightcurve of HD 174884, a seismological target which was found to be an astrophysically important double-lined eclipsing binary in an eccentric orbit (e~0.3) and with a short (3.65705d) orbital period. The high eccentricity, coupled with the orientation of the binary orbit in space, explains the very unusual observed light curve with strongly unequal primary and secondary eclipses, having the depth ratio of 1-to-100 in the CoRoT "seismo" passband.
The analysis of the CoRoT photometry and the result of the spectroscopic follow-up program, provided a consistent picture of the system, composed of two late B stars and stringent constraints on the theoretical models. In particular it was evidenced the need of stellar models including rotation to recover the agreement between theory and observations.
The analysis of the light curve fit residuals evidences the presence of additional periodic variability other than that due to the orbit, and the Fourier decomposition yields two components, multiples of the orbital frequency, which are interpreted as tidally induced pulsations.

Associated publications

The young cluster NGC 2264 was observed with the Corot satellite for 23 days uninterruptedly in March 2008 with unprecedent photometric accuracy.
AA Tau-like light curves are found to be fairly common, with a frequency of at least ~ 30 to 40% in young stars with inner dusty disks. The temporal evolution of the light curves indicates that the structure of the inner disk warp, located close to the corotation radius and responsible for the obscuration episodes, varies over a timescale of a few (~1-3) rotational periods. This probably reflects the highly dynamical nature of the star-disk magnetospheric interaction.

Associated publications