Multi-color photometry with SOFIA: Spots on the solar-like star CoRoT-2A and their effect on its exoplanet CoRoT-2b

• Applicant: Dr. Klaus Felix Huber
• Subject Area: Astrophysics and Astronomy
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 239961424

My collaborators and I will observe one transit of the exoplanet CoRoT-2b in front of its very active host-star CoRoT-2A. For the first time we will be able to obtain quasi-space-based, short-cadence photometry in the optical and the near-infrared simultaneously for an uninterrupted time period of more than 3 hours. The SOFIA data will provide us with the information necessary to investigate two issues:(a) Are exoplanetary radii inflated?Current research shows that many Jupiter-like exoplanets have radii much larger than theoretical predictions. Using CoRoT data our group has already shown that the activity of the host-star causes systematic errors in the determination of planetary parameters, i.e., the planet radius. Our SOFIA observations will allow us to examine how much of the planet's inflated radius is caused by starspots on the stellar surface. The result will help us to understand whether the observed inflation really is due to an yet not understood physical process expanding the planet or some consequence of stellar activity affecting the lightcurves.(b) What are the physical properties of starspots?Lightcurves can be used to reconstruct dark spots on the surface of a star. For this task, transiting planets are of special interest: When the planet moves across the stellar disk, it scans the surface of the star and all brightness inhomogeneities are imprinted onto the profile of the transit. Our group has already used this method to reconstruct the surface evolution of CoRoT-2A over a time period of almost half a year using the data of the CoRoT satellite. The SOFIA observations will give us additional information in the near-infrared, which was not provided by CoRoT. For the first time, it will be possible to measure the temperature of spots on the surface of CoRoT-2A independent of the unknown size of the spots. If we are able to resolve the umbra and penumbra of an individual spot in our observations, it will also be possible to measure - for the very first time - the structure and umbra/penumbra temperatures of spots on another solar-like star.

• DFG Programme: Research Grants