Multi-color photometry with SOFIA: Spots on the solar-like star CoRoT-2A and their effect on its exoplanet CoRoT-2b
Final Report Abstract
In 2012 I have been granted observations with the new Stratospheric Observatory for Infrared Astronomy (SOFIA), a joint venture of NASA and DLR. I proposed to observe one transit of the exoplanet CoRoT-2 b in front of its very active host-star CoRoT-2 A. SOFIA is capable of delivering quasi-space-based, shortcadence photometry in the optical and the near-infrared simultaneously for an uninterrupted time period of more than 3 hours spanning the entire planetary transit. The observations were supposed to provided us with the data necessary to investigate two still unresolved questions: (1) Does CoRoT-2 b’s radius appear to be inflated due to the stellar activity of its host-star? (2) What are the physical properties of starspots on CoRoT-2 A? Unfortunately, we were not able to get data from the SOFIA observatory during the first three observation periods (cycles), due to different technical problems. NASA rescheduled the observations for cycle 4 and the initially proposed observations were partially carried out on October 13, 2016 (UT), two weeks before the end of funding for this project. A premilinary analysis of the data was done, although an in-depth study will require significantly more time, especially in light of the problematic quality of the data. Although these difficulties prevented us from following the research plan laid out in the initial DFG proposal, we realized other projects which are closely connected to our main science topics: stellar photospheres, stellar activity, and exoplanets. First, using the ground-based infrared imager GROND, we showed that there is no way around airborne/space-based observations to obtain infrared transits of CoRoT-2 b good enough for the investigations we planned. We wrote a paper on stellar limb-darkening using Kepler data to better understand how the modeling of transit lightcurves is affected by the adopted limb-darkening law and coefficients, and investigated whether the theoretical coefficients are reliable or not. In another paper we showed how transit lightcurves are deformed when planets cross starspots on their way across the stellar disk and discuss the implications on transit timing variations. We also published a paper on flares in the HD 181068 system, which can serve as a model system to study star-planet interactions. Finally, we found the secondary eclipse of the exo-Neptune HAT-P-11 b in the Kepler lightcurves, which has been looked for since the planet’s detection in 2010 but could not be detected until now.
Publications
- (2017) Discovery of the secondary eclipse of HAT-P-11 b. A&A (Astronomy & Astrophysics) 597 A113
Huber, K. F.; Czesla, S.; Schmitt, J. H. M. M.
(See online at https://doi.org/10.1051/0004-6361/201629699) - High-precision stellar limb-darkening measurements. A transit study of 38 Kepler planetary candidates. Astronomy & Astrophysics, 2013, 560, A112
Mueller, H. M. & Huber, K. F., et al.
(See online at https://doi.org/10.1051/0004-6361/201322079) - A multiwavelength study of the hierarchical triple HD 181068. A test bed for studying star-planet interaction? Astronomy & Astrophysics, 2014, 570, A115
Czesla, S. & Huber, K. F., et al.
(See online at https://doi.org/10.1051/0004-6361/201423879) - Occultation Spectrophotometry of Extrasolar Planets with SOFIA. Proceedings of the International Astronomical Union, 2014, 293, 435-441
Angerhausen, D. & Huber, K. F., et al.
(See online at https://doi.org/10.1017/S1743921313013343) - How do starspots influence the transit timing variations of exoplanets? Simulations of individual and consecutive transits. Astronomy & Astrophysics, 2016, 585, A72
Ioannidis, P. & Huber, K. F., et al.
(See online at https://doi.org/10.1051/0004-6361/201527184)
