Spitzer Space Telescope - Directors Discretionary Time Proposal #540


First complete transit observation of the 111-day-period planet HD80606b

Principal Investigator: Guillaume Hebrard
           Institution: IAP

     Technical Contact: Guillaume Hebrard, IAP

Co-Investigators: 
Jean-Michel Desert, IAP
Claire Moutou, OAMP
Xavier Bonfils, LAOG
David Ehrenreich, LAOG
Thierry Forveille, LAOG
Alfred Vidal-Madjar, IAP
Frederic Pont, University of Exeter
Nuno Santos, Univ. do Porto

Science Category: extrasolar planets
 Observing Modes: IracPost-Cryo Mapping
  Hours Approved: 19.0

Abstract:
Due to its high-eccentricity 111-day-period orbit, HD80606b is an extreme 
planet, going from hot-Jupiters mode to a much cooler regime near the 
habitable zone. Its transiting nature was recently established by ground 
observations, including the photometric and spectroscopic data we secured 
at Haute-Provence Observatory, covering a part of this extremely long-duration
transit (about 12 hours). The fortunate properties of HD80606b provides an 
amazing opportunity to challenge the field of exoplanets characterization. 

There is intense interest in obtaining a first complete transit of HD80606b 
with Spitzer. However, the end of the "Cold Spitzer" made impossible its 
scheduled observation. We thus propose to observe with IRAC onboard the 
"Warm Spitzer" the complete transit of HD80606b expected on January 13-14, 2010, 
which will produce the best-quality transit light curve ever obtained from 
any extrasolar planet. We will simultaneously conduct a photometric and 
spectroscopic campaign from ground, at that date and the weeks around. This 
full dataset will allow system parameters to be accurately measured, including 
stellar and planetary masses, radii and densities, orbit inclination and 
eccentricity, or spin-orbit misalignment angle. They are fundamental parameters 
to understand the origin and the evolution of this system. Such well-observable 
transits of HD80606b are extremely rare, and opportunities should not be missed. 
Together with complementary ground observations, the Spitzer January 2010 
complete transit light curve of this exceptional object will provide a 
long-term legacy value.