Francois Fressin, Guillermo Torres, Frederic Pont, Heather A. Knutson, David Charbonneau, Tsevi Mazeh, Suzanne Aigrain, Malcolm Fridlund, Christopher E. Henze, Tristan Guillot, Heike Rauer
The detection and characterization of the first transiting super-Earth,
CoRoT-7 b, has required an unprecedented effort in terms of telescope time and
analysis. Although the star does display a radial velocity signal at the period
of the planet, this has been difficult to disentangle from the intrinsic
stellar variability, and pinning down the velocity amplitude has been very
challenging. As a result, the precise value of the mass of the planet - and
even the extent to which it can be considered to be confirmed - have been
debated in the recent literature, with six mass measurements published so far
based on the same spectroscopic observations, ranging from about 2 to 8 Earth
masses. Here we report on an independent validation of the planet discovery,
using one of the fundamental properties of a transit signal: its achromaticity.
We observed four transits of CoRoT-7 b with Spitzer, in order to determine
whether the depth of the transit signal in the near-infrared is consistent with
that observed in the CoRoT bandpass, as expected for a planet. We detected the
transit and found an average depth of 0.426 {\pm} 0.115 mmag at 4.5 {\mu}m,
which is in good agreement with the depth of 0.350 {\pm} 0.011 mmag found by
CoRoT. These observations place important constraints on the kinds of
astrophysical false positives that could mimic the signal. Combining this with
additional constraints reported earlier, we performed an exhaustive exploration
of possible blends scenarios for CoRoT-7 b using the BLENDER technique. We are
able to rule out the vast majority of false positives, and the remaining ones
are found to be much less likely than a true transiting planet. We thus
validate CoRoT-7 b as a bona-fide planet with a very high degree of confidence,
independently of any radial-velocity information. Our Spitzer observations have
additionally allowed us to significantly improve the ephemeris of the planet.
View original:
http://arxiv.org/abs/1110.5336
No comments:
Post a Comment