Transiting exoplanets from the CoRoT space mission. XX. CoRoT-20b: A very high density, high eccentricity transiting giant planet

LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92195, Meudon, France
Astronomy and Astrophysics (Impact Factor: 4.48). 01/2012; 538:145. DOI: 10.1051/0004-6361/201117681
Source: arXiv

ABSTRACT We report the discovery by the CoRoT space mission of a new giant
planet, CoRoT-20b. The planet has a mass of 4.24 ± 0.23
MJup and a radius of 0.84 ± 0.04 RJup. With
a mean density of 8.87 ± 1.10 g cm-3, it is among the
most compact planets known so far. Evolutionary models for the planet
suggest a mass of heavy elements of the order of 800 M⊕
if embedded in a central core, requiring a revision either of the planet
formation models or both planet evolution and structure models. We note
however that smaller amounts of heavy elements are expected by more
realistic models in which they are mixed throughout the envelope. The
planet orbits a G-type star with an orbital period of 9.24 days and an
eccentricity of 0.56.The star's projected rotational velocity is vsini =
4.5 ± 1.0 km s-1, corresponding to a spin period of
11.5 ± 3.1 days if its axis of rotation is perpendicular to the
orbital plane. In the framework of Darwinian theories and neglecting
stellar magnetic breaking, we calculate the tidal evolution of the
system and show that CoRoT-20b is presently one of the very few
Darwin-stable planets that is evolving toward a triple synchronous state
with equality of the orbital, planetary and stellar spin periods.

The CoRoT space mission, launched on December 27th 2006, has been
developed and is operated by CNES, with the contribution of Austria,
Belgium, Brazil, ESA (RSSD and Science Programme), Germany, and Spain.

Download full-text


Available from: S. Aigrain, Aug 09, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Context: CoRoT is a pioneering space mission whose primary goals are stellar seismology and extrasolar planets search. Its surveys of large stellar fields generate numerous planetary candidates whose lightcurves have transit-like features. An extensive analytical and observational follow-up effort is undertaken to classify these candidates. Aims: The list of planetary transit candidates from the CoRoT LRa01 star field in the Monoceros constellation towards the Galactic anti-center is presented. The CoRoT observations of LRa01 lasted from 24 October 2007 to 3 March 2008. Methods: 7470 chromatic and 3938 monochromatic lightcurves were acquired and analysed. Instrumental noise and stellar variability were treated with several filtering tools by different teams from the CoRoT community. Different transit search algorithms were applied to the lightcurves. Results: Fifty-one stars were classified as planetary transit candidates in LRa01. Thirty-seven (i.e., 73 % of all candidates) are "good" planetary candidates based on photometric analysis only. Thirty-two (i.e., 87 % of the "good" candidates) have been followed-up. At the time of this writing twenty-two cases have been solved and five planets have been discovered: three transiting hot-Jupiters (CoRoT-5b, CoRoT-12b, and CoRoT-21b), the first terrestrial transiting planet (CoRoT-7b), and another planet in the same system (CoRoT-7c, detected by radial velocity survey only). Evidences of another non-transiting planet in the CoRoT-7 system, namely CoRoT-7d, have been recently found.
    Astronomy and Astrophysics 10/2011; 538(2012). DOI:10.1051/0004-6361/201116934 · 4.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Exoplanets show a pile-up of Jupiter-size planets in orbits with a 3-day period. A fraction of these hot Jupiters have retrograde orbits with respect to the parent star's rotation. To explain these observations we performed a series of numerical integrations of planet scattering followed by the tidal circularization. We considered planetary systems having 3 and 4 planets initially. We found that the standard Kozai migration is an inefficient mechanism for the formation of hot Jupiters. Our results show the formation of two distinct populations of hot Jupiters. The inner population of hot Jupiters with semimajor axis a < 0.03 AU formed in the systems where no planetary ejections occurred. This group contained a significant fraction of highly inclined and retrograde orbits, with distributions largely independent of the initial setup. However, our follow-up integrations showed that this populations was transient with most planets falling inside the Roche radius of the star in <1 Gyr. The outer population of hot Jupiters formed in systems where at least one planet was ejected. This population survived the effects of tides over >1 Gyr. The semimajor axis distribution of Population II fits nicely the observed 3-day pile-up. The inclination distribution of the outer hot planets depends on the number of planets in the initial systems and the 4-planet case showed a larger proportion (up to 10%), and a wider spread in inclination values. As the later results roughly agrees with observations, this may suggest that the planetary systems with observed hot Jupiters were originally rich in the number of planets, some of which were ejected. In a broad perspective, our work therefore hints on an unexpected link between the hot Jupiters and recently discovered free floating planets.
    The Astrophysical Journal 10/2011; 751(2). DOI:10.1088/0004-637X/751/2/119 · 6.28 Impact Factor
  • Astronomy and Astrophysics 01/2012; 537:A54. DOI:10.1051/0004-6361/201117916 · 4.48 Impact Factor
Show more