* Astronomy

Blobrana · L

RE: CFBDSIR2149-0403

Blobrana · L

Title: CFBDSIR2149-0403: a 4-7 Jupiter-mass free-floating planet in the young moving group AB Doradus ?
Authors: P. Delorme, J. Gagné, L. Malo, C. Reylé, E. Artigau, L. Albert, T. Forveille, X. Delfosse, F. Allard, D. Homeier

We present in section 2 the detection of a lowgravity T dwarf, CFBDSIRJ214947.2-040308.9, hereafter CFBDSIR2149, that is probably a 4-7MJup free-oating planet. In section 3, we describe our spectroscopic data reduction and present the full Near-InfraRed (NIR) spectrum of this object, highlighting its low gravity features. In section 4 we discuss its likely membership to the young moving group AB Doradus (hereafter ABDMG). In section 5 we analyse its spectrum in the light of the age and metallicity constraints that would be brought by its probable ABDMG membership, and derive its fundamental physical parameters. Finally we discuss some of the implications of this discovery

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Blobrana · L

Title: CFBDSIR2149-0403: a 4-7 Jupiter-mass free-floating planet in the young moving group AB Doradus ?
Authors: P. Delorme, J. Gagné, L. Malo, C. Reylé, E. Artigau, L. Albert, T. Forveille, X. Delfosse, F. Allard, D. Homeier

Using the CFBDSIR wide field survey for brown dwarfs, we identified CFBDSIRJ214947.2-040308.9, a late T dwarf with atypically red J-Ks colour. We obtained an X-Shooter spectra, with signal detectable from 0.8 to 2.3 micron, which confirmed a T7 spectral type with an enhanced Ks-band flux indicative of a potentially low-gravity, young, object. The comparison of our near infrared spectrum with atmosphere models, for solar metallicity, shows that CFBDSIRJ214947.2-040308.9 is probably a 650-750 K, log g=3.75-4.0 substellar object. Using evolution models, this translates into a planetary mass object, with an age in the 20-200 Myr range. An independent Bayesian analysis from proper motion measurements results in a 87% probability that this free-floating planet is a member of the 50-120 Myr old AB Doradus moving group, which strengthens the spectroscopic youth diagnosis. By combining our atmospheric characterisation with the age and metallicity constraints arising from the probable membership to the AB Doradus moving group, we find that CFBDSIRJ214947.2-040308.9 is probably a 4-7 Jupiter masses free-floating planet with an effective temperature of ~700K and a log g of ~4.0, typical of the late T-type exoplanets that are targeted by direct imaging. We stress that this object could be used as a benchmark for understanding the physics of the similar T-type exoplanets that will be discovered by the upcoming high contrast imagers.

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