Publications (5)0 Total impact
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ABSTRACT: 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.
10/2012;
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S. K. Leggett,
L. Albert, E. Artigau,
Ben Burningham,
X. Delfosse,
P. Delorme,
T. Forveille,
P. W. Lucas,
M. S. Marley,
D. J. Pinfield,
C. Reyle,
D. Saumon,
R. L. Smart,
S. J. Warren
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ABSTRACT: Mid-infrared data, including Spitzer warm-IRAC [3.6] and [4.5] photometry, is critical for understanding the cold population of brown dwarfs now being found, objects which have more in common with planets than stars. As effective temperature (T_eff) drops from 800 K to 400 K, the fraction of flux emitted beyond 3 microns increases rapidly, from about 40% to >75%. This rapid increase makes a color like H-[4.5] a very sensitive temperature indicator, and it can be combined with a gravity- and metallicity-sensitive color like H-K to constrain all three of these fundamental properties, which in turn gives us mass and age for these slowly cooling objects. Determination of mid-infrared color trends also allows better exploitation of the WISE mission by the community. We use new Spitzer Cycle 6 IRAC photometry, together with published data, to present trends of color with type for L0 to T10 dwarfs. We also use the atmospheric and evolutionary models of Saumon & Marley to investigate the masses and ages of 13 very late-type T dwarfs, which have H-[4.5] > 3.2 and T_eff ~ 500 K to 750 K. Comment: To be published in the on-line version of the Proceedings of Cool Stars 16 (ASP Conference Series). This is an updated version of Leggett et al. 2010 ApJ 710 1627; a photometry compilation is available at http://www.gemini.edu/staff/sleggett
12/2010;
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P. Delorme,
L. Albert,
T. Forveille, E. Artigau,
X. Delfosse,
C. Reylé,
C. J. Willott,
E. Bertin,
S. M. Wilkins,
F. Allard,
D. Arzoumanian
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ABSTRACT: We present the first results of the ongoing Canada-France Brown Dwarfs Survey-InfraRed, hereafter CFBDSIR, a Near InfraRed extension to the optical wide-field survey CFBDS. Our final objectives are to constrain ultracool atmosphere physics by finding a statistically significant sample of objects cooler than 650K and to explore the ultracool brown dwarf mass function building on a well defined sample of such objects. Candidates are identified in CFHT/WIRCam J and CFHT/MegaCam z' images using optimised psf-fitting, and we follow them up with pointed near infrared imaging with SOFI at NTT. We finally obtain low resolution spectroscopy of the coolest candidates to characterise their atmospheric physics. We have so far analysed and followed up all candidates on the first 66 square degrees of the 335 square degrees survey. We identified 55 T-dwarfs candidates with z'-J > 3:5 and have confirmed six of them as T-dwarfs, including 3 that are strong later-than-T8 candidates, based on their far-red and NIR colours. We also present here the NIR spectra of one of these ultracool dwarfs, CFBDSIR1458+1013 which confirms it as one of the coolest brown dwarf known, possibly in the 550-600K temperature range. From the completed survey we expect to discover 10 to 15 dwarfs later than T8, more than doubling the known number of such objects. This will enable detailed studies of their extreme atmospheric properties and provide a stronger statistical base for studies of their luminosity function. Comment: A&A, Accepted
04/2010;
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ABSTRACT: The Canada-France Brown Dwarf Survey is a wide eld survey for cool brown dwarfs conducted with the MegaCam camera on the CFHT telescope. Our objectives are to nd ultracool brown dwarfs and to constrain the eld brown dwarf mass function from a large and homogeneous sample of L and T dwarfs. We identify candidates in CFHT/Megacam i' and z' images and follow them up with pointed NIR imaging on several telescopes. Our survey has to date found 50 T dwarfs candidates and 170 L or late M dwarf candidates drawn from a larger sample of 1300 candidates with typical ultracool dwarfs i'-z' colours, found in 900 square degrees. We currently have completed the NIR follow-up on a large part of the survey for all candidates from the latest T dwarfs known to the late L color range. This allows us to build on a complete and well de ned sample of ultracool dwarfs to investigate the luminosity function of eld L and T dwarfs. Comment: Cool Stars XV conference. to appear in proceedings of Cool Stars XV Conference
12/2008;
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ABSTRACT: From a 2 x 2 degree survey of NGC 6822 we have previously established that this Local Group dwarf irregular galaxy possesses a huge spheroid having more than one degree in length. This spheroid is in rotation but its rotation curve is known only within ~15' from the center. It is therefore critical to identify bright stars belonging to the spheroid to characterize, as far as possible, its outer kinematics. We use the new wide field near infrared imager CPAPIR, operated by the SMARTS consortium, to acquire J, Ks images of two 34.8' x 34.8' areas in the outer spheroid to search for C stars. The colour diagram of the fields allows the identification of 192 C stars candidates but a study of the FWHM of the images permits the rejection of numerous non-stellar objects with colours similar to C stars. We are left with 75 new C stars, their mean Ks magnitude and mean colour are similar to the bulk of known NGC 6822 C stars. This outer spheroid survey confirms that the intermediate-age AGB stars are a major contributor to the stellar populations of the spheroid. The discovery of some 50 C stars well beyond the limit of the previously known rotation curve calls for a promising spectroscopic follow-up to a major axis distance of 40'. Comment: 13 pages
06/2006;
Institutions
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2010
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Université de Montréal
Montréal,
Quebec,
Canada
