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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 693603.0, MPI für Astronomie / Publikationen_mpia
The extremely red, young L dwarf PSO J318.5338–22.8603: a free-floating planetary-mass analog to directly imaged young gas-giant planets
Authors:Liu, Michael C.; Magnier, Eugene A.; Deacon, Niall R.; Allers, Katelyn N.; Dupuy, Trent J.; Kotson, Michael C.; Aller, Kimberly M.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Hodapp, K. W.; Jedicke, R.; Kaiser, N.; Kudritzki, R.-P.; Metcalfe, N.; Morgan, J. S.; Price, P. A.; Tonry, J. L.; Wainscoat, R. J.
Date of Publication (YYYY-MM-DD):2013
Title of Journal:The Astrophysical Journal Letters
Issue / Number:2
Start Page:id. L20 (7 pp)
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:We have discovered using Pan-STARRS1 an extremely red late-L dwarf, which has (J – K)MKO = 2.78 and (J – K)2MASS = 2.84, making it the reddest known field dwarf and second only to 2MASS J1207–39b among substellar companions. Near-IR spectroscopy shows a spectral type of L7 ± 1 and reveals a triangular H-band continuum and weak alkali (K I and Na I) lines, hallmarks of low surface gravity. Near-IR astrometry from the Hawaii Infrared Parallax Program gives a distance of 24.6 ± 1.4 pc and indicates a much fainter J-band absolute magnitude than field L dwarfs. The position and kinematics of PSO J318.5–22 point to membership in the β Pic moving group. Evolutionary models give a temperature of 1160^{+30}_{-40} K and a mass of 6.5^{+1.3}_{-1.0} M Jup, making PSO J318.5–22 one of the lowest mass free-floating objects in the solar neighborhood. This object adds to the growing list of low-gravity field L dwarfs and is the first to be strongly deficient in methane relative to its estimated temperature. Comparing their spectra suggests that young L dwarfs with similar ages and temperatures can have different spectral signatures of youth. For the two objects with well constrained ages (PSO J318.5–22 and 2MASS J0355+11), we find their temperatures are ≈400 K cooler than field objects of similar spectral type but their luminosities are similar, i.e., these young L dwarfs are very red and unusually cool but not "underluminous." Altogether, PSO J318.5–22 is the first free-floating object with the colors, magnitudes, spectrum, luminosity, and mass that overlap the young dusty planets around HR 8799 and 2MASS J1207–39.
Free Keywords:brown dwarfs; parallaxes; planets and satellites: atmospheres; proper motions; solar neighborhood; surveys
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X [ID No:1]
URL:http://cdsads.u-strasbg.fr/abs/2013ApJ...777L..20L [ID No:2]
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