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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 709787.0, MPI für Astronomie / Publikationen_mpia
Deep z-band observations of the coolest Y dwarf
Authors:Kopytova, T. G.; Crossfield, I. J. M.; Deacon, N. R.; Brandner, W.; Buenzli, E.; Bayo, A.; Schlieder, J. E.; Manjavacas, E.; Biller, B. A.; Kopon, D.
Date of Publication (YYYY-MM-DD):2014
Title of Journal:The Astrophysical Journal
Volume:797
Issue / Number:1
Start Page:id. 3 (4 pp)
Audience:Not Specified
Abstract / Description:WISE J085510.83-071442.5 (hereafter, WISE 0855-07) is the coolest Y dwarf known to date and is located at a distance of 2.31 ± 0.08 pc, giving it the fourth largest parallax of any known star or brown dwarf system. We report deep z-band observations of WISE 0855-07 using FORS2 on UT1/Very Large Telescope. We do not detect any counterpart to WISE 0855-07 in our z-band images and estimate a brightness upper limit of AB mag > 24.8 (F nu < 0.45 muJy) at 910 ± 65 nm with 3sigma confidence. We combine our z-band upper limit with previous near- and mid-infrared photometry to place constraints on the atmospheric properties of WISE 0855-07 via comparison to models which implement water clouds in the atmospheres of T eff < 300 K substellar objects. We find that none of the available models that implement water clouds can completely reproduce the observed spectral energy distribution of WISE 0855-07. Every model significantly disagrees with the (3.6 mum/4.5 mum) flux ratio and at least one other bandpass. Since methane is predicted to be the dominant absorber at 3-4 mum, these mismatches might point to an incorrect or incomplete treatment of methane in current models. We conclude that (a) WISE0855-07 has T eff ~ 200-250 K, (b) <80% of its surface is covered by clouds, and (c) deeper observations, and improved models of substellar evolution, atmospheres, clouds, and opacities will be necessary to better characterize this object. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program 293.C-5008(A).
Free Keywords:brown dwarfs; stars: individual: WISE J085510.83-071442.5; stars: low-mass
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X %R 10.1088/0004-637X/797/1/3
URL:http://adsabs.harvard.edu/abs/2014ApJ...797....3K
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