Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2009-01-26
Astrophys.J.695:1517-1526,2009
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
26 pages, including 2 Tables and 9 Figures, accepted for publication in Astrophysical Journal
Scientific paper
10.1088/0004-637X/695/2/1517
We present Spitzer 7.6-14.5um spectra of ULAS J003402.77-005206.7 and ULAS J133553.45+113005.2, two T9 dwarfs with the latest spectral types currently known. We fit synthetic spectra and photometry to the near- through mid-infrared energy distributions of these dwarfs and that of the T8 dwarf 2MASS J09393548-2448279. We also analyse near-infrared data for another T9, CFBD J005910.82-011401.3. We find that the ratio of the mid- to near-infrared fluxes is very sensitive to effective temperature at these low temperatures, and that the 2.2 and 4.5um fluxes are sensitive to metallicity and gravity; there is a degeneracy between these parameters. The 4.5 and 10um fluxes are also sensitive to vertical transport of gas through the atmosphere, which we find to be significant for these dwarfs. The full near- through mid-infrared spectral energy distribution allows us to constrain the effective temperature (K)/gravity (m/s2)/metallicity ([m/H] dex) of ULAS J0034-00 and ULAS J1335+11 to 550-600/ 100-300/ 0.0-0.3 and 500-550/ 100-300/ 0.0-0.3, respectively. These fits imply low masses and young ages for the dwarfs of 5-20 M(Jup) and 0.1-2 Gyr. The fits to 2MASS J0939-24 are in good agreement with the measured distance, the observational data, and the earlier T8 near-infrared spectral type if it is a slightly metal-poor 4-10 Gyr old system consisting of a 500 and 700K, ~25 and ~40 M(Jup), pair, although it is also possible that it is an identical pair of 600K, 30 M(Jup), dwarfs. As no mid-infrared data are available for CFBD J0059-01 its properties are less well constrained; nevertheless it appears to be a 550-600K dwarf with g= 300-2000 m/s2 and [m/H]= 0-0.3 dex. These properties correspond to mass and age ranges of 10-50 M(Jup) and 0.5-10 Gyr for this dwarf.
Burningham Ben
Cushing Michael. C.
Jones Hugh R. A.
Kirkpatrick Joseph D.
Leggett Sandy K.
No associations
LandOfFree
The Physical Properties of Four ~600K T Dwarfs does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Physical Properties of Four ~600K T Dwarfs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Physical Properties of Four ~600K T Dwarfs will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-360939