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Title: Resolved spectroscopy of the T8.5 AND Y0-0.5 binary WISEPC J121756.91+162640.2AB

We present 0.9-2.5 μm resolved spectra for the ultracool binary WISEPC J121756.91+162640.2AB. The system consists of a pair of brown dwarfs that straddles the currently defined T/Y spectral type boundary. We use synthetic spectra generated by model atmospheres that include chloride and sulfide clouds (Morley et al.), the distance to the system (Dupuy and Kraus), and the radius of each component based on evolutionary models (Saumon and Marley) to determine a probable range of physical properties for the binary. The effective temperature of the T8.5 primary is 550-600 K and that of the Y0-Y0.5 secondary is ≈450 K. The atmospheres of both components are either free of clouds or have extremely thin cloud layers. We find that the masses of the primary and secondary are 30 and 22 M {sub Jup}, respectively, and that the age of the system is 4-8 Gyr. This age is consistent with astrometric measurements (Dupuy and Kraus) that show that the system has kinematics intermediate between those of the thin and thick disks of the Galaxy. An older age is also consistent with an indication by the H – K colors that the system is slightly metal poor.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Gemini Observatory, Northern Operations Center, 670 North A'ohoku Place, Hilo, HI 96720 (United States)
  2. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)
  3. Smithsonian Astrophysical Observatory, 60 Garden Street, MS 9, Cambridge, MA 02138 (United States)
  4. Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
  5. NASA Ames Research Center, Mail Stop 245-3, Moffett Field, CA 94035 (United States)
  6. Los Alamos National Laboratory, P.O. Box 1663, MS F663, Los Alamos, NM 87545 (United States)
Publication Date:
OSTI Identifier:
22348316
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 780; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ATMOSPHERES; CHLORIDES; COLOR; GALAXIES; MASS; METALS; SPECTRA; SPECTROSCOPY; STARS; SULFIDES