The discovery of y dwarfs using data from the wide-field infrared survey explorer (WISE)

• Main Authors: Cushing, Michael C. (Author), Kirkpatrick, J. Davy (Author), Gelino, Christopher R. (Author), Griffith, Roger L. (Author), Skrutskie, Michael F. (Author), Mainzer, A. (Author), Marsh, Kenneth A. (Author), Beichman, Charles A. (Author), Burgasser, Adam J. (Contributor), Prato, Lisa A. (Author), Simcoe, Robert A. (Contributor), Marley, Mark S. (Author), Saumon, D. (Author), Freedman, Richard S. (Author), Eisenhardt, P. R. (Author), Wright, Edward L. (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Physics (Contributor)
• Format: Article
• Language: English
• Published: IOP Publishing, 2013-01-30T21:19:53Z.
• Subjects: Article
• Online Access: Get fulltext

We present the discovery of seven ultracool brown dwarfs identified with the Wide-field Infrared Survey Explorer (WISE). Near-infrared spectroscopy reveals deep absorption bands of H[subscript 2]O and CH[subscript 4] that indicate all seven of the brown dwarfs have spectral types later than UGPS J072227.51-054031.2, the latest-type T dwarf currently known. The spectrum of WISEP J182831.08+265037.8 is distinct in that the heights of the J- and H-band peaks are approximately equal in units of f [subscript λ], so we identify it as the archetypal member of the Y spectral class. The spectra of at least two of the other brown dwarfs exhibit absorption on the blue wing of the H-band peak that we tentatively ascribe to NH[subscript 3]. These spectral morphological changes provide a clear transition between the T dwarfs and the Y dwarfs. In order to produce a smooth near-infrared spectral sequence across the T/Y dwarf transition, we have reclassified UGPS 0722-05 as the T9 spectral standard and tentatively assign WISEP J173835.52+273258.9 as the Y0 spectral standard. In total, six of the seven new brown dwarfs are classified as Y dwarfs: four are classified as Y0, one is classified as Y0 (pec?), and WISEP J1828+2650 is classified as >Y0. We have also compared the spectra to the model atmospheres of Marley and Saumon and infer that the brown dwarfs have effective temperatures ranging from 300 K to 500 K, making them the coldest spectroscopically confirmed brown dwarfs known to date.
University of California, San Diego (Chris and Warren Hellman Fellowship Program)
United States. National Aeronautics and Space Administration (Postdoctoral Program)