TY - JOUR
T1 - The discovery of y dwarfs using data from the wide-field infrared survey explorer (WISE)
AU - Cushing, Michael C.
AU - Kirkpatrick, J. Davy
AU - Gelino, Christopher R.
AU - Griffith, Roger L.
AU - Skrutskie, Michael F.
AU - Mainzer, A.
AU - Marsh, Kenneth A.
AU - Beichman, Charles A.
AU - Burgasser, Adam J.
AU - Prato, Lisa A.
AU - Simcoe, Robert A.
AU - Marley, Mark S.
AU - Saumon, D.
AU - Freedman, Richard S.
AU - Eisenhardt, Peter R.
AU - Wright, Edward L.
PY - 2011/12/10
Y1 - 2011/12/10
N2 - 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 H2O and CH4 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 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 NH3. 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 300K to 500K, making them the coldest spectroscopically confirmed brown dwarfs known to date.
AB - 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 H2O and CH4 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 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 NH3. 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 300K to 500K, making them the coldest spectroscopically confirmed brown dwarfs known to date.
KW - brown dwarfs
KW - infrared: stars
KW - stars: low-mass
UR - https://www.scopus.com/pages/publications/82255180619
UR - https://www.scopus.com/inward/citedby.url?scp=82255180619&partnerID=8YFLogxK
U2 - 10.1088/0004-637X/743/1/50
DO - 10.1088/0004-637X/743/1/50
M3 - Article
AN - SCOPUS:82255180619
SN - 0004-637X
VL - 743
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 50
ER -