A T8.5 BROWN DWARF MEMBER OF THE ξ URSAE MAJORIS SYSTEM

The Wide-field Infrared Survey Explorer has revealed a T8.5 brown dwarf (WISE J111838.70+312537.9) that exhibits common proper motion with a solar-neighborhood (8 pc) quadruple star system—ξ Ursae Majoris. The angular separation is 8.'5, and the projected physical separation is ≈4000 AU. The sub-solar metallicity and low chromospheric activity of ξ UMa A argue that the system has an age of at least 2 Gyr. The infrared luminosity and color of the brown dwarf suggests the mass of this companion ranges between 14 and 38 M_J for system ages of 2 and 8 Gyr, respectively.

[1]  William Herschel.  XIV. Continuation of an account of the changes that have happened in the relative situation of double stars , 1804, Philosophical Transactions of the Royal Society of London.

[2]  SHIV S. Kumar,et al.  Study of Degeneracy in Very Light Stars. , 1962 .

[3]  S. Tremaine,et al.  The Formation and Extent of the Solar System Comet Cloud , 1987 .

[4]  P. C. Keenan,et al.  The Perkins catalog of revised MK types for the cooler stars , 1989 .

[5]  M. Shara,et al.  Binary Star Orbits From Speckle Interferometry. VII. The Multiple System XI Ursae Majoris , 1995 .

[6]  Scott Milligan,et al.  Development of a three-channel SWIR camera, for ground-based astronomical imaging. (Two micron all sky survey, 2MASS) , 1996, Optics & Photonics.

[7]  R. Griffin.  Spectroscopic binary orbits from photoelectric radial velocities. Paper 142: Xi Ursae Majoris , 1998 .

[8]  Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog , 2002, astro-ph/0202164.

[9]  Michael E. Brown,et al.  The spectra of t dwarfs I: near-infrared data and spectral classification , 2001, astro-ph/0108452.

[10]  Adam Burrows,et al.  Beyond the T Dwarfs: Theoretical Spectra, Colors, and Detectability of the Coolest Brown Dwarfs , 2003, astro-ph/0304226.

[11]  H Germany,et al.  A Method of Correcting Near‐Infrared Spectra for Telluric Absorption , 2002, astro-ph/0211255.

[12]  O. Demircan,et al.  Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution , 2004, astro-ph/0404219.

[13]  John T. Rayner,et al.  Spextool: A Spectral Extraction Package for SpeX, a 0.8–5.5 Micron Cross‐Dispersed Spectrograph , 2004 .

[14]  G. Fazio,et al.  The Infrared Array Camera (IRAC) for the Spitzer Space Telescope , 2004, astro-ph/0405616.

[15]  Sandy K. Leggett,et al.  JHK Magnitudes for L and T Dwarfs and Infrared Photometric Systems , 2004 .

[16]  V. Kashyap,et al.  Stellar Coronal Abundances at Intermediate-Activity Levels: ξ UMa , 2005 .

[17]  E. L. Wright,et al.  Preliminary design of the Wide-Field Infrared Survey Explorer (WISE) , 2005, SPIE Optics + Photonics.

[18]  Martin G. Cohen,et al.  Absolute Calibration of the Infrared Array Camera on the Spitzer Space Telescope , 2005, astro-ph/0507139.

[19]  Wendy L. Freedman,et al.  The Carnegie Supernova Project: The Low‐Redshift Survey , 2005, astro-ph/0512039.

[20]  Douglas M. Summers,et al.  The W. M. Keck Observatory Laser Guide Star Adaptive Optics System: Overview , 2006 .

[21]  Douglas M. Summers,et al.  The W. M. Keck Observatory Laser Guide Star Adaptive Optics System: Performance Characterization , 2006 .

[22]  David A. Golimowski,et al.  A Unified Near-Infrared Spectral Classification Scheme for T Dwarfs , 2006 .

[23]  A. Burrows,et al.  A Systematic Study of Departures from Chemical Equilibrium in the Atmospheres of Substellar Mass Objects , 2007, 0705.3922.

[24]  L. Hillenbrand,et al.  Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics , 2008, 0807.1686.

[25]  J. Perea,et al.  The Night Sky at the Calar Alto Observatory II: The Sky at the Near-infrared , 2008 .

[26]  Walter Seifert,et al.  LUCIFER status report: summer 2008 , 2008, Astronomical Telescopes + Instrumentation.

[27]  Frantz Martinache,et al.  The performance of TripleSpec at Palomar , 2008, Astronomical Telescopes + Instrumentation.

[28]  D. Saumon,et al.  The Evolution of L and T Dwarfs in Color-Magnitude Diagrams , 2008, 0808.2611.

[29]  W. D. Vacca,et al.  THE INFRARED TELESCOPE FACILITY (IRTF) SPECTRAL LIBRARY: COOL STARS , 2009, 0909.0818.

[30]  R. Lenzen,et al.  Dynamical masses for the nearest brown dwarf binary: ε Indi Ba, Bb , 2008, 0811.0588.

[31]  J. Bochanski,et al.  THE BROWN DWARF KINEMATICS PROJECT. II. DETAILS ON NINE WIDE COMMON PROPER MOTION VERY LOW MASS COMPANIONS TO NEARBY STARS, , 2009, 0911.1363.

[32]  M. Skrutskie,et al.  FanCam—A Near-Infrared Camera for the Fan Mountain Observatory , 2009 .

[33]  A. M. Ghez,et al.  HIGH-PRECISION DYNAMICAL MASSES OF VERY LOW MASS BINARIES , 2010, 1001.4800.

[34]  R. Barkhouser,et al.  Design Overview and Performance of the WIYN High Resolution Infrared Camera (WHIRC) , 2010 .

[35]  Michael C. Cushing,et al.  FIRE SPECTROSCOPY OF FIVE LATE-TYPE T DWARFS DISCOVERED WITH THE WIDE-FIELD INFRARED SURVEY EXPLORER , 2011, 1104.2537.

[36]  Dominic J. Benford,et al.  THE FIRST HUNDRED BROWN DWARFS DISCOVERED BY THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE) , 2011, 1108.4677.

[37]  Michael C. Cushing,et al.  THE DISCOVERY OF Y DWARFS USING DATA FROM THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE) , 2011, 1108.4678.

[38]  E. Wright,et al.  WISE J163940.83−684738.6: A Y DWARF IDENTIFIED BY METHANE IMAGING , 2012, 1209.6123.

[39]  A. Burgasser,et al.  LOW-MASS TERTIARY COMPANIONS TO SPECTROSCOPIC BINARIES. I. COMMON PROPER MOTION SURVEY FOR WIDE COMPANIONS USING 2MASS , 2009, 1206.4289.

[40]  D. Saumon,et al.  NEGLECTED CLOUDS IN T AND Y DWARF ATMOSPHERES , 2012, 1206.4313.

[41]  M. Skrutskie,et al.  FURTHER DEFINING SPECTRAL TYPE “Y” AND EXPLORING THE LOW-MASS END OF THE FIELD BROWN DWARF MASS FUNCTION , 2012, 1205.2122.

[42]  M. C. Gálvez-Ortiz,et al.  Discovery of the benchmark metal-poor T8 dwarf BD +01° 2920B , 2012, 1201.3243.

[43]  M. Skrutskie,et al.  PARALLAXES AND PROPER MOTIONS OF ULTRACOOL BROWN DWARFS OF SPECTRAL TYPES Y AND LATE T , 2012, 1211.6977.