title: Discovery of a Brown Dwarf Companion to Gliese 570ABC: A 2MASS T Dwarf Significantly Cooler than Gliese 229B.
abstract: We report the discovery of a widely separated (258&farcs;3+/-0&farcs;4) T dwarf companion to the Gl 570ABC system. This new component, Gl 570D, was initially identified from the Two Micron All-Sky Survey. Its near-infrared spectrum shows the 1.6 and 2.2 µm CH4 absorption bands characteristic of T dwarfs, while its common proper motion with the Gl 570ABC system confirms companionship. Gl 570D (MJ=16.47+/-0.07) is nearly a full magnitude dimmer than the only other known T dwarf companion, Gl 229B, and estimates of L=&parl0;2.8+/-0.3&parr0;x10-6 L middle dot in circle and Teff=750+/-50 K make it significantly cooler and less luminous than any other known brown dwarf companion. Using evolutionary models by Burrows et al. and an adopted age of 2-10 Gyr, we derive a mass estimate of 50+/-20 MJup for this object.
authors.initials: AJ
authors.lastname: Burgasser
authors.initials: JD
authors.lastname: Kirkpatrick
authors.initials: RM
authors.lastname: Cutri
authors.initials: H
authors.lastname: McCallon
authors.initials: G
authors.lastname: Kopan
authors.initials: JE
authors.lastname: Gizis
authors.initials: J
authors.lastname: Liebert
authors.initials: IN
authors.lastname: Reid
authors.initials: ME
authors.lastname: Brown
authors.initials: DG
authors.lastname: Monet
authors.initials: CC
authors.lastname: Dahn
authors.initials: CA
authors.lastname: Beichman
authors.initials: MF
authors.lastname: Skrutskie