M. R. Zapatero Osorio (LAEFF-INTA, Spain) B. L. Lane (MIT, USA) Ya. Pavlenko (MAO, Ukraine) E. L. Martín (IAC, Spain) M. Britton, S. R. Kulkarni (Caltech, USA) La Gomera, June 2004

Lane et al. (2001) Keck AO images. GJ 569B is resolved into two objects of spectral types M8.5V and M9V, separated by 0.9 AU, and total mass of M sol. Martín et al. (2000); Lane et al. (2001) GJ 569: a tertiary system GJ 569B is a proper motion companion located at 50 AU from GJ 569A. Forrest et al. (1988) A B Keck AO NIRSPEC low –res spectra. T eff ~ 2450, 2300 K.

GJ 569B: the binary companion Lane et al. (2001) Period = ± 9.2 days e = 0.32 ± 0.01 a = 0.90 ± 0.01 AU i = 34 ± 2 deg  = 257 ± 2 deg  = 321 ± 2 deg Epoch (MJD) = ± 3 days Total mass = ± M sol Astrometric results:

GJ 569Ba and Bb: Keck AO NIRSPEC hi-res spectra 28 June 2001; J-band 2D spectrum GJ 569Bb GJ 569Ba Four observing dates between 2001 May and 2001 September.

GJ 569Ba and Bb: Keck AO NIRSPEC hi-res spectra GJ 569Ba GJ 569Bb

GJ 569Ba and Bb: velocities The expected velocity curve, based solely on the astrometric result, is plotted as a red line. The observed relative velocities and the curve are in very good agreement.

GJ 569Ba and Bb: velocities GJ 569Ba GJ 569Bb The best fit to the unweighted velocity data yields: M (GJ 569Ba) = ± M sol M (GJ 569Bb) = ± M sol Zapatero Osorio et al. (2004) GJ 569Bb is the first brown dwarf confirmed dynamically, i.e., without any theoretical assumption.

GJ 569: the age of the system Chereul et al. (1999) GJ 569A The galactic UVW velocities of GJ 569A are within 1  the values of a known star cluster moving group, which has an estimated age of Myr. Additionally, the star GJ 569A exhibits many of the attributes of young stars ( Myr).

GJ 569Ba and Bb and evolutionary models Models nicely reproduce the substellar mass-luminosity relation of the binary if the system is about 300 Myr. Ba Bb Ba Bb

Dependence of KI lines on T eff and gravity T eff = 2400 Klog g = 4.5 From synthetic computations, the KI lines are remarkably sensitive to both T eff and gravity. (See also observed spectra of Gorlova et al. 2003; McGovern et al. 2004).

GJ 569Ba and Bb: Keck AO NIRSPEC hi-res spectra Model atmospheres fitting yields: log g = [cm s -2 ] T eff = K v rot sin i ~ 30 km s -1 KI

Increasing list of nearby ultra-cool binaries … Table from Close et al. (2003) Eps Indi B 2.6 T1/T (McCaughrean et al. 2004) M sol Bouy et al. (2004)