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 resolvedinto two objects of spectral types M8.5V and M9V, separated by0.9 AU, and total mass of 0.125 Msol.

Martín et al. (2000); Lane et al. (2001)

GJ 569: a tertiary system

GJ 569B is a proper motioncompanion locatedat 50 AU fromGJ 569A.

Forrest et al. (1988)

A

B

Keck AO NIRSPEC low –res spectra.Teff ~ 2450, 2300 K.

GJ 569B: the binary companion

Lane et al. (2001)

Period = 876.0 ± 9.2 dayse = 0.32 ± 0.01a = 0.90 ± 0.01 AUi = 34 ± 2 deg = 257 ± 2 deg = 321 ± 2 degEpoch (MJD) = 51822 ± 3 days

Total mass = 0.125 ± 0.005 Msol

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) = 0.068 ± 0.011 Msol

M (GJ 569Bb) = 0.057 ± 0.011 Msol

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 300-800 Myr.

Additionally, the star GJ 569A exhibits many of the attributes of young stars (120-1000 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.

BaBb

BaBb

Dependence of KI lines on Teff and gravity

Teff = 2400 K log g = 4.5

From synthetic computations, the KI lines are remarkably sensitive to both Teff 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 = 4.5-5.0 [cm s-2] Teff = 2400-2500 Kvrot sin i ~ 30 km s-1

KI KI

Increasing list of nearby ultra-cool binaries …

Table from Close et al. (2003) Eps Indi B 2.6 T1/T6 0.047 0.028 15 (McCaughrean et al. 2004)

0.146 MsolBouy et al. (2004)