Detalles de publicación
PP 010086
Lucky Imaging Adaptive Optics of the browndwarf binary GJ569Bab
(1) IAC, (2) Departamento de Astrofísica Universidad de La Lagun, (3) CSIC, (4) Laboratoire de Physique Subatomique et Cosmologie-Grenoble, (5) Universidad Politécnica de Cartagena-Murcia, (6) Max-Planck-Institut für Sonnensystemforschung-Katlenburg-Lindau, Germany
The potential of combining Adaptive Optics (AO) and Lucky Imaging (LI) to achieve high precision astrometry and
differential photometry in the optical is investigated by conducting observations of the close 0\farcs1 brown dwarf
binary GJ569Bab. We took 50000 $I$-band images with our LI instrument FastCam attached to NAOMI, the 4.2-m William
Herschel Telescope (WHT) AO facility. In order to extract the most of the astrometry and photometry of the GJ569Bab
system we have resorted to a PSF fitting technique using the primary star GJ569A as a suitable PSF reference which
exhibits an $I$-band magnitude of $7.78\pm0.03$. The AO+LI observations at WHT were able to resolve the binary system
GJ569Bab located at $4\farcs 92 \pm 0\farcs05$ from GJ569A. We measure a separation of $98.4 \pm 1.1$ mas and $I$-band
magnitudes of $13.86 \pm 0.03$ and $14.48 \pm 0.03$ and $I-J$ colors of 2.72$\pm$0.08 and 2.83$\pm$0.08 for the Ba and
Bb components, respectively. Our study rules out the presence of any other companion to GJ569A down to magnitude
I$\sim$ 17 at distances larger than 1\arcsec. The $I-J$ colors measured are consistent with M8.5-M9 spectral types for
the Ba and Bb components. The available dynamical, photometric and spectroscopic data are consistent with a binary
system with Ba being slightly (10-20\%) more massive than Bb. We obtain new orbital parameters which are in good
agreement with those in the literature.
differential photometry in the optical is investigated by conducting observations of the close 0\farcs1 brown dwarf
binary GJ569Bab. We took 50000 $I$-band images with our LI instrument FastCam attached to NAOMI, the 4.2-m William
Herschel Telescope (WHT) AO facility. In order to extract the most of the astrometry and photometry of the GJ569Bab
system we have resorted to a PSF fitting technique using the primary star GJ569A as a suitable PSF reference which
exhibits an $I$-band magnitude of $7.78\pm0.03$. The AO+LI observations at WHT were able to resolve the binary system
GJ569Bab located at $4\farcs 92 \pm 0\farcs05$ from GJ569A. We measure a separation of $98.4 \pm 1.1$ mas and $I$-band
magnitudes of $13.86 \pm 0.03$ and $14.48 \pm 0.03$ and $I-J$ colors of 2.72$\pm$0.08 and 2.83$\pm$0.08 for the Ba and
Bb components, respectively. Our study rules out the presence of any other companion to GJ569A down to magnitude
I$\sim$ 17 at distances larger than 1\arcsec. The $I-J$ colors measured are consistent with M8.5-M9 spectral types for
the Ba and Bb components. The available dynamical, photometric and spectroscopic data are consistent with a binary
system with Ba being slightly (10-20\%) more massive than Bb. We obtain new orbital parameters which are in good
agreement with those in the literature.