Astrometric orbits of spectral binary brown dwarfs - I. Massive T dwarf companions to 2M1059-21 and 2M0805+48

June 2020 • 2020MNRAS.495.1136S

Authors • Sahlmann, J. • Burgasser, A. J. • Bardalez Gagliuffi, D. C. • Lazorenko, P. F. • Ségransan, D. • Zapatero Osorio, M. R. • Blake, C. H. • Gelino, C. R. • Martín, E. L. • Bouy, H.

Abstract • Near-infrared spectroscopic surveys have uncovered a population of short-period, blended-light spectral binaries composed of low-mass stars and brown dwarfs. These systems are amenable to orbit determination and individual mass measurements via astrometric monitoring. Here, we present first results of a multiyear campaign to obtain high-precision absolute astrometry for spectral binaries using the Gemini-South and Gemini-North GMOS imagers. We measure the complete astrometric orbits for two systems: 2M0805+48 and 2M1059-21. Our astrometric orbit of 2M0805+48 is consistent with its 2-yr radial velocity orbit determined previously and we find a mass of 66-14+5 MJup for its T5.5 companion. For 2M1059-21, we find a 1.9-yr orbital period and a mass of 67-5+4 MJup for its T3.5 companion. We demonstrate that sub-milliarcsecond absolute astrometry can be obtained with both GMOS imagers and that this is an efficient avenue for confirming and characterizing ultracool binary systems.


IPAC Authors

Chris Gelino

Associate Scientist