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

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.
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https://hal-insu.archives-ouvertes.fr/insu-03678867
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Submitted on : Wednesday, May 25, 2022 - 4:15:12 PM
Last modification on : Thursday, May 26, 2022 - 3:48:01 AM

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J. Sahlmann, A. J. Burgasser, D. C. Bardalez Gagliuffi, P. F. Lazorenko, D. Ségransan, et al.. Astrometric orbits of spectral binary brown dwarfs - I. Massive T dwarf companions to 2M1059-21 and 2M0805+48. Monthly Notices of the Royal Astronomical Society, 2020, 495, pp.1136-1147. ⟨10.1093/mnras/staa1235⟩. ⟨insu-03678867⟩

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