On the Orbit of the Binary Brown Dwarf Companion GL229 Ba and Bb
William Thompson, Dori Blakely, Jerry W. Xuan, Alexandre, Bouchard-C\^ot\'e, Guillaume Bourdarot, Miguel Biron-Lattes, Trevor Campbell,, Frank Eisenhauer, Thomas Henning, Markus Janson, Doug Johnstone, Jens, Kammerer, Quinn Konopacky, Sylvestre Lacour, Christian Marois

TL;DR
This paper models the orbit of the binary brown dwarf companion GL229 Ba and Bb using interferometry and RV data, providing precise orbital parameters and demonstrating methodological advances for low SNR interferometric data analysis.
Contribution
It introduces a Bayesian modeling approach with kernel phases and parallel tempering to accurately determine orbits from low SNR VLTI-GRAVITY data, and updates the orbital parameters of GL229 Ba and Bb.
Findings
Inner binary period of 12.1346 days with eccentricity 0.2317.
Masses of Ba and Bb are 37.7 and 33.4 Mjup respectively.
Outer orbit semi-major axis of 42.9 AU with eccentricity 0.736.
Abstract
The companion GL229B was recently resolved by Xuan et al. (2024) as a tight binary of two brown dwarfs (Ba and Bb) through VLTI-GRAVITY interferometry and VLT-CRIRES+ RV measurements. Here, we present Bayesian models of the interferometric and RV data in additional detail, along with an updated outer orbit of the brown dwarf pair about the primary. To create a model of the inner orbit with robust uncertainties, we apply kernel phases to the GRAVITY data to address baseline redundancy in the raw closure phases. Using parallel tempering, we constrain the binary's orbit using only VLTI-GRAVITY data, despite each epoch having low visibility-plane coverage and/or SNR. We demonstrate very agreement the VLTI-GRAVITY and CRIRES+ datasets and find that the inner binary has a period of 12.13460.0011 days, eccentricity of 0.23170.0025, and total mass of 71.00.4 Mjup, with Ba and Bb…
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Taxonomy
TopicsStellar, planetary, and galactic studies · Astronomy and Astrophysical Research · Astrophysics and Star Formation Studies
