3D Orbital Architecture of a Dwarf Binary System and Its Planetary Companion

Abstract

Because of the diversity of stellar masses and orbital sizes of binary systems and the complex interaction between star–star, star–planet, and planet–planet, it has been difficult to fully characterize the planetary systems associated with binary systems. Here, we report high-precision astrometric observations of the low-mass binary system GJ 896AB, revealing the presence of a Jupiter-like planetary companion (GJ 896Ab). The planetary companion is associated to the main star GJ 896A, with an estimated mass of 2.3 Jupiter masses and an orbit period of 284.4 days. A simultaneous analysis of the relative astrometric data obtained in the optical and infrared with several telescopes, and the absolute astrometric data obtained at radio wavelengths with the Very Long Baseline Array (VLBA), reveals, for the first time, the fully characterized three-dimensional (3D) orbital plane orientation of the binary system and the planetary companion. The planetary and binary orbits are found to be in a retrograde configuration and with a large mutual inclination angle (Φ = 148°) between both orbital planes. Characterizing the 3D orbital architecture of binary systems with planets is important in the context of planet formation, as it could reveal whether the systems were formed by disk fragmentation or turbulence fragmentation, as well as the origin of spin–orbit misalignment. Furthermore, as most stars are in binary or multiple systems, our understanding of systems such as this one will help to further understand the phenomenon of planetary formation in general.

Spectroscopic Follow-up of Gaia Exoplanet Candidates: Impostor Binary Stars Invade the Gaia DR3 Astrometric Exoplanet Candidates

“…With only one previous discovery (Curiel et al 2022), astrometry is not yet a well-developed technique for the detection of exoplanets. The method comes with its own set of unique challenges.…”

Precise Mass, Orbital Motion, and Stellar Properties of the M-dwarf Binary LP 349−25AB

“…We reduced the data with the Astronomical Imaging Processing System (AIPS; Greisen 2003), following standard procedures for phase-referencing observations (Torres et al 2007;Ortiz-Leon et al 2017) as described in Curiel et al (2020) and Curiel et al (2022). First, corrections for the ionosphere dispersive delays were applied.…”

“…We followed the same fitting procedure presented by Curiel et al (2022). In short, we used three astrometric fitting methods: the asexual genetic algorithm (AGA; Cantó et al 2009;Curiel et al 2011Curiel et al , 2019Curiel et al , 2020, a nonlinear least-squares algorithm, and Markov Chain Monte Carlo (MCMC; Curiel et al 2022).…”

“…Thus, close binary systems can be used to calibrate evolutionary models due to the measurable dynamical masses and coevolution of their components, which eliminates age as a confusion factor (Zhang et al 2020). Only a few close binaries with lowmass components have been studied in detail with multiepoch very long baseline interferometry (VLBI) observations, giving high-precision mass estimates (e.g., Dupuy et al 2016;Ortiz-Leon et al 2017;Zhang et al 2020;Curiel et al 2022). Observations of nearby UCDs also offer the possibility of finding Jupiter-like planetary companions because the astrometric signature of such planets (the reflex motion of the the star due to the gravitational pull of the companion) exceed the astrometric precision that can be achieved with the Very Long Baseline Array (VLBA; of the order of, or even better than, 100 μas).…”

“…VLBA observations can isolate the emission to individual components of the binary, and trace their absolute motion in the sky with extremely high precision. Curiel et al (2022) previously employed such a method to obtain absolute astrometry, and subsequently constrain the orbits and individual masses of the M dwarf binary system GJ896AB, whose secondary component was also found to be radio emitting. Furthermore, a Jovian-like planet was found orbiting the main star of this binary system.…”