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A distant brown dwarf coplanar to a warm Jupiter and a hot super-Earth

Abstract

In transiting planetary systems, in which planetary sizes are accurately determined from transit observations, the presence of transit-timing variations1 (TTVs), especially when combined with radial velocity (RV) data, provides powerful constraints on masses and orbital eccentricities. Together, these measurements offer crucial insights into system architecture, formation mechanisms and dynamical evolution. We present long-term RV and transit/TTV monitoring of the relatively young star (age approximately 1 Gyr) TOI-201, revealing an exceptional multi-planet system composed of a hot super-Earth (SE) size planet transiting every 5.8 days, a warm Jupiter (WJ) on a 53-day orbit and an eccentric (e = 0.62) low-mass brown dwarf (BD) on an approximately 8-year orbit, with an estimated mass MBD of about 16 Jupiter masses. The BD is the longest-period transiting substellar object ever characterized by means of RVs and the only one known to be coplanar with inner planets. The architecture of this system suggests that the SE was formed isolated and in the innermost region of the gaseous disk. On the other hand, the orbital configuration of the outer companions suggests a nearly in situ formation of both objects, with the WJ forming in a dense inner disk. Alternatively, the BD might have formed farther out and migrated inward, while increasing its eccentricity owing to interactions with the disk.

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Fig. 1: Light curves and RVs.
The alternative text for this image may have been generated using AI.
Fig. 2: Orbital properties and system configuration.
The alternative text for this image may have been generated using AI.
Fig. 3: Formation scenarios.
The alternative text for this image may have been generated using AI.

Data availability

The TESS photometric data can be downloaded from the Mikulski Archive for Space Telescopes (MAST) archive at https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html?searchQuery=TOI201. The RV data are presented in the Supplementary Information.

Code availability

The Exo-Striker tool can be downloaded from https://github.com/3fon3fonov/exostriker. The CERES pipeline is available at https://github.com/rabrahm/ceres. The juliet tool can be downloaded from https://github.com/nespinoza/juliet. The Gastli python package can be found at https://gastli.readthedocs.io/en/latest/. The EXOFASTv2 code can be downloaded from https://github.com/jdeast/EXOFASTv2.

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