doi: 10.1126/sciadv.adu0627. Epub 2025 Apr 16.
Evidence for a polar circumbinary exoplanet orbiting a pair of eclipsing brown dwarfs
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- PMID:40238865
- PMCID: PMC12002110
- DOI: 10.1126/sciadv.adu0627
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Evidence for a polar circumbinary exoplanet orbiting a pair of eclipsing brown dwarfs
Thomas A Baycroft et al. Sci Adv..
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Abstract
One notable example of exoplanet diversity is the population of circumbinary planets, which orbit around both stars of a binary star system. There are, so far, only 16 known circumbinary exoplanets, all of which lie in the same orbital plane as the host binary. Suggestions indicate that circumbinary planets could also exist on orbits highly inclined to the binary, close to 90°, polar orbits. No such planets have been found yet, but polar circumbinary gas and debris discs have been observed, and if these were to form planets, then those would be left on a polar orbit. We report strong evidence for a polar circumbinary exoplanet, which orbits a close pair of brown dwarfs that are on an eccentric orbit. We use radial velocities to measure a retrograde apsidal precession for the binary and show that this can only be attributed to the presence of a polar planet.
Figures
The division into different groups used to see the evolution of is shown. The root mean square (RMS) of the residuals for each dataset is also listed. RVs, radial velocities. Time is shown in Barycentric Julian Day (BJD) - 240,000.
(A) Lack of correlation between the residuals of the primary and secondary. (B) Posterior distribution of for the analyses of the primary, the secondary, and the full dataset compared to the prior distribution.
Corner plot of periods and masses consistent with the induced precession rate from anN-body fit. Regions of sensitivity are shown for (i) a 3-year astrometric campaign with the VLT in blue and (ii) 2 years of eclipse timing monitoring with 1-min timing precision (as was achieved with SPECULOOS) in red.
These are trajectories of test particles orbiting the binary. The red trajectories show the regions of libration, and the orange trajectories show the regions of circulation. The 584 stable orbits of 600 randomly drawn simulations from the posterior of theN-body fit are integrated, and the trajectories are overplotted in blue. Note that, because the simulations shown in blue are drawn from theN-body fit, they are for massive objects not test particles. Two different projections are shown.
Brown dwarfs are in red, and the planet is in blue. Direction to Earth relative to the binary is shown.
Figure showing residuals relative to the first epoch in meters per second (m/s) for the two stars, primary (circles) and secondary (squares). The blue points represent the RVs measured using the DOLBY-SD method (this work), and the red circles represent literature values from (27). (B) Zoom-in image of (A) so that the uncertainties on the DOLBY-SD data can be seen.
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