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A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266

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Demory, BO 
Pozuelos, FJ 
Gómez Maqueo Chew, Y 
Sabin, L 
Petrucci, R 


We report the discovery and characterisation of a super-Earth and a sub-Neptune transiting the bright (K=8.8), quiet, and nearby (37 pc) M3V dwarf TOI-1266. We validate the planetary nature of TOI-1266 b and c using four sectors of TESS photometry and data from the newly-commissioned 1-m SAINT-EX telescope located in San Pedro M'artir (Mexico). We also include additional ground-based follow-up photometry as well as high-resolution spectroscopy and high-angular imaging observations. The inner, larger planet has a radius of R=2.37−0.12+0.16 R and an orbital period of 10.9 days. The outer, smaller planet has a radius of R=1.56−0.13+0.15 R on an 18.8-day orbit. The data are found to be consistent with circular, co-planar and stable orbits that are weakly influenced by the 2:1 mean motion resonance. Our TTV analysis of the combined dataset enables model-independent constraints on the masses and eccentricities of the planets. We find planetary masses of Mp = 13.5−9.0+11.0 M (<36.8 M at 2-σ) for TOI-1266 b and 2.2−1.5+2.0 M (<5.7 M at 2-σ) for TOI-1266 c. We find small but non-zero orbital eccentricities of 0.09−0.05+0.06 (<0.21 at 2-σ) for TOI-1266 b and 0.04±0.03 (<0.10 at 2-σ) for TOI-1266 c. The equilibrium temperatures of both planets are of 413±20 K and 344±16 K, respectively, assuming a null Bond albedo and uniform heat redistribution from the day-side to the night-side hemisphere. The host brightness and negligible activity combined with the planetary system architecture and favourable planet-to-star radii ratios makes TOI-1266 an exquisite system for a detailed characterisation.



instrumentation: detectors, planets and satellites: detection

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Astronomy and Astrophysics

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EDP Sciences


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