TOI-1743 b, TOI-5799 b, TOI-5799 c, and TOI-6223 b: TESS discovery and validation of four super-Earth to Neptune-sized planets around M dwarfs

We present the discovery by the TESS mission of one transiting Neptune-sized planet, TOI-6223 b, and two transiting super-Earths, TOI-1743 b and TOI-5799 b. We validate these planets using a statistical validation method, multi-color light curves, and other ancillary observations. We combined TESS and ground-based photometric data to constrain the physical properties of the planets. TOI-6223 b is slightly larger than Neptune Rp = 5.12−0.25+0.24 R⊕) orbiting an early M dwarf in 3.86 days, and it has an equilibrium temperature of Teq = 714 ± 14 K. TOI-1743 b orbits its mid-dwarf star every 4.27 days. It has a radius of Rp = 1.83−0.10+0.11 R⊕ and an equilibrium temperature of Teq = 485−13+14. TOI-5799 b has a radius of Rp = 1.733−0.090+0.096 R⊕ and an equilibrium temperature of Teq = 505 ± 16 K. It orbit around an M2 dwarf in 4.17 days. We also present the discovery of an additional transiting planet, TOI-5799 c, which we identified in the TESS data and validated using the SHERLOCK pipeline. TOI-5799 c is a super-Earth with a radius of Rp = 1.76−0.10+0.11 R⊕. Its orbital period and its equilibrium temperature are 14.01 days and Teq = 337 ± 11 K, respectively, which place it near the inner edge of the habitable zone of its star. We show that these planets are suitable for both radial velocity follow-up and atmospheric characterization. They orbit bright (<11 Kmag) early M dwarfs, making them accessible for precise mass measurements. The combination of the planet sizes and stellar brightness of their host stars also make them suitable targets for atmospheric exploration with the JWST. Such studies may provide insights into planet formation and evolution, as TOI-1743 b, TOI-5799 b, and TOI-5799 c lie within what is known as the radius valley, while TOI-6223 b is located on the Neptunian ridge in the period-radius plane.