<i>TESS</i> discovery of a sub-Neptune orbiting a mid-M dwarf TOI-2136

ABSTRACT We present the discovery of TOI-2136 b, a sub-Neptune planet transiting nearby M4.5V-type star every 7.85 d, identified through photometric measurements from Transiting Exoplanet Survey Satellite (TESS) mission. The host is located 33 pc away with radius R* = 0.34 ± 0.02 R?, mass $0.34\pm \, \mathrm{M}_{\odot }$, and an effective temperature 3342 100 K. estimate its stellar rotation period to be 75 5 d based on archival long-term photometry. confirm characterize series ground-based multiwavelength photometry, high-angular-resolution imaging observations, precise radial velocities Canada–France–Hawaii Telescope (CFHT)/SpectroPolarimètre InfraROUge (SPIRou). Our joint analysis reveals that has 2.20 0.17 R? 6.4 2.4 M?. b are consistent broad range compositions, water-ice gas-dominated worlds. falls close valley for M dwarfs predicted by thermally driven atmospheric mass-loss models, making it interesting target future studies interior structure properties.