Detection and characterization of the temperate super-earth Gliese 48 b

Gliese 48 is an M3.5V red dwarf exhibiting significant magnetic activity and a stellar rotation period of 51.5 d. In this work, we present a systematic re-analysis of radial velocities (RV) from CARMENES and decade-long HIRES observations, integrated with TESS space-based photometry. We identify a planet of undetermined composition, Gliese 48 b, with an orbital period P = 39.6299 plus or minus 0.29 d and a minimum mass M i = 8.11 plus or minus 1.63 M. The planetary nature of the signal is confirmed by its temporal coherence over a 15-year baseline and its achromaticity between visible and near-infrared channels. TESS photometry from Sectors 18, 19, 24, and 25 (218.6 d total baseline, 66,983 cadences) reveals no transit at P = 39.63 d (FAP > 10%, BLS). An injection-and-recovery test demonstrates that a 1287 ppm transit signal corresponding to a minimum-radius 1.69 R planet would have been detected with Signal-to-Pink-Noise Ratio SPNR > 7, ruling out a transiting geometry with high confidence. The orbital inclination is constrained to i < 89.3. With an incident stellar flux S eff about 0.889 S and bolometric luminosity L* = 0.0273 plus or minus 0.0023 L, Gliese 48 b lies near the inner edge of the Conservative Habitable Zone and within the Optimistic HZ, making it one of the most astrobiologically compelling temperate Super-Earths orbiting an M-dwarf.