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

Abstract

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 $P=39.6299\pm 0.29$ d and a minimum mass $M\sin i=8.11\pm 1.63M_{\oplus }$. 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 $1.69R_{\oplus }$ 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 $i<89.3^{\circ }$. With an incident stellar flux $S_{\mathrm{eff}}\approx 0.889S_{\oplus }$ and bolometric luminosity $L_{\ast }=0.0273\pm 0.0023L_{\odot }$, 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.

18 pages, 4 figures, 2 tables. Published on OEJV