The Neptunian desert is a distinct lack of Neptune-sized planets at short orbital periods, purportedly carved by photoevaporation and tidal circularisation following high-eccentricity migration. Constraining these processes and how they vary across different host-star spectral types requires detailed characterisation of the planets in the desert and around its boundaries. In this study, we confirm the planetary nature of a massive super-Neptune identified by TESS around the M0 dwarf TOI-672. We analysed photometry from TESS and ExTrA and precise radial velocity measurements taken with the recently commissioned Near-InfraRed Planet Searcher (NIRPS) and HARPS spectrographs. We measured a planetary orbital period of 3. 634 days, a radius of 5. 31^ +0. 24 _ -0. 26, R_⊕, and mass of +4. 5 _ -4. 4, M_⊕. Our findings place TOI-672 b within the Neptunian ridge, a pile-up of planets from 3--5 days at the Neptunian desert boundary. We used a novel approach to determine the desert boundaries in period-radius space and instellation-radius space, and for the first time, we compared the Neptunian desert boundaries for planets orbiting FGK versus M dwarf stars. We determined that the boundary ridge shifts slightly inwards from 3. 3 ± 1. 4, days for FGK host stars to 2. 2 ± 1. 0, days for M dwarf host stars. Statistically, these values do not significantly differ from each other, and the shift to shorter periods for M dwarf planets is smaller than what theoretical photoevaporation models predict. We also find that TOI-672, b is a single-planet system within the sensitivity limits of our RV and TTV datasets.
Osborn et al. (Wed,) studied this question.