A gem system with a lava world and a habitable zone sub-Neptune orbiting TOI–1752

ABSTRACT The Transiting Exoplanet Survey Satellite (TESS) has delivered a large number of transiting planet candidates around nearby stars by identifying periodic decreases in stellar brightness. Establishing the planetary nature of these signals and determining their fundamental properties is a necessary step towards detailed studies of their internal structure, atmospheres, and formation pathways. In this work, we investigate the planetary nature of the TOI–1752 system (M1 V, $103.02\pm 0.34$ pc), which hosts two TESS candidates: TOI–1752 b, a short-period object consistent with a lava-world scenario, and TOI–1752 c, a sub-Neptune-size planet candidate located in the optimistic habitable zone. We obtained ground-based multicolour photometric follow-up observations of TOI–1752, which we combined with TESS photometry to assess the nature of both signals. We performed a formal statistical validation using the TRICERATOPS framework, while independently vetting the candidates with the neural-network-based classifier WATSON-Net, which provides a machine-learning assessment of their planetary likelihood based on light-curve morphology, centroid diagnostics, and auxiliary vetting features. We validate TOI–1752 b as a bona fide planet with a radius of $1.69\pm 0.07\, R_{\oplus }$ and an orbital period of $0.935186^{+0.000001}_{-0.000002}$ d, and TOI–1752 c with a radius of $2.29^{+0.13}_{-0.14}\, R_{\oplus }$ and an orbital period of $32.7144\pm 0.0004$ d. The combined analysis confirms TOI–1752 as a new planetary system, places TOI–1752 c within the optimistic habitable zone of its host star, and identifies TOI–1752 b as a promising target for atmospheric characterization, with an estimated emission spectroscopy metric of up to $\sim 8$.