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

TL;DR

This study confirms two exoplanets orbiting TOI-1752, including a lava-world and a habitable-zone sub-Neptune, using TESS data, ground follow-up, and machine learning validation methods.

Contribution

First validation of TOI-1752 b and c as planets, with detailed characterization and assessment of habitability and atmospheric observation potential.

Findings

TOI-1752 b is a 1.69 R⊕ planet with a 0.935-day orbit.

TOI-1752 c is a 2.29 R⊕ planet in the habitable zone.

TOI-1752 c is confirmed as a planet in the habitable zone.

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 toward 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, $103.02\pm0.34$ 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 multi-color 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 $1.69\pm0.07 R_{\oplus}$ and an orbital period of $0.935186^{+0.000001}_{-0.000002}$ days, and TOI-1752 c with a radius of $2.29^{+0.13}_{-0.14} R_{\oplus}$ and an orbital period of $32.7144\pm0.0004$ days. 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 (ESM) of up to $\sim8$.