VaTEST I: validation of sub-Saturn exoplanet TOI-181b in narrow orbit from its host star

Abstract

We present here a validation of sub-Saturn exoplanet TOI-181b orbiting a K spectral type star TOI-181 (mass: 0.822 ± 0.04 M_⊙, radius: 0.745 ± 0.02 R_⊙, temperature: 4994 ± 50 K) as a part of Validation of Transiting Exoplanets using Statistical Tools (VaTEST) project. TOI-181b is a planet with radius 6.95 ± 0.08 R_⊕, mass 46.16 ± 2.71 M_⊕, orbiting in a slightly eccentric orbit with eccentricity 0.15 ± 0.06 and semimajor axis of 0.054 ± 0.004 au, with an orbital period of 4.5320 ± 0.000002 d. The transit photometry data were collected using Transiting Exoplanet Survey Satellite (TESS) and spectroscopic data for radial velocity analysis were collected using The European Southern Observatory's (ESO) High Accuracy Radial Velocity Planet Searcher (HARPS) telescope. Based on the radial velocity best-fit model we measured RV semi-amplitude to be 20.56 ± 2.37 m s⁻¹. Additionally, we used VESPA and TRICERATOPS to compute the False Positive Probability (FPP), and the findings were FPP values of 1.68 × 10⁻¹⁴ and 3.81 × 10⁻⁰⁴, respectively, which are significantly lower than the 1 per cent threshold. The finding of TOI-181b is significant in the perspective of future work on the formation and migration history of analogous planetary systems since warm sub-Saturns are uncommon in the known sample of exoplanets.

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