TOI-283 b: A transiting mini-Neptune in a 17.6-day orbit discovered with TESS and ESPRESSO

Context . Super-Earths and mini-Neptunes are missing from our Solar System, yet they appear to be the most abundant planetary types in our Galaxy. A detailed characterization of key planets within this population is important for understanding the formation mechanisms of rocky and gas giant planets and the diversity of planetary interior structures. Aims . In 2019, NASA’s TESS satellite found a transiting planet candidate in a 17.6-day orbit around the star TOI-283. We started radial velocity (RV) follow-up observations with ESPRESSO to obtain a mass measurement. Mass and radius are measurements critical for planetary classification and internal composition modeling. Methods . We used ESPRESSO spectra to derive the stellar parameters of the planet candidate host star TOI-283. We then performed a joint analysis of the photometric and RV data of this star, using Gaussian processes to model the systematic noise present in both datasets. Results . We find that the host is a bright K-type star ( d = 82.4 pc, T eff = 5213 ± 70 K, V = 10.4 mag) with a mass and radius of M ⋆ = 0.80 ± 0.01 M ⊙ and R ⋆ = 0.85 ± 0.03 R ⊙ . The planet has an orbital period of P = 17.617 days, a size of R p = 2.34 ± 0.09 R ⊕ , and a mass of M p = 6.54 ± 2.04 M ⊕ . With an equilibrium temperature of ~600 K and a bulk density of ρ p = 2.81 ± 0.93 g cm −3 , this planet is positioned in the mass-radius diagram where planetary models predict H 2 O- and H/He-rich envelopes. The ESPRESSO RV data also reveal a long-term trend that is probably related to the star’s activity cycle. Further RV observations are required to confirm whether this signal originates from stellar activity or another planetary body in the system.

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Journal
Astronomy and Astrophysics
Published
2025-10-15
DOI
https://doi.org/10.1051/0004-6361/202553968
Primary Topic
Astro and Planetary Science
Type
article
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article

TOI-283 b: A transiting mini-Neptune in a 17.6-day orbit discovered with TESS and ESPRESSO

N. J. Nunes, E. Furlan, D.A. Caldwell, F. Murgas et al.
Astronomy and Astrophysics
Astro and Planetary Science
article

TOI-283 b: A transiting mini-Neptune in a 17.6-day orbit discovered with TESS and ESPRESSO

N. J. Nunes, E. Furlan, D.A. Caldwell, F. Murgas, D. Bossini, J.N. Winn, J.M. Jenkins, F. Pepe, C. Ziegler, F. J. Pozuelos, Cristilyn N. Watkins, A. Mehner, P. Figueira, K.I. Collins, M. R. Zapatero Osorio, S. Cristiani, F. Bouchy, C. J. A. P. Martins, B. Lavie, N.C. Santos, J. Korth, H.M. Relles, A.W. Mann, P. Molaro, V. Adibekyan, A. Suárez Mascareño, K.A. Collins, Alessandro Sozzetti, H. Parviainen, D. Ciardi, C. Lovis, A. Castro-González, Y. Alibert, Colin Littlefield, N.J. Scott, S. Seager, Catherine A. Clark, X. Dumusque, Zachary Hartman, S.B. Howell, S. Udry, D. Ehrenreich, R. Rébolo, N. Law, J. I. Gónzalez Hernández, Mélissa J. Hobson, C. Briceño, G. Lo Curto, R. Génova Santos, E. Pallé, S. G. Sousa, G. Micela, Carlos Allende Prieto, C. Gnilka
article en

Abstract

Context . Super-Earths and mini-Neptunes are missing from our Solar System, yet they appear to be the most abundant planetary types in our Galaxy. A detailed characterization of key planets within this population is important for understanding the formation mechanisms of rocky and gas giant planets and the diversity of planetary interior structures. Aims . In 2019, NASA’s TESS satellite found a transiting planet candidate in a 17.6-day orbit around the star TOI-283. We started radial velocity (RV) follow-up observations with ESPRESSO to obtain a mass measurement. Mass and radius are measurements critical for planetary classification and internal composition modeling. Methods . We used ESPRESSO spectra to derive the stellar parameters of the planet candidate host star TOI-283. We then performed a joint analysis of the photometric and RV data of this star, using Gaussian processes to model the systematic noise present in both datasets. Results . We find that the host is a bright K-type star ( d = 82.4 pc, T eff = 5213 ± 70 K, V = 10.4 mag) with a mass and radius of M ⋆ = 0.80 ± 0.01 M ⊙ and R ⋆ = 0.85 ± 0.03 R ⊙ . The planet has an orbital period of P = 17.617 days, a size of R p = 2.34 ± 0.09 R ⊕ , and a mass of M p = 6.54 ± 2.04 M ⊕ . With an equilibrium temperature of ~600 K and a bulk density of ρ p = 2.81 ± 0.93 g cm −3 , this planet is positioned in the mass-radius diagram where planetary models predict H 2 O- and H/He-rich envelopes. The ESPRESSO RV data also reveal a long-term trend that is probably related to the star’s activity cycle. Further RV observations are required to confirm whether this signal originates from stellar activity or another planetary body in the system.

Astronomy and AstrophysicsVol. 703
University of North Carolina at Chapel Hill (US), University of Geneva (CH), University of Bern (CH), Ames Research Center (US), Consejo Superior de Investigaciones Científicas (ES), Universidad de La Laguna (ES), George Mason University (US), Universidade do Porto (PT), Lund University (SE), Princeton University (US), Stephen F. Austin State University (US), NASA Exoplanet Science Institute (US), Trieste Astronomical Observatory (IT), Institute of Astrophysics and Space Sciences (PT), Kavli Institute for Particle Astrophysics and Cosmology (US), Osservatorio Astrofisico di Torino (IT), Centro de Astrofísica da Universidade do Porto (PT), Bay Area Environmental Research Institute (US), Southern Astrophysical Research Telescope (CL), Gemini South Observatory (CL), Center for Astrophysics Harvard & Smithsonian (US), Osservatorio Astronomico di Palermo (IT), Centro de Astrobiología (ES), Instituto de Astrofísica de Canarias (ES), NSF NOIRLab (US), Instituto de Astrofísica de Andalucía (ES), Institute of Psychology (RU), American Institute of Aeronautics and Astronautics (US), Massachusetts Institute of Technology (US), Search for Extraterrestrial Intelligence (US)
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