Discovery and characterization of two exoplanets orbiting the metal-poor, solar-type star TOI-5788 with <i>TESS, CHEOPS</i> , and HARPS-N

ABSTRACT We present the discovery and characterization of two transiting exoplanets orbiting the metal-poor, solar-type star TOI-5788. From our analysis of six TESS sectors and a dedicated CHEOPS programme, we identify an inner planet (TOI-5788 b; $P = 6.340758\pm 0.000030\, d$) with radius $1.528\pm 0.075\, \mathrm{R_{\oplus }}$ and an outer planet (TOI-5788 c; $P = 16.213362\pm 0.000026\, d$) with radius $2.272\pm 0.039\, \mathrm{R_{\oplus }}$. We obtain 125 radial-velocity spectra from HARPS-N and constrain the masses of TOI-5788 b and c as $3.72\pm 0.94\, \mathrm{M_{\oplus }}$ and $6.4\pm 1.2\, \mathrm{M_{\oplus }}$, respectively. Although dynamical analyses indicate that a third planet could exist in a stable orbit between 8 and 14 d, we find no evidence of additional planets. Since the TOI-5788 system is one of the few systems with planets straddling the radius gap, and noting that there are even fewer such systems around metal-poor stars, it is a promising system to constrain planet formation theories. We therefore model the interior structures of both planets. We find that TOI-5788 b is consistent with being a rocky planet with almost no envelope, or having an atmosphere of a high mean molecular weight. We find that TOI-5788 c is consistent with both gas-dwarf and water-world hypotheses of mini-Neptune formation. We model the atmospheric evolution history of both planets. While both scenarios are consistent with the atmospheric evolution of TOI-5788 c, the gas-dwarf model is marginally preferred. The results of the atmospheric evolution analysis are not strongly dependent on stellar evolution. This makes the system a promising target to test internal structure and atmospheric evolution models.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2026-01-22
DOI
https://doi.org/10.1093/mnras/stag158
Primary Topic
Stellar, planetary, and galactic studies
Type
article
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article

Discovery and characterization of two exoplanets orbiting the metal-poor, solar-type star TOI-5788 with TESS, CHEOPS , and HARPS-N

Christina Hedges, Z. Garai, Daria Kubyshkina, M. Pinamonti et al.
Monthly Notices of the Royal Astronomical Society
Stellar, planetary, and galactic studies
article

Discovery and characterization of two exoplanets orbiting the metal-poor, solar-type star TOI-5788 with TESS, CHEOPS , and HARPS-N

Christina Hedges, Z. Garai, Daria Kubyshkina, M. Pinamonti, Soléne Ulmer-Moll, Ε. Πάλλη, J. Maldonado, G. Lacedelli, I. Ribas, Belinda Nicholson, Ben S Lakeland, Larissa Palethorpe, Annelies Mortier, C Mordasini, A Cameron, A F Martínez Fiorenzano, X Dumusque, S M O’Brien, M López-Morales, J A Egger, H P Osborn, L Fossati, D Ehrenreich, A C M Correia, D A Turner, C A Watson, D Gandolfi, A Castro-González, T G Wilson, P F L Maxted, M Stalport, A M Silva, R D Haywood, L A Buchhave, M Damasso, W Boschin, G Mantovan, S Udry, R Cosentino, G Szabó, N C Santos, L Malavolta, D Rapetti, A Vanderburg, M Gillon, M Lendl, S Filomeno, M Vezie, Z Essack
article en

Abstract

ABSTRACT We present the discovery and characterization of two transiting exoplanets orbiting the metal-poor, solar-type star TOI-5788. From our analysis of six TESS sectors and a dedicated CHEOPS programme, we identify an inner planet (TOI-5788 b; $P = 6.340758\pm 0.000030\, d$) with radius $1.528\pm 0.075\, \mathrm{R_{\oplus }}$ and an outer planet (TOI-5788 c; $P = 16.213362\pm 0.000026\, d$) with radius $2.272\pm 0.039\, \mathrm{R_{\oplus }}$. We obtain 125 radial-velocity spectra from HARPS-N and constrain the masses of TOI-5788 b and c as $3.72\pm 0.94\, \mathrm{M_{\oplus }}$ and $6.4\pm 1.2\, \mathrm{M_{\oplus }}$, respectively. Although dynamical analyses indicate that a third planet could exist in a stable orbit between 8 and 14 d, we find no evidence of additional planets. Since the TOI-5788 system is one of the few systems with planets straddling the radius gap, and noting that there are even fewer such systems around metal-poor stars, it is a promising system to constrain planet formation theories. We therefore model the interior structures of both planets. We find that TOI-5788 b is consistent with being a rocky planet with almost no envelope, or having an atmosphere of a high mean molecular weight. We find that TOI-5788 c is consistent with both gas-dwarf and water-world hypotheses of mini-Neptune formation. We model the atmospheric evolution history of both planets. While both scenarios are consistent with the atmospheric evolution of TOI-5788 c, the gas-dwarf model is marginally preferred. The results of the atmospheric evolution analysis are not strongly dependent on stellar evolution. This makes the system a promising target to test internal structure and atmospheric evolution models.

Monthly Notices of the Royal Astronomical SocietyVol. 546(4)
University of Geneva (CH), University of Rome Tor Vergata (IT), University of Bern (CH), Leiden University (NL), Queen's University Belfast (GB), Ames Research Center (US), Space Telescope Science Institute (US), Goddard Space Flight Center (US), Universities Space Research Association (US), Austrian Academy of Sciences (AT), University of Padua (IT), University of Liège (BE), Universidad de La Laguna (ES), University of St Andrews (GB), University of New Mexico (US), Universidade do Porto (PT), University of Southern Queensland (AU), Slovak Academy of Sciences (SK), University of Exeter (GB), Astronomical Observatory of Rome (IT), ETH Zurich (CH), University of Warwick (GB), Institute of Astrophysics and Space Sciences (PT), Institut d'Estudis Espacials de Catalunya (ES), Osservatorio Astrofisico di Torino (IT), Royal Observatory (GB), Institute of Space Sciences (ES), Université Bourgogne Franche-Comté (FR), Osservatorio Astrofisico di Catania (IT), Center for Astrophysics Harvard & Smithsonian (US), Osservatorio Astronomico di Palermo (IT), Instituto de Astrofísica de Canarias (ES), Astronomical Institute of the Slovak Academy of Sciences (SK), Szent Imre Egyetemi Oktatókórház (HU), Osservatorio Astronomico di Padova (IT), Telescopio Nazionale Galileo (ES), European Space Research and Technology Centre (NL), UK Astronomy Technology Centre (GB), University of Turin (IT), Keele University (GB), Massachusetts Institute of Technology (US), University of Coimbra (PT), University of Birmingham (GB), International Space Science Institute (CH), Sapienza University of Rome (IT), Technical University of Denmark (DK), University of Edinburgh (GB)
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