TOI-5005 b: A super-Neptune in the savanna near the ridge

Context . The Neptunian desert and savanna have recently been found to be separated by a ridge, an overdensity of planets in the period range of ≃3–5 days. These features are thought to be shaped by dynamical and atmospheric processes. However, their roles are not yet well understood. Aims . Our aim was to confirm and characterize the super-Neptune TESS candidate TOI-5005.01, which orbits a moderately bright (V = 11.8) solar-type star (G2 V) with an orbital period of 6.3 days. With these properties, TOI-5005.01 is located in the Neptunian savanna near the ridge. Methods . We used Bayesian inference to analyse 38 HARPS radial velocity measurements, three sectors of TESS photometry, and two PEST and TRAPPIST-South transits. We tested a set of models involving eccentric and circular orbits, long-term drifts, and Gaussian processes to account for correlated stellar and instrumental noise. We computed the Bayesian evidence to find the model that best represents our dataset and infer the orbital and physical properties of the system. Results . We confirm TOI-5005 b to be a transiting super-Neptune with a radius of R p = 6.25 ± 0.24 R ⊕ ( R p = 0.558 ± 0.021 R J ) and a mass of M p = 32.7 ± 5.9 M ⊕ ( M p = 0.103 ± 0.018 M J ), which corresponds to a mean density of ρ p = 0.74 ± 0.16 g cm −3 . Our internal structure modelling indicates that the core mass fraction (CMF = 0.74 −0.45 +0.05 ) and envelope metal mass fraction ( Z env = 0.08 −0.06 +0.41 ) of TOI-5005 b are degenerate, but the overall metal mass fraction is well constrained to a value slightly lower than that of Neptune and Uranus ( Z planet = 0.76 −0.11 +0.04 ). The Z planet / Z star ratio is consistent with the well-known mass-metallicity relation, which suggests that TOI-5005 b was formed via core accretion. We also estimated the present-day atmospheric mass-loss rate of TOI-5005 b, but found contrasting predictions depending on the choice of photoevaporation model (0.013 ± 0.008 M ⊕ Gyr −1 vs. 0.17 ± 0.12 M ⊕ Gyr −1 ). At a population level, we find statistical evidence ( p -value = 0.0092 −0.0066 +0.0184 ) that planets in the savanna such as TOI-5005 b tend to show lower densities than planets in the ridge, with a dividing line around 1 g cm −3 , which supports the hypothesis of different evolutionary pathways populating the two regimes. Conclusions . TOI-5005 b is located in a region of the period-radius space that is key to studying the transition between the Neptunian ridge and the savanna. It orbits the brightest star of all such planets known today, which makes it a target of interest for atmospheric and orbital architecture observations that will bring a clearer picture of its overall evolution.

Authors

Institutions

Publication Details

Journal
Astronomy and Astrophysics
Published
2024-10-16
DOI
https://doi.org/10.1051/0004-6361/202451656
Citations
22
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
7.29

Funders

Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

TOI-5005 b: A super-Neptune in the savanna near the ridge

M. Ghachoui, D.A. Caldwell, D.J. Armstrong, M. Gillon et al.
22 citations
Astronomy and Astrophysics
Astro and Planetary Science
7.29
article

TOI-5005 b: A super-Neptune in the savanna near the ridge

M. Ghachoui, D.A. Caldwell, D.J. Armstrong, M. Gillon, N. Law, Z. Benkhaldoun, F. J. Pozuelos, A. Moya, K. Barkaoui, S. Seager, A. C. M. Correia, F. Bouchy, N.C. Santos, N. Schanche, V. Adibekyan, S. Gandhi, Z. Essack, M. Damasso, A. Castro-González, Mathilde Timmermans, C. Ziegler, L. D. Nielsen, Marcelo Aron Fetzner Keniger, J.N. Winn, L. Acuña, R. Hounsell, D. Barrado, K. A. Collins, E. Jehin, S. C. C. Barros, Avantika Mann, V. Bourrier, J. Lillo-Box, J.M. Jenkins, T.-G. Tan, E. Delgado-Mena, Artyom Aguichine, S. G. Sousa, César Briceño, J. Villaseñor, Cristilyn N. Watkins
article en
22 citations

Abstract

Context . The Neptunian desert and savanna have recently been found to be separated by a ridge, an overdensity of planets in the period range of ≃3–5 days. These features are thought to be shaped by dynamical and atmospheric processes. However, their roles are not yet well understood. Aims . Our aim was to confirm and characterize the super-Neptune TESS candidate TOI-5005.01, which orbits a moderately bright (V = 11.8) solar-type star (G2 V) with an orbital period of 6.3 days. With these properties, TOI-5005.01 is located in the Neptunian savanna near the ridge. Methods . We used Bayesian inference to analyse 38 HARPS radial velocity measurements, three sectors of TESS photometry, and two PEST and TRAPPIST-South transits. We tested a set of models involving eccentric and circular orbits, long-term drifts, and Gaussian processes to account for correlated stellar and instrumental noise. We computed the Bayesian evidence to find the model that best represents our dataset and infer the orbital and physical properties of the system. Results . We confirm TOI-5005 b to be a transiting super-Neptune with a radius of R p = 6.25 ± 0.24 R ⊕ ( R p = 0.558 ± 0.021 R J ) and a mass of M p = 32.7 ± 5.9 M ⊕ ( M p = 0.103 ± 0.018 M J ), which corresponds to a mean density of ρ p = 0.74 ± 0.16 g cm −3 . Our internal structure modelling indicates that the core mass fraction (CMF = 0.74 −0.45 +0.05 ) and envelope metal mass fraction ( Z env = 0.08 −0.06 +0.41 ) of TOI-5005 b are degenerate, but the overall metal mass fraction is well constrained to a value slightly lower than that of Neptune and Uranus ( Z planet = 0.76 −0.11 +0.04 ). The Z planet / Z star ratio is consistent with the well-known mass-metallicity relation, which suggests that TOI-5005 b was formed via core accretion. We also estimated the present-day atmospheric mass-loss rate of TOI-5005 b, but found contrasting predictions depending on the choice of photoevaporation model (0.013 ± 0.008 M ⊕ Gyr −1 vs. 0.17 ± 0.12 M ⊕ Gyr −1 ). At a population level, we find statistical evidence ( p -value = 0.0092 −0.0066 +0.0184 ) that planets in the savanna such as TOI-5005 b tend to show lower densities than planets in the ridge, with a dividing line around 1 g cm −3 , which supports the hypothesis of different evolutionary pathways populating the two regimes. Conclusions . TOI-5005 b is located in a region of the period-radius space that is key to studying the transition between the Neptunian ridge and the savanna. It orbits the brightest star of all such planets known today, which makes it a target of interest for atmospheric and orbital architecture observations that will bring a clearer picture of its overall evolution.

Astronomy and AstrophysicsVol. 691
University of North Carolina at Chapel Hill (US), University of Geneva (CH), Cadi Ayyad University (MA), Ames Research Center (US), Centre National de la Recherche Scientifique (FR), Planetary Science Institute (US), Goddard Space Flight Center (US), University of Liège (BE), Universitat de València (ES), University of New Mexico (US), Universidade do Porto (PT), University of California, Santa Cruz (US), Princeton University (US), Stephen F. Austin State University (US), Université Paris Sciences et Lettres (FR), Observatoire de Paris (FR), University of Warwick (GB), Institute of Astrophysics and Space Sciences (PT), Osservatorio Astrofisico di Torino (IT), Max Planck Institute for Astronomy (DE), Center for Astrophysics Harvard & Smithsonian (US), Centro de Astrobiología (ES), Instituto de Astrofísica de Canarias (ES), Cerro Tololo Inter-American Observatory (CL), Instituto de Astrofísica de Andalucía (ES), American Institute of Aeronautics and Astronautics (US), Institut de Mécanique Céleste et de Calcul des Éphémérides (FR), Massachusetts Institute of Technology (US), University of Maryland, College Park (US), University of Coimbra (PT), University of Maryland, Baltimore County (US), Ludwig-Maximilians-Universität München (DE), Search for Extraterrestrial Intelligence (US), Universidad Politécnica de Madrid (ES)
National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, Space Telescope Science Institute, European Space Agency, European Commission, Indian Council of Agricultural Research, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Fonds De La Recherche Scientifique - FNRS, Fédération Wallonie-Bruxelles, Generalitat Valenciana, Nuclear Safety and Security Commission, Ministerio de Ciencia e Innovación, Fondation Francqui - Stichting, Instituto de Astrofísica de Andalucía, Ames Research Center, Goddard Space Flight Center, Science Mission Directorate, Fundação para a Ciência e a Tecnologia, Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture, European Regional Development Fund, Agencia Estatal de Investigación
Openalex Percentile: Top 2%
Astro and Planetary Science
7.29
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.