K2-370 b: a strongly irradiated sub-Neptune transiting a very active solar-type star

ABSTRACT We report on the detailed characterization of K2-370 b, a transiting sub-Neptune on a 2.14-d orbit around the chromospherically active G-type dwarf HD 284521 ($T_\mathrm{eff} = 5662\pm 44$ K, $\lt \log R^\prime _{\rm HK}\gt =-4.49$). The system parameters are derived based on a global fit to K2, TESS and CHEOPS photometry, and HARPS-N and HARPS radial velocities (RVs). A Gaussian process regression analysis is performed simultaneously to the orbital fit of the RVs of K2-370 to effectively model the strong stellar rotation signal with a period of $13.5\pm 0.05$ d and measure the planetary RV signal with semi-amplitude $K_{\rm b}=5.6\pm 0.7$ m s$^{-1}$. We find that K2-370 b has a radius of $2.67\pm 0.05$ ${\rm R}_{\rm{\oplus }}$ and a mass of $11.1\pm 1.4$ ${\rm M}_{\rm{\oplus }}$. With an estimated equilibrium temperature $T_\mathrm{eq}\sim 1480$ K, K2-370 b is the second-hottest sub-Neptune with a highly precise mass determination around primaries with $T_\mathrm{eff}\gt 5500$ K. The resulting density of $3.2\pm 0.4$ g cm$^{-3}$ implies that K2-370 b either retains a significant ($\sim 2~{{\ \rm per\ cent}}$ by mass) H-rich atmosphere or its interior contains a high ($\sim 40~{{\ \rm per\ cent}}$) water–mass fraction.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2024-10-11
DOI
https://doi.org/10.1093/mnras/stae2323
Citations
2
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
0.66

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article

K2-370 b: a strongly irradiated sub-Neptune transiting a very active solar-type star

A. S. Bonomo, A. Collier Cameron, L. Malavolta, Annelies Mortier et al.
2 citations
Monthly Notices of the Royal Astronomical Society
Astro and Planetary Science
0.66
article

K2-370 b: a strongly irradiated sub-Neptune transiting a very active solar-type star

A. S. Bonomo, A. Collier Cameron, L. Malavolta, Annelies Mortier, M. Pinamonti, Jorge Fernández Fernández, A. Anna John, David W. Latham, Daniel Bayliss, D. J. Armstrong, A. Ghedina, Alessandro Sozzetti, M. Damasso, X Dumusque, Andrew Vanderburg, Marcelo Aron Fetzner Keniger, P. J. Wheatley, Ares Osborn, F. Pepe, Louise D. Nielsen, Patricio E. Cubillos, T. G. Wilson, S. Udry, Alix Violet Freckelton, P. A. Strøm, R Rabino
article en
2 citations

Abstract

ABSTRACT We report on the detailed characterization of K2-370 b, a transiting sub-Neptune on a 2.14-d orbit around the chromospherically active G-type dwarf HD 284521 ($T_\mathrm{eff} = 5662\pm 44$ K, $\lt \log R^\prime _{\rm HK}\gt =-4.49$). The system parameters are derived based on a global fit to K2, TESS and CHEOPS photometry, and HARPS-N and HARPS radial velocities (RVs). A Gaussian process regression analysis is performed simultaneously to the orbital fit of the RVs of K2-370 to effectively model the strong stellar rotation signal with a period of $13.5\pm 0.05$ d and measure the planetary RV signal with semi-amplitude $K_{\rm b}=5.6\pm 0.7$ m s$^{-1}$. We find that K2-370 b has a radius of $2.67\pm 0.05$ ${\rm R}_{\rm{\oplus }}$ and a mass of $11.1\pm 1.4$ ${\rm M}_{\rm{\oplus }}$. With an estimated equilibrium temperature $T_\mathrm{eq}\sim 1480$ K, K2-370 b is the second-hottest sub-Neptune with a highly precise mass determination around primaries with $T_\mathrm{eff}\gt 5500$ K. The resulting density of $3.2\pm 0.4$ g cm$^{-3}$ implies that K2-370 b either retains a significant ($\sim 2~{{\ \rm per\ cent}}$ by mass) H-rich atmosphere or its interior contains a high ($\sim 40~{{\ \rm per\ cent}}$) water–mass fraction.

Monthly Notices of the Royal Astronomical SocietyVol. 535(1)
University of Geneva (CH), Austrian Academy of Sciences (AT), University of Padua (IT), University of St Andrews (GB), Politecnico di Torino (IT), University of Warwick (GB), Space Research Institute (AT), Osservatorio Astrofisico di Torino (IT), Center for Astrophysics Harvard & Smithsonian (US), Osservatorio Astronomico di Padova (IT), Massachusetts Institute of Technology (US), University of Birmingham (GB), Ludwig-Maximilians-Universität München (DE), McMaster University (CA)
National Science Foundation, National Aeronautics and Space Administration, California Institute of Technology, UK Space Agency, UK Research and Innovation, Diabetes Patient Advocacy Coalition, European Space Agency, European Commission, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Agenzia Spaziale Italiana, Ames Research Center, Science and Technology Facilities Council, H2020 European Research Council
Openalex Percentile: Top 28%
Astro and Planetary Science
0.66
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