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

A Sozzetti; M Damasso; J Fernández Fernández; A Mortier; A Anna John; P E Cubillos; T G Wilson; M Pinamonti; L Nielsen; A S Bonomo; A V Freckelton; A Collier Cameron; D Armstrong; A Vanderburg; D Bayliss; X Dumusque; A Ghedina; M A F Keniger; D W Latham; M López Morales; L Malavolta; A Osborn; F Pepe; R Rabino; P A Strøm; S Udry; P Wheatley

doi:10.1093/mnras/stae2323

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

A Sozzetti^*, M Damasso, J Fernández Fernández, A Mortier, A Anna John, P E Cubillos, T G Wilson, M Pinamonti, L Nielsen, A S Bonomo, A V Freckelton, A Collier Cameron, D Armstrong, A Vanderburg, D Bayliss, X Dumusque, A Ghedina, M A F Keniger, D W Latham, M López MoralesL Malavolta, A Osborn, F Pepe, R Rabino, P A Strøm, S Udry, P Wheatley

^*Corresponding author for this work

Physics and Astronomy

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Abstract

We report on the detailed characterisation of K2-370 b, a transiting sub-Neptune on a 2.14-d orbit around the chromospherically active G-type dwarf HD 284521 (𝑇_eff = 5662 ± 44 K, < log 𝑅′_𝐻𝐾 >= −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 ± 0.05 d and measure the planetary RV signal with semi-amplitude 𝐾_𝑏 = 5.6 ± 0.7 m s⁻¹. We find that K2-370 b has a radius of 2.67 ± 0.05 𝑅_⊕ and a mass of 11.1 ± 1.4 𝑀_⊕. With an estimated equilibrium temperature 𝑇_eq ∼ 1480 K, K2-370 b is the second-hottest sub-Neptune with a highly precise mass determination around primaries with 𝑇_eff > 5500 K. The resulting density of 3.2±0.4 g cm⁻³ implies that K2-370 b either retains a significant (∼ 2 per cent by mass) H-rich atmosphere or its interior contains a high (∼ 40 per cent) water-mass fraction.

Original language	English
Pages (from-to)	531-550
Number of pages	20
Journal	Monthly Notices of the Royal Astronomical Society
Volume	535
Issue number	1
Early online date	11 Oct 2024
DOIs	https://doi.org/10.1093/mnras/stae2323
Publication status	Published - Nov 2024

Bibliographical note

Corrected and typeset: 30 October 2024.

Keywords

methods: miscellaneous
planets and satellites: composition
stars: individual: HD 284521 (K2-370)
techniques: radial velocities
techniques: photometric

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Sozzetti, A., Damasso, M., Fernández, J. F., Mortier, A., John, A. A., Cubillos, P. E., Wilson, T. G., Pinamonti, M., Nielsen, L., Bonomo, A. S., Freckelton, A. V., Cameron, A. C., Armstrong, D., Vanderburg, A., Bayliss, D., Dumusque, X., Ghedina, A., Keniger, M. A. F., Latham, D. W., ... Wheatley, P. (2024). K2-370 b: a strongly irradiated sub-Neptune transiting a very active solar-type star. Monthly Notices of the Royal Astronomical Society, 535(1), 531-550. https://doi.org/10.1093/mnras/stae2323

@article{078d5f93584243b699d82d4f9f211808,

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

abstract = "We report on the detailed characterisation of K2-370 b, a transiting sub-Neptune on a 2.14-d orbit around the chromospherically active G-type dwarf HD 284521 (𝑇eff = 5662 ± 44 K, < log 𝑅′𝐻𝐾 >= −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 ± 0.05 d and measure the planetary RV signal with semi-amplitude 𝐾𝑏 = 5.6 ± 0.7 m s−1. We find that K2-370 b has a radius of 2.67 ± 0.05 𝑅⊕ and a mass of 11.1 ± 1.4 𝑀⊕. With an estimated equilibrium temperature 𝑇eq ∼ 1480 K, K2-370 b is the second-hottest sub-Neptune with a highly precise mass determination around primaries with 𝑇eff > 5500 K. The resulting density of 3.2±0.4 g cm−3 implies that K2-370 b either retains a significant (∼ 2 per cent by mass) H-rich atmosphere or its interior contains a high (∼ 40 per cent) water-mass fraction.",

keywords = "methods: miscellaneous, planets and satellites: composition, stars: individual: HD 284521 (K2-370), techniques: radial velocities, techniques: photometric",

author = "A Sozzetti and M Damasso and Fern{\'a}ndez, \{J Fern{\'a}ndez\} and A Mortier and John, \{A Anna\} and Cubillos, \{P E\} and Wilson, \{T G\} and M Pinamonti and L Nielsen and Bonomo, \{A S\} and Freckelton, \{A V\} and Cameron, \{A Collier\} and D Armstrong and A Vanderburg and D Bayliss and X Dumusque and A Ghedina and Keniger, \{M A F\} and Latham, \{D W\} and Morales, \{M L{\'o}pez\} and L Malavolta and A Osborn and F Pepe and R Rabino and Str{\o}m, \{P A\} and S Udry and P Wheatley",

note = "Corrected and typeset: 30 October 2024. ",

year = "2024",

month = nov,

doi = "10.1093/mnras/stae2323",

language = "English",

volume = "535",

pages = "531--550",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "SIPRI/Oxford University Press",

number = "1",

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Sozzetti, A, Damasso, M, Fernández, JF, Mortier, A , John, AA, Cubillos, PE, Wilson, TG, Pinamonti, M, Nielsen, L, Bonomo, AS, Freckelton, AV, Cameron, AC, Armstrong, D, Vanderburg, A, Bayliss, D, Dumusque, X, Ghedina, A, Keniger, MAF, Latham, DW, Morales, ML, Malavolta, L, Osborn, A, Pepe, F, Rabino, R, Strøm, PA, Udry, S & Wheatley, P 2024, 'K2-370 b: a strongly irradiated sub-Neptune transiting a very active solar-type star', Monthly Notices of the Royal Astronomical Society, vol. 535, no. 1, pp. 531-550. https://doi.org/10.1093/mnras/stae2323

TY - JOUR

T1 - K2-370 b

T2 - a strongly irradiated sub-Neptune transiting a very active solar-type star

AU - Sozzetti, A

AU - Damasso, M

AU - Fernández, J Fernández

AU - Mortier, A

AU - John, A Anna

AU - Cubillos, P E

AU - Wilson, T G

AU - Pinamonti, M

AU - Nielsen, L

AU - Bonomo, A S

AU - Freckelton, A V

AU - Cameron, A Collier

AU - Armstrong, D

AU - Vanderburg, A

AU - Bayliss, D

AU - Dumusque, X

AU - Ghedina, A

AU - Keniger, M A F

AU - Latham, D W

AU - Morales, M López

AU - Malavolta, L

AU - Osborn, A

AU - Pepe, F

AU - Rabino, R

AU - Strøm, P A

AU - Udry, S

AU - Wheatley, P

N1 - Corrected and typeset: 30 October 2024.

PY - 2024/11

Y1 - 2024/11

N2 - We report on the detailed characterisation of K2-370 b, a transiting sub-Neptune on a 2.14-d orbit around the chromospherically active G-type dwarf HD 284521 (𝑇eff = 5662 ± 44 K, < log 𝑅′𝐻𝐾 >= −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 ± 0.05 d and measure the planetary RV signal with semi-amplitude 𝐾𝑏 = 5.6 ± 0.7 m s−1. We find that K2-370 b has a radius of 2.67 ± 0.05 𝑅⊕ and a mass of 11.1 ± 1.4 𝑀⊕. With an estimated equilibrium temperature 𝑇eq ∼ 1480 K, K2-370 b is the second-hottest sub-Neptune with a highly precise mass determination around primaries with 𝑇eff > 5500 K. The resulting density of 3.2±0.4 g cm−3 implies that K2-370 b either retains a significant (∼ 2 per cent by mass) H-rich atmosphere or its interior contains a high (∼ 40 per cent) water-mass fraction.

AB - We report on the detailed characterisation of K2-370 b, a transiting sub-Neptune on a 2.14-d orbit around the chromospherically active G-type dwarf HD 284521 (𝑇eff = 5662 ± 44 K, < log 𝑅′𝐻𝐾 >= −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 ± 0.05 d and measure the planetary RV signal with semi-amplitude 𝐾𝑏 = 5.6 ± 0.7 m s−1. We find that K2-370 b has a radius of 2.67 ± 0.05 𝑅⊕ and a mass of 11.1 ± 1.4 𝑀⊕. With an estimated equilibrium temperature 𝑇eq ∼ 1480 K, K2-370 b is the second-hottest sub-Neptune with a highly precise mass determination around primaries with 𝑇eff > 5500 K. The resulting density of 3.2±0.4 g cm−3 implies that K2-370 b either retains a significant (∼ 2 per cent by mass) H-rich atmosphere or its interior contains a high (∼ 40 per cent) water-mass fraction.

KW - methods: miscellaneous

KW - planets and satellites: composition

KW - stars: individual: HD 284521 (K2-370)

KW - techniques: radial velocities

KW - techniques: photometric

UR - https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stae2323/7819156

U2 - 10.1093/mnras/stae2323

DO - 10.1093/mnras/stae2323

M3 - Article

SN - 0035-8711

VL - 535

SP - 531

EP - 550

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 1

ER -

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

Abstract

Bibliographical note

Keywords

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