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

Research output: Contribution to journal › Article › peer-review

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
Article number	stae2323
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	30 Oct 2024
DOIs	https://doi.org/10.1093/mnras/stae2323
Publication status	Published - 1 Nov 2024

Keywords

Planetary systems
Planets and satellites: composition
Stars: individual: HD 284521 (K2-370)
Techniques: radial velocities
Techniques: photometric
Methods: miscellaneous

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10.1093/mnras/stae2323Licence: CC BY

Sozzetti_2024_MNRAS_K2-370b-strongly-indicative-sub-Neptune_CC
Copyright © 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Final published version, 3.24 MBLicence: CC BY

1 Finished
2 Active

REVEAL: REVEALing Signatures of Habitable Worlds Hidden by Stellar Activity
Cameron, A. C. (PI)
UKRI (EU)
1/08/24 → 31/07/30
Project: Standard
PLATO 22-25: Support for the PLATO Development Phase 2022-2025: Planet candidate ranking and validation
Cameron, A. C. (PI)
Science & Technology Facilities Council
1/04/22 → 31/03/25
Project: Standard
AO2 - Professor Andrew Cameron: Project AO2 - Andrew Cameron
Cameron, A. C. (PI)
Science & Technology Facilities Council
1/04/21 → 31/03/24
Project: Standard

Cite this

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. Article stae2323. https://doi.org/10.1093/mnras/stae2323

@article{42126d02f2d34459893931fdcd6b38e5,

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 = "Planetary systems, Planets and satellites: composition, Stars: individual: HD 284521 (K2-370), Techniques: radial velocities, Techniques: photometric, Methods: miscellaneous",

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 = "Funding: The authors acknowledge financial contribution from the agreement ASIINAF n.2018-16-HH.0. They gratefully acknowledge support from the Italian Space Agency (ASI) under contract 2018-24-HH.0 {"}The Italian participation to the Gaia Data Processing and Analysis Consortium (DPAC){"} in collaboration with the Italian National Institute of Astrophysics. AVF acknowledges the support of the IOP through the Bell Burnell Graduate Scholarship Fund. ACC acknowledges support from STFC consolidated grant number ST/V000861/1, and UKSA grant number ST/X002217/1. XD acknowledges the support from the European Research Council (ERC) under the European Union{\textquoteright}s Horizon 2020 research and innovation programme (grant agreement SCORE No 851555) and from the Swiss National Science Foundation under the grant SPECTRE (No 200021_215200). FPE would like to acknowledge the Swiss National Science Foundation (SNSF) for supporting research with HARPS-N through the SNSF grants nr. 140649, 152721, 166227, 184618 and 215190. This research was funded in part by the UKRI, (Grants ST/X001121/1, EP/X027562/1).",

year = "2024",

month = nov,

day = "1",

doi = "10.1093/mnras/stae2323",

language = "English",

volume = "535",

pages = "531--550",

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

issn = "0035-8711",

publisher = "Oxford University Press",

number = "1",

}

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, stae2323, pp. 531-550. https://doi.org/10.1093/mnras/stae2323

TY - JOUR

T1 - K2-370 b: 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 - Funding: The authors acknowledge financial contribution from the agreement ASIINAF n.2018-16-HH.0. They gratefully acknowledge support from the Italian Space Agency (ASI) under contract 2018-24-HH.0 "The Italian participation to the Gaia Data Processing and Analysis Consortium (DPAC)" in collaboration with the Italian National Institute of Astrophysics. AVF acknowledges the support of the IOP through the Bell Burnell Graduate Scholarship Fund. ACC acknowledges support from STFC consolidated grant number ST/V000861/1, and UKSA grant number ST/X002217/1. XD acknowledges the support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement SCORE No 851555) and from the Swiss National Science Foundation under the grant SPECTRE (No 200021_215200). FPE would like to acknowledge the Swiss National Science Foundation (SNSF) for supporting research with HARPS-N through the SNSF grants nr. 140649, 152721, 166227, 184618 and 215190. This research was funded in part by the UKRI, (Grants ST/X001121/1, EP/X027562/1).

PY - 2024/11/1

Y1 - 2024/11/1

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 - Planetary systems

KW - Planets and satellites: composition

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

KW - Techniques: radial velocities

KW - Techniques: photometric

KW - Methods: miscellaneous

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

M1 - stae2323

ER -

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

Abstract

Keywords

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Projects

REVEAL: REVEALing Signatures of Habitable Worlds Hidden by Stellar Activity

PLATO 22-25: Support for the PLATO Development Phase 2022-2025: Planet candidate ranking and validation

AO2 - Professor Andrew Cameron: Project AO2 - Andrew Cameron

Cite this