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Two mini-Neptunes Transiting the Adolescent K-star HIP 113103 Confirmed with <i>TESS</i> and <i>CHEOPS</i>

Lowson, N; Zhou, G; Huang, C X; Wright, D J; Edwards, B; Nabbie, E; Venner, A; Quinn, S N; Collins, K A; Gillen, E; Battley, M; Triaud, A; Hellier, C; Seager, S; Winn, J N; Jenkins, J M; Wohler, B; Shporer, A; Schwarz, R P; Murgas, F; Pallé, E; Anderson, D R; West, R G; Wittenmyer, R A; Bowler, B P; Horner, J; Kane, S R; Kielkopf, J; Plavchan, P; Zhang, H; Fairnington, T; Okumura, J; Mengel, M W; Addison, B C


N Lowson

G Zhou

C X Huang

D J Wright

B Edwards

E Nabbie

A Venner

S N Quinn

K A Collins

E Gillen

M Battley

A Triaud

S Seager

J N Winn

J M Jenkins

B Wohler

A Shporer

R P Schwarz

F Murgas

E Pallé

D R Anderson

R G West

R A Wittenmyer

B P Bowler

J Horner

S R Kane

J Kielkopf

P Plavchan

H Zhang

T Fairnington

J Okumura

M W Mengel

B C Addison


We report the discovery of two mini-Neptunes in near 2:1 resonance orbits (P = 7.610303 d for HIP 113103 b and P = 14.245651 d for HIP 113103 c ) around the adolescent K-star HIP 113103 (TIC 121490076 ). The planet system was first identified from the TESS mission, and was confirmed via additional photometric and spectroscopic observations, including a ∼17.5 hour observation for the transits of both planets using ESA CHEOPS . We place ≤4.5 min and ≤2.5 min limits on the absence of transit timing variations over the three year photometric baseline, allowing further constraints on the orbital eccentricities of the system beyond that available from the photometric transit duration alone. With a planetary radius of Rp = $1.829_{-0.067}^{+0.096}$R⊕, HIP 113103 b resides within the radius gap, and this might provide invaluable information on the formation disparities between super-Earths and mini-Neptunes. Given the larger radius Rp = $2.40_{-0.08}^{+0.10}$R⊕ for HIP 113103 c , and close proximity of both planets to HIP 113103 , it is likely that HIP 113103 b might have lost (or is still losing) its primordial atmosphere. We therefore present simulated atmospheric transmission spectra of both planets using JWST , HST , and Twinkle . It demonstrates a potential metallicity difference (due to differences in their evolution) would be a challenge to detect if the atmospheres are in chemical equilibrium. As one of the brightest multi sub-Neptune planet systems suitable for atmosphere follow up, HIP 113103 b and HIP 113103 c could provide insight on planetary evolution for the sub-Neptune K-star population.

Journal Article Type Article
Acceptance Date Sep 6, 2023
Online Publication Date Sep 12, 2023
Deposit Date Sep 28, 2023
Publicly Available Date Oct 3, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 527
Issue 1
Article Number stad2756
Pages 1146-1162
Keywords Space and Planetary Science, Astronomy and Astrophysics


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Copyright Statement
© The Author(s) 2023. 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 (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

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