Two mini-Neptunes transiting the adolescent K-star HIP 113103 confirmed with TESS and CHEOPS

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, C. Hellier, S. Seager, J. N. Winn, J. M. Jenkins, B. Wohler, A. Shporer, R. P. Schwarz, F. MurgasE. 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

Research output: Contribution to journalArticlepeer-review

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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 h 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 3 yr 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+−00067096 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+−000810 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.

Original languageEnglish (US)
Pages (from-to)1146-1162
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Jan 1 2024

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • TIC121490076
  • detection – stars
  • individual
  • photometric – techniques
  • planets
  • satellites
  • spectroscopic
  • techniques


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