A sub-Neptune transiting the young field star HD 18599 at 40 pc

J. P. de Leon, J. H. Livingston, J. S. Jenkins, J. I. Vines, R. A. Wittenmyer, J. T. Clark, J. I.M. Winn, B. Addison, S. Ballard, D. Bayliss, C. Beichman, B. Benneke, D. A. Berardo, B. P. Bowler, T. Brown, E. M. Bryant, J. Christiansen, D. Ciardi, K. A. Collins, K. I. CollinsI. Crossfield, D. Deming, D. Dragomir, C. D. Dressing, A. Fukui, T. Gan, S. Giacalone, S. Gill, V. Gorjian, E. González Alvarez, K. Hesse, J. Horner, S. B. Howell, J. M. Jenkins, S. R. Kane, A. Kendall, J. F. Kielkopf, L. Kreidberg, D. W. Latham, H. Liu, M. B. Lund, R. Matson, E. Matthews, M. W. Mengel, F. Morales, M. Mori, N. Narita, T. Nishiumi, J. Okumura, P. Plavchan, S. Quinn, M. Rabus, G. Ricker, A. Rudat, J. Schlieder, R. P. Schwarz, S. Seager, A. Shporer, A. M.S. Smith, K. Stassun, M. Tamura, T. G. Tan, C. Tinney, R. Vanderspek, M. W. Werner, R. G. West, D. Wright, H. Zhang, G. Zhou

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Transiting exoplanets orbiting young nearby stars are ideal laboratories for testing theories of planet formation and evolution. However, to date only a handful of stars with age <1 Gyr have been found to host transiting exoplanets. Here we present the discovery and validation of a sub-Neptune around HD 18599, a young (300 Myr), nearby (d = 40 pc) K star. We validate the transiting planet candidate as a bona fide planet using data from the TESS , Spitzer , and Gaia missions, ground-based photometry from IRSF , LCO , PEST , and NGTS , speckle imaging from Gemini, and spectroscopy from CHIRON , NRES , FEROS , and MINERVA-Australis . The planet has an orbital period of 4.13 d, and a radius of 2.7 R. The RV data yields a 3-σ mass upper limit of 30.5 M which is explained by either a massive companion or the large observed jitter typical for a young star. The brightness of the host star (V∼9 mag) makes it conducive to detailed characterization via Doppler mass measurement which will provide a rare view into the interior structure of young planets.

Original languageEnglish (US)
Pages (from-to)750-766
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Jun 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planets and satellites: detection
  • stars: individual: TOI-179
  • techniques: radial velocities
  • techniques: spectroscopic


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