TESS spots a mini- interior to a hot saturn in the TOI-2000 system

Lizhou Sha, Andrew M. Vanderburg, Chelsea X. Huang, David J. Armstrong, Rafael Brahm, Steven Giacalone, Mackenna L. Wood, Karen A. Collins, Louise D. Nielsen, Melissa J. Hobson, Carl Ziegler, Steve B. Howell, Pascal Torres-Miranda, Andrew W. Mann, George Zhou, Elisa Delgado-Mena, Felipe I. Rojas, Lyu Abe, Trifon Trifonov, Vardan AdibekyanSrgio G. Sousa, Sergio B. Fajardo-Acosta, Tristan Guillot, Saburo Howard, Colin Littlefield, Faith Hawthorn, François Xavier Schmider, Jan Eberhardt, Thiam Guan Tan, Ares Osborn, Richard P. Schwarz, Paul Strøm, Andrs Jordán, Gavin Wang, Thomas Henning, Bob Massey, Nicholas Law, Chris Stockdale, Elise Furlan, Gregor Srdoc, Peter J. Wheatley, David Barrado Navascus, Jack J. Lissauer, Keivan G. Stassun, George R. Ricker, Roland K. Vanderspek, David W. Latham, Joshua N. Winn, Sara Seager, Jon M. Jenkins, Thomas Barclay, Luke G. Bouma, Jessie L. Christiansen, Natalia Guerrero, Mark E. Rose

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Hot jupiters (P < 10 d, M > 60 M?) are almost always found alone around their stars, but four out of hundreds known have inner companion planets. These rare companions allow us to constrain the hot jupiter's formation history by ruling out high-eccentricity tidal migration. Less is known about inner companions to hot Saturn-mass planets. We report here the discovery of the TOI-2000 system, which features a hot Saturn-mass planet with a smaller inner companion. The mini-neptune TOI-2000 b (2.70 ± 0.15 R?, 11.0 ± 2.4 M?) is in a 3.10-d orbit, and the hot saturn TOI-2000 c (R?, M?) is in a 9.13-d orbit. Both planets transit their host star TOI-2000 (TIC 371188886, V = 10.98, TESS magnitude = 10.36), a metal-rich ([Fe/H] = 0.439) G dwarf 173 pc away. TESS observed the two planets in sectors 9-11 and 36-38, and we followed up with ground-based photometry, spectroscopy, and speckle imaging. Radial velocities from CHIRON, FEROS, and HARPS allowed us to confirm both planets by direct mass measurement. In addition, we demonstrate constraining planetary and stellar parameters with MIST stellar evolutionary tracks through Hamiltonian Monte Carlo under the PyMC framework, achieving higher sampling efficiency and shorter run time compared to traditional Markov chain Monte Carlo. Having the brightest host star in the V band among similar systems, TOI-2000 b and c are superb candidates for atmospheric characterization by the JWST, which can potentially distinguish whether they formed together or TOI-2000 c swept along material during migration to form TOI-2000 b.

Original languageEnglish (US)
Pages (from-to)1113-1138
Number of pages26
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Sep 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planets and satellites: detection
  • planets and satellites: formation
  • planets and satellites: gaseous planets
  • stars: individual: TOI-2000 (TIC 371188886)
  • techniques: photometric
  • techniques: radial velocities


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