TOI-1199 b and TOI-1273 b: Two new transiting hot Saturns detected and characterized with SOPHIE and TESS

J. Serrano Bell, R. F. Díaz, G. Hébrard, E. Martioli, N. Heidari, S. Sousa, I. Boisse, J. M. Almenara, J. Alonso-Santiago, S. C.C. Barros, P. Benni, A. Bieryla, X. Bonfils, D. A. Caldwell, D. R. Ciardi, K. A. Collins, P. Cortés-Zuleta, S. Dalal, J. P. De León, M. DeleuilX. Delfosse, O. D.S. Demangeon, E. Esparza-Borges, T. Forveille, A. Frasca, A. Fukui, J. Gregorio, N. M. Guerrero, S. B. Howell, S. Hoyer, K. Ikuta, J. M. Jenkins, F. Kiefer, D. W. Latham, G. Marino, E. J. Michaels, C. Moutou, F. Murgas, N. Narita, E. Palle, H. Parviainen, N. C. Santos, K. G. Stassun, J. N. Winn

Research output: Contribution to journalArticlepeer-review


We report the characterization of two planet candidates detected by the Transiting Exoplanet Survey Satellite (TESS), TOI-1199 b and TOI-1273 b, with periods of 3.7 and 4.6 days, respectively. Follow-up observations for both targets, which include several ground-based light curves, confirmed the transit events. High-precision radial velocities from the SOPHIE spectrograph revealed signals at the expected frequencies and phases of the transiting candidates and allowed mass determinations with a precision of 8.4% and 6.7% for TOI-1199 b and TOI-1273 b, respectively. The planetary and orbital parameters were derived from a joint analysis of the radial velocities and photometric data. We find that the planets have masses of 0.239 ± 0.020 MJ and 0.222 ± 0.015 MJ and radii of 0.938 ± 0.025 RJ and 0.99 ± 0.22 RJ, respectively. The grazing transit of TOI-1273 b translates to a larger uncertainty in its radius, and hence also in its bulk density, compared to TOI-1199 b. The inferred bulk densities of 0.358 ± 0.041 g cm-3 and 0.28 ± 0.11 g cm-3 are among the lowest known for exoplanets in this mass range, which, considering the brightness of the host stars (V≈11 mag), render them particularly amenable to atmospheric characterization via the transit spectroscopy technique. The better constraints on the parameters of TOI-1199 b provide a transmission spectroscopy metric of 134 ± 17, making it the better suited of the two planets for atmospheric studies.

Original languageEnglish (US)
Article numberA6
JournalAstronomy and Astrophysics
StatePublished - Apr 1 2024

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • planetary systems
  • planets and satellites: detection
  • planets and satellites: gaseous planets
  • techniques: photometric
  • techniques: radial velocities


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