An ultra-short-period transiting super-Earth orbiting the M3 dwarf TOI-1685

P. Bluhm, E. Pallé, K. Molaverdikhani, J. Kemmer, A. P. Hatzes, D. Kossakowski, S. Stock, J. A. Caballero, J. Lillo-Box, V. J.S. Béjar, M. G. Soto, P. J. Amado, P. Brown, C. Cadieux, R. Cloutier, K. A. Collins, K. I. Collins, M. Cortés-Contreras, R. Doyon, S. DreizlerN. Espinoza, A. Fukui, E. González-Álvarez, Th Henning, K. Horne, S. V. Jeffers, J. M. Jenkins, E. L.N. Jensen, A. Kaminski, J. F. Kielkopf, N. Kusakabe, M. Kürster, D. Lafrenière, R. Luque, F. Murgas, D. Montes, J. C. Morales, N. Narita, V. M. Passegger, A. Quirrenbach, P. Schöfer, S. Reffert, A. Reiners, I. Ribas, G. R. Ricker, S. Seager, A. Schweitzer, R. P. Schwarz, M. Tamura, T. Trifonov, R. Vanderspek, J. Winn, M. Zechmeister, M. R. Zapatero Osorio

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24 Scopus citations


Dynamical histories of planetary systems, as well as the atmospheric evolution of highly irradiated planets, can be studied by characterizing the ultra-short-period planet population, which the TESS mission is particularly well suited to discover. Here, we report on the follow-up of a transit signal detected in the TESS sector 19 photometric time series of the M3.0 V star TOI-1685 (2MASS J04342248+4302148). We confirm the planetary nature of the transit signal, which has a period of Pb = 0.6691403-0.0000021+0.0000023 d, using precise radial velocity measurements taken with the CARMENES spectrograph. From the joint photometry and radial velocity analysis, we estimate the following parameters for TOI-1685 b: a mass of Mb = 3.78-0.63+0.63 M? , a radius of Rb = 1.70-0.07+0.07 R? , which together result in a bulk density of ρb = 4.21-0.82+0.95 g cm-3, and an equilibrium temperature of Teq = 1069-16+16 K. TOI-1685 b is the least dense ultra-short-period planet around an M dwarf known to date. TOI-1685 b is also one of the hottest transiting super-Earth planets with accurate dynamical mass measurements, which makes it a particularly attractive target for thermal emission spectroscopy. Additionally, we report with moderate evidence an additional non-transiting planet candidate in the system, TOI-1685 [c], which has an orbital period of Pc = 9.02-0.12+0.10 d.

Original languageEnglish (US)
Article numberA78
JournalAstronomy and Astrophysics
StatePublished - Jun 1 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Stars: individual: TOI-1685
  • Stars: late-type
  • Techniques: photometric
  • Techniques: radial velocities


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