An ultra-short-period transiting super-Earth orbiting the M3 dwarf TOI-1685
P. Bluhm, E. Pallé, Karan 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, Peyton Brown, Charles Cadieux, Ryan Cloutier, Karen A. Collins, Kevin I. Collins, M. Cortés‐Contreras, René Doyon, S. Dreizler, Néstor Espinoza, Akihiko Fukui, E. González-Álvarez, Th. Henning, K. Horne, S. V. Jeffers, Jon M. Jenkins, Eric L. N. Jensen, A. Kaminski, John F. Kielkopf, Nobuhiko Kusakabe, M. Kürster, David Lafreniére, R. Luque, F. Murgas, D. Montes, J. C. Morales, Norio Narita, V. M. Passegger, A. Quirrenbach, P. Schöfer, S. Reffert, A. Reiners, I. Ribas, G. Ricker, Sara Seager, A. Schweitzer, Richard P. Schwarz, Motohide Tamura, Trifon Trifonov, R. Vanderspek, Joshua N. Winn, M. Zechmeister, M. R. Zapatero Osorio
Abstract
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 P b = 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 M b = 3.78 −0.63 +0.63 M ⊕ , a radius of R b = 1.70 −0.07 +0.07 R ⊕ , which together result in a bulk density of ρ b = 4.21 −0.82 +0.95 g cm −3 , and an equilibrium temperature of T eq = 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 P c = 9.02 −0.12 +0.10 d.