%0 Journal Article
%A Caballero, J. A.
%A Cortés Contreras, Miriam
%A Montes Gutiérrez, David
%T An ultra-short-period transiting super-Earth orbiting the M3 dwarf TOI-1685
%D 2021
%@ 0004-6361
%U https://hdl.handle.net/20.500.14352/8453
%X 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^(+0.0000023)_(−0.0000021) 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) Mꙩ, a radius of R_(b) = 1.70^(+0.07)_(−0.07) Rꙩ, which together result in a bulk density of ρ_(b) = 4.21^(+0.95)_(−0.82) 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^(+0.10)_(−0.12) d.
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