%0 Journal Article
%A Caballero, J. A.
%A Cortés Contreras, Miriam
%A Montes Gutiérrez, David
%T Planetary system around the nearby M dwarf GJ 357 including a transiting, hot, Earth-sized planet optimal for atmospheric characterization
%D 2019
%@ 1432-0746
%U https://hdl.handle.net/20.500.14352/13693
%X We report the detection of a transiting Earth-size planet around GJ 357, a nearby M2.5 V star, using data from the Transiting Exoplanet Survey Satellite (TESS). GJ 357 b (TOI-562.01) is a transiting, hot, Earth-sized planet (T_(eq) = 525 ± 11 K) with a radius of R_(b) = 1.217 ± 0.084 Rꚛ and an orbital period of P_(b) = 3.93 d. Precise stellar radial velocities from CARMENES and PFS, as well as archival data from HIRES, UVES, and HARPS also display a 3.93-day periodicity, confirming the planetary nature and leading to a planetary mass of M_(b) = 1.84 ± 0.31 Mꚛ. In addition to the radial velocity signal for GJ 357 b, more periodicities are present in the data indicating the presence of two further planets in the system: GJ 357 c, with a minimum mass of M_(c) = 3.40 ± 0.46 Mꚛ in a 9.12 d orbit, and GJ 357 d, with a minimum mass of M_(d) = 6.1 ± 1.0 Mꚛ in a 55.7 d orbit inside the habitable zone. The host is relatively inactive and exhibits a photometric rotation period of P_(rot) = 78 ± 2 d. GJ 357 b is to date the second closest transiting planet to the Sun, making it a prime target for further investigations such as transmission spectroscopy. Therefore, GJ 357 b represents one of the best terrestrial planets suitable for atmospheric characterization with the upcoming JWST and ground-based ELTs.
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