摘要：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 (Teq= 525 ± 11 K) with a radius ofRb= 1.217 ± 0.084R⊕and an orbital period ofPb= 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 ofMb= 1.84 ± 0.31M⊕. 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 ofMc= 3.40 ± 0.46M⊕in a 9.12 d orbit, and GJ 357 d, with a minimum mass ofMd= 6.1 ± 1.0M⊕in a 55.7 d orbit inside the habitable zone. The host is relatively inactive and exhibits a photometric rotation period ofProt= 78 ± 2 d. GJ 357 b isto 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.
