  One of the main goals of the NASA's TESS (Transiting Exoplanet Survey
Satellite) mission is the discovery of Earth-like planets around nearby M-dwarf
stars. Here, we present the discovery and validation of three new short-period
Earth-sized planets orbiting nearby M-dwarfs: TOI- 5720b, TOI-6008b and
TOI-6086b. We combined TESS data, ground-based multi-color light curves,
ground-based optical and near-infrared spectroscopy, and Subaru/IRD RVs data to
validate the planetary candidates and constrain the physical parameters of the
systems. In addition, we used archival images, high-resolution imaging, and
statistical validation techniques to support the planetary validation.
TOI-5720b is a planet with a radius of Rp=1.09 Re orbiting a nearby (23 pc)
M2.5 host, with an orbital period of P=1.43 days. It has an equilibrium
temperature of Teq=708 K and an incident flux of Sp=41.7 Se. TOI-6008b has a
period of P=0.86 day, a radius of Rp=1.03 Re, an equilibrium temperature of
Teq=707 K and an incident flux of Sp=41.5 Se. The host star (TOI-6008) is a
nearby (36 pc) M5 with an effective temperature of Teff=3075 K. Based on the RV
measurements collected with Subaru/IRD, we set a 3-sigma upper limit of Mp<4
M_Earth, thus ruling out a star or brown dwarf as the transiting companion.
TOI-6086b orbits its nearby (31 pc) M3 host star (Teff=3200 K) every 1.39 days,
and has a radius of Rp=1.18 Re, an equilibrium temperature of Teq=634 K and an
incident flux of Sp=26.8 Se. Additional high precision radial velocity
measurements are needed to derive the planetary masses and bulk densities, and
to search for additional planets in the systems. Moreover, short-period
earth-sized planets orbiting around nearby M-dwarfs are suitable targets for
atmospheric characterization with the James Webb Space Telescope (JWST) through
transmission and emission spectroscopy, and phase curve photometry.
