Three short-period Earth-sized planets around M dwarfs discovered by TESS: TOI-5720 b, TOI-6008 b, and TOI-6086 b

Abstract

One of the main goals of the NASA Transiting Exoplanet Survey Satellite (TESS) mission is the discovery of Earth-like planets around nearby M-dwarf stars. We present the discovery and validation of three new short-period Earth-sized planets orbiting nearby M dwarfs: TOI-5720\,b, TOI-6008\,b, and TOI-6086\,b. We combined TESS data, ground-based multicolor light curves, ground-based optical and near-infrared spectroscopy, and Subaru/IRD radial velocity 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-5720\,b is an Earth-sized planet with a radius of $R_p = 1.09 0.07 R_ It orbits a nearby (36 pc) M2.5 host with an orbital period of $P = 1.4344555 0.0000036 $ days. It has an equilibrium temperature of eq 19$ K (assuming a null albedo) and an incident flux of $S_p = 41.7 4.5 S_ TOI-6008\,b is a short-period planet of $ P = 0.8574347 0.0000424$ day. It has a radius of $R_p = 1.03 0.05 R_ an equilibrium temperature of eq 19$ K, and an incident flux of $S_p = 41.5 4.5 S_ The host star (TOI-6008) is a nearby (23 pc) M5 with an effective temperature of eff 75 K$. Based on the radial velocity measurements collected with Subaru/IRD, we set a $3 upper limit of $M_p < 4M_ thus ruling out a star or brown dwarf as the transiting companion. TOI-6086\,b orbits its nearby (32 pc) M3 host star eff 75$ K) every $1.3888725 0.0000827$ days and has a radius of $ R_p = 1.18 0.07 R_ an equilibrium temperature of eq 16$ K, and an incident flux of $S_p = 26.8 2.7 S_ 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 an atmospheric characterization with the James Webb Space Telescope through transmission and emission spectroscopy and phase-curve photometry.