A Second Planet Transiting LTT 1445A and a Determination of the Masses of Both Worlds

Abstract LTT 1445 is a hierarchical triple M-dwarf star system located at distance of 6.86 pc. The primary 1445A (0.257 M ⊙ ) known to host the transiting planet 1445Ab with an orbital period 5.36 days, making it second-closest exoplanet system, and closest one for which dwarf. Using Transiting Exoplanet Survey Satellite data, we present discovery second in 3.12 days. We combine radial-velocity measurements obtained from five spectrographs, Echelle Spectrograph Rocky Exoplanets Stable Spectroscopic Observations, High Accuracy Radial Velocity Planet Searcher, High-Resolution Spectrometer, MAROON-X, Finder establish that new world also orbits 1445A. determine mass radius be 2.87 ± 0.25 ⊕ 1.304 − 0.060 + 0.067 R , consistent Earth-like composition. For newly discovered 1445Ac, measure ${1.54}_{-0.19}^{+0.20}$?> 1.54 0.19 0.20 minimum 1.15 but cannot directly as signal-to-noise ratio our light curve permits both grazing nongrazing configurations. MEarth photometry ground-based spectroscopy, C (0.161 likely source 1.4 day rotation period, B (0.215 has 6.7 estimate probable 85 days Thus, this appears special evolutionary stage where most massive dwarf spun down, intermediate process spinning while least stellar component not yet begun spin down.