Two Earth-size Planets and an Earth-size Candidate Transiting the nearby Star HD 101581

Abstract

We report the validation of multiple planets transiting the nearby (d = 12.8 pc) K5V dwarf HD 101581 (GJ 435, TOI-6276, TIC 397362481). This system consists of at least two Earth-size planets whose orbits are near a mutual 4:3 mean-motion resonance, HD 101581 b ( R-p=0.956(-0.061)(+0.063 )R(circle plus) , P = 4.47 days) and HD 101581c ( R-p=0.990(-0.070)(+0.070 )R(circle plus) , P = 6.21 days). Both planets were discovered in Sectors 63 and 64 TESS observations and statistically validated with supporting ground-based follow-up. We also identify a signal that probably originates from a third transiting planet, TOI-6276.03 ( R-p=0.982(-0.098)(+0.114 )R(circle plus), P = 7.87 days). These planets are remarkably uniform in size and their orbits are evenly spaced, representing a prime example of the «peas-in-a-pod» architecture seen in other compact multiplanet systems. At V = 7.77, HD 101581 is the brightest star known to host multiple transiting planets smaller than 1.5 R (circle plus). HD 101581 is a promising system for atmospheric characterization and comparative planetology of small planets.