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 ⊕ , P = 4.47 days) and HD 101581c ( R p = 0.990 − 0.070 + 0.070 R ⊕ , 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 ⊕ , 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 ⊕ . HD 101581 is a promising system for atmospheric characterization and comparative planetology of small planets.