EUROPEAN SPACE AGENCY

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

DOI: 10.3847/1538-3881/ad9266 Bibcode: 2025AJ....169...47K

Butler, R. Paul; Vanderburg, Andrew; Brahm, Rafael; Littlefield, Colin; Stassun, Keivan G.; Wittenmyer, Robert A.; Howell, Steve B.; Horner, Jonathan; Kabáth, Petr; Collins, Karen A.; Ricker, George R.; Seager, Sara; Jenkins, Jon M.; Vanzi, Leonardo; Crane, Jeffrey D.; Shporer, Avi; Collins, Kevin I.; Ciardi, David R.; Guenther, Eike W.; Bailey, Jeremy; Colón, Knicole D.; Twicken, Joseph D.; Daylan, Tansu; Osborn, Hugh P.; Kunimoto, Michelle; Hinkel, Natalie R.; Schwarz, Richard P.; Paegert, Martin; Díaz, Matías R.; Wang, Sharon X.; Kanodia, Shubham; Lin, Zifan; Doty, John P.; Teske, Johanna K.; Burt, Jennifer A.; Srdoc, Gregor; Feng, Fabo; Carter, Brad; Millholland, Sarah; Jones, Hugh R. A.; Winn, Joshua; Shectman, Steve; Venner, Alexander; Pintr, Pavel; Janik, Jan; O'Toole, Simon

United States, Canada, Australia, Chile, China, Germany, Česko, United Kingdom, Czech Republic, Switzerland, Croatia

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 ( , P = 4.47 days) and HD 101581c ( , 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 ( , 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. *This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

2025 • The Astronomical Journal
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