Exoplanetology: Exoplanets & Exomoons

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

By Keith Cowing
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astro-ph.EP
December 13, 2024
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Two Earth-size Planets and an Earth-size Candidate Transiting the Nearby Star HD 101581
Instellation flux as a function of planet escape velocity, in log-log scale. Based on data from the NASA Exoplanet Archive (2024) downloaded on June 30, 2024. The empirical “cosmic shoreline” and the water vapor greenhouse runaway threshold (Zahnle & Catling 2017) are shown as cyan and yellow shaded regions, respectively. Planets are categorized into terrestrial planets (magenta), sub-Neptunes (blue), Neptune-like planets (green), and gas giants (yellow) based on radius, see legend. The red rectangles represent escape velocities calculated based on HD 101581 planets’ mean estimated masses assuming Hypatia Catalog metallicity. Because only radius, but not mass, is known, we further plot light red regions covering all possible interior compositions, ranging from pure iron to pure silicates. Height of the rectangles represent uncertainties in insolation. — astro-ph.EP

We report the validation of multiple planets transiting the nearby (d=12.8 pc) K5V dwarf HD 101581 (GJ 435, TOI-6276, TIC 397362481).

The system consists of at least two Earth-size planets whose orbits are near a mutual 4:3 mean-motion resonance, HD 101581 b (Rp=0.956+0.063−0.061 R⊕, P=4.47 days) and HD 101581 c (Rp=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 (Rp=0.982+0.114−0.098 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 multi-planet 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.

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

Comments: 25 pages, 13 figures. Accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2412.08863 [astro-ph.EP] (or arXiv:2412.08863v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2412.08863
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Submission history
From: Michelle Kunimoto
[v1] Thu, 12 Dec 2024 01:52:12 UTC (7,009 KB)
https://arxiv.org/abs/2412.08863
Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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