Exoplanets & Exomoons

A Hot Mars-sized Exoplanet Transiting An M Dwarf

By Keith Cowing
December 8, 2021
Filed under
A Hot Mars-sized Exoplanet Transiting An M Dwarf
KOI-4777.01 on the mass-radius diagram. Without a mass measurement, we only constrain the most probable location of KOI-4777.01. The shaded regions indicate our 1σ and 3σ radius measurement, and incorporate limits on the mass from density constraints. For comparison, we include the inner Solar System planets and the Moon (red diamonds), well-characterized and small Kepler planets (Almenara et al. 2018; Mills & Fabrycky 2017), the TRAPPIST-1 system (Agol et al. 2021), and known USPs (gray points) from the NASA Exoplanet Archive (queried 3 September 2021). We include several model composition curves from Zeng et al. (2019). KOI-4777.01 is hot (Teq > 1000K), and is incompatible with models that include an atmosphere with temperature effects. It is compatible with models of rocky planets with no significant volatile envelope.

We validate the planetary nature of an ultra-short period planet orbiting the M dwarf KOI-4777. We use a combination of space-based photometry from Kepler, high-precision, near-infrared Doppler spectroscopy from the Habitable-zone Planet Finder, and adaptive optics imaging to characterize this system.

KOI-4777.01 is a Mars-sized exoplanet (Rp=0.51±0.03R⊕) orbiting the host star every 0.412-days (∼9.9-hours). This is the smallest validated ultra-short period planet known and we see no evidence for additional massive companions using our HPF RVs. We constrain the upper 3σ mass to Mp<0.34 M⊕ by assuming the planet is less dense than iron. Obtaining a mass measurement for KOI-4777.01 is beyond current instrumental capabilities. Caleb I. Cañas, Suvrath Mahadevan, William D. Cochran, Chad F. Bender, Eric D. Feigelson, C. E. Harman, Ravi Kumar Kopparapu, Gabriel A. Caceres, Scott A. Diddams, Michael Endl, Eric B. Ford, Samuel Halverson, Fred Hearty, Sinclaire Jones, Shubham Kanodia, Andrea S.J. Lin, Andrew J. Metcalf, Andrew Monson, Joe P. Ninan, Lawrence W. Ramsey, Paul Robertson, Arpita Roy, Christian Schwab, Guðmundur Stefánsson Comments: 25 pages, 8 figures, accepted for publication in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2112.03958 [astro-ph.EP] (or arXiv:2112.03958v1 [astro-ph.EP] for this version)
Submission history
From: Caleb Cañas [view email]
[v1] Tue, 7 Dec 2021 19:30:02 UTC (3,272 KB)

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) 🖖🏻