GJ 367b: A dense ultra-short period sub-Earth planet transiting a nearby red dwarf star
Abstract
Ultra-short-period (USP) exoplanets have orbital periods shorter than one day. Precise masses and radii of USPs could provide constraints on their unknown formation and evolution processes. We report the detection and characterization of the USP planet GJ 367b using high precision photometry and radial velocity observations. GJ 367b orbits a bright (V-band magnitude = 10.2), nearby, red (M-type) dwarf star every 7.7 hours. GJ 367b has a radius of 0.718 0.054 Earth-radii, a mass of 0.546 0.078 Earth-masses, making it a sub-Earth. The corresponding bulk density is 8.106 2.165 g cm-3, close to that of iron. An interior structure model predicts the planet has an iron core radius fraction of 86 5\%, similar to Mercury's interior.
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