Super-Earth LHS3844b is tidally locked
Xintong Lyu, Daniel D.B. Koll, Nicolas B. Cowan, Renyu Hu, Laura, Kreidberg, Brain E.J. Rose

TL;DR
This study analyzes the tidally locked state of super-Earth LHS 3844b using thermal modeling and phase curve data, providing empirical evidence supporting tidal locking and highlighting the role of space weathering in surface darkening.
Contribution
It offers the first empirical constraints on the rotation state of LHS 3844b, ruling out non-synchronous rotation and suggesting space weathering influences its surface.
Findings
LHS 3844b is likely tidally locked with very low eccentricity.
Rapid non-synchronous rotation is ruled out by lack of tidal heating evidence.
Surface darkening by space weathering is a plausible explanation for phase curve observations.
Abstract
Short period exoplanets on circular orbits are thought to be tidally locked into synchronous rotation. If tidally locked, these planets must possess permanent day- and nightsides, with extreme irradiation on the dayside and none on the nightside. However, so far the tidal locking hypothesis for exoplanets is supported by little to no empirical evidence. Previous work showed that the super-Earth LHS 3844b likely has no atmosphere, which makes it ideal for constraining the planet's rotation. Here we revisit the Spitzer phase curve of LHS 3844b with a thermal model of an atmosphere-less planet and analyze the impact of non-synchronous rotation, eccentricity, tidal dissipation, and surface composition. Based on the lack of observed strong tidal heating we rule out rapid non-synchronous rotation (including a Mercury-like 3:2 spin-orbit resonance) and constrain the planet's eccentricity to…
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Taxonomy
TopicsStellar, planetary, and galactic studies · Astro and Planetary Science · Astronomy and Astrophysical Research
