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Arxiv: Two-Dimensional Eclipse Mapping of the Hot Jupiter WASP-43b with JWST MIRI/LRS Published: 4/25/2024 1:21:35 PM Updated: 4/25/2024 1:21:35 PM

Paper abstract: We present eclipse maps of the two-dimensional thermal emission from thedayside of the hot Jupiter WASP-43b, derived from an observation of a phasecurve with the JWST MIRI/LRS instrument. The observed eclipse shapes deviatesignificantly from those expected for a planet emitting uniformly over itssurface. We fit a map to this deviation, constructed from spherical harmonicsup to order \ell_{\rm max}=2, alongside the planetary, orbital, stellar, andsystematic parameters. This yields a map with a meridionally-averaged eastwardhot-spot shift of (7.75 \pm 0.36)^{\circ}, with no significant degeneracybetween the map and the additional parameters. We show the latitudinal andlongitudinal contributions of the day-side emission structure to the eclipseshape, finding a latitudinal signal of ~200 ppm and a longitudinal signalof ~250 ppm. To investigate the sensitivity of the map to the method, wefix the non-mapping parameters and derive an "eigenmap" fitted with anoptimised number of orthogonal phase curves, which yields a similar map to the\ell_{\rm max}=2 map. We also fit a map up to \ell_{\rm max}=3, which showsa smaller hot-spot shift, with a larger uncertainty. These maps are similar tothose produced by atmospheric simulations. We conclude that there is asignificant mapping signal which constrains the spherical harmonic componentsof our model up to \ell_{\rm max}=2. Alternative mapping models may derivedifferent structures with smaller-scale features; we suggest that furtherobservations of WASP-43b and other planets will drive the development of morerobust methods and more accurate maps.