WASP-43b TESS Phase Curve Mapping: Evidence for a Hot Interior
Abstract
Phase-curve mapping probes various atmospheric properties depending on wavelength: thermal phase curves are dominated by atmospheric emission, while visible and near-infrared phase curves include reflected light. The measured planetary phase curve offset--the longitudinal offset of the hemisphere of peak brightness from the substellar point--is therefore sensitive to differing atmospheric processes in emission-dominated vs. reflection-dominated bands. In particular, planets with partial western-dayside reflective cloud coverage show a westward reflected-light phase-curve offset relative to the thermal wavelengths. In this work, we analyze five sectors of TESS phase curve observations of the hot Jupiter WASP-43b and compare to previous published multi-band analyses to investigate dayside cloud coverage. We measure a mid-eclipse depth of 130 ± 34 ppm, indicating excess TESS planetary brightness above expectations based on observed and modeled thermal emission. Attributing this excess flux to reflection, we estimate a low geometric albedo of Ag ≈ 0.05 - 0.10. These findings support previous conclusions that WASP-43b lacks any significant cloud coverage on its dayside. Phase-curve mapping reveals a large eastward phase curve offset of 44 ± 18 degrees, significantly eastward of offsets measured at longer wavelengths with JWST, providing evidence for a cloud-free dayside. Both the detection of excess emission in the TESS band and the large measured eastward phase-curve offset support the conclusion that WASP-43b has a hot deep atmosphere that is probed at short wavelengths.
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BibTeX
@misc{lally2026wasp43b,
title = {{WASP-43b TESS Phase Curve Mapping: Evidence for a Hot Interior}},
author = {Maura Lally and Ryan C. Challener and Elspeth Lee and Nikole Lewis},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10719},
eprint = {2609.10719},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10719},
}
RIS
TY - UNPB
TI - WASP-43b TESS Phase Curve Mapping: Evidence for a Hot Interior
AU - Maura Lally
AU - Ryan C. Challener
AU - Elspeth Lee
AU - Nikole Lewis
PY - 2026
DA - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2609.10719
UR - https://arxiv.org/abs/2609.10719
AB - Phase-curve mapping probes various atmospheric properties depending on wavelength: thermal phase curves are dominated by atmospheric emission, while visible and near-infrared phase curves include reflected light. The measured planetary phase curve offset--the longitudinal offset of the hemisphere of peak brightness from the substellar point--is therefore sensitive to differing atmospheric processes in emission-dominated vs. reflection-dominated bands. In particular, planets with partial western-dayside reflective cloud coverage show a westward reflected-light phase-curve offset relative to the thermal wavelengths. In this work, we analyze five sectors of TESS phase curve observations of the hot Jupiter WASP-43b and compare to previous published multi-band analyses to investigate dayside cloud coverage. We measure a mid-eclipse depth of 130 ± 34 ppm, indicating excess TESS planetary brightness above expectations based on observed and modeled thermal emission. Attributing this excess flux to reflection, we estimate a low geometric albedo of A_g ≈ 0.05 - 0.10. These findings support previous conclusions that WASP-43b lacks any significant cloud coverage on its dayside. Phase-curve mapping reveals a large eastward phase curve offset of 44 ± 18 degrees, significantly eastward of offsets measured at longer wavelengths with JWST, providing evidence for a cloud-free dayside. Both the detection of excess emission in the TESS band and the large measured eastward phase-curve offset support the conclusion that WASP-43b has a hot deep atmosphere that is probed at short wavelengths.
ER -