A Long Spin Period For A Sub-Neptune-mass Exoplanet

HIP 41378 f is a sub-Neptune exoplanet with an anomalously low density. Its long orbital period and deep transit make it an ideal candidate for detecting oblateness photometrically.
We present a new cross-platform, GPU-enabled code greenlantern, suitable for computing transit light curves of oblate planets at arbitrary orientations. We then use Markov Chain Monte Carlo to fit K2 data of HIP 41378 f, specifically examining its transit for possible oblateness and obliquity.
We find that the flattening of HIP 41378 f is f≤0.889 at the 95% confidence level, consistent with a rotation period of Prot≥15.3 hr. In the future, high-precision data from JWST has the potential to tighten such a constraint and can differentiate between spherical and flattened planets.
Ellen M. Price, Juliette Becker, Zoë L. de Beurs, Leslie A. Rogers, Andrew Vanderburg
Comments: 18 pages, 13 figures, 3 tables. Accepted to ApJL. Code available at this https URL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2410.05408 [astro-ph.EP] (or arXiv:2410.05408v2 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2410.05408
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Submission history
From: Ellen Price
[v1] Mon, 7 Oct 2024 18:17:51 UTC (2,121 KB)
[v2] Mon, 17 Feb 2025 19:00:01 UTC (2,609 KB)
https://arxiv.org/abs/2410.05408
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