Exoplanetology: Exoplanets & Exomoons

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

By Keith Cowing
Status Report
astro-ph.EP
February 23, 2025
Filed under , , , , , , ,
A Long Spin Period For A Sub-Neptune-mass Exoplanet
Long- and short-cadence transit light curve data for HIP 41378 f, folded with orbital period Porb = 542.08 days. The reduced long-cadence data is shown in the left panels in scattered points; the short-cadence data is shown on the right with small points, then binned to 30 minutes and plotted with large points. The solid purple curve shows a randomly-drawn model from the posterior for comparison. The lower row presents the residual between the maximum likelihood model and the data. If we select the maximum likelihood model with f > 0.1, we obtain the residual shown in the dashed purple curve, which is disfavored with log-likelihood difference ∆ (log L) ≈ −3.4 — astro-ph.EP

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
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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