A Panchromatic Characterization Of The Evening And Morning Atmosphere Of WASP-107 b

Limb-resolved transmission spectroscopy has the potential to transform our understanding of exoplanetary atmospheres. By separately measuring the transmission spectra of the evening and morning limbs, these atmospheric regions can be individually characterized, shedding light into the global distribution and transport of key atmospheric properties from transit observations alone.

In this work, we follow up the recent detection of limb asymmetry on the exoplanet WASP-107 b (Murphy et al. 2024) by reanalyzing literature observations of WASP-107 b using all of JWST’s science instruments (NIRISS, NIRCam, NIRSpec, and MIRI) to measure its limb transmission spectra from ∼1-12 μm.

We confirm the evening–morning temperature difference inferred previously and find that it is qualitatively consistent with predictions from global circulation models. We find evidence for evening–morning variation in SO₂ and CO₂ abundance, and significant cloud coverage only on WASP-107 b’s morning limb.

We find that the NIRISS and NIRSpec observations are potentially contaminated by occulted starspots, which we leverage to investigate stellar contamination’s impact on limb asymmetry measurements.

We find that starspot crossings can significantly bias the inferred evening and morning transmission spectra depending on when they occur during the transit, and develop a simple correction model which successfully brings these instruments’ spectra into agreement with the uncontaminated observations.

A Panchromatic Characterization Of The Evening And Morning Atmosphere Of WASP-107 b: Composition and Cloud Variations, and Insight into the Effect of Stellar Contamination

Matthew M. Murphy, Thomas G. Beatty, Everett Schlawin, Taylor J. Bell, Michael Radica, Thomas D. Kennedy, Nishil Mehta, Luis Welbanks, Michael R. Line, Vivien Parmentier, Thomas P. Greene, Sagnick Mukherjee, Jonathan J. Fortney, Kazumasa Ohno, Lindsey Wiser, Kenneth Arnold, Emily Rauscher, Isaac R. Edelman, Marcia J. Rieke

Comments: Currently under review with the Astronomical Journal. Comments welcome
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2505.13602 [astro-ph.EP] (or arXiv:2505.13602v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2505.13602
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Journal reference: AJ 170 61 (2025)
Related DOI:
https://doi.org/10.3847/1538-3881/addf38
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Submission history
From: Matthew Murphy
[v1] Mon, 19 May 2025 18:00:03 UTC (6,001 KB)
https://arxiv.org/abs/2505.13602
Astrobiology,