Hidden Transits: TOI-2285 b is a Warmer sub-Neptune Likely with a Super-Earth Companion

TOI-2285 b is a sub-Neptune-sized planet orbiting a nearby M dwarf, discovered through the TESS photometric survey and ground-based follow-up observations.

The planet was initially reported to have an orbital period of 27.27 d, making it one of the lowest temperature sub-Neptunes transiting a bright M dwarf. However, additional TESS data reveal that its true orbital period is 13.64 d, half the original value, resulting in a warmer equilibrium temperature (358 K) than previously estimated (284 K).

The misidentification likely resulted from the low signal-to-noise ratio of individual transit signals and the limited number of transits observed by TESS at that time. This case highlights the importance of carefully considering harmonic solutions for similar cases. The additional TESS data also reveal another planetary candidate with an orbital period of 9.67 d and a radius of 1.5 R_⊕, requiring validation in future studies.

Akihiko Fukui

Comments: 4 pages, 1 figure, published in RNAAS (the initial submission to arXiv was in April 2025)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2505.22009 [astro-ph.EP] (or arXiv:2505.22009v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2505.22009
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Journal reference: Research Notes of the AAS, Volume 9, Issue 4, id.73 (2025)
Related DOI:
https://doi.org/10.3847/2515-5172/adc7fb
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Submission history
From: Akihiko Fukui
[v1] Wed, 28 May 2025 06:17:04 UTC (472 KB)
https://arxiv.org/abs/2505.22009
Astrobiology,