The Neptunian ridge through the lens of TESS
Abstract
The Neptunian desert and savanna are separated by a ridge, an overdensity at orbital periods of approximately 3-6 d identified with Kepler. Like the hot Jupiter pileup at larger radii, this feature has been linked to the accumulation of successful outcomes of high-eccentricity migration (HEM). We revisit the ridge independently using TESS occurrence posteriors for FGK main-sequence stars. We quantify its excess over adjacent regions and compare six occurrence profiles using leave-one-out cross-validation and Bayesian evidence. For planets with radii of approximately 5-8 R⊕, the ridge has twice the occurrence density of the denser neighbouring region (J=2.05+0.52−0.44), with 99.9% posterior support (one-sided Gaussian equivalent of 3.1σ). This contrast agrees with the discovery study and earlier Kepler occurrence measurements. Both predictive performance and Bayesian evidence strongly favour profiles peaking within the ridge over a single power law. The lognormal is preferred, suggesting a narrower inner wing and a more extended outer wing, although evidence for asymmetry remains weak. In the same period window, the analysis recovers the hot Jupiter pileup (approximately 10-16 R⊕) with a contrast consistent with that of the ridge and excludes an analogous excess among sub-Neptunes (approximately 2-4 R⊕) with 3.4σ posterior support. TESS thus provides an independent detection of the Neptunian ridge. Its possible asymmetry would be compatible with HEM, in which tidal disruption could produce a sharper inner edge and variations in circularisation efficiency a more gradual outer decline. Establishing whether the ridge has this shape requires more precise occurrence measurements, with PLATO's expected planet yield offering a promising opportunity to help unveil its morphology.
Related
- Demographics of Close-In TESS Exoplanets Orbiting FGK Main-sequence Stars II. Spectral-Type Dependence and the Neptunian Landscape
- Demographics of Close-In TESS Exoplanets Orbiting FGK Main-sequence Stars – II. Spectral-Type Dependence and the Neptunian Landscape
- ATREIDES II. Detection of a polar orbit for HAT-P-26 b, a fluffy planet in the Neptunian ridge
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- Testing Charged Black Holes Embedded in Anisotropic Matter and Surrounded by Plasma through Gravitational Lensing: Bounds from the Sloan Lens ACS Survey
BibTeX
@misc{castrogonzalez2026neptunian,
title = {{The Neptunian ridge through the lens of TESS}},
author = {Amadeo Castro-González},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.03643},
eprint = {2611.03643},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.03643},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Neptunian ridge through the lens of TESS
AU - Amadeo Castro-González
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.03643
UR - https://arxiv.org/abs/2611.03643
AB - The Neptunian desert and savanna are separated by a ridge, an overdensity at orbital periods of approximately 3-6 d identified with Kepler. Like the hot Jupiter pileup at larger radii, this feature has been linked to the accumulation of successful outcomes of high-eccentricity migration (HEM). We revisit the ridge independently using TESS occurrence posteriors for FGK main-sequence stars. We quantify its excess over adjacent regions and compare six occurrence profiles using leave-one-out cross-validation and Bayesian evidence. For planets with radii of approximately 5-8 R_⊕, the ridge has twice the occurrence density of the denser neighbouring region (J=2.05^+0.52_−0.44), with 99.9% posterior support (one-sided Gaussian equivalent of 3.1σ). This contrast agrees with the discovery study and earlier Kepler occurrence measurements. Both predictive performance and Bayesian evidence strongly favour profiles peaking within the ridge over a single power law. The lognormal is preferred, suggesting a narrower inner wing and a more extended outer wing, although evidence for asymmetry remains weak. In the same period window, the analysis recovers the hot Jupiter pileup (approximately 10-16 R_⊕) with a contrast consistent with that of the ridge and excludes an analogous excess among sub-Neptunes (approximately 2-4 R_⊕) with 3.4σ posterior support. TESS thus provides an independent detection of the Neptunian ridge. Its possible asymmetry would be compatible with HEM, in which tidal disruption could produce a sharper inner edge and variations in circularisation efficiency a more gradual outer decline. Establishing whether the ridge has this shape requires more precise occurrence measurements, with PLATO's expected planet yield offering a promising opportunity to help unveil its morphology.
ER -