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arXiv · 2601.07374

Possible evidence for a pair-instability supernova nature of ultra-early JWST sources

Andrea Ferrara·Stefano Carniani·Takahiro Morishita·Massimo Stiavelli
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Abstract

Recent JWST observations have revealed a population of unexpectedly bright sources at ultra-high redshift ($z > 15$), challenging current models of early galaxy formation. One extreme example is 'Capotauro', an F356W-dropout identified in the CEERS survey and initially interpreted as a luminous galaxy at $z\sim30$, but subsequently found to be variable over an $\sim 800$ day baseline. Motivated by this variability, we explore the alternative hypothesis that Capotauro is a pair-instability supernova (PISN) originating from a massive ($250-260\,M_\odot$), metal-free star. Using state-of-the-art PISN light curves, spectral energy distributions, and synthetic spectra, we show that a PISN at $z\simeq 15$ can plausibly reproduce the observed brightness, temporal evolution, photometry, and NIRSpec spectrum. We compare this scenario with alternative interpretations, including a local Y0 brown dwarf, and discuss observational tests to discriminate among them. If confirmed, this event would provide a rare window onto Population III stars, and highlights the importance of transient contamination in ultra-high redshift galaxy samples.

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Andrea Ferrara, Stefano Carniani, Takahiro Morishita, Massimo Stiavelli. 2026-01-12. Possible evidence for a pair-instability supernova nature of ultra-early JWST sources. https://doi.org/10.33232/001c.162107

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