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arXiv · 2607.03619

Archival Diagnostics for Potential Background Contaminantsof Project Hephaistos Dyson Sphere Candidates

Tongtian Ren·Michael A. Garrett·Erik Zackrisson·Andreas J. Korn·Andrew P. V. Siemion·Jason T. Wright·Alexis Brandeker
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Abstract

We report on the diagnostic investigation of nine Project Hephaistos Dyson Sphere candidate M-dwarfs based on archival data. By comparing the Gaia DR3 positions with epoch 2016.0, propagated to the AllWISE epoch, with the mid-infrared centroids measured from the AllWISE images, together with deep archival optical/near-infrared imaging, we identified significant background contamination in candidates B and C--candidate B coincident with a radio counterpart showing a power-law-like spectrum with a radio spectral index alpha = 0.63 +/- 0.11, while candidate C has a near-infrared companion at an offset of 3.75 arcsec. Candidate A provides suggestive evidence through a radio counterpart with spectral index alpha = 0.40 +/- 0.35, while candidates E, F, H and J show marginal evidence. These systems exhibit either significant astrometric offsets or visible interlopers, indicating that the mid-infrared excess likely arises from line-of-sight contamination by hot, dust-obscured galaxies. However, candidates D and I still lack obvious signs of contamination. Dedicated observations are therefore essential to characterise these potential interlopers, eliminate false positives, and ensure that technosignature searches focus on the most robust Dyson Sphere candidates.

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Tongtian Ren, Michael A. Garrett, Erik Zackrisson, Andreas J. Korn, Andrew P. V. Siemion, Jason T. Wright, Alexis Brandeker. 2026-09-12. Archival Diagnostics for Potential Background Contaminantsof Project Hephaistos Dyson Sphere Candidates. https://doi.org/10.1093/mnras%2Fstag1558

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