![The Rapid ASKAP Continuum Survey (RACS) radio images of radio sources associated with candidates A (J1245-2652, top row) and B (J0356-4031, bottom row) are shown at three frequencies: 887.5 MHz (left), 1367.5 MHz (centre), and 1655.5 MHz (right), with each panel covering a field of view of 65" × 65" . White ellipses show the PyBDSF source fits from the RACS catalogues, with thick solid lines indicating the fits at the frequency of the image, while thin dashed lines show fits from the other radio frequencies for comparison. Large blue crosses (×) mark radio source positions for the corresponding frequency, and small blue plus signs (+) indicate positions at other frequencies. The red stars represent the Gaia positions propagated to the corresponding RACS observation epochs using the measured proper motions. -- [astro-ph.SR]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/07/Archival-Diagnostics.png?fit=1200%2C672&ssl=1)
[astro-ph.SR] We report on the diagnostic inspection of nine Project Hephaistos Dyson Sphere candidate M-dwarfs based on archival data. By comparing the Gaia positions, 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 is coincident with a radio counterpart with 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.
Tongtian Ren (1), Michael A. Garrett (1, 2 and 7), Erik Zackrisson (3), Andreas J. Korn (3), Andrew P. V. Siemion (1, 4, 5, 6 and 7), Jason T. Wright (8, 9 and 10), Alexis Brandeker (11) ((1) Jodrell Bank Centre for Astrophysics, University of Manchester, UK, (2) Leiden Observatory, Leiden University, Netherlands, (3) Department of Physics and Astronomy, Uppsala University, Sweden, (4) Breakthrough Listen, University of Oxford, UK, (5) Berkeley SETI Research Center, University of California, Berkeley, USA, (6) SETI Institute, USA, (7) University of Malta, Malta, (8) Department of Astronomy and Astrophysics, The Pennsylvania State University, USA, (9) Penn State Extraterrestrial Intelligence Center, The Pennsylvania State University, USA, (10) Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, USA, (11) Department of Astronomy, Stockholm University, Sweden)
Comments: 16 figures, 13 tables. Presented at IAUS 404: Advancing the Search for Technosignatures (March 2026). Submitted to the MNRAS
Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2607.03619 [astro-ph.SR] (or arXiv:2607.03619v1 [astro-ph.SR] for this version)
https://doi.org/10.48550/arXiv.2607.03619
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Submission history
From: Tongtian Ren
[v1] Fri, 3 Jul 2026 22:31:21 UTC (9,887 KB)
https://arxiv.org/abs/2607.03619
Astrobiology, SETI, Technosignature,
