The emergence of Little Red Dots from binary massive black holes

article The emergence of Little Red Dots from binary massive black holes published yes Kohei Inayoshi author Jinyi Shangguan author Xian Chen author Luis C. Ho author Zoltán Haiman author 7c006e8c-cc0d-11ee-8322-cb904ef76f360000-0003-3633-5403 ZoHa department Little red dots (LRDs) are a newly identified class of broad-line active galactic nuclei (AGNs) with a distinctive V-shaped spectrum characterized by red optical and blue UV continuum emission. Their high abundance at redshifts of z ∼ 6–8 and decline at lower redshifts suggest a transient origin. We propose that the spectral shape of LRDs originates from compact binary black hole systems, in which each black hole is surrounded by a mini-disk and embedded within a larger circumbinary disk. With a binary separation of ≲103 Schwarzschild radii, the Wien tail of a T ≃ 5000 K blackbody spectrum at the inner edge of the circumbinary disk produces the red optical emission, while the mini-disks power the UV continuum. Binary torques carve out a gap between the circumbinary disk and the mini-disks, setting the turnover wavelength of the V-shaped spectrum around the Balmer limit. This scenario naturally reproduces LRD spectra requiring only modest dust attenuation (AV ≲ 1 mag), resolving overestimated luminosities for LRDs in previous studies and alleviating a tension with the so-called Sołtan argument. This model predicts distinct spectral evolution as the binary orbit decays through binary disk interactions and gravitational-wave (GW) emission, linking early-stage “proto-LRD” binaries to the broader AGN population and late-stage “LRD descendants” to coalescing binaries detectable in GW experiments. https://research-explorer.ista.ac.at/download/21844/21853/2026_AstrophysicalJour_Inayoshi.pdf application/pdfno IOP Publishing2026 eng The Astrophysical Journal 0004-637X 1538-4357 2505.0532210.3847/1538-4357/ae548d 10021 Inayoshi K, Shangguan J, Chen X, Ho LC, Haiman Z. The emergence of Little Red Dots from binary massive black holes. The Astrophysical Journal. 2026;1002(1). doi:<a href="https://doi.org/10.3847/1538-4357/ae548d">10.3847/1538-4357/ae548d</a> Inayoshi, Kohei, et al. “The Emergence of Little Red Dots from Binary Massive Black Holes.” The Astrophysical Journal, vol. 1002, no. 1, 25, IOP Publishing, 2026, doi:<a href="https://doi.org/10.3847/1538-4357/ae548d">10.3847/1538-4357/ae548d</a>. K. Inayoshi, J. Shangguan, X. Chen, L.C. Ho, Z. Haiman, The Astrophysical Journal 1002 (2026). Inayoshi K, Shangguan J, Chen X, Ho LC, Haiman Z. 2026. The emergence of Little Red Dots from binary massive black holes. The Astrophysical Journal. 1002(1), 25. Inayoshi, Kohei, Jinyi Shangguan, Xian Chen, Luis C. Ho, and Zoltán Haiman. “The Emergence of Little Red Dots from Binary Massive Black Holes.” The Astrophysical Journal. IOP Publishing, 2026. <a href="https://doi.org/10.3847/1538-4357/ae548d">https://doi.org/10.3847/1538-4357/ae548d</a>. K. Inayoshi, J. Shangguan, X. Chen, L. C. Ho, and Z. Haiman, “The emergence of Little Red Dots from binary massive black holes,” The Astrophysical Journal, vol. 1002, no. 1. IOP Publishing, 2026. Inayoshi, K., Shangguan, J., Chen, X., Ho, L. C., & Haiman, Z. (2026). The emergence of Little Red Dots from binary massive black holes. The Astrophysical Journal. IOP Publishing. <a href="https://doi.org/10.3847/1538-4357/ae548d">https://doi.org/10.3847/1538-4357/ae548d</a> 218442026-05-10T22:02:14Z2026-05-11T07:09:12Z