Holes in the BH$^\star$? AGN signatures in the FUV spectrum of a black-hole dominated Little Red Dot at $z=7.04$

Xihan Ji, Gabriele Pezzulli, Francesco D'Eugenio, Roberto Maiolino, Stefano Carniani, Sandro Tacchella, Gareth Jones, Aaron Smith, Joris Witstok, Andrew C. Fabian, Sophia Geris, Anishya Harshan, Yuki Isobe, Lucy R. Ivey, Ignas Juodžbalis, Robert Pascalau, Jan Scholtz, Callum Witten

First listed 2026-04-03 | Last updated 2026-04-03

Abstract

It has been suggested that "Little Red Dots" (LRDs) might be accreting black holes enshrouded by dense gas in a nearly closed geometry, which completely covers the central black hole, leading to an atmosphere-like structure known as the "black-hole star" ($\rm BH^\star$). We test this scenario by analysing new JWST spectroscopy in the far ultraviolet (FUV, rest-frame) of the prototypical LRD Abell2744-QSO1, at $z=7.04$. We found the presence of broad Ly$α$ emission with an FWHM of $\sim 1000$ km/s, and detections of OI, CIV, and/or FeII emission lines. The NIRCam imaging and NIRSpec slit images indicate that the low-velocity component ($v\lesssim 200$ km/s) of Ly$α$ is likely spatially extended, but the high-velocity component ($v\gtrsim 200$ km/s) of Ly$α$ remains unresolved. Based on the multi-component kinematics and flux of Ly$α$ relative to Balmer lines, we conclude that the observed line profile is unlikely to be broadened by subsequent resonant scattering through the interstellar medium. This suggests that the high-velocity component of Ly$α$ originates in the broad-line region, although resonant scattering in the dense gas likely makes Ly$α$ broader than H$α$ as observed. The nebular features of this LRD indicate that there is at least one relatively optically thin direction where Ly$α$ can escape from the broad-line region (BLR). We also found indications that photons from the BLR are powering fluorescence of FeII and OI on a larger physical scale. The FUV features thus challenge the fully-covered geometry interpretation and suggest that there are "holes" in the $\rm BH^\star$, or the absorbing medium is simply clumpy.

Short digest

This paper examines far-ultraviolet AGN signatures in a black-hole-dominated little red dot at z = 7.04. The main result is that the FUV spectrum carries line and continuum evidence favoring an accretion-powered source despite the unusual broadband appearance of the system. The paper matters because FUV diagnostics probe a different physical window than the rest-optical LRD features that dominate current discussions.

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