A Spectral Framework for Testing the Quasi-Star Hypothesis in Little Red Dots I: Weighing LRDs by Their Super-Eddington Luminosity Ratios---No Signs of Overmassive Black Holes

Olivia Curtis, Nikko J. Cleri, Jakob M. Helton, Joel Leja, Jason T. Wright

First listed 2026-09-10 | Last updated 2026-09-08

Abstract

We present a spectral test of the quasi-star hypothesis for Little Red Dots (LRDs) whereby a black hole grows inside a stellar-like envelope. We use \texttt{Prospector} to fit host galaxies and \texttt{TLUSTY} photospheres to four LRDs that show strong molecular or atomic absorption. We approximate each object's electron-scattered Eddington luminosity ratio, $φ\equiv κ_{\rm es}σT_{\rm eff}^{4}/(gc)$, and we use \texttt{MESA-QUEST} to simulate their envelopes. All four are super-Eddington at $φ= 4.0$--$299$, although the largest value sits at the edge of our atmosphere grid and beyond our simulations. We derive envelope masses between $700$--$27{,}000\,M_\odot$, where quasi-star theory requires the black hole to be less than a third of that. GN-28074 falls five decades below its published virial mass estimate, alleviating the overmassive black hole problem. Their black holes double in mass every $\sim0.05$--$3.5$~Myr and can produce intermediate-mass black holes in $\lesssim30$~Myr. The two fitted components of the water-absorbing object WIDE-EGS-2974 share a single $φ$, consistent with our hypothesis that the absorption originates in an extended atmosphere. We then extend our measurements to 82 archival LRDs, finding super-Eddington photospheres throughout the population that launch winds at $1$--$3\times$ their own escape speeds, which implies that LRDs evolve from being massive, continuum-driven sources to more eruptive winds as they mature and shed their outer envelopes. We thus constrain the Eddington ratios and masses of LRDs, and, for the first time, show self-consistently that quasi-stars may be the central engines powering LRDs.

Short digest

Curtis et al. test whether little red dots can be quasi-stars, fitting Prospector host-galaxy models plus TLUSTY photospheres to four absorption-line LRDs and connecting the inferred temperatures, gravities, and luminosities to MESA-QUEST envelope calculations. All four primary sources are super-Eddington, with c6 = 4.0299, and yield 70027,000 M envelopes whose quasi-star mass caps place GN-28074 about five decades below its published virial black-hole mass estimate. Extending the analysis to 82 archival LRDs, the authors find population-wide super-Eddington photospheres and continuum-driven winds at roughly 13 times escape speed, interpreting the sequence as evolution from massive, slowly shedding envelopes to thinner, more eruptive ones. The most extreme c6 measurement lies at the boundary of the atmosphere grid and beyond the simulated regime, but the broader result argues that quasi-stars can reconcile LRD spectra and BHhost mass ratios without invoking overmassive black holes.

Key figures to inspect

• Figure 4. This is the papers core self-consistency test: fitted photospheric components are placed against the Eddington limit and iso-c6 curves, then compared directly with converged MESA-QUEST tracks. It shows how the observed LRD states map onto super-Eddington quasi-star envelope solutions and how wind evolution connects the fitted hot and cold components.
• Figure 5. This figure delivers the headline BHhost result. The quasi-star black-hole mass caps for the primary and archival LRDs lie on or below the local ReinesVolonteri relation, while GN-28074s published virial estimate is displayed as the discrepant comparison point.
• Figure 6. The full-sample temperaturegravity diagram establishes that the super-Eddington inference is not restricted to the four detailed fits. It makes the population-level selection and posterior constraints visible, including the explicitly excluded unconstrained fits and the placement of the water-absorbing cold components.
• Figure 7. This synthesis figure links envelope mass to outflow kinematics, supporting the proposed evolutionary interpretation. Its comparison to the continuum-driven wind limit shows that the measured LRD winds are consistent with radiation-dominated outflows, with low-c6 sources retaining the most massive, slowest envelopes.