Weekly issue · Nov 9–11, 2026

Week 46, 2026

3 curated papers

01arXiv:2611.12861v1

Theme match 4/5

Little Red Dots from Primordial Black Holes: Non-Gaussianity and Accretion Evade $μ$-Distortion Constraints

Shyam Balaji, Bryce Cyr, Sarah R. Geller et al.

This paper asks whether primordial black holes can provide the massive seeds needed for the JWST little red dot population without violating COBE/FIRAS limits on CMB μ-distortions. Using MCMC fits for broad lognormal and cut-power-law primordial power-spectrum enhancements, including local non-Gaussianity, nonlinear density mapping, and post-formation accretion, the authors find viable LRD-seeding models with |fNL| of order unity and peak power A of order 10^-3 under standard Eddington-limited growth. Both positive and negative fNL branches can reproduce the inferred LRD abundance, but the negative branch is accretion-history dependent and disappears for low black-hole duty cycles (fduty ≲ 0.1). The result reopens a primordial-seed route to early SMBHs and makes future μ-distortion experiments a direct test of that scenario.

Figure notes (5)

Figure 1. This overview connects the allowed small-scale curvature-power enhancements to the PBH mass range relevant for JWST LRDs, while showing why direct Gaussian seed formation is excluded without either efficient accretion or non-Gaussianity. It also places COBE/FIRAS and projected FOSSIL sensitivity alongside the viable templates.
Figure 2. This figure gives the clearest direct demonstration of the paper's central non-Gaussianity result: both positive and negative local fNL values can intersect the observed LRD number-density band for fixed broad-spectrum templates.
Figure 4. This posterior plot isolates the bimodal positive- and negative-fNL solutions in the lognormal model, making clear that the two branches are distinct statistical pathways to the required seed abundance rather than a single broad Gaussian-like solution.
Figure 7. This duty-cycle comparison is the key caveat figure because it shows how the joint μ-distortion-plus-LRD constraints change with accretion efficiency, including the loss of the negative-fNL preference when fduty becomes small.
Figure 9. This late synthesis figure compares the lognormal and cut-power-law MCMC posteriors under the same μ+LRD likelihood, showing that the main viable-seed conclusion is not tied to one specific broad power-spectrum parameterization.

02arXiv:2611.09397v1

Theme match 4/5

Where the red rise stops: JWST/MIRI reveals a near-infrared turnover in the Little Red Dot Abell2744-QSO1

E. Iani, P. Rinaldi, A. Torralba et al.

JWST/MIRI photometry of the lensed z=7.04 Little Red Dot Abell2744-QSO1 finds its red continuum turns over near rest-frame 1 μm, tightening energy-budget constraints but leaving dust reddening versus dense-gas reprocessing unresolved.

What changes The reported advance is the placement of two MIRI constraints beyond the previously emphasized rest-optical SED, directly locating where QSO1’s red rise stops. Among tested interpretations, super-Eddington models with a thermalising envelope reproduce that turnover, but only with a black-hole mass ∼2.5 dex below the dynamical estimate. Thus the new points expose tension in both a simple dense-cocoon disc and the quoted envelope realization, rather than uniquely selecting a model. The authors propose MIRI imaging beyond 18 μm as the discriminant between dust reddening and dense-gas processing.

LRD
spectroscopy
high-z

Figure notes (5)

Figure 2. This is the central observational result: QSO1’s optical rise flattens between F770W and F1000W, establishing a near-infrared turnover by rest-frame 1.24 μm and showing that a roughly 4450 K blackbody or a reddened hotter continuum can fit the measured SED.
Figure 3. This comparison places QSO1 among other LRDs and against type-1 quasar templates, making the missing quasar-like hot-dust rise immediately visible while emphasizing that LRD continua diverge at wavelengths beyond the present coverage.
Figure 6. This figure connects the new MIRI constraint to the model-selection argument: the highest-evidence stellar solutions demand an implausibly large stellar mass, whereas the dynamically permitted accretion-disc cocoon solution over-predicts F1000W.
Figure 7. This energy-budget diagnostic quantifies the dust-reddening alternative: hot dust near 1200 K can reradiate only a few percent of the absorbed luminosity without violating the data, requiring most obscured power to emerge at much cooler temperatures if dust has a large covering fraction.
Figure 8. This synthesis figure shows which dust temperatures can hide the absorbed luminosity and demonstrates why deeper MIRI imaging at longer wavelengths can discriminate between a reddened accretion disc and dense-gas processing.

03arXiv:2611.10140v1

Theme match 2/5

Probing circumstellar interaction with spectroscopy of ZTF hydrogen-rich superluminous supernovae

Yang Hu, Ragnhild Lunnan, Priscila J. Pessi et al.

Across 304 ZTF optical spectra of 106 H-rich superluminous supernovae, Balmer-line modeling and comparisons support dense circumstellar interaction, but reveal no line morphology unique to SLSNe-IIn; blue-excess objects are typically fainter and favor faster fitted emitting shells.

What changes The principal advance is the scale of a homogeneous ZTF spectroscopic assessment of H-rich SLSNe and the application of electron-scattering Hα-profile modeling across it. The work separates a dominant narrow-line interacting population from a single broad-lined SLSN-II, flags possible flash-ionisation and Ia-CSM-like subsets, and reports that some SLSNe-IIn maintain high-ionisation emission for prolonged periods. The authors interpret the ensemble as supporting dense CSM created by enhanced pre-explosion mass loss and raise, rather than confirm, a hidden Ia-CSM population among luminous interacting H-rich SNe.

broad Balmer
spectroscopy

Figure notes (5)

Figure 4. This representative post-peak spectral montage establishes the central observational result: substantial diversity in the evolution of narrow Balmer-line SLSNe despite their common interacting classification.
Figure 5. The selected Hα profiles provide the clearest visual taxonomy of the symmetric, blue-excess, and broad-shouldered morphologies that the electron-scattering interpretation seeks to explain.
Figure 11. The Hα pEW comparison directly supports the paper’s conclusion that SLSNe-IIn overlap spectroscopically with lower-luminosity SNe IIn rather than defining a distinct Balmer-line population.
Figure 14. The time-resolved Balmer decrement diagnostic shows the evolution from near Case-B values to larger late-time ratios and distinguishes the ZTF SLSNe-IIn population from the Ia-CSM comparison sample.
Figure 19. These late spectral sequences compare blue-shoulder SLSNe-IIn with SN 2013L, making the paper’s key point tangible: even striking asymmetric Balmer morphologies have analogues among ordinary interacting SNe.