Too Quiet for Comfort: Local Little Red Dots Lack Variability over Decades
- 1Yale University
- 2University of Illinois at Urbana-Champaign
- 3Flatiron Institute
Abstract
Several local ( z ≲ 0.2) metal-poor dwarf active galactic nuclei (AGNs) have remarkably similar properties to those of high-redshift little red dots (LRDs), and are proposed to be local analogs of LRDs. We use long-term photometric and spectroscopic observations of three local LRDs spanning ∼20 yr to measure variability in their rest-frame optical continua and broad H α emission lines. Using Zwicky Transient Facility light curves over a rest-frame ∼5 yr baseline, the r -band intrinsic rms variability is ( 9 × 1 0 − 5 ) − 9 × 10 - 5 + 0.014 mag (J1022+0841), 0.025 ± 0.004 mag (J1025+1402) and 0.020 ± 0.005 mag (J1047+0739), indicating low intrinsic variability (<3%–4% at 3 σ ). These variability amplitudes are much lower than those for dwarf AGNs and more massive quasars. We constrain the broad H α variability to be less than a few percent, without significant profile changes, over a rest-frame baseline of ∼15 yr in J1025+1402 and J1047+0739, respectively. Local LRDs have exceptionally large H α equivalent widths and H α /H β ratios that far exceed the Case B recombination value, in contrast with normal broad-line AGNs. In the context of recent theoretical models of LRDs as dense gas-enshrouded massive black holes with super-Eddington accretion, our results suggest that the photosphere emission is long-term stable and the broad Balmer lines do not arise primarily by photoionization. This scenario is consistent with the lack of variability, large H α /H β ratios, little dust extinction, and expected high gas density. Virial black hole mass estimates using broad H α assuming photoionization are therefore highly questionable for LRDs.
Related
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BibTeX
@article{burke2026quiet,
title = {{Too Quiet for Comfort: Local Little Red Dots Lack Variability over Decades}},
author = {Colin J. Burke and Zachary Stone and Yue Shen and Yan-Fei 燕飞 Jiang 姜},
journal = {The Astrophysical Journal},
year = {2026},
month = jun,
doi = {10.3847/1538-4357/ae6b89},
url = {https://doi.org/10.3847/1538-4357/ae6b89},
note = {CC BY},
}
RIS
TY - JOUR
TI - Too Quiet for Comfort: Local Little Red Dots Lack Variability over Decades
AU - Colin J. Burke
AU - Zachary Stone
AU - Yue Shen
AU - Yan-Fei 燕飞 Jiang 姜
PY - 2026
DA - 2026/06/02
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae6b89
UR - https://doi.org/10.3847/1538-4357/ae6b89
AB - Several local ( z ≲ 0.2) metal-poor dwarf active galactic nuclei (AGNs) have remarkably similar properties to those of high-redshift little red dots (LRDs), and are proposed to be local analogs of LRDs. We use long-term photometric and spectroscopic observations of three local LRDs spanning ∼20 yr to measure variability in their rest-frame optical continua and broad H α emission lines. Using Zwicky Transient Facility light curves over a rest-frame ∼5 yr baseline, the r -band intrinsic rms variability is ( 9 × 1 0 − 5 ) − 9 × 10 - 5 + 0.014 mag (J1022+0841), 0.025 ± 0.004 mag (J1025+1402) and 0.020 ± 0.005 mag (J1047+0739), indicating low intrinsic variability (<3%–4% at 3 σ ). These variability amplitudes are much lower than those for dwarf AGNs and more massive quasars. We constrain the broad H α variability to be less than a few percent, without significant profile changes, over a rest-frame baseline of ∼15 yr in J1025+1402 and J1047+0739, respectively. Local LRDs have exceptionally large H α equivalent widths and H α /H β ratios that far exceed the Case B recombination value, in contrast with normal broad-line AGNs. In the context of recent theoretical models of LRDs as dense gas-enshrouded massive black holes with super-Eddington accretion, our results suggest that the photosphere emission is long-term stable and the broad Balmer lines do not arise primarily by photoionization. This scenario is consistent with the lack of variability, large H α /H β ratios, little dust extinction, and expected high gas density. Virial black hole mass estimates using broad H α assuming photoionization are therefore highly questionable for LRDs.
SN - 0004-637X
SN - 1538-4357
ER -