Analysis of Multi-epoch JWST Images of ∼300 Little Red Dots: Tentative Detection of Variability in a Minority of Sources

Abstract The James Webb Space Telescope (JWST) has revealed a population of red and compact sources at z ≳ 5 known as “little red dots” (LRDs) that are likely active galactic nuclei (AGNs). Here, we present a comprehensive study of the variability of 314 LRDs with multi-epoch JWST observations in five deep fields: Ultra Deep Survey, GOODS-S, GOODS-N, A2744, and COSMOS. Our analyses use all publicly available JWST NIRCam imaging data in these fields, together with multi-epoch JWST MIRI images available. We measure the significance (signal-to-noise ratio or SNR var ) of the variabilities for all LRDs and statistically evaluate their variabilities using the SNR var distributions. We pay particular attention to the systematic offsets of photometric zero-points among different epochs that seem to commonly exist. The derived SNR var distributions of the LRDs, including those with broad H α /H β emission lines, follow the standard Gaussian distribution, and are generally consistent with those of the comparison samples of objects detected in the same images. This finding suggests that the LRD population, on average, does not show strong variability, which can be explained by super-Eddington accretion of the black holes in AGNs. Alternatively, many of them may be dominated by galaxies. We also find eight strongly variable LRD candidates with variability amplitudes of 0.24–0.82 mag. The rest-frame optical spectral energy distributions of these variable LRDs should have a significant AGN contribution. Future JWST observations will provide more variability information on LRDs.