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Arxiv: Analysis of Multi-epoch JWST Images of \sim 300 Little Red Dots: Tentative Detection of Variability in a Minority of Sources Published: 11/5/2024 3:55:48 AM Updated: 11/5/2024 3:55:48 AM

Paper abstract: James Webb Space Telescope (JWST) has revealed a population of red andcompact sources at z \gtrsim 5 known as "Little Red Dots" (LRDs) that arelikely active galactic nuclei (AGNs). Here we present a comprehensive study ofthe variability of 314 LRDs with multi-epoch JWST observations in five deepfields: UDS, GOODS-S, GOODS-N, Abell 2744, and COSMOS. Our analyses use allpublicly available JWST NIRCam imaging data in these fields, together withmulti-epoch JWST MIRI images available. We measure the significance of thevariabilities (signal-to-noise ratio or {\rm SNR}_{\rm var}) for all LRDs andstatistically evaluate their variabilities using the {\rm SNR}_{\rm var}distributions. We pay particular attention to the systematic offsets ofphotometric zero points among different epochs that seem to commonly exist. Thederived {\rm SNR}_{\rm var} distributions of the LRDs, including those withbroad H\alpha/H\beta emission lines, follow the standard Gaussiandistribution, and are generally consistent with those of the comparison samplesof objects detected in the same images. This finding suggests that the LRDpopulation on average does not show strong variability, which can be due tosuper-Eddington accretion of the black holes in AGNs. Alternatively, they aredominated by galaxies. We also find eight strongly variable LRD candidates withvariability amplitudes of 0.24 - 0.82 mag. The rest-frame optical SEDs of thesevariable LRDs should have significant AGN contribution. Future JWSTobservations will provide more variability information of LRDs.