Dice Question Streamline Icon: https://streamlinehq.com

Physical origin of inverted mid-infrared variability amplitudes in two RCL AGNs

Determine the physical origin of the inverted mid-infrared variability pattern observed in the recurrent changing-look active galactic nuclei J1104+6343 and J1118+3203, specifically why the variability amplitude in the W1 (3.4 μm) band exceeds that in the W2 (4.6 μm) band, contrary to the typical redder-when-brighter behavior seen in most RCL AGNs.

Information Square Streamline Icon: https://streamlinehq.com

Background

The authors find that most recurrent changing-look AGNs show larger variability amplitudes in the W2 (4.6 μm) band than in W1 (3.4 μm), consistent with a redder-when-brighter trend commonly attributed to changes in the hot-dust covering factor in the torus.

However, two sources (J1104+6343 and J1118+3203) display the opposite behavior, with larger amplitudes in W1 than in W2. The authors explicitly state that the physical origin of this deviation is not yet clear and note it could be due to measurement uncertainties or differences in dust composition or geometry, requiring further observations.

References

Two sources, J1104+6343 and J1118+3203, display the opposite behavior, with larger amplitudes in W1 than in W2. The physical origin of this deviation is not yet clear, though we cannot rule out the possibility that it is caused by measurement uncertainties.

— Discovery of Repeating Transitions in 25 Changing-look Active Galactic Nuclei (2510.18445 - Dong et al., 21 Oct 2025) in Section 3.3 (Color changes in spectra and MIR light curves)