An X-ray Luminosity-dependent "Changing-look" Phenomenon in UGC 3223
Abstract
The nature of the rare "Changing-look" (CL) phenomenon in active galactic nuclei (AGNs) is still under debate at current stage. We here present Swift/ XRT and UVOT follow-up observations of UGC\,3223, a newly discovered repeat CL-AGN with type transitions of S1.5→ S2 → S1.8 occurring in a period of about 30 years. By comparing the values previously reported in the ROSAT All-sky Survey and in the second Swift-XRT Point Source catalog, we clearly find that the X-ray flux tightly follows the optical spectral transition, in which a spectral type closer to a Seyfert 1 type is associated with a higher X-ray flux. An invariable X-ray spectral shape is, however, found in the CL phenomenon of the object. An extremely low Eddington ratio of 2×10-4 can be obtained from the X-ray luminosity for its Seyfert 2 state, which suggests a favor of the disk-wind broad-line region model in explaining the CL phenomenon. A variation of the total UV emission is not revealed when compared to the previous GALEX NUV observation, since the UVOT images indicate that 90\% UV emission comes from the intensive star formation in the host galaxy.