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. We 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 yr. 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 the disk-wind broad-line region model best explains the CL phenomenon. A variation of the total UV emission is not revealed when compared to the previous Galaxy Evolution Explorer NUV observation, since the UVOT images indicate that ∼90% UV emission comes from intensive star formation in the host galaxy.