B3\,0749+460A: A New "Changing-Look" Active Galactic Nucleus Associated with X-ray Spectral Slope Variations

TL;DR

This paper reports the discovery of a new changing-look active galactic nucleus (CL-AGN) that exhibits spectral type transitions and X-ray spectral slope variations, providing insights into the connection between optical and X-ray properties in AGNs.

Contribution

It presents the first multi-epoch spectroscopic and X-ray analysis of B3 0749+460A, revealing its changing-look nature and linking spectral changes to X-ray spectral slope variations.

Findings

Type transitions from Sy 1.9 to Sy 1.8 and back observed.

Disappearance of broad Hα emission over time.

X-ray emission decreases and spectral slope varies with optical state.

Abstract

Here we report an identification of B3\,0749+460A as a new double-peaked local "changing-look" active galactic nucleus (CL-AGN) in terms of our multi-epoch spectroscopic analysis. By comparing our new spectra taken in 2021 with the ones taken by the Sloan Digital Sky Survey in 2004, BOSS in 2013, and MaNGA in 2016, we reveal type transitions of Seyfert (Sy) 1.9$\rightarrow$Sy1.8$\rightarrow$Sy1.9. In the transitions, the classical broad H$\alpha$ emission fades away since 2013, and disappears in our 2021 spectrum, although the absence of broad H$\beta$ can be traced back to at least 2016. A follow-up observation in X-rays by the {\it Swift}/XRT reveals that (1) the X-ray emission level gradually decreases since 2005; and (2) the X-ray spectrum is soft in the optical "turn-off" state and hard in the "turn-on" state. We argue that the disappearance of the classical broad H$\alpha$ emission can be likely explained by the disk-wind broad-line-region model, in which the CL phenomenon is sensitive to luminosity in individual AGNs.