2021ApJ...919...13Z

In this manuscript, we report a new changing-look QSO (CLQSO) SDSS J2241 at z = 0.059. Based on the multi-epoch Sloan Digital Sky Survey spectra from 2011 to 2017, the flux ratio of broad Hα to broad Hβ has changed from 7 in 2011 to 2.7 in 2017, leading SDSS J2241 with a spectral index α_λ ∼ -5.21 ± 0.02 (λ < 4000) in 2017 to be, so far, the bluest CLQSO. Based on the SDSS spectrum in 2011, the host galaxy contribution with a stellar velocity dispersion of ∼86 km s^–1 can be well determined, leading to the M-sigma relation expected central black hole (BH) mass of ∼3 x 10⁶ M_☉. However, based on properties of the broad Hα emission, the virial BH mass is ∼10⁸ M_☉, about two magnitudes larger than the mass found through the M-sigma relation. The different BH masses found using different methods indicate that SDSS J2241 is one unique CLQSO. The long-term photometric light curve shows interesting variability that is not expected assuming the Damped Random Walk process commonly applied to active galactic nuclei but probably connected to a central tidal disruption event. Furthermore, based on continuum emission properties in 2017 with no dust obscuration, the moving dust clouds scenario alone cannot be preferred to explain the CLQSO SDSS J2241, because the expected intrinsic reddening-corrected continuum emission was unreasonably higher than the unobscured continuum emission in 2017.