The Close AGN Reference Survey (CARS) - Mrk 1018 returns to the shadows after 30 years as a Seyfert 1

TL;DR

The paper reports the second spectral type change of the changing look AGN Mrk 1018, which has reverted to a Seyfert 1.9, showing significant flux decrease likely due to intrinsic accretion disk variability.

Contribution

It provides new observational evidence of a second spectral type transition in Mrk 1018, highlighting intrinsic accretion disk flux changes as the cause.

Findings

Broad line flux decreased by a factor of 4.75 since 2000.

No significant change in Balmer decrement, indicating stable reddening.

Remaining broad lines are more asymmetric in the current phase.

Abstract

We report the discovery that the known `changing look' AGN Mrk 1018 has changed spectral type for a second time. New VLT-MUSE data taken in 2015 as part of the Close AGN Reference Survey (CARS) shows that the AGN has returned to its original Seyfert 1.9 classification. The CARS sample is selected to contain only bright type 1 AGN, but Mrk 1018's broad emission lines and continuum, typical of type 1 AGN, have almost entirely disappeared. We use spectral fitting of the MUSE spectrum and previously available spectra to determine the drop in broad line flux and the Balmer decrement. We find that the broad line flux has decreased by a factor of 4.75+/- 0.5 in H{\alpha} since an SDSS spectrum was taken in 2000. The Balmer decrement has not changed significantly implying no enhanced reddening with time, but the remaining broad lines are more asymmetric than those present in the type 1 phase. We posit that the change is due to an intrinsic drop in flux from the accretion disk rather than variable extinction or a tidal disruption event.