The Close AGN Reference Survey (CARS)

Mrk 1018 returns to the shadows after 30 years as a Seyfert 1

¹ Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006, Australia
e-mail: rmcelroy@physics.usyd.edu.au
² ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), Redfern NSW 2016, Australia
³ European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, 85478 Garching b. München, Germany
⁴ School of Physics & Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff, CF24 3AA, UK
⁵ Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407, USA
⁶ I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
⁷ LERMA, Observatoire de Paris, Collège de France, PSL, CNRS, Sorbonne Univ., UPMC, 75014 Paris, France
⁸ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁹ Instituto de Astrofisica de Andalucia (IAA), Glorieta de la Astronomía, s/n, 18008 Granada, Spain
¹⁰ Yale Center for Astronomy and Astrophysics, Yale University, 52 Hillhouse Ave., New Haven, CT 06511, USA
¹¹ Gemini Observatory, Northern Operations Center, 670 N. A’ohoku Place, Hilo, HI 96720, USA
¹² Leibniz-Institut füer Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany

Received: 13 June 2016
Accepted: 22 July 2016

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 Hα 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.