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The Close AGN Reference Survey (CARS): what is causing Mrk 1018’s return to the shadows after 30 years?

Husemann, B., Urrutia, T., Tremblay, G. R., Krumpe, M., Dexter, J., Busch, G., Combes, F., Croom, S. M., Davis, Timothy, Eckart, A., McElroy, R. E., Perez-Torres, M., Powell, M. and Scharwächter, J. 2016. The Close AGN Reference Survey (CARS): what is causing Mrk 1018’s return to the shadows after 30 years? Astronomy & Astrophysics 593 , L9. 10.1051/0004-6361/201629245

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Abstract

We recently discovered that the active galactic nucleus (AGN) of Mrk 1018 has changed optical type again after 30 yr as a type 1 AGN. Here we combine Chandra, NuStar, Swift, Hubble Space Telescope and ground-based observations to explore the cause of this change. The 2–10 keV flux declines by a factor of ~8 between 2010 and 2016. We show with our X-ray observation that this is not caused by varying neutral hydrogen absorption along the line-of-sight up to the Compton-thick level. The optical-UV spectral energy distributions are well fit with a standard geometrically thin optically thick accretion disc model that seems to obey the expected L ~ T4 relation. It confirms that a decline in accretion disc luminosity is the primary origin for the type change. We detect a new narrow-line absorber in Lyα blue-shifted by ~700 km s-1 with respect to the systemic velocity of the galaxy. This new Lyα absorber could be evidence for the onset of an outflow or a companion black hole with associated gas that could be related to the accretion rate change. However, the low column density of the absorber means that it is not the direct cause for Mrk 1018’s changing-look nature.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: accretion, accretion disks / galaxies: nuclei / galaxies: Seyfert / galaxies: individual: Mrk 1018
Publisher: EDP Sciences
ISSN: 0004-6361
Funders: STFC
Date of First Compliant Deposit: 20 June 2017
Date of Acceptance: 16 August 2016
Last Modified: 10 Jul 2017 11:18
URI: http://orca.cf.ac.uk/id/eprint/94552

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