摘要：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.
