X-ray spectra reveal the reawakening of the repeat changing-look AGN NGC 1566

We present simultaneous XMM-Newton and NuSTAR observations of the repeat changing-look AGN NGC 1566, which dramatically increased in brightness in the IR to X-ray bands in 2018. The broad-band X-ray spectrum was taken at the peak of the outburst and is typical of Seyfert 1 AGN. The spectrum shows a soft excess, Compton hump, warm absorption and reflection, ruling out tidal disruption as the cause of the outburst and demonstrating that a `standard' accretion disk can develop very rapidly. The high-resolution grating spectrum reveals that the outburst has launched a ∼500 km s^-1 outflow, and shows photoionized emission lines from rest-frame gas. We discuss possible mechanisms for the outburst, and conclude that it is most likely caused by a disk instability.