ИСТИНА

Optical and near-infrared photometry, optical spectroscopy, and soft X-ray and UV monitoring of the changing-look active galactic nucleus NGC 2617 show that it continues to have the appearance of a type-1 Seyfert galaxy. An optical light curve for 2010–2017 indicates that the change of type probably occurred between 2010 October and 2012 February and was not related to the brightening in 2013. In 2016 and 2017 NGC 2617 brightened again to a level of activity close to that in 2013April. However, in 2017 from the end of the March to the December it was in very low level and starting to change back to a Seyfert 1.8. The UV and X-ray fluxes reach minimal levels for all time of observations (since 1982) at the beginning of December. We find strong variations both in the intensities and profiles of the broad Balmer lines. A new displaced emission peak has appeared in Hβ. X-ray variations are well correlated with UV–optical variability and possibly lead by ~2–3 d. The K band lags the J band by about 21.5 ± 2.5 d and lags the combined B + J bands by ~25 d. J lags B by about 3 d. This could be because J-band variability arises predominantly from the outer part of the accretion disc, while K- band variability is dominated by thermal re-emission by dust. We propose that spectral-type changes are a result of strong variations of central luminosity causing sublimation or re-creation of the innermost dust in the hollow bi-conical outflow. We briefly discuss various other possible reasons that might explain the dramatic changes in NGC 2617.