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A strong outburst in the X-ray continuum and a change of its Seyfert spectraltype was detected in HE 1136-2304 in 2014. The spectral type changed fromnearly Seyfert 2 type (1.95) to Seyfert 1.5 type in comparison to previousobservations taken ten to twenty years before. In a subsequent variabilitycampaign we wanted to investigate whether this outburst was a single event orwhether the variability pattern following the outburst was similar to thoseseen in other variable Seyfert galaxies. In addition to a SALT spectralvariability campaign, we carried out optical continuum as well as X-ray and UV(Swift) monitoring studies from 2014 to 2017. HE 1136-2304 strongly varied ontimescales of days to months from 2014 to 2017. No systematic trends were foundin the variability behavior following the outburst in 2014. A general decreasein flux would have been expected for a tidal disruption event. This could notbe confirmed. More likely the flux variations are connected to irregularfluctuations in the accretion rate. The strongest variability amplitudes havebeen found in the X-ray regime: HE 1136-2304 varied by a factor of eight during2015. The amplitudes of the continuum variability (from the UV to the optical)systematically decreased with wavelength following a power law F_var = a${\times}$ {\lambda}^-c with c = 0.84. There is a trend that the B-bandcontinuum shows a delay of three light days with respect to the variable X-rayflux. The Seyfert type 1.5 did not change despite the strong continuumvariations for the period between 2014 and 2017.

Long-term optical, UV, and X-ray continuum variations in the changing-look AGN HE 1136-2304