The Awakening Beast in the Seyfert 1 Galaxy KUG 1141+371

KUG 1141+371 is a Seyfert 1 galaxy that shows a significant simultaneous flux increase followed by a rapid decay from the optical to the X-ray bands in the past 13 years. For instance, Swift observations show that the UVW2 and X-ray flux of the AGN in KUG 1141+371 steadily increased by a factor of 10 from 2009 to 2020 and has followed a rapid decay ever since 2020. The significant multi-wavelength luminosity change is likely due to a boost in mass accretion rate. The timescale of such mass accretion changes is much shorter than the viscosity timescale of the disc assuming the measured black hole mass of 100 million solar masses for KUG 1141+371.

I will present a detailed multi-epoch X-ray spectral analysis focusing on the variability of the X-ray continuum emission and the puzzling soft excess emission. In addition, our SED models also suggest a simultaneous increase in disc temperature and a decreasing inner disc radius along with the increasing accretion rate. Simultaneous ground-based optical observations also show significant changes in the permitted line profiles and optical continuum. Finally, I will discuss the possible connection between KUG 1141+371, stellar mass-black hole transients in outburst and changing-look AGN.