Seminar by Jiachen Jiang, Leverhulme/Isaac Newton Fellow – Institute of Astronomy (University of Cambridge, UK)
Tuesday 4th of April, 2.30 pm (On-line seminar. Link: https://meet.google.com/ots-rija-hyc)
“Unlike the stochastic variability in the optical and UV emission of active galactic nuclei (AGN), more significant change is seen in some less common AGN transients. Their optical emission is found to change significantly within a much shorter time interval than the viscous timescales given by the standard disc model. Some of these peculiar galaxies also switch look between type-1 and type-2 AGN by presenting the appearance or disappearance of broad optical permitted lines along with magnitude changes.
In this talk, I will present an X-ray, UV and optical look of the type-1 AGN KUG 1141+371. It shows a simultaneous flux increase in the optical and UV bands in the past decade. For instance, the Swift observations in 2019 show that its far-UV flux has increased by over one order of magnitude since 2009. Meanwhile, the soft X-ray flux of KUG 1141+371 also shows a steady increase by almost one order of magnitude from 2007 to 2019 and a very rapid decay ever since 2020. The significant multi-wavelength luminosity change is likely due to a boost followed by a quick drop-in mass accretion rate. At odds, the optical spectrum of KUG 1141+371 never changes look. Finally, I will discuss the possible connection between KUG 1141+371 and a stellar-mass black hole X-ray binary and other AGN transients in outburst.”