Double-peaked Profile and Tidal Disruption Event of NGC 4203

In this work, we present the spectroscopic monitoring of the double-peaked profile of the AGN in the galaxy NGC 4203, based on 9 observations obtained over a timespan of 17 years. The broad double-peaked Hα profile showed significant variabilities during this period. Between the 2007 and 2010 observations, the line exhibited a 126% increase in flux accompanied by a broadening of the profile. An observation taken 4.5 months later showed a rapidly decrease 20% in the line flux and the narrowing of the profile. Observations in 2023 and 2024 show that the double-peaked profile stayed in a low flux and highly broad state. The observed variability is consistent with a scenario in which the accretion disc gives rise to the double-peaked profile while the increase in the line flux between 2007 and 2010 is interpreted as an increase in the amount of gas in the disc associated with a Tidal Disruption Event (TDE). To reproduce the observed profile variability, we propose a new modelling approach - called Emissivity Surface Modelling (ESM). This model assumes an accretion disc with Keplerian and relativistic orbits, inclined with respect to the plane of the sky, and featuring a multi-asymmetric surface emissivity. The results demonstrate that the ESM model successfully reproduces the temporal and structural variations of the double-peaked profile of NGC 4203, supporting the interpretation of a disc perturbed by a TDE as the origin of the observed variability.