Discovery of late-time X-ray flare and anomalous emission line enhancement after the nuclear optical outburst in a narrow-line Seyfert 1 Galaxy

CSS J102913+404220 is a peculiar narrow line Seyfert 1 galaxy with an energetic nuclear optical outburst. We present detailed analysis of its multi-wavelength photometric and spectroscopic observations covering period decade since detect mid-infrared (MIR) flares delayed by about two months relative to the outburst, extremely high peak luminosity log(L_4.6um)>44 erg/s. The MIR at least order magnitude higher than any known supernovae explosions, suggesting outburst might be due stellar tidal disruption event (TDE). find late-time X-ray brightening factor >30 respect what observed 100 days after peak, followed flux fading ~4 within weeks, making it one Active Galactic Nuclei (AGNs) extreme variability. Despite dramatic variability, there are no coincident strong variations in optical, UV bands. This unusual variability behavior has been seen other highly accreting AGNs could attributed absorption In this scenario, decrease absorber accretion rate cause brightening, possibly induced TDE. Most strikingly, while UV/optical continuum remains little changes time, evident enhancement H_alpha broad emission observed, which anomalous never AGNs. Such anomaly explained replenishment gas clouds excitation Broad Line Region (BLR) that originates, perhaps from interaction outflowing debris BLR. results highlight importance evolution TDE affect properties AGN, as suggested recent simulations.