Optical Variability and Evidence for a Changing-Look Event in the Galaxy Mrk 6 (IC 450)

In this work, the light curve of the Seyfert galaxy Mrk 6 constructed from photometric observations in the B, V, and Rc filters over the period from 5 April 2016 to 1 February 2026 is presented and analyzed. Over the entire monitoring interval (2016–2026), the variability amplitude of the light curve reaches ΔB=1.9 mag, ΔV=1.5 mag, and ΔRc=1.4 mag. During 2024–2026, the galaxy exhibits synchronous photometric variability in the B, V, and Rc filters with an amplitude of ∼0.3 mag. The study also uses spectroscopic observations obtained on 15 and 22 November 2025 and 16 February 2026 at the Shamakhy Astrophysical Observatory (Azerbaijan), as well as on 9 January 2026 at the Fesenkov Astrophysical Institute (Kazakhstan). The fluxes in the Hβ emission line were calibrated using the [O III] λ5007 Å line, ensuring consistent relative calibration of the spectral data. A comparison of the optical spectra reveals a pronounced transformation of the Hβ line profile between November 2025 and January 2026. The broad component, clearly present in November 2025, becomes strongly suppressed and nearly disappears in January 2026, while the narrow emission lines remain stable. This behavior is consistent with a changing-look transition, indicating a temporary weakening of the broad-line region emission. The radius of the broad-line region RBLR was taken to be equal to the average time delays (lags), amounting to ≈20 light days for the Hβ emission and ≈28 light days for the Hα.