Spectral and Photometric Studies of NGC 3516 in the Optical RangeSpectral and Photometric Studies of NGC 3516 in the Optical Range

(1) Background: NGC 3516 is an active Seyfert galaxy, which has become a focal point of astronomical studies due to its variable luminosity and emission lines, linked to the activity of its central supermassive black hole (SMBH). This paper presents an analysis of long-term observations from 2014 to 2024, including photometric and spectroscopic data collected at the Fesenkov Astrophysical Institute (FAI, Kazakhstan) and the Shamakhy Astrophysical Observatory (SHAO, Azerbaijan). The primary aim of this study was to investigate the changes in luminosity and spectral characteristics of NGC 3516, providing insights into the dynamics of the galaxy’s activity and its evolving chemical composition. (2) Methods: The research utilized photometric data in the B, V, R filters, along with spectroscopic observations in the wavelength range of λ4000 Å–λ7000 ÅThe spectroscopic data were normalized to analyze the profiles of emission lines and their variations over time. Broad emission line profiles (Hα and Hβ) were also analyzed to estimate radial velocities. A three-component model was applied, demonstrating a better statistical fit to the observed data, indicating a complex structure and dynamics within the galaxy’s Broad Line Region (BLR).; (3) Results: The main results of the study show that from 2018 to 2024, the brightness of NGC 3516 varied with amplitudes of ΔB=0.35 mag, ΔV=0.18 mag, ΔR=0.20 mag. An increase in brightness was observed in April 2020, likely associated with an X-ray flare detected simultaneously. Spectroscopic observations revealed a gradual weakening of the Hγλ4340 Å emission line starting from mid-2023. Narrow emission lines of [FeII] λ4814.53 Å and [FeVII] λ6087 Å were detected, indicating an active phase of the galaxy in May 2020. Photometric observations also revealed an increase in the object’s brightness in 2020. These observations suggest intriguing changes in the object’s activity, potentially indicating luminosity and chemical composition dynamics over the observed period. For the broad Hα line profile in the spectrum of NGC 3516, obtained with the AZT-8 on April 20, 2020, the radial velocity v=981−20+19 km/s. The radial velocity for the Hβ profile was 937−576+584 km/s; (4) Conclusions: Long-term observations of NGC 3516 have revealed significant changes in its luminosity and spectral characteristics, suggesting dynamic processes within the active nucleus of the galaxy. The observed variability in the broad emission line profiles could be linked to processes within the Broad Line Region (BLR) interacting with the SMBH and surrounding matter. These results may help in a more accurate estimation of the SMBH mass and provide deeper insights into the dynamics and evolution of active Seyfert galaxies.