Optical Identification of Candidates for Active Galactic Nuclei Detected by the Mikhail Pavlinsky ART-XC Telescope Onboard the SRG Observatory during an All-Sky X-ray Survey

We present the results of our identification of eight objects from the preliminary catalogue of X-ray sources detected in the 4–12 keV energy band by the Mikhail Pavlinsky ART-XC telescope onboard the SRG observatory during the first all-sky survey. Three of them (SRGA J005751.0+210846, SRGA J $$014157.0{-}032915$$ , SRGA J232446.8+440756) have been discovered by the ART-XC telescope, while five have already been known previously as X-ray sources, but their nature has remained unestablished. The last five sources have also been detected in soft X-rays by the eROSITA telescope of the SRG observatory. Our optical observations have been carried out at the 1.6-m AZT-33IK telescope of the Sayan Observatory and the 1.5-m Russian–Turkish telescope (RTT-150). All of the investigated objects have turned out to be active galactic nuclei (AGNs) at redshifts from 0.019 to 0.283. Six of them are Seyfert 2 galaxies (including one Seyfert 1.9 galaxy), one (SRGA J005751.0+210846) is a ‘‘hidden’’ AGN (in an edge-on galaxy), and one (SRGA J224125.9+760343) is a narrow-line Seyfert 1 galaxy. The latter object is characterized by a high X-ray luminosity ( $${\sim}(2-13)\times 10^{44}$$ erg s $${}^{-1}$$ in the 4–12 keV band) and, according to our black hole mass estimate ( $${\sim}2\times 10^{7}M_{\odot}$$ ), an accretion rate close to the Eddington limit. All three AGNs discovered by the ART-XC telescope (which are not detected by the eROSITA telescope) are characterized by a high absorption column density ( $$N_{\textrm{H}}\gtrsim 3\times 10^{23}$$ cm $${}^{-2}$$ ). The results obtained confirm the expectations that the ART-XC telescope is an efficient instrument in searching for heavily obscured and other interesting AGNs in the nearby ( $$z\lesssim 0.3$$ ) Universe. The SRG sky survey will last for another 3 years or more, which must allow many such objects to be discovered.