A Multiwavelength Study of Narrow‐Line Seyfert 1 Galaxies from the Second Byurakan Survey

In this work we present a multiwavelength study of narrow-line Seyfert 1 galaxies (NLS1s) discovered in the Second Byurakan Survey (SBS). The sample consists of 26 objects, which have M B ≥ -23.0, or -19.9 > M B > -23.0, 0.0243 < z < 0.317, and 15.2 < B < 19.0. For these objects, we present accurate coordinates, magnitudes, redshifts, and the identification of optical objects with X-ray, IR, and radio sources. Several galaxies are identified as X-ray or radio sources for the first time. We also report spectroscopic and photometric data, the spectral energy distribution, α ox indices, and other data. Our study shows that SBS NLS1s are strong or moderately strong soft X-ray sources with log L X = 42.8-45.4. Soft X-ray-luminous sources in our sample do not tend to be luminous in the infrared. All SBS NLS1s are radio-quiet objects (log L R < 40.0), and 52% of them are strong Fe II emitters (Fe II λ4570/Hβ > 1). The traditional linear correlation L X and L op , which seems to hold for active galactic nuclei in general, is found for SBS NLS1s. An anticorrelation between the FWHM of Hβ and the ratio of Fe II λ4570/Hβ is also observed. A weak correlation is found between α ox slope and L op . One of our main findings is that almost all SBS NLS1s may not have an FIR bump. Their spectral energy distribution suggests that they may also possess a big blue bump. The absence of an IR bump in most SBS NLS1s and the weakness of X-ray radiation in some of them may argue against the presence of a broad-line region. The surface density of SBS NLS1s is less than 0.015 deg -2 ( B < 17.5, z < 0.16).