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 MB ≥ -23.0, or -19.9 > MB > -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, αox indices, and other data. Our study shows that SBS NLS1s are strong or moderately strong soft X-ray sources with log LX = 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 LR < 40.0), and 52% of them are strong Fe II emitters (Fe II λ4570/Hβ > 1). The traditional linear correlation LX and Lop, 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 αox slope and Lop. 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).