Obscured Binary Quasar Cores in SDSS J104807.74+005543.5?”, Astrophys

We report the discovery of a possible close binary system of quasars in SDSS J10480055. The [O iii] ll4959, 5007 emission lines are clearly double-peaked, and two discrete radio sources with a projected physical separation of ∼20 pc are found in the Very Long Baseline Array milliarcsecond resolution image at 8.4 GHz. Each of the [O iii] ll4959, 5007 doublets and Hb can be well modeled by two Gaussians, and the line ratio [O iii] is typical of Seyfert 2 galaxies. No broad component of Hb was detected, and its [O iii] l5007l5007/Hb ∼ 7 luminosity, ergs s1, is comparable to luminous quasars and is a few #10 more luminous42L ≈ 9.2 # 10[O iii] than typical Seyfert galaxies. One natural interpretation is that SDSS J10480055 contains two close quasar-like nuclei, and the broad-line region around them is obscured. Other possible models are also discussed. We suggest that a double-peaked narrow emission line profile may be an effective way of selecting candidates of binary black holes with intermediate separation