G A ] 1 7 A pr 2 01 9 SDSS J 153636 . 22 + 044127 . 0 and its analogues : shocked outflows , not active binary black holes

The binary emission-line system, particularly the binary broad-line emission system, is considered the most effective indicator of the black hole binary. A plausible example of such a system, SDSS J153636.22+044127.0, was reported as the first known object with two hydrogen Balmer broad-line systems, which are interpreted to be the result of broad-line regions around a pair of black holes (Boroson & Lauer 2009). Here, we show the follow-up optical and nearinfrared spectral observations of SDSS J153636.22+044127.0 and its analogues. In these objects, the broad hydrogen Balmer and Paschen, He I and Mg II lines share the same peculiar emissionline profile (including a blue system, a red system and a double-peaked disk-line component); however, the invariance in the large time interval, the absence of the blue system in He I λ10830 profile and the abnormally strong emission of the hydrogen Paβ blue system oppose the binary proposal. We suggest that these unique broad lines arise from the AGN emission-line region and the shock-heated outflowing gases rather than a binary system of two active black holes. Subject headings: black hole physics – quasars: emission lines – quasars: individual (SDSS J153636.22+044127.0)