The Quasar SDSS J1536+0441: An Unusual Double-peaked Emitter

Abstract

The quasar SDSS J153636.22+044127.0, exhibiting peculiar broad emission- line profiles with multiple components, was proposed as a candidate sub-parsec binary supermassive black hole system. More recently, imaging revealed two spatially distinct sources, leading some to suggest that the system was a quasar pair separated by åisebox-0.5ex 5 kpc. We present Palomar and Keck optical spectra of this system from which we identify a third velocity component to the emission lines. We argue that the system is more likely an unusual member of the class of active galactic nuclei known as ``double-peaked emitters’’ than a sub-parsec black hole binary or quasar pair. We find no significant velocity evolution of the two main peaks over the course of 0.95 yr, with a 3σ upper limit on any secular change of 70 km s1 yr1. We also find that the three velocity components of the emission lines are spatially coincident to within 0farcs015 along the slit, apparently ruling out the double-quasar hypothesis.

Publication
Astrophysical Journal Letters

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