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

TL;DR

This study analyzes the peculiar emission-line profiles of quasar SDSS J1536+0441, providing evidence that it is an unusual double-peaked emitter rather than a binary black hole system or quasar pair, based on spectral and spatial data.

Contribution

The paper presents new optical spectra revealing a third velocity component and spatially coincident emission lines, challenging previous binary or quasar pair interpretations.

Findings

No significant velocity change over 0.95 years.

Three velocity components are spatially coincident within 0.015".

The system is more consistent with a double-peaked emitter than a binary black hole.

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 the system to be a quasar pair separated by ~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 (AGNs) 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 3-sigma upper limit on any secular change of 70 km/s/yr. We also find that the three velocity components of the emission lines are spatially coincident to within 0.015" along the slit, apparently ruling out the double-quasar hypothesis.