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Velocity offsets in the broad Balmer lines of quasars and their temporalvariations serve as indirect evidence for bound supermassive black holebinaries (SBHBs) at sub-parsec separations. In this work, we test the SBHBhypothesis for 14 quasars with double-peaked broad emission lines using theirlong-term (14--41 years) radial velocity curves. We improve on previous work by(a) using elliptical instead of circular orbits for the SBHBs, (b) adopting astatistical model for radial velocity jitter, (c) employing a Markov ChainMonte Carlo method to explore the orbital parameter space efficiently and buildposterior distributions of physical parameters and (d) incorporating newobservations. We determine empirically that jitter comprises approximatelyGaussian distributed fluctuations about the smooth radial velocity curves thatare larger than the measurement errors by factors of order a few. We initiallytreat jitter by enlarging the effective error bars and then verify thisapproach via a variety of Gaussian process models for it. We find lower masslimits for the hypothesized SBHBs in the range $10^8$--$10^{11}\;M_{\odot}$.For seven objects the SBHB scenario appears unlikely based on goodness-of-fittests. For two additional objects the minimum SBHB masses are unreasonablylarge ($>10^{10}\;M_{\odot}$), strongly disfavoring the SBHB scenario. Usingconstraints on the orbital inclination angle (which requires some assumptions)makes the minimum masses of four more objects unreasonably large. We also citephysical and observational arguments against the SBHB hypothesis for nineobjects. We conclude that the SBHB explanation is not the favoured explanationof double-peaked broad emission lines.

An Improved Test of the Binary Black Hole Hypothesis for Quasars with Double-peaked Broad Balmer Lines