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arXiv · 1501.01375

A possible close supermassive black-hole binary in a quasar with optical periodicity

Matthew J. Graham·S. George Djorgovski·Daniel Stern·Eilat Glikman·Andrew J. Drake·Ashish A. Mahabal·Ciro Donalek·Steve Larson·Eric Christensen
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Abstract

Quasars have long been known to be variable sources at all wavelengths. Their optical variability is stochastic, can be due to a variety of physical mechanisms, and is well-described statistically in terms of a damped random walk model. The recent availability of large collections of astronomical time series of flux measurements (light curves) offers new data sets for a systematic exploration of quasar variability. Here we report on the detection of a strong, smooth periodic signal in the optical variability of the quasar PG 1302-102 with a mean observed period of 1,884 $\pm$ 88 days. It was identified in a search for periodic variability in a data set of light curves for 247,000 known, spectroscopically confirmed quasars with a temporal baseline of $\sim9$ years. While the interpretation of this phenomenon is still uncertain, the most plausible mechanisms involve a binary system of two supermassive black holes with a subparsec separation. Such systems are an expected consequence of galaxy mergers and can provide important constraints on models of galaxy formation and evolution.

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Matthew J. Graham, S. George Djorgovski, Daniel Stern, Eilat Glikman, Andrew J. Drake, Ashish A. Mahabal, Ciro Donalek, Steve Larson, Eric Christensen. 2015-01-07. A possible close supermassive black-hole binary in a quasar with optical periodicity. https://doi.org/10.1038/nature14143

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