We conducted a systematic search for periodically varying quasars, which are predicted manifestations of sub-pc supermassive black hole binaries (SMBHBs), in the Pan-STARRS1 Medium Deep Survey (PS1 MDS). Since the normal variability of quasars can also mimic periodicity over a small number of cycles, we have extended the temporal baseline by monitoring the candidates with the Discovery Channel Telescope and the Las Cumbres Observatory telescopes. We have also adopted a more rigorous method to evaluate the significance of the periodic candidates, by considering in the light curves a red noise background modeled as the Damped Random Walk process. While none of the candidates can be resolved by the current pulsar timing arrays (PTAs) as individual gravitational wave sources, the Large Synoptic Survey Telescope is capable of finding more periodic candidates, some of which are likely to be detected by the PTA experiment with the Square Kilometre Array.
Publication Source (Journal or Book title)
Proceedings of the International Astronomical Union
Liu, T., Gezari, S., González, G., & Hynes, R. (2017). Supermassive Black Hole Binary Candidates from the Pan-STARRS1 Medium Deep Survey. Proceedings of the International Astronomical Union, 13 (S338), 46-52. https://doi.org/10.1017/S1743921318003617