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The Search for Supermassive Black Hole Binary Candidates in the Optical Time Domain


Tingting Liu (University of Maryland)

April 17 @ 12:00 PM - 1:00 PM

Supermassive black hole binaries (SMBHBs) should be common products of the hierarchical growth of galaxies and the loudest expected sources of low-frequency gravitational waves. Periodic quasar variability has been predicted as an observational signature of SMBHBs, due to modulated mass accretion or relativistic Doppler boosting. We have conducted a systematic search for periodically varying quasars in the Pan-STARRS1 Medium Deep Survey and identified 26 candidates from ~9,000 color-selected quasars in a ~50 deg^2 sky area. We further extend the baseline of observations via our imaging campaign with the Discovery Channel Telescope and the Las Cumbres Observatory network telescopes. We then reevaluate the candidates using a more rigorous, maximum likelihood method by searching for a periodic component in addition to red noise, which is modeled as the Damped Random Walk process or a broken power law power spectrum. We also apply our method to the well-known periodic quasar and SMBHB candidate PG1302-102 using extended data from ASAS-SN and find evidence for the lack of persistence over a baseline of ~15 years. I will conclude with a discussion of the exciting capabilities of LSST to discover SMBHBs that can potentially be detected by the next generation of pulsar timing arrays.