Supermassive Black Hole Binary Candidates from the Pan-STARRS1 Medium Deep Survey
Speaker: Tingting Liu, University of Maryland
We present a systematic search for periodically varying quasar and supermassive black hole binary (SMBHB) candidates in the Pan-STARRS1 Medium Deep Survey. From ~9,000 color-selected quasars in a ~50 deg^2 sky area, we identify 26 candidates with more than 1.5 cycles of variation. We extend the baseline of observations via our imaging campaign with the Discovery Channel Telescope and the Las Cumbres Observatory network and reevaluate the candidates using a more rigorous, maximum likelihood method; 3 candidates remained significant, if we assume the variability of all normal quasars are characterized by the Damped Random Walk process. The down-selected “gold” sample translates to an SMBHB rate of 0.3 per 10^3 quasars out to z~2, in tension with previous work by Graham et al. (2015) and Charisi et al. (2016). We also find that the binary residence times of the “gold” sample are best matched to the expected distribution if the mass ratio q = 0.3. Using our study with MDS as a benchmark, we estimate that ~10,000 periodic quasars with more than 3 cycles could be discovered by the Large Synoptic Survey Telescope, paving the way for the direct detection of individual gravitational wave sources by future pulsar timing array experiments.
Characterising exoplanet atmospheres as part of the LRG-BEASTS survey
Speaker: James Kirk, University of Warwick