A Systematic Search for Periodically Varying Quasars in Pan STARRS1: An Extended Baseline Test in Medium Deep Survey Field MD09
We present a systematic search for periodically varying quasars and supermassive black hole binary (SMBHB) candidates in the Pan STARRS1 (PS1) Medium Deep Survey's MD09 field. From a color selected sample of 670 quasars extracted from a multi band deep stack catalog of point sources, we locally select variable quasars and look for coherent periods with the Lomb Scargle periodogram. Three candidates from our sample demonstrate strong variability for more than ~3 cycles, and their PS1 light curves are well fitted to sinusoidal functions. We test the persistence of the candidates' apparent periodic variations detected during the 4.2 years of the PS1 survey with archival photometric data from the SDSS Stripe 82 survey or new monitoring with the Large Monolithic Imager at the Discovery Channel Telescope. None of the three periodic candidates (including PSO J334.2028+1.4075) remain persistent over the extended baseline of 7 14 years, corresponding to a detection rate of 5 cycles) is crucial to our search for these systems.