X-RAY SPECTRUM OF A PERIODIC QUASAR FROM THE DES: TESTING THE BINARY BLACK HOLE

We propose joint NuSTARXMMNewton observations of a periodically variablequasar recently found from the Dark Energy Survey (DES). The target is uniquebecause its periodicity is highly significant and robust thanks to the sensitiveDES imaging and a virgul20yr long time baseline by combining DES with SDSS. The highsensitivity and long baseline are both crucial to rejecting false positivescaused by quasars stochastic red noise variability. The proposed Xrayobservations will test and distinguish two generic but different sets of modelsof circumbinary accretion disk simulations (a central cavity vs. minidisks),which predict dramatically different Xray fluxes. The results will provide anindependent and complementary test for the binary black hole hypothesis to explain the periodicity. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]