A PERIODICALLY VARYING LUMINOUS QUASAR AT z=2 FROM THE PAN-STARRS1 MEDIUM DEEP SURVEY: A CANDIDATE SUPERMASSIVE BLACK HOLE BINARY IN THE GRAVITATIONAL WAVE-DRIVEN REGIME

作者：Liu Tingting^*; Gezari Suvi; Heinis Sebastien; Magnier Eugene A; Burgett William S; Chambers Kenneth; Flewelling Heather; Huber Mark; Hodapp Klaus W; Kaiser Nicholas; Kudritzki Rolf Peter; Tonry John L; Wainscoat Richard J; Waters Christopher

来源：Astrophysical Journal Letters, 2015, 803(2): L16.

DOI：10.1088/2041-8205/803/2/L16

• quasars: general
• surveys

Supermassive black hole binaries (SMBHBs) should be an inevitable consequence of the hierarchical growth of massive galaxies through mergers and the strongest sirens of gravitational waves (GWs) in the cosmos. Yet, their direct detection has remained elusive due to the compact (sub-parsec) orbital separations of gravitationally bound SMBHBs. Here, we exploit a theoretically predicted signature of an SMBHB in the time domain: periodic variability caused by a mass accretion rate that is modulated by the binary's orbital motion. We report our first significant periodically varying quasar detection from the systematic search in the Pan-STARRS1 (PS1) Medium Deep Survey. Our SMBHB candidate, PSO J334.2028+01.4075, is a luminous radio-loud quasar at z = 2.060, with extended baseline photometry from the Catalina Real-Time Transient Survey, as well as archival spectroscopy from the FIRST Bright Quasar Survey. The observed period (542 +/- 15 days) and estimated black hole mass (log(M-BH/M-circle dot)= 9.97 +/- 0.50) correspond to an orbital separation of 7(-4)(+8) Schwarzschild radii (similar to 0.006(-0.003)(+0.007) pc), assuming the rest-frame period of the quasar variability traces the orbital period of the binary. This SMBHB candidate, discovered at the peak redshift for SMBH mergers, is in a physically stable configuration for a circumbinary accretion disk and within the regime of GW-driven orbital decay. Our search with PS1 is a benchmark study for the exciting capabilities of LSST, which will have orders of magnitude larger survey power and will potentially pinpoint the locations of thousands of SMBHBs in the variable night sky.

• 出版日期2015-4-20