SDSS J0159+0105: A RADIO-QUIET QUASAR WITH A CENTI-PARSEC SUPERMASSIVE BLACK HOLE BINARY CANDIDATE

We report a candidate centi-parsec supermassive black hole binary (SMBHB) in the radio-quiet quasar SDSS J0159+0105 at z = 0.217. With a modified Lomb-Scargle code (GLSdeDRW) and auto-correlation analysis, we detect two significant (at P > 99%) periodic signals at similar to 741 day and similar to 1500 day from the 8.1 yr Catalina V-band light curve of this quasar. The period ratio, which is close to 1:2, is typical of a black hole binary system with a mass ratio of 0.05 < q < 0.8 according to recent numerical simulations. SDSS J0159+0105 has two SDSS spectroscopic observations separated by similar to 10 yr. There is a significant change in the broad H beta profile between the two epochs, which can be explained by a single broad-line region (BLR) around the binary system illuminated by the aforementioned mini-disks, or a stream of gas flowing from the circumbinary disk to one of the SMBHs. From the single BLR assumption and the orbital period t(orb) similar to 1500 day, we estimate the total virial masses of M-SMBHB similar to 1.3 x 10(8) M-circle dot, the average distances of BLR of similar to 0.04 pc (similar to 50 lt-day, with +/- 0.3 dex uncertainty), and an SMBHB separation of d = (0.01 pc)M-8,tot(1/3) (T-rest/3.3 yr)(2/3) similar to 0.013 pc (15 lt-day). Based on analytical work, the postulated circumbinary disk has an inner radius of 2d = 0.026 pc (30 lt-day). SDSS J0159 +0105 also displays unusual spectral energy distribution. The unique properties of SDSS J0159+0105 are consistent with it being a centi-parsec SMBHB.