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 the auto-correlation analysis ( ACF ) , we detect two significant ( at P > 99 \% ) periodic signals at \sim 741 day and \sim 1500 day from the 8.1-year 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 \sim 10 years .
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 } \sim 1500 day , we estimate the total virial masses of M _ { SMBHB } \sim 1.3 \times 10 ^ { 8 } M _ { \odot } , the average distances of BLR of \sim 0.04pc ( \sim 50 light-day , with \pm 0.3 dex uncertainty ) , and a SMBHB separation of d = ( 0.01pc ) M _ { 8 ,tot } ^ { 1 / 3 } ( T _ { rest } /3.3yr ) ^ { 2 / 3 } \sim 0.013 pc ( 15 light-day ) .
Based on analytical work , the postulated circumbinary disk has an inner radius of 2 d = 0.026 pc ( 30 light-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 .