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 the auto-correlation analysis ACF, we detect two significant
(at P>99%) periodic signals at ~741 day and ~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 ~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 ~1500 day, we estimate the total virial masses of
M_SMBHB ~ 1.3x10^8 M_sun, the average distances of BLR of ~0.04pc (~50
light-day, with +/-0.3 dex uncertainty), and a SMBHB separation of d=
(0.01pc)M_{8,tot}^{1/3} (T_rest/3.3yr)^{2/3} ~ 0.013 pc (15 light-day). Based
on analytical work, the postulated circumbinary disk has an inner radius of 2d
= 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.
  The GLSdeDRW code link: http://butler.lab.asu.edu/qso_period/
