A Disk-originated 329 Day Quasiperiodic Oscillation in the Seyfert 1 Galaxy J1626+5120

The Seyfert 1 galaxy J1626+5120 is estimated to host a 108M⊙ black hole (BH) accreting at Eddington ratio . Its long-term multiband light-curve data show flicker-like variations, but in a well-sampled g-band light curve, we are able to determine a ≃329 day quasiperiodic oscillation (QPO) at a ∼4.53σ significance. Six optical spectra were obtained for the source, three of which were taken by us. The spectra show that the variations were mainly because of flux changes blueward of 4000 Å. We also analyze X-ray and ultraviolet (UV) data obtained with the Neil Gehrels Swift Observatory (Swift), which targeted the source in the past 2 yr. X-ray and UV emissions of the source show variations correlated with optical. Time lags of four UV bands and four optical bands are determined with respect to the X-ray emission, which are consistent with a continuum reprocessing disk model. These properties point out a disk origin for the QPO, likely due to Lense–Thirring (LT) precession of the accretion flow at ∼20 gravitational radii of the BH. This QPO could be a key case linking subyear-long QPOs in jets, which have more cases reported, to LT precession.