Quasi-periodic Variations in the Radio Light Curves of Fermi Blazars

We search for possible periodicity in the MOJAVE (Monitoring Of Jets in Active Galactic Nuclei with VLBA Experiments) observations at 15.3 GHz of eight Fermi blazars using the REDFIT method. Possible periodic components of about 1.77, 8.69, 2.04 and 7.65 years are found in the sources 0851+202, 1308+326, 1641+399 and 2251+158 at a 99% confidence level, respectively. The super-massive binary black hole model and the helical jet model are used to explain these periodicities. And they are also used to caculate the central black hole masses of the four sources which are 10⁹M_⊙~10¹⁰M_⊙.