Study On Long-term Gamma-ray Variability Properties Of Blazar OJ 287

Since the Fermi Gamma-ray Space Telescope was launched successfully in 2008,it has observed blazars for nearly a decade.The observational data support good oppor-tunity to study long-term variability properties in gamma-ray of blazars.In this work,the long-term data of blazar OJ 287 from August 2008 to October 2016 were reduced.The gamma-ray variability characteristics,and the quasi-periodic oscillations of blazar OJ 287 were analyzed.We reduced the observational data in 100MeV-300GeV for about 8 years.During this period,five major flares were observed with asymmetric structure.The maximum flux can be reached 8×10^-7ph·cm^-2·s^-1.And the most rapid doubling timescale is less than 6 hr.The variability properties in low 100MeV-1GeV and high 1-300GeV energy range are similar to those in 100MeV-300GeV.Different models are used to fit the flares.The fitting results of different models have almost same spectral index?of blazar OJ 287 of about 2.The periodic modulations in the blazar OJ 287 were searched with the Lomb-Scargle Periodogram?LSP?.Two significant gamma-ray quasi-periodicity with a period of 313days and 715 days were found.However,the significances in both quasi-periodicities are less than 3?.Further long-term gamma-ray monitoring of the blazar OJ 287 is needed to confirm its quasi-periodicity.