2017ApJ...842...10Z

We search for γ-ray and optical periodic modulations in distant flat-spectrum radio quasar (FSRQ) PKS 0426-380 (the redshift z = 1.1). Using two techniques (i.e., the maximum likelihood optimization and the exposure-weighted aperture photometry), we obtain γ-ray light curves from Fermi-LAT Pass 8 data covering from 2008 August to 2016 December. We then analyze the light curves with the Lomb-Scargle periodogram and the weighted wavelet Z-transform. A γ-ray quasi-periodicity with a period of 3.35 ± 0.68 yr is found at the significance level of ≃3.6 σ . The optical-UV flux covering from 2005 August to 2013 April provided by the ASI Science Data Center is also analyzed, but no significant quasi-periodicity is found. It should be pointed out that the result of the optical-UV data could be tentative because of the incompleteness of the data. Further long-term multiwavelength monitoring of this FSRQ is needed to confirm its quasi-periodicity.