Possible Quasi-periodic Modulation in the z = 1.1 Gamma-Ray Blazar PKS 0426–380

Abstract

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 . 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.