Super-orbital Variability of LS I +61° 303 Binary

LS I +61° 303 is a high mass gamma-ray binary with a compact object revolving around a massive B0 Ve star. It has been extensively studied from radio to TeV energies. In addition to an orbital period, a long term super-orbital modulation at 1667 days was first observed in radio. The super-orbital variability has been confirmed by the multiwavelength observations from optical to gamma rays and is possibly related to the expansion and shrinkage of the circumstellar disk of the companion star. Evidence for a super-orbital period in TeV observations has been claimed by Ahnen et al (2016), based on two super-orbital periods. Here we extend this analysis over a longer timescale which covers 3.5 super-orbital periods. Using 174 hours of VERITAS data collected over a decade, we present the study of gamma-ray emission from the binary and a search for the super-orbital period in the orbital phase 0.5 to 0.75.