Simultaneous long-term monitoring of LS I +61°303 by OVRO and Fermi-LAT

Abstract

Previous long-term monitorings of the gamma-ray-loud X-ray binary LS I +61°303 have revealed the presence of a long-term modulation of ~4.5 years. After nine years of simultaneous monitoring of LS I +61°303 by the Owens Valley Radio Observatory and the Fermi-LAT, two cycles of the long-term period are now available. Here we perform timing-analysis on the radio and the gamma-ray light curves. We confirm the presence of previously detected periodicities at both radio and GeV gamma-ray wavelengths. Moreover, we discover an offset of the long-term modulation between radio and gamma-ray data which could imply different locations of the radio (15 GHz) and GeV emission along the precessing jet.

8 pages, 7 figures, 2 tables, accepted for publication in MNRAS