We report the discovery of a systematic constant time lag between the X-ray and radio flares of the gamma-ray binary LSI +61 303, persistent over long, multi-year, time scale. Using the data of monitoring of the system by RXTE we show that the orbital phase of X-ray flares from the source varies from ϕX≃0.35 to ϕX≃0.75 on the superorbital 4.6 yr time scale. Simultaneous radio observations show that periodic radio flares always lag the X-ray flare by ΔϕX−R≃0.2. We propose that the constant phase lag corresponds to the time of flight of the high-energy particle filled plasma blobs from inside the binary to the radio emission region at the distance ~10 times the binary separation distance. We put forward a hypothesis that the X-ray bursts correspond to the moments of formation of plasma blobs inside the binary system.
@article{arxiv.1203.1944,
title = {Superorbital modulation of X-ray emission from gamma-ray binary LSI +61 303},
author = {M. Chernyakova and A. Neronov and S. Molkov and D. Malyshev and A. Lutovinov and G. Pooley},
journal= {arXiv preprint arXiv:1203.1944},
year = {2012}
}