Superorbital modulation of X-ray emission from gamma-ray binary LSI +61 303

摘要

We report the discovery of a systematic constant time lag between the X-rayand 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 weshow that the orbital phase of X-ray flares from the source varies from$\phi_X\simeq 0.35$ to $\phi_X\simeq 0.75$ on the superorbital 4.6 yr timescale. Simultaneous radio observations show that periodic radio flares alwayslag the X-ray flare by $\Delta\phi_{X-R}\simeq 0.2$. We propose that theconstant phase lag corresponds to the time of flight of the high-energyparticle filled plasma blobs from inside the binary to the radio emissionregion at the distance ~10 times the binary separation distance. We put forwarda hypothesis that the X-ray bursts correspond to the moments of formation ofplasma blobs inside the binary system.