  The gamma-ray binary LS I +61 303 is one of the brightest Fermi sources, with
orbitally modulated emission across the electromagnetic spectrum. Here we
present H-alpha spectra of LS I +61 303 that exhibit a dramatic emission burst
shortly before apastron, observed as a redshifted shoulder in the line profile.
A correlated burst in radio, X-ray, and GeV emission is observed at the same
orbital phase. We interpret the source of the emission as a compact pulsar wind
nebula that forms when a tidal mass stream from the Be circumstellar disk
interacts with the relativistic pulsar wind. The H-alpha emission offers an
important probe of the high energy emission morphology in this system.

High Energy Astrophysical Phenomena