Using H-alpha as a Tracer of the Emission Region of LS I +61 303

TL;DR

This study uses H-alpha spectral observations of LS I +61 303 to link emission bursts across multiple wavelengths to a pulsar wind nebula formed by interactions with the Be star's disk, revealing insights into the system's high-energy processes.

Contribution

It presents the first detailed H-alpha spectral analysis correlating emission bursts with high-energy activity in LS I +61 303, proposing a new interpretation of the emission region.

Findings

H-alpha spectra show a dramatic emission burst before apastron.

Correlated bursts observed in radio, X-ray, and GeV emissions.

Emission interpreted as a pulsar wind nebula interacting with the Be star's disk.

Abstract

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.