VERITAS Observations of the gamma-Ray Binary LS I +61 303

Understand

LS I +61 303 is one of only a few high-mass X-ray binaries currently detected at high significance in very high energy gamma-rays.

• The system was observed over several orbital cycles (between September 2006 and February 2007) with the VERITAS array of imaging air-Cherenkov telescopes.
• A signal of gamma-rays with energies above 300 GeV is found with a statistical significance of 8.4 standard deviations.
• The detected flux is measured to be strongly variable; the maximum flux is found during most orbital cycles at apastron.