The Astrophysical Journal, Volume 679, Issue 2, pp. 1427-1432.
Abstract: 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. The energy spectrum for the period of maximum emission can be characterized by a power law with a photon index of Gamma=2.40+-0.16_stat+-0.2_sys and a flux above 300 GeV corresponding to 15-20% of the flux from the Crab Nebula.
Additional Information:
Differential energy spectrum of VHE photons above 300 GeV for LS I +61 303 around apastron (orbital phases 0.5–0.8). Taken from Fig.2 in V.A.Acciari et al, The Astrophysical Journal, Volume 679, Issue 2, pp. 1427-1432 (arXiv:0802.2363)):
Energy dN/dE
[TeV] [cm^{-2}s^{-1}TeV^{-1}]
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0.37 2.83e-11 +- 1.14e-11
0.53 1.25e-11 +- 3.66e-12
0.74 6.70e-12 +- 1.49e-12
1.05 2.23e-12 +- 6.37e-13
1.48 1.24e-12 +- 3.17e-13
2.09 6.62e-13 +- 1.93e-13
2.99 <1.96e-13
4.18 7.00e-14 +- 3.48e-14
5.96 <4.14e-14
