Abstract
Emission of TeV γ-rays from the fast (periods less than 4 s) neutron stars in the X-ray binary systems Cyg X-3, Her X–1 and 4U0115 + 63 has recently been reported. Here we present the first evidence that the 283-s neutron star in the X-ray binary Vela X-1 radiates steady, pulsed TeV γ-rays with a sinusoidal light curve. This is also the first evidence that a wind-driven binary system radiates in this energy range. A periodic enhancement was also observed which was in phase with the steady pulsed emission and eight times stronger. This event was directly observable as an enhancement in the counting rate of the telescope and occurred while the pulsar was entering eclipse. This is considered to be an indication that the enhancement was caused by γ-ray production by a charged-particle beam interacting with the limb of the companion star. This fact further indicates that TeV γ-rays are not produced on the neutron star itself but in the accreting material in the system. This is probably the case with some of the other observed binaries.
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North, A., Raubenheimer, B., Jager, O. et al. Pulsed TeV gamma-rays from Vela X-1. Nature 326, 567–569 (1987). https://doi.org/10.1038/326567a0
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DOI: https://doi.org/10.1038/326567a0
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