Mass limits on particles from pulsed sources: How reliable are they?

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Abstract
It is widely believed that the arrival at Earth of pulsed emission from a cosmic accelerator such as Cygnus X-3 puts mass limits on the particles carrying the radiation of order 1 GeV. We show that these simple kinematic estimates are unreliable and can often be avoided. The actual mass limit depends critically on the detailed structure of the pulse, i.e., on (i) the shape of the flux as a function of energy and (ii) the minimum and maximum energies. We illustrate this by showing that masses of 100 GeV or more for the ‘‘cygnets’’ responsible for the unexplained pulsed muon signal from Cygnus X-3 can be made consistent with present experiments. These masses are large enough to accommodate the 3° angular spread of the muon pulses and to exclude the production of cygnets in accelerator experiments.