Search for signals from Cygnus X-3 at energies above 50 TeV

Upper limits for the time-averaged flux of air showers from the direction of Cygnus X-3 during the calendar period April 2, 1986 to May 3, 1987 are found to be 1.5 x 10 to the -13th/sq cm per sec for all events, and 7.6 x 10 to the 14th/sq cm per sec for events with no observed muons in a 44-sq-m muon detector. These are integral fluxes above 50 TeV on the assumption of an 1/E primary spectrum. A possible observation of a short-term signal from Cygnus X-3, with an anomalous muon content, phase correlated with the 4.8-h orbital period and with an integral flux above 50 TeV of (8.2 + or - 2.0) x 10 to the -13th/sq cm per sec, is also reported. (Author)