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

Abstract

Upper limits for the time-averaged flux of air showers from the direction of Cygnus X-3 during the calendar period 2 April 1986 to 3 May 1987 are found to be 1.5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ for all events, and 7.6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}14}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ for events with no observed muons in a 44-${\mathrm{m}}^{2}$ muon detector. These are integral fluxes above 50 TeV on the assumption of an ${E}^{\mathrm{\ensuremath{-}}1}$ 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, with an integral flux above 50 TeV of (8.2\ifmmode\pm\else\textpm\fi{}2.0)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ is also reported.