Observations of steady flux of PeV-energy extensive air showers from Cygnus X-3 during 1984-1986

Abstract

Data taken with a 24 detector extensive air shower array, operating at Ooty since 1984 June, have been used to search for excess of extensive air showers of energy > 2.5 × 10¹⁴ eV from the direction of binary X-ray source Cyg X-3. The data show a time-averaged excess in the number of showers from this direction, over the background determined from other regions of the sky having the same declination. The excess is most prominent among older showers having a flatter lateral distribution. A part of this excess shows up significantly in the phase region, 0.6-0.8 in the 4.8 hr periodicity analysis. These observations correspond to an integral flux of (7.16 ± 3.15) × 10^-13 cm ^-2 s^-1 at energies > 2.5 × 10¹⁴ eV and of (1.04 ± 0.44) × 10^-13 cm^-2 s^-1 at energies > 2.5 × 10¹⁵ eV. The observations confirm, for the first time, results reported by the Kiel group in 1983 of a directional excess from the direction of Cygnus X-3, without requiring the 4.8 hr periodicity analysis as was necessary in many of the other experiments reporting positive signals. This emphasizes the advantage of good angular resolution for such studies.