Results on candidate UHE gamma-ray sources by the EAS-TOP array (1989-1993)

M. Aglietta, B. Alessandro, P. Antonioli, F. Arneodo, L. Bergamasco, A. Campos Fauth, C. Castagnoli, A. Castellina, A. Chiavassa, G. Cini, B. D'Ettorre Piazzoli, G. Di Sciascio, W. Fulgione, P. Galeotti, P. L. Ghia, M. Iacovacci, G. Mannocchi, C. Morello, G. Navarra, L. RiccatiO. Saavedra, G. C. Trinchero, P. Vallania, S. Vernetto

Research output: Contribution to journalArticlepeer-review


A search for UHE gamma-rays from 13 candidate point sources observable in the northern hemisphere (the Crab Nebula and Pulsar, Cygnus X-3, Hercules X-1, Geminga and others) has been performed by the EAS-TOP array during four years of operation since January 1989 to December 1993, at different energy thresholds (E0 = 30-300 TeV). DC, periodic and sporadic emissions have been studied, and no evidence for significant excesses has been found from any of these searches. The derived 90% c.l. upper limits to the d.c. flux, for a source culminating at the zenith such as Cygnus X-3, are Φ(E > 230 TeV) < 2 × 10-14 cm-2 s-1, Φ(E > 90 TeV) < 4.1 × 10-14 cm-2 s-1 and Φ(E > 25 TeV) < 1.9 × 10-13 cm-2 s-1. The excess from the Crab Nebula of February 23, 1989, as reported by the EAS-TOP, Baksan and KGF arrays, remains the only sporadic excess detected with statistically significant confidence level (probability of background imitation ≈ 10-5).

Original languageEnglish (US)
Pages (from-to)1-15
Number of pages15
JournalAstroparticle Physics
Issue number1
StatePublished - Jan 1995

ASJC Scopus subject areas

  • Astronomy and Astrophysics


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