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Astrophysics and Astronomy | Physical Sciences and Mathematics
The Whipple Observatory 10 m γ-ray telescope has been used to survey the error boxes of EGRET unidentified sources in an attempt to find counterparts at energies of 350 GeV and above. Twenty-one unidentified sources detected by EGRET (more than 10% of the total number) have been included in this survey. In no case is a statistically significant signal found in the EGRET error box, which implies that, at least for this sample, the γ-ray spectra of these sources steepen between 100 MeV and 350 GeV. For each EGRET source location, we list candidate associations and derive upper limits on the integral γ-ray flux above 350 GeV.
Fegan, S. J. et al. (2005) ‘A Survey of Unidentified EGRET Sources at Very High Energies’, The Astrophysical Journal, 624(2), pp. 638–655. doi: 10.1086/429123.