The third catalog of high-energy gamma-ray sources detected by the EGRET telescope on the Compton Gamma Ray Observatory includes data from 1991 April 22 to 1995 October 3 (cycles 1, 2, 3, and 4 of the mission). In addition to including more data than the second EGRET catalog and its supplement, this catalog uses completely reprocessed data (to correct a number of mostly minimal errors and problems). The 271 sources (E [ 100 MeV) in the catalog include the single 1991 solar Ñare bright enough to be detected as a source, the Large Magellanic Cloud, Ðve pulsars, one probable radio galaxy detection (Cen A), and 66 high-conÐdence identiÐcations of blazars (BL Lac objects, Ñat-spectrum radio quasars, or unidentiÐed Ñat-spectrum radio sources). In addition, 27 lower conÐdence potential blazar identiÐcations are noted. Finally, the catalog contains 170 sources not yet identiÐed Ðrmly with known objects, although potential identiÐcations have been suggested for a number of those. A Ðgure is presented that gives approximate upper limits for gamma-ray sources at any point in the sky, as well as information about sources listed in the second catalog and its supplement, that do not appear in this catalog.

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Interactions of 10.6A GeV gold nuclei have been studied in nuclear emulsions. In a minimum bias sample of 1100 interactions, 4730 helium nuclei and 2102 heavy nuclei were emitted as fragments of the incident gold projectiles. The emission angles of these fragments have been measured and pseudorapidity distributions constructed. The multiplicity distributions have been considered separately for the light and heavy target nuclei in the emulsions and found to be relatively independent of the nature of the target, when studied in terms of the total charge remaining bound in the multiply charged fragments. These distributions have been compared with those reported by experiments that studied the multifragmentation of 0.6 and 1.0A GeV gold nuclei, and show relatively small but statistically significant differences that may be attributed to the differing energies or, possibly, to detection biases in the low energy data. We have also looked for evidence of phase changes in the description of multifragmentation and compared our conclusions with those of a study of 1.0A GeV gold nuclei interacting in a carbon target. We see evidence of behavior that is similar, but not entirely consistent, with that reported at the lower energy. Whether this is evidence for a true phase change in the state of the nuclear matter remains an open question. PACS number(s): 25.75+r, 29.40.Rg

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