Results of Gamma-Ray Balloon Astronomy

The results obtained from recent high~a1titude balloon flights of the Goddard 7-ray telescope with a digitized spark chamber are reported and combined with earlier work. The data on the region near the galactic center are reanalyzed in terms of a possible line source in the galactic plane. The analysis leads to a value of (2.3 ± 1.2) X 1O-~ y (cm2 sec rad)~ above 100 MeV for a galactic-latitude interval of -3° to +30 in the region near the galactic center; this result in itself does not justify the claim of a de- tected flux, but it is consistent with the line intensity of (4.1 ± 0.7) X 1O~ `y (cm2 sec rad)' quoted from recent OSO-Ill results. The flux and energy spectrum of the atmospheric background were measured as a function of angle with respect to the vertical. The measured downward flux is in reasonable agree- ment with measurements of other experimenters at several energies; however, the upward flux for ener- gies above 100 MeV is a factor of about three lower than that measured in the OSO-Jil experiment mentioned above. This difference seems larger than would be expected, but small compared with the difference between the galactic y-ray flux observed by OSO-IJI and the predicted one. The upper limits to possible point sources of y-rays are summarized and are shown generally to fall above the fluxes ex~ pected from a straight extrapolation of the X-ray spectra. No positive evidence for a point source has been found