Observation and search for γ rays 1–20 MeV from the Crab, NGC4151, Cyg X-1, Cyg X-3, CG135+1 and 3C273

Abstract

Observiations of γ rays of 1–20 MeV with the UCR Compton double scatter γ ray telescope are reported for a balloon flight launched from Palestine, Texas, 4.5 GV, at 01.00 UT 29 September 1978. The energy distribution of the total γ rays from the Crab from 1.2 to 20 MeV is measured. Two δ upper limits of 3, 2, 0.6 and 0.4 × 10⁻⁴ photons cm⁻² s⁻¹ MeV⁻¹ at energies 1.2–3, 3–5, 5–10 and 10–20 MeV, respectively, are found for the Seyfert galaxy NGC4151, the black hole candidate Cyg X-1 and for Cyg X-3. In the same energy intervals, the 2σ upper limits for the nearest and second nearest QSOs CG135 + 1 and 3C273 are 5,3,1 and 0.4 × 10⁻⁴ photons cm⁻² s⁻¹ MeV⁻¹. These upper limits restrict confirmed γ-ray sources at 1–20 MeV to the Crab and NP0532. Our upper limits for NGC4151 do not support Seyfert galaxies as the source of cosmic diffuse radiation¹.