Gamma-ray imaging of the Crab and Vela regions with the UCR double-Compton telescope.

摘要

Results are presented for a new imaging technique applied to the reconstruction of celestial gamma-ray source images. This algorithm uses an expectation maximization maximum likelihood method (EMML) and is applied to the UCR double Compton telescope. First, this technique is used with simulated data and preflight calibration data. It is then applied to the Crab pulsar/Nebula, and Vela regions. These data were collected in 1988 from Alice Springs, Australia and in 1989 from Fort Sumner, NM.; An excess of 1200 counts from the Crab has been detected at 4{dollar}sigma{dollar} in the energy range 1-30 MeV, 920 counts at 3.1{dollar}sigma{dollar} in the energy range 1-5 MeV and 202 counts at 2.7{dollar}sigma{dollar} in the energy range 5-10 MeV. The total measured flux from 1-30 MeV is {dollar}(2.0 pm 0.5) times 10sp{lcub}-3{rcub}{dollar} photons cm{dollar}sp{lcub}-2{rcub}{dollar} s{dollar}sp{lcub}-1{rcub}.{dollar} Pulsar analysis was also performed. The pulsed flux in the energy range 1-30 MeV is equal to {dollar}(1.4 pm 0.4) times 10sp{lcub}-4{rcub}{dollar} photons cm{dollar}sp{lcub}-2{rcub}{dollar} s{dollar}sp{lcub}-1{rcub}.{dollar} Only upper limits for the pulsed flux have been placed in the individual energy ranges of 5-10 MeV and 10-30 MeV. Our results are compared with other experiments.; The Vela region image shows an excess of 575 counts in the energy range 1.1-30 MeV at 2.7{dollar}sigma{dollar}, 340 counts at 2.4{dollar}sigma{dollar} in the energy range 1.1-5 MeV and 130 counts from 5 to 10 MeV at 2.2{dollar}sigma{dollar}. No excess is seen above 10 MeV. The total flux for the energy range 1.1 to 30 MeV is equal to {dollar}(1.0 pm 0.4) times 10sp{lcub}-3{rcub}{dollar} photons cm{dollar}sp{lcub}-2{rcub}{dollar} s{dollar}sp{lcub}-1{rcub}.{dollar} The Vela pulsed flux in the energy range 1.1 to 30 MeV is equal to {dollar}(3.5 pm 1.4) times 10sp{lcub}-4{rcub}{dollar} photons cm{dollar}sp{lcub}-2{rcub}{dollar} s{dollar}sp{lcub}-1{rcub}.{dollar} The ratio of pulsed flux to total flux in the energy range 1.1-30 MeV, is found to be equal to 0.35 {dollar}pm{dollar} 0.2.