Thomas L. Jenkins

50–500 MeV observations of LMC supernova 1987A

Abstract Since the discovery of the supernova outburst in the LMC in 1987, we have made two attempts (on day 55 and day 407) to measure the high energy gamma-ray flux in the range 50–500 MeV, by using a balloon borne spark chamber telescope. On day 55, no positive signal was seen from the source. A 3σ upper limit of 2.9 × 10 −5 ph cm −2 s −1 was obtained after the analysis of the spark chamber data. Preliminary analysis of the quick look data obtained in the second flight shows that the gamma-ray flux even on day 407 was less than 9 × 10 −4 ph cm −2 s −1 (3 σ ).

A GAMMA-RAY TELESCOPE WITH ARC MINUTE RESOLUTION

A prototype imaging telescope of a kind that could be used in a future γ-ray astronomy mission has been tested using a quasi-point source of 20 MeV γ radiation. The results have demonstrated the ability to reconstruct images of the source at various positions within the field of view of the telescope. The point-spread function of the telescope was improved by nearly two orders of magnitude over that of a track chamber alone through the use of a coded aperture mask. This work has demonstrated for the first time the possibility of achieving arc minute source location with future γ-ray space telescopes. This would enable point-like γ-ray sources to be located with that precision while extended objects could be mapped with a resolution of about 10 arc min.

An imaging telescope for high energy gamma-ray astronomy

Abstract Recent tests of a γ-ray imaging telescope, which incorporated a coded aperture mask and multi-wire proportional counter system produced good images of a tritium target source which was used to generate the 20 MeV protons at a proton Van de Graaff accelerator. This paper indicates what performance one might expect if a large area drift chamber were used in conjunction with a coded aperture mask. The prospects for achieving significant scientific results if such a system were flown on a variety of space vehicles are discussed.

SN 1987A - The impact of greater than 50 MeV gamma-ray luminosity limits on theories of particle acceleration

Analysis of the data obtained from two flights of a balloonborne gamma-ray detector to observe SN 1987A was completed. The detector, which included a spark chamber to determine the arrival directions of the photons, was sensitive in the energy range 50-500 MeV. The 95 percent confidence upper limit to the flux on day 55 after the explosion has been established to be 1.1 x 10 exp -5 photons/sq cm/s and on day 407 to be 3.4 x 10 exp -5 photons/sq cm/s. These limits are compared with various theoretical predictions.