Gamma-Ray Lines from SN1987A and Interpretation

Abstract

Gamma-ray lines from the decay of 56Co in the SN1987A remnant have been detected by satellite and balloon experiments. The observations directly confirm the basic theoretical tenet that 56Ni was explosively synthesized in the aftermath of core collapse of the blue super giant Sanduleak - 69 202. The flux level of the 56Co lines at 847 keV and 1238 keV, from the Gamma-Ray Spectometer (GRS) on the SMM satellite, is consistent with a constant level from 1987 August through 1988 May. The early appearence of the γ-ray lines and the continuum reported by the Ginga and Mir-Kvant satellite experiments require mixing, or clumping of a few percent of the newly synthesized 56Ni in the expanding envelope. Results from balloon experiments, which are in the preliminary stage of analysis, do not give clear evidence for γ-ray line shifts from rest energies with a limit ΔE/E ≤ 0.002, nor is there definitive evidence, at this time, of line splitting, but γ-ray line widths are clearly wider than instrument resolution at ΔE/E ≤ 0.02. The continuum (50–500) keV/line ratio has stayed approximately constant at 8 from 1987 August to 1988 May indicating the origin of the continuum from Compton down-scattering of deeper lying 56Co and lines from 56Co at smaller γ-ray optical depths. Future balloon flights of the most sensitive high-resolution spectrometers, planned for 1988 November and 1989 April, are expected to be able to detect weaker γ-ray lines at a flux level of ~ 10−4 γ cm−2 s−1 for the 847 keV line. SN1987A was just close enough to the Earth to confirm theory with existing instruments. In this report we review only γ-ray line results, since the continuum observations have been reviewed by Professor Trümper in this session.KeywordsLine FluxRest EnergyFlux LevelAstrophysical Journal56CO LineThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.