High resolution phase resolved spectroscopy of the Crab

The Gamma Ray Imaging Spectrometer (GRIS) observed the Crab 31 May 1990. This balloon‐borne high resolution germanium spectrometer made a 9 hour observation of the Crab just a few weeks prior to the FIGARO II observation in which a possible red‐shifted annihilation line was reported. Phase resolved spectroscopy of the GRIS data places a three sigma upper limit for a pulsed narrow (2 keV) line at 4.1×10−5 photons cm−2 sec−1. If the feature reported by FIGARO was present during the GRIS observation, GRIS would have observed a line if its FWHM was less than 10 keV. The Crab total spectrum was fit by a power law of spectral index 2.15±0.03 and a 100 keV flux of 4.52±0.18 photons cm−2 sec−1 keV−1.