Fermi Gamma-ray Space Telescope

Search for nuclear gamma-ray line emission from astrophysical sources in the GBM continuous spectral data - an update

A. von Kienlin

Abstract:

The poster gives an update on the evaluation of feasibility for using the GBM continuous CSPEC data for the detection of nuclear gamma-ray line emission from astrophysical sources. The GBM instrument provides continuous spectral data from all 14 detectors with a temporal binning of 4.096 s and 128 logarithmical spaced energy bands in the energy range from 8 keV to 1 MeV (NaI detectors) and from 200 keV to 40 MeV (BGO detectors), thus covering the energy range of interest for astrophysical nuclear lines. Since any point in the sky is always viewed by some of the GBM detectors at regular intervals the GBM CSPEC data can serve for such explorations. The main problem which strongly deteriorates the capabilities of GBM for this search is the highly varying background. In order to accomplish the aimed goal and to handle the background problem a dedicated analysis method is continually further developed. The different steps of the procedure are presented together with the results of an investigation of the background behavior. In addition estimates of sensitivities for line detection from nearby sources are given.