INTEGRAL Image Gallery Comissioning and performance/verification phase
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SPECTROMETER SPI
Gamma-ray line emission in the energy range 2-8 MeV
The SPI telescope aboard INTEGRAL has detected during the period from 9-Nov-2002 (12:00) and 11-Nov-2002 (12:00) a considerable increase of gamma-ray line emission in the energy range 2-8 MeV. In particular, broadened and shifted gamma-ray lines have been observed around 2216 keV, 3009 MeV, and 4452 keV. Increased but narrow gamma-ray line emission has also been seen at 6129 keV.
The increase of gamma-ray line flux is correlated with an increase of the SPI anticoincidence (ACS) overall counting rate, and an increase of the 1-100 MeV proton flux as seen by GOES8
(see
http://www.lmsal.com/solarsoft/last_events ).
The origin of the gamma-ray lines is not fully understood so far, yet the measurements impressively demonstrate the capacity of SPI to perform detailed studies of gamma-ray line profiles. For example, the spectrum at 2.2 MeV is composed of a narrow instrumental background line at the rest energy of the deuterium line (2223 keV), and a broadened and possible redshifted line with a mean energy of 2216 keV and a width of 16 keV (FWHM). Subtracting off the instrumental background removes the narrow deuterium line and reveals the excess emission during the flare period.
A more detailed study of the event and a more refined analysis of the data, which were acquired only 5 days after the switch-on of the SPI Germanium camera, is in progress.
