A comprehensive search for gamma-ray lines in the first year of data from the INTEGRAL spectrometer.
TEEGARDEN B.J. and WATANABE K.
Abstract (from CDS):
We have carried out an extensive search for gamma-ray lines in the first year of public data from the spectrometer (SPI) on the INTEGRAL mission. INTEGRAL has spent a large fraction of its observing time in the Galactic plane with particular concentration in the Galactic center (GC) region (∼3 Ms in the first year). Hence the most sensitive search regions are in the Galactic plane and center. The phase space of the search spans the energy range 20-8000 keV and line widths from 0 to 1000 keV (FWHM). It includes both diffuse and pointlike emission. We have searched for variable emission on timescales down to ∼1000 s. Diffuse emission has been searched for on a range of different spatial scales from ∼20° (the approximate field of view of the spectrometer) up to the entire Galactic plane. Our search procedures were verified by the recovery of the known gamma-ray lines at 511 and 1809 keV at the appropriate intensities and significances. We find no evidence for any previously unknown gamma-ray lines. The upper limits range from a fewx10–5 to a fewx10–2 cm–2.s–1 depending on line width, energy, and exposure; regions of strong instrumental background lines were excluded from the search. Comparison is made between our results and various prior predictions of astrophysical lines.