| Abstract: | We report on searches for neutrino sources at energies above 200 GeV in the
Northern sky of the galactic plane, using the data collected by the South Pole
neutrino telescopes IceCube and AMANDA. The galactic region considered here
includes the Local Arm towards the Cygnus region and our closest approach to
the Perseus Arm. The data have been collected between 2007 and 2009 when AMANDA
was an integrated part of IceCube, which was still under construction and
operated with 22-strings (2007-8) and 40-strings (2008-9) of optical modules
deployed in the ice. By combining the larger IceCube detector with the lower
energy threshold of the more compact AMANDA detector, we obtain an improved
sensitivity at energies below $sim$10 TeV with respect to previous searches.
The analyses presented here are: a scan for point sources within the galactic
plane; a search optimized for multiple and extended sources in the Cygnus
region, which might be below the sensitivity of the point source scan; and
studies of seven pre-selected neutrino source candidates. For one of them,
Cygnus X-3, a time-dependent search for neutrinos in coincidence with observed
radio and X-ray flares has been performed. No evidence of a signal is found,
and upper limits are reported for each of the searches. We investigate neutrino
spectra proportional to E$^{-2}$ and E$^{-3}$ to cover the entire range of
possible spectra. The soft E$^{-3}$ spectrum results in an energy distribution
similar to a source with cut-off below $sim$50 TeV. For the considered region
of the galactic plane, the 90% confidence level muon neutrino flux upper limits
are in the range E$^3$dN/dE$sim 5.4 - 19.5 imes 10^{-11}
m{TeV^{2} cm^{-2}
s^{-1}}$ for point-like neutrino sources in the energy region [180.0 GeV - 20.5
TeV]. These represent the most stringent upper limits for soft-spectra neutrino
sources within the Galaxy reported to date. |
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