Aartsen, M.G.Abraham, K.Ackermann, M.Adams, J.Aguilar, J.A.Ahlers, M.Ahrens, M.Altmann, D.Andeen, K.Anderson, T.Ansseau, I.Anton, G.Archinger, M.Argüelles, C.Auffenberg, J.Axani, S.Bai, X.Barwick, S.W.Baum, V.Bay, R.et al.2017-06-202017-06-202016The Astrophysical Journal: an international review of astronomy and astronomical physics, 2016; 830(2):1-120004-637X1538-4357http://hdl.handle.net/2440/106105IceTop is an air-shower array located on the Antarctic ice sheet at the geographic South Pole. IceTop can detect an astrophysical flux of neutrons from Galactic sources as an excess of cosmic-ray air showers arriving from the source direction. Neutrons are undeflected by the Galactic magnetic field and can typically travel 10 (E/PeV) pc before decay. Two searches are performed using 4 yr of the IceTop data set to look for a statistically significant excess of events with energies above 10 PeV (10¹⁶ eV) arriving within a small solid angle. The all-sky search method covers from −90° to approximately −50° in declination. No significant excess is found. A targeted search is also performed, looking for significant correlation with candidate sources in different target sets. This search uses a higher-energy cut (100 PeV) since most target objects lie beyond 1 kpc. The target sets include pulsars with confirmed TeV energy photon fluxes and high-mass X-ray binaries. No significant correlation is found for any target set. Flux upper limits are determined for both searches, which can constrain Galactic neutron sources and production scenarios.en© 2016. The American Astronomical Society. All rights reserved.Astroparticle physics; cosmic rays; methods: data analysisJournal article003005924610.3847/0004-637X/830/2/1290004004713000012-s2.0-84992735145260127