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Volume 331 - Frontier Research in Astrophysics – III (FRAPWS2018) - Cosmology
Highlights of Pierre Auger Observatory
E. Santos* on behalf of the Pierre Auger Collaboration
*corresponding author
Full text: Not available
The existence of a cosmic ray flux of a still unknown origin with particles reaching energies millions of times higher than those attained at the LHC continues to intrigue the scientific community. The Pierre Auger Observatory, the largest cosmic ray detector in the world, was built to study the cosmic rays with $E > 10^{17}\;\mathrm{eV}$ with unprecedented statistics. Taking continuous data since 2004, the Pierre Auger Collaboration has published numerous results about the properties of Ultra-High Energy Cosmic Rays. Recently it has determined, with a $5.2\:\sigma$ significance, that the arrival directions of cosmic rays with energies above $8\:\mathrm{EeV}$ are anisotropic and can be described by a dipole whose direction favors an extragalactic origin of Ultra-High Energy Cosmic Rays. At an intermediate angular scale, the two largest departures from isotropy for the arrival directions of events with $E > 39\:\mathrm{EeV}$ and $E > 60\:\mathrm{EeV}$ are best described by a correlation with two nearby populations of extragalactic gamma-ray sources, namely starburst galaxies and AGNs. Photon and neutrino searches for events above $1\:\mathrm{EeV}$ and $0.1\:\mathrm{EeV}$, respectively, resulted in no candidates so far, allowing Auger to put stringent limits to the flux of these particles. In the multi-messenger astronomy era, Auger is actively participating in neutrino searches in coincidence with gravitational wave events. Currently, the Observatory is undergoing a major upgrade which aims at an improved determination, event-by-event, of the nuclear mass composition of cosmic rays near the region of the flux suppression
with increased statistics.
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