Cosmic-ray anisotropies in right ascension measured by the Pierre Auger Observatory
Collaboration
13 pages
Published in:
- Astrophys.J. 891 (2020) 142
- Published: Mar 13, 2020
e-Print:
- 2002.06172 [astro-ph.HE]
DOI:
- 10.3847/1538-4357/ab7236 (publication)
Report number:
- FERMILAB-PUB-20-076,
- FERMILAB-PUB-20-076-ND-PPD-TD
Experiments:
Citations per year
Abstract: (arXiv)
We present measurements of the large-scale cosmic-ray anisotropies in right ascension, using data collected by the surface detector array of the Pierre Auger Observatory over more than 14 years. We determine the equatorial dipole component, , through a Fourier analysis in right ascension that includes weights for each event so as to account for the main detector-induced systematic effects. For the energies at which the trigger efficiency of the array is small, the ``East-West'' method is employed. Besides using the data from the array with detectors separated by 1500 m, we also include data from the smaller but denser sub-array of detectors with 750 m separation, which allows us to extend the analysis down to EeV. The most significant equatorial dipole amplitude obtained is that in the cumulative bin above 8~EeV, %, which is inconsistent with isotropy at the 6 level. In the bins below 8 EeV, we obtain 99% CL upper-bounds on at the level of 1 to 3 percent. At energies below 1 EeV, even though the amplitudes are not significant, the phases determined in most of the bins are not far from the right ascension of the Galactic center, at , suggesting a predominantly Galactic origin for anisotropies at these energies. The reconstructed dipole phases in the energy bins above 4 EeV point instead to right ascensions that are almost opposite to the Galactic center one, indicative of an extragalactic cosmic ray origin.Note:
- Accepted by ApJ •
- Submitted to ApJ
- cosmic radiation: anisotropy
- detector: surface
- trigger: efficiency
- dipole
- galaxy
- observatory
- Auger
References(33)
Figures(4)