We present measurements of the large-scale cosmic-ray (CR) anisotropies in R.A., using data collected by the surface detector array of the Pierre Auger Observatory over more than 14 yr. We determine the equatorial dipole component, through a Fourier analysis in R.A. 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 subarray of detectors with 750 m separation, which allows us to extend the analysis down to ∼0.03 EeV. The most significant equatorial dipole amplitude obtained is that in the cumulative bin above 8 EeV, %, which is inconsistent with isotropy at the 6σ level. In the bins below 8 EeV, we obtain 99% CL upper bounds on d ⊥ at the level of 1%-3%. 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 R.A. of the Galactic center, at GC =-94°, suggesting a predominantly Galactic origin for anisotropies at these energies. The reconstructed dipole phases in the energy bins above 4 EeV point instead to R.A. that are almost opposite to the Galactic center one, indicative of an extragalactic CR origin.

Cosmic-Ray anisotropies in right ascension measured by the Pierre Auger Observatory / Aab, A., Abreu, P., Aglietta, M., Albuquerque, I.F.M., Albury, J.M., Allekotte, I., Almela, A., Castillo, J.A., Alvarez-Muiz, J., Anastasi, G.A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P.R.A., Asorey, H., Assis, P., Avila, G., Badescu, A.M., Bakalova, A., et al.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 891:2(2020), pp. 1-10. [10.3847/1538-4357/ab7236]

Cosmic-Ray anisotropies in right ascension measured by the Pierre Auger Observatory

Mastrodicasa M.;
2020

Abstract

We present measurements of the large-scale cosmic-ray (CR) anisotropies in R.A., using data collected by the surface detector array of the Pierre Auger Observatory over more than 14 yr. We determine the equatorial dipole component, through a Fourier analysis in R.A. 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 subarray of detectors with 750 m separation, which allows us to extend the analysis down to ∼0.03 EeV. The most significant equatorial dipole amplitude obtained is that in the cumulative bin above 8 EeV, %, which is inconsistent with isotropy at the 6σ level. In the bins below 8 EeV, we obtain 99% CL upper bounds on d ⊥ at the level of 1%-3%. 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 R.A. of the Galactic center, at GC =-94°, suggesting a predominantly Galactic origin for anisotropies at these energies. The reconstructed dipole phases in the energy bins above 4 EeV point instead to R.A. that are almost opposite to the Galactic center one, indicative of an extragalactic CR origin.
2020
pierre auger observatory; cosmic rays; anisotropies
01 Pubblicazione su rivista::01a Articolo in rivista
Cosmic-Ray anisotropies in right ascension measured by the Pierre Auger Observatory / Aab, A., Abreu, P., Aglietta, M., Albuquerque, I.F.M., Albury, J.M., Allekotte, I., Almela, A., Castillo, J.A., Alvarez-Muiz, J., Anastasi, G.A., Anchordoqui, L., Andrada, B., Andringa, S., Aramo, C., Ferreira, P.R.A., Asorey, H., Assis, P., Avila, G., Badescu, A.M., Bakalova, A., et al.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 891:2(2020), pp. 1-10. [10.3847/1538-4357/ab7236]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1752266
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