TY - JOUR
T1 - Combined fit of UHECR spectrum and composition with two extragalactic source populations
AU - Das, Saikat
AU - Razzaque, Soebur
AU - Gupta, Nayantara
N1 - Publisher Copyright:
© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0)
PY - 2022/3/18
Y1 - 2022/3/18
N2 - A mixed composition of light-to-heavy nuclei elements (1H, 4He, 14N, 28Si, 56Fe) at injection fits the ultrahigh-energy cosmic ray (UHECR; E > 1017 eV) spectrum data measured by the Pierre Auger Observatory, beyond the ankle, i.e., E & 5 × 1018 eV. However, the composition fit can be further improved by the addition of light nuclei at the highest energies. We consider the light nuclei to originate from a discrete source population consisting of protons (1H). We constrain the maximum allowed proton fraction at the highest-energy bin at 3.5σ statistical significance. Including the redshift evolution of sources as a free parameter further improves the composition fit. We find that low-luminosity gamma-ray bursts match the best-fit evolution index in the case of the one-population model. Active galactic nuclei are the plausible candidates for light nuclei injection in the two-population model, whereas tidal disruption events can inject heavy nuclei composition. We also present the secondary neutrino flux in one- and two-population models, constraining the composition at highest energies.
AB - A mixed composition of light-to-heavy nuclei elements (1H, 4He, 14N, 28Si, 56Fe) at injection fits the ultrahigh-energy cosmic ray (UHECR; E > 1017 eV) spectrum data measured by the Pierre Auger Observatory, beyond the ankle, i.e., E & 5 × 1018 eV. However, the composition fit can be further improved by the addition of light nuclei at the highest energies. We consider the light nuclei to originate from a discrete source population consisting of protons (1H). We constrain the maximum allowed proton fraction at the highest-energy bin at 3.5σ statistical significance. Including the redshift evolution of sources as a free parameter further improves the composition fit. We find that low-luminosity gamma-ray bursts match the best-fit evolution index in the case of the one-population model. Active galactic nuclei are the plausible candidates for light nuclei injection in the two-population model, whereas tidal disruption events can inject heavy nuclei composition. We also present the secondary neutrino flux in one- and two-population models, constraining the composition at highest energies.
UR - http://www.scopus.com/inward/record.url?scp=85143888916&partnerID=8YFLogxK
M3 - Conference article
AN - SCOPUS:85143888916
SN - 1824-8039
VL - 395
JO - Proceedings of Science
JF - Proceedings of Science
M1 - 460
T2 - 37th International Cosmic Ray Conference, ICRC 2021
Y2 - 12 July 2021 through 23 July 2021
ER -