Supernovae in compact star clusters as sources of high-energy cosmic rays and neutrinos

We discuss a specific population of galactic PeVatrons which may be the main source of the galactic cosmic-ray (CR) component well above PeV energies. Supernovae in compact clusters of massive stars are proposed as powerful sources of CRs, neutrinos, and gamma-ray emission. Numerical simulations of non-linear Fermi acceleration at converging shock flows have revealed that these accelerators can provide very hard spectra of protons up to $10^{16}-10^{17}$ eV which is well above the "knee" in the all-particle CR spectrum at about $3\times10^{15}$ eV. We suggest that known supernova remnants interacting with stellar winds in the compact clusters of young massive stars Westerlund I and Cl*1806-20 can be associated with the sources of the TeV gamma-ray emission detected by H.E.S.S. and may be responsible for a fraction of the high-energy neutrinos detected with the IceCube observatory. A recent CR composition measurement with the LOFAR array has revealed a light-mass component possibly dominating the all-particle spectrum at energies around $10^{17}$ eV. Such a strong light component (mainly protons and helium) may require specific galactic CR sources such as supernovae interacting with compact clusters of massive stars in addition to isolated supernova remnants.
Comment: Accepted for publication in Advances in Space Research May 2017