The long-held notion that the highest energy cosmic rays are of distant extragalactic origin is challenged by observations that events above approximately 1020 eV do not exhibit the expected high-energy cutoff from photopion production off the cosmic microwave background. We suggest that these unexpected ultra-high-energy events are due to iron nuclei accelerated from young strongly magnetized neutron stars through relativistic MHD winds. We find that neutron stars whose initial spin periods are shorter than approximately 10 ms and whose surface magnetic fields are in the 1012-1014 G range can accelerate iron cosmic rays to greater than approximately 1020 eV. These ions can pass through the remnant of the supernova explosion that produced the neutron star without suffering significant spallation reactions or energy loss. For plausible models of the Galactic magnetic field, the trajectories of the iron ions curve sufficiently to be consistent with the observed, largely isotropic arrival directions of the highest energy events.

Cosmic ray spallation

10.1086/312626

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Citations (162)

The fate of ultrahigh energy nuclei in the immediate environment of young fast-rotating pulsars

Journal of Cosmology and Astroparticle Physics (2015)

Kumiko Kotera Elena Amato Pasquale Blasi

Young, fast-rotating neutron stars are promising candidate sources for the production of ultrahigh energy cosmic rays (UHECRs). The interest in this model has recently been boosted by the latest chemical composition measurements of cosmic rays, that seem to show the presence of a heavy nuclear component at the highest energies. Neutrons stars, with their metal-rich surfaces, are potentially interesting sources of such nuclei, but some open issues remain: 1) is it possible to extract these nuclei from the star's surface? 2) Do the nuclei survive the severe conditions present in the magnetosphere of the neutron star? 3) What happens to the surviving nuclei once they enter the wind that is launched outside the light cylinder? In this paper we address these issues in a quantitative way, proving that for the most reasonable range of neutron star surface temperatures (T<107 K), a large fraction of heavy nuclei survive photo-disintegration losses. These processes, together with curvature losses and acceleration in the star's electric potential, lead to injection of nuclei with a chemical composition that is mixed, even if only iron is extracted from the surface. We show that under certain conditions the chemical composition injected into the wind region is compatible with that required in previous work based on purely phenomenological arguments (typically ∼50% protons, ∼30% CNO and ∼20% Fe), and provides a reasonable explanation of the mass abundance inferred from ultra high energy data.

r-process

10.1088/1475-7516/2015/08/026

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Citations (58)

Multiwavelength observations of clusters of galaxies and the role of cluster mergers

Pasquale Blasi

Some clusters of galaxies have been identified as powerful sources of non-thermal radiation, from the radio to X-ray wavelengths. The classical models proposed for the explanation of this radiation usually require large energy densities in cosmic rays in the intracluster medium and magnetic fields much lower than those measured using the Faraday rotation. They study here the role that mergers of clusters of galaxies may play in the generation of the non-thermal radiation, and they seek for additional observable consequences of the model. They find that if hard X-rays and radio radiation are respectively interpreted as inverse Compton scattering (ICS) and synchrotron emission of relativistic electrons, large gamma ray fluxes are produced, and for the Coma cluster, where upper limits are available, these limits are exceeded. They also discuss an alternative and testable model that naturally solves the problems mentioned above.

Coma Cluster

Intracluster medium

Source

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SNI: new mechanism for gamma ray burst. I: Weak magnetic field

STIN (1995)

V. S. Berezinsky Pasquale Blasi B. Hnatyk

Source

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GeV GAMMA-RAY FLUX UPPER LIMITS FROM CLUSTERS OF GALAXIES

The Astrophysical Journal Letters (2010)

M. Ackermann M. Ajello A. Allafort L. Baldini J. Ballet

The detection of diffuse radio emission associated with clusters of galaxies indicates populations of relativistic leptons infusing the intracluster medium (ICM). Those electrons and positrons are either injected into and accelerated directly in the ICM, or produced as secondary pairs by cosmic-ray ions scattering on ambient protons. Radiation mechanisms involving the energetic leptons together with the decay of neutral pions produced by hadronic interactions have the potential to produce abundant GeV photons. Here, we report on the search for GeV emission from clusters of galaxies using data collected by the Large Area Telescope on the Fermi Gamma-ray Space Telescope from 2008 August to 2010 February. Thirty-three galaxy clusters have been selected according to their proximity and high mass, X-ray flux and temperature, and indications of non-thermal activity for this study. We report upper limits on the photon flux in the range 0.2–100 GeV toward a sample of observed clusters (typical values (1–5) ×10−9 photon cm−2 s−1) considering both point-like and spatially resolved models for the high-energy emission and discuss how these results constrain the characteristics of energetic leptons and hadrons, and magnetic fields in the ICM. The volume-averaged relativistic-hadron-to-thermal energy density ratio is found to be <5%–10% in several clusters.

Intracluster medium

10.1088/2041-8205/717/1/l71

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Citations (132)

An application of INAA and PIXE on the analysis of nutritional and toxicological elements in samples of drinkable water

Biological Trace Element Research (1990)

Pasquale Blasi G. Capannesi A. Cecchi F. Lucarelli F. A. Sedda

Neutron Activation Analysis

10.1007/bf02992691

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Citations (11)

Ultrahigh energy cosmic rays from dark matter annihilation

Nuclear Physics B - Proceedings Supplements (2003)

Rainer Dick Pasquale Blasi Edward W. Kolb

Annihilation

PAMELA detector

Warm dark matter

Signature (topology)

10.1016/s0920-5632(03)02106-6

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Extragalactic cosmic ray self-confinement around sources

arXiv (Cornell University) (2015)

Pasquale Blasi Elena Amato M. D’Angelo

Most models of the origin of ultra high energy cosmic rays rely on the existence of luminous extragalactic sources. Cosmic rays escaping the galaxy where the source is located produce a sufficiently large electric current to justify the investigation of plasma instabilities induced by such current. Most interesting is the excitation of modes that lead to production of magnetic perturbations that may scatter particles thereby hindering their escape, or at least changing the propagation mode of escaping cosmic rays. We argue that self-generation of waves may force cosmic rays to be confined in the source proximity for energies $E\lesssim 10^{7} L_{44}^{2/3}$ GeV for low background magnetic fields ($B_{0}\ll nG$). For larger values of $B_{0}$, cosmic rays are confined close to their sources for energies $E\lesssim 2\times 10^{8} λ_{10} L_{44}^{1/4} B_{-10}^{1/2}$ GeV, where $B_{-10}$ is the field in units of $0.1$ nG, $λ_{10}$ is its coherence length in units of 10 Mpc and $L_{44}$ is the source luminosity in units of $10^{44}$ erg/s.

10.48550/arxiv.1508.04698

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Citations (1)

CTA Contributions to the 34th International Cosmic Ray Conference (ICRC2015)

arXiv (Cornell University) (2015)

the CTA Consortium NULL AUTHOR_ID A. Abchiche A. U. Abeysekara Ó. Abril

List of contributions from the CTA Consortium presented at the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands.

10.48550/arxiv.1508.05894

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Citations (3)