205 research outputs found
From the Galaxy to the Edge of the Universe: Plausible Sources of UHECRs
The lack of a high energy cutoff in the cosmic ray spectrum together with an
apparently isotropic distribution of arrival directions for the highest energy
events have strongly constrained most models proposed for the generation of
these particles. An overview of the theoretical proposals are presented along
with their most general signatures. Future experimental tests of the different
proposals are discussed.Comment: 14 pages, 7 figures; talk given at the International Workshop on
Observing Ultra High Energy Cosmic Rays From Space and Earth, Metepec,
Puebla, Mexico (2000
Chasing Cosmic Bullets: The Pierre Auger Experiment
The most energetic particles in the universe are ultra-high energy cosmic rays. Millions of times more powerful than anything produced by man-made accelerators, their origin has been a mystery for about a century. Over the last several years, an international collaboration of 18 countries joined forces to solve this mystery by building the Pierre Auger Observatory. Spread over 3,000 square kilometers in western Argentina, the observatory was recently inaugurated. During its construction, the observatory gathered enough of these rare particles to find the first clues to their origin. The most energetic of these particles tend to point to cosmologically nearby galaxies that host super massive black holes at their centers. Over the next years, scientists working on Auger will be carefully studying these most extreme particles, learning where they come from and what they are made of in order to solve the longstanding mystery of where they come from and how they are accelerated to the highest energies ever observed
Ultrahigh Energy Cosmic Ray Nuclei from Extragalactic Pulsars and the effect of their Galactic counterparts
The acceleration of ultrahigh energy nuclei in fast spinning newborn pulsars
can explain the observed spectrum of ultrahigh energy cosmic rays and the trend
towards heavier nuclei for energies above eV as reported by the
Auger Observatory. Pulsar acceleration implies a hard injection spectrum () due to pulsar spin down and a maximum energy eV due to the limit on the spin rate of neutron stars. We have
previously shown that the escape through the young supernova remnant softens
the spectrum, decreases slightly the maximum energy, and generates secondary
nuclei. Here we show that the distribution of pulsar birth periods and the
effect of propagation in the interstellar and intergalactic media modifies the
combined spectrum of all pulsars. By assuming a normal distribution of pulsar
birth periods centered at 300 ms, we show that the contribution of
extragalactic pulsar births to the ultrahigh energy cosmic ray spectrum
naturally gives rise to a contribution to very high energy cosmic rays (VHECRs,
between and eV) by Galactic pulsar births. The required
injected composition to fit the observed spectrum depends on the absolute
energy scale, which is uncertain, differing between Auger Observatory and
Telescope Array. The contribution of Galactic pulsar births can also bridge the
gap between predictions for cosmic ray acceleration in supernova remnants and
the observed spectrum just below the ankle, depending on the composition of the
cosmic rays that escape the supernova remnant and the diffusion behavior of
VHECRs in the Galaxy.Comment: 21 pages, 5 figure, JCAP submitte
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