Speaker
Dr
Kumiko Kotera
(University of Chicago)
Description
Newly-born magnetars are good candidates for the acceleration of ultrahigh energy
cosmic rays (Blasi et al. 00, Arons 03). We discuss issues related to the production
of ultrahigh energy heavy nuclei in newly-born magnetars, in light of the latest
results of the Auger Observatory.
Magnetars offer favorable sites for the injection of heavy nuclei (by stripping from
the star surface or by r-process in the wind), and for their further acceleration to
the highest energies by unipolar induction. Once accelerated in the wind, nuclei have
to escape from the dense supernova envelope surrounding the magnetar. We examine this
escape analytically and numerically.
We find that iron nuclei can escape from the envelope for a certain range of magnetar
parameters, while protons and light elements never can. Iron escape leads to a
transition from light to heavy nuclei from low to high energy as observed in the
Auger data (Abraham et al. 2010), due to the production of secondary nucleons. Heavy
nuclei escape from the envelope also results in a much softer spectral slope than the
original injected power-law in -1, and, after propagation in the intergalactic
medium, allows a good fit the observed ultrahigh energy cosmic ray spectrum.
In conclusion, we find that the injection of iron nuclei in magnetars within a
certain range of parameters gives a picture that is surprisingly consistent with the
UHECR overall data measured with Auger.
Primary author
Dr
Kumiko Kotera
(University of Chicago)
Co-authors
Prof.
Angela Olinto
(University of Chicago)
Ke Fang
(University of Chicago)
