Session T7: Cosmic Ray Composition and Air Shower Studies

3:30 PM–5:18 PM, Monday, April 2, 2012
Room: Embassy D

Sponsoring Unit: DAP
Chair: Robert Binns, Washington University in St. Louis

Abstract ID: BAPS.2012.APR.T7.9

Abstract: T7.00009 : Newly-born Pulsars as Sources of Ultrahigh Energy Cosmic Rays

5:06 PM–5:18 PM

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Authors:

  Ke Fang
    (Department of Astronomy and Astrophysics, Kavli Institute for Cosmological Physics, The University of Chicago)

  Kumiko Kotera
    (Theoretical Astrophysics, California Institute of Technology)

  Angela Olinto
    (Department of Astronomy and Astrophysics, Kavli Institute for Cosmological Physics, The University of Chicago)

Newly-born pulsars are good candidate sources of ultrahigh energy cosmic ray (UHECR). Young pulsars can strip heavy nuclei from the star surface, and further accelerate them to ultrahigh energies by unipolar induction in the pulsar wind. Once accelerated, nuclei have to escape from the dense supernova envelope surrounding the pulsar. We examine this escape analytically and numerically. Our results show that, protons with energy above $10^{20}\,$eV can hardly survive from interactions with the young supernova shell. In contrast, as a result of their higher charge, iron-peaked nuclei at the highest observed energies are able to escape newly-born pulsars with millisecond periods and dipole magnetic fields of $\sim10^{12-13}\,$Gauss, embedded in core-collapse supernova. The escaped spectrum presents a transition of composition from light to heavy elements at a few EeV as observed by the Auger Observatory, due to the production of secondary nucleons. The interactions also help to soften the spectral slope, which allows a good fit to the observation. We conclude that the acceleration of heavy nuclei in a reasonably small fraction ($\le 0.01\%$) of extragalactic young pulsars would reproduce consistently the current UHECR data.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.APR.T7.9