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Origin of Ultra-High Energy Cosmic Rays: Nuclear Composition of Gamma-Ray Burst Jets

Published online by Cambridge University Press:  05 September 2012

Sanshiro Shibata  and
Nozomu Tominaga
Sanshiro Shibata
Affiliation:
Department of physics, Konan University, 8-9-1 Okamoto, Kobe, Hyogo 658-8501, Japan Email: [email protected]
Nozomu Tominaga
Affiliation:
Department of physics, Konan University, 8-9-1 Okamoto, Kobe, Hyogo 658-8501, Japan Email: [email protected] Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan
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Abstract

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Ultra-high energy cosmic rays (UHECRs) are the most energetic particles flying from space and their source is not clarified yet. Recently, the Pierre Auger Observatory (PAO) suggests that UHECRs involve heavy nuclei. The PAO results require that a considerable fraction of metal nuclei must exist in the accelerating site, which can be realized only in the stellar interior. This puts strong constraints on the origin of UHECRs. In order to definitize the constraints from PAO results, we investigate the fraction of metal nuclei in a relativistic jet in gamma-ray burst associated with core-collapse supernova. If the jet is initially dominated by radiation field, quasi-statistical equilibrium (QSE) is established and heavy nuclei are dissociated to light particles such as 4He during the acceleration and expansion. On the other hand, if the jet is mainly accelerated by magnetic field heavy or intermediate mass nuclei can survive. The criterion to contain the metal nuclei is that the temperature at the launch site is below 4.5 × 109K. Therefore, if the composition of UHECRs is dominated by metal nuclei, a GRB with the magnetized jet is the most plausible candidate of the accelerating site.

Keywords

gamma rays: burstsnuclear reactionsnucleosynthesisabundancesMHD
Type
Poster Papers
Information
Proceedings of the International Astronomical Union , Volume 7 , Symposium S279: Death of Massive Stars: Supernovae and Gamma-Ray Bursts , April 2011 , pp. 389 - 390
Copyright
Copyright © International Astronomical Union 2012

References

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