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Cosmic-ray Acceleration in Core-Collapse Supernova Remnants with the Wind Termination Shock

We investigate the attainable maximum energy of particles accelerated in the core-collapse supernova remnant (SNR) shock propagating in the free wind region with the Parker-spiral magnetic field, current sheet, and the wind termination shock (WTS) by using test particle simulations. This work focuses on Wolf-Rayet stars as progenitors. The magnetic field amplification in the free wind region (shock upstream region) is not considered in this work. Test particle simulations show that particles escaped from the core-collapse SNR reach and move along the WTS, and eventually return to the SNR shock from the poles or equator of the WTS. The particle attainable energy can be boosted by this cyclic motion between the SNR shock and WTS and can be larger than the particle energy that is limited by escape from the SNR shock. The particle energy limited by the cyclic motion between the SNR shock and WTS is about $10-100~{\rm TeV}$. Thus, the core-collapse SNR without upstream magnetic field amplification can be the origin of the break around $10~{\rm TeV}$ of the energy spectrum of observed cosmic ray protons and helium.