Ultra high-energy cosmic rays from relativistic outflows in accretion induced collapse of white dwarfs

TL;DR

This paper proposes that relativistic outflows from accretion-induced collapse of white dwarfs could be significant sources of ultra high-energy cosmic rays, modeling heavy nuclei acceleration and estimating their contribution.

Contribution

It introduces a new model linking white dwarf collapse events to the acceleration of heavy nuclei as UHECR sources, with quantitative estimates of their energy contribution.

Findings

AICs can produce relativistic outflows capable of accelerating heavy nuclei to ultra high energies.

AICs could account for a few 10^{43} - 10^{45} erg Mpc^{-3} yr^{-1} in UHECR energy density.

Relativistic outflows from AICs may dominate the observed UHECR flux if most host such outflows.

Abstract

When a rapidly-rotating, highly magnetized white dwarf (WD) approaches the Chandrashekhar limit through mass accretion, it can undergo an accretion-induced collapse (AIC) to form a proto-neutron star or protomagnetar. The protomagnetar can drive a magnetically-dominated relativistic outflow, whose low entropy can lead to efficient formation of heavy nuclei. In this work, we propose that such relativistic outflows from AIC of WDs can contribute as sources of ultra high-energy cosmic rays (UHECRs). We model the acceleration of heavy nuclei in these relativistic outflows, and show that AICs can dominantly power the observed UHECRs, if a majority of them host relativistic outflows. Accounting for uncertainties in the acceleration mechanisms and AIC rates, AICs can contribute $\sim$ a few $10^{43} - 10^{45}\ {\rm erg \ Mpc}^{-3} {\rm yr}^{-1}$ in UHECR energy generation rate density, assuming iron-like nuclei.