Ultra-high-energy cosmic rays strike white dwarfs and neutron stars at astrophysically significant rates.

The claim originates in the astrophysical safety literature around TeV-scale black holes, principally Giddings and Mangano, "Astrophysical implications of hypothetical stable TeV-scale black holes" (arXiv:0806.3381). Their calculation takes the measured ultra-high-energy cosmic ray spectrum, which is uncontested (the subclaim that cosmic rays above 10^18 eV are observed is settled measurement from Auger and predecessors), and integrates it over stellar cross-sections and gigayear ages. For white dwarfs this yields production-rate tables showing vast numbers of super-collider-energy collisions over a white dwarf's lifetime; neutron-star rates follow by surface-area rescaling, which the authors explicitly present "neglecting the magnetic screening."

The supporting argument therefore goes through cleanly for white dwarfs, conditional on the subclaim that some white dwarfs have fields weak enough for cosmic rays to reach their surfaces; this is observationally well grounded (magnetic surveys find large populations of white dwarfs with fields at or below the kilogauss scale) and Giddings and Mangano identify specific low-field candidates.

The counter-consideration is the subclaim that strong magnetic fields shield most neutron stars from charged ultra-high-energy cosmic rays. This is taken seriously across the literature: contemporary commentary on the safety debate records that neutron-star bounds were "helpful but not definitive" precisely because of screening, and Sokolov and Pshirkov (Eur. Phys. J. C, 2017; arXiv:1611.04949) compute a cutoff near 1.8x10^17 eV above which cosmic rays cannot reach a typical neutron-star surface. This qualifies, rather than negates, the claim: neutron stars still intercept cosmic rays at lower energies and via binary-companion channels, and the white-dwarf half is unaffected.

Weighing: the load-bearing content (white dwarfs, and compact stars in aggregate, accumulate astrophysically significant ultra-high-energy strikes) is solid; the conjunct covering typical neutron stars at the very highest energies is contradicted by the screening analyses. Supported, not verified, because the claim as worded bundles the qualified neutron-star case with the robust white-dwarf case, and because the rate tables were checked through the literature rather than recomputed. Evidence that would change the verdict: a demonstration that white-dwarf magnetic fields or envelopes screen ultra-high-energy cosmic rays after all (would push toward contested), or a resolution of the neutron-star screening question showing substantial flux does reach representative neutron-star surfaces (would push toward verified).