Hyperaccreting Magnetised Neutron Stars inside Rotating Massive Envelopes: Low-Power Jets and Precursor Flares

@misc{cheong2026hyperaccreting,
  title = {{Hyperaccreting Magnetised Neutron Stars inside Rotating Massive Envelopes: Low-Power Jets and Precursor Flares}},
  author = {Patrick Chi-Kit Cheong and Christopher L. Fryer and David Radice},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2608.09395},
  eprint = {2608.09395},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2608.09395},
}

TY  - UNPB
TI  - Hyperaccreting Magnetised Neutron Stars inside Rotating Massive Envelopes: Low-Power Jets and Precursor Flares
AU  - Patrick Chi-Kit Cheong
AU  - Christopher L. Fryer
AU  - David Radice
PY  - 2026
DA  - 2026/10/13
PB  - arXiv
DO  - 10.48550/arxiv.2608.09395
UR  - https://arxiv.org/abs/2608.09395
AB  - The engulfment of a neutron star (NS) by a massive companion initiates a highly dynamic common-envelope (CE) evolution phase. As the NS spirals into the dense stellar core, it is subjected to hypercritical accretion rates that threaten to rapidly collapse the NS into a black hole (BH). However, if the infalling envelope possesses sufficient angular momentum and magnetic fields, the NS might survive longer and launch feedback-driving jets. To investigate this, we perform fully coupled, axisymmetric General Relativistic Magnetohydrodynamic (GRMHD) simulations of hyperaccreting NSs, featuring energy-integrated two-moment neutrino transport and a 13-isotope nuclear reaction network. We systematically vary the envelope rotation profile and the magnetic field strength of the NS surface (B_surf ∼ 5 × 10^10 − 5 × 10^13~G). In non-magnetised models, we find that envelope rotation naturally forms a centrifugal barrier and a geometrically thick accretion disk, which suppresses the mass accretion rate and lowers the neutrino luminosity; conversely, the intrinsic spin of the NS has a negligible global impact. In magnetised models, the differential rotation of the accretion flow vigorously amplifies the toroidal magnetic field via the Ω-effect, driving the expansion of magnetic towers. Crucially, for strong initial surface magnetic fields (B_surf ≳ 2.3 × 10^13~G), the intense magnetic pressure could completely halt the accretion flow at the NS surface and evacuates a low-density polar funnel. We conclude that while this highly magnetised NS engine successfully delays prompt BH formation and may launch low-power precursor jets (with powers up to ∼ 10^46 erg/s) capable of generating observable X-ray flares, it lacks the energy budget to unbind the massive envelope, potentially setting the stage for a subsequent BH-driven explosion.
ER  -