Energy accreted onto a compact star
Abstract
We compute the energy gained by accretion onto a compact star due to matter falling from the inner edge of a thin accretion disk. We employ a controlled slow-rotation expansion based on the Hartle-Thorne metric and find that in neutron stars in general only leading order rotational corrections to the metric, describing frame dragging, are sizable. However, for accretion onto a magnetized neutron star, where the disk roughly extends to the co-rotation radius, even frame dragging effects are minor. Based on general conservation laws we then derive simple, equation-of-state-independent expressions for the spin-up and heating energy, consistently including the relevant rotational, relativistic and nuclear effects, and find that in observed accreting millisecond sources the results can strongly deviate from presently employed estimates.
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BibTeX
@misc{arf2026energy,
title = {{Energy accreted onto a compact star}},
author = {Kaiser Arf and Kai Schwenzer},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.11902},
eprint = {2609.11902},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.11902},
}
RIS
TY - UNPB
TI - Energy accreted onto a compact star
AU - Kaiser Arf
AU - Kai Schwenzer
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.11902
UR - https://arxiv.org/abs/2609.11902
AB - We compute the energy gained by accretion onto a compact star due to matter falling from the inner edge of a thin accretion disk. We employ a controlled slow-rotation expansion based on the Hartle-Thorne metric and find that in neutron stars in general only leading order rotational corrections to the metric, describing frame dragging, are sizable. However, for accretion onto a magnetized neutron star, where the disk roughly extends to the co-rotation radius, even frame dragging effects are minor. Based on general conservation laws we then derive simple, equation-of-state-independent expressions for the spin-up and heating energy, consistently including the relevant rotational, relativistic and nuclear effects, and find that in observed accreting millisecond sources the results can strongly deviate from presently employed estimates.
ER -