Extreme eccentricity in double neutron stars without exotic physics
Abstract
The formation of neutron stars (NSs) underpins astrophysical phenomena from supernovae (SNe), radio pulsars and X-ray binaries to double NS mergers that power gravitational waves (GWs), short gamma-ray bursts and r-process kilonovae. A recently reported double NS (PSR J0653+0443) with record eccentricity e=0.9924 provides a unique laboratory for studying GW emission and orbital evolution, and challenges existing formation scenarios. Here we show that such extreme eccentricities arise naturally -- without invoking exotic conditions -- from standard binary-SN physics: instantaneous mass loss (Blaauw recoil) and natal kicks readily produce e>0.99 for both compact and wide pre-SN orbits. The observed orbit matches three families of kinematic solutions spanning a range of kick velocities and progenitor configurations. Physically motivated priors based on NS spin and pre-SN mass transfer constrain the viable progenitor family, demonstrating that the system is not exceptionally rare. Future proper-motion measurements will tightly constrain its natal SN kick magnitude.
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BibTeX
@misc{tauris2026extreme,
title = {{Extreme eccentricity in double neutron stars without exotic physics}},
author = {Thomas M. Tauris},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.37759},
eprint = {2610.37759},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.37759},
}
RIS
TY - UNPB
TI - Extreme eccentricity in double neutron stars without exotic physics
AU - Thomas M. Tauris
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.37759
UR - https://arxiv.org/abs/2610.37759
AB - The formation of neutron stars (NSs) underpins astrophysical phenomena from supernovae (SNe), radio pulsars and X-ray binaries to double NS mergers that power gravitational waves (GWs), short gamma-ray bursts and r-process kilonovae. A recently reported double NS (PSR J0653+0443) with record eccentricity e=0.9924 provides a unique laboratory for studying GW emission and orbital evolution, and challenges existing formation scenarios. Here we show that such extreme eccentricities arise naturally -- without invoking exotic conditions -- from standard binary-SN physics: instantaneous mass loss (Blaauw recoil) and natal kicks readily produce e>0.99 for both compact and wide pre-SN orbits. The observed orbit matches three families of kinematic solutions spanning a range of kick velocities and progenitor configurations. Physically motivated priors based on NS spin and pre-SN mass transfer constrain the viable progenitor family, demonstrating that the system is not exceptionally rare. Future proper-motion measurements will tightly constrain its natal SN kick magnitude.
ER -