A concordance model of neutron star kicks
Abstract
Neutron stars (NSs) receive natal kicks during supernovae that affect their survival in binaries and motion through the Galaxy. The global distribution of these kick velocities across the NS population remains uncertain. Here, we combine the orbital properties and birth rates of Gaia NS and Be+NS binaries with velocity constraints from young isolated pulsars to construct a concordance model of NS natal kicks. We find that all three populations can be jointly described by a shared bimodal kick distribution. The low-velocity component follows a lognormal distribution with μln v=1.87+0.65−0.53 and σln v=0.55+0.85−0.44, corresponding to a median speed of 6.5+5.9−2.7 km s−1. The high-velocity component is consistent with the distribution inferred from young pulsars, which peaks near 200 km s−1. The low-velocity component contributes only ∼10% of all NS births, but produces most Gaia NS binaries and roughly half of Be+NS binaries. The same model predicts systemic recoil velocities consistent with the observed kinematics of Gaia NSs, Be+NS binaries, and NS low-mass X-ray binaries. For Gaia NSs, whose formation history remains unknown, we use this kick distribution to constrain their progenitors. We favor pre-supernova binaries containing intermediate-mass stripped stars with ∼1 M⊙ companions in au-scale orbits, and predict ∼300 such binaries in the Milky Way today, ∼40 in the LMC, and ∼30 in the SMC. Finally, we consider the implications of these kicks for NSs in hierarchical triples. We find that 2-10% of Gaia NS triples and 3-23% of Be+NS triples retain their tertiary after the supernova. Overall, our results suggest that a shared natal kick law can account for isolated pulsars and surviving NS binaries, where most NSs receive large kicks and low kicks are common among surviving binaries.
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BibTeX
@misc{shariat2026concordance,
title = {{A concordance model of neutron star kicks}},
author = {Cheyanne Shariat and Kareem El-Badry and Smadar Naoz},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.04005},
eprint = {2610.04005},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.04005},
}
RIS
TY - UNPB
TI - A concordance model of neutron star kicks
AU - Cheyanne Shariat
AU - Kareem El-Badry
AU - Smadar Naoz
PY - 2026
DA - 2026/10/02
PB - arXiv
DO - 10.48550/arxiv.2610.04005
UR - https://arxiv.org/abs/2610.04005
AB - Neutron stars (NSs) receive natal kicks during supernovae that affect their survival in binaries and motion through the Galaxy. The global distribution of these kick velocities across the NS population remains uncertain. Here, we combine the orbital properties and birth rates of Gaia NS and Be+NS binaries with velocity constraints from young isolated pulsars to construct a concordance model of NS natal kicks. We find that all three populations can be jointly described by a shared bimodal kick distribution. The low-velocity component follows a lognormal distribution with μ_ln v=1.87^+0.65_−0.53 and σ_ln v=0.55^+0.85_−0.44, corresponding to a median speed of 6.5^+5.9_−2.7 km s^−1. The high-velocity component is consistent with the distribution inferred from young pulsars, which peaks near 200 km s^−1. The low-velocity component contributes only ∼10% of all NS births, but produces most Gaia NS binaries and roughly half of Be+NS binaries. The same model predicts systemic recoil velocities consistent with the observed kinematics of Gaia NSs, Be+NS binaries, and NS low-mass X-ray binaries. For Gaia NSs, whose formation history remains unknown, we use this kick distribution to constrain their progenitors. We favor pre-supernova binaries containing intermediate-mass stripped stars with ∼1 M_⊙ companions in au-scale orbits, and predict ∼300 such binaries in the Milky Way today, ∼40 in the LMC, and ∼30 in the SMC. Finally, we consider the implications of these kicks for NSs in hierarchical triples. We find that 2-10% of Gaia NS triples and 3-23% of Be+NS triples retain their tertiary after the supernova. Overall, our results suggest that a shared natal kick law can account for isolated pulsars and surviving NS binaries, where most NSs receive large kicks and low kicks are common among surviving binaries.
ER -