Authors
Z L Yang, J L Han, W Q Su, P F Wang, C Wang, T Wang, D J Zhou, Yi Yan, J Xu, W C Jing, N N Cai, R X Xu, H G Wang, X P You
Published in
Physical review letters. Volume 137. Issue 12. Pages 121401. Sep 18, 2026.
Abstract
Compact double neutron star (DNS) systems are unique laboratories for testing gravitational theories and studying DNS mergers. Here we report the properties of a new DNS system, PSR J1856-0039, discovered in the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The pulsar is mildly recycled with a period of 23.4 ms in a compact eccentric orbit (e=0.106) with an orbital period of 2.36 hours. By following up FAST observations, we measured the relativistic effects, including the orbital period derivative P[over ˙]_{orb}=-1.284±0.019×10^{-12} s s^{-1}, periastron advance ω[over ˙]=17.5859±0.0007 deg yr^{-1}, and Einstein delay γ=0.445±0.011 ms. This DNS system has a low orbital inclination of i=133.[over ∘]2±1.[over ∘]1 and the lowest total mass of any known DNS, M_{tot}=2.48841±0.00015M_{⊙}, with a determined pulsar mass of 1.304±0.022M_{⊙} and a companion mass of 1.185±0.022M_{⊙}, one of the lowest neutron-star masses. The observed orbital decay due to gravitational-wave emission P[over ˙]_{orb,obs}^{GW} and the orbital decay predicted by general relativity P[over ˙]_{orb,pred}^{GW} are consistent at a level of P[over ˙]_{orb,obs}^{GW}/P[over ˙]_{orb,pred}^{GW}=1.009(14) (68% confidence). This DNS will merge after 82 Myr and may form a stable neutron star or collapse into a black hole after spin-down. Long-term monitoring could potentially probe the Lense-Thirring precession.
PMID:
42826977
Bibliographic data and abstract were imported from PubMed on 03 Oct 2026.
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