Strong neutrino cooling by cycles of electron capture and ${\beta }^{-}$ decay in neutron star crusts

Abstract

The temperature in the crust of an accreting neutron star, which comprises its outermost kilometer, is set by heating from nuclear reactions at large densities, neutrino cooling, and heat transport from the interior. The heated crust has been thought to affect observable phenomena at shallower depths, such as thermonuclear bursts in the accreted envelope. Here we report that cycles of electron capture and its inverse, ${\beta }^{-}$ decay, involving neutron-rich nuclei at a typical depth of about 150 m, cool the outer neutron star crust by emitting neutrinos while also thermally decoupling the surface layers from the deeper crust. This Urca mechanism has been studied in the context of white dwarfs and Type Ia supernovae, but hitherto was not considered in neutron stars, because previous models computed the crust reactions using a zero-temperature approximation and assumed that only a single nuclear species was present at any given depth. This thermal decoupling means that X-ray bursts and other surface phenomena are largely independent of the strength of deep crustal heating. The unexpectedly short recurrence times, of the order of years, observed for very energetic thermonuclear superbursts are therefore not an indicator of a hot crust, but may point instead to an unknown local heating mechanism near the neutron star surface.

arXiv comment15 pages with 5 figures. Nature advance online publication, December 1, 2013

References in corpus (26)

• Nuclear Ground-State Masses and Deformations
• Neutron Star Observations: Prognosis for Equation of State Constraints
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Neutrino Emission from Neutron Stars
• Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. XII: Stiffness and stability of neutron-star matter
• The endpoint of the rp process on accreting neutron stars
• Models for Type I X-Ray Bursts with Improved Nuclear Physics
• A Remarkable Three Hour Thermonuclear Burst From 4U 1820-30
• Carbon Flashes in the Heavy Element Ocean on Accreting Neutron Stars
• Mapping crustal heating with the cooling lightcurves of quasi-persistent transients
• Heating in the Accreted Neutron Star Ocean: Implications for Superburst Ignition
• Advanced burning stages and fate of 8-10 Mo stars
• Models of crustal heating in accreting neutron stars
• Long Type I X-ray Bursts and Neutron Star Interior Physics
• GT strengths and electron-capture rates for pf-shell nuclei of relevance for late stellar evolution
• Nuclear heating and melted layers in the inner crust of an accreting neutron star
• Possible Resonances in the 12C + 12C Fusion Rate and Superburst Ignition
• Forecasting neutron star temperatures: predictability and variability
• Superburst Models for Neutron Stars with Hydrogen and Helium-Rich Atmospheres
• Superburst Ignition and Implications for Neutron Star Interiors
• Multi-Zone Models of Superbursts from Accreting Neutron Stars
• Nuclear shell effects near the r-process path
• Superfluid Response and the Neutrino Emissivity of Neutron Matter
• Compositionally-driven convection in the oceans of accreting neutron stars
• The structure of accreted neutron star crust
• On burning regimes and long duration X-ray bursts

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