Accreting neutron stars: heating of the upper layers of the inner crust

Abstract

Neutron stars in low-mass X-ray binaries are thought to be heated up by accretion-induced exothermic nuclear reactions in the crust. The energy release and the location of the heating sources are important ingredients of the thermal evolution models. Here we present thermodynamically consistent calculations of the energy release in three zones of the stellar crust: at the outer-inner crust interface, in the upper layers of the inner crust (up to the density $\rho \le 2\times 10^{12}$ g cm${}^{-3}$), and in the underlying crustal layers. We consider three representative models of thermonuclear ashes (Superburst, Extreme rp, and Kepler ashes). The energy release in each zone is parametrized by the pressure at the outer-inner crust interface, which encodes all uncertainties related to the physics of the deepest inner-crust layers. Our calculations allow us, in particular, to set new lower limits on the net energy release (per accreted baryon): $Q\gtrsim 0.28$ MeV for Extreme rp ashes and Q~0.43-0.51 MeV for Superburst and Kepler ashes.

5 pages, 1 figure; submitted to MNRAS:Letters

References in corpus (19)

• Models of crustal heating in accreting neutron stars
• Dependence of X-Ray Burst Models on Nuclear Reaction Rates
• Fusion reactions in multicomponent dense matter
• Cooling of Accretion-Heated Neutron Stars
• Thermal states of coldest and hottest neutron stars in soft X-ray transients
• Neutron drip transition in accreting and nonaccreting neutron star crusts
• Statistical theory of thermal evolution of neutron stars - II. Limitations on direct Urca threshold
• Neutron reactions in accreting neutron stars: a new pathway to efficient crust heating
• Thermal evolution of relativistic hyperonic compact stars with calibrated equations of state
• Crust structure and thermal evolution of neutron stars in soft X-ray transients
• Thermodynamically consistent equation of state for an accreted neutron star crust
• Observational appearance of rapidly rotating neutron stars: X-ray bursts, cooling tail method, and radius determination
• Heat release in accreting neutron stars
• Deep crustal heating for realistic compositions of thermonuclear ashes
• Measuring Masses and Radii of Neutron Stars in Low-Mass X-ray Binaries: Effects of Atmospheric Composition and Touchdown Radius
• Constraining the properties of dense neutron star cores: The case of the low-mass X-ray binary HETE J1900.1-2455
• Crucial role of neutron diffusion in the crust of accreting neutron stars
• Quiescent luminosities of accreting neutron stars with different equation of states
• Nonequilibrium thermodynamics of accreted neutron-star crust

Cited by in corpus (2)

• Impacts of the direct URCA and Superfluidity inside a Neutron Star on Type-I X-Ray Bursts and X-Ray Superbursts
• Constraining Accreted Neutron Star Crust Shallow Heating with the Inferred Depth of Carbon Ignition in X-ray Superbursts