Internal temperatures and cooling of neutron stars with accreted envelopes

Therelationshipsbetweentheeffectivesurface(Teff) and internal temperatures of neutron stars (NSs) with and with- out accreted envelopes are calculated for Teff > 5 10 4 K using new data on the equation of state and opacities in the outer NS layers. We examine various models of accreted lay- ers (H, He, C, O shells produced by nuclear transformations in accreted matter). We employ new Opacity Library (OPAL) radiative opacities for H, He, and Fe. In the outermost NS lay- ers, we implement the modern OPAL equation of state for Fe, and the Saumon-Chabrier equation of state for H and He. The updated thermal conductivities of degenerate electrons include the Debye-Waller factor for the electron-phonon scattering in solidied matter, while in liquid matter they include the contri- butions from electron-ion collisions (evaluated with non-Born correctionsandwiththeionstructurefactorsinresponsiveelec- tron background) and from the electron-electron collisions. For Teff 10 5 K. Even a small amount of accreted mat- ter(withmass> 10 16 M)affectsappreciablytheNScooling, leading to higher Teff at the neutrino cooling stage and to lower Teff at the subsequent photon stage.