Fast Cooling of Neutron Stars: Superfluidity versus Heating and Accreted Envelope

It is generally considered that the neutron star cooling scenarios involvingfast neutrino emission, from a kaon or pion condensate, quark matter, or thedirect Urca process, require the presence of baryon pairing in the central coreof the star to control the strong neutrino emission and produce surfacetemperatures compatible with observations. I show here that within the kaoncondensate scenario pairing is not necessary if: 1) the equation of state isstiff enough for the star to have a thick crust in which sufficient frictioncan occur to heat the star and 2) a thin layer, of mass larger than 10^{-12}Msol, of light elements (H and He) is present at the stellar surface. Theeffect of the light elements is to increase the heat flow and thus produce ahigher surface temperature. Both the occurrence of heating and the presence ofH and/or He at the surface (deposited during the late post-supernova accretion)can possibly be confirmed or infirmed by future observations.Comment: 7 pages AASLatex v4.0 + 2 ps figures. Submitted to Ap. J. Lett. ONLY change in this revised version is a misprint in a citatio