Direct Urca neutrino radiation from superfluid baryonic matter

Dense matter in compact stars cools efficiently by neutrino emission via the direct Urca processes n --> p + e + (v) over bare and p + e --> n + (v) over bare. Below the pairing phase transition temperature T-c these processes are suppressed-at asymptotically low temperatures exponentially. We compute the emissivity of the Urca process at one loop for temperatures T less than or equal to T-c, in the case where the baryons are paired in the S-1(0) partial wave. The Urca process is suppressed linearly, rather than exponentially, within the temperature range 0.1 less than or equal to T\T-c less than or equal to 1. The charge-current Cooper pair-breaking process contributes up to 50% of the total Urca emissivity in this temperature range. (C) 2004 Elsevier B.V. All rights reserved.