Astronomy & Astrophysics

Free access article

A&A 423, 1063-1071 (2004)
DOI: 10.1051/0004-6361:20041006

Enhanced cooling of neutron stars via Cooper-pairing neutrino emission

M. E. Gusakov¹, A. D. Kaminker¹, D. G. Yakovlev¹ and O. Y. Gnedin²

¹ Ioffe Physical Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg, Russia
e-mail: [gusakov;kam;yak]@astro.ioffe.ru
² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
e-mail: ognedin@stsci.edu

(Received 1 April 2004 / Accepted 2 May 2004 )

Abstract
We simulate cooling of superfluid neutron stars with nucleon cores where the direct Urca process is forbidden. We adopt density-dependent critical temperatures $T_{\rm cp}(\rho)$ and $T_{\rm cn}(\rho)$ of singlet-state proton and triplet-state neutron pairing in a stellar core and consider strong proton pairing (with maximum $T_{\rm cp}^{\rm max} \ga 5 \times 10^9$ K) and moderate neutron pairing ( $T_{\rm cn}^{\rm max} \sim 6 \times 10^8$ K). When the internal stellar temperature T falls below $T_{\rm cn}^{\rm max}$ , the neutrino luminosity $L_{\rm CP}$ due to Cooper pairing of neutrons behaves $\propto$ T⁸, just as that produced by the modified Urca process (in a non-superfluid star) but is higher by about two orders of magnitude. In this case the Cooper-pairing neutrino emission acts like an enhanced cooling agent. By tuning the density dependence $T_{\rm cn}(\rho)$ we can explain observations of cooling isolated neutron stars in the scenario in which the direct Urca process or a similar process in kaon/pion condensed or quark matter are absent.

Key words: stars: neutron -- dense matter

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