Wednesday, December 14, 2011

1103.3870 (Rodrigo Negreiros et al.)

Impact of Rotation-Driven Particle Repopulation on the Thermal Evolution of Pulsars    [PDF]

Rodrigo Negreiros, Stefan Schramm, Fridolin Weber
Driven by the loss of energy, isolated rotating neutron stars (pulsars) are gradually slowing down to lower frequencies, which monotonically increases the tremendous compression of the matter inside of them. This increase in compression changes both the global properties of rotating neutron stars as well as their hadronic core compositions. Both effects may register themselves observationally in the thermal evolution of such stars, as demonstrated in this Letter. The rotation-driven particle process which we consider is the direct Urca (DU) process, which is known to become operative in neutron stars if the number of protons in the stellar core exceeds a critical limit of around 11% to 15%. We find that neutron stars spinning down from moderately high rotation rates of a few hundred Hertz may be creating just the right conditions where the DU process becomes operative, leading to an observable effect (enhanced cooling) in the temperature evolution of such neutron stars. We also find that the rotation-driven DU process can comfortably explain the temperatures observed for the neutron star in Cas A provided the mass of this neutron star is assumed to be around 1.5 -- 1.9 \msun. Finally, a preliminary estimate of the temperature of the recently discovered massive neutron star PSR J1614-2230, which rotates at 317 Hz, indicates that the rotation-driven DU process may have cooled this neutron star to remarkably low temperatures of $\lsim 10^6$ K.
View original: http://arxiv.org/abs/1103.3870

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