Magnetar superconductivity versus magnetism: neutrino cooling processes

Monika Sinha; Armen Sedrakian

doi:10.1103/PhysRevC.91.035805

paper

Magnetar superconductivity versus magnetism: neutrino cooling processes

arXiv:1502.02979 · doi:10.1103/PhysRevC.91.035805

Abstract

We describe the microphysics, phenomenology, and astrophysical implication of a $B$ -field induced unpairing effect that may occur in magnetars, if the local $B$ -field in the core of a magnetar exceeds a critical value $H_{c 2}$ . Using the Ginzburg-Landau theory of superconductivity, we derive the $H_{c 2}$ field for proton condensate taking into the correction ( $\leq 30%$ ) which arises from its coupling to the background neutron condensate. The density dependence of pairing of proton condensate implies that $H_{c 2}$ is maximal at the crust-core interface and decreases towards the center of the star. As a consequence, magnetar cores with homogenous constant fields will be partially superconducting for "medium-field" magnetars ( $1 0^{15} \leq B \leq 5 \times 1 0^{16}$ G) whereas "strong-field" magnetars ( $B > 5 \times 1 0^{16}$ G) will be void of superconductivity. The neutrino emissivity of a magnetar's core changes in a twofold manner: (i)~the $B$ -field assisted direct Urca process is enhanced by orders of magnitude, because of the unpairing effect in regions where $B \geq H_{c 2}$ ; (ii)~the Cooper-pair breaking processes on protons vanish in these regions and the overall emissivity by the pair-breaking processes is reduced by a factor of only a few.

arXiv commentv2: minor changes, matches published version; v1: 10 RevTex two-column pages, 7 figures

Magnetar superconductivity versus magnetism: neutrino cooling processes

Abstract

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