Neutrino emissivity of nonequilibrium<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>β</mml:mi></mml:mrow></mml:math>processes with nucleon superfluidity

Pi, Chun‐Mei; Zheng, Xiaoping; Yang, Shu‐Hua

doi:10.1103/physrevc.81.045802

Cited by 12 publications

(12 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, the size of the threshold determines how much imbalance is to be generated, with a larger imbalance enhancing the heating effect. The effect of nucleon superfluidity on the non-equilibrium beta processes has been considered in the literature [40][41][42][43]. In Refs.…”

Section: Introductionmentioning

confidence: 99%

Cooling theory faced with old warm neutron stars: role of non-equilibrium processes with proton and neutron gaps

Yanagi

Hamaguchi

2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Recent observations have found several candidates for old warm neutron stars whose surface temperatures are above the prediction of the standard neutron star cooling scenario, and thus require some heating mechanism. Motivated by these observations, we study the nonequilibrium beta process in the minimal cooling scenario of neutron stars, which inevitably occurs in pulsars. This out-of-equilibrium process yields the late time heating in the core of a neutron star, called the rotochemical heating, and significantly changes the time evolution of the neutron star surface temperature. To perform a realistic analysis of this heating effect, we include the singlet proton and triplet neutron pairing gaps simultaneously in the calculation of the rate and emissivity of this process, where the dependence of these pairing gaps on the nucleon density is also taken into account. We then compare the predicted surface temperature of neutron stars with the latest observational data. We show the simultaneous inclusion of both proton and neutron gaps is advantageous for the explanation of the old warm neutron stars since it enhances the heating effect. It is then found that the observed surface temperatures of the old warm millisecond pulsars, J2124-3358 and J0437-4715, are explained for various choices of nucleon gap models. The same setup is compatible with the observed temperatures of ordinary pulsars including old warm ones, J0108-1431 and B0950+08, by choosing the initial rotational period of each neutron star accordingly. In particular, the upper limit on the surface temperature of J2144-3933 can be satisfied if its initial period is 10 ms.

show abstract

Section: Introductionmentioning

confidence: 99%

Cooling theory faced with old warm neutron stars: role of non-equilibrium processes with proton and neutron gaps

Yanagi

Hamaguchi

2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…As a result, the imbalance in the chemical potentials of nucleons and leptons increases constantly, which is to be partially dissipated as heat [15][16][17]. This heating effect, called the rotochemical heating, can raise the NS surface temperature up to T s 10 6 K for t 10 6−7 years [18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Dark matter heating vs. rotochemical heating in old neutron stars

Hamaguchi

Yanagi

2019

Physics Letters B

View full text Add to dashboard Cite

Dark matter (DM) particles in the Universe accumulate in neutron stars (NSs) through their interactions with ordinary matter. It has been known that their annihilation inside the NS core causes late-time heating, with which the surface temperature becomes a constant value of Ts (2 − 3) × 10 3 K for the NS age t 10 6−7 years. This conclusion is, however, drawn based on the assumption that the beta equilibrium is maintained in NSs throughout their life, which turns out to be invalid for rotating pulsars. The slowdown in the pulsar rotation drives the NS matter out of beta equilibrium, and the resultant imbalance in chemical potentials induces late-time heating, dubbed as rotochemical heating. This effect can heat a NS up to Ts 10 6 K for t 10 6−7 years. In fact, recent observations found several old NSs whose surface temperature is much higher than the prediction of the standard cooling scenario and is consistent with the rotochemical heating. Motivated by these observations, in this letter, we reevaluate the significance of the DM heating in NSs, including the effect of the rotochemical heating. We then show that the signature of DM heating can still be detected in old ordinary pulsars, while it is concealed by the rotochemical heating for old millisecond pulsars. To confirm the evidence for the DM heating, however, it is necessary to improve our knowledge on nucleon pairing gaps as well as to evaluate the initial period of the pulsars accurately. In any cases, a discovery of a very cold NS can give a robust constraint on the DM heating, and thus on DM models. To demonstrate this, as an example, we also discuss the case that the DM is the neutral component of an electroweak multiplet, and show that an observation of a NS with Ts 10 3 K imposes a stringent constraint on such a DM candidate.

show abstract

“…For β k B T, superfluidity and supercon- ductivity exponentially suppress the rate of Urca processes (Yakovlev et al 2001). However, for β > ∼ k B T c k B T, there is very little suppression (Pi et al 2010;Alford et al 2012). Since we find that β ∼ 1 MeV > ∼ k B T c for ν orb > ∼ 100 Hz, the Urca reaction rates and emissivities should approximately equal those of a normal fluid during the late inspiral.…”

Section: Introductionmentioning

confidence: 99%

Urca reactions during neutron star inspiral

Arras

Weinberg

2019

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We study the impact of nonlinear bulk viscosity due to Urca reactions driven by tidally-induced fluid motion during binary neutron star inspiral. Fluid compression is computed for low radial order oscillation modes through an adiabatic, time-dependent solution of the mode amplitudes. Optically thin neutrino emission and heating rates are then computed from this adiabatic fluid motion. Calculations use direct and modified Urca reactions operating in a M = 1.4 M neutron star, which is constructed using the Skyrme Rs equation of state. We find that the energy pumped into low order oscillation modes is not efficiently thermalized even by direct Urca reactions, with core temperatures reaching only T 10 8 K during the inspiral. Although this is an order of magnitude larger than the heating due to shear viscosity considered by previous studies, it reinforces the result that the stars are quite cold at merger. Upon excitation of the lowest order g-mode, the chemical potential imbalance reaches β > ∼ 1 MeV at orbital frequencies ν orb > ∼ 200 Hz, implying significant charged-current optical depths and Fermi blocking. To asses the importance of neutrino degeneracy effects, the neutrino transfer equation is solved in the static approximation for the three-dimensional density distribution, and the reaction rates are then computed including Fermi-blocking. We find that the heating rate is suppressed by factors of a few for ν orb > ∼ 200 Hz. The spectrum of emitted ν e andν e , including radiation transfer effects, is presented for a range of orbital separations.

show abstract

Neutrino emissivity of nonequilibriumβprocesses with nucleon superfluidity

Cited by 12 publications

References 15 publications

Cooling theory faced with old warm neutron stars: role of non-equilibrium processes with proton and neutron gaps

Cooling theory faced with old warm neutron stars: role of non-equilibrium processes with proton and neutron gaps

Dark matter heating vs. rotochemical heating in old neutron stars

Urca reactions during neutron star inspiral

Contact Info

Product

Resources

About