Neutron star heating vs. HST observations

Abstract

Passively cooling neutron stars (NSs) should reach undetectably low surface temperatures $T_s<10^4$ K in less than $10^7$ yr. However, HST observations have revealed likely thermal UV emission from the Gyr-old millisecond pulsars PSR~J0437$-$4715 and PSR~J2124$-$3358, and from the $\sim 10^{7-8}$ yr-old classical pulsars PSR~B0950$+$08 and PSR~J0108$-$1431, implying $T_s\sim 10^5$ K and the need for heating mechanisms. We compute the thermal evolution of these NSs including rotochemical heating (RH) in the core with normal or Cooper-paired matter, vortex creep (VC) in the inner crust, and crustal heating through nuclear reactions, and compare the results with observations and with the upper limit for PSR~2144$-$3933. No single mechanism explains all sources. The high temperature of PSR~J0437$-$4715 can be reproduced by RH with a large Cooper pairing gap ${\Delta }_i\sim 1.5$ MeV for either neutrons or protons, but this requires an unrealistically short initial period $P_0\lesssim 1.8$ ms to activate the same mechanism in PSR~B0950$+$08. Conversely, the latter can be explained by RH with modified Urca reactions in normal matter or by VC with an excess angular momentum $J\sim 3\times 10^{43}$ erg,s, but these models underpredict PSR~J0437$-$4715. A model combining RH with a large pairing gap and VC matches both pulsars and is consistent with the upper limits for the remaining three. It further predicts that their temperatures should lie close to these limits, suggesting that deeper or broader-wavelength observations would provide a strong test of this scenario.

References in corpus (44)

• The ATNF Pulsar Catalogue
• A Radio Pulsar Spinning at 716 Hz
• Neutron Star Cooling
• Birth and Evolution of Isolated Radio Pulsars
• Neutrino Emission from Neutron Stars
• On the Mass Distribution and Birth Masses of Neutron Stars
• Neutron Stars as Dark Matter Probes
• A NICER View of the Nearest and Brightest Millisecond Pulsar: PSR J0437$\unicode{x2013}$4715
• Can Neutron stars constrain Dark Matter?
• Pulsar Polar Cap Heating and Surface Thermal X-Ray Emission II. Inverse Compton Radiation Pair Fronts
• Magnetic Field Evolution in Neutron Star Crusts due to the Hall Effect and Ohmic Decay
• VLBA Measurement of Nine Pulsar Parallaxes
• Constraining the Neutron Star Mass-Radius Relation and Dense Matter Equation of State with NICER. I. The Millisecond Pulsar X-ray Data Set
• Precision southern hemisphere VLBI pulsar astrometry II: Measurement of seven parallaxes
• Atmospheres and radiating surfaces of neutron stars
• Ultraviolet Emission from the Millisecond Pulsar J0437-4715
• Internal Heating of Old Neutron Stars: Contrasting Different Mechanisms
• LOFAR discovery of the fastest-spinning millisecond pulsar in the Galactic field
• The spectrum of the recycled PSR J0437-4715 and its white dwarf companion
• Rotochemical Heating in Millisecond Pulsars. Formalism and Non-superfluid case
• The neutron star mass, distance, and inclination from precision timing of the brilliant millisecond pulsar J0437$-$4715
• Neutron star radius measurement from the ultraviolet and soft X-ray thermal emission of PSR J0437-4715
• Hubble Space Telescope detection of the millisecond pulsar J2124-3358 and its far-ultraviolet bow shock nebula
• Hubble Space Telescope non-detection of PSR J2144-3933: the coldest known neutron star
• Old but still warm: Far-UV detection of PSR B0950+08
• Thermodynamically consistent equation of state for an accreted neutron star crust
• The NuSTAR view of the non-thermal emission from PSR J0437-4715
• Rotochemical heating in millisecond pulsars: modified Urca reactions with uniform Cooper pairing gaps
• Cooling Theory Faced with Old Warm Neutron Stars: Role of Non-Equilibrium Processes with Proton and Neutron Gaps
• Rotation-induced deep crustal heating of millisecond pulsars
• Rotochemical heating of millisecond and classical pulsars with anisotropic and density-dependent superfluid gap models
• Magnetic field evolution timescales in superconducting neutron stars
• Ages of radio pulsar: long-term magnetic field evolution
• Thermal and nonthermal emission in the optical-UV spectrum of PSR B0950+08
• Leptonic contribution to the bulk viscosity of nuclear matter
• Rotochemical Heating of Neutron Stars: Rigorous Formalism with Electrostatic Potential Perturbations
• On the weak magnetic field of millisecond pulsars: Does it decay before accretion?
• 3D evolution of neutron star magnetic-fields from a realistic core-collapse turbulent topology
• Long-lasting accretion-powered chemical heating of millisecond pulsars
• XMM-Newton detection and spectrum of the second fastest spinning pulsar PSR J0952-0607
• Hubble Space Telescope observations of the old pulsar PSR J0108-1431
• On the initial spin period distribution of neutron stars
• Long-period thermal oscillations in superfluid millisecond pulsars
• Born to be recycled: a comprehensive population synthesis of the Galactic millisecond pulsars