scholarly journals A universal formula for the relativistic correction to the mutual friction coupling time-scale in neutron stars

2020 ◽  
Vol 494 (3) ◽  
pp. 3562-3580 ◽  
Author(s):  
L Gavassino ◽  
M Antonelli ◽  
P M Pizzochero ◽  
B Haskell
Keyword(s):  
General Relativity ◽  
Neutron Star ◽  
Time Scale ◽  
Outer Core ◽  
Relativistic Correction ◽  
Quantized Vortices ◽  
Universal Relation ◽  
Mutual Friction ◽  
Universal Formula ◽  
Coupling Time

ABSTRACT Vortex-mediated mutual friction governs the coupling between the superfluid and normal components in neutron star interiors. By, for example, comparing precise timing observations of pulsar glitches with theoretical predictions it is possible to constrain the physics in the interior of the star, but to do so an accurate model of the mutual friction coupling in general relativity is needed. We derive such a model directly from Carter’s multifluid formalism, and study the vortex structure and coupling time-scale between the components in a relativistic star. We calculate how general relativity modifies the shape and the density of the quantized vortices and show that, in the quasi-Schwarzschild coordinates, they can be approximated as straight lines for realistic neutron star configurations. Finally, we present a simple universal formula (given as a function of the stellar compactness alone) for the relativistic correction to the glitch rise-time, which is valid under the assumption that the superfluid reservoir is in a thin shell in the crust or in the outer core. This universal relation can be easily employed to correct, a posteriori, any Newtonian estimate for the coupling time-scale, without any additional computational expense.

scholarly journals Superfluid vortex-mediated mutual friction in non-homogeneous neutron star interiors

2020 ◽  
Vol 499 (3) ◽  
pp. 3690-3705
Author(s):  
M Antonelli ◽  
B Haskell
Keyword(s):  
Neutron Star ◽  
Normal Component ◽  
Homogeneous Medium ◽  
Outer Core ◽  
Two Dimensions ◽  
Pinning Force ◽  
Mutual Friction ◽  
Momentum Exchange ◽  
Drag Forces ◽  
Vortex Lines

ABSTRACT Understanding the average motion of a multitude of superfluid vortices in the interior of a neutron star is a key ingredient for most theories of pulsar glitches. In this paper, we propose a kinetic approach to compute the mutual friction force that is responsible for the momentum exchange between the normal and superfluid components in a neutron star, where the mutual friction is extracted from a suitable average over the motion of many vortex lines. As a first step towards a better modelling of the repinning and depinning processes of many vortex lines in a neutron star, we consider here only straight and non-interacting vortices: we adopt a minimal model for the dynamics of an ensemble of point vortices in two dimensions immersed in a non-homogeneous medium that acts as a pinning landscape. Since the degree of disorder in the inner crust or outer core of a neutron star is unknown, we compare the two possible scenarios of periodic and disordered pinscapes. This approach allows us to extract the mutual friction between the superfluid and the normal component in the star when, in addition to the usual Magnus and drag forces acting on vortex lines, also a pinning force is at work. The effect of disorder on the depinning transition is also discussed.

Merger of black hole and neutron star in general relativity

2008 ◽  
Author(s):  
Masaru Shibata ◽  
Keisuke Taniguchi ◽  
Koji Uryū ◽  
Ye-Fei Yuan ◽  
Xiang-Dong Li ◽  
...  
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Neutron Star

scholarly journals 1S0 Pairing Gaps, Chemical Potentials and Entrainment Matrix in Superfluid Neutron-Star Cores for the Brussels–Montreal Functionals

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 470
Author(s):  
Valentin Allard ◽  
Nicolas Chamel
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Physical Meaning ◽  
Outer Core ◽  
Time Dependent ◽  
Hartree Fock ◽  
Chemical Potentials ◽  
Bogoliubov Equations ◽  
Flow Velocities

Temperature and velocity-dependent 1S0 pairing gaps, chemical potentials and entrainment matrix in dense homogeneous neutron–proton superfluid mixtures constituting the outer core of neutron stars, are determined fully self-consistently by solving numerically the time-dependent Hartree–Fock–Bogoliubov equations over the whole range of temperatures and flow velocities for which superfluidity can exist. Calculations have been made for npeμ in beta-equilibrium using the Brussels–Montreal functional BSk24. The accuracy of various approximations is assessed and the physical meaning of the different velocities and momentum densities appearing in the theory is clarified. Together with the unified equation of state published earlier, the present results provide consistent microscopic inputs for modeling superfluid neutron-star cores.

scholarly journals Torque Reversals in Disk Accreting Pulsars

1998 ◽  
Vol 15 (2) ◽  
pp. 250-253
Author(s):  
Jianke Li ◽  
Dayal T. Wickramasinghe
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
Recent Work ◽  
Time Scale ◽  
Accretion Rate ◽  
Future Studies ◽  
X Ray ◽  
The Past ◽  
X Ray Binaries ◽  
Coherent Picture

AbstractX-ray binaries in which the accreting component is a neutron star commonly exhibit significant changes in their spin. In the system Cen X-3, a disk accreting binary system, the pulsar was observed to spin up at a rate ḟ = 8 × 10−13 Hz s−1 when averaged over the past twenty years, but significant fluctuations were observed above this mean. Recent BASTE observations have disclosed that these fluctuations are much larger than previously noted, and appeared to be a system characteristic. The change in the spin state from spin-up to spin-down or vice-versa occurs on a time scale that is much shorter than the instrument can resolve (≤1 d), but appears always to be a similar amplitude, and to occur stochastically. These observations have posed a problem for the conventional torque–mass accretion relation for accreting pulsars, because in this model the spin rate is closely related to the accretion rate, and the latter needs to be finely tuned and to change abruptly to explain the observations. Here we review recent work in this direction and present a coherent picture that explains these observations. We also draw attention to some outstanding problems for future studies.

scholarly journals Neutron star mergers as a probe of modifications of general relativity with finite-range scalar forces

2018 ◽  
Vol 97 (6) ◽  
Author(s):  
Laura Sagunski ◽  
Jun Zhang ◽  
Matthew C. Johnson ◽  
Luis Lehner ◽  
Mairi Sakellariadou ◽  
...  
Keyword(s):  
General Relativity ◽  
Neutron Star ◽  
Finite Range

scholarly journals Luminosity–duration relations and luminosity functions of repeating and non-repeating fast radio bursts

2020 ◽  
Vol 494 (2) ◽  
pp. 2886-2904 ◽  
Author(s):  
Tetsuya Hashimoto ◽  
Tomotsugu Goto ◽  
Ting-Wen Wang ◽  
Seong Jin Kim ◽  
Simon C-C Ho ◽  
...  
Keyword(s):  
Neutron Star ◽  
Time Scale ◽  
Gamma Ray ◽  
Clear Correlation ◽  
Type Ia Supernovae ◽  
Radio Bursts ◽  
Luminosity Functions ◽  
Type Ia ◽  
Ia Supernovae ◽  
Two Populations

ABSTRACT Fast radio bursts (FRBs) are mysterious radio bursts with a time-scale of approximately milliseconds. Two populations of FRB, namely repeating and non-repeating FRBs, are observationally identified. However, the differences between these two and their origins are still cloaked in mystery. Here we show the time-integrated luminosity–duration (Lν–wint, rest) relations and luminosity functions (LFs) of repeating and non-repeating FRBs in the FRB Catalogue project. These two populations are obviously separated in the Lν-wint, rest plane with distinct LFs, i.e. repeating FRBs have relatively fainter Lν and longer wint, rest with a much lower LF. In contrast with non-repeating FRBs, repeating FRBs do not show any clear correlation between Lν and wint, rest. These results suggest essentially different physical origins of the two. The faint ends of the LFs of repeating and non-repeating FRBs are higher than volumetric occurrence rates of neutron star (NS) mergers and accretion-induced collapse (AIC) of white dwarfs (WDs), and are consistent with those of soft gamma-ray repeaters (SGRs), Type Ia supernovae (SNe Ia), magnetars, and WD mergers. This indicates two possibilities: either (i) faint non-repeating FRBs originate in NS mergers or AIC and are actually repeating during the lifetime of the progenitor, or (ii) faint non-repeating FRBs originate in any of SGRs, SNe Ia, magnetars, and WD mergers. The bright ends of LFs of repeating and non-repeating FRBs are lower than any candidates of progenitors, suggesting that bright FRBs are produced from a very small fraction of the progenitors regardless of the repetition. Otherwise, they might originate in unknown progenitors.

scholarly journals Radio emission from a pulsar’s magnetic pole revealed by general relativity

Science ◽  
2019 ◽  
Vol 365 (6457) ◽  
pp. 1013-1017 ◽  
Author(s):  
Gregory Desvignes ◽  
Michael Kramer ◽  
Kejia Lee ◽  
Joeri van Leeuwen ◽  
Ingrid Stairs ◽  
...  
Keyword(s):  
General Relativity ◽  
Neutron Star ◽  
Radio Emission ◽  
Neutron Stars ◽  
Geometrical Model ◽  
Spin Axis ◽  
Magnetic Pole ◽  
Polarization Model ◽  
Binary Pulsars ◽  
Relativistic Treatment

Binary pulsars are affected by general relativity (GR), causing the spin axis of each pulsar to precess. We present polarimetric radio observations of the pulsar PSR J1906+0746 that demonstrate the validity of the geometrical model of pulsar polarization. We reconstruct the (sky-projected) polarization emission map over the pulsar’s magnetic pole and predict the disappearance of the detectable emission by 2028. Two tests of GR are performed using this system, including the spin precession for strongly self-gravitating bodies. We constrain the relativistic treatment of the pulsar polarization model and measure the pulsar beaming fraction, with implications for the population of neutron stars and the expected rate of neutron star mergers.

THE DOUBLE PULSAR SYSTEM J0737–3039

2005 ◽  
Vol 20 (29) ◽  
pp. 7035-7044 ◽  
Author(s):  
D. R. LORIMER
Keyword(s):  
General Relativity ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Detection Rate ◽  
Order Effects ◽  
Gravitational Wave Detector ◽  
High Detection Rate ◽  
Wave Detector ◽  
High Detection ◽  
Order Of Magnitude

The double pulsar system J0737 – 3039 – a 22.7 ms pulsar in a compact 2.4 hr orbit about a 2.7 s pulsar was one of the long-awaited "holy grails" of pulsar astronomy. After only two years of timing, the system is close to surpassing the original Hulse-Taylor binary as a test of general relativity. On-going timing should soon reveal second-order effects in the post-Newtonian parameters. In addition, the observed interactions of the radio beams of the two pulsars provide a unique laboratory for probing neutron star magnetospheres and relativistic winds. Finally, a revised estimate of the cosmic rate of double neutron star mergers including J0737 – 3039 boosts previous estimates by an order of magnitude and suggests a high detection rate for the advanced LIGO gravitational wave detector.

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