scholarly journals Spin-Down of Neutron Stars and Compositional Transitions in the Cold Crustal Matter

1998 ◽  
Vol 188 ◽  
pp. 345-345 ◽  
Author(s):  
Kei Iida ◽  
Katsuhiko Sato
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Ground State ◽  
Rotation Axis ◽  
Mass Density ◽  
Rotation Period ◽  
Equatorial Region ◽  
Compressible Liquid ◽  
Shell Correction ◽  
X Ray

Transitions of nuclear compositions in the crust of a neutron star induced by stellar spin-down are evaluated at zero temperature. We construct a compressible liquid-drop model for the energy of nuclei immersed in a neutron gas, including pairing and shell correction terms, in reference to the known properties of the ground state of matter above neutron drip density, 4.3 × 1011 g cm−3. Recent experimental values and extrapolations of nuclear masses are used for a description of matter at densities below neutron drip. Changes in the pressure of matter in the crust due to the stellar spin-down are calculated by taking into account the structure of the crust of a slowly and uniformly rotating relativistic neutron star. If the initial rotation period is of the order of milliseconds, these changes cause nuclei, initially being in the ground-state matter above a mass density of about 3 × 1013 g cm−3, to absorb neutrons in the equatorial region where the matter undergoes compression, and to emit them in the vicinity of the rotation axis where the matter undergoes decompression. Heat generation by these processes is found to have significant effects on the thermal evolution of old neutron stars with low magnetic fields; the surface emission predicted from this heating is compared with the ROSAT observations of X-ray emission from millisecond pulsars and is shown to be insufficient to explain the observed X-ray luminosities (Iida and Sato, 1997).

BIRTH RATES OF DIFFERENT TYPES OF NEUTRON STARS AND POSSIBLE EVOLUTIONS OF THESE OBJECTS

2005 ◽  
Vol 14 (03n04) ◽  
pp. 643-656 ◽  
Author(s):  
OKTAY H. GUSEINOV ◽  
AŞKIN ANKAY ◽  
SEVINÇ O. TAGIEVA
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Neutron Stars ◽  
Rotation Axis ◽  
Solar Mass ◽  
Birth Rates ◽  
X Ray ◽  
Soft Gamma Repeaters ◽  
Different Types ◽  
The Magnetic Field

It is shown that anomalous X-ray pulsars and soft gamma repeaters are neutron stars with mass less than 1 solar mass and with magnetic field about 3×1013–1014 G . Their ages (t≤105 yr ) are considerably larger than their characteristic times. The angle between the rotation axis and the axis of the magnetic field must be large for these objects. From time to time as a result of activities their value of Ṗ considerably increases because of the propeller mechanism. Using such an approach Guseinov et al.1 have predicted the transient characteristic of these sources which has been confirmed recently.2 We estimate the spatial densities and lifetimes of different types of isolated neutron star. Some of these sources must have relations with anomalous X-ray pulsars and soft gamma repeaters. In order to understand the locations of different types of isolated neutron star on the P–Ṗ diagram it is also necessary to take into account the differences in the mass and the magnetic field of neutron stars. We have also estimated the birth rates of different types of isolated neutron stars.

DO YOUNG NEUTRON STARS WHICH SHOW THEMSELVES AS AXPs AND SGRs ACCRETE?

2003 ◽  
Vol 12 (05) ◽  
pp. 825-831 ◽  
Author(s):  
S. O. TAGIEVA ◽  
E. YAZGAN ◽  
A. ANKAY
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Explosion ◽  
X Ray ◽  
X Ray Binaries

We examined the fall-back disk models, and in general accretion, proposed to explain the properties of AXPs and SGRs. We checked the possibility of some gas remaining around the neutron star after a supernova explosion. We also compared AXPs and SGRs with the X-ray pulsars in X-ray binaries. We conclude that the existing models of accretion from a fall-back disk are insufficient to explain the nature of AXPs and SGRs.

scholarly journals Physical Processes and Parameters in the Magnetosphere of NP 0532

1971 ◽  
Vol 46 ◽  
pp. 394-406
Author(s):  
F. Pacini
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Remnants ◽  
Crab Nebula ◽  
General Relation ◽  
Energy Generation ◽  
Main Pulse ◽  
Physical Processes ◽  
X Ray ◽  
The Crab Nebula

The Crab Nebula pulsar conforms to the model of a rotating magnetised neutron star in the rate of energy generation and the exponent of the rotation law.It is suggested that the main pulse is due to electrons and the precursor to protons. Both must radiate in coherent bunches. Optical and X-ray radiation is by the synchrotron process.The wisps observed in the Nebula may represent the release of an instability storing about 1043 erg and 1047–48 particles.Finally, some considerations are made about the general relation between supernova remnants and rotating neutron stars.

scholarly journals Models for Compact Pulsing X-Ray Sources

1973 ◽  
Vol 55 ◽  
pp. 143-154 ◽  
Author(s):  
Jeremiah P. Ostriker ◽  
Kris Davidson
Keyword(s):  
Neutron Star ◽  
Rotation Period ◽  
Critical Value ◽  
Blackbody Radiation ◽  
Roche Lobe ◽  
Magnetic Pole ◽  
Solar Mass ◽  
Centrifugal Barrier ◽  
Companion Star ◽  
X Ray

Cen X-3 is probably a neutron star, releasing the infall energy of accreted matter. Sufficient material for accretion will be provided by a conventional stellar wind from its more massive companion star. That star is not likely to rotate synchronously; therefore a ‘Roche lobe’ analysis of the eclipses is not valid. A ‘tidal lobe’ analysis allows the neutron star to have a mass of the order of one solar mass. Overflow of the ‘Roche lobe’ is neither necessary as a source of mass nor probable in view of the observed stellar line widths of the two identified X-ray companions.The mass flow onto the condensed star is very small in all cases. It is limited, for an object of m solar masses by the Eddington Limiting Luminosity to Ṁac < 10–7.4m(M⊙ yr−1), which limit applies even if the accreting object contacts or traverses its companion star.The observed 4.84 s rotation period of the Cen X-3 neutron star is very simply explained as the critical value where a centrifugal barrier regulates the rate of infall to the surface. The X-ray spectrum is understood as blackbody radiation coming from a well-defined area near each magnetic pole of the neutron star.

scholarly journals Effect of Compact Objects Near Be Stars

1987 ◽  
Vol 92 ◽  
pp. 516-518
Author(s):  
Krishna M.V. Apparao ◽  
S.P. Tarafdar
Keyword(s):  
Black Holes ◽  
Neutron Star ◽  
Rotation Period ◽  
Compact Object ◽  
Compact Objects ◽  
X Rays ◽  
Be Stars ◽  
Eccentric Orbit ◽  
X Ray ◽  
Be Star

Several Be stars are identified with bright X-ray sources. (Rappaport and Van den Heuvel, 1982). The bright X-ray emission and observed periodicities indicate the existence of compact objects (white dwarfs, neutron stars or black holes) near the Be stars. A prime example is the brightest X-ray source A0538-66 in LMC, which contains a neutron star with a rotation period of 59 ms. Apparao (1985) explained the X-ray emission, which occurs in periodic flares, by considering an inclined eccentric orbit for the neutron star around the assumed Be-star. The neutron star when it enters a gas ring (around the Be-star) accreting matter giving out X-rays.The X-ray emission from the compact objects, when the gas ring from the Be-star envelopes the objects, has interesting consequences. The X-ray emission produces an ionized region (compact object Stromgren sphere or COSS) in the gas surrounding the compact object (CO).

scholarly journals The X-Ray Timing Explorer

1990 ◽  
Vol 123 ◽  
pp. 89-110
Author(s):  
H. V. Bradt ◽  
A. M. Levine ◽  
E. H. Morgan ◽  
R. A. Remillard ◽  
J. H. Swank ◽  
...  
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Active Galactic Nuclei ◽  
High Throughput ◽  
Proportional Counter ◽  
Galactic Nuclei ◽  
X Ray ◽  
Sky Monitor ◽  
Proportional Counter Array ◽  
Millisecond Timing

AbstractThe capabilities of the X-ray Timing Explorer (XTE) are described with particular attention paid to current scientific problems it will address from galactic neutron star systems to active galactic nuclei. It features a low-background continuous 2-200 keV response with large apertures (a 0.63-m2 proportional counter array and a 0.16-m2 dual rocking NaI/CsI scintillation array). Rapid response (in hours) to temporal phenomena, e.g. transients, is obtained by virtue of a scanning all-sky monitor and rapid maneuverability. XTE will carry out detailed energy-resolved studies of phenomena close to neutron stars (e.g. QPO’s) because of its sub-millisecond timing (to 10 μs), its high telemetry rates (to 256 kb/s), and the high throughput of its data system (to ≳ 2 × 105 c s−1).

scholarly journals Estimation of Electrical Conductivity and Magnetization Parameter of Neutron Star Crusts and Applied to the High-Braking-Index Pulsar PSR J1640-4631

Universe ◽  
2020 ◽  
Vol 6 (5) ◽  
pp. 63
Author(s):  
Hui Wang ◽  
Zhi-Fu Gao ◽  
Huan-Yu Jia ◽  
Na Wang ◽  
Xiang-Dong Li
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Neutron Stars ◽  
General Expression ◽  
Equations Of State ◽  
Rotation Period ◽  
Ohmic Dissipation ◽  
Hartree Fock ◽  
Induction Equation ◽  
The Magnetic Field

Young pulsars are thought to be highly magnetized neutron stars (NSs). The crustal magnetic field of a NS usually decays at different timescales in the forms of Hall drift and Ohmic dissipation. The magnetization parameter ω B τ is defined as the ratio of the Ohmic timescale τ O h m to the Hall drift timescale τ H a l l . During the first several million years, the inner temperature of the newly born neutron star cools from T = 10 9 K to T = 1.0 × 10 8 K, and the crustal conductivity increases by three orders of magnitude. In this work, we adopt a unified equations of state for cold non-accreting neutron stars with the Hartree–Fock–Bogoliubov method, developed by Pearson et al. (2018), and choose two fiducial dipole magnetic fields of B = 1.0 × 10 13 G and B = 1.0 × 10 14 G, four different temperatures, T, and two different impurity concentration parameters, Q, and then calculate the conductivity of the inner crust of NSs and give a general expression of magnetization parameter for young pulsars: ω B τ ≃ ( 1 − 50 ) B 0 / ( 10 13 G) by using numerical simulations. It was found when B ≤ 10 15 G, due to the quantum effects, the conductivity increases slightly with the increase in the magnetic field, the enhanced magnetic field has a small effect on the matter in the low-density regions of the crust, and almost has no influence the matter in the high-density regions. Then, we apply the general expression of the magnetization parameter to the high braking-index pulsar PSR J1640-4631. By combining the observed arrival time parameters of PSR J1640-4631 with the magnetic induction equation, we estimated the initial rotation period P 0 , the initial dipole magnetic field B 0 , the Ohm dissipation timescale τ O h m and Hall drift timescale τ H a l l . We model the magnetic field evolution and the braking-index evolution of the pulsar and compare the results with its observations. It is expected that the results of this paper can be applied to more young pulsars.

scholarly journals X-ray Emission Characteristics of Pulsars

2000 ◽  
Vol 195 ◽  
pp. 49-60
Author(s):  
W. Becker
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Emission Characteristics ◽  
Millisecond Pulsars ◽  
X Ray ◽  
Emission Properties ◽  
Important Progress

Recent X-ray observatories such as ROSAT, ASCA, RXTE, BeppoSAX, and Chandra have achieved important progress in neutron star and pulsar astronomy. The identification of Geminga as a rotation-powered pulsar, the discovery of X-ray emission from millisecond pulsars, and the identification of cooling neutron stars are only a few of the fascinating results. In the following, I will give a brief review on the X-ray emission properties of rotation-powered pulsars and their wind nebulae.

scholarly journals A Bayesian approach to matching thermonuclear X-ray burst observations with models

2019 ◽  
Vol 490 (2) ◽  
pp. 2228-2240 ◽  
Author(s):  
A J Goodwin ◽  
D K Galloway ◽  
A Heger ◽  
A Cumming ◽  
Z Johnston
Keyword(s):  
Neutron Star ◽  
Rotation Axis ◽  
Line Of Sight ◽  
Type I ◽  
X Ray ◽  
Star Mass ◽  
Disc Model ◽  
Neutron Star Mass ◽  
Hydrogen Mass ◽  
Neutron Star Radius

ABSTRACT We present a new method of matching observations of Type-I (thermonuclear) X-ray bursts with models, comparing the predictions of a semi-analytic ignition model with X-ray observations of the accretion-powered millisecond pulsar SAX J1808.4–3658 in outburst. We used a Bayesian analysis approach to marginalize over the parameters of interest and determine parameters such as fuel composition, distance/anisotropy factors, neutron star mass, and neutron star radius. Our study includes a treatment of the system inclination effects, inferring that the rotation axis of the system is inclined $\left(69^{+4}_{-2}\right)^\circ$ from the observers line of sight, assuming a flat disc model. This method can be applied to any accreting source that exhibits Type-I X-ray bursts. We find a hydrogen mass fraction of $0.57^{+0.13}_{-0.14}$ and CNO metallicity of $0.013^{+0.006}_{-0.004}$ for the accreted fuel is required by the model to match the observed burst energies, for a distance to the source of $3.3^{+0.3}_{-0.2}\, \mathrm{kpc}$. We infer a neutron star mass of $1.5^{+0.6}_{-0.3}\, \mathrm{M}_{\odot }$ and radius of $11.8^{+1.3}_{-0.9}\, \mathrm{km}$ for a surface gravity of $1.9^{+0.7}_{-0.4}\times 10^{14}\, \mathrm{cm}\, \mathrm{s}^{-2}$ for SAX J1808.4–3658.

scholarly journals Astrophysical implications of neutron star inspiral and coalescence

2020 ◽  
Vol 29 (11) ◽  
pp. 2041015
Author(s):  
John L. Friedman ◽  
Nikolaos Stergioulas
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Maximum Mass ◽  
X Ray ◽  
Spectral Bands ◽  
Heaviest Elements ◽  
X Ray Binaries

The first inspiral of two neutron stars observed in gravitational waves was remarkably close, allowing the kind of simultaneous gravitational wave and electromagnetic observation that had not been expected for several years. Their merger, followed by a gamma-ray burst and a kilonova, was observed across the spectral bands of electromagnetic telescopes. These GW and electromagnetic observations have led to dramatic advances in understanding short gamma-ray bursts; determining the origin of the heaviest elements; and determining the maximum mass of neutron stars. From the imprint of tides on the gravitational waveforms and from observations of X-ray binaries, one can extract the radius and deformability of inspiraling neutron stars. Together, the radius, maximum mass, and causality constrain the neutron-star equation of state, and future constraints can come from observations of post-merger oscillations. We selectively review these results, filling in some of the physics with derivations and estimates.

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