scholarly journals Bumpy Spin-Down of Anomalous X-Ray Pulsars: The Link with Magnetars

2000 ◽  
Vol 177 ◽  
pp. 691-694
Author(s):  
A. Melatos
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Equations Of Motion ◽  
Recurrence Time ◽  
Statistical Relation ◽  
Dipole Radiation ◽  
X Ray ◽  
Euler’S Equations ◽  
Euler's Equations

AbstractIt is argued that bumps in the timing histories Ω(t) of the anomalous X-ray pulsars (AXPs) IE 1048.1-5937 and IE 2259+586 are the signature of a magnetar undergoing radiative precession, wherein the hydromagnetic deformation of the neutron star couples to an oscillating component of the vacuum-dipole radiation torque to produce an anharmonic wobble with periodτpr∼ 10 yr. An analysis of Euler’s equations of motion for a biaxial magnet reproduces the amplitude and recurrence time of the bumps for IE 1048.1-5937 and IE 2259+586, predicts Ω(t) for the next 20 years for both objects, and predicts a testable statistical relation betweendΩ/dtandτprfor the AXP population overall. Radiative precession of soft gamma-ray repeaters is also discussed, together with implications for the internal (e.g. viscosity) and magnetospheric (e.g.e+e−pair currents) properties of magnetars.

scholarly journals Aperiodic Flux Variability in A 0535+262

1996 ◽  
Vol 165 ◽  
pp. 313-319
Author(s):  
Mark H. Finger ◽  
Robert B. Wilson ◽  
B. Alan Harmon ◽  
William S. Paciesas
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Beat Frequency ◽  
Power Spectra ◽  
Center Frequency ◽  
X Ray ◽  
Binary Pulsar ◽  
Transient Source ◽  
Flux Variability ◽  
Burst And Transient Source

A “giant” outburst of A 0535+262, a transient X-ray binary pulsar, was observed in 1994 February and March with the Burst and Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory. During the outburst power spectra of the hard X-ray flux contained a QPO-like component with a FWHM of approximately 50% of its center frequency. Over the course of the outburst the center frequency rose smoothly from 35 mHz to 70 mHz and then fell to below 40 mHz. We compare this QPO frequency with the neutron star spin-up rate, and discuss the observed correlation in terms of the beat frequency and Keplerian frequency QPO models in conjunction with the Ghosh-Lamb accretion torque model.

scholarly journals Gravitational waves from mountains in newly born millisecond magnetars

2021 ◽  
Vol 502 (4) ◽  
pp. 4680-4688
Author(s):  
Ankan Sur ◽  
Brynmor Haskell
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Massive Star ◽  
Gamma Ray ◽  
Dipole Radiation ◽  
X Ray ◽  
Binary Neutron Star ◽  
Spin Period ◽  
Lower Maximum ◽  
Wave Emission

ABSTRACT In this paper, we study the spin-evolution and gravitational-wave luminosity of a newly born millisecond magnetar, formed either after the collapse of a massive star or after the merger of two neutron stars. In both cases, we consider the effect of fallback accretion; and consider the evolution of the system due to the different torques acting on the star, namely the spin-up torque due to accretion and spin-down torques due to magnetic dipole radiation, neutrino emission, and gravitational-wave emission linked to the formation of a ‘mountain’ on the accretion poles. Initially, the spin period is mostly affected by the dipole radiation, but at later times, accretion spin the star up rapidly. We find that a magnetar formed after the collapse of a massive star can accrete up to 1 M⊙, and survive on the order of 50 s before collapsing to a black hole. The gravitational-wave strain, for an object located at 1 Mpc, is hc ∼ 10−23 at kHz frequencies, making this a potential target for next-generation ground-based detectors. A magnetar formed after a binary neutron star merger, on the other hand, accretes at the most 0.2 M⊙ and emits gravitational waves with a lower maximum strain of the order of hc ∼ 10−24, but also survives for much longer times, and may possibly be associated with the X-ray plateau observed in the light curve of a number of short gamma-ray burst.

scholarly journals Interpreting the X-ray afterglows of gamma-ray bursts with radiative losses and millisecond magnetars

2020 ◽  
Vol 499 (4) ◽  
pp. 5986-5992
Author(s):  
Nikhil Sarin ◽  
Paul D Lasky ◽  
Gregory Ashton
Keyword(s):  
Gravitational Wave ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Dipole Radiation ◽  
X Ray ◽  
Radiative Efficiency ◽  
Central Engine ◽  
Radiative Losses ◽  
Wave Emission ◽  
Prompt Emission

ABSTRACT The spin-down energy of millisecond magnetars has been invoked to explain X-ray afterglow observations of a significant fraction of short and long gamma-ray bursts. Here, we extend models previously introduced in the literature, incorporating radiative losses with the spin-down of a magnetar central engine through an arbitrary braking index. Combining this with a model for the tail of the prompt emission, we show that our model can better explain the data than millisecond-magnetar models without radiative losses or those that invoke spin-down solely through vacuum dipole radiation. We find that our model predicts a subset of X-ray flares seen in some gamma-ray bursts. We can further explain the diversity of X-ray plateaus by altering the radiative efficiency and measure the braking index of newly born millisecond magnetars. We measure the braking index of GRB061121 as $n=4.85^{+0.11}_{-0.15}$ suggesting the millisecond-magnetar born in this gamma-ray burst spins down predominantly through gravitational-wave emission.

scholarly journals X-ray and Gamma-ray Radiation from the Switched-off Radiopulsars

1983 ◽  
Vol 101 ◽  
pp. 505-507
Author(s):  
A. I. Tsygan
Keyword(s):  
Neutron Stars ◽  
Magnetic Dipole ◽  
Gamma Ray ◽  
Neutral Hydrogen ◽  
Dipole Radiation ◽  
X Ray ◽  
Electron Positron ◽  
Hard Radiation ◽  
Γ Ray ◽  
Generate Electron

It is shown that pulsars that have ceased to generate electron-positron pairs (switched-off radiopulsars) may be the sources of X-ray and γ-ray radiation. The magnetic dipole radiation from these rotating neutron stars is transformed near the “light radius” into hard radiation by the plasma that is created due to ionization of interstellar neutral hydrogen.

scholarly journals Modes of Energy Loss from Isolated Magnetized Neutron Star

1987 ◽  
Vol 125 ◽  
pp. 450-450
Author(s):  
S. Shibata
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Gamma Ray ◽  
Rotational Energy ◽  
Pair Creation ◽  
Dipole Radiation ◽  
Pair Plasma ◽  
Electron Positron ◽  
Closed Current ◽  
Electron Positron Pair

Pulsar may be regarded as a discharge tube by electron-positron pair creation. On this viewpoint we carry out two numerical calculations. The obtained magnetic field is consistent with the flow. We find that pulsars emit their rotational energy through three modes simultaneously. The three modes are (1)relativistic acceleration and following gamma-ray emission in the closed current circuit in the magnetosphere, (2)wind of the electron-positron pair plasma, and (3)dipole radiation.

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.

The fate of accreted CNO elements in neutron star atmospheres - X-ray bursts and gamma-ray lines

1992 ◽  
Vol 384 ◽  
pp. 143 ◽  
Author(s):  
Lars Bildsten ◽  
Edwin E. Salpeter ◽  
Ira Wasserman
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
X Ray

Complete Six-Degrees-of-Freedom Nonlinear Ship Rolling Motion

1994 ◽  
Vol 116 (4) ◽  
pp. 191-201 ◽  
Author(s):  
M. Taz Ul Mulk ◽  
J. Falzarano
Keyword(s):  
Degrees Of Freedom ◽  
Second Harmonic ◽  
Equations Of Motion ◽  
Path Following ◽  
Euler Angle ◽  
Moment Curve ◽  
Six Degrees Of Freedom ◽  
Euler’S Equations ◽  
Euler's Equations ◽  
Asymmetric Nonlinearity

The emphasis of this paper is on nonlinear ship roll motion, because roll is the most critical ship motion of all six modes of motion. However, coupling between roll and the other modes of motion may be important and substantially affect the roll. Therefore, the complete six-degrees-of-freedom Euler’s equations of motion are studied. In previous work (Falzarano et al., 1990, 1991), roll linearly coupled to sway and yaw was studied. Continuing in this direction, this work extends that analysis to consider the dynamically more exact six-degrees-of-freedom Euler’s equations of motion and associated Euler angle kinematics. A combination of numerical path-following techniques and numerical integrations are utilized to study the steady-state response determined using this more exact modeling. The hydrodynamic forces are: linear frequency-dependent added-mass, damping, and wave-exciting, which are varied on a frequency-by-frequency basis. The linearized GM approximation to the roll-restoring moment is replaced with the nonlinear roll-restoring moment curve GZ(φ), and the linear roll wave damping is supplemented by an empirically derived linear and nonlinear viscous damping. A particularly interesting aspect of this modeling is the asymmetric nonlinearity associated with the heave and pitch hydrostatics. This asymmetric nonlinearity results in distinctive “dynamic bias,” i.e., a nonzero mean in heave and pitch time histories for a zero mean periodic forcing, and a substantial second harmonic. A Fourier analysis of the nonlinear response indicates that the harmonic response is similar to the linear motion response.

scholarly journals An approach to constrain models of accreting neutron stars with the use of an equation of state

2020 ◽  
Vol 2020 (3) ◽  
Author(s):  
Akira Dohi ◽  
Masa-aki Hashimoto ◽  
Rio Yamada ◽  
Yasuhide Matsuo ◽  
Masayuki Y Fujimoto
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Light Curve ◽  
Nuclear Energy ◽  
Evolution Equations ◽  
Energy Generation ◽  
Reaction Rates ◽  
Computational Time ◽  
Recurrence Time ◽  
X Ray

Abstract We investigate X-ray bursts during the thermal evolution of an accreting neutron star that corresponds to the X-ray burster GS 1826$-$24. Physical quantities of the neutron star are included using an equation of state below and above the nuclear matter density. We adopt an equation of state and construct an approximate network that saves computational time and calculates nuclear energy generation rates accompanying the abundance evolutions. The mass and radius of the neutron star are found by solving the stellar evolution equations from the center to the surface; this involves necessary information such as the nuclear energy generation in accreting layers, heating from the crust, and neutrino emissions inside the stellar core. We reproduce the light curve and recurrence time of the X-ray burst from GS 1826$-$24 within the standard deviation of 1$\sigma$ for the assumed accretion rate, metallicity, and equation of state. It is concluded that the observed recurrence time is consistent with the theoretical model with metallicity of the initial CNO elements $Z_{\rm CNO} = 0.01$. We suggest that the nuclear reaction rates responsible for the $rp$-process should be examined in detail, because the rates may change the shape of the light curve and our conclusion.

scholarly journals Discovery of a retrogradely rotating neutron star in the X-ray pulsar GX 301–2

2020 ◽  
Vol 494 (2) ◽  
pp. 2178-2182
Author(s):  
Juhani Mönkkönen ◽  
Victor Doroshenko ◽  
Sergey S Tsygankov ◽  
Armin Nabizadeh ◽  
Pavel Abolmasov ◽  
...  
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Orbital Motion ◽  
X Ray ◽  
Spin Evolution ◽  
Ultimate Result ◽  
Term Monitoring ◽  
Direction Opposite ◽  
Principal Possibility

ABSTRACT We report on the analysis of the spin evolution of a slow X-ray pulsar GX 301–2 along the orbit using long-term monitoring by Fermi/Gamma-ray Burst Monitor. Based on the observationally confirmed accretion scenario and an analytical model for the accretion of angular momentum, we demonstrate that in this system, the neutron star spins retrogradely, that is, in a direction opposite to the orbital motion. This first-of-a-kind discovery of such a system proves the principal possibility of retrograde rotation in accreting systems with suitable accretion torque, and might have profound consequences for our understanding of the spin evolution of X-ray pulsars, estimates of their initial spin periods, and the ultimate result of their evolution.

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