scholarly journals Anomalous diffusion across a tera-Gauss magnetic field in accreting neutron stars

2020 ◽  
Vol 86 (6) ◽  
Author(s):  
Russell M. Kulsrud ◽  
Rashid Sunyaev
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Flux Distribution ◽  
Polar Regions ◽  
X Ray ◽  
Princeton University ◽  
Neutron Star Mass ◽  
Field Lines ◽  
Strong Ideal ◽  
The Magnetic Field

When mass falls on the polar regions of a neutron star in a binary X-ray source system, it tends to spread out over the entire surface. A long-standing question in research on this problem is: will the mass be anchored on the magnetic field lines and drag the field with it or is there a special mechanism that allows the mass to slip through the magnetic field lines, leading to much less distortion? As the amount of mass falling on the neutron star can actually be comparable with the neutron star mass, the question of which alternative holds is very important. We suggest an efficient mechanism that will allow the mass to slip through the lines. The mechanism is based on a strong ideal Schwarzschild (Structure and Evolution of the Stars. Princeton University Press, 1958) instability. As the instability itself is ideal, it cannot directly force the mass to slip though the lines. However, it can create a cascade of eddies whose scale extends down to a resistive scale, at the same time mixing the field lines up without breaking them. On this scale the mass can cross the lines. This instability is efficient enough that it can produce a mass flow in the plasma without growing to a large amplitude but saturates at a small one. The instability determines the mass per flux distribution of the accumulated material on different lines so that the equilibrium is marginal to the instability on every line. This makes the equilibrium unique. Thus, as the extra mass on the neutron star grows, the state of the outer shell proceeds through a sequence of unique critically unstable equilibria. In an appendix, an attempt is made to track the critical equilibria over long times.

scholarly journals Early neutron star evolution in high-mass X-ray binaries

2020 ◽  
Vol 494 (1) ◽  
pp. 44-49 ◽  
Author(s):  
Wynn C G Ho ◽  
M J P Wijngaarden ◽  
Nils Andersson ◽  
Thomas M Tauris ◽  
F Haberl
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Thermal Emission ◽  
Equilibrium Phase ◽  
High Mass ◽  
X Ray ◽  
Spin Period ◽  
Long Duration ◽  
X Ray Binaries ◽  
The Magnetic Field

ABSTRACT The application of standard accretion theory to observations of X-ray binaries provides valuable insights into neutron star (NS) properties, such as their spin period and magnetic field. However, most studies concentrate on relatively old systems, where the NS is in its late propeller, accretor, or nearly spin equilibrium phase. Here, we use an analytic model from standard accretion theory to illustrate the evolution of high-mass X-ray binaries (HMXBs) early in their life. We show that a young NS is unlikely to be an accretor because of the long duration of ejector and propeller phases. We apply the model to the recently discovered ∼4000 yr old HMXB XMMU J051342.6−672412 and find that the system’s NS, with a tentative spin period of 4.4 s, cannot be in the accretor phase and has a magnetic field B > a few × 1013 G, which is comparable to the magnetic field of many older HMXBs and is much higher than the spin equilibrium inferred value of a few × 1011 G. The observed X-ray luminosity could be the result of thermal emission from a young cooling magnetic NS or a small amount of accretion that can occur in the propeller phase.

scholarly journals Radiation Beaming in Pulsars

1971 ◽  
Vol 46 ◽  
pp. 455-456
Author(s):  
V. Canuto
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Coming Out ◽  
Critical Magnetic Field ◽  
Zero Field ◽  
Ordinary Wave ◽  
Magnetic Field Axis ◽  
Field Lines ◽  
Star Surface ◽  
The Magnetic Field

It is usually considered that the beaming of the radiation coming out of a pulsar has to be strictly connected with the mechanism producing the radiation itself. We want to show that even when the emitting mechanism gives rise to an isotropically distributed radiation, the presence of a strong magnetic field will automatically beam the radiation preferentially along the magnetic field line rather than in any other direction. We have computed the Compton scattering and from that the opacity KH (K0 is the opacity for zero field). In Figure 1 the ratio KH/K0 is given vs. θ, the angle between the propagation vector and the magnetic field axis. Hq is a critical magnetic field numerically equal to 4.41 × 1013 G; Ne is the electron density. For the ordinary wave the opacity is reduced at θ = 0, while it is unaffected at θ = π/2 where KH → K0. Even at θ = π/4 the ratio KH/K0 is still ≃ 10−2, and a good beaming is still present. The values of the parameters are proper for a neutron star surface. It is to be noticed that the ratio KH/K0 is of the order of (ω/ωH)2 or [(kT/mc2)/(H/Hq]2. One therefore can conclude that the presence of a magnetic field itself assures the beaming of radiation along the field lines.

The magnetic field of an isolated neutron star from X-ray cyclotron absorption lines

Nature ◽  
2003 ◽  
Vol 423 (6941) ◽  
pp. 725-727 ◽  
Author(s):  
G. F. Bignami ◽  
P. A. Caraveo ◽  
A. De Luca ◽  
S. Mereghetti
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Absorption Lines ◽  
X Ray ◽  
Cyclotron Absorption ◽  
The Magnetic Field

scholarly journals On Special Features of Non-Thermal Solar X Radiation above 10 keV

1972 ◽  
Vol 14 ◽  
pp. 761-762
Author(s):  
G. Elwert ◽  
E. Haug
Keyword(s):  
Magnetic Field ◽  
Angular Distribution ◽  
Power Law ◽  
Impulsive Phase ◽  
X Rays ◽  
Energetic Electrons ◽  
X Ray ◽  
Preferred Direction ◽  
Field Lines ◽  
The Magnetic Field

The polarization and angular distribution of solar hard X radiation above 10 keV was calculated under the assumption that the X rays originate as bremsstrahlung from energetic electrons moving in a preferred direction. The source electrons are supposed to have a power-law spectrum. These conditions are to be expected in the impulsive phase of an X-ray burst. The spiral orbits of the electrons around the magnetic field lines are taken into account.

scholarly journals Effect of Photon Rocket in X-ray Binaries

2000 ◽  
Vol 177 ◽  
pp. 653-654
Author(s):  
V. D. Pal’shin ◽  
A. I. Tsygan
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Gravitational Attraction ◽  
Dipolar Field ◽  
X Ray ◽  
The Galaxy ◽  
Star Surface ◽  
X Ray Binaries ◽  
The Magnetic Field

AbstractIt is shown that X-ray binaries can be accelerated by their own radiation. It is possible if the magnetic field of a neutron star in a binary differs from the dipolar field. Asymmetric X-ray emission generated due to accretion of matter onto a neutron star surface creates an accelerating force. Its magnitude can be comparable or even larger than gravitational attraction of the binary to the Galaxy.

scholarly journals Spin evolution of neutron stars in wind-fed high-mass X-ray binaries

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Shigeyuki Karino
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Neutron Stars ◽  
Wind Velocity ◽  
High Mass ◽  
Quasi Equilibrium ◽  
Pulse Period ◽  
X Ray ◽  
Spin Evolution ◽  
The Magnetic Field

Abstract The observed X-ray pulse period of OB-type high-mass X-ray binary (HMXB) pulsars is typically longer than 100 seconds. It is considered that the interaction between the strong magnetic field of a neutron star and the wind matter could cause such a long pulse period. In this study, we follow the spin evolution of neutron stars, taking into account the interaction between the magnetic field and wind matter. In this line, as new challenges, we solve the evolution of the magnetic field of the neutron star at the same time, and additionally we focus on the effects of the wind properties of the donor. As a result, evolutionary tracks were obtained in which the neutron star spends some duration in the ejector phase after birth, then rapidly spins down, becomes quasi-equilibrium, and gradually spins up. Such evolution is similar to previous studies, but we found that its dominant physics depends on the velocity of the donor wind. When the wind velocity is fast, the spin-down occurs due to magnetic inhibition, while the classical propeller effect and settling accretion shell causes rapid spin-down in the slow wind accretion. Since the wind velocity of the donor could depend on the irradiated X-ray luminosity, the spin evolution track of the neutron star in a wind-fed HMXB could be more complicated than considered.

scholarly journals On the role of rotation in the outflows of the Crab pulsar

2015 ◽  
Vol 24 (06) ◽  
pp. 1550042
Author(s):  
Gudavadze Irakli ◽  
Osmanov Zaza ◽  
Rogava Andria
Keyword(s):  
Magnetic Field ◽  
Rotation Axis ◽  
Three Dimensional ◽  
Rotating Magnetic Field ◽  
Crab Pulsar ◽  
X Ray ◽  
Field Lines ◽  
The Magnetic Field ◽  
Component Parallel

In order to study constraints imposed on kinematics of the Crab pulsar's jet, we consider motion of particles along co-rotating field lines in the magnetosphere of the Crab pulsar. It is shown that particles following the co-rotating magnetic field lines may attain velocities close to observable values. In particular, we demonstrate that if the magnetic field lines are within the light cylinder (LC), the maximum value of the velocity component parallel to the rotation axis is limited by 0.5c. This result in the context of the X-ray observations performed by Chandra X-ray Observatory seems to be quite indicative and useful to estimate the density of field lines inside the jet. Considering the three-dimensional (3D) field lines crossing the LC, we found that for explaining the force-free regime of outflows the magnetic field lines must asymptotically tend to the Archimedes spiral configuration. It is also shown that the 3D case may explain the observed jet velocity for appropriately chosen parameters of magnetic field lines.

scholarly journals Observations of GRO J1744–28 in quiescence with XMM-Newton

2020 ◽  
Vol 643 ◽  
pp. A62
Author(s):  
V. Doroshenko ◽  
V. Suleimanov ◽  
S. Tsygankov ◽  
J. Mönkkönen ◽  
L. Ji ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Binary System ◽  
Galactic Center ◽  
Optical Counterpart ◽  
X Ray ◽  
Upper Limit ◽  
Dipole Term ◽  
The Magnetic Field

We report on the deep observations of the “bursting pulsar” GRO J1744–28, which were performed with XMM-Newton and aimed to clarify the origin of its X-ray emission in quiescence. We detect the source at a luminosity level of ∼1034 erg s−1 with an X-ray spectrum that is consistent with the power law, blackbody, or accretion-heated neutron star atmosphere models. The improved X-ray localization of the source allowed us to confirm the previously identified candidate optical counterpart as a relatively massive G/K III star at 8 kpc close to the Galactic center, implying an almost face-on view of the binary system. Although we could only find a nonrestricting upper limit on the pulsed fraction of ∼20%, the observed hard X-ray spectrum and strong long-term variability of the X-ray flux suggest that the source is also still accreting when not in outburst. The luminosity corresponding to the onset of centrifugal inhibition of accretion is thus estimated to be at least two orders of magnitude lower than previously reported. We discuss this finding in the context of previous studies and argue that the results indicate a multipole structure in the magnetic field with the first dipole term of ∼1010 G, which is much lower than previously assumed.

scholarly journals Polar Gap Properties for Neutron StarWithin Light Cylinder Limits

2008 ◽  
Vol 5 (4) ◽  
pp. 612-618
Author(s):  
Baghdad Science Journal
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Magnetic Fields ◽  
Potential Drop ◽  
Stellar Surface ◽  
Physical Motion ◽  
Condensed Layer ◽  
Polar Gap ◽  
Field Lines ◽  
The Magnetic Field

The huge magnetic fields of neutron star cause the nuclei of the stellar surface to form a tightly bound condensed layer. In this research some characteristics of polar gap and magnetosphere enclosed the star according to Sturrock Model were illustrated, positrons move out along the open field lines, and electrons flow to the stellar surface as in the related to Sturrock model. The magnetic field within polar gap areas, which is defined by the Irvin Radius (RL) decreases due to the expansion of the polar, resulting from the physical motion of the accreted material. The values of height gap at different distances from the star were estimated. The obtained results improve the most energetic positrons those with E? Emax radiate away their energy in a distances re = 104m above the polar gap while less energetic positrons produced at much greater distances re =108m. The potential drop across the polar gap is obtained using a well defined adopted formula, it is found that the potential drop across the polar gap grows like (h2), when h « rp

scholarly journals First characterization of Swift J1845.7–0037 with NuSTAR

2020 ◽  
Vol 634 ◽  
pp. A89
Author(s):  
V. Doroshenko ◽  
S. Tsygankov ◽  
J. Long ◽  
A. Santangelo ◽  
S. Molkov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spectral Analysis ◽  
Neutron Star ◽  
X Ray ◽  
Transient Source ◽  
Broadband Spectrum ◽  
Cyclotron Line ◽  
The Magnetic Field

The hard X-ray transient source Swift J1845.7–0037 was discovered in 2012 by Swift/BAT. However, at that time, no dedicated observations of the source were performed. In October 2019, the source became active again, and X-ray pulsations with a period of ∼199 s were detected with Swift/XRT. This triggered follow-up observations with NuSTAR. Here, we report on the timing and spectral analysis of the source properties using NuSTAR and Swift/XRT. The main goal was to confirm pulsations and search for possible cyclotron lines in the broadband spectrum of the source to probe its magnetic field. Despite highly significant pulsations with period of 207.379(2) s being detected, no evidence for a cyclotron line was found in the spectrum of the source. We therefore discuss the strength of the magnetic field based on the source flux and the detection of the transition to the “cold-disc” accretion regime during the 2012 outburst. Our conclusion is that the source is most likely a highly magnetized neutron star with B ≳ 1013 G at a large distance of d ∼ 10 kpc. The latter is consistent with the nondetection of a cyclotron line in the NuSTAR energy band.

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