scholarly journals Single X-ray Bursts and the Model of a Spreading Layer of Accreting Matter over the Neutron Star Surface

2018 ◽  
Vol 44 (12) ◽  
pp. 777-781 ◽  
Author(s):  
S. A. Grebenev ◽  
I. V. Chelovekov
Keyword(s):  
Neutron Star ◽  
X Ray ◽  
Star Surface

scholarly journals Discovery of accretion-driven pulsations in the prolonged low X-ray luminosity state of the Be/X-ray transient GX 304–1

2018 ◽  
Vol 620 ◽  
pp. L13 ◽  
Author(s):  
A. Rouco Escorial ◽  
J. van den Eijnden ◽  
R. Wijnands
Keyword(s):  
Neutron Star ◽  
Stable State ◽  
Type I ◽  
X Ray ◽  
Monitoring Campaign ◽  
Spin Period ◽  
One Year ◽  
The Many ◽  
Low X ◽  
Star Surface

We present our Swift monitoring campaign of the slowly rotating neutron star Be/X-ray transient GX 304–1 (spin period of ∼275 s) when the source was not in outburst. We found that between its type I outbursts, the source recurrently exhibits a slowly decaying low-luminosity state (with luminosities of 1034 − 35 erg s−1). This behaviour is very similar to what has been observed for another slowly rotating system, GRO J1008–57. For that source, this low-luminosity state has been explained in terms of accretion from a non-ionised (“cold”) accretion disc. Because of the many similarities between the two systems, we suggest that GX 304–1 enters a similar accretion regime between its outbursts. The outburst activity of GX 304–1 ceased in 2016. Our continued monitoring campaign shows that the source is in a quasi-stable low-luminosity state (with luminosities a few factors lower than previously seen) for at least one year now. Using our NuSTAR observation in this state, we found pulsations at the spin period, demonstrating that the X-ray emission is due to accretion of matter onto the neutron star surface. If the accretion geometry during this quasi-stable state is the same as during the cold-disc state, then matter indeed reaches the surface (as predicted) during this later state. We discuss our results in the context of the cold-disc accretion model.

scholarly journals Einstein Observatory Limits on Neutron Star Surface Temperatures

1987 ◽  
Vol 125 ◽  
pp. 457-457
Author(s):  
F.R. Harnden
Keyword(s):  
Star Formation ◽  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Remnants ◽  
Theoretical Models ◽  
X Ray ◽  
Star Models ◽  
Formation And Evolution ◽  
Star Surface ◽  
Einstein Observatory

For years the theoretical models of neutron star formation and evolution had remained largely unconstrained by observation. Following the Einstein X-ray Observatory surveys of supernova remnants and pulsars, however, strict temperature limits were placed on many putative neutron stars. The Einstein search for additional objects in the class of supernova remnants with embedded pulsars has increased the number of such objects by two. For the four objects in this class, the surface temperature limits (see Table 1) provide meaningful logically sound constraints on the neutron star models. For the future, however, still better X-ray observations are needed, both to increase the number of objects available for study and to refine the spatial and spectral capabilities of the X-ray measurements.

scholarly journals The optical/UV excess of X-ray-dim isolated neutron star II. Nonuniformity of plasma on a strangeon star surface

2018 ◽  
Vol 18 (7) ◽  
pp. 082
Author(s):  
Wei-Yang Wang ◽  
Yi Feng ◽  
Xiao-Yu Lai ◽  
Yun-Yang Li ◽  
Ji-Guang Lu ◽  
...  
Keyword(s):  
Neutron Star ◽  
X Ray ◽  
Uv Excess ◽  
Star Surface

scholarly journals Timing of the accreting millisecond pulsar IGR J17591–2342: evidence of spin-down during accretion

2020 ◽  
Vol 495 (2) ◽  
pp. 1641-1649
Author(s):  
A Sanna ◽  
L Burderi ◽  
K C Gendreau ◽  
T Di Salvo ◽  
P S Ray ◽  
...  
Keyword(s):  
Neutron Star ◽  
Timing Analysis ◽  
Millisecond Pulsar ◽  
Pulse Profile ◽  
X Ray ◽  
Observed Behaviour ◽  
October 17 ◽  
Refined Estimate ◽  
Star Surface ◽  
Orbital Solution

ABSTRACT We report on the phase-coherent timing analysis of the accreting millisecond X-ray pulsar IGR J17591–2342, using Neutron Star Interior Composition Explorer (NICER) data taken during the outburst of the source between 2018 August 15 and 2018 October 17. We obtain an updated orbital solution of the binary system. We investigate the evolution of the neutron star spin frequency during the outburst, reporting a refined estimate of the spin frequency and the first estimate of the spin frequency derivative ($\dot{\nu }\sim -7\times 10^{-14}$ Hz s−1), confirmed independently from the modelling of the fundamental frequency and its first harmonic. We further investigate the evolution of the X-ray pulse phases adopting a physical model that accounts for the accretion material torque as well as the magnetic threading of the accretion disc in regions where the Keplerian velocity is slower than the magnetosphere velocity. From this analysis we estimate the neutron star magnetic field Beq = 2.8(3) × 108 G. Finally, we investigate the pulse profile dependence on energy finding that the observed behaviour of the pulse fractional amplitude and lags as a function of energy is compatible with the down-scattering of hard X-ray photons in the disc or the neutron star surface.

scholarly journals Determining the neutron star surface magnetic field strength of two Z sources

2012 ◽  
Vol 8 (S290) ◽  
pp. 203-204
Author(s):  
Guoqiang Ding ◽  
Chunping Huang ◽  
Yanan Wang
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Extreme Position ◽  
X Ray ◽  
Surface Magnetic Field ◽  
Axis Of Rotation ◽  
Star Surface ◽  
Z Sources

AbstractFrom the extreme position of disk motion, we infer the neutron star (NS) surface magnetic field strength (B0) of Z-source GX 17+2 and Cyg X-2. The inferred B0 of GX 17+2 and Cyg X-2 are ~(1–5)×108 G and ~(1–3)×108 G, respectively, which are not inferior to that of millisecond X-ray pulsars or atoll sources. It is likely that the NS magnetic axis of Z sources is parallel to the axis of rotation, which could result in the lack of pulsations in these sources.

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.

The Energy Dependence of Neutron Star Surface Modes and X‐Ray Burst Oscillations

2006 ◽  
Vol 638 (2) ◽  
pp. 968-973 ◽  
Author(s):  
Anthony L. Piro ◽  
Lars Bildsten
Keyword(s):  
Neutron Star ◽  
Energy Dependence ◽  
X Ray ◽  
Surface Modes ◽  
Star Surface

scholarly journals Multiwavelength observations of the Be-star/X-ray binary EXO2030+375 during outburst

1994 ◽  
Vol 162 ◽  
pp. 206-207
Author(s):  
A.J. Norton ◽  
M.J. Coe ◽  
C. Everall ◽  
P. Roche ◽  
L. Bildsten ◽  
...  
Keyword(s):  
Neutron Star ◽  
Emission Lines ◽  
Be Stars ◽  
Infrared Excess ◽  
X Ray ◽  
Circumstellar Material ◽  
Spin Period ◽  
Be Star ◽  
Star Surface ◽  
X Ray Binaries

EXO2030+375 consists of a neutron star in an eccentric 46 day orbit around a 20th magnitude Be-star companion (Coe et al., 1988; Parmar et al., 1989; Stollberg et al., 1993). The Be-star is thought to be surrounded by a shell/disc of material which is responsible for the infrared excess and Balmer emission lines which are characteristic of Be-stars in general. At periastron, the neutron star passes through this circumstellar material, giving rise to enhanced accretion onto the neutron star surface. As a result of this, the X-ray emission (pulsed at the neutron star spin period of 41.8s) increases dramatically, so producing the transient, outburst behaviour which is commonly seen in Be-star / X-ray binaries.

Asymmetric X-ray Pulsar Beam Emission

1986 ◽  
Vol 6 (4) ◽  
pp. 446-452 ◽  
Author(s):  
Whayne E. P. Padden ◽  
Michelle C. Storey
Keyword(s):  
Neutron Star ◽  
Magnetic Dipole ◽  
Accretion Rate ◽  
Rotation Period ◽  
Dipole Field ◽  
X Ray ◽  
Magnetic Dipole Field ◽  
Star Surface ◽  
Matter Transfer

AbstractMany of the X-ray pulsars for which X-ray lightcurves have been presented in the literature exhibit asymmetric emission beams. We postulate the existence of an off-centre magnetic dipole field embedded in the rotating neutron star and show that such a field leads to varying rates of matter transfer between an accretion dise and the neutron star surface, over a rotation period. Assuming that the accretion rate onto the surface is simply related to the luminosity, we show that most of the observed asymmetries can be accounted for by this mechanism.

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