scholarly journals Kilohertz quasi-periodic oscillations as probes of the X-ray color-color diagram and neutron star accretion-disk structure for Z sources

2020 ◽  
Vol 642 ◽  
pp. A117
Author(s):  
De-Hua Wang ◽  
Cheng-Min Zhang ◽  
Jin-Lu Qu ◽  
Shu-Mei Jia
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Accretion Disk ◽  
Magnetic Energy ◽  
Mass Density ◽  
Periodic Oscillations ◽  
Disk Radius ◽  
X Ray ◽  
Disk Structure ◽  
Z Sources

Based on the detected kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low-mass X-ray binaries (NS-LMXBs), we investigate the evolution of the NS magnetosphere-disk structure along the Z track in the X-ray color-color diagram (CCD) for luminous Z sources, such as Cyg X-2, GX 5-1, GX 17+2, and Sco X-1. We find that the magnetosphere-disk radius r inferred by kHz QPOs for all the sources shows a monotonically decreasing trend along the Z track from the horizontal branch (HB) to the normal branch (NB), implying that the dominated radiation components may dramatically change as the accretion disk moves toward the NS surface. In addition, the specific radius that corresponds to the HB/NB vertex is found to be around r ∼ 20 km, implying a potential characteristic position of transiting for the X-ray radiation mode. Furthermore, we find that the NBs that occur near the NS surface have a radius of r ∼ 16−20 km, which is systematically smaller than those of HBs that have radii of r ∼ 20−29 km. To interpret the relation between the CCD properties and the special magnetosphere-disk radii of Z sources, we suggest that the magnetic field lines corresponding to NB are “frozen-in” to the plasma, and move further inward with the shrinking of the NS magnetosphere-disk radius and pile up near the NS surface. They then form a strong magnetic field region around r ∼ 16−20 km, where the high magnetic energy density and high plasma mass density may dominate the radiation process in NB.

scholarly journals The kHz QPOs as a probe of the X-ray color–color diagram and accretion-disk structure for the atoll source 4U 1728-34

2018 ◽  
Vol 618 ◽  
pp. A181 ◽  
Author(s):  
De-Hua Wang ◽  
Cheng-Min Zhang ◽  
Jin-Lu Qu
Keyword(s):  
Magnetic Field ◽  
Accretion Disk ◽  
Disk Radius ◽  
X Ray ◽  
Corotation Radius ◽  
Disk Structure ◽  
Radiation Distribution ◽  
Island State ◽  
The Magnetic Field ◽  
Radiation Transition

We have taken the kHz QPOs as a tool to probe the correlation between the tracks of X-ray color–color diagram (CCD) and magnetosphere-disk positions for the atoll source 4U 1728-34, based on the assumptions that the upper kHz QPO is ascribed to the Keplerian orbital motion and the neutron star (NS) magnetosphere is defined by the dipole magnetic field. We find that from the island to the banana state, the inner accretion disk gradually approaches the NS surface with the radius decreasing from r ∼ 33.0 km to ∼15.9 km, corresponding to the magnetic field from B(r) ∼ 4.8 × 106 G to ∼4.3 × 107 G. In addition, we note the characteristics of some particular radii of magnetosphere-disk r are: firstly, the whole atoll shape of the CCD links the disk radius range of ∼15.9–33.0 km, which is just located inside the corotation radius of 4U 1728-34 rco (∼34.4 km), implying that the CCD shape is involved in the NS spin-up state. Secondly, the island and banana states of CCD correspond to the two particular boundaries: (I)near the corotation radius at r ∼ 27.2–33.0 km, where the source lies in the island state; (II)near the NS surface at r ∼ 15.9–22.3 km, where the source lies in both the island and banana states. Thirdly, the vertex of the atoll shape in CCD, where the radiation transition from the hard to soft photons occurs, is found to be near the NS surface at r ∼ 16.4 km. The above results suggest that both the magnetic field and accretion environment are related to the CCD structure of atoll track, where the corotation radius and NS hard surface play the significant roles in the radiation distribution of atoll source.

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 Evidence for the radiation-pressure dominated accretion disk in bursting pulsar GRO J1744−28 using timing analysis

2019 ◽  
Vol 626 ◽  
pp. A106 ◽  
Author(s):  
Juhani Mönkkönen ◽  
Sergey S. Tsygankov ◽  
Alexander A. Mushtukov ◽  
Victor Doroshenko ◽  
Valery F. Suleimanov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Accretion Disk ◽  
Radiation Pressure ◽  
Compact Objects ◽  
Disk Radius ◽  
Line Energy ◽  
X Ray ◽  
Inner Radius ◽  
Cyclotron Line ◽  
The Magnetic Field

The X-ray pulsar GRO J1744−28 is a unique source that shows both pulsations and type-II X-ray bursts, allowing studies of the interaction of the accretion disk with the magnetosphere at huge mass-accretion rates exceeding 1019 g s−1 during its super-Eddington outbursts. The magnetic field strength in the source, B ≈ 5 × 1011 G, is known from the cyclotron absorption feature discovered in the energy spectrum around 4.5 keV. Here, we have explored the flux variability of the source in context of interaction of its magnetosphere with the radiation-pressure dominated accretion disk. Specifically, we present the results of the analysis of noise power density spectra (PDS) using the observations of the source in 1996–1997 by the Rossi X-ray Timing Explorer (RXTE). Accreting compact objects commonly exhibit a broken power-law PDS shape with a break corresponding to the Keplerian orbital frequency of matter at the innermost disk radius. The observed frequency of the break can thus be used to estimate the size of the magnetosphere. We find, however, that the observed PDS of GRO J1744−28 differs dramatically from the canonical shape. The observed break frequency appears to be significantly higher than expected based on the magnetic field estimated from the cyclotron line energy. We argue that these observational facts can be attributed to the existence of the radiation-pressure dominated region in the accretion disk at luminosities above ∼2 × 1037 erg s−1. We discuss a qualitative model for the PDS formation in such disks, and show that its predictions are consistent with our observational findings. The presence of the radiation-pressure dominated region can also explain the observed weak luminosity dependence of the inner radius, and we argue that the small inner radius can be explained by a quadrupole component dominating the magnetic field of the neutron star.

scholarly journals The kHz QPOs of Neutron Stars and Millisecond Pulsars and Implications

2012 ◽  
Vol 8 (S290) ◽  
pp. 381-385
Author(s):  
Chengmin Zhang ◽  
Dehua Wang
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Compact Objects ◽  
Periodic Oscillations ◽  
Disk Thickness ◽  
X Ray ◽  
Low Mass ◽  
Millisecond Timing ◽  
X Ray Binaries ◽  
Z Sources

AbstractThe kilohertz quasi-periodic oscillations (kHz QPOs) have been found in neutron star low mass X-ray binaries (NS-LMXBs), which present the millisecond timing phenomena close to the surface of the compact objects. We briefly summarize the following contents: (1). The correlations and distributions of twin kHz QPOs; (2). The relations of high-low frequency QPOs; (3). The QPO properties of NS Atoll and Z sources; (4). No clear direct correlations between NS spins and QPOs; (5). The mechanisms of kHz QPOs; (6). The implications of kHZ QPOs, e.g., NS mass and radius, disk thickness and magnetic field of Atoll and Z source.

AGN torus threaded by large scale magnetic field

2018 ◽  
Vol 27 (10) ◽  
pp. 1844006
Author(s):  
A. Dorodnitsyn ◽  
T. Kallman
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Accretion Disk ◽  
Large Scale ◽  
Three Dimensional ◽  
X Ray ◽  
Radiative Feedback ◽  
Large Scale Magnetic Field ◽  
Three Dimensional Simulations

Large scale magnetic field can be easily dragged from galactic scales toward AGN along with accreting gas. There, it can contribute to both the formation of AGN “torus” and help to remove angular momentum from the gas which fuels AGN accretion disk. However the dynamics of such gas is also strongly influenced by the radiative feedback from the inner accretion disk. Here we present results from the three-dimensional simulations of pc-scale accretion which is exposed to intense X-ray heating.

scholarly journals An Emission Line in the Hard X-Ray Spectrum of Hercules X-1: Quantized Cyclotron Emission from the Neutron Star

1977 ◽  
Vol 43 ◽  
pp. 34-34
Author(s):  
W. Pietsch ◽  
C. Reppin ◽  
R. Staubert ◽  
J. Truemper ◽  
W. Voges ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Field Strength ◽  
Second Harmonic ◽  
Narrow Line ◽  
Electron Cyclotron Emission ◽  
Polar Cap ◽  
Astrophysical Application ◽  
X Ray ◽  
Cyclotron Emission

A four hour balloon observation of HERC X-l during the 'On-state' in the 35 day cycle was performed on May 3rd, 1976. The 1.24 second pulsations show a pulsed fraction of 58 ± 8% in the 18-31 KeV interval. A pulsed flux (1.24 sec) was discovered in the 31-88 KeV interval with a pulsed fraction of 51 ± 14%. The spectrum of the pulsed flux can be represented up to 50 KeV by an exponential distribution with KT approximately 8 KeV. At approximately 58 KeV a strong and narrow line feature occurs which we interpret as electron cyclotron emission (ΔN = 1 Landau transition) from the polar cap plasma of the rotating neutron star. The corresponding magnetic field strength is approximately 5 x 1012 Gauss, neglecting gravitational red shift. There is evidence for a second harmonic at approximately 110 KeV (ΔN = 2 ).The astrophysical application of this discovery will be discussed in some detail.

Sign in / Sign up

Export Citation Format

Share Document