scholarly journals Revisiting the X-ray emission of the asynchronous polar V1432 Aql

2022 ◽  
Vol 21 (12) ◽  
pp. 315
Author(s):  
Qi-Shan Wang ◽  
Sheng-Bang Qian ◽  
Li-Ying Zhu
Keyword(s):  
Magnetic Field ◽  
Spectral Analysis ◽  
Accretion Rate ◽  
Wide Band ◽  
Reflection Effect ◽  
X Ray ◽  
Low Intensity ◽  
Strong Reflection ◽  
Orbital Modulation ◽  
The Magnetic Field

Abstract As the only eclipsing asynchronous polar, V1432 Aql provides an excellent laboratory to study the interaction between the accreted matter and the magnetic field. Here, we report an analysis of the X-ray data from the contemporaneous NuSTAR and Swift-XRT observations. The X-ray data present a profile with a low-intensity state for almost half an orbital period, a dip at 0.6 phase, and a peak at 0.75 phase, which suggests that there was only one accretion region during the observation and the claim is supported by the spectral analysis. The comparison with the previous data indicates that the X-ray data have an orbital modulation, as the case in BeppoSAX, rather than a spin one observed in ROSAT. We attribute the orbit and spin modulations to the different accretion geometries at work. The spectral analysis of the wide-band data presents a significant reflection effect, a commonly observed soft X-ray temperature, and the energy balance in V1432 Aql. Additionally, we obtained a low total accretion rate of 1.3 × 10−10 M ⊙ yr−1 and a high specific accretion rate of 3.8 g cm−2 s−1 which explains the strong reflection from the surface of the white dwarf. However, due to its complex emission, a more physical understanding of its accretion geometry is still outstanding.

scholarly journals Magnetic-reconnection-heated corona in active galactic nuclei: refined disc–corona model and application to broad-band radiation

2020 ◽  
Vol 495 (1) ◽  
pp. 1158-1171
Author(s):  
Huaqing Cheng ◽  
B F Liu ◽  
Jieying Liu ◽  
Zhu Liu ◽  
Erlin Qiao ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Accretion Rate ◽  
Broad Band ◽  
Limited Range ◽  
Relative Strength ◽  
Spectral Energy ◽  
X Ray ◽  
The Magnetic Field ◽  
Spectral Shapes

ABSTRACT A long-standing question in active galactic nucleus (AGN) research is how the corona is heated up to produce X-ray radiation much stronger than that arising from the viscous heating within the corona. In this paper, we carry out detailed investigations of magnetic-reconnection heating to the corona, specifically, studying how the disc and corona are self-consistently coupled with the magnetic field, and how the emergent spectra depend on the fundamental parameters of AGN. It is shown that diverse spectral shapes and luminosities over a broad bandpass from optical to X-ray can be produced from the coupled disc and corona within a limited range of the black hole mass, accretion rate, and magnetic field strength. The relative strength of X-ray emission with respect to optical/ultraviolet (UV) depends on the strength of the magnetic field in the disc, which, together with accretion rate, determines the fraction of accretion energy transported and released in the corona. This refined disc–corona model is then applied to reproduce the broad-band spectral energy distributions (SEDs) of a sample of 20 bright local AGNs observed simultaneously in X-ray and optical/UV. We find that, in general, the overall observed broad-band SEDs can be reasonably reproduced, except for rather hard X-ray spectral shapes in some objects. The radiation pressure-dominant region, as previously predicted for the standard accretion disc in AGN, disappears for strong X-ray sources, revealing that AGN accretion discs are indeed commonly stable as observed. Our study suggests the disc–corona coupling model involving magnetic fields to be a promising approach for understanding the broad-band spectra of bright AGNs.

scholarly journals Probability Distribution of Magnetic Field Strengths through the Cyclotron Lines in High-Mass X-ray Binaries

2020 ◽  
Vol 13 (3) ◽  
pp. 243-251
Keyword(s):  
Magnetic Field ◽  
Neutron Stars ◽  
Accretion Rate ◽  
High Mass ◽  
X Ray ◽  
Different Types ◽  
The Difference ◽  
Field Formation ◽  
X Ray Binaries ◽  
The Magnetic Field

Abstract: The study of variation of measured cyclotron lines is of fundamental importance to understand the physics of the accretion process in magnetized neutron star systems. We investigate the magnetic field formation, evolution and distribution for several High- Mass X-ray Binaries (HMXBs). We focus our attention on the cyclotron lines that have been detected in HMXB classes in their X-ray spectra. As has been correctly pointed out, several sources show variation in cyclotron lines, which can result due to the effect of accretion dynamics and hence that would reflect the magnetic field characteristics. Besides, the difference in time scales of variation of accretion rate and different types of companion can be used to distinguish between magnetized neutron stars. Keywords: Stars: neutron stars, High-Mass X-ray binaries, Stars: magnetic field, Cyclotron lines.

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.

scholarly journals X-Ray Emission from Cataclysmic Variables

1979 ◽  
Vol 53 ◽  
pp. 508-508
Author(s):  
D. Q. Lamb
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Classification Scheme ◽  
Accretion Rate ◽  
Cataclysmic Variables ◽  
X Rays ◽  
X Ray ◽  
Stellar Radius ◽  
The Magnetic Field

Many cataclysmic variables have been found to be hard, as well as soft, X-ray sources. Emission from the boundary layer of an optically thick accretion disk extending down to the stellar surface can, at outburst, produce soft X-rays, but the production of hard X-rays from such a disk is difficult to understand. We therefore conjecture that the sources which emit hard X-rays have magnetic fields and are, in general, rotating. We then propose a classification scheme for cataclysmic variables based on the size of the Alfven radius rA relative to the stellar radius R of the degenerate dwarf and the separation α of the binary system. We show that many of the varied characteristics displayed by the cataclysmic variable X-ray sources can be understood in terms of this ordering. We suggest that the AM Her Class (AM Her, AN UMa, W Pup, and 2A0311-23) have R ≪ α ≪ rA , the DQ Her Class (DQ Her, V533 Her, and AE Aqr) have R ≪ rA ≪ α, while the SS Cyg Class (SS Cyg, U Gem, EX Hya, and GK Per) have rA ≲ R ≪ α. Although rA depends on both the magnetic field strength of the degenerate dwarf ana the accretion rate, for comparable rates of accretion the ordering that we propose is essentially one of decreasing magnetic field strength.

scholarly journals The Magnetic Field of the Intermediate Polar RE 0751+14

1996 ◽  
Vol 158 ◽  
pp. 183-183
Author(s):  
H. Väth
Keyword(s):  
Magnetic Field ◽  
White Dwarf ◽  
Accretion Rate ◽  
Shock Structure ◽  
Light Curves ◽  
X Rays ◽  
Strong Magnetic Fields ◽  
X Ray ◽  
Spin Period ◽  
The Magnetic Field

Piirola, Hakala & Coyne (1993) modeled the optical/IR light curve of RE 0751+14 assuming a uniform shock structure and neglecting the hard X-ray emission. In this paper, we model the light curves at optical/IR and hard X-ray wavelengths and include the effects of the shock structure.We base our model on accretion onto a white dwarf with a displaced magnetic dipole for a range of likely white dwarf masses. We find that the observed intensity variations of X-rays and in the I band over one spin period largely determine the position of the emission regions. Furthermore, the observed maximum X-ray flux constrains the specific accretion rate. We deduce that the magnetic field at the pole is likely to be in the range 9 .. .21 MG, which is consistent with the estimates of Piirola et al. (1993). It had been proposed previously that there must exist asynchronous rotators with sufficiently strong magnetic fields such that the binaries will evolve into AM Her binaries (Chanmugam & Ray 1984; King, Frank & Ritter 1985). With this deduced high magnetic field RE 0751+14 is the most likely example of such a system known to date.

JET FORMATION IN MICROQUASARS AND ACTIVE GALACTIC NUCLEI: MAGNETIC FIELD LIMITS

2008 ◽  
Vol 17 (10) ◽  
pp. 1931-1937
Author(s):  
M. M. KAUFMAN BERNADÓ ◽  
M. MASSI
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Accretion Rate ◽  
Plasma Pressure ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Disk Material ◽  
The Magnetic Field

We introduce the use of a well-known parameter, the Alfvén Radius, R A , as a new tool to discern whether an X-ray binary system may undergo a microquasar phase, i.e. ejecting relativistic particles orthogonal to the accretion disk. We study what we call the basic condition, R A /R* = 1 in its dependency on the magnetic field strength and the mass accretion rate. With this basic condition we establish under which combination of parameters any class of accreting neutron stars could become a microquasar instead of confining disk-material down to the magnetic poles and creating the two emitting caps typical for an X-ray pulsar. In the case of black-hole accreting binaries we equate the magnetic field pressure to the plasma pressure in the last stable orbit (i.e. R A /R LSO = 1) and we get upper limits for the magnetic field strength as a function of the mass accretion rate and the black hole mass.

scholarly journals Enhanced X-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Evgeny D. Filippov ◽  
Sergey S. Makarov ◽  
Konstantin F. Burdonov ◽  
Weipeng Yao ◽  
Guilhem Revet ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic ◽  
Radiative Properties ◽  
Magnetic Field Direction ◽  
Solid Target ◽  
Total Plasma ◽  
Plasma Confinement ◽  
X Ray ◽  
Magnetic Compression ◽  
The Magnetic Field

AbstractWe analyze, using experiments and 3D MHD numerical simulations, the dynamic and radiative properties of a plasma ablated by a laser (1 ns, 10$$^{12}$$ 12 –10$$^{13}$$ 13 W/cm$$^2$$ 2 ) from a solid target as it expands into a homogeneous, strong magnetic field (up to 30 T) that is transverse to its main expansion axis. We find that as early as 2 ns after the start of the expansion, the plasma becomes constrained by the magnetic field. As the magnetic field strength is increased, more plasma is confined close to the target and is heated by magnetic compression. We also observe that after $$\sim 8$$ ∼ 8  ns, the plasma is being overall shaped in a slab, with the plasma being compressed perpendicularly to the magnetic field, and being extended along the magnetic field direction. This dense slab rapidly expands into vacuum; however, it contains only $$\sim 2\%$$ ∼ 2 % of the total plasma. As a result of the higher density and increased heating of the plasma confined against the laser-irradiated solid target, there is a net enhancement of the total X-ray emissivity induced by the magnetization.

How the Magnetic Field Impacts the Chiroptical Activities of Helical Copper Enantiomers

2021 ◽  
Author(s):  
jialu wu ◽  
Bo Li ◽  
Hong Wang ◽  
Ying Zhen Lai ◽  
Yue Ye ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solid State ◽  
Thermogravimetric Analysis ◽  
Single Crystal ◽  
Structure Analysis ◽  
Chiral Ligands ◽  
X Ray ◽  
The Magnetic Field

A pair of enantiomers {[Cu(L-pro)(L-tyr)]·2H2O}n (L-1) and {[Cu(D-pro)(D-tyr)]·2H2O}n (D-1) based on the chiral ligands L/D-proline and L/D-tyrosine were synthesized and investigated by single-crystal X-ray structure analysis, IR, thermogravimetric analysis, solid-state...

scholarly journals Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars

2008 ◽  
Vol 4 (S259) ◽  
pp. 395-396 ◽  
Author(s):  
Swetlana Hubrig ◽  
C. Grady ◽  
M. Schöller ◽  
O. Schütz ◽  
B. Stelzer ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Survey ◽  
Accretion Rate ◽  
Be Stars ◽  
General Correlation ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Debris Disk ◽  
Magnetic Nature

AbstractWe present the results of a new magnetic field survey of Herbig Ae/Be and A debris disk stars. They are used to determine whether magnetic field properties in these stars are correlated with the mass-accretion rate, disk inclinations, companion(s), Silicates, PAHs, or show a more general correlation with age and X-ray emission as expected for the decay of a remnant dynamo.

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