scholarly journals Polarization of accreting X-ray pulsars – II. Hercules X-1

2020 ◽  
Vol 501 (1) ◽  
pp. 129-136
Author(s):  
Ilaria Caiazzo ◽  
Jeremy Heyl
Keyword(s):  
Quantum Electrodynamics ◽  
Pulse Shape ◽  
Main Peak ◽  
Polarization Angle ◽  
X Ray ◽  
Structure And Dynamics ◽  
Cyclotron Line ◽  
Magnetic Poles ◽  
Energy Dependent ◽  
Polarization Fraction

ABSTRACT We employ our new model for the polarized emission of accreting X-ray pulsars to describe the emission from the luminous X-ray pulsar Hercules X-1. In contrast with previous works, our model predicts the polarization parameters independently of spectral formation, and considers the structure and dynamics of the accretion column, as well as the additional effects on propagation due to general relativity and quantum electrodynamics. We find that our model can describe the observed pulse fraction and the pulse shape of the main peak, as well as the modulation of the cyclotron line with phase. We pick two geometries, assuming a single accretion column or two columns at the magnetic poles, that can describe current observations of pulse shape and cyclotron modulation with phase. Both models predict a high polarization fraction, between 60 and 80 per cent in the 1–10 keV range, that is phase and energy dependent, and that peaks at the same phase as the intensity. The phase and energy dependence of the polarization fraction and of the polarization angle can help discern between the different geometries.

scholarly journals A Significant Detection of X-ray Polarization in Sco X-1 with PolarLight and Constraints on the Corona Geometry

2022 ◽  
Vol 924 (1) ◽  
pp. L13
Author(s):  
Xiangyun Long ◽  
Hua Feng ◽  
Hong Li ◽  
Jiahuan Zhu ◽  
Qiong Wu ◽  
...  
Keyword(s):  
Polarization Measurement ◽  
Polarization Angle ◽  
X Ray ◽  
Astrophysical Source ◽  
Accretion Rates ◽  
Measured Polarization ◽  
Low Mass ◽  
Marginal Detection ◽  
Energy Dependent ◽  
Polarization Fraction

Abstract We report the detection of X-ray polarization in the neutron-star low-mass X-ray binary Scorpius (Sco) X-1 with PolarLight. The result is energy-dependent, with a nondetection in 3–4 keV but a 4σ detection in 4–8 keV; it is also flux-dependent in the 4–8 keV band, with a nondetection when the source displays low fluxes but a 5σ detection during high fluxes, in which case we obtain a polarization fraction of 0.043 ± 0.008 and a polarization angle of 52.°6 ± 5.°4. This confirms a previous marginal detection with OSO-8 in the 1970s and marks Sco X-1 as the second astrophysical source with a significant polarization measurement in the keV band. The measured polarization angle is in line with the jet orientation of the source on the sky plane (54°), which is supposedly the symmetry axis of the system. Combining previous spectral analysis, our measurements suggest that an optically thin corona is located in the transition layer under the highest accretion rates, and disfavor the extended accretion disk corona model.

scholarly journals X-ray Spectroscopy of Thermally Emitting Neutron Stars

2004 ◽  
Vol 218 ◽  
pp. 283-286 ◽  
Author(s):  
M. H. van Kerkwijk
Keyword(s):  
Neutron Stars ◽  
Quantum Electrodynamics ◽  
Strong Field ◽  
Mode Conversion ◽  
X Ray ◽  
Surface Emission ◽  
Similar Temperature ◽  
Cyclotron Line ◽  
Absorption Features ◽  
Proton Cyclotron

I describe recent high-resolution X-ray spectroscopy of surface emission from nearby, thermally emitting neutron stars. I focus on RX J0720.4−3125, RX J1308.6+2127 and RX J1605.3+3249, all of which have similar temperature, but differ in the presence and strength of absorption features in their spectrA. I discuss possible causes for the absorption we see in two sources, and conclude that it may be proton cyclotron line absorption, but weakened due to the strong-field quantum electrodynamics effect of vacuum resonance mode conversion.

scholarly journals Broad-band X-ray characteristics of the transient pulsar GRO J2058+42

2020 ◽  
Vol 497 (1) ◽  
pp. 1059-1065
Author(s):  
Sanhita Kabiraj ◽  
Biswajit Paul
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Broad Band ◽  
High Energy ◽  
Energy Bands ◽  
X Ray ◽  
Energy Cutoff ◽  
Cyclotron Line ◽  
Energy Dependent

ABSTRACT The Be X-ray binary GRO J2058+42 recently went through a Type-II outburst during 2019 March–April lasting for about 50 d. This outburst was detected with the operating all sky X-ray monitors like the Fermi-GBM, Swift-BAT, and MAXI-GSC. Two Nuclear Spectroscopic Telescope Array(NuSTAR) observations were also made, one during the rise and other during the decay of the outburst. It gave us the unique opportunity to analyse the broad-band characteristics of the pulsar for the first time and accretion torque characteristics of the pulsar over a range of X-ray luminosity. The pulse profiles are strongly energy-dependent, with at least four different pulse components at low energy (< 20 keV), which evolves to a single-peaked profile at high energy (> 30 keV). In each of the narrow energy bands, the pulse profiles are nearly identical in the two NuSTAR observations. The spectra from both the observations are fitted well to a power-law with a Fermi–Dirac-type high-energy cutoff. We ruled out presence of a cyclotron line in the pulse phase averaged X-ray spectrum in the NuSTAR band with an optical depth greater than 0.15. An iron emission line is detected in both the NuSTAR spectra with an equivalent width of about 125 eV. We looked at the dependence of the spin-up rate on the luminosity and estimated the magnetic field strength from that, which came out to be much higher compared to other known BeXRB pulsars. Lastly, we discussed the inadequacy of the torque–luminosity relation for determination of magnetic field strength of neutron stars.

scholarly journals NuSTAR and XMM–Newton observations of SXP 59 during its 2017 giant outburst

2019 ◽  
Vol 489 (1) ◽  
pp. 1000-1005
Author(s):  
Shan-Shan Weng ◽  
Ming-Yu Ge ◽  
Hai-Hui Zhao
Keyword(s):  
Magnetic Field ◽  
Pulse Shape ◽  
The Other ◽  
Limited Data ◽  
High Luminosity ◽  
Thermal Component ◽  
X Ray ◽  
Spectral Models ◽  
Dipole Magnetic Field ◽  
Energy Dependent

ABSTRACT The Be X-ray pulsar (BeXRP) SXP 59 underwent a giant outburst in 2017 with a peak X-ray luminosity of 1.1 × 1038 erg s−1. We report on the X-ray behaviour of SXP 59 with the XMM–Newton and NuSTAR observations collected at the outburst peak, decay, and the low luminosity states. The pulse profiles are energy dependent, the pulse fraction increases with the photon energy and saturates at 65 per cent above 10 keV. It is difficult to constrain the change in the geometry of emitting region with the limited data. Nevertheless, because the pulse shape generally has a double-peaked profile at high luminosity and a single peak profile at low luminosity, we prefer the scenario that the source transited from the super-critical state to the sub-critical regime. This result would further imply that the neutron star (NS) in SXP 59 has a typical magnetic field. We confirm that the soft excess revealed below 2 keV is dominated by a cool thermal component. On the other hand, the NuSTAR spectra can be described as a combination of the non-thermal component from the accretion column, a hot blackbody emission, and an iron emission line. The temperature of the hot thermal component decreases with time, while its size remains constant (R ∼ 0.6 km). The existence of the hot blackbody at high luminosity cannot be explained with the present accretion theories for BeXRPs. It means that either more sophisticated spectral models are required to describe the X-ray spectra of luminous BeXRPs, or there is non-dipole magnetic field close to the NS surface.

SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

1981 ◽  
Vol 39 ◽  
pp. 198-199 ◽  
Author(s):  
R.F. Egerton
Keyword(s):  
Cross Sections ◽  
Fortran Program ◽  
Absorption Data ◽  
X Ray ◽  
Atomic Electrons ◽  
Energy Dependent ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

Energy-dependent dead-time correction in digital pulse processors applied to silicon drift detector's X-ray spectra

2018 ◽  
Vol 25 (2) ◽  
pp. 484-495 ◽  
Author(s):  
Suelen F. Barros ◽  
Vito R. Vanin ◽  
Alexandre A. Malafronte ◽  
Nora L. Maidana ◽  
Marcos N. Martins
Keyword(s):  
Dead Time ◽  
Pulse Height ◽  
Height Distribution ◽  
Pulse Height Distribution ◽  
Dead Time Correction ◽  
Time Model ◽  
X Ray ◽  
Digital Pulse ◽  
Analytical Correction ◽  
Energy Dependent

Dead-time effects in X-ray spectra taken with a digital pulse processor and a silicon drift detector were investigated when the number of events at the low-energy end of the spectrum was more than half of the total, at counting rates up to 56 kHz. It was found that dead-time losses in the spectra are energy dependent and an analytical correction for this effect, which takes into account pulse pile-up, is proposed. This and the usual models have been applied to experimental measurements, evaluating the dead-time fraction either from the calculations or using the value given by the detector acquisition system. The energy-dependent dead-time model proposed fits accurately the experimental energy spectra in the range of counting rates explored in this work. A selection chart of the simplest mathematical model able to correct the pulse-height distribution according to counting rate and energy spectrum characteristics is included.

scholarly journals Local Structure and Dynamics of Functional Materials Studied by X-ray Absorption Fine Structure

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1315
Author(s):  
Takafumi Miyanaga
Keyword(s):  
Fine Structure ◽  
Local Structure ◽  
Chemical Reactivity ◽  
Functional Materials ◽  
X Ray ◽  
Structure And Dynamics ◽  
Absorption Fine ◽  
Structure Phase Transition ◽  
Local Electronic Structure ◽  
X Ray Absorption

X-ray absorption fine structure (XAFS) is a powerful technique used to analyze a local electronic structure, local atomic structure, and structural dynamics. In this review, I present examples of XAFS that apply to the local structure and dynamics of functional materials: (1) structure phase transition in perovskite PbTiO3 and magnetic FeRhPd alloys; (2) nano-scaled fluctuations related to their magnetic properties in Ni–Mn alloys and Fe/Cr thin films; and (3) the Debye–Waller factors related to the chemical reactivity for catalysis in polyanions and ligand exchange reaction. This study shows that the local structure and dynamics are related to the characteristic function of the materials.

Structure and dynamics of 1,4-dioxane-water binary solutions studied by X-ray diffraction, mass spectrometry, and NMR relaxation

1999 ◽  
Vol 83 (1-3) ◽  
pp. 163-177 ◽  
Author(s):  
Toshiyuki Takamuku ◽  
Atsushi Yamaguchi ◽  
Masaaki Tabata ◽  
Nobuyuki Nishi ◽  
Koji Yoshida ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Nmr Relaxation ◽  
X Ray Diffraction ◽  
Binary Solutions ◽  
X Ray ◽  
Structure And Dynamics

scholarly journals Performance and optimization of X-ray grating interferometry

2014 ◽  
Vol 372 (2010) ◽  
pp. 20130027 ◽  
Author(s):  
T. Thuering ◽  
M. Stampanoni
Keyword(s):  
Interference Fringe ◽  
Refraction Angle ◽  
Fringe Visibility ◽  
X Ray ◽  
Analytical Formulae ◽  
Grating Interferometer ◽  
Differential Phase Contrast ◽  
Energy Dependent ◽  
Application Specific ◽  
Contrast Image

The monochromatic and polychromatic performance of a grating interferometer is theoretically analysed. The smallest detectable refraction angle is used as a metric for the efficiency in acquiring a differential phase-contrast image. Analytical formulae for the visibility and the smallest detectable refraction angle are derived for Talbot-type and Talbot–Lau-type interferometers, respectively, providing a framework for the optimization of the geometry. The polychromatic performance of a grating interferometer is investigated analytically by calculating the energy-dependent interference fringe visibility, the spectral acceptance and the polychromatic interference fringe visibility. The optimization of grating interferometry is a crucial step for the design of application-specific systems with maximum performance.

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