Investigation of the Timing and Spectral Properties of an Ultraluminous X-Ray Pulsar NGC 7793 P13

Abstract We perform both timing and spectral analyses using the archival X-ray data taken with Swift, XMM-Newton, NICER, and NuSTAR from 2016 to 2020 to study an ultraluminous pulsar, NGC 7793 P13, that showed a long period of super-Eddington accretion. We use the Rayleigh test to investigate the pulsation at different epochs, and confirm the variation of the pulse profile with finite Gaussian mixture modeling and a two-sample Kuiper test. Taking into account the periodic variation of the spin periods caused by the orbital Doppler effect, we further determine an orbital period of ∼65 days and show that no significant correlation can be detected between the orbital phase and the pulsed fraction. The pulsed spectrum of NGC 7793 P13 in the 0.5–20 keV range can be simply described using a power law with a high-energy exponential cutoff, while the broadband phase-averaged spectrum of the same energy range requires two additional components to account for the contribution of a thermal accretion disk and the Comptonization photons scattered into the hard X-rays. We find that NGC 7793 P13 stayed in the hard ultraluminous state and the pulsed spectrum was relatively soft when the source was faint at the end of 2019. Moreover, an absorption feature close to 1.3 keV is marginally detected from the pulsed spectra and it is possibly associated with a cyclotron resonant scattering feature.

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New measurements of the cyclotron line energy in Cen X-3

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3477 ◽

2020 ◽

Vol 500 (3) ◽

pp. 3454-3461

Author(s):

Gunjan Tomar ◽

Pragati Pradhan ◽

Biswajit Paul

Keyword(s):

Broad Band ◽

Resonant Scattering ◽

High Energy ◽

Emission Lines ◽

Power Law Model ◽

Pulse Profile ◽

Line Energy ◽

X Ray ◽

Cyclotron Absorption ◽

Cyclotron Line

ABSTRACT We report results from the analysis of data from two observations of the accreting binary X-ray pulsar Cen X-3 carried out with the broad-band X-ray observatories Suzaku and NuSTAR. The pulse profile is dominated by a broad single peak and show some energy dependence with two additional weak pulse peaks at energies below 15 and 25 keV, respectively. The broad-band X-ray spectrum for 0.8–60.0 keV for Suzaku and 3.0–60.0 keV for NuSTAR is fitted well with high-energy cut-off power-law model along with soft-excess, multiple iron emission lines and a cyclotron absorption. The cyclotron line energy is found to be $30.29^{+0.68}_{-0.61}$ and $29.22^{+0.28}_{-0.27}$ keV, respectively, in the Suzaku and NuSTAR spectra. We make a comparison of these two measurements with four previous measurements of Cyclotron Resonant Scattering Feature (CRSF) in Cen X-3 obtained with Ginga, BeppoSAX, and RXTE. We find no evidence for a dependence of the CRSF on luminosity. Except for one CRSF measurement with BeppoSAX , the remaining measurements are consistent with a CRSF energy in the range of 29.5–30.0 keV over a luminosity range of 1.1–5.4 × 1037 erg s−1 different from several other sources that show considerable CRSF variation in the same luminosity range.

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Revisiting the spectral and timing properties of 4U 1909+07 with NuSTAR and Astrosat

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2604 ◽

2020 ◽

Vol 498 (4) ◽

pp. 4830-4838 ◽

Cited By ~ 1

Author(s):

Gaurava K Jaisawal ◽

Sachindra Naik ◽

Wynn C G Ho ◽

Neeraj Kumari ◽

Prahlad Epili ◽

...

Keyword(s):

Broad Band ◽

High Energy ◽

High Mass ◽

X Rays ◽

Pulse Profile ◽

X Ray ◽

Beam Geometry ◽

Cyclotron Absorption ◽

Using Data ◽

Wind Distribution

ABSTRACT We present the results obtained from the analysis of high-mass X-ray binary pulsar 4U 1909+07 using NuSTAR and Astrosat observations in July 2015 and 2017, respectively. X-ray pulsations at ≈604 s are clearly detected in our study. Based on the long-term spin-frequency evolution, the source is found to spun-up in the last 17 yr. We observed a strongly energy-dependent pulse profile that evolved from a complex broad structure in soft X-rays into a profile with a narrow emission peak followed by a plateau in energy ranges above 20 keV. This behaviour ensured a positive correlation between the energy and pulse fraction. The pulse profile morphology and its energy evolution are almost similar during both the observations, suggesting a persistent emission geometry of the pulsar over time. The broad-band energy spectrum of the pulsar is approximated by an absorbed high-energy exponential cut-off power-law model with iron emission lines. In contrast to the previous report, we found no statistical evidence for the presence of cyclotron absorption features in the X-ray spectra. We performed phase-resolved spectroscopy using data from the NuSTAR observation. Our results showed a clear signature of absorbing material at certain pulse phases of the pulsar. These findings are discussed in terms of stellar wind distribution and its effect on the beam geometry of this wind-fed accreting neutron star. We also reviewed the subsonic quasi-spherical accretion theory and its implication on the magnetic field of 4U 1909+07 depending on the global spin-up rate.

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Spectrum formation in X-ray pulsars at very low mass accretion rate: Monte Carlo approach

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab811 ◽

2021 ◽

Vol 503 (4) ◽

pp. 5193-5203

Author(s):

Alexander A Mushtukov ◽

Valery F Suleimanov ◽

Sergey S Tsygankov ◽

Simon Portegies Zwart

Keyword(s):

Monte Carlo ◽

Neutron Star ◽

Spectral Characteristics ◽

Electron Gas ◽

High Energy ◽

Spectral Shape ◽

Absorption Feature ◽

X Rays ◽

Component Structure ◽

X Ray

ABSTRACT Recently, it has been discovered that the transition of X-ray pulsars to the low luminosity state ($L\lesssim 10^{35}\, {\rm erg\ \rm s^{-1}}$) is accompanied by a dramatic spectral change. That is, the typical power-law-like spectrum with high-energy cut-off transforms into a two-component structure with a possible cyclotron absorption feature on top of it. It was proposed that these spectral characteristics can be explained qualitatively by the emission of cyclotron photons in the atmosphere of the neutron star caused by collisional excitation of electrons to upper Landau levels and further Comptonization of the photons by electron gas. The electron gas are expected to be overheated in a thin top layer of the atmosphere. In this paper, we perform Monte Carlo simulations of the radiative transfer in the atmosphere of an accreting neutron star while accounting for a resonant scattering of polarized X-ray photons by thermally distributed electrons. The spectral shape is shown to be strongly polarization-dependent in soft X-rays ($\lesssim 10\, {\rm keV}$) and near the cyclotron scattering feature. The results of our numerical simulations are tested against the observational data of the X-ray pulsar A 0535+262 in the low-luminosity state. We show that the spectral shape of the pulsar can be reproduced by the proposed theoretical model. We discuss applications of the discovery to the observational studies of accreting neutron stars.

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The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117777 ◽

1985 ◽

Vol 43 ◽

pp. 154-157

Author(s):

A.J. Tousimis

Keyword(s):

Ion Beam ◽

Depth Resolution ◽

Sample Surface ◽

High Energy ◽

X Rays ◽

X Ray ◽

Electrons And Ions ◽

Spatial Depth ◽

Minimum Surface Area ◽

Physical Principles

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.

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Demonstration of Geometric Effects and Resonant Scattering in the X-Ray Spectra of High-Energy-Density Plasmas

Physical Review Letters ◽

10.1103/physrevlett.126.085001 ◽

2021 ◽

Vol 126 (8) ◽

Author(s):

G. Pérez-Callejo ◽

E. V. Marley ◽

D. A. Liedahl ◽

L. C. Jarrott ◽

G. E. Kemp ◽

...

Keyword(s):

Energy Density ◽

Resonant Scattering ◽

High Energy ◽

High Energy Density ◽

X Ray ◽

High Energy Density Plasmas ◽

Geometric Effects

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A multi-length-scale USAXS/SAXS facility: 10–50 keV small-angle X-ray scattering instrument

Journal of Applied Crystallography ◽

10.1107/s0021889813021900 ◽

2013 ◽

Vol 46 (5) ◽

pp. 1508-1512 ◽

Cited By ~ 11

Author(s):

Byron Freelon ◽

Kamlesh Suthar ◽

Jan Ilavsky

Keyword(s):

Small Angle ◽

Soft Matter ◽

High Energy ◽

X Rays ◽

X Ray ◽

X Ray Scattering ◽

Wide Range ◽

And Performance ◽

New Facility ◽

Ray Scattering

Coupling small-angle X-ray scattering (SAXS) and ultra-small-angle X-ray scattering (USAXS) provides a powerful system of techniques for determining the structural organization of nanostructured materials that exhibit a wide range of characteristic length scales. A new facility that combines high-energy (HE) SAXS and USAXS has been developed at the Advanced Photon Source (APS). The application of X-rays across a range of energies, from 10 to 50 keV, offers opportunities to probe structural behavior at the nano- and microscale. An X-ray setup that can characterize both soft matter or hard matter and high-Zsamples in the solid or solution forms is described. Recent upgrades to the Sector 15ID beamline allow an extension of the X-ray energy range and improved beam intensity. The function and performance of the dedicated USAXS/HE-SAXS ChemMatCARS-APS facility is described.

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A high-energy triple-axis X-ray diffractometer for the study of the structure of bulk crystals

Journal of Applied Crystallography ◽

10.1107/s0021889804023805 ◽

2004 ◽

Vol 37 (6) ◽

pp. 901-910 ◽

Cited By ~ 6

Author(s):

C. Seitz ◽

M. Weisser ◽

M. Gomm ◽

R. Hock ◽

A. Magerl

Keyword(s):

High Energy ◽

X Rays ◽

Bulk Crystals ◽

X Ray Diffraction ◽

X Ray ◽

Peak Intensity ◽

High Penetration ◽

Massive Sample ◽

Laue Geometry ◽

The Ideal

A triple-axis diffractometer for high-energy X-ray diffraction is described. A 450 kV/4.5 kW stationary tungsten X-ray tube serves as the X-ray source. Normally, 220 reflections of thermally annealed Czochralski Si are employed for the monochromator and analyser. Their integrated reflectivity is about ten times higher than the ideal crystal value. With the same material as the sample, and working with the WKα line at 60 keV in symmetric Laue geometry for all axes, the full width at half-maximum (FWHM) values for the longitudinal and transversal resolution are 2.5 × 10−3and 1.1 × 10−4for ΔQ/Q, respectively, and the peak intensity for a non-dispersive setting is 3000 counts s−1. In particular, for a double-axis mode, an energy well above 100 keV from theBremsstrahlungspectrum can be used readily. High-energy X-rays are distinguished by a high penetration power and materials of several centimetre thickness can be analysed. The feasibility of performing experiments with massive sample environments is demonstrated.

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Development of Si-APD Timing Detectors for Nuclear Resonant Scattering using High-energy Synchrotron X-rays

10.1063/1.2436267 ◽

2007 ◽

Author(s):

Shunji Kishimoto ◽

Zhang Xiaowei ◽

Yoshitaka Yoda

Keyword(s):

Resonant Scattering ◽

High Energy ◽

Nuclear Resonant Scattering ◽

X Rays

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X-ray spectra and light curves of cooling novae and a nova like

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3012 ◽

2020 ◽

Vol 499 (2) ◽

pp. 3006-3018

Author(s):

Bangzheng Sun ◽

Marina Orio ◽

Andrej Dobrotka ◽

Gerardo Juan Manuel Luna ◽

Sergey Shugarov ◽

...

Keyword(s):

Light Curve ◽

Accretion Rate ◽

High Energy ◽

Gravitational Energy ◽

Light Curves ◽

Clear Correlation ◽

X Rays ◽

High State ◽

X Ray ◽

Low X

ABSTRACT We present X-ray observations of novae V2491 Cyg and KT Eri about 9 yr post-outburst of the dwarf nova and post-nova candidate EY Cyg, and of a VY Scl variable. The first three objects were observed with XMM–Newton, KT Eri also with the Chandra ACIS-S camera, V794 Aql with the Chandra ACIS-S camera and High Energy Transmission Gratings. The two recent novae, similar in outburst amplitude and light curve, appear very different at quiescence. Assuming half of the gravitational energy is irradiated in X-rays, V2491 Cyg is accreting at $\dot{m}=1.4\times 10^{-9}{\!-\!}10^{-8}\,{\rm M}_\odot \,{\rm yr}^{-1}$, while for KT Eri, $\dot{m}\lt 2\times 10^{-10}{\rm M}_\odot \,{\rm yr}$. V2491 Cyg shows signatures of a magnetized WD, specifically of an intermediate polar. A periodicity of 39 min, detected in outburst, was still measured and is likely due to WD rotation. EY Cyg is accreting at $\dot{m}\sim 1.8\times 10^{-11}{\rm M}_\odot \,{\rm yr}^{-1}$, one magnitude lower than KT Eri, consistently with its U Gem outburst behaviour and its quiescent UV flux. The X-rays are modulated with the orbital period, despite the system’s low inclination, probably due to the X-ray flux of the secondary. A period of 81 min is also detected, suggesting that it may also be an intermediate polar. V794 Aql had low X-ray luminosity during an optically high state, about the same level as in a recent optically low state. Thus, we find no clear correlation between optical and X-ray luminosity: the accretion rate seems unstable and variable. The very hard X-ray spectrum indicates a massive WD.

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