scholarly journals Re-assessment of the Accretion Disc Clock in Hercules X-1

2010 ◽  
Vol 6 (S277) ◽  
pp. 325-328 ◽  
Author(s):  
E. Jurua ◽  
M. Still ◽  
P. J. Meintjes ◽  
P. A. Charles ◽  
S. K Anguma
Keyword(s):  
Neutron Star ◽  
Energy Range ◽  
Accretion Disc ◽  
X Rays ◽  
X Ray ◽  
Broad Energy Range ◽  
Sky Monitor ◽  
Broad Energy

AbstractThe Galactic neutron star X-ray binary Her X-1 shows a 35-day photometric modulation. Detected across a broad energy range, the modulation is prevalent in X-rays, cycling between low and high states. Since the discovery of the 35-day cycle of Her X-1, the X-ray source has entered and returned from an extended anomalous low state on at least seven occasions. Employing Rossi X-ray Timing Explorer All-Sky Monitor observations, prior predictions that Her X-1 would return from the 2003 - 2004 anomalous low state with a new precession period and accretion luminosity are verified. However, the precession has not been as coherent over recent years as predicted. Potentially there have been more minor anomalous low states between 2004 and the present day.

scholarly journals Cygnus X-1: X-Ray Emission Mechanism and Geometry

1998 ◽  
Vol 188 ◽  
pp. 386-387
Author(s):  
Wei Cui ◽  
S. N. Zhang ◽  
J. H. Swank ◽  
X.-M. Hua ◽  
K. Ebisawa ◽  
...  
Keyword(s):  
Energy Range ◽  
Emission Mechanism ◽  
Spectral Variability ◽  
X Ray ◽  
Broad Energy Range ◽  
Soft State ◽  
Hard State ◽  
Sky Monitor ◽  
Broad Energy

On 1996 May 10, the All-Sky Monitor aboard RXTE revealed that Cyg X-1 started a transition from its hard state to soft state (Cui 1996). Throughout this interesting episode, snapshots were taken with more sensitive detectors on ASCA, RXTE, and CGRO to monitor the temporal and spectral variability of the source over a broad energy range.

scholarly journals NSLS-II MX beamlines FMX for micro-crystallography & AMX for highly automated MX

2014 ◽  
Vol 70 (a1) ◽  
pp. C1733-C1733
Author(s):  
Martin Fuchs ◽  
Robert Sweet ◽  
Lonny Berman ◽  
Dileep Bhogadi ◽  
Wayne Hendrickson ◽  
...  
Keyword(s):  
Energy Range ◽  
Structure Determination ◽  
Optical Systems ◽  
Photon Flux ◽  
X Rays ◽  
Macromolecular Crystallography ◽  
Binding Studies ◽  
X Ray ◽  
Array Detectors ◽  
Broad Energy Range

We present the final design of the x-ray optical systems and experimental stations of the two macromolecular crystallography (MX) beamlines, FMX and AMX, at the National Synchrotron Light Source-II (NSLS-II). Along with its companion x-ray scattering beamline, LIX, this suite of Advanced Beamlines for Biological Investigations with X-rays (ABBIX, [1]) will begin user operation in 2016. The pair of MX beamlines with complementary and overlapping capabilities is located at canted undulators (IVU21) in sector 17-ID. The Frontier Microfocusing Macromolecular Crystallography beamline (FMX) will deliver a photon flux of ~5x10^12 ph/s at a wavelength of 1 Å into a spot of 1 - 50 µm size. It will cover a broad energy range from 5 - 30 keV, corresponding to wavelengths from 0.4 - 2.5 Å. The highly Automated Macromolecular Crystallography beamline (AMX) will be optimized for high throughput applications, with beam sizes from 4 - 100 µm, an energy range of 5 - 18 keV (0.7 - 2.5 Å), and a flux at 1 Å of ~10^13 ph/s. Central components of the in-house-developed experimental stations are a 100 nm sphere of confusion goniometer with a horizontal axis, piezo-slits to provide dynamic beam size changes during diffraction experiments, a dedicated secondary goniometer for crystallization plates, and sample- and plate-changing robots. FMX and AMX will support a broad range of biomedical structure determination methods from serial crystallography on micron-sized crystals, to structure determination of complexes in large unit cells, to rapid sample screening and data collection of crystals in trays, for instance to characterize membrane protein crystals and to conduct ligand-binding studies. Together with the solution scattering program at LIX, the new beamlines will offer unique opportunities for advanced diffraction experiments with micro- and mini-beams, with next generation hybrid pixel array detectors and emerging crystal delivery methods such as acoustic droplet ejection. This work is supported by the US National Institutes of Health.

scholarly journals A von Hamos-type hard X-ray spectrometer at the PETRA III beamline P64

2020 ◽  
Vol 27 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Aleksandr Kalinko ◽  
Wolfgang A. Caliebe ◽  
Roland Schoch ◽  
Matthias Bauer
Keyword(s):  
High Resolution ◽  
Energy Range ◽  
Energy Resolution ◽  
Two Dimensional ◽  
Elastic Line ◽  
X Ray ◽  
Analyzer Crystal ◽  
Broad Energy Range ◽  
And Performance ◽  
Broad Energy

The design and performance of the high-resolution wavelength-dispersive multi-crystal von Hamos-type spectrometer at PETRA III beamline P64 are described. Extended analyzer crystal collection available at the beamline allows coverage of a broad energy range from 5 keV to 20 keV with an energy resolution of 0.35–1 eV. Particular attention was paid to enabling two-color measurements by a combination of two types of analyzer crystals and two two-dimensional detectors. The performance of the spectrometer is demonstrated by elastic-line and emission-line measurements on various compounds.

Investigation of pulsed X-ray radiation of a plasma focus in a broad energy range

2011 ◽  
Vol 37 (13) ◽  
pp. 1215-1218 ◽  
Author(s):  
A. S. Savelov ◽  
G. Kh. Salakhutdinov ◽  
M. V. Koltunov ◽  
B. D. Lemeshko ◽  
D. I. Yurkov ◽  
...  
Keyword(s):  
Energy Range ◽  
Plasma Focus ◽  
X Ray ◽  
Broad Energy Range ◽  
Broad Energy

scholarly journals Compton scattering for spectroscopic detection of ultra-fast, high flux, broad energy range X-rays

2013 ◽  
Vol 84 (11) ◽  
pp. 113302 ◽  
Author(s):  
S. Cipiccia ◽  
S. M. Wiggins ◽  
D. Maneuski ◽  
E. Brunetti ◽  
G. Vieux ◽  
...  
Keyword(s):  
Energy Range ◽  
Compton Scattering ◽  
High Flux ◽  
X Rays ◽  
Broad Energy Range ◽  
Broad Energy

Pockels readout optical modulator: An x‐ray imaging detector that maintains good efficiency over a broad energy range

1985 ◽  
Vol 56 (11) ◽  
pp. 2173-2175 ◽  
Author(s):  
Grant H. Stokes ◽  
David M. Stupin ◽  
Norman E. Elliott ◽  
Michael Graser
Keyword(s):  
Energy Range ◽  
Optical Modulator ◽  
Good Efficiency ◽  
X Ray ◽  
X Ray Imaging ◽  
Imaging Detector ◽  
Broad Energy Range ◽  
Broad Energy

scholarly journals X-ray Dips in AGN and Microquasars – Collapse Timescales of Inner Accretion Disc

2020 ◽  
Author(s):  
Mayur B Shende ◽  
Prashali Chauhan ◽  
Prasad Subramanian
Keyword(s):  
Collisionless Plasma ◽  
Cosmic Ray ◽  
Outer Radius ◽  
Accretion Disc ◽  
Accretion Discs ◽  
X Rays ◽  
Temporal Behaviour ◽  
X Ray ◽  
Ray Diffusion ◽  
3C 120

Abstract The temporal behaviour of X-rays from some AGN and microquasars is thought to arise from the rapid collapse of the hot, inner parts of their accretion discs. The collapse can occur over the radial infall timescale of the inner accretion disc. However, estimates of this timescale are hindered by a lack of knowledge of the operative viscosity in the collisionless plasma comprising the inner disc. We use published simulation results for cosmic ray diffusion through turbulent magnetic fields to arrive at a viscosity prescription appropriate to hot accretion discs. We construct simplified disc models using this viscosity prescription and estimate disc collapse timescales for 3C 120, 3C 111, and GRS 1915+105. The Shakura-Sunyaev α parameter resulting from our model ranges from 0.02 to 0.08. Our inner disc collapse timescale estimates agree well with those of the observed X-ray dips. We find that the collapse timescale is most sensitive to the outer radius of the hot accretion disc.

scholarly journals Compton-Thick AGN in the NuSTAR ERA VII. A joint NuSTAR, Chandra, and XMM-Newton Analysis of Two Nearby, Heavily Obscured Sources

2021 ◽  
Vol 922 (2) ◽  
pp. 159
Author(s):  
A. Traina ◽  
S. Marchesi ◽  
C. Vignali ◽  
N. Torres-Albà ◽  
M. Ajello ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Energy Range ◽  
Active Galactic Nuclei ◽  
Column Density ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Line Of Sight ◽  
Broad Energy Range ◽  
Larger Sample ◽  
Broad Energy

Abstract We present the joint Chandra, XMM-Newton, and NuSTAR analysis of two nearby Seyfert galaxies, NGC 3081 and ESO 565-G019. These are the only two having Chandra data in a larger sample of 10 low-redshift (z ≤ 0.05), candidates Compton-thick (CT) Active Galactic Nuclei selected in the 15–150 keV band with Swift-BAT that were still lacking NuSTAR data. Our spectral analysis, performed using physically motivated models, provides an estimate of both the line-of-sight (l.o.s.) and average (N H,S ) column densities of the two torii. NGC 3081 has a Compton-thin l.o.s. column density N H,z = [0.58–0.62] × 1024 cm−2, but the N H,S , beyond the CT threshold (N H,S = [1.41–1.78] × 1024 cm−2), suggests a “patchy” scenario for the distribution of the circumnuclear matter. ESO 565-G019 has both CT l.o.s. and N H,S column densities (N H,z > 2.31 × 1024 cm−2 and N H,S > 2.57 × 1024 cm−2, respectively). The use of physically motivated models, coupled with the broad energy range covered by the data (0.6–70 keV and 0.6–40 keV, for NGC 3081 and ESO 565-G019, respectively) allows us to constrain the covering factor of the obscuring material, which is C TOR = [0.63–0.82] for NGC 3081, and C TOR = [0.39–0.65] for ESO 565-G019.

scholarly journals Mass transfer on a nuclear timescale in models of supergiant and ultra-luminous X-ray binaries

2019 ◽  
Vol 628 ◽  
pp. A19 ◽  
Author(s):  
M. Quast ◽  
N. Langer ◽  
T. M. Tauris
Keyword(s):  
Mass Transfer ◽  
Black Hole ◽  
Neutron Star ◽  
Roche Lobe ◽  
High Mass ◽  
X Rays ◽  
X Ray ◽  
Mass Ratios ◽  
X Ray Binaries ◽  
Eddington Limit

Context. The origin and number of the Galactic supergiant X-ray binaries is currently not well understood. They consist of an evolved massive star and a neutron star or black-hole companion. X-rays are thought to be generated from the accretion of wind material donated by the supergiant, while mass transfer due to Roche-lobe overflow is mostly disregarded because the high mass ratios of these systems are thought to render this process unstable. Aims. We investigate how the proximity of supergiant donor stars to the Eddington limit, and their advanced evolutionary stage, may influence the evolution of massive and ultra-luminous X-ray binaries with supergiant donor stars (SGXBs and ULXs). Methods. We constructed models of massive stars with different internal hydrogen and helium gradients (H/He gradients) and different hydrogen-rich envelope masses, and exposed them to slow mass-loss to probe the response of the stellar radius. In addition, we computed the corresponding Roche-lobe overflow mass-transfer evolution with our detailed binary stellar evolution code, approximating the compact objects as point masses. Results. We find that a H/He gradient in the layers beneath the surface, as it is likely present in the well-studied donor stars of observed SGBXs, can enable mass transfer in SGXBs on a nuclear timescale with a black-hole or a neutron star accretor, even for mass ratios in excess of 20. In our binary evolution models, the donor stars rapidly decrease their thermal equilibrium radius and can therefore cope with the inevitably strong orbital contraction imposed by the high mass ratio. We find that the orbital period derivatives of our models agree well with empirical values. We argue that the SGXB phase may be preceded by a common-envelope evolution. The envelope inflation near the Eddington limit means that this mechanism more likely occurs at high metallicity. Conclusion. Our results open a new perspective for understanding that SGBXs are numerous in our Galaxy and are almost completely absent in the Small Magellanic Cloud. Our results may also offer a way to find more ULX systems, to detect mass transfer on nuclear timescales in ULX systems even with neutron star accretors, and shed new light on the origin of the strong B-field in these neutron stars.

Sign in / Sign up

Export Citation Format

Share Document