In Search of X-rays from Uranus

2020 ◽  
Author(s):  
William Dunn ◽  
Jan-Uwe Ness ◽  
Laurent Lamy ◽  
Grant Tremblay ◽  
Graziella Branduard-Raymont ◽  
...  
Keyword(s):  
High Resolution ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Field Of View ◽  
X Rays ◽  
Imaging Spectrometer ◽  
Ccd Imaging ◽  
X Ray ◽  
Upper Limits ◽  
Photon Energy Distribution

<p>Within the solar system, X-ray emissions have been detected from every planet except the Ice Giants: Uranus and Neptune. Here, we present three Chandra X-ray Observations of Uranus (each 24-30 ks duration): an Advanced CCD Imaging Spectrometer (ACIS) observation during solar maximum on 7 August 2002 and two High Resolution Camera (HRC) observations during solar minimum on 11 and 12 November 2017. The ACIS observation from 2002 shows a low signal but statistically significant detection of X-rays from Uranus. The measured Uranus X-ray fluxes of 10<sup>-15</sup>-10<sup>-16 </sup>erg/cm<sup>2</sup>/s from this detection are consistent with upper limits and modelling predictions in previous work (Ness & Schmidt. 2000; Cravens et al. 2006).  The photon energy distribution from this observation is consistent with an X-ray emission from charge exchange or scattering of solar photons, as observed for Jupiter and Saturn. The two HRC observations from 2017 constitute non-detections. For 11 Nov 2017, the X-ray emission coincident with Uranus’ location is dimmer than 98% of the Field of View. 12 November 2017, was also a non-detection, but with tentative hints of planetary X-ray signatures: Uranus was 4 times brighter than the previous day, and brighter than 94% of the Field of View (1.6 standard deviations > Field of View mean). At this time, the Uranus coincident X-ray signature also exhibited timing variation distinct from the field of view. Further and longer observations will be required to better characterise the nature of the X-ray emissions from Uranus.</p>

scholarly journals Long-term X-ray variability of the symbiotic system RT Cru based on Chandra spectroscopy

2020 ◽  
Vol 500 (4) ◽  
pp. 4801-4817
Author(s):  
A Danehkar ◽  
M Karovska ◽  
J J Drake ◽  
V L Kashyap
Keyword(s):  
High Resolution ◽  
Thermal Plasma ◽  
High Energy ◽  
Accretion Disc ◽  
Energy Transmission ◽  
Imaging Spectrometer ◽  
Ccd Imaging ◽  
X Ray ◽  
Transmission Grating ◽  
Absorbing Material

ABSTRACT RT Cru belongs to the rare class of hard X-ray emitting symbiotics, whose origin is not yet fully understood. In this work, we have conducted a detailed spectroscopic analysis of X-ray emission from RT Cru based on observations taken by the Chandra Observatory using the Low Energy Transmission Grating (LETG) on the High-Resolution Camera Spectrometer (HRC-S) in 2015 and the High Energy Transmission Grating (HETG) on the Advanced CCD Imaging Spectrometer S-array (ACIS-S) in 2005. Our thermal plasma modelling of the time-averaged HRC-S/LETG spectrum suggests a mean temperature of kT ∼ 1.3 keV, whereas kT ∼ 9.6 keV according to the time-averaged ACIS-S/HETG. The soft thermal plasma emission component (∼1.3 keV) found in the HRC-S is heavily obscured by dense materials (>5 × 1023 cm−2). The aperiodic variability seen in its light curves could be due to changes in either absorbing material covering the hard X-ray source or intrinsic emission mechanism in the inner layers of the accretion disc. To understand the variability, we extracted the spectra in the ‘low/hard’ and ‘high/soft’ spectral states, which indicated higher plasma temperatures in the low/hard states of both the ACIS-S and HRC-S. The source also has a fluorescent iron emission line at 6.4 keV, likely emitted from reflection off an accretion disc or dense absorber, which was twice as bright in the HRC-S epoch compared to the ACIS-S. The soft thermal component identified in the HRC-S might be an indication of a jet that deserves further evaluations using high-resolution imaging observations.

scholarly journals To be or not to be: the case of the hot WHIM absorption in the blazar PKS 2155–304 sight line

2019 ◽  
Vol 621 ◽  
pp. A88 ◽  
Author(s):  
J. Nevalainen ◽  
E. Tempel ◽  
J. Ahoranta ◽  
L. J. Liivamägi ◽  
M. Bonamente ◽  
...  
Keyword(s):  
Absorption Line ◽  
Imaging Spectrometer ◽  
Transient Event ◽  
Ccd Imaging ◽  
X Ray ◽  
Lyman Alpha ◽  
Transmission Grating ◽  
Upper Limits ◽  
Far Ultraviolet

The cosmological missing baryons at z <  1 most likely hide in the hot (T ≳ 105.5 K) phase of the warm hot intergalactic medium (WHIM). While the hot WHIM is hard to detect due to its high ionisation level, the warm (T ≲ 105.5 K) phase of the WHIM has been very robustly detected in the far-ultraviolet (FUV) band. We adopted the assumption that the hot and warm WHIM phases are co-located and therefore used the FUV-detected warm WHIM as a tracer for the cosmologically interesting hot WHIM. We performed an X-ray follow-up in the sight line of the blazar PKS 2155–304 at the redshifts where previous FUV measurements of O VI, Si IV, and broad Lyman-alpha (BLA) absorption have indicated the existence of the warm WHIM. We looked for the O VII Heα and O VIII Lyα absorption lines, the most likely hot WHIM tracers. Despite the very large exposure time (≈1 Ms), the Reflection Grating Spectrometer unit 1 (RGS1) on-board XMM-Newton data yielded no significant detection which corresponds to upper limits of log N(O VII(cm−2)) ≤ 14.5−15.2 and log N(O VIII(cm−2)) ≤ 14.5−15.2. An analysis of the data obtained with the combination of the Low Energy Transmission Grating (LETG) and the High Resolution Camera (HRC) on-board Chandra yielded consistent results. However, the data obtained with the LETG, combined with the Advanced CCD Imaging Spectrometer (ACIS) lead to the detection of an feature resembling an absorption line at λ ≈ 20 Å at simple one-parameter confidence level of 3.7σ, consistent with several earlier LETG/ACIS reports. Given the high statistical quality of the RGS1 data, the possibility of RGS1 accidentally missing the true line at λ ∼ 20 Å is very low: 0.006%. Neglecting this, the LETG/ACIS detection can be interpreted as Lyα transition of O VIII at one of the redshifts (z ≈ 0.054) of FUV-detected warm WHIM. Given the very convincing X-ray spectral evidence for and against the existence of the λ ∼ 20 Å feature, we cannot conclude whether or not it is a true astrophysical absorption line. Considering cosmological simulations, the probability of the LETG/ACIS λ ∼ 20 Å feature being due to the astrophysical O VIII absorber co-located with the FUV-detected O VI absorber is at the very low level of ≲0.1%. We cannot completely rule out the very unlikely possibility that the LETG/ACIS 20 Å feature is due to a transient event located close to the blazar.

scholarly journals Large field-of-view X-ray imaging by using a Fresnel zone plate

2012 ◽  
Vol 30 (1) ◽  
pp. 87-93 ◽  
Author(s):  
Xiao-Fang Wang ◽  
Jin-Yu Wang ◽  
Xiao-Hu Chen ◽  
Xin-Gong Chen ◽  
Lai Wei
Keyword(s):  
High Resolution ◽  
Fresnel Zone ◽  
Numerical Study ◽  
Field Of View ◽  
Zone Plate ◽  
Large Field ◽  
Fresnel Zone Plate ◽  
X Rays ◽  
X Ray ◽  
X Ray Imaging

AbstractTo diagnose the implosion of a laser-driven-fusion target such as the symmetry, the hydrodynamic instability at the interface, a high-resolution, large field-of-view kilo-electron-volt X-ray imaging is required. A Kirkpatrick-Baez (K-B) microscope is commonly used, but its field of view is limited to a few hundred microns as the resolution decreases rapidly with the increase of the field of view. A higher resolution could be realized by using a Fresnel zone plate (FZP) for imaging. Presented in this work is a numerical study on the imaging properties of an FZP at Ti-Kα wavelength of 0.275 nm, and a comparison to a K-B imager. It is found that the FZP can realize not only a resolution better than 1 µm, but also a field-of-view larger than 20 mm when the FZP is illuminated by X-rays of spectral bandwidth less than 1.75%. These results indicate the feasibility of applying the FZP in high-resolution, large field-of-view X-ray imaging.

Joint AXAF high-resolution mirror assembly and AXAF CCD Imaging Spectrometer calibration at the MSFC X-Ray Calibration Facility

1998 ◽  
Author(s):  
John A. Nousek ◽  
Leisa K. Townsley ◽  
George Chartas ◽  
David N. Burrows ◽  
E. Moskalenko ◽  
...  
Keyword(s):  
High Resolution ◽  
Imaging Spectrometer ◽  
Ccd Imaging ◽  
X Ray ◽  
Calibration Facility ◽  
Spectrometer Calibration

Cryogenic high-resolution X-ray spectrometers for SR-XRF and microanalysis

1998 ◽  
Vol 5 (3) ◽  
pp. 515-517 ◽  
Author(s):  
M. Frank ◽  
C. A. Mears ◽  
S. E. Labov ◽  
L. J. Hiller ◽  
J. B. le Grand ◽  
...  
Keyword(s):  
High Resolution ◽  
Energy Resolution ◽  
Superconducting Tunnel Junction ◽  
Semiconductor Detectors ◽  
X Rays ◽  
X Ray ◽  
Sr Xrf ◽  
Demonstration Experiment ◽  
Near Future ◽  
Stj Detector

Experimental results are presented obtained with a cryogenically cooled high-resolution X-ray spectrometer based on a 141 × 141 µm Nb-Al-Al2O3-Al-Nb superconducting tunnel junction (STJ) detector in an SR-XRF demonstration experiment. STJ detectors can operate at count rates approaching those of semiconductor detectors while still providing a significantly better energy resolution for soft X-rays. By measuring fluorescence X-rays from samples containing transition metals and low-Z elements, an FWHM energy resolution of 6–15 eV for X-rays in the energy range 180–1100 eV has been obtained. The results show that, in the near future, STJ detectors may prove very useful in XRF and microanalysis applications.

Applications of High-Resolution Powder X-Ray Diffraction

2007 ◽  
Vol 130 ◽  
pp. 7-14 ◽  
Author(s):  
Andrew N. Fitch
Keyword(s):  
High Resolution ◽  
Synchrotron Radiation ◽  
Powder Diffraction ◽  
X Rays ◽  
X Ray Diffraction ◽  
Crystalline Materials ◽  
X Ray ◽  
Structural Characterisation ◽  
Pdf Analysis

The highly-collimated, intense X-rays produced by a synchrotron radiation source can be harnessed to build high-resolution powder diffraction instruments with a wide variety of applications. The general advantages of using synchrotron radiation for powder diffraction are discussed and illustrated with reference to the structural characterisation of crystalline materials, atomic PDF analysis, in-situ and high-throughput studies where the structure is evolving between successive scans, and the measurement of residual strain in engineering components.

HIGH-RESOLUTION PIXE USING BRAGG’S SPECTROMETER

1991 ◽  
Vol 01 (03) ◽  
pp. 251-258 ◽  
Author(s):  
M. TERASAWA
Keyword(s):  
High Resolution ◽  
Heavy Ions ◽  
X Rays ◽  
Light Elements ◽  
Element Analysis ◽  
X Ray ◽  
Peak Intensity ◽  
Moderate Energy ◽  
Practical Analysis ◽  
Wavelength Selectivity

K, L, and M X-rays in the wavelengths between 6Å and 130Å generated by the bombardment of 200 keV protons and other heavy ions were measured by means of a wavelength dispersive Bragg’s spectrometer. The X-ray peak intensity was fairly high in general, while the background was very low. The technique was favorably applied to a practical analysis of several light elements (Be, B, C, N, O, and F). Use of moderate-energy heavy ions considering the wavelength selectivity in X-ray generation was effective for the element analysis. The high-resolution spectrometry in the analytical application of ion-induced X-ray generation was found to be useful for the study of fine electronic structure, e.g. satellite and hypersatellite X-ray study, and of the chemical state of materials.

The Best of Both Worlds: 3D X-ray Microscopy with Ultra-high Resolution and a Large Field of View

2011 ◽  
Author(s):  
W. Li ◽  
J. Gelb ◽  
Y. Yang ◽  
Y. Guan ◽  
W. Wu ◽  
...  
Keyword(s):  
High Resolution ◽  
Field Of View ◽  
Large Field ◽  
X Ray

scholarly journals Micrometer-resolution imaging using MÖNCH: towards G2-less grating interferometry

2016 ◽  
Vol 23 (6) ◽  
pp. 1462-1473 ◽  
Author(s):  
Sebastian Cartier ◽  
Matias Kagias ◽  
Anna Bergamaschi ◽  
Zhentian Wang ◽  
Roberto Dinapoli ◽  
...  
Keyword(s):  
High Resolution ◽  
Silicon Detector ◽  
Limiting Factor ◽  
X Rays ◽  
X Ray ◽  
Charge Cloud ◽  
High Resolution Images ◽  
Resolution Imaging ◽  
Hybrid Silicon ◽  
Small Pixel

MÖNCH is a 25 µm-pitch charge-integrating detector aimed at exploring the limits of current hybrid silicon detector technology. The small pixel size makes it ideal for high-resolution imaging. With an electronic noise of about 110 eV r.m.s., it opens new perspectives for many synchrotron applications where currently the detector is the limiting factor,e.g.inelastic X-ray scattering, Laue diffraction and soft X-ray or high-resolution color imaging. Due to the small pixel pitch, the charge cloud generated by absorbed X-rays is shared between neighboring pixels for most of the photons. Therefore, at low photon fluxes, interpolation algorithms can be applied to determine the absorption position of each photon with a resolution of the order of 1 µm. In this work, the characterization results of one of the MÖNCH prototypes are presented under low-flux conditions. A custom interpolation algorithm is described and applied to the data to obtain high-resolution images. Images obtained in grating interferometry experiments without the use of the absorption grating G2are shown and discussed. Perspectives for the future developments of the MÖNCH detector are also presented.

scholarly journals The Effect of Image Resolution on Automated Classification of Chest X-rays

2021 ◽  
Author(s):  
Md Inzamam Ul Haque ◽  
Abhishek K Dubey ◽  
Jacob D Hinkle
Keyword(s):  
High Resolution ◽  
Automated Analysis ◽  
Image Resolution ◽  
Free Text ◽  
X Rays ◽  
Training Time ◽  
X Ray ◽  
Radiology Reports ◽  
Chest X Ray ◽  
High Resolution Images

Deep learning models have received much attention lately for their ability to achieve expert-level performance on the accurate automated analysis of chest X-rays. Although publicly available chest X-ray datasets include high resolution images, most models are trained on reduced size images due to limitations on GPU memory and training time. As compute capability continues to advance, it will become feasible to train large convolutional neural networks on high-resolution images. This study is based on the publicly available MIMIC-CXR-JPG dataset, comprising 377,110 high resolution chest X-ray images, and provided with 14 labels to the corresponding free-text radiology reports. We find, interestingly, that tasks that require a large receptive field are better suited to downscaled input images, and we verify this qualitatively by inspecting effective receptive fields and class activation maps of trained models. Finally, we show that stacking an ensemble across resolutions outperforms each individual learner at all input resolutions while providing interpretable scale weights, suggesting that multi-scale features are crucially important to information extraction from high-resolution chest X-rays.

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