scholarly journals X-Ray Observations of M87’s Halo

1980 ◽  
Vol 5 ◽  
pp. 689-693
Author(s):  
D. Fabricant ◽  
M. Lecar ◽  
P. Gorenstein
Keyword(s):  
Proportional Counter ◽  
Total Mass ◽  
Precise Determination ◽  
Virgo Cluster ◽  
Field Of View ◽  
Two Dimensional ◽  
X Ray ◽  
Einstein Observatory ◽  
Extended Emission

We briefly describe the soft X-ray image of M87 obtained using the imaging proportional counter aboard the Einstein Observatory. These data provide further strong evidence for the existence of a massive halo of dark matter surrounding M87 and allow a much more precise determination of its mass. Two pointing positions of the satellite were analyzed; one centered on M87, the other 63’ south and 25’ east of M87. The field of view of the imaging proportional counter is 60’ × 60’, and it attains a two dimensional spatial resolution of ˜ 1.5’ in a spectral range spanning 0.1 to 4.5 keV.As previous reports had suggested (Gorenstein et al. 1977; Fabricant et al. 1978), the present observations show M87 to be a strong, very extended, thermal X-ray source with a temperature near 2 keV, surrounded by weaker and still more extended emission from hotter gas associated with the Virgo cluster as a whole (Davison, 1978; Lawrence, 1978). We find M87 to have a total 0.5-4.5 keV X-ray luminosity of about 2 × 1043 ergs/sec, and an extrapolated 2-6 keV luminosity of approximately 1 × 1043 ergs/sec. The total mass of gas inferred from the X-ray measurement exceeds 1012 solar masses.

scholarly journals Review of Recent Observations of Cluster X-Ray Sources Using the Einstein Observatory

1980 ◽  
Vol 5 ◽  
pp. 727-734
Author(s):  
Stephen S. Murray
Keyword(s):  
Energy Resolution ◽  
Proportional Counter ◽  
Field Of View ◽  
Clusters Of Galaxies ◽  
X Ray ◽  
Moderate Energy ◽  
Einstein Observatory

In this contribution I shall review briefly some of the recent research being carried out at the Harvard-Smithsonian Center for Astrophysics in the study of X-ray emission from clusters of galaxies. This work is being done by several of us at CFA, and I particularly wish to thank Drs. Christine Jones, William Forman, and J. Patrick Henry for permission to discuss their results. The data have been obtained from the Einstein X-ray Observatory (HEAO-2) using the imaging instruments, and in particular the Imaging Proportional Counter (IPC). This gives X-ray images with about l½ arc minute resolution over a field of view of ½° × ½° and moderate energy resolution over a band from 0.5 to 3.0 keV. (For further details see Giacconi et al. 1979).

scholarly journals The Degree of Oxidation of Graphene Oxide

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 560
Author(s):  
Alexandra Carvalho ◽  
Mariana C. F. Costa ◽  
Valeria S. Marangoni ◽  
Pei Rou Ng ◽  
Thi Le Hang Nguyen ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Ab Initio ◽  
State Of The Art ◽  
High Accuracy ◽  
Precise Determination ◽  
Photoemission Spectroscopy ◽  
Pristine Graphene ◽  
X Ray ◽  
Degree Of Oxidation

We show that the degree of oxidation of graphene oxide (GO) can be obtained by using a combination of state-of-the-art ab initio computational modeling and X-ray photoemission spectroscopy (XPS). We show that the shift of the XPS C1s peak relative to pristine graphene, ΔEC1s, can be described with high accuracy by ΔEC1s=A(cO−cl)2+E0, where c0 is the oxygen concentration, A=52.3 eV, cl=0.122, and E0=1.22 eV. Our results demonstrate a precise determination of the oxygen content of GO samples.

scholarly journals X-Ray Sources of Cosmological Relevance

1983 ◽  
Vol 104 ◽  
pp. 7-18
Author(s):  
T. Maccacaro ◽  
I. M. Gioia
Keyword(s):  
Proportional Counter ◽  
Extragalactic Astronomy ◽  
X Ray ◽  
Einstein Observatory

The imaging and spectroscopic instruments onboard the Einstein Observatory (Giacconi et al. 1979) have been extensively used to study in detail the X-ray properties of a large variety of astronomical objects. In this paper we will briefly discuss some of the most relevant results on extragalactic astronomy obtained mainly with the Imaging Proportional Counter (IPC).

Intraoperative Determination of the Extent of Corpus Callosotomy for Epilepsy: Two Simple Techniques

Neurosurgery ◽  
1990 ◽  
Vol 26 (1) ◽  
pp. 102-106 ◽  
Author(s):  
Issam A. Awad ◽  
Elaine Wyllie ◽  
Hans Luders ◽  
Jennifer Ahl
Keyword(s):  
Corpus Callosum ◽  
Precise Determination ◽  
Planar Geometry ◽  
Corpus Callosotomy ◽  
Midsagittal Plane ◽  
Anatomic Landmarks ◽  
Mri Scan ◽  
Simple Modification ◽  
X Ray

Abstract There is increasing interest in staged corpus callosotomy for intractable generalized epilepsy. At the first procedure, a portion (usually the anterior two-thirds) of the corpus callosum is sectioned. If seizures persist, completion of callosotomy or alternative treatment approaches can be considered. It is obviously important to ascertain that the desired extent of callosotomy was in fact accomplished at the time of initial operation. Our experience and the published literature indicate that the surgeon's impression at operation can be erroneous. We describe a technique of determining extent of corpus callosotomy during the procedure. The magnetic resonance imaging (MRI) scan in the midsagittal plane is used to select the desired extent of callosotomy. That point on the corpus callosum is characterized using simple planar geometry in relation to three anatomic landmarks in that same plane: the glabella, the inion, and the bregma (midline intersection of the coronal suture). The same point along the corpus callosum can then be located on a lateral skull xray using these same three anatomic landmarks. At surgery, an intraoperative lateral skull x-ray is obtained with a marking clip, thereby verifying the actual extent of callosotomy. We have verified the reliability of this scheme in 5 callosotomy procedures and have used this technique for intraoperative localization of midline and parasagittal targets in another 7 cases (3 tumors, 2 aneurysms, and 2 placements of interhemispheric subdural grids). In addition, we reviewed corpus callosum topography on 25 randomly selected MRI scans. A perpendicular line bisecting the glabellainion line intersects the corpus callosum at a point near its two-thirds extent in every case. This allows a quick determination of the approximate two-thirds point along the corpus callosum by skull x-ray alone, without the need of an MRI scan. The use of the new technique and its simple modification for the two-thirds callosotomy allows a precise determination of the extent of corpus callosum section at surgery and should avoid unintended deviations from the desired procedure. (Neurosurgery 26:102-106, 1990)

scholarly journals X-ray observations of symbiotic stars

1982 ◽  
Vol 70 ◽  
pp. 115-116
Author(s):  
David A. Allen
Keyword(s):  
Steady State ◽  
Proportional Counter ◽  
White Dwarfs ◽  
Symbiotic Stars ◽  
X Ray ◽  
The Past ◽  
Accretion Process ◽  
Einstein Observatory

AbstractObservations are reported of 19 symbiotic stars made with the imaging proportional counter of the Einstein Observatory. Three of the objects (HM Sge, V 1016 Cyg and RR Tel) were detected as soft X-ray sources. All three have shown slow-nova eruptions in the past 40 years. The data are interpreted as support of a model for slow novae involving thermonuclear events on white dwarfs which accrete from M giant companions. Symbiotic stars in their steady state, not being detected X-ray sources, are presumed to be powered by the accretion process alone.

Computer reconstructed X-ray imaging

1979 ◽  
Vol 292 (1390) ◽  
pp. 223-232 ◽  
Keyword(s):  
Spatial Resolution ◽  
Atomic Number ◽  
High Sensitivity ◽  
Precise Determination ◽  
Diagnostic Methods ◽  
X Ray ◽  
X Ray Imaging ◽  
Internal Structures ◽  
Transmission Measurements

Computed tomography is a method for obtaining a series of radiographic pictures of contiguous slices through a solid object such as the human body. Each picture is computed from a set of X-ray transmission measurements and represents the distribution of X-ray attenuation in the slice. The high sensitivity of the method to changes in both density and atomic number has resulted in the development of new diagnostic methods in medicine. The limitations of the method are discussed in terms of two particular kinds of application. First, those applications in which a very precise determination of density or atomic number is required, but at low spatial resolution; an example would be the determination of the uniformity of mixture of plastics or metals. The second kind of application is that requiring high spatial resolution as in the detection of cracks and the visualization of internal structures in complicated objects.

scholarly journals Determination of hard X-ray polarization from two-dimensional images

2020 ◽  
Vol 53 (6) ◽  
pp. 1559-1561
Author(s):  
Robert B. Von Dreele ◽  
Wenqian Xu
Keyword(s):  
Incident Beam ◽  
Beam Polarization ◽  
Two Dimensional ◽  
One Dimensional ◽  
X Ray ◽  
Dimensional Image ◽  
Two Dimensional Image ◽  
The Difference ◽  
Two Dimensional Images

An estimate of synchrotron hard X-ray incident beam polarization is obtained by partial two-dimensional image masking followed by integration. With the correct polarization applied to each pixel in the image, the resulting one-dimensional pattern shows no discontinuities arising from the application of the mask. Minimization of the difference between the sums of the masked and unmasked powder patterns allows estimation of the polarization to ±0.001.

scholarly journals The Mass and Structure of the Remnant of Tycho's Supernova

1983 ◽  
Vol 101 ◽  
pp. 1-15 ◽  
Author(s):  
Paul Gorenstein ◽  
Frederick Seward ◽  
Wallace Tucker
Keyword(s):  
Total Mass ◽  
Column Density ◽  
Supernova Remnant ◽  
Average Density ◽  
Equilibrium Calculation ◽  
Free Expansion ◽  
X Ray ◽  
Upper Limit ◽  
Interstellar Material ◽  
Einstein Observatory

A high resolution X-ray image of Tycho's supernova remnant obtained from the Einstein Observatory reveals three components of X-ray emission that we identify with shocked interstellar material, diffuse ejecta, and clumpy ejecta. This picture is applied to derive the mass of X-ray emitting material. Assuming a distance of 3 kpc, an absorbing column density of 3 × 1021 atoms/cm2, and using an ion-electron non-equilibrium calculation for the emissivity, we find the average density of the ISM is 0.4 atoms/cm3, and the energy contained in the remnant is 1.4 × 1051 ergs. The total mass of X-ray emitting material in the remnant is ≈4 M⊙, ≈2 M⊙ ejecta and ≈2 M⊙ swept up, putting the remnant at an intermediate state between a free expansion and the Sedov phase. There is no evidence for neutron star. The upper limit on the surface temperature is in the range 1.1 to 1.8 × 106K.

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