scholarly journals Spectroscopic Techniques in X-Ray Astronomy

1972 ◽  
Vol 14 ◽  
pp. 845-869 ◽  
Author(s):  
Leon Van Speybroeck
Keyword(s):  
Energy Range ◽  
Seyfert Galaxies ◽  
High Energy ◽  
Spectroscopic Techniques ◽  
X Rays ◽  
Energy Limit ◽  
Ample Evidence ◽  
X Ray ◽  
Normal Galaxies ◽  
Electron Production

The catalog of X-ray sources now includes types I and II super-novae remnants, at least one pulsar, other periodic or quasi-periodic sources, starlike objects which emit primarily in X rays, normal galaxies, radio galaxies, Seyfert galaxies, a quasar, and an apparently isotropic extragalactic background. There is ample evidence that X-ray emission is characteristic of many of the most interesting objects in astronomy, and the background may have cosmological implications. This should not be too surprising, since significant X-ray emission occurs whenever high energy electrons interact, and high energy electron production is usually associated with explosive phenomena.The most useful energy range for X-ray observations extends from about 200 eV to perhaps 10 keV. The low energy limit results from the absorption by the interstellar media, which of course varies from object to object; some typical cutoffs are given in Table I. The high energy limit, which is much more arbitrary, results from the usually observed rapidly decreasing emission with increasing energy, and also from the lack of important characteristic emission or absorption features above this energy range. In many cases, however, observations outside of this energy range are required to definitively identify a dominant source mechanism.

scholarly journals X-rays from Photoionized Accretion Discs

1994 ◽  
Vol 159 ◽  
pp. 380-380
Author(s):  
G. Matt ◽  
A.C. Fabian ◽  
R.R. Ross
Keyword(s):  
Black Hole ◽  
Seyfert Galaxies ◽  
High Energy ◽  
Accretion Disc ◽  
Accretion Discs ◽  
X Rays ◽  
Central Black Hole ◽  
X Ray

The presence of iron lines and high energy excesses in the X-ray spectra of Seyfert galaxies has been firmly established by Ginga (e.g. Nandra & Pounds 1993 and references therein). These features are generally interpreted as signatures of the reprocessing of the primary X-rays by matter in the neighbourhood of the central black hole, probably distributed in an accretion disc (Lightman & White 1988, George & Fabian 1991, Matt, Perola & Piro 1991).

scholarly journals Centaurus A at Hard X-Rays and Soft Gamma-Rays

2010 ◽  
Vol 27 (4) ◽  
pp. 431-438 ◽  
Author(s):  
H. Steinle
Keyword(s):  
Energy Range ◽  
Spatial Resolution ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
Satellite Mission ◽  
X Ray

AbstractCen A, at a distance of less than 4 Mpc, is the nearest radio-loud AGN. Its emission is detected from radio to very-high energy gamma-rays. Despite the fact that Cen A is one of the best studied extragalactic objects the origin of its hard X-ray and soft gamma-ray emission (100 keV <E< 50 MeV) is still uncertain. Observations with high spatial resolution in the adjacent soft X-ray and hard gamma-ray regimes suggest that several distinct components such as a Seyfert-like nucleus, relativistic jets, and even luminous X-ray binaries within Cen A may contribute to the total emission in the MeV regime that has been detected with low spatial resolution. As the Spectral Energy Distribution of Cen A has its second maximum around 1 MeV, this energy range plays an important role in modeling the emission of (this) AGN. As there will be no satellite mission in the near future that will cover this energies with higher spatial resolution and better sensitivity, an overview of all existing hard X-ray and soft gamma-ray measurements of Cen A is presented here defining the present knowledge on Cen A in the MeV energy range.

scholarly journals Hot Accretion Disks and the High Energy Background

1983 ◽  
Vol 104 ◽  
pp. 345-346
Author(s):  
M. Kafatos ◽  
Jean A. Eilek
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Spectral Range ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
High Energy ◽  
X Rays ◽  
X Ray

The origin of the high energy (X-ray and gamma-ray) background may be attributed to discrete sources, which are usually thought to be active galactic nuclei (AGN) (cf. Rothschild et al. 1982, Bignami et al. 1979). At X-rays a lot of information has been obtained with HEAO-1 in the spectral range 2–165 keV. At gamma-rays the background has been estimated from the Apollo 15 and 16 (Trombka et al. 1977) and SAS-2 (Bignami et al. 1979) observations. A summary of some of the observations (Rothschild et al. 1982) is shown in Figure 1. The contribution of AGN to the diffuse high energy background is uncertain at X-rays although it is generally estimated to be in the 20–30% range (Rothschild et al. 1982). At gamma-rays, in the range 1–150 MeV, AGN (specifically Seyfert galaxies) could account for all the emission.

scholarly journals Solar flares observed simultaneously with SphinX, GOES and RHESSI

2012 ◽  
Vol 8 (S294) ◽  
pp. 571-572 ◽  
Author(s):  
Tomasz Mrozek ◽  
Szymon Gburek ◽  
Marek Siarkowski ◽  
Barbara Sylwester ◽  
Janusz Sylwester ◽  
...  
Keyword(s):  
Energy Range ◽  
Solar Flares ◽  
Solar Minimum ◽  
Spectroscopic Analysis ◽  
High Energy ◽  
Pin Diode ◽  
X Rays ◽  
X Ray ◽  
Thermal Part ◽  
Silicon Pin Diode

AbstractIn February 2009, during recent deepest solar minimum, Polish Solar Photometer in X-rays (SphinX) begun observations of the Sun in the energy range of 1.2–15 keV. SphinX was almost 100 times more sensitive than GOES X-ray Sensors. The silicon PIN diode detectors used in the experiment were carefully calibrated on the ground using Synchrotron Radiation Source BESSY II. The SphinX energy range overlaps with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) energy range. The instrument provided us with observations of hundreds of very small flares and X-ray brightenings. We have chosen a group of solar flares observed simultaneously with GOES, SphinX and RHESSI and performed spectroscopic analysis of observations wherever possible. The analysis of thermal part of the spectra showed that SphinX is a very sensitive complementary observatory for RHESSI and GOES.

scholarly journals X-Ray Observations of the Galactic Centre

1989 ◽  
Vol 136 ◽  
pp. 567-580 ◽  
Author(s):  
G. K. Skinner
Keyword(s):  
Energy Range ◽  
High Energy ◽  
Point Sources ◽  
Galactic Centre ◽  
X Rays ◽  
Diffuse Emission ◽  
Variable Source ◽  
X Ray ◽  
Centre Region ◽  
Sgr A

Observations of the galactic centre region in the photon energy range 2–500 keV are reviewed. Point sources, transients, bursts and a patch of apparently diffuse emission ~1° in extent have all been observed. The relatively detailed information obtained with the Einstein observatory just above the bottom edge of the x-ray window is starting to be supplemented by observations at higher photon energies. Although there is known to be a strong, variable, source of high energy x-rays somewhere in the region there is little reason to associate it with Sgr A West, which is detectable, but relatively weak, in the energy range below 30 keV where detailed measurements have been possible.

Observational results on diffuse cosmic X-rays: (Invited discourse)

1970 ◽  
Vol 37 ◽  
pp. 260-268
Author(s):  
Minoru Oda
Keyword(s):  
Energy Spectrum ◽  
Energy Range ◽  
Present Status ◽  
X Rays ◽  
X Ray ◽  
Normal Galaxies ◽  
The Universe

The present status of observations of the diffuse cosmic X-rays is discussed. The energy spectrum in the energy range 1–100 keV has been well established. The flux around 0.25 keV appears to be rather high. The basis of the classical argument that the integration of normal galaxies in the universe is not sufficient to explain the diffuse X-ray flux is re-examined. Recent observations around 0.25 keV are discussed and results are compiled.

THE DOPPLER FACTORS AT X-RAY BAND OF THE BLAZARS

2005 ◽  
Vol 14 (06) ◽  
pp. 947-956
Author(s):  
D. C. MEI ◽  
L. ZHANG
Keyword(s):  
Synchrotron Radiation ◽  
Energy Range ◽  
High Energy ◽  
Low Energy ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Doppler Factor ◽  
Intrinsic Radiation

We study the Doppler factors for a group blazars at soft X-ray band. In our estimates, we have made the assumptions that (i) blazars can be divided into high-energy-peaked (HEP) objects whose synchrotron peak frequencies νp > 1014.7 Hz , and the low-energy-peaked (LEP) objects whose synchrotron peak frequencies νp≤1014.7 Hz , and (ii) the intrinsic radiation from a blazar in the energy range from radio to soft X-ray bands is the synchrotron radiation for HEP objects and the soft X-ray emission comes from inverse Compton scattering for LEP objects. Under the above assumptions, we estimate Doppler factors at optical (δO) and X-rays (δx) for 54 blazars by using the known radio Doppler factors and the observed flux densities in radio, optical and X-ray bands, and Doppler factors [Formula: see text] at X-ray band in which X-rays are assumed to be produced only by the synchrotron radiation. We get [Formula: see text] . The Doppler factors are different in various wavebands, and on average, the Doppler factor decreases with frequency from radio to X-ray bands.

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

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.

scholarly journals Transient absorption spectroscopy using high harmonic generation: a review of ultrafast X-ray dynamics in molecules and solids

2019 ◽  
Vol 377 (2145) ◽  
pp. 20170463 ◽  
Author(s):  
Romain Geneaux ◽  
Hugo J. B. Marroux ◽  
Alexander Guggenmos ◽  
Daniel M. Neumark ◽  
Stephen R. Leone
Keyword(s):  
Time Scales ◽  
Harmonic Generation ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
High Harmonic ◽  
High Harmonic Generation ◽  
Transient Absorption Spectroscopy ◽  
Spectroscopic Techniques ◽  
X Rays ◽  
X Ray

Attosecond science opened the door to observing nuclear and electronic dynamics in real time and has begun to expand beyond its traditional grounds. Among several spectroscopic techniques, X-ray transient absorption spectroscopy has become key in understanding matter on ultrafast time scales. In this review, we illustrate the capabilities of this unique tool through a number of iconic experiments. We outline how coherent broadband X-ray radiation, emitted in high-harmonic generation, can be used to follow dynamics in increasingly complex systems. Experiments performed in both molecules and solids are discussed at length, on time scales ranging from attoseconds to picoseconds, and in perturbative or strong-field excitation regimes. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

scholarly journals PHEMTO: the polarimetric high energy modular telescope observatory

2021 ◽  
Author(s):  
P. Laurent ◽  
F. Acero ◽  
V. Beckmann ◽  
S. Brandt ◽  
F. Cangemi ◽  
...  
Keyword(s):  
Black Holes ◽  
Energy Range ◽  
High Performance ◽  
Angular Resolution ◽  
High Energy ◽  
Thermal Processes ◽  
Scientific Performance ◽  
X Ray ◽  
Measurement Capability ◽  
Better Than

AbstractBased upon dual focusing techniques, the Polarimetric High-Energy Modular Telescope Observatory (PHEMTO) is designed to have performance several orders of magnitude better than the present hard X-ray instruments, in the 1–600 keV energy range. This, together with its angular resolution of around one arcsecond, and its sensitive polarimetry measurement capability, will give PHEMTO the improvements in scientific performance needed for a mission in the 2050 era in order to study AGN, galactic black holes, neutrons stars, and supernovae. In addition, its high performance will enable the study of the non-thermal processes in galaxy clusters with an unprecedented accuracy.

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