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1

Spectral analysis of X-ray binaries  

E-print Network

In this thesis, I present work from three separate research projects associated with observations of X-ray binaries. Two of those revolve around spectral characteristics of neutron star low-mass X-ray binaries (NS-LMXBs), ...

Fridriksson, Joel Karl

2011-01-01

2

X-ray grating spectrometer for opacity measurements in the 50 eV to 250 eV spectral range at the LULI 2000 laser facility  

SciTech Connect

An x-ray grating spectrometer was built in order to measure opacities in the 50 eV to 250 eV spectral range with an average spectral resolution {approx} 50. It has been used at the LULI-2000 laser facility at Ecole Polytechnique (France) to measure the {Delta}n = 0, n = 3 transitions of several elements with neighboring atomic number: Cr, Fe, Ni, and Cu in the same experimental conditions. Hence a spectrometer with a wide spectral range is required. This spectrometer features one line of sight looking through a heated sample at backlighter emission. It is outfitted with one toroidal condensing mirror and several flat mirrors cutting off higher energy photons. The spectral dispersion is obtained with a flatfield grating. Detection consists of a streak camera sensitive to soft x-ray radiation. Some experimental results showing the performance of this spectrometer are presented.

Reverdin, Charles; Caillaud, T.; Gilleron, F.; Pain, J. C.; Silvert, V.; Soullie, G.; Villette, B. [CEA, DAM, DIF, 91297 Arpajon (France); Thais, Frederic; Loisel, Guillaume; Blenski, T.; Poirier, M. [CEA, DSM, IRAMIS, Service Photons, Atomes et Molecules, 91191 Gif-sur-Yvette (France); Busquet, M. [ARTEP Inc, Ellicott City, Maryland 21042 (United States); Bastiani-Ceccotti, S.; Serres, F. [LULI, Ecole Polytechnique, CNRS, CEA, UPMC, route de Saclay, 91128 Palaiseau (France); Ducret, J. E. [CELIA, UMR5107, CEA, CNRS, Universite de Bordeaux, 33400 Talence (France); Foelsner, W. [Max Planck Instituet fuer Quantum Optik, 85748 Garching (Germany); Gilles, D.; Turck-Chieze, S. [CEA, DSM, IRFU, Service d'astrophysique, 91191 Gif-sur-Yvette (France)

2012-10-15

3

X-ray crystal spectrometer for opacity measurements in the 8-18 A˚ spectral range at the LULI laser facility  

Microsoft Academic Search

An x-ray crystal spectrometer was built in order to measure opacities in the 8-18 A˚ spectral range with an average spectral resolution of ~400. It has been successfully used at the LULI-2000 laser facility (See C. Sauteret, rapport LULI 2001, 88 (2002) at École Polytechnique (France) to measure in the same experimental conditions the 2p-3d transitions of several elements with

C. Reverdin; F. Thais; G. Loisel; M. Bougeard

2010-01-01

4

Spectral slicing X-ray telescope  

NASA Astrophysics Data System (ADS)

Layered synthetic microstructure (LSM) X-ray optics is investigated as a system for coupling a conventional glancing incidence X-ray mirror to a high sensitivity X-ray detector. It is shown that, by the use of figured LSM optics, it is possible to magnify the X-ray image produced by the primary mirrors so as to maintain their high inherent spatial resolution. The results of theoretical and design analyses of several spectral slicing X-ray telescope systems that utilize LSM mirrors of hyperboloidal, spherical, ellipsoidal, and constant optical path aspheric configurations are presented. It is shown that the spherical LSM optics are the preferred configuration, yielding subarcsecond performance over the entire field. The Stanford/Marshall Space Flight Center Rocket X-ray Telescope, which will utilize normal incidence LSM optics to couple a Wolter-Schwarzschild primary mirror to high resolution detectors for solar X-ray/EUV studies, is discussed. Design diagrams are included.

Hoover, R. B.; Shealy, D.; Chao, S.-H.

1986-08-01

5

Freestanding multilayer films for application as phase retarders and spectral purity filters in the soft x-ray and EUV ranges  

NASA Astrophysics Data System (ADS)

A technique for fabrication of freestanding multilayers which are able to be used as optical elements in the soft X-ray and EUV ranges is reported. Two types of transmission mode elements have been developed: phase retarders for the aims of soft X-ray polarimetry and thin film spectral filters. A variety of phase retarders on the base of Cr/Sc, Cr/C, V/B4C and W/B4C freestanding multilayers were designed for a spectral region of "water window" (?~ 2-4.5nm) 2 - 4.5 nm). The possibility to yield the phase shift between s- and p-polarizations as high as 90º at equal transparencies of these polarizations of 0.4% was experimentally demonstrated with Cr/Sc phase retarder close to the Sc L-edge of absorption (? = 3.11 nm). The set of freestanding absorption filters Cr/Sc, Mo/C, Zr/Si, Zr/Al with spectral windows within 2.2 to 22 nm wavelength range was developed for the aims of hot plasma diagnostics. We also fabricated Al/Si structures with supported mesh, which are transparent in the range ? = 17 - 60 nm, for application in the sun astronomy. The sample of 160 mm in diameter Mo/ZrSi2 spectral purity filters with transparency of 70% (? = 13 nm) was fabricated as the probable component part of industrial EUV lithography tool. The preliminary testing of heat load withstandability was fulfilled for a number of freestanding multilayers consisting of Si, Zr, Mo and silicides of both metals. It was found that Mo/ZrSi2 structure is the challenge to withstand intensive heating up to 800 - 850°C.

Chkhalo, N. I.; Drozdov, M. N.; Gusev, S. A.; Kluenkov, E. B.; Lopatin, A. Ya.; Luchin, V. I.; Salashchenko, N. N.; Shmaenok, L. A.; Tsybin, N. N.; Volodin, B. A.

2011-05-01

6

The Swift X-ray Telescope Cluster Survey. II. X-ray spectral analysis  

NASA Astrophysics Data System (ADS)

Aims: We present a spectral analysis of a new, flux-limited sample of 72 X-ray selected clusters of galaxies identified with the X-ray Telescope (XRT) on board the Swift satellite down to a flux limit of ~10-14 erg s-1 cm-2 (SWXCS). We carry out a detailed X-ray spectral analysis with the twofold aim of measuring redshifts and characterizing the properties of the intracluster medium (ICM) for the majority of the SWXCS sources. Methods: Optical counterparts and spectroscopic or photometric redshifts for some of the sources are obtained with a cross-correlation with the NASA/IPAC Extragalactic Database. Additional photometric redshifts are computed with a dedicated follow-up program with the Telescopio Nazionale Galileo and a cross-correlation with the SDSS. In addition, we also blindly search for the Hydrogen-like and He-like iron K? emission line complex in the X-ray spectrum. We detect the iron emission lines in 35% of the sample, and hence obtain a robust measure of the X-ray redshift zX with typical rms error 1-5%. We use zX whenever the optical redshift is not available. Finally, for all the sources with measured redshift, background-subtracted spectra are fitted with a single-temperature mekal model to measure global temperature, X-ray luminosity and iron abundance of the ICM. We perform extensive spectral simulations to accounts for fitting bias, and to assess the robustness of our results. We derive a criterion to select reliable best-fit models and an empirical formula to account for fitting bias. The bias-corrected values are then used to investigate the scaling properties of the X-ray observables. Results: Overall, we are able to characterize the ICM of 46 sources with redshifts (64% of the sample). The sample is mostly constituted by clusters with temperatures between 3 and 10 keV, plus 14 low-mass clusters and groups with temperatures below 3 keV. The redshift distribution peaks around z ~ 0.25 and extends up to z ~ 1, with 60% of the sample at 0.1 < z < 0.4. We derive the luminosity-temperature relation for these 46 sources, finding good agreement with previous studies. Conclusions: Thanks to the good X-ray spectral quality and the low background of Swift/XRT, we are able to measure ICM temperatures and X-ray luminosities for the 46 sources with redshifts. Once redshifts are available for the remaining 26 sources, this sample will constitute a well-characterized, flux-limited catalog of clusters distributed over a broad redshift range (0.1 ? z ? 1.0) providing a statistically complete view of the cluster population with a selection function that allows a proper treatment of any measurement bias. The quality of the SWXCS sample is comparable to other samples available in the literature and obtained with much larger X-ray telescopes. Our results have interesting implications for the design of future X-ray survey telescopes, characterized by good-quality PSF over the entire field of view and low background. Tables 1 and 2 and Appendix A are available in electronic form at http://www.aanda.orgCatalog and data products of SWXCS, constantly updated, are made available to the public through the websites http://www.arcetri.astro.it/SWXCS/ and http://swxcs.ustc.edu.cn/

Tozzi, P.; Moretti, A.; Tundo, E.; Liu, T.; Rosati, P.; Borgani, S.; Tagliaferri, G.; Campana, S.; Fugazza, D.; D'Avanzo, P.

2014-07-01

7

High spectral and spatial resolution X-ray transmission radiography and tomography using a Color X-ray Camera  

PubMed Central

High resolution X-ray radiography and computed tomography are excellent techniques for non-destructive characterization of an object under investigation at a spatial resolution in the micrometer range. However, as the image contrast depends on both chemical composition and material density, no chemical information is obtained from this data. Furthermore, lab-based measurements are affected by the polychromatic X-ray beam, which results in beam hardening effects. New types of X-ray detectors which provide spectral information on the measured X-ray beam can help to overcome these limitations. In this paper, an energy dispersive CCD detector with high spectral resolution is characterized for use in high resolution radiography and tomography, where a focus is put on the experimental conditions and requirements of both measurement techniques. PMID:24357889

Boone, Matthieu N.; Garrevoet, Jan; Tack, Pieter; Scharf, Oliver; Cormode, David P.; Van Loo, Denis; Pauwels, Elin; Dierick, Manuel; Vincze, Laszlo; Van Hoorebeke, Luc

2013-01-01

8

Non-periodic multilayer coatings in EUV, soft x-ray and x-ray range  

Microsoft Academic Search

Non-periodic multilayer coatings offer engineer great flexibility to achieve tailored spectral performance in EUV, soft X-ray and X-ray region. We have developed a variety of non-periodic multilayer mirrors for use as optical key components for polarization-sensitive studies, Kirkpatrick-Baez microscope, Earth's magnetosphere observation and reflection of sub-femtosecond pulses. To find optimal distribution of layer thicknesses for a given spectral response, several

Zhanshan Wang

2008-01-01

9

Synchrotron-radiation-operated cryogenic electrical-substitution radiometer as the high-accuracy primary detector standard in the ultraviolet, vacuum-ultraviolet, and soft-x-ray spectral ranges.  

PubMed

The accuracy of detector calibration in the UV, vacuum-ultraviolet, and soft-x-ray spectral ranges could be significantly improved by the use of the synchrotron radiation electrical substitution radiometer (SYRES) as the primary detector standard. The SYRES radiometer is optimized for use with spectrally dispersed synchrotron radiation as supplied by two monochromator beam lines in the radiometry laboratory of the Physikalisch-Technische Bundesanstalt at the Berlin electron-storage ring (BESSY). Wavelength ranges from 0.8 to 25 nm and from 35 to 400 nm are covered. The typically available radiant power of approximately 1-10 microW can be measured with the SYRES radiometer with a standard relative uncertainty of less than 0.2%. The spectral responsivity of qualified photodiodes for use as secondary detector standards is determined by direct comparison with the primary detector standard at an arbitrary wavelength. At present, the scale of spectral responsivity is realized with a standard relative uncertainty of well below 1% in the spectral ranges 0.8-3.5 nm, 5-25 nm, and 120-400 nm. We provide a comprehensive description of the SYRES radiometer and of the two facilities for detector calibration in the UV and vacuum-ultraviolet spectral ranges and in the soft-x-ray spectral range, respectively, and we discuss the achievable uncertainties in the calibration of detectors. PMID:18259363

Rabus, H; Persch, V; Ulm, G

1997-08-01

10

Phase-resolved X-ray spectroscopy and spectral energy distribution of the X-ray soft polar RS Caeli  

NASA Astrophysics Data System (ADS)

Context. RS Cae is the third target in our series of XMM-Newton observations of soft X-ray-dominated polars. Aims: Our observational campaign aims to better understand and describe the multiwavelength data, the physical properties of the system components, and the short- and long-term behavior of the component fluxes in RS Cae. Methods: We employ stellar atmosphere, stratified accretion-column, and widely used X-ray spectral models. We fit the XMM-Newton spectra, model the multiband light curves, and opt for a mostly consistent description of the spectral energy distribution. Results: Our XMM-Newton data of RS Cae are clearly dominated by soft X-ray emission. The X-ray light curves are shaped by emission from the main accretion region, which is visible over the whole orbital cycle, interrupted only by a stream eclipse. The optical light curves are formed by cyclotron and stream emission. The XMM-Newton X-ray spectra comprise a black-body-like and a plasma component at mean temperatures of 36 eV and 7 keV. The spectral fits give evidence of a partially absorbing and a reflection component. Multitemperature models, covering a broader temperature range in the X-ray emitting accretion regions, reproduce the spectra appropriately well. Including archival data, we describe the spectral energy distribution with a combination of models based on a consistent set of parameters and derive a lower limit estimate of the distance d ? 750 pc. Conclusions: The high bolometric soft-to-hard flux ratios and short-term variability of the (X-ray) light curves are characteristic of inhomogeneous accretion. RS Cae clearly belongs in the group of polars that show a very strong soft X-ray flux compared to their hard X-ray flux. The different black-body fluxes and similar hard X-ray and optical fluxes during the XMM-Newton and ROSAT observations show that soft and hard X-ray emission are not directly correlated. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Traulsen, I.; Reinsch, K.; Schwope, A. D.; Schwarz, R.; Walter, F. M.; Burwitz, V.

2014-02-01

11

A new X-ray spectral observation of NGC 1068  

NASA Technical Reports Server (NTRS)

A new X-ray observation of NGC 1068, in which improved spectral resolution (R is approximately equal to 40) and broad energy range provide important new constraints on models for this galaxy, is reported. The observed X-ray continuum of NGC 1068 from 0.3 to 10 keV is well fitted as the sum of two power-law spectra with no evidence for absorption intrinsic to the source. Strong Fe K emission lines with a total equivalent width of 2700 eV were detected due to iron less ionized than Fe XX and to iron more ionized than Fe XXIII. No evidence was seen for lines due to the recombination of highly ionized oxygen with an upper limit for the O Ly-alpha emission line of 40 eV. The discovery of multiple Fe K and Fe L emission lines indicates a broad range of ionization states for this gas. The X-ray emission from the two components is modeled for various geometries using a photoionization code that calculates the temperature and ionization state of the gas. Typical model parameters are a total Compton depth of a few percent, an inner boundary of the hot component of about 1 pc, and an inner boundary of the warm component of about 20 pc.

Marshall, F. E.; Netzer, H.; Arnaud, K. A.; Boldt, E. A.; Holt, S. S.; Jahoda, K. M.; Kelley, R.; Mushotzky, R. F.; Petre, R.; Serlemitsos, P. J.

1993-01-01

12

Spectral unfolds of PITHON Flash X-ray source.  

SciTech Connect

Using a differential absorption spectrometer we obtained experimental spectral information for the PITHON Flash X-ray Machine located in San Leandro, California at L-3 Communications. Spectral information we obtained pertained to the 200 keV to 800 keV endpoint operation of PITHON. We also obtained data on the temporal behavior of high energy and low energy spectral content.

Zarick, Thomas Andrew; Sheridan, Timothy J.; Hartman, E. Frederick; Riordan, John C. (L-3 Pulse Sciences)

2007-11-01

13

The X-ray spectra of galaxies. I - Spectral fits of individual galaxies and X-ray colors  

NASA Technical Reports Server (NTRS)

The X-ray spectra of normal galaxies is investigated systematically by using the Imaging Proportional Counter (IPC) data in the Einstein data bank. In addition to the standard model fitting technique, X-ray colors are introduced in order to extract spectral information from the fainter X-ray sources. Spectral parameters for 43 galaxies and X-ray colors for 127 galaxies are presented.

Kim, D.-W.; Fabbiano, G.; Trinchieri, G.

1992-01-01

14

THE X-RAY SPECTRAL EVOLUTION OF GALACTIC BLACK HOLE X-RAY BINARIES TOWARD QUIESCENCE  

SciTech Connect

Most transient black hole X-ray binaries (BHXBs) spend the bulk of their time in a quiescent state, where they accrete matter from their companion star at highly sub-Eddington luminosities (we define quiescence here as a normalized Eddington ratio l{sub x} = L{sub 0.5-10{sub keV}}/L{sub Edd} < 10{sup -5}). Here, we present Chandra X-ray imaging spectroscopy for three BHXB systems (H 1743-322, MAXI J1659-152, and XTE J1752-223) as they fade into quiescence following an outburst. Multiple X-ray observations were taken within one month of each other, allowing us to track each individual system's X-ray spectral evolution during its decay. We compare these three systems to other BHXB systems. We confirm that quiescent BHXBs have softer X-ray spectra than low-hard-state BHXBs, and that quiescent BHXB spectral properties show no dependence on the binary system's orbital parameters. However, the observed anti-correlation between X-ray photon index ({Gamma}) and l{sub x} in the low-hard state does not continue once a BHXB enters quiescence. Instead, {Gamma} plateaus to an average ({Gamma}) = 2.08 {+-} 0.07 by the time l{sub x} reaches {approx}10{sup -5}. l{sub x} {approx} 10{sup -5} is thus an observationally motivated upper limit for the beginning of the quiescent spectral state. Our results are discussed in the context of different accretion flow models and across the black hole mass scale.

Plotkin, Richard M.; Gallo, Elena [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Jonker, Peter G., E-mail: rplotkin@umich.edu [SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht (Netherlands)

2013-08-10

15

EXSAA: Environmentally-Induced X-ray Spectral Analysis Automation  

NASA Astrophysics Data System (ADS)

X-ray fluorescence (XRF) spectrometry is one of the principal means of compositional analysis in the lab and in the field: it will be a central tool in NASA's Exploration Initiative (EI) missions. No currently available XRF software has the generic functionality to provide the basis for XRF experiment design, instrument development, and data interpretation for the suite of prospective EI missions. In response to this need, we have developed EXSAA (Environmentally-induced X-ray Spectral Analysis Automation), a generic, fast, interactive spectral simulation tool which can be used in assessing broadband continuous spectra being generated and detected during reconnaissance missions and field campaigns involving planetary surfaces. The software produces model spectra of detectable environmentally-induced X-ray spectra from fundamental principles for target characteristics and conditions likely to be experienced in remote or in situ planetary missions. Fluorescence is modeled following Jenkins and DeVries (1967); coherent and Compton scattering following Hubbell (1969). The modeling provided is extensible, and a user interface provides for selection of source, detector characteristics, compositional components, and geometry for known targets. An immediate application of the tool is the prediction for mission planning purposes of X-ray flux to be expected for a range of targets and instrumentation. A longer-term application is the model basis for the recovery of surface composition from actual missions, where some parameters (e.g. source flux) will be known, and others obtained from a Bayesian analysis of the observations. Ultimately, EXSAA could function as part of the agent-based SAA Toolkit being developed by a group of physical scientists, systems engineers, and AI practitioners to automate portions of the spectral analysis process. EXSAA could be called on by human or machine agents to provide an understanding of XRF phenomena for tasks including specifically (1) instrument and mission design and planning, or (2) model-based data analysis. Thus EXSAA could support traditional design methods and enable a variety of experiments in automated design and operation. The far term objective is to develop a toolkit for use at the human/robotic interface during exploration of lunar or Martian surfaces.

Fallon, F. W.; Clark, P. E.; Rilee, M. L.; Truszkowski, W.

2005-05-01

16

The Swift X-ray Telescope Cluster Survey III: X-ray spectral analysis  

E-print Network

(Abridged) We present a spectral analysis of a new, flux-limited sample of 72 X-ray selected clusters of galaxies identified with the X-ray Telescope (XRT) on board the Swift satellite down to a flux limit of ~10-14 erg/s/cm2 (SWXCS, Tundo et al. 2012). We carry out a detailed X-ray spectral analysis with the twofold aim of measuring redshifts and characterizing the properties of the Intra-Cluster Medium (ICM). Optical counterparts and spectroscopic or photometric redshifts are obtained with a cross-correlation with NED. Additional photometric redshifts are computed with a dedicated follow-up program with the TNG and a cross-correlation with the SDSS. We also detect the iron emission lines in 35% of the sample, and hence obtain a robust measure of the X-ray redshift zX. We use zX whenever the optical redshift is not available. Finally, for all the sources with measured redshift, background-subtracted spectra are fitted with a mekal model. We perform extensive spectral simulations to derive an empirical formul...

Tozzi, P; Tundo, E; Liu, T; Rosati, P; Borgani, S; Tagliaferri, G; Campana, S; Fugazza, D; D'Avanzo, P

2014-01-01

17

Spectral encoding of x-ray/optical relative delay.  

PubMed

We present a new technique for measuring the relative delay between a soft x-ray FEL pulse and an optical laser that indicates a sub 25 fs RMS measurement error. An ultra-short x-ray pulse photo-ionizes a semiconductor (Si(3)N(4)) membrane and changes the optical transmission. An optical continuum pulse with a temporally chirped bandwidth spanning 630 nm-710 nm interacts with the membrane such that the timing of the x-ray pulse can be determined from the onset of the spectral modulation of the transmitted optical pulse. This experiment demonstrates a nearly in situ single-shot measurement of the x-ray pulse arrival time relative to the ultra-short optical pulse. PMID:22109037

Bionta, Mina R; Lemke, H T; Cryan, J P; Glownia, J M; Bostedt, C; Cammarata, M; Castagna, J-C; Ding, Y; Fritz, D M; Fry, A R; Krzywinski, J; Messerschmidt, M; Schorb, S; Swiggers, M L; Coffee, R N

2011-10-24

18

Super-soft X-ray Spectral Evolution in Novae  

NASA Astrophysics Data System (ADS)

Swift has performed intensive monitoring of a number of novae as they pass through their super-soft X-ray phase. While Chandra and XMM-Newton can provide high-resolution grating spectra, important for identifying individual emission and absorption features and placing constraints on abundances, few observations are obtained with these instruments, thus providing only rare snapshots of the super-soft spectral evolution. With Swift, however, we can perform daily (if not hourly) monitoring, allowing us to follow the entirety of the super-soft phase in great detail. Spectral evolution is clear, often even when simply comparing the unfitted spectra. Here, we fit stellar atmosphere models to the X-ray spectra of some of the densely-observed Swift novae, investigating the evolution of temperature, emitting radius and X-ray luminosity throughout their super-soft phases.

Page, K. L.; Osborne, J. P.

2014-12-01

19

Modification of the TASMIP x-ray spectral model for the simulation of microfocus x-ray sources  

SciTech Connect

Purpose: The availability of accurate and simple models for the estimation of x-ray spectra is of great importance for system simulation, optimization, or inclusion of photon energy information into data processing. There is a variety of publicly available tools for estimation of x-ray spectra in radiology and mammography. However, most of these models cannot be used directly for modeling microfocus x-ray sources due to differences in inherent filtration, energy range and/or anode material. For this reason the authors propose in this work a new model for the simulation of microfocus spectra based on existing models for mammography and radiology, modified to compensate for the effects of inherent filtration and energy range. Methods: The authors used the radiology and mammography versions of an existing empirical model [tungsten anode spectral model interpolating polynomials (TASMIP)] as the basis of the microfocus model. First, the authors estimated the inherent filtration included in the radiology model by comparing the shape of the spectra with spectra from the mammography model. Afterwards, the authors built a unified spectra dataset by combining both models and, finally, they estimated the parameters of the new version of TASMIP for microfocus sources by calibrating against experimental exposure data from a microfocus x-ray source. The model was validated by comparing estimated and experimental exposure and attenuation data for different attenuating materials and x-ray beam peak energy values, using two different x-ray tubes. Results: Inherent filtration for the radiology spectra from TASMIP was found to be equivalent to 1.68 mm Al, as compared to spectra obtained from the mammography model. To match the experimentally measured exposure data the combined dataset required to apply a negative filtration of about 0.21 mm Al and an anode roughness of 0.003 mm W. The validation of the model against real acquired data showed errors in exposure and attenuation in line with those reported for other models for radiology or mammography. Conclusions: A new version of the TASMIP model for the estimation of x-ray spectra in microfocus x-ray sources has been developed and validated experimentally. Similarly to other versions of TASMIP, the estimation of spectra is very simple, involving only the evaluation of polynomial expressions.

Sisniega, A.; Vaquero, J. J., E-mail: juanjose.vaquero@uc3m.es [Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Madrid ES28911 (Spain); Instituto de Investigación Sanitaria Gregorio Marañón, Madrid ES28007 (Spain); Desco, M. [Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Madrid ES28911 (Spain) [Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Madrid ES28911 (Spain); Instituto de Investigación Sanitaria Gregorio Marañón, Madrid ES28007 (Spain); Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Madrid ES28029 (Spain)

2014-01-15

20

Non-periodic multilayer coatings in EUV, soft x-ray and x-ray range  

NASA Astrophysics Data System (ADS)

Non-periodic multilayer coatings offer engineer great flexibility to achieve tailored spectral performance in EUV, soft X-ray and X-ray region. We have developed a variety of non-periodic multilayer mirrors for use as optical key components for polarization-sensitive studies, Kirkpatrick-Baez microscope, Earth's magnetosphere observation and reflection of sub-femtosecond pulses. To find optimal distribution of layer thicknesses for a given spectral response, several numerical algorithms, such as simplex, simulated annealing, genetic and Levenberg Marquardt, have been explored to solve the reverse optimization problems. The designed non-periodic multilayers were prepared by use of a direct current magnetron sputtering system and characterized by grazing incidence x-ray reflectometry analysis. The synchrotron measurements of these samples were performed at the National Synchrotron Radiation Laboratory, China and at the beamline UE56/1-PGM-1 at BESSY II Berlin, Germany. This paper covers our recent results of design and fabrication of non-periodic multilayer coatings. And the mirror performance and limitations were also briefly reviewed.

Wang, Zhanshan

2008-09-01

21

ON NEUTRAL ABSORPTION AND SPECTRAL EVOLUTION IN X-RAY BINARIES  

SciTech Connect

Current X-ray observatories make it possible to follow the evolution of transient and variable X-ray binaries across a broad range in luminosity and source behavior. In such studies, it can be unclear whether evolution in the low-energy portion of the spectrum should be attributed to evolution in the source, or instead to evolution in neutral photoelectric absorption. Dispersive spectrometers make it possible to address this problem. We have analyzed a small but diverse set of X-ray binaries observed with the Chandra High Energy Transmission Grating Spectrometer across a range in luminosity and different spectral states. The column density in individual photoelectric absorption edges remains constant with luminosity, both within and across source spectral states. This finding suggests that absorption in the interstellar medium strongly dominates the neutral column density observed in spectra of X-ray binaries. Consequently, evolution in the low-energy spectrum of X-ray binaries should properly be attributed to evolution in the source spectrum. We discuss our results in the context of X-ray binary spectroscopy with current and future X-ray missions.

Miller, J. M.; Cackett, E. M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Reis, R. C., E-mail: jonmm@umich.ed [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom)

2009-12-10

22

Global X-ray Spectral Variation of Eta Carinae through the 2003 X-ray Minimum  

NASA Technical Reports Server (NTRS)

We report on the results of the X-ray observing campaign of the massive, evolved star Eta Carinae in 2003 around its recent X-ray Minimum, mainly using data from the XMM-Newton observatory. These imaging observations show that the hard X-ray source associated with the Eta Carinae system does not completely disappear in any of the observations during the Minimum. The variation of the spectral shape revealed two emission components. One newly discovered component did not exhibit any variation on kilo-second to year-long timescales, in a combined analysis with earlier ASCA and ROSAT data, and might represent the collision of a high speed outflow from Eta Carinae with ambient gas clouds. The other emission component was strongly variable in flux but the temperature of the hottest plasma did not vary significantly at any orbital phase. Absorption to the hard emission, was about a factor of three larger than the absorption determined from the cutoff of the soft emission, and reached a maximum of approx.4 x 10(exp 23)/sq cm before the Minimum. The thermal Fe\\rm XXV emission line showed significant excesses on both the red and blue sides of the line outside the Minimum and exhibited a large redward excess during the Minimum. This variation in the line profile probably requires an abrupt change in ionization balance in the shocked gas.

Hamaguchi, K.; Corcoran, M. F.; White, N. E.; Gull, T.; Damineli, A.; Davidson, K.

2006-01-01

23

[Research on spectral characteristic of miniature X-ray tube and determination of beryllium window thickness].  

PubMed

Applying Monte Carlo method, the present paper simulates the emitted X-ray spectrum of miniature X-ray tube with thirteen thickness of beryllium window in the range from 50 to 500 microm. By analyzing the characteristic of the spectrums, the reasonable choice of thickness of beryllium window relies on the application and for the beryllium window it is not the thinner the better. Taking in-situ EDXRF as an example, though the emission X-ray intensity is higher as the thickness of the beryllium window becomes thinner, the proportion of useless low-energy X-ray (<5 keV) intensity to all energy X-ray intensity also is higher (>20%). The accuracy of in-situ EDXRF will be reduced when the high-throughput low-energy X-ray enters the detector. Therefore, this paper puts forward several parameters as judgment index for beryllium window thickness, which is described as follows: 1)The intensity ratios of the K-series X-ray to middle-energy (5-25 keV) bremsstrahlung and middle-high-energy (5-50 keV) bremsstrahlung (F1 and F3); 2)The intensity ratios of useless low-energy X-ray (<5 keV) to middle-energy (5-25 keV) X-ray and middle-high-energy (5-50 keV) X-ray (F2 and F4), it can reflect the relative intensity of useless low-energy X-ray. The simulation results demonstrate that with the increase in the beryllium window thickness, the value of F1 (F3) improves slowly, and the value of F2 (F4) decreases rapidly. In addition to the judgment index discussed above, and considering the X-ray shielded by beryllium window, the beryllium window of miniature X-ray tube can be determined. Based on simulation analysis, the thickness of around 250 microm is appropriate to miniature X-ray tube applied in the in-situ EDXRF. Comparing the emitted spectrum with 50 microm-thick beryllium window, 71.66% of low-energy X-rays are shielded, only 21.31% of X-rays with energy from 5 to 50 keV is shielded, the intensity ratio of low-energy X-ray to total energy X-ray is less than 10%, and the intensity proportion of K-series X-ray to middle-high energy X-ray maintains a high level. In other words, when the mobile X-ray source with 250 microm beryllium window is used in the in-situ EDXRF, proportion of effective signal is higher, and effect of energy resolution of the detection is least; Moreover, the relative intensity of the excitation spectral scattering background, which is obtained by detection for specimen excitation analysis, will remain at low level, thus to ensure the precision of the result of element analysis. For the beryllium window in the application of radiation therapy, the thicker the better. At this time, low-energy X-ray flux maintains a high level, and it can ensure that radiation dose is concentrated on treatment tissue. PMID:24783571

Gu, Yi; Xiong, Sheng-Qing; Ge, Liang-Quan; Fan, Zheng-Guo; Zhang, Qing-Xian; Zhu, Zhen-Ya

2014-01-01

24

XSPEC: An X-ray spectral fitting package  

NASA Astrophysics Data System (ADS)

It has been over a decade since the first paper was published containing results determined using the general X-ray spectral-fitting program XSPEC. Since then XSPEC has become the most widely used program for this purpose, being the de facto standard for the ROSAT and the de jure standard for the ASCA and XTE satellites. Probably the most important features of XSPEC are the large number of theoretical models available and the facilities for adding new models.

Arnaud, Keith; Dorman, Ben; Gordon, Craig

1999-10-01

25

Soft X-ray spectral variations in Scorpius X-1  

NASA Technical Reports Server (NTRS)

Soft X-ray spectra of Scorpius X-1 obtained with the low-energy detectors of the A-2 experiment on HEAO 1 are presented. The raw count spectra are deconvolved using the Kahn and Blissett technique to reveal the presence of oxygen absorption in the range 0.5-0.7 keV. The strength of this feature is shown to vary on a time scale of order hours. These results are interpreted as evidence for variable X-ray photoionization of circumsource material in the system. An alternative model, involving variable Compton broadening of an oxygen edge, is also discussed.

Kahn, S. M.; Charles, P. A.; Bowyer, S.; Blissett, R. J.

1981-01-01

26

Spectral Modeling of X-rays from Hot Star Winds Emma E. Wollman, Swarthmore College `09  

E-print Network

1 Spectral Modeling of X-rays from Hot Star Winds Emma E. Wollman, Swarthmore College `09 Prof x-ray spectra from Chandra's archive. Models of x-ray production in hot star winds predict broad models of x-ray production. Previous explorations of the trade-offs of these two options have been

Cohen, David

27

The Extended Range X-Ray Telescope center director's discretionary fund report  

NASA Technical Reports Server (NTRS)

An Extended Range X-Ray Telescope (ERXRT) of high sensitivity and spatial resolution capable of functioning over a broad region of the X-ray/XUV portion of the spectrum has been designed and analyzed. This system has been configured around the glancing-incidence Wolter Type I X-ray mirror system which was flown on the Skylab Apollo Telescope Mount as ATM Experiment S-056. Enhanced sensitivity over a vastly broader spectral range can be realized by the utilization of a thinned, back-illuminated, buried-channel Charge Coupled Device (CCD) as the X-ray/XUV detector rather than photographic film. However, to maintain the high spatial resolution inherent in the X-ray optics when a CCD of 30 micron pixel size is used, it is necessary to increase the telescope plate scale. This can be accomplished by use of a glancing-incidence X-ray microscope to enlarge and re-focus the primary image onto the focal surface of the CCD.

Hoover, R. B.; Cumings, N. P.; Hildner, E.; Moore, R. L.; Tandberg-Hanssen, E. A.

1985-01-01

28

Spectral Properties of X-ray Binaries in Centaurus A  

E-print Network

We present a spectral investigation of X-ray binaries in NGC 5128 (Cen A), using six 100 ks Chandra observations taken over two months in 2007. We divide our sample into thermally and non-thermally dominated states based on the behavior of the fitted absorption column, and present the spectral parameters of sources with L >2x10^37 erg/s. The majority of sources are consistent with being neutron star low mass X-ray binaries (NS LMXBs) and we identify three transient black hole (BH) LMXB candidates coincident with the dust lane, which is the remnant of a small late-type galaxy. Our results also provide tentative support for the apparent `gap' in the mass distribution of compact objects between ~2-5 Msol. We propose that BH LMXBs are preferentially found in the dust lane, and suggest this is because of the younger stellar population. The majority (~70-80%) of potential Roche-lobe filling donors in the Cen A halo are >12 Gyr old, while BH LMXBs require donors >1 Msol to produce the observed peak luminosities. Thi...

Burke, Mark J; Kraft, Ralph P; Maccarone, Thomas J; Brassington, Nicola J; Hardcastle, Martin J; Kainulainen, Jouni; Woodley, Kristin A; Goodger, Joanna L; Sivakoff, Gregory R; Forman, William R; Jones, Christine; Murray, Stephen S; Birkinshaw, Mark; Croston, Judith H; Evans, Daniel A; Gilfanov, Marat; Jordan, Andres; Sarazin, Craig L; Voss, Rasmus; Worrall, Diana M; Zhang, Zhongli

2013-01-01

29

A wide dynamic range x-ray streak camera system  

SciTech Connect

An x-ray streak camera with wide dynamic range and a large slit photocathode of 30 mm length has been developed and calibrated. In order to achieve wide dynamic range, a conventional streak tube has been improved and the camera system has been designed without microchannel plate electron amplifier. As a result, a dynamic range of 922 is achieved in a single shot mode with laser pulse of 30 ps (full width at half maximum) at time resolution of better than 31 ps.

Niu Lihong; Yang Qinlao; Niu Hanben; Liao Hua; Zhou Junlan; Ding Yunkun [Institute of Optoelectronics, Shenzhen University, Guangdong 518060 (China); Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900 (China)

2008-02-15

30

Rapid X-ray spectral variability in NGC 3227  

NASA Technical Reports Server (NTRS)

We present preliminary results of an ASCA observation of the Seyfert 1 galaxy, NGC 3227. The source exhibits rapid X-ray amplitude and spectral variability, the flux below 2 keV varying by a factor of approximately 3 in approximately 10,000 s while the flux in the 2-10 keV band varies by a factor of approximately 2 in the same interval. The spectrum below approximately 1 keV shows complex structure compared to a simple power-law model. We argue that the simplest interpretation of the spectrum is in terms of a power-law continuum modified by absorption in a photoionized medium. Simple, static, ionized absorber models yield an ionization parameter of approximately 0.05 and column density approximately 3.6 x 10(exp 21)/sq cm. However, the data strongly indicate that the situation is much more complex than this. If the spectral variability is caused by a changing ionization state of the absorber, then both the ionization state and column density are required to decrease as the intrinsic source luminosity increases. This does not have a simple physical interpretation. On the other hand, the data are also consistent with the spectral variability being due to changes in the intrinsic power-law index with little change in the ionization state of the absorber. This case could correspond to an absorber which is always in some average ionization state and the continuum variability is too fast for the absorber to deviate significantly from that, or the absorber could be in the form of an X-ray-heated wind.

Ptak, A.; Yaqoob, T.; Serlemitsos, P. J.; Mushotzky, R.; Otani, C.

1994-01-01

31

The Formal Underpinnings of the Response Functions used in X-Ray Spectral John E. Davis  

E-print Network

of the instrument. The main goal of this work is to present an explicit #12;rst-principles derivation of the ARFThe Formal Underpinnings of the Response Functions used in X-Ray Spectral Analysis John E. Davis that are used for spatial and spectral analysis of X-ray data. The use of such functions is well-known to anyone

Davis, John E.

32

ISIS: Interactive Spectral Interpretation System for High Resolution X-Ray Spectroscopy  

NASA Astrophysics Data System (ADS)

ISIS, the Interactive Spectral Interpretation System, is designed to facilitate the interpretation and analysis of high resolution X-ray spectra. It is being developed as a programmable, interactive tool for studying the physics of X-ray spectrum formation, supporting measurement and identification of spectral features, and interaction with a database of atomic structure parameters and plasma emission models.

Houck, John C.; Davis, John E.; Huenemoerder, David; Dewey, Dan; Nowak, Mike; Davis, David S.

2013-02-01

33

X-ray spectral evolution of high redshift quasars  

NASA Technical Reports Server (NTRS)

At z approx. equals 3, the x-ray spectra of radio-loud and radio-quiet quasars are different. High-redshift radio-quiet quasars either have large absorbing columns, N(sub H), and steeper power law spectral indices, alpha(sub epsilon), than low redshift quasars, or no absorption and similar alpha(sub epsilon)'s. In contrast, the radio-loud quasars at high redshift have substantial absorption and similar alpha(sub epsilon)'s to low redshift quasars. Implications for the interpretation of the evolution of the luminosity function of quasars are discussed. If the absorption arises outside the central engine for both radio-loud and radio-quiet quasars, then radio-quiet quasars differ from the radio-loud quasars in that their emitted power law spectrum has evolved with redshift. We argue that this favors models where quasars are numerous and short-lived, rather than rare and long-lived.

Bechtold, Jill; Elvis, Martin; Fiore, Fabrizio; Kuhn, Olga; Cutri, Roc M.; Mcdowell, Jonathan C.; Rieke, Marcia; Siemiginowska, Aneta; Wilkes, Belinda J.

1994-01-01

34

Development of a stacked detector system for the x-ray range and its possible applications  

NASA Astrophysics Data System (ADS)

We have constructed a stacked detector system operating in the X-ray range from 0.5 keV to 250 keV that consists of a Si-based 64×64 DePFET-Matrix in front of a CdTe hybrid detector called Caliste-64. The setup is operated under laboratory conditions that approximate the expected environment of a space-borne observatory. The DePFET detector is an active pixel matrix that provides high count-rate capabilities with a near Fanolimited spectral resolution at energies up to 15 keV. The Caliste-64 hard X-ray camera consists of a 1mm thick CdTe crystal combined with very compact integrated readout electronics, constituting a high performance spectro-imager with event-triggered time-tagging capability in the energy range between 2 keV and 200 keV. In this combined geometry the DePFET detector works as the Low Energy Detector (LED) while the Caliste-64 - as the High Energy Detector (HED) - detects predominantly the high energetic photons that have passed the LED. In addition to the individual optimization of both detectors, we use the setup to test and optimize the performance of the combined detector system. Side-effects like X-ray fluorescence photons, electrical crosstalk, and mutual heating have negative impacts on the data quality and will be investigated. Besides the primary application as a combined imaging detector system with high sensitivity across a broad energy range, additional applications become feasible. Via the analysis of coincident events in both detectors we can estimate the capabilities of the setup to be used as a Compton camera and as an X-ray polarimeter - both desirable functionalities for use in the lab as well as for future X-ray missions.

Maier, Daniel; Limousin, Olivier; Meuris, Aline; Pürckhauer, Sabina; Santangelo, Andrea; Schanz, Thomas; Tenzer, Christoph

2014-07-01

35

Spectra of cosmic gamma-ray bursts in the hard X-ray range  

NASA Technical Reports Server (NTRS)

Hard X-ray measurements of six gamma-ray bursts observed by detectors on the OGO-5 and OSO-6 satellites during the period Oct. 1969 to Apr. 1971 are presented. Spectra for five of the six bursts were determined using measurements from both satellites in order to reduce ambiguities due to uncertain source locations. A significant fraction, 20 to 60%, of the energy of the bursts fall in the hard X-ray range (20 to 130 keV). The time-integrated spectra were fitted by power-law, exponential, and thermal bremsstrahlung functions. They are consistent with power-laws which steepen at energies approx. above 150 keV, as reported earlier for two other bursts. Evidence for spectral variability from event to event in the hard X-ray region is presented. The hard X-ray spectra of the gamma-ray bursts differ from those of the recently discovered 1 to 15 keV bursts.

Share, G. H.; Kane, S. R.

1977-01-01

36

X-Ray Spectral Study of the Photoionized Stellar Wind in Vela X-1  

SciTech Connect

We present results from quantitative modeling and spectral analysis of the high mass X-ray binary system Vela X-1 obtained with the Chandra High Energy Transmission Grating Spectrometer. The observations cover three orbital phase ranges within a single binary orbit. The spectra exhibit emission lines from H-like and He-like ions driven by photoionization, as well as fluorescent emission lines from several elements in lower charge states. The properties of these X-ray lines are measured with the highest accuracy to date. In order to interpret and make full use of the high-quality data, we have developed a simulator, which calculates the ionization and thermal structure of a stellar wind photoionized by an X-ray source, and performs Monte Carlo simulations of X-ray photons propagating through the wind. The emergent spectra are then computed as a function of the viewing angle accurately accounting for photon transport in three dimensions including dynamics. From comparisons of the observed spectra with results from the simulator, we are able to find the ionization structure and the geometrical distribution of material in the stellar wind of Vela X-1 that can reproduce the observed spectral line intensities and continuum shapes at different orbital phases remarkably well. We find that the stellar wind profile can be represented by a CAK-model with a star mass loss rate of (1.5-2.0) x 10{sup -6} M{sub {circle_dot}} yr{sup -1}, assuming a terminal velocity of 1100 km s{sup -1}. It is found that a large fraction of X-ray emission lines from highly ionized ions are formed in the region between the neutron star and the companion star. We also find that the fluorescent X-ray lines must be produced in at least three distinct regions: (1) the extended stellar wind, (2) reflection off the stellar photosphere, and (3) in a distribution of dense material partially covering and possibly trailing the neutron star, which may be associated with an accretion wake. Finally, from detailed analysis of the emission line profiles, we demonstrate that the stellar wind dynamics is affected by X-ray photoionization.

Watanabe, Shin; Sako, Masao; Ishida, Manabu; Ishisaki, Yoshitaka; Kahn, Steven M.; Kohmura, Takayoshi; Nagase, Fumiaki; Paerels, Frederik; Takahashi, Tadayuki; /JAXA,

2006-07-10

37

Feasibility of a spectral imager in the soft x-ray region  

NASA Astrophysics Data System (ADS)

The development of Fourier Transform (FT) spectral techniques in the soft X-ray (100eV to 500eV spectral region) has been advocated in the past as a possible route to constructing a bench-top size spectral imager with high spatial and spectral resolution. The crux of the imager is the soft X-ray interferometer. The auxiliary subsystems include a soft X-ray source, focusing optics and a CCD-based detection system. When tuned over a sufficiently large range of path delays (frames), the interferometer will sinusoidally modulate a spectrum of a wide-band X-ray source centered at the core wavelength of interest with high resolving power. The spectrum illuminates a target, the reflected signal is imaged onto a CCD, and data acquired for different frames is converted to spectra in software by using FT methods similar to those used in IR spectrometry, producing spectral image per each pixel. The use of short wavelengths results in dramatic increase in imaging resolution over that for IR. Important for future NASA missions, and unlike X-ray Absorption Near Edge Structure (XANES) that uses intense and in monochromatic beams which only a synchrotron can deliver, FTXR plans to use a miniature, wide bandwidth X-ray source. By modulating the beam spectrum around the wavelength of interest, the beam energy is used much more efficiently than with gratings (when only a very small, monochromatized portion of the radiation is used at one time) facilitating construction of a bench-top instrument. With the predicted <0.1eV spectral and <100 nm spatial resolution, the imager would be able to map a core-level shift spectrum for each pixel of the image for elements such as C, Si, Ca, N (K?-lines) which can be used as a chemical compound fingerprint and for imaging intracellular structures. For heavy elements it could provide "bonding maps" (L and M-shell lines), enabling to study fossils of microorganisms on space missions and in returned samples to Earth. We have initiated development of a Fourier Transform X-ray Reflection (FTXR) spectral imager based on the use of a Mach-Zender type interferometer. The enabling technology for the interferometer is the X-ray beam splitting mirrors. The mirrors are not available commercially; multi layers of quarter-wave films are not suitable, requiring a different approach to beam-splitters than in the visible or IR regions. Several efforts by other researchers used parallel slits or stripes for partial transmission, with only a very limited success. In contrast, our beam splitters are based on thin (about 200 nm) SiN membranes perforated with a large number of very small holes, prepared using state-of-art microfabrication techniques that have only recently become available in our laboratory at JPL. Precise control of surface roughness and high planarity are needed to achieve the wave coherency required for high-contrast fringe forming. The perforation design is expected to result in much greater surface flatness, facilitating greater wave coherence than for the other techniques. We report on our progress in the fabrication of beam splitting mirrors to-date, interferometer design, modeling, assembly, and experimental results.

Wilcox, Jaroslava; White, Victor; Shcheglov, Kirill

2009-05-01

38

SPECTRAL SURVEY OF X-RAY BRIGHT ACTIVE GALACTIC NUCLEI FROM THE ROSSI X-RAY TIMING EXPLORER  

SciTech Connect

Using long-term monitoring data from the Rossi X-ray Timing Explorer (RXTE), we have selected 23 active galactic nuclei (AGNs) with sufficient brightness and overall observation time to derive broadband X-ray spectra from 3 to {approx}>100 keV. Our sample includes mainly radio-quiet Seyferts, as well as seven radio-loud sources. Given the longevity of the RXTE mission, the greater part of our data is spread out over more than a decade, providing truly long-term average spectra and eliminating inconsistencies arising from variability. We present long-term average values of absorption, Fe line parameters, Compton reflection strengths, and photon indices, as well as fluxes and luminosities for the hard and very hard energy bands, 2-10 keV and 20-100 keV, respectively. We find tentative evidence for high-energy rollovers in three of our objects. We improve upon previous surveys of the very hard X-ray energy band in terms of accuracy and sensitivity, particularly with respect to confirming and quantifying the Compton reflection component. This survey is meant to provide a baseline for future analysis with respect to the long-term averages for these sources and to cement the legacy of RXTE, and especially its High Energy X-ray Timing Experiment, as a contributor to AGN spectral science.

Rivers, Elizabeth; Markowitz, Alex; Rothschild, Richard, E-mail: erivers@ucsd.edu [University of California, San Diego, Center for Astrophysics and Space Sciences, 9500 Gilman Dr., La Jolla, CA 92093-0424 (United States)

2011-03-15

39

Spectral and Temporal Characteristics of X-Ray-Bright Stars in the Pleiades  

NASA Technical Reports Server (NTRS)

We follow up our deep ROSAT imaging survey of the Pleiades (Stauffer et al. 1994) with an analysis of the spectral and temporal characteristics of the X-ray-bright stars in the Pleiades. Raymond & Smith (1977) one and two-temperature models have been used to fit the position-sensitive proportional counter (PSPC) pulse-height spectra of the dozen or so brightest sources associated with late-type Pleiades members. The best-fit temperatures suggest hot coronal temperatures for K, M, and rapidly rotating G stars, and cooler temperatures for F and slowly rotating G stars. In order to probe the many less X-ray-luminous stars, we have generated composite spectra by combining net counts from all Pleiades members according to spectral type and rotational velocity. Model fits to the composite spectra confirm the trend seen in the individual spectral fits. Particularly interesting is the apparent dependence of coronal temperature on L(sub x)/L(sub bol). A hardness-ratio analysis also confirms some of these trends. The PSPC data have also revealed a dozen or so strong X-ray flares with peak X-ray luminosities in excess of approx. 10(exp 30) ergs/sec. We have modeled the brightest of these flares with a simple quasi-static cooling loop model. The peak temperature and emission measure and the inferred electron density and plasma volume suggest a very large scale flaring event. The PSPC data were collected over a period of approx. 18 months, allowing us to search for source variability on timescales ranging from less than a day (in the case of flares) to more than a year between individual exposures. On approximately year-long timescales, roughly 25% of the late-type stars are variable. Since the Pleiades was also intensively monitored by the imaging instruments on the Einstein Observatory, we have examined X-ray luminosity variations on the 10 yr timescale between Einstein and ROSAT and find that up to 40% of the late-type stars are X-ray variable. Since there is only marginal evidence for increased variability on decade-long timescales, the variability observed on long and short timescales may have a common physical origin.

Gagne, Marc; Caillault, Jean-Pierre; Stauffer, John R.

1995-01-01

40

X-ray emission from A0-F6 spectral type stars  

Microsoft Academic Search

We use the ROSAT public data archive to study the X-ray emission of a sample of supposedly single A0-F6 spectral type stars from the Bright Star Catalogue. We detected X-ray emission from 19 A- and 33 F-type stars. However, our results are not sufficient to associate with certainty the X-ray emission to the A-type stars themselves, since the usual argument

M. R. Panzera; G. Tagliaferri; L. Pasinetti; E. Antonello

1999-01-01

41

Small, Fast TES Microcalorimeters with Unprecedented X-ray Spectral Performance  

NASA Technical Reports Server (NTRS)

Driven initially by the desire for X-ray microcalorimeter arrays suitable for imaging the dynamic solar corona, we have developed a transition-edge-sensor (TES) microcalorimeter optimization that exhibits a unique combination of high spectral resolving power and a wide X-ray bandpass. These devices have achieved spectral performance of dE approximately 1.3 eV FWHM at 1.5 keV, 1.6 eV at 6 keV, and 2.0 eV at 8 keV, using small TESs (e.g., approximately 35 micron x 35 micron) that operate in a regime in which the superconducting transition is highly current dependent. In order to accommodate high X-ray count rates, the devices sit directly on a solid substrate instead of on membranes, and we use an embedded heatsinking layer to reduce pixel-to-pixel crosstalk. We will present results from devices with a range of TES and absorber sizes, and from device wafers with varied embedded heatsink materials. This contribution will focus on count-rate capabilities, including a discussion of the trade-off between count rate and energy resolution, and the heatsinking design. We will also present preliminary tests of array readout using a code-division multiplexed SQUID readout scheme, which may be necessary to enable large arrays of these fast devices.

Eckart, M. E.; Adams, J. S.; Bailey, C. N.; Bandler, S. R.; Chervenak, J. A.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.; Sadleir, J. E.; Smith, S. J.; Hilton, G. C.; Irwin, K. D.; Vale, L. R.

2011-01-01

42

Nonthermal X-ray Spectral Flattening toward Low Energies in Early Impulsive Flares  

NASA Technical Reports Server (NTRS)

The determination of the low-energy cutoff to nonthermal electron distributions is critical to the calculation of the nonthermal energy in solar flares. The most direct evidence for low-energy cutoffs is flattening of the power-law, nontherma1 X-ray spectra at low energies. However, because of the plasma preheating often seen in flares, the thermal emissions at low energies may hide such spectral flattening of the nonthermal component. We select a category of flares, which we call "early impulsive flares", in which the > 25 keV hard X-ray (HXR) flux increase is delayed by less than 30 s after the flux increase at lower energies. Thus, the plasma preheating in these flares is minimal, so the nonthermal spectrum can be determined to lower energies than in flares with significant preheating. Out of a sample of 33 early impulsive flares observed by the Ramaty High Energy Solar Spectroscopy Imager (RHESSI), 9 showed spectral flattening toward low energies. In these events, the break energy of the double power-law fit to the HXR spectra lies in the range of 10-50 keV, significantly lower than the value we have seen for other flares that do not show such early impulsive emissions. In particular, it correlates with the HXR flux. After correcting the spatially-integrated spectra for albedo from isotropically emitted X-rays and using RHESSI imaging spectroscopy to exclude the extended albedo halo, we find that albedo associated with isotropic or nearly isotropic electrons can only account for the spectral flattening in 3 flares near Sun center. The spectral flattening in the remaining 6 flares is found to be consistent with the existence of a low-energy cutoff in the electron spectrum, falling in the range of 15-50 keV, which also correlates with the HXR flux.

Holman, Gordon D.

2007-01-01

43

Spectral features in solar hard x-ray and radio events and particle acceleration  

Microsoft Academic Search

Hard x-ray and radio intensities of two major solar outbursts are found to anticorrelate in time with their spectral indices, which, furthermore, are in satisfactory correlation with each other. The radio emission must be synchrotron radiation from the same electron population that causes the x-ray bremsstrahlung. A delay of temporal features, increasing with energy, is clearly observed in one of

A. O. Benz

1977-01-01

44

X-ray Spectral Classification of Chandra Orion Ultradeep Project (COUP) Sources  

NASA Astrophysics Data System (ADS)

The Chandra X-ray Observatory is producing images with outstanding spatial resolution using low-noise, fast-readout CCDs. Techniques than can objectively and efficiently classify X-ray sources in large images of rich fields of sources are needed to analyze the growing Chandra image archive. One such dataset, the Chandra Orion Ultradeep Project (COUP) dataset, was compiled from an 850 ks Chandra observation of the Orion Nebula Cluster (ONC). It represents the most sensitive and comprehensive description of X-ray emission from a pre-main sequence star cluster (Getman et al. 2005, ApJS, 160, 000). A statistical image processing algorithm has been developed that groups the ONC X-ray sources into classes based on their spectral attributes. The algorithm was applied to a subset of 444 of the 1616 X-ray sources detected in the COUP dataset, resulting in sets of distinct X-ray spectral classes. The X-ray class membership for each of the remaining approximately 1150 COUP sources was then predicted, using the X-ray class definitions obtained from running the algorithm on the initial training subset. Our results show that ONC and extragalactic X-ray sources can potentially be distinguished via this classification method. In addition, there are clear correlations between the softer X-ray spectral classes and classical optical spectral types in the cluster H-R diagram. This research is supported by NASA under AISRP award number NNG04GQ07G and Chandra Award Number AR5-6004X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for an on behalf of NASA under contract NAS8-03060.

Hojnacki, S. M.; Kastner, J. H.; LaLonde, S. M.; Micela, G.; Feigelson, E. D.

2005-12-01

45

The X-Ray Spectral Analysis of Dwarf Nova WZ Sge Observed with ROSAT in Quiescence  

NASA Astrophysics Data System (ADS)

X-ray spectral parameters were determined for WZ Sge observed with the ROSAT PSPC. The raw data were fitted with various spectral models and the best fit spectral models are found to be that of Raymond-Smith and Thermal Bremsstrahlung. The best fit temperature was estimated to be kT ~ 2.17 keV while the column density was found to be NH ~ 2.8 × 1020 cm-2. The estimated 0.1-2.4 keV flux was in the range of log F = -12 ergs cm-2 s-1. WZ Sge stars show long outburst recurrence times and weak X-ray emissions during the quiescence states. It is possible to lengthen repetition cycles by decreasing the viscosity parameter (?) however there still remains the question why ? is so small, specifically for these objects. The Coronal Siphon Model of Meyer and Meyer-Hofmeister1 can explain these phenomenons successfully. For this reason, the equations of this model were applied to the results of spectral analysis. Using this model, the mass accretion rate, mass evaporation rate in corona and the radius of the corona were calculated to be 1014.48 gr yr-1, 10-5.4 gr cm-2 s-1 and 109.7 cm, respectively. The obtained values suggest that the corona model can indeed operate in WZ Sge system.

Gün, Gülnur Ikis

46

Spectral Properties of Blazars. II. an X-Ray Observed Sample  

NASA Astrophysics Data System (ADS)

All the blazars observed in X-rays in various reference lists and all those belonging to X-ray selected samples are considered. It is found that X-ray selected objects have, on average, radio (5 GHz) to ultraviolet (2500 Å) and ultraviolet to X-ray (2 keV) spectral indices significantly flatter than radio-selected objects. The monochromatic luminosity distributions show that X-ray selected and radio-selected blazars have the same average X-ray luminosity, and that the X-ray selected ones are underluminous at ultraviolet and radio frequencies. It is argued that the objects with flat overall spectrum, which may be called radio-weak, discovered from X-ray searches are the dominant members of the blazar population in terms of space density, while radio-loud blazars with the same X-ray luminosity are a minority. The results are interpreted in the framework of a model where the X-ray emission is isotropic, while that at lower frequencies is relativistically beamed. Radio-loud blazars should be those with the beam pointing towards us.

Maraschi, L.; Ghisellini, G.; Tanzi, E. G.; Treves, A.

1986-11-01

47

Photon counting spectral CT: improved material decomposition with K-edge-filtered x-rays.  

PubMed

Photon counting spectral computed tomography (PCSCT) provides material selective CT imaging at a single CT scan and fixed tube voltage. The PCSCT data are acquired in several energy ranges (bins) arranged over the x-ray spectrum. The quasi-monoenergetic CT images are acquired in these energy bins and are used for material decomposition. The PCSCT exhibits inherent limitations when material decomposition is performed using energy bins. For effective material decomposition, the energy bins used for material decomposition should be sufficiently narrow and well separated. However, when narrow bins are used, a large fraction of the detected x-ray counts is lost and statistical noise is increased. Alternatively, the x-ray spectrum can be split into a few larger bins with no gap in between and all detected x-ray photons can be used for material decomposition. However, in this case the energy bins are too wide and not well separated, which results in suboptimal material decomposition. The above contradictory requirements can be resolved if the x-ray photons are physically removed from the regions of the energy spectrum between the energy bins. Such a selective removal can be performed using filtration of the x-ray beam by high-Z filter materials with appropriate positions of K-edge energies. The K-edge filtration of x-rays can, therefore, provide necessary gaps between the energy bins with no dose penalty to the patient. In the current work, we proposed using selective K-edge filtration of x-rays in PCSCT and performed the first experimental investigation of this approach. The PCSCT system included a cadmium zinc telluride semiconductor detector with 2 × 256 pixels and 1 × 1 mm(2) pixel size, and five energy bins. The CT phantom had 14 cm diameter and included contrast elements of iodine, gold and calcifications with clinically relevant concentrations. The tube voltages of 60, 90 and 120 kVp were used. K-edge filters based on Ba (E(k) = 37.44 keV) were used for a 60 kVp tube voltage and Gd (E(k) = 50.24 keV) was used for the 90 and 120 kVp tube voltages, respectively. The material selective CT images were also acquired with conventional Al filtration for comparison. The half-value layers of x-ray beams after K-edge and Al filtration were matched. The mean entrance skin exposure was 280 mR for all tube voltages and filters. The contrast-to-noise ratio (CNR) in material-decomposed images was approximately 30%-50% higher when K-edge filters were used instead of Al filters. It was concluded that K-edge filtration of x-rays provides substantial improvement of the CNR in material-selective PCSCT. Further optimization of K-edge filter materials, tube voltages, detector technology and energy bin settings will provide even higher CNR in decomposed images. PMID:22398007

Shikhaliev, Polad M

2012-03-21

48

X-ray flux related timing and spectral features of 2S 1417-62  

NASA Astrophysics Data System (ADS)

Rossi X-ray Timing Explorer (RXTE) observations of the X-ray transient pulsar 2S 1417 - 62 between 1999 November and 2000 August with a total exposure of ~394 ks have been analysed. Observations include a main outburst followed by a series of mini outbursts. Changes in pulse morphology and pulse fraction were found to be related to the changes in X-ray flux. Particularly low X-ray flux regions were found to have significantly lower pulse fractions with different pulse morphologies. The 3-60 keV Proportional Counter Array (PCA) High-Energy X-ray Timing Experiment (HEXTE) main outburst spectrum was modelled with an absorbed power-law model with high-energy cut-off and a Gaussian iron line complex feature. Using the same spectral model, individual 3-20 keV PCA spectra were found to be softer and less absorbed in low X-ray flux regions between outbursts. Spectral studies showed that hydrogen column density was correlated, and the power-law index was anticorrelated with the 3-20 keV X-ray flux. X-ray flux related spectral and timing features in 2S 1417 - 62, except for low X-ray flux regions, were interpreted as a sign of disc accretion with a similar accretion geometry with a varying mass accretion rate (), whereas spectral and timing features of the low X-ray flux regions were interpreted as a sign of possible temporary accretion geometry change prior to the next periastron where increases again to restore the original accretion geometry.

?nam, S. Ça?da?; Baykal, Altan; Matthew Scott, D.; Finger, Mark; Swank, Jean

2004-03-01

49

The spectral archive of cosmic X-ray sources observed by the Einstein Observatory Focal Plane Crystal Spectrometer  

NASA Technical Reports Server (NTRS)

The Einstein Observatory Focal Plane Crystal Spectrometer (FPCS) used the technique of Bragg spectroscopy to study cosmic X-ray sources in the 0.2-3 keV energy range. The high spectral resolving power (E/Delta-E is approximately equal to 100-1000) of this instrument allowed it to resolve closely spaced lines and study the structure of individual features in the spectra of 41 cosmic X-ray sources. An archival summary of the results is presented as a concise record the FPCS observations and a source of information for future analysis by the general astrophysics community. For each observation, the instrument configuration, background rate, X-ray flux or upper limit within the energy band observed, and spectral histograms are given. Examples of the contributions the FPCS observations have made to the understanding of the objects observed are discussed.

Lum, Kenneth S. K.; Canizares, Claude R.; Clark, George W.; Coyne, Joan M.; Markert, Thomas H.; Saez, Pablo J.; Schattenburg, Mark L.; Winkler, P. F.

1992-01-01

50

Unveiling Obscured AGN with X-ray Spectral Analysis  

NASA Astrophysics Data System (ADS)

With the recent advent of physically motivated, self-consistent X-ray models, the circumnuclear medium enshrouding AGN can now be investigated in unprecedented detail. We applied these models to 19 SDSS [OIII] 5007 Angstrom selected Type 2 AGN, where 9 are local Seyfert 2 galaxies and 10 are more luminous and distant Type 2 quasars. For the first time in a sample of AGN, we constrained both the line-of-sight and global column densities, finding that over half (11/19) are heavily obscured or Compton-thick (NH > 10^23 cm^-2). Four objects have different global from line-of-sight column densities. When correcting the observed X-ray luminosities for obscuration, the L_x/L_[OIII] ratio for these Type 2 AGN is essentially identical to the Seyfert 1 (i.e., unabsorbed AGN) value, which is consistent with both parameters cleanly probing AGN emission.

LaMassa, Stephanie M.; Yaqoob, Tahir; Ptak, Andrew; Jia, Jianjun; Heckman, Timothy M.; Gandhi, Poshak; Urry, C. Megan

2014-06-01

51

TW Hya: SPECTRAL VARIABILITY, X-RAYS, AND ACCRETION DIAGNOSTICS  

SciTech Connect

The nearest accreting T Tauri star, TW Hya was intensively and continuously observed over {approx}17 days with spectroscopic and photometric measurements from four continents simultaneous with a long segmented exposure using the Chandra satellite. Contemporaneous optical photometry from WASP-S indicates a 4.74 day period was present during this time. The absence of a similar periodicity in the H{alpha} flux and the total X-ray flux which are dominated by accretion processes and the stellar corona, respectively, points to a different source of photometric variations. The H{alpha} emission line appears intrinsically broad and symmetric, and both the profile and its variability suggest an origin in the post-shock cooling region. An accretion event, signaled by soft X-rays, is traced spectroscopically for the first time through the optical emission line profiles. After the accretion event, downflowing turbulent material observed in the H{alpha} and H{beta} lines is followed by He I ({lambda}5876) broadening near the photosphere. Optical veiling resulting from the heated photosphere increases with a delay of {approx}2 hr after the X-ray accretion event. The response of the stellar coronal emission to an increase in the veiling follows {approx}2.4 hr later, giving direct evidence that the stellar corona is heated in part by accretion. Subsequently, the stellar wind becomes re-established. We suggest a model that incorporates the dynamics of this sequential series of events: an accretion shock, a cooling downflow in a supersonically turbulent region, followed by photospheric and later, coronal heating. This model naturally explains the presence of broad optical and ultraviolet lines, and affects the mass accretion rates determined from emission line profiles.

Dupree, A. K.; Brickhouse, N. S.; Cranmer, S. R.; Luna, G. J. M.; Schneider, E. E. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Bessell, M. S. [Australian National Observatory, Mount Stromlo Observatory, Canberra, ACT 2611 (Australia); Bonanos, A. [Institute of Astronomy and Astrophysics, National Observatory of Athens, 15236 Athens (Greece); Crause, L. A. [South African Astronomical Observatory, P.O. Box 9, Observatory 7935, Cape Town (South Africa); Lawson, W. A. [School of Physical, Environmental, and Math Sciences, University of New South Wales, Canberra, ACT 2600 (Australia); Mallik, S. V. [Indian Institute of Astrophysics, Bangalore 560034 (India); Schuler, S. C. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)

2012-05-01

52

Do X-ray Binary Spectral State Transition Luminosities Vary?  

E-print Network

We tabulate the luminosities of the soft-to-hard state transitions of all X-ray binaries for which there exist good X-ray flux measurements at the time of the transition, good distance estimates, and good mass estimates for the compact star. We show that the state transition luminosities are at about 1-4% of the Eddington rate, markedly smaller than those typically quoted in the literature, with a mean value of 2%. Only the black hole candidate GRO J~1655-40 and the neutron star systems Aql X-1 and 4U 1728-34 have measured state transition luminosities inconsistent with this value at the 1$\\sigma$ level. GRO J~1655-40, in particular, shows a state transition luminosity below the mean value for the other sources at the $4\\sigma$ level. This result, combined with the known inner disk inclination angle (the disk is nearly parallel to the line of sight) from GRO J~1655-40's relativistic jets suggest that the hard X-ray emitting region in GRO J~1655-40 can have a velocity of no more than about $\\beta=0.68$, with a most likely value of about $\\beta=0.52$, and a minimum speed of $\\beta=0.45$, assuming that the variations in state transition luminosities are solely due to relativistic beaming effects. The variance in the state transition luminosities suggests an emission region with a velocity of $\\sim0.2c$. The results are discussed in terms of different emission models for the low/hard state. We also discuss the implications for measuring the dimensionless viscosity parameter $\\alpha$. We also find that if its state transitions occur at typical luminosities, then GX 339-4 is likely to be at a distance of at least 7.6 kpc, much further than typically quoted estimates.

Thomas J. Maccarone

2003-08-02

53

Toward a New Spectral Modeling Capability for Accreting X-Ray Pulsars  

NASA Astrophysics Data System (ADS)

Spectral modeling of accreting X-ray pulsars can tell us a great deal about the physical conditions in and near the neutron star compact objects in high mass X-ray binary systems. In such systems the accreting plasma is initially channeled from an accretion disk by the strong neutron star magnetic field into a funneled supersonic flow onto the magnetic polar cap of the neutron star. Many of these accreting X-ray pulsars have X-ray spectra that consist of broadband Comptonized power-law X-ray continua with superposed cyclotron resonant scattering features indicating magnetic field strengths above 10^12 G. We are undertaking a new program to develop a spectral analysis tool based on the analytical work of Becker & Wolff (2007) for accreting X-ray pulsar spectra inside the XSPEC spectral analysis framework. We will apply this new analysis tool to the large amount of data on numerous bright accreting X-ray pulsars currently residing in the HEASARC archive. In this presentation we discuss the physical processes that are likely to occur in such a flow and how one might self-consistently model the broadband pulsar X-ray spectrum. A previous attempt at developing such a modeling capability made significant contributions to the understanding of one source in particular, namely, 4U0115+634 (Ferrigno et al. 2010) and we expect to build on that success. Our models will incorporate bremsstrahlung emission, black body emission, and cyclotron emission, all in a strongly Comptonizing environment inside the shock-heated accreting plasma. We will discuss how we will include these physical processes in the calculations as well as the algorithm such a tool will use to converge to a solution. This program is both feasible and timely in light of the expected launch of the LOFT X-ray timing mission. This research is supported by the NASA Astrophysical Data Analysis Program and the Office of Naval Research.

Wolff, Michael T.; Becker, P. A.; Marcu, D.; Pottschmidt, K.; Wilms, J.; Wood, K. S.

2013-04-01

54

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

PubMed

Compton side-scattering has been used to simultaneously downshift the energy of keV to MeV energy range photons while attenuating their flux to enable single-shot, spectrally resolved, measurements of high flux X-ray sources to be undertaken. To demonstrate the technique a 1 mm thick pixelated cadmium telluride detector has been used to measure spectra of Compton side-scattered radiation from a Cobalt-60 laboratory source and a high flux, high peak brilliance X-ray source of betatron radiation from a laser-plasma wakefield accelerator. PMID:24289391

Cipiccia, S; Wiggins, S M; Maneuski, D; Brunetti, E; Vieux, G; Yang, X; Issac, R C; Welsh, G H; Anania, M; Islam, M R; Ersfeld, B; Montgomery, R; Smith, G; Hoek, M; Hamilton, D J; Lemos, N R C; Symes, D R; Rajeev, P P; Shea, V O; Dias, J M; Jaroszynski, D A

2013-11-01

55

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

SciTech Connect

Compton side-scattering has been used to simultaneously downshift the energy of keV to MeV energy range photons while attenuating their flux to enable single-shot, spectrally resolved, measurements of high flux X-ray sources to be undertaken. To demonstrate the technique a 1 mm thick pixelated cadmium telluride detector has been used to measure spectra of Compton side-scattered radiation from a Cobalt-60 laboratory source and a high flux, high peak brilliance X-ray source of betatron radiation from a laser-plasma wakefield accelerator.

Cipiccia, S.; Wiggins, S. M.; Brunetti, E.; Vieux, G.; Yang, X.; Welsh, G. H.; Anania, M.; Islam, M. R.; Ersfeld, B.; Jaroszynski, D. A. [Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG (United Kingdom)] [Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG (United Kingdom); Maneuski, D.; Montgomery, R.; Smith, G.; Hoek, M.; Hamilton, D. J.; Shea, V. O. [Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)] [Scottish Universities Physics Alliance, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Issac, R. C. [Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG (United Kingdom) [Scottish Universities Physics Alliance, Department of Physics, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow G4 0NG (United Kingdom); Research Department of Physics, Mar Athanasius College, Kothamangalam 686666, Kerala (India); Lemos, N. R. C.; Dias, J. M. [GoLP/Instituto de Plasmas eFusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal)] [GoLP/Instituto de Plasmas eFusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal); Symes, D. R. [Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, OX11 0QX Didcot (United Kingdom)] [Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, OX11 0QX Didcot (United Kingdom); and others

2013-11-15

56

Spectral properties, generation order parameters and luminosities for spin-powered X-ray pulsars  

E-print Network

We show the spectral properties of 15 spin-powered X-ray pulsars, and the correlation between the average power-law photon index and spin-down rate. Generation order parameters (GOPs) based on polar-cap models are introduced to characterize the X-ray pulsars. We calculate three definitions of generation order parameters due to the different effects of magnetic and electric fields on photon absorption during cascade processes, and study the relations between the GOPs and spectral properties of X-ray pulsars. There exists a possible correlation between the photon index and GOP in our pulsar sample. Furthermore, we present a method due to the concept of GOPs to estimate the non-thermal X-ray luminosity for spin-powered pulsars. Then X-ray luminosity is calculated in the context of our polar-cap accelerator model which is well consistent with the most observed X-ray pulsar data. The ratio between X-ray luminosity estimated by our method and the pulsar's spin-down power is well consistent with the $L_{\\rm X}\\sim 10^{-3}L_{\\rm sd}$ feature.

W. Wang; Y. Zhao

2003-10-06

57

X-Ray Spectral Behavior of the Relativistic Jet Source Cygnus X-3  

NASA Technical Reports Server (NTRS)

Cyg X-3 is an unusual X-ray binary which shows remarkable correlative behavior between the hard X-ray, soft X-ray, and the radio. We present an analysis of these long term light curves in the context of spectral changes of the system. This analysis will also incorporate a set of pointed RXTE observations made during a period when Cyg X-3 made a transition from a quiescent radio state to a flaring state (including a major flare) and then returned to a quiescent radio state.

McCollough, M. L.; Robinson, C. R.; Zhang, S. N.; Harmon, B. A.; Paciesas, W. S.; Dieters, S.; Phengchamnan, S.; Hjellming, R. M.; Rupen, M.; Mioduszewski, A. J.; Waltman, E. B.; Ghigo, F. D.; Pooley, G. G.; Fender, R. P.; Cui, W.; Trushkin, S.

1998-01-01

58

X-ray Flux Related Timing and Spectral Features of 2S 1417-62  

E-print Network

RXTE observations of the X-ray transient pulsar 2S 1417-62 between 1999 November and 2000 August with a total exposure of $\\sim 394$ ksec were analyzed. Observations include a main outburst followed by a series of mini outbursts. Changes in pulse morphology and pulse fraction were found to be related to the changes in X-ray flux. Particularly low X-ray flux regions were found to have significantly lower pulse fractions with different pulse morphologies. The 3-60 keV PCA-HEXTE main outburst spectrum was modeled with an absorbed power law model with high energy cut-off and a Gaussian Iron line complex feature. Using the same spectral model, individual 3-20 keV PCA spectra were found to be softer and less absorbed in low X-ray flux regions between outbursts. Spectral studies showed that hydrogen column density was correlated, and the power law index was anti-correlated with the 3-20 keV X-ray flux. X-ray flux related spectral and timing features in 2S 1417-62 except for low X-ray flux regions were interpreted as a sign of disc accretion with a similar accretion geometry with a varying mass accretion rate ($\\dot{M}$), whereas spectral and timing features of the low X-ray flux regions were interpreted as a sign of possible temporary accretion geometry change prior to the next periastron where $\\dot{M}$ increases again to restore the original accretion geometry.

S. C. Inam; A. Baykal; D. M. Scott; M. Finger; J. Swank

2003-12-02

59

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters  

NASA Astrophysics Data System (ADS)

Context. In the fallback disk model for the persistent emission of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), the hard X-ray emission arises from bulk- and thermal Comptonization of bremsstrahlung photons, which are generated in the accretion column. The relatively low X-ray luminosity of these sources implies a moderate transverse optical depth to electron scattering, with photons executing a small number of shock crossings before escaping sideways. Aims: We explore the range of spectral shapes that can be obtained with this model and characterize the most important parameter dependencies. Methods: We use a Monte Carlo code to study the crisscrossing of photons in a radiative shock in an accretion column and compute the resulting spectrum. Results: As expected, high-energy power-law X-ray spectra are produced in radiative shocks with photon-number spectral index ? ? 0.5. We find that the required transverse optical depth is 1 ? ?? ? 7. Such spectra are observed in low-luminosity X-ray pulsars. Conclusions: We demonstrate here with a simple model that Compton upscattering in the radiative shock in the accretion column can produce hard X-ray spectra similar to those seen in the persistent and transient emission of AXPs and SGRs. In particular, one can obtain a high-energy power-law spectrum, with photon-number spectral-index ? ~ 1 and a cutoff at 100 - 200 keV, with a transverse Thomson optical depth of ~5, which is shown to be typical in AXPs/SGRs.

Kylafis, N. D.; Trümper, J. E.; Ertan, Ü.

2014-02-01

60

XSPEC: An x ray spectral fitting package. Version 2 of the user's guide  

NASA Technical Reports Server (NTRS)

The user guide for XSPEC, a command driven, interactive, X-ray spectral fitting program is presented. It is designed to be completely detector independent so it can be used for any X-ray spectral instrument. An overview of the program commands and a walk through of an XSPEC session is presented. Individual commands and descriptions of the spectral models are given. For the more experienced user details of some of the programs associated with XSPEC, the command parser, and the addition of models to XSPEC are included. The PLT plotting package used by XSPEC is described together with the maximum likelihood option for users possessing X-ray spectra with small numbers of counts per bin. Details on the various files used by XSPEC and on the general file structure are also given.

Shafer, R. A.; Haberl, F.; Arnaud, K. A.; Tennant, A. F.; Barron, Chris (editor)

1991-01-01

61

Spectrally resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography  

PubMed Central

The nanophosphors, or other similar materials, emit near-infrared (NIR) light upon x-ray excitation. They were designed as optical probes for in vivo visualization and analysis of molecular and cellular targets, pathways, and responses. Based on the previous work on x-ray fluorescence computed tomography (XFCT) and x-ray luminescence computed tomography (XLCT), here we propose a spectrally-resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography (SXLCT or SXFCT) approach to quantify a spatial distribution of nanophosphors (other similar materials or chemical elements) within a biological object. In this paper, the x-ray scattering is taken into account in the reconstruction algorithm. The NIR scattering is described in the diffusion approximation model. Then, x-ray excitations are applied with different spectra, and NIR signals are measured in a spectrally resolving fashion. Finally, a linear relationship is established between the nanophosphor distribution and measured NIR data using the finite element method and inverted using the compressive sensing technique. The numerical simulation results demonstrate the feasibility and merits of the proposed approach. PMID:21721815

Cong, Wenxiang; Shen, Haiou; Wang, Ge

2011-01-01

62

X-Ray Spectral Parameters for a Sample of 95 Active Galactic Nuclei  

E-print Network

We present a broadband X-ray analysis of a new homogeneous sample of 95 active galactic nuclei (AGN) from the 22-month Swift/BAT all-sky survey. For this sample we treated jointly the X-ray spectra observed by XMM-Newton and INTEGRAL missions for the total spectral range of 0.5-250 keV. Photon index \\Gamma, relative reflection R, equivalent width of Fe $K_{\\alpha}$ line (EW Fe $K_{\\alpha}$), hydrogen column density $N_{H}$, exponential cut-off energy $E_{c}$ and intrinsic luminosity $L_{corr}$ are determined for all objects of the sample. We investigated correlations \\Gamma - R, EW Fe $K_{\\alpha}$ - $L_{corr}$, \\Gamma - $E_{c}$, EW Fe $K_{\\alpha}$ - $N_{H}$. Dependence \\Gamma - R for Seyfert 1 and 2 type of galaxies has been investigated separately. We found that the relative reflection parameter at low power-law indexes for Seyfert 2 galaxies is systematically higher than for Seyfert 1 ones. This can be related to an increasing contribution of the reflected radiation from the gas-dust torus. Our data show th...

Vasylenko, A; Fedorova, E

2015-01-01

63

X-ray Spectral Variability of TeV Blazars during Rapid Flares  

E-print Network

The spectral energy distribution (SED) of TeV blazars peaks both at keV and TeV energies. The X-ray emission is generally believed to originate in the synchrotron emission from relativistic electrons (and positrons) in the jet of these sources, while the origin of the gamma-ray emission is still being debated. We report results from a systematic study of X-ray spectral variability of Mrk 421 and Mrk 501 during individual flares that last for several days, making use of some of the high-quality data that have recently become available. The X-ray spectra of the two sources fall on the opposite sides of the synchrotron peak of their respective SEDs, so they together may offer additional insights into the physical origin of X-ray variability. We modeled each of the time-resolved X-ray spectra over a {\\em single} flare by adopting a homogeneous spatial distribution and an instantaneous power-law spectral distribution for the emitting particles. We focused on the variation of four key parameters: particle spectral index, maximum Lorentz factor, energy density, and magnetic field. While there is considerable degeneracy in the fits, we show that, in order to account for the X-ray spectral variability observed in Mrk 421, at least three of the parameters are required to vary in most cases, with the spectral index being one of them. The observations of Mrk 501 support the conclusion, although the quality of the data is not as good. We discuss the implications of the results.

Yongquan Xue; Feng Yuan; Wei Cui

2006-05-08

64

The X-ray Spectral Evolution of eta Carinae as Seen by ASCA  

NASA Technical Reports Server (NTRS)

Using data from the ASCA X-ray observatory, we examine the variations in the X-ray spectrum of the supermassive star nu Carinae with an unprecedented combination of spatial and spectral resolution. We include data taken during the recent X-ray eclipse in 1997-1998, after recovery from the eclipse, and during and after an X-ray flare. We show that the eclipse variation in the X-ray spectrum is apparently confined to a decrease in the emission measure of the source. We compare our results with a simple colliding wind binary model and find that the observed spectral variations are only consistent, with the binary model if there is significant high-temperature emission far from the star and/or a substantial change in the temperature distribution of the hot plasma. If contamination in the 2-10 keV band is important, the observed eclipse spectrum requires an absorbing column in excess of 10(exp 24)/sq cm for consistency with the binary model, which may indicate an increase in the first derivative of M from nu Carinae near the time of periastron passage. The flare spectra are consistent with the variability seen in nearly simultaneous RXTE observations and thus confirm that nu Carinae itself is the source of the flare emission. The variation in the spectrum during the flare seems confined to a change in the source emission measure. By comparing 2 observations obtained at the same phase in different X-ray cycles, we find that the current, X-ray brightness of the source is slightly higher than the brightness of the source during the last cycle perhaps indicative of a long-term increase in the first derivative of M, not associated with the X-ray cycle.

Corcoran, M. F.; Fredericks, A. C.; Petre, R.; Swank, J. H.; Drake, S. A.; White, Nicholas E. (Technical Monitor)

2000-01-01

65

X-ray-pulse characterization by spectral shearing interferometry using three-wave mixing  

NASA Astrophysics Data System (ADS)

We describe a method for measuring the field profile of x-ray ultrashort pulses including phase information. The scheme is based on spectrally interfering two replicas of the same pulse, which are spectrally shifted via three-wave mixing with IR or visible beams. Using a single-shot spectrometer the scheme can be used for the inspection of individual ultrashort x-ray pulses with random amplitudes and phases. Examples for characterization of stochastic pulses with a bandwidth of 1 eV are given, including criteria for a successful measurement.

Yudovich, S.; Shwartz, S.

2014-09-01

66

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Analysis of the applications of the Schwarzschild objective in the soft x-ray and VUV spectral ranges. 2. Diffraction modelling of aberrations  

NASA Astrophysics Data System (ADS)

An analysis is reported of the use of the Schwarzschild objective in soft x-ray and VUV (2-20 nm) microscopy. Estimates are given of the influence of the objective alignment and of the precision of fabrication of spherical mirrors on the resolution of the objective (point spread function, line spread function, and modulation transfer function).

Malyutin, A. A.

1997-02-01

67

Spectral distribution of Be/X-ray binaries in the Small Magellanic Cloud  

E-print Network

The spectral distributions of Be/X-ray binaries in the Large Magellanic Cloud and Galaxy have been shown to differ significantly from the distribution of isolated Be stars in the Galaxy. Population synthesis models can explain this difference in spectral distributions through substantial angular momentum loss from the binary system. In this work we explore the spectral distribution of Be/X-ray binaries in the Small Magellanic Cloud (SMC) using high signal-to-noise spectroscopy of a sample of 37 optical counterparts to known X-ray pulsars. Our results show that the spectral distribution of Be/X-ray binaries in the SMC is consistent with that of the Galaxy, despite the lower metallicity environment of the SMC. This may indicate that, although the metallicity of the SMC is conducive to the formation of a large number of HMXBs, the spectral distribution of these systems is likely to be most strongly influenced by angular momentum losses during binary evolution, which are not particularly dependent on the local metallicity.

V. A. McBride; M. J. Coe; I. Negueruela; M. P. E. Schurch; K. E. McGowan

2008-04-30

68

Temporal and spectral characteristics of solar flare hard X-ray emission  

NASA Technical Reports Server (NTRS)

Solar Maximum Mission observations of three flares that impose stringent constraints on physical models of the hard X-ray production during the impulsive phase are presented. Hard X-ray imaging observations of the flares on 1980 November 5 at 22:33 UT show two patches in the 16 to 30 keV images that are separated by 70,000 km and that brighten simultaneously to within 5 s. Observations to O V from one of the footprints show simultaneity of the brightening in this transition zone line and in the total hard X-ray flux to within a second or two. These results suggest but do not require the existence of electron beams in this flare. The rapid fluctuations of the hard X-ray flux within some flares on the time scales of 1 s also provide evidence for electron beams and limits on the time scale of the energy release mechanism. Observations of a flare on 1980 June 6 at 22:34 UT show variations in the 28 keV X-ray counting rate from one 20 ms interval to the next over a period of 10 s. The hard X-ray spectral variations measured with 128 ms time resolution for one 0.5 s spike during this flare are consistent with the predictions of thick-target non-thermal beam model.

Dennis, B. R.; Kiplinger, A. L.; Orwig, L. E.; Frost, K. J.

1985-01-01

69

Spectral encoding method for measuring the relative arrival time between x-ray/optical pulses.  

PubMed

The advent of few femtosecond x-ray light sources brings promise of x-ray/optical pump-probe experiments that can measure chemical and structural changes in the 10-100 fs time regime. Widely distributed timing systems used at x-ray Free-Electron Laser facilities are typically limited to above 50 fs fwhm jitter in active x-ray/optical synchronization. The approach of single-shot timing measurements is used to sort results in the event processing stage. This has seen wide use to accommodate the insufficient precision of active stabilization schemes. In this article, we review the current technique for "measure-and-sort" at the Linac Coherent Light Source at the SLAC National Accelerator Laboratory. The relative arrival time between an x-ray pulse and an optical pulse is measured near the experimental interaction region as a spectrally encoded cross-correlation signal. The cross-correlation provides a time-stamp for filter-and-sort algorithms used for real-time sorting. Sub-10 fs rms resolution is common in this technique, placing timing precision at the same scale as the duration of the shortest achievable x-ray pulses. PMID:25173255

Bionta, M R; Hartmann, N; Weaver, M; French, D; Nicholson, D J; Cryan, J P; Glownia, J M; Baker, K; Bostedt, C; Chollet, M; Ding, Y; Fritz, D M; Fry, A R; Kane, D J; Krzywinski, J; Lemke, H T; Messerschmidt, M; Schorb, S; Zhu, D; White, W E; Coffee, R N

2014-08-01

70

Dual-exposure technique for extending the dynamic range of x-ray flat panel detectors.  

PubMed

This work presents an approach to extend the dynamic range of x-ray flat panel detectors by combining two acquisitions of the same sample taken with two different x-ray photon flux levels and the same beam spectral configuration. In order to combine both datasets, the response of detector pixels was modelled in terms of mean and variance using a linear model. The model was extended to take into account the effect of pixel saturation. We estimated a joint probability density function (j-pdf) of the pixel values by assuming that each dataset follows an independent Gaussian distribution. This j-pdf was used for estimating the final pixel value of the high-dynamic-range dataset using a maximum likelihood method. The suitability of the pixel model for the representation of the detector signal was assessed using experimental data from a small-animal cone-beam micro-CT scanner equipped with a flat panel detector. The potential extension in dynamic range offered by our method was investigated for generic flat panel detectors using analytical expressions and simulations. The performance of the proposed dual-exposure approach in realistic imaging environments was compared with that of a regular single-exposure technique using experimental data from two different phantoms. Image quality was assessed in terms of signal-to-noise ratio, contrast, and analysis of profiles drawn on the images. The dynamic range, measured as the ratio between the exposure for saturation and the exposure equivalent to instrumentation noise, was increased from 76.9 to 166.7 when using our method. Dual-exposure results showed higher contrast-to-noise ratio and contrast resolution than the single-exposure acquisitions for the same x-ray dose. In addition, image artifacts were reduced in the combined dataset. This technique to extend the dynamic range of the detector without increasing the dose is particularly suited to image samples that contain both low and high attenuation regions. PMID:24352046

Sisniega, A; Abella, M; Desco, M; Vaquero, J J

2014-01-20

71

The X-ray spectral variability of the BL Lacertae type object PKS 2155-304  

NASA Technical Reports Server (NTRS)

We present a detailed study of the hard X-ray properties of the BL Lacertae object PKS 2155-304 based on measurements made in 1988 and 1989 with the Large Area Counter (LAC) on board the Ginga satellite. The source exhibited a high degree of variability with a dynamic range of a factor 7 in the 2-6 keV band. The fastest amplitude variation was a factor 2 decline in the intensity in this band within 4 hours. The spectrum is characterized by a break which occurs at about 4 keV. Spectral fits to the data integrated in 6400 s time bins reveal that, in common with previous observations of BL Lacertae objects, the spectral slope is generally anticorrelated with intensity in the sense that the spectrum hardens as the intensity increases. However, the tracks of sequential points in the index-intensity plane are occasionally seen to differ during the rise and decay stages of individual flares. Furthermore, during one, or possibly two, flaring episodes the spectral index is observed to correlate with intensity variations.

Sembay, S.; Warwick, R. S.; Urry, C. M.; Sokoloski, J.; George, I. M.; Makino, F.; Ohashi, T.; Tashiro, M.

1993-01-01

72

The solar spectral irradiances from x ray to radio wavelengths  

NASA Technical Reports Server (NTRS)

Sources of new measurements of the solar EUV, UV, and visible spectrum are presented together with discussion of formation of the solar spectrum as a problem in stellar atmospheres. Agreement between the data and a modern synthetic spectrum shows that observed radiative variability is a minor perturbation on a photosphere in radiative equilibrium and local thermodynamic equilibrium (LTE). Newly observed solar variability in 1992 defines a magnetic episode on the Sun closely associated with changes in both spectral irradiances and the total irradiance. This episode offers the opportunity to track the relationship between radiation and magnetic flux evolution.

White, O. R.

1993-01-01

73

X-RAY SPECTRAL VARIABILITY IN NGC 3783  

SciTech Connect

NGC 3783 was observed for approximately 210 ks by Suzaku and in this time showed significant spectral and flux variability at both short (20 ks) and long (100 ks) timescales. The full observation is found to consist of approximately six 'spectral periods' where the behavior of the soft (0.3-1.0 keV) and hard (2-10 keV) bands are somewhat distinct. Using a variety of methods we find that the strong warm absorber present in this source does not change on these timescales, confirming that the broadband variability is intrinsic to the central source. The time-resolved difference-spectra are well modeled with an absorbed power law below 10 keV, but show an additional hard excess at Almost-Equal-To 20 keV in the latter stages of the observation. This suggests that, in addition to the variable power law, there is a further variable component that varies with time but not monotonically with flux. We show that a likely interpretation is that this further component is associated with variations in the reflection fraction or possibly ionization state of the accretion disk a few gravitational radii from the black hole.

Reis, R. C.; Miller, J. M. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Fabian, A. C.; Walton, D. J. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Reynolds, C. S.; Trippe, M.; Mushotzky, R. F. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Brenneman, L. W. [Harvard-Smithsonian CfA, 60 Garden Street MS-67, Cambridge, MA 02138 (United States); Nowak, M. A. [MIT Kavli Institute for Astrophysics, Cambridge, MA 02139 (United States)

2012-01-20

74

Testing the Pairs-Reflection Model with X-Ray Spectral Variability and X-Ray Properties of Complete Samples of Radio-Selected BL Lacertae Objects  

NASA Technical Reports Server (NTRS)

This grant was awarded to Dr. C. Megan Urry of the Space Telescope Science Institute in response to two successful ADP proposals to use archival Ginga and Rosat X-ray data for 'Testing the Pairs-Reflection model with X-Ray Spectral Variability' (in collaboration with Paola Grandi, now at the University of Rome) and 'X-Ray Properties of Complete Samples of Radio-Selected BL Lacertae Objects' (in collaboration with then-graduate student Rita Sambruna, now a post-doc at Goddard Space Flight Center). In addition, post-docs Joseph Pesce and Elena Pian, and graduate student Matthew O'Dowd, have worked on several aspects of these projects. The grant was originally awarded on 3/01/94; this report covers the full period, through May 1997. We have completed our project on the X-ray properties of radio-selected BL Lacs.

Urry, C. Megan

1997-01-01

75

TEMPORAL AND SPATIAL ANALYSES OF SPECTRAL INDICES OF NONTHERMAL EMISSIONS DERIVED FROM HARD X-RAYS AND MICROWAVES  

SciTech Connect

We studied electron spectral indices of nonthermal emissions seen in hard X-rays (HXRs) and microwaves. We analyzed 12 flares observed by the Hard X-Ray Telescope aboard Yohkoh, Nobeyama Radio Polarimeters, and the Nobeyama Radioheliograph (NoRH), and compared the spectral indices derived from total fluxes of HXRs and microwaves. Except for four events, which have very soft HXR spectra suffering from the thermal component, these flares show a gap {Delta}{delta} between the electron spectral indices derived from HXRs {delta} {sub X} and those from microwaves {delta}{sub {mu}} ({Delta}{delta} = {delta} {sub X} - {delta}{sub {mu}}) of about 1.6. Furthermore, from the start to the peak times of the HXR bursts, the time profiles of the HXR spectral index {delta} {sub X} evolve synchronously with those of the microwave spectral index {delta}{sub {mu}}, keeping the constant gap. We also examined the spatially resolved distribution of the microwave spectral index by using NoRH data. The microwave spectral index {delta}{sub {mu}} tends to be larger, which means a softer spectrum, at HXR footpoint sources with stronger magnetic field than that at the loop tops. These results suggest that the electron spectra are bent at around several hundreds of keV, and become harder at the higher energy range that contributes the microwave gyrosynchrotron emission.

Asai, Ayumi [Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto, 607-8471 (Japan)] [Unit of Synergetic Studies for Space, Kyoto University, Yamashina, Kyoto, 607-8471 (Japan); Kiyohara, Junko; Takasaki, Hiroyuki [Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto, 607-8471 (Japan)] [Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto, 607-8471 (Japan); Narukage, Noriyuki [Institute of Space and Astronomical Science, Japan Aerospace Exploration Agency, Chuo, Sagamihara, Kanagawa, 229-8510 (Japan)] [Institute of Space and Astronomical Science, Japan Aerospace Exploration Agency, Chuo, Sagamihara, Kanagawa, 229-8510 (Japan); Yokoyama, Takaaki [Department of Earth and Planetary Science, University of Tokyo, Hongo, Bunkyo, Tokyo, 113-0033 (Japan)] [Department of Earth and Planetary Science, University of Tokyo, Hongo, Bunkyo, Tokyo, 113-0033 (Japan); Masuda, Satoshi [Solar-Terrestrial Environment Laboratory, Nagoya University, Chikusa, Nagoya, Aichi, 464-8601 (Japan)] [Solar-Terrestrial Environment Laboratory, Nagoya University, Chikusa, Nagoya, Aichi, 464-8601 (Japan); Shimojo, Masumi [National Astronomical Observatory of Japan, Mitaka, Tokyo, 181-8588 (Japan)] [National Astronomical Observatory of Japan, Mitaka, Tokyo, 181-8588 (Japan); Nakajima, Hiroshi, E-mail: asai@kwasan.kyoto-u.ac.jp [Nobeyama Solar Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Minamisaku, Nagano, 384-1305 (Japan)] [Nobeyama Solar Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Minamisaku, Nagano, 384-1305 (Japan)

2013-02-15

76

Spatial and spectral features of soft diffuse X ray background seen by the Einstein observatory  

NASA Technical Reports Server (NTRS)

A survey of the diffuse soft X-ray background as seen directly by the Einstein Observatory Imaging Proportional Counter (IPC) is presented. A source free region of the detector 1 by 1 degree field is used. The background in the 0.16 to 3.5 keV spectral region is viewed. The data covers roughly 5 percent of the sky, with some bias in coverage towards the galactic plane. The moderate energy resolution of the IPC enables the characterization and the production of maps of the background as a function of energy within the Einstein passband. The results are compared with previous observations of the diffuse X-ray background. The implications for galactic structure and for the soft component of the extragalactic X-ray background are discussed.

Micela, G.; Harnden, F. R.; Rosner, R., Jr.; Sciortino, S.; Vaiana, G. S.

1989-01-01

77

New constraints on the X-ray spectral properties of type 1 active galactic nuclei  

NASA Astrophysics Data System (ADS)

We present a detailed characterization of the X-ray spectral properties of 761 type 1 active galactic nuclei (AGN), selected from a cross-correlation of the SDSS DR5 quasar catalogue and the incremental version of the second XMM-Newton serendipitous X-ray source catalogue 2XMMi-DR2. The X-ray spectrum of each source has been fitted with models based on a simple power law to which additional cold absorption and/or soft-excess features have been added if an F-test at 99 per cent significance required them. The distribution of best-fitting photon indices, ?, has been fitted with a Gaussian with mean = 1.99 ± 0.01 and dispersion ?= 0.30 ± 0.01; however, this does not provide a good representation of the distribution due to sources with very flat or steep ? values. A highly significant trend for decreasing ? values with increasing 2-10 keV luminosity, LX, has been seen but only a weak trend with redshift has been found. Intrinsic cold absorption has been detected in ˜4 per cent of the sample and soft-excess emission has been detected in ˜8 per cent. These values are lower limits due to the detectability being limited by the quality of the spectra and we suggest that the intrinsic values may be as high as ˜25 and ˜80 per cent, respectively. The levels of rest-frame absorption are higher than expected for type 1 objects (NH= 1021-1023 cm-2) and the fraction of absorbed sources and the NH values were not seen to vary with LX or z. The average blackbody temperature used to model the soft excesses is = 0.17 ± 0.09 keV. This temperature has been found to correlate with LX but not the blackbody luminosity or the black hole mass which do correlate with each other. A strong correlation has been found between the luminosities in the blackbody and power-law components, suggesting that a similar fraction is reprocessed from the blackbody to the power-law component for the entire luminosity range of objects. A positive correlation between ? and the X-ray derived Eddington ratio has been found for the sources whose mass was determined using the H? line, but a negative correlation has been found where the C IV line was used. No correlation has been found where the Mg II line was used. No significant correlations have been found between the blackbody temperature, luminosity or black hole mass with Eddington ratio, despite a link between the power law and blackbody production being indicated. The sample includes 552 confirmed radio-quiet quasars (RQQ) and 75 confirmed radio-loud quasars (RLQ). The RLQ have been found to have higher LX values than their RQQ counterparts, suggesting an additional X-ray component, perhaps related to a jet, is present in these sources. This component may also be the cause of the flatter ? values seen in RLQ.

Scott, A. E.; Stewart, G. C.; Mateos, S.; Alexander, D. M.; Hutton, S.; Ward, M. J.

2011-10-01

78

Influence of X-ray tube spectral distribution on uncertainty of calculated fluorescent radiation intensity  

NASA Astrophysics Data System (ADS)

The relative radiation intensity ( Ri) defined as fluorescent radiation intensity of analyte in specimen to fluorescent radiation intensity of pure element or compound, e.g., oxide is used in calculation in both fundamental parameter methods and in theoretical influence coefficient algorithms. Accuracy of calculated Ri is determined by uncertainties of atomic parameters, spectrometer geometry and also by X-ray tube spectral distribution. This paper presents the differences between Ri calculated using experimental and theoretical X-ray tube spectra evaluated by three different algorithms proposed by Pella et al., Ebel, and Finkelshtein-Pavlova. The calculations are performed for the most common targets, i.e., Cr, Mo, Rh and W. In this study, Ri is calculated for V, Cr, Mn, Fe, Co, Ni, Cu and Mo in steels as an example. The differences between Ri calculated using different X-ray tube spectrum algorithms are presented when pure element standard, multielement standard similar to the analyzed material and one pure element standard for all analytes is used in X-ray fluorescence analysis. The differences between Ri for intermediate-thickness samples (and also for thin films) and for X-ray tube, which ran for many hours, are also evaluated.

Sitko, Rafa?

2007-08-01

79

X-Ray Spectral Analysis of SU UMa Type Dwarf Novae Observed with Rosat  

NASA Astrophysics Data System (ADS)

X-ay spectral parameters were determined for eight SU UMa type Dwarf Novae observed with the ROSAT PSPC. The raw data were fitted with various spectral models and the best fit spectral models are found to be that of Raymond-Smith and Thermal Bremsstrahlung. The best fit temperatures were estimated to be between kT ~ 1.1 - 1.8 keV while the Column Densities were found to be between NH ~ 2.4 × 1020 - 4.1 × 1020 cm-2. The estimated 0.1 - 2.4 keV fluxes were in the range of log FX = -13 to -11 ergs cm-2 s-1. FX/FUV and FX/Fopt rates were calculated to be between ~ 0.09 and ~ 0.37. This shows that most of the energy is radiated in the Optical and Ultraviolet band from the accretion disk in the quiescent state. Many of the SU UMa type Dwarf Novae show an Ultraviolet lag in their outburst spectrum, the Coronal Siphon Flow Model of Meyer and Meyer-Hofmeister may explain this phenomenon. This model proposes a corona at the boundary layer of a system when it is a quiescent state and suggests that some parts of the X-rays come from the corona. For these reasons, the equations of this model were applied to the results of the spectral analysis. Using this model, the mass accretion rates, the mass evaporation rates, and the radii of the coronas were calculated to be ~ 10-12.3 - 10-11.3 Msolar yr-1, ~ 10-6.5 - 10-5.5 g cm-2 s-1 and ~ 109.1 - 109.9 cm, respectively. The pressures in the coronas were less than ~ 1200 g cm-2 s-1 for (z) up to ~ 10 × 109 cm. The obtained values suggest that the Corona model can indeed operate in SU UMa type Dwarf Novae.

Gün, Gülnur Ýkis; Ercan, E. Nihal

80

X-ray temporal and spectral studies of blazars with the Ginga satellite  

NASA Technical Reports Server (NTRS)

This is the final report to the National Aeronautics and Space Administration (NASA) concerning NASA grant NAG8-697. This grant was awarded to Dr. C. Megan Urry of the Space Telescope Science Institute in response to a proposal, entitled 'X-Ray Temporal and Spectral Studies of Blazars with the Ginga Satellite', to collaborate with Japanese colleagues in using the Ginga X-ray satellite. The grant was originally awarded on 2/27/88 and expired on 3/31/94. The Ginga X-ray satellite had unprecedented sensitivity in the 2-20 keV energy band, allowing us to make detailed temporal and spectral studies of a large number of blazars, which are a kind of unusually luminous and variable active galactic nuclei. We were successful with several proposals and were able to observe a number of different active galactic nuclei. Our investigations under this grant fall broadly into two categories: (1) Ginga observations of blazars, usually in conjunction with simultaneous multiwavelength observations using other facilities; and (2) the application of calculated pair plasma spectra to the X-ray colors of active galactic nuclei. These are described in turn.

Urry, C. Megan

1994-01-01

81

Regularized energy-dependent solar flare hard x-ray spectral index  

E-print Network

The deduction from solar flare X-ray photon spectroscopic data of the energy dependent model-independent spectral index is considered as an inverse problem. Using the well developed regularization approach we analyze the energy dependency of spectral index for a high resolution energy spectrum provided by Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The regularization technique produces much smoother derivatives while avoiding additional errors typical of finite differences. It is shown that observations imply a spectral index varying significantly with energy, in a way that also varies with time as the flare progresses. The implications of these findings are discussed in the solar flare context.

Eduard P. Kontar; Alexander L. MacKinnon

2005-06-05

82

Resolution of Auger and X-ray photoelectron spectra of mixtures by spectral ratioing  

NASA Astrophysics Data System (ADS)

A method is described for resolving multicomponent Auger or X-ray photoelectron spectra into spectra of the pure components. The method begins by computing spectral ratios from two multicomponent spectra which contain the same unidentified components, but in different proportions. One requirement of the method is that a spectral region must exist for each component where only that component contributes to the signal. A second requirement is that the inelastic energy loss background must be suppressed. An appropriate background suppression method is presented for ESCA (Electron Spectroscopy for Chemical Analysis) survey spectra. Spectral ratioing is applied to Auger and ESCA spectra to identify surface segregates on heat-treated alloy steels.

Gaarenstroom, Stephen W.; Waldo, Richard A.

1984-05-01

83

X-ray spectral variability of LINERs selected from the Palomar sample  

NASA Astrophysics Data System (ADS)

Variability in active galactic nuclei (AGN) has been discovered at X-ray, UV, and radio frequencies on timescales from hours to years, being one of their most important features. Among the AGN family and according to theoretical studies, low-ionization nuclear emission line region (LINER) nuclei would be variable objects at long timescales because of their large black hole masses and low accretion rates. Our aim is to investigate the spectral X-ray variability in LINERs, leading to an understanding of the nature of this kind of objects, including their accretion mechanism. We selected 18 LINERs from the Palomar sample, and used Chandra and XMM-Newton public archives to analyze their X-ray spectral properties at different epochs with timescales of years. Spectral modeling allowed us to investigate the parameter(s) responsible for the variations. The main result from the analysis is that long term spectral variability is very common, mostly related to the nuclear power at hard (2-10 keV) energies.

Hernandez-Garcia, L.; González-Martín, O.; Masegosa, J.; Márquez, I.

2014-07-01

84

PIXIE III: a very large area photon-counting CMOS pixel ASIC for sharp X-ray spectral imaging  

NASA Astrophysics Data System (ADS)

PIXIE III is the third generation of very large area (32 × 25 mm2) pixel ASICs developed by Pixirad Imaging Counters s.r.l. to be used in combination with suitable X-ray sensor materials (Silicon, CdTe, GaAs) in hybrid assemblies using flip-chip bonding. A Pixirad unit module based on PIXIE III shows several advances compared to what has been available up to now. It has a very broad energy range (from 2 to 100 keV before full pulse saturation), high speed (100 ns peaking time), high frame rate (larger than 500 fps), dead-time-free operation, good energy resolution (around 2 keV at 20 keV), high photo-peak fraction and sharp spectral separation between the color images. In this paper the results obtained with PIXIE III both in a test bench set-up as well in X-ray imaging applications are discussed.

Bellazzini, R.; Brez, A.; Spandre, G.; Minuti, M.; Pinchera, M.; Delogu, P.; de Ruvo, P. L.; Vincenzi, A.

2015-01-01

85

Experimental spectral measurements of heavy K-edge filtered beams for x-ray computed mammotomography  

PubMed Central

A dual modality computed mammotomography (CmT) and single photon emission computed tomography (SPECT) system for dedicated 3D breast imaging is in development. Using heavy K-edge filtration, the CmT component narrows the energy spectrum of the cone-shaped x-ray beam incident on the patient’s pendant, uncompressed breast. This quasi-monochromatic beam is expected to improve discrimination of tissue with similar attenuation coefficients while restraining absorbed dose to below that of dual view mammography. Previous simulation studies showed the optimal energy that maximizes dose efficiency for a 50/50% adipose/glandular breast is between 30 and 40 keV. This study experimentally validates these results using pre-breast and post-breast spectral measurements made under tungsten tube voltages between 40 and 100 kVp using filter materials with K-edge values ranging from 15 to 70 keV. Different filter material thicknesses are used, approximately equivalent to the 200th and 500th attenuating value layer (VL) thickness. Cerium (K = 40.4 keV) filtered post-breast spectra for 8–18 cm breasts are measured for a range of breast compositions. Figures of merit include mean beam energy, spectral full-width at tenth-maximum, beam hardening and dose for the range of breast sizes. Measurements corroborate simulation results, indicating that for a given dose, a 200th VL of cerium filtration may have optimal performance in the dedicated mammotomography paradigm. PMID:17228108

Crotty, D J; McKinley, R L; Tornai, M P

2012-01-01

86

X-ray spectral constraints on the broad-line cloud geometry of NGC 4151  

NASA Technical Reports Server (NTRS)

X-ray spectral data from NGC 4151 taken with the Einstein Solid-State Spectrometer (SSS) and the HEAO-1 A-2 experiment cannot be simply reconciled with absorption from a uniform column of cold gas. The SSS data can, however, be explained in terms of a clumped absorber with approximately 10% uncovered fraction and factor-of-two overabundances in Z equal to or greater than 14 elements relative to solar oxygen. It is shown that these and previously reported spectral and variability data can be quantitatively reconciled with absorption arising in the cold clouds responsible for the broad optical line emission if the cloud dimensions are small compared to the central source size. It is suggested that the lack of significant X-ray absorption observed from much higher luminosity Seyferts and quasars is a natural consequence of our picture for NGC 4151.

Holt, S. S.; Muchotzky, R. F.; Becker, R. H.; Boldt, E. A.; Serlemitsos, P. J.; Szymkowiak, A. E.; White, N. E.

1980-01-01

87

X-ray spectral constraints on the broad-line cloud geometry of NGC 4151  

NASA Technical Reports Server (NTRS)

X-ray spectral data from NGC 4151 taken with the Einstein Solid-State Spectrometer (SSS) and the HEAO 1 A-2 experiment cannot be simply reconciled with absorption from a uniform column of cold gas. The SSS data can, however, be explained in terms of a clumped absorber with approximately 10% uncovered fraction and factor-of-two overabundances in Z equal to or greater than 14 elements relative to solar oxygen. It is shown that these and previously reported spectral and variability data can be quantitatively reconciled with absorption arising in the cold clouds responsible for the broad optical line emission if the cloud dimensions are small compared to the central source size. It is suggested that the lack of significant X-ray absorption observed from much higher luminosity Seyferts and quasars is a natural consequence of the proposed picture for NGC 4151.

Holt, S. S.; Mushotzky, R. F.; Boldt, E. A.; Serlemitsos, P. J.; Becker, R. H.; Szymkowiak, A. E.; White, N. E.

1980-01-01

88

Automated analysis of SEM X-ray spectral images: a powerful new microanalysis tool.  

PubMed

Spectral imaging in the scanning electron microscope (SEM) equipped with an energy-dispersive X-ray (EDX) analyzer has the potential to be a powerful tool for chemical phase identification, but the large data sets have, in the past, proved too large to efficiently analyze. In the present work, we describe the application of a new automated, unbiased, multivariate statistical analysis technique to very large X-ray spectral image data sets. The method, based in part on principal components analysis, returns physically accurate (all positive) component spectra and images in a few minutes on a standard personal computer. The efficacy of the technique for microanalysis is illustrated by the analysis of complex multi-phase materials, particulates, a diffusion couple, and a single-pixel-detection problem. PMID:12597783

Kotula, Paul G; Keenan, Michael R; Michael, Joseph R

2003-02-01

89

Are spectral and timing correlations similar in different spectral states in black hole X-ray binaries?  

E-print Network

We study the outbursts of the black hole X-ray binaries MAXI J1659-152, SWIFT J1753.5--0127 and GX 339-4 with the Swift X-ray Telescope. The bandpass of the X-ray Telescope has access to emission from both components of the accretion flow: the accretion disk and the corona/hot flow. This allows a correlated spectral and variability study, with variability from both components of the accretion flow. We present for the first time, a combined study of the evolution of spectral parameters (disk temperature and radius) and timing parameters (frequency and strength) of all power spectral components in different spectral states. Comparison of the correlations in different spectral states shows that the frequency and strength of the power spectral components exhibit dependencies on the disk temperature that are different in the (low-)hard and the hard-intermediate states; most of these correlations that are clearly observed in the hard-intermediate state (in MAXI J1659-152 and GX 339-4) are not seen in the (low-)hard...

Kalamkar, M; van der Klis, M; Altamirano, D; Miller, J M

2015-01-01

90

Optical and X-ray radiation from fast pulsars - Effects of duty cycle and spectral shape  

NASA Technical Reports Server (NTRS)

The optical luminosity of PSR 0540 is considerably stronger than what one would have predicted in a simple model developed earlier where the pulses are synchrotron radiation by secondary electrons near the light cylinder. This discrepancy can be eliminated if one incorporates into the model the effects of the large duty cycle and the spectral properties of PSR 0540. It is also shown that the same model can provide a reasonable fit to the observed X-ray fluxes from fast pulsars.

Pacini, F.; Salvati, M.

1987-01-01

91

High-spatial resolution and high-spectral resolution detector for use in the measurement of solar flare hard X-rays  

NASA Technical Reports Server (NTRS)

In the areas of high spatial resolution, the evaluation of a hard X-ray detector with 65 micron spatial resolution for operation in the energy range from 30 to 400 keV is proposed. The basic detector is a thick large-area scintillator faceplate, composed of a matrix of high-density scintillating glass fibers, attached to a proximity type image intensifier tube with a resistive-anode digital readout system. Such a detector, combined with a coded-aperture mask, would be ideal for use as a modest-sized hard X-ray imaging instrument up to X-ray energies as high as several hundred keV. As an integral part of this study it was also proposed that several techniques be critically evaluated for X-ray image coding which could be used with this detector. In the area of high spectral resolution, it is proposed to evaluate two different types of detectors for use as X-ray spectrometers for solar flares: planar silicon detectors and high-purity germanium detectors (HPGe). Instruments utilizing these high-spatial-resolution detectors for hard X-ray imaging measurements from 30 to 400 keV and high-spectral-resolution detectors for measurements over a similar energy range would be ideally suited for making crucial solar flare observations during the upcoming maximum in the solar cycle.

Desai, U. D.; Orwig, Larry E.

1988-01-01

92

Unsupervised spectral decomposition of X-ray binaries with application to GX 339-4  

NASA Astrophysics Data System (ADS)

In this paper, we explore unsupervised spectral decomposition methods for distinguishing the effect of different spectral components for a set of consecutive spectra from an X-ray binary. We use well-established linear methods for the decomposition, namely principal component analysis, independent component analysis and non-negative matrix factorization (NMF). Applying these methods to a simulated data set consisting of a variable multicolour disc blackbody and a cutoff power law, we find that NMF outperforms the other two methods in distinguishing the spectral components. In addition, due the non-negative nature of NMF, the resulting components may be fitted separately, revealing the evolution of individual parameters. To test the NMF method on a real source, we analyse data from the low-mass X-ray binary GX 339-4 and found the results to match those of previous studies. In addition, we found the inner radius of the accretion disc to be located at the innermost stable circular orbit in the intermediate state right after the outburst peak. This study shows that using unsupervised spectral decomposition methods results in detecting the separate component fluxes down to low flux levels. Also, these methods provide an alternative way of detecting the spectral components without performing actual spectral fitting, which may prove to be practical when dealing with large data sets.

Koljonen, K. I. I.

2015-03-01

93

X-Ray Fluctuation Power Spectral Densities of Seyfert 1 Galaxies  

NASA Technical Reports Server (NTRS)

By combining complementary monitoring observations spanning long, medium and short time scales, we have constructed power spectral densities (PSDs) of six Seyfert 1 galaxies. These PSDs span approx. greater than 4 orders of magnitude in temporal frequency, sampling variations on time scales ranging from tens of minutes to over a year. In at least four cases, the PSD shows a "break," a significant departure from a power law, typically on time scales of order a few days. This is similar to the behavior of Galactic X-ray binaries (XRBs), lower mass compact systems with breaks on time scales of seconds. NGC 3783 shows tentative evidence for a doubly-broken power law, a feature that until now has only been seen in the (much better-defined) PSDs of low-state XRBs. It is also interesting that (when one previously-observed object is added to make a small sample of seven), an apparently significant correlation is seen between the break time scale T and the putative black hole mass M(sub BH), while none is seen between break time scale and luminosity. The data are consistent with the linear relation T = M(sub BH) /10(exp 6.5) solar mass; extrapolation over 6-7 orders of magnitude is in reasonable agreement with XRBs. All of this strengthens the case for a physical similarity between Seyfert 1s and XRBs.

Markowitz, A.; Edelson, R.; Vaughan, S.; Uttley, P.; George, I. M.; Griffiths, R. E.; Kaspi, S.; Lawrence, A.; McHandy, I.; Nandra, K.

2003-01-01

94

Spontaneous and X-Ray Triggered Crystallization at Long Range in Self-Assembling Filament Networks  

PubMed Central

We report here crystallization at long range in networks of like-charge supramolecular filaments mediated by repulsive forces. The crystallization is spontaneous beyond a given concentration of the molecules that form the filaments, but can be triggered by X-ray photons at lower concentrations. The crystalline domains formed by X-ray irradiation, with inter-filament separations of up to 320 angstroms, are stable for hours after the beam is turned off, and ions that screen charges on the filaments suppress ordering. We hypothesize that the stability of crystalline domains emerges from a balance of repulsive tensions linked to native or X-ray induced charges and the mechanical compressive entrapment of filaments within a network. Similar phenomena may occur naturally in the cytoskeleton of cells, and if induced externally in biological or artificial systems lead to possible biomedical and lithographic functions. PMID:20019248

Cui, Honggang; Pashuck, Eugene T.; Velichko, Yuri S.; Weigand, Steven J.; Cheetham, Andrew G.; Newcomb, Christina J.; Stupp, Samuel I.

2011-01-01

95

A statistical relation between the X-ray spectral index and Eddington ratio of active galactic nuclei in deep surveys  

NASA Astrophysics Data System (ADS)

We present an investigation into how well the properties of the accretion flow on to a supermassive black hole may be coupled to those of the overlying hot corona. To do so, we specifically measure the characteristic spectral index, ?, of a power-law energy distribution, over an energy range of 2-10 keV, for X-ray selected, broad-lined radio-quiet active galactic nuclei (AGN) up to z ˜ 2 in Cosmic Evolution Survey (COSMOS) and Extended Chandra Deep Field South (E-CDF-S). We test the previously reported dependence between ? and black hole mass, full width at half-maximum (FWHM) and Eddington ratio using a sample of AGN covering a broad range in these parameters based on both the Mg II and H? emission lines with the later afforded by recent near-infrared spectroscopic observations using Subaru/Fibre Multi Object Spectrograph. We calculate the Eddington ratios, ?Edd, for sources where a bolometric luminosity (LBol) has been presented in the literature, based on spectral energy distribution fitting, or, for sources where these data do not exist, we calculate LBol using a bolometric correction to the X-ray luminosity, derived from a relationship between the bolometric correction and LX/L3000. From a sample of 69 X-ray bright sources (>250 counts), where ? can be measured with greatest precision, with an estimate of LBol, we find a statistically significant correlation between ? and ?Edd, which is highly significant with a chance probability of 6.59× 10-8. A statistically significant correlation between ? and the FWHM of the optical lines is confirmed, but at lower significance than with ?Edd indicating that ?Edd is the key parameter driving conditions in the corona. Linear regression analysis reveals that ? = (0.32 ± 0.05) log10?Edd + (2.27 ± 0.06) and ? = (-0.69 ± 0.11) log10(FWHM/km s-1) + (4.44 ± 0.42). Our results on ?-?Edd are in very good agreement with previous results. While the ?-?Edd relationship means that X-ray spectroscopy may be used to estimate black hole accretion rate, considerable dispersion in the correlation does not make this viable for single sources, however could be valuable for large X-ray spectral samples, such as those to be produced by eROSITA.

Brightman, M.; Silverman, J. D.; Mainieri, V.; Ueda, Y.; Schramm, M.; Matsuoka, K.; Nagao, T.; Steinhardt, C.; Kartaltepe, J.; Sanders, D. B.; Treister, E.; Shemmer, O.; Brandt, W. N.; Brusa, M.; Comastri, A.; Ho, L. C.; Lanzuisi, G.; Lusso, E.; Nandra, K.; Salvato, M.; Zamorani, G.; Akiyama, M.; Alexander, D. M.; Bongiorno, A.; Capak, P.; Civano, F.; Del Moro, A.; Doi, A.; Elvis, M.; Hasinger, G.; Laird, E. S.; Masters, D.; Mignoli, M.; Ohta, K.; Schawinski, K.; Taniguchi, Y.

2013-08-01

96

X-RAY PROPERTIES OF INTERMEDIATE-MASS BLACK HOLES IN ACTIVE GALAXIES. III. SPECTRAL ENERGY DISTRIBUTION AND POSSIBLE EVIDENCE FOR INTRINSICALLY X-RAY-WEAK ACTIVE GALACTIC NUCLEI  

SciTech Connect

We present a systematic X-ray study, the third in a series, of 49 active galactic nuclei with intermediate-mass black holes (IMBH; {approx}10{sup 5}-10{sup 6} M{sub Sun }) using Chandra observations. We detect 42 out of 49 targets with a 0.5-2 keV X-ray luminosity 10{sup 41}-10{sup 43} erg s{sup -1}. We perform spectral fitting for the 10 objects with enough counts (>200), and they are all well fit by a simple power-law model modified by Galactic absorption, with no sign of significant intrinsic absorption. While we cannot fit the X-ray spectral slope directly for the rest of the sample, we estimate it from the hardness ratio and find a range of photon indices consistent with those seen in more luminous and massive objects. The X-ray-to-optical spectral slope ({alpha}{sub ox}) of our IMBH sample is systematically flatter than in active galaxies with more massive black holes, consistent with the well-known correlation between {alpha}{sub ox} and UV luminosity. Thanks to the wide dynamic range of our sample, we find evidence that {alpha}{sub ox} increases with decreasing M{sub BH} as expected from accretion disk models, where the UV emission systematically decreases as M{sub BH} decreases and the disk temperature increases. We also find a long tail toward low {alpha}{sub ox} values. While some of these sources may be obscured, given the high L{sub bol}/L{sub Edd} values in the sample, we argue that some may be intrinsically X-ray-weak, perhaps owing to a rare state that radiates very little coronal emission.

Dong Ruobing; Greene, Jenny E. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Ho, Luis C., E-mail: rdong@princeton.edu, E-mail: jgreene@princeton.edu, E-mail: lho@obs.carnegiescience.edu [Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States)

2012-12-10

97

Revealing a hard X-ray spectral component reverberating within one light hour of the central Supermassive Black Hole in Ark 564  

E-print Network

Ark 564 (z=0.0247) is an X-ray bright NLS1. By using advanced X-ray timing techniques, Legg et al. (2012) discovered an excess of "delayed" emission in the hard X-ray band (4-7.5 keV) following about 1000 seconds after "flaring" light in the soft X-ray band (0.4-1 keV). We report on the X-ray spectral analysis of eight XMM-Newton and one Suzaku observation of Ark 564. High-resolution spectroscopy was performed with the RGS in the soft X-ray band, while broad-band spectroscopy was performed with the EPIC-pn and XIS/PIN instruments. We analysed time-averaged, flux-selected, and time-resolved spectra. Despite the large variability in flux, the broad band spectral shape of Ark 564 is not dramatically varying and can be reproduced either by a superposition of a power law and a blackbody emission, or by a Comptonized power law emission model. High resolution spectroscopy revealed the presence of ionised gas along the line of sight at the systemic redshift of the source, with a low column density and a range of ioni...

Giustini, M; Reeves, J N; Miller, L; Legg, E; Kraemer, S B; George, I M

2015-01-01

98

Black hole X-ray binaries LMC X-1 and X-3: observations confront spectral models  

NASA Astrophysics Data System (ADS)

We present a comprehensive spectral analysis of black hole X-ray binaries, LMC X-1 and X-3, based on BeppoSAX observations. We test both the multicolour disc plus power-law (MCD+PL) model and a newly developed Monte Carlo simulation-based model for a Comptonized MCD (CMCD) with either a spherical or a slab-like corona, by comparing the inferred parameters with independent direct measurements. While all models give an adequate description of the spectra, we find a significant discrepancy between the MCD+PL inferred X-ray-absorbing gas column density and the absorption-edge measurement based on dispersed X-ray spectra. The MCD+PL fits to the LMC X-1 spectra also require a change in the inner disc radius during the BeppoSAX observation, which may be due to the unphysical effects inherited in the model. In contrast, the CMCD model with the spherical corona gives predictions of both the disc inclination angle and the absorption that are consistent with the direct measurements, and only slightly underpredicts the black hole mass of LMC X-3. The model explains the spectral state evolution of LMC X-1 within the BeppoSAX observation as a change in the accretion rate, which leads to an increase in both the inner disc temperature and the Comptonization opacity. On the other hand, the CMCD model with the slab-like corona is more problematic in the test and is thus not recommended.

Yao, Yangsen; Wang, Q. Daniel; Nan Zhang, Shuang

2005-09-01

99

Astro-H: New Spectral Features Seen in High-Resolution X-rays  

NASA Astrophysics Data System (ADS)

The Soft X-ray Spectrometer (SXS) microcalorimeter on Astro-H will provide the first high-resolution X-ray spectra of diffuse astrophysical sources. One key new type of science will be charge exchange spectroscopy, wherein highly-ionized metals interact with neutral hydrogen, helium, or other material. This has been detected with modest resolution in comets and planets, and is thought to be the origin of at least some of the 1/4 keV soft X-ray background. We will report on the predicted emission that the Astro-H SXS may detector from all of these sources using the recently released AtomdB Charge Exchange spectral model acx, and comment on possible other sources such as starburst galaxies. The SXS will also observe complex high-resolution spectra from other diffuse sources such as overionized supernova remnants and galaxy clusters. We will discuss these in the context of advanced spectral models using the recently released AtomDB v3.0 data and non-equilibrium models.

Astro-H Science Working Group

2015-01-01

100

X-ray spectral variability of seven LINER nuclei with XMM-Newton and Chandra data  

NASA Astrophysics Data System (ADS)

Context. One of the most distinctive features in active galactic nuclei (AGN) is the variability of their emission. Variability has been discovered at X-ray, UV, and radio frequencies on timescales from hours to years. Among the AGN family and according to theoretical studies, low-ionization nuclear emission line region (LINER) nuclei would be objects variable on long timescales. Aims: Our purpose is to investigate spectral X-ray variability in LINERs and to understand the nature of these types of objects, as well as their accretion mechanism. Methods: Chandra and XMM-Newton public archives were used to compile X-ray spectra of seven LINER nuclei at different epochs with timescales of years. To search for variability we fit all spectra from the same object with a set of models to identify the parameters responsible for the variability pattern. We also analyzed the light curves to search for short timescale (from hours to days) variability. Whenever possible, UV variability was also studied. Results: We found spectral variability in four objects (NGC 1052, NGC 3226, NGC 4278, and NGC 4552), with variations mostly related to hard energies (2-10 keV). These variations are generated by several possible changes that act either alone or in combination: changes in the soft excess or in the absorber. Added to this can be intrinsic variations of the source, which may also be responsible by themselves for the spectral variability. These variations occurred within years, the shortest timescale being found for NGC 4278 (two months). Another two galaxies (NGC 4261 and NGC 5846) apparently do not vary. No short timescale variations during individual observations were found. Our analysis confirms the previously reported anticorrelation between the X-ray spectral index, ?, and the Eddington ratio, Lbol/LEdd, and also the correlation between the X-ray to UV flux ratio, ?ox, and the Eddington ratio, Lbol/LEdd. These results support an advection dominated accretion flow as the accretion mechanism in LINERs. Tables 2-11 and Appendices are available in electronic form at http://www.aanda.org

Hernández-García, L.; González-Martín, O.; Márquez, I.; Masegosa, J.

2013-08-01

101

XOP: A graphical user interface for spectral calculations and x-ray optics utilities  

NASA Astrophysics Data System (ADS)

A graphical user interface, using the Interactive Data Language (IDL) widget toolkit, for calculation of spectral properties of synchrotron radiation sources and for interaction of x-rays with optical elements has been developed. The interface runs presently on three different computer architectures under the Unix operating system - the Sun-OS, the HP-UX, and the DEC-Unix operating systems. The point-and-click interface is used as a driver program for a variety of codes from different authors written in different computer languages. The execution of codes for calculating synchrotron radiation from undulators, wigglers, and bending magnets is summarized. The computation of optical properties of materials and the x-ray diffraction profiles from crystals in different geometries are also discussed. The interface largely simplifies the use of these codes and may be used without prior knowledge of how to run a particular program.

Dejus, Roger J.; Sanchez del Rio, Manuel

1996-09-01

102

The Extragalactic X-ray Background in the 0.2 - 2 keV Range  

NASA Technical Reports Server (NTRS)

We made the first measurement of the extragalactic 0.7 keV background. We detected the X-ray shadow of a neutral gas cloud in the Magellanic Bridge. We further constrained the point-like source contribution based on the mean spectrum of detected sources and on our early autocorrelation function analysis of the background. We find that our measurement extragalactic background intensity is significantly greater than the total point-like source contribution expected if sources are responsible for all the observed background intensity in the 1-2 keV range. For a further confirmation of the theoretical prediction of the hot intergalactic medium, we have conducted a pilot project to search for enhanced X-ray-emitting features near rich clusters of galaxies. We have reported the discovery of an elongated complex of extended X-ray-emitting objects in and around the galaxy cluster A2125, based on an archival deep ROSAT/PSPC observation. Using multicolor optical imaging of galaxies in the field, we find that this complex represents a hierarchical superstructure spanning approx. 11 Mpc at the redshift approx. 0.247. The multiple peak X-ray morphology and large blue galaxy fraction of A2125 indicate that the cluster is undergoing a coalescence of subunits. The superstructure contains two additional clusters, projected at distances of only 3 and 4.3 Mpc from A2125. The most interesting feature is, however, the low-surface-brightness X-ray emission from a moderate galaxy concentration away from individual clusters. The emission likely arises in a hot (approx. 10(exp 7) K) intergalactic medium, as predicted in N-body/hydro simulations of structure formation. These results demonstrate the potential of X-ray observations as a powerful tool to study the large-scale structure of the universe.

Wang, Q. Daniel

1997-01-01

103

The Spatial Distribution of Hard X-Ray Spectral Index and Local Magnetic Reconnection Rate  

E-print Network

The rare phenomenon of ribbon-like hard X-ray (HXR) sources up to 100 keV found in the 2005 May 13 M8.0 flare observed with the \\textit{Reuven Ramaty High Energy Solar Spectroscopic Imager} provides detailed information on the spatial distribution of flare HXR emission. In this Letter, we further investigate the characteristics of HXR emission in this event using imaging spectroscopy, from which we obtain spatially resolved HXR spectral maps during the flare impulsive phase. As a result we found, along a flare ribbon, an anticorrelation relationship between the local HXR flux and the local HXR spectral index. We suggest that this can be regarded as a spatial analog of the well-known temporal soft-hard-soft spectral evolution pattern of the integrated HXR flux. We also found an anticorrelation between HXR spectral index and local electric field along the ribbon, which suggests the electron acceleration by the electric field during flares.

Chang Liu; Jeongwoo Lee; Ju Jing; Dale E. Gary; Haimin Wang

2007-11-08

104

The effect of proton damage on the X-ray spectral response of MOS CCDs for the Swift X-ray telescope  

NASA Astrophysics Data System (ADS)

The effect of non-ionising energy loss of protons in charge-coupled devices is to displace silicon atoms and any dopant materials present from their lattice positions to form lattice defects which in turn can trap electrons (IEEE Trans. Nucl. Sci. NS-40 (1993) 1628). A CCD operating as a photon counter for X-ray spectroscopy relies on the efficient transfer of charge from one region to another. The number of defects produced will reduce the charge transfer efficiency and hence degrade the spectral resolution of the energy distribution of interest (Jet-X Project Document: JET-X(94) UL-230 WP2220 (1994)). The Swift X-ray telescope will be equipped with a single EPIC MOS CCD22 as developed for the XMM project SPIE 3445 (1998) 13. It is the aim of this study to determine the effect of the radiation environment on the performance of the CCD and its impact on the scientific objective of the X-ray telescope, to probe the X-ray afterglow of gamma-ray bursts.

Ambrosi, R. M.; Short, A. D. T.; Abbey, A. F.; Wells, A. A.; Smith, D. R.

2002-04-01

105

X-ray spectral variability of LINERs selected from the Palomar sample  

NASA Astrophysics Data System (ADS)

Context. Variability is a general property of active galactic nuclei (AGN). The way in which these changes occur at X-rays is not yet clearly understood. In the particular case of low-ionization nuclear emission line region (LINER) nuclei, variations on the timescales from months to years have been found for some objects, but the main driver of these changes is still debated. Aims: The main purpose of this work is to investigate the X-ray variability in LINERs, including the main driver of these variations, and to search for possible differences between type 1 and 2 objects. Methods: We examined the 18 LINERs in the Palomar sample with data retrieved from the Chandra and/or XMM-Newton archives that correspond to observations gathered at different epochs. All the spectra for the same object were fitted simultaneously to study long-term variations. The nature of the variability patterns were studied by allowing different parameters to vary during the spectral fit. Whenever possible, short-term variations from the analysis of the light curves and long-term UV variability were studied. Results: Short-term variations are not reported in X-rays. Three LINERs are classified as non-AGN candidates in X-rays, all of them are Compton-thick candidates; none of them show variations at these frequencies, and two of them vary in the UV. Long-term X-ray variations were analyzed in 12 out of 15 AGN candidates; about half of them showed variability (7 out of the 12). At UV frequencies, most of the AGN candidates with available data are variable (five out of six). Thus, 13 AGN candidates are analyzed at UV and/or X-rays, ten of which are variable at least in one energy band. None of the three objects that do not vary in X-rays have available UV data. This means that variability on long-timescales is very common in LINERs. These X-ray variations are mainly driven by changes in the nuclear power, while changes in absorptions are found only for NGC 1052. We do not find any difference between type 1 and 2 LINERs, neither in the number of variable cases (three out of five type 1 and four out of seven type 2 LINERs), nor in the nature of the variability pattern. We find indications of an anticorrelation between the slope of the power law, ?, and the Eddington ratio. Conclusions: LINERs are definitely variable sources irrespective of whether they are classified as optical type 1 or 2. Their BH masses, accretion rates, and variability timescales place them in the same plane as more powerful AGN at X-rays. However, our results suggest that the accretion mechanism in LINERs may be different. UV variations of some type 2 LINERs were found, this could support the hypothesis of a torus that disappears at low luminosities. Appendices are available in electronic form at http://www.aanda.org

Hernández-García, L.; González-Martín, O.; Masegosa, J.; Márquez, I.

2014-09-01

106

The GALAXIES beamline at the SOLEIL synchrotron: inelastic X-ray scattering and photoelectron spectroscopy in the hard X-ray range.  

PubMed

The GALAXIES beamline at the SOLEIL synchrotron is dedicated to inelastic X-ray scattering (IXS) and photoelectron spectroscopy (HAXPES) in the 2.3-12?keV hard X-ray range. These two techniques offer powerful complementary methods of characterization of materials with bulk sensitivity, chemical and orbital selectivity, resonant enhancement and high resolving power. After a description of the beamline components and endstations, the beamline capabilities are demonstrated through a selection of recent works both in the solid and gas phases and using either IXS or HAXPES approaches. Prospects for studies on liquids are discussed. PMID:25537606

Rueff, J P; Ablett, J M; Céolin, D; Prieur, D; Moreno, Th; Balédent, V; Lassalle-Kaiser, B; Rault, J E; Simon, M; Shukla, A

2015-01-01

107

Variability of Soft X-ray Spectral Shape in Blazars Observed by ROSAT  

E-print Network

In paper 1 (Cheng et al. 2001) we have shown that the soft X-ray spectra of two types of Seyfert 1 galaxies statistically vary differently with increasing intensity. In order to understand how the spectrum of blazars changes, the spectral shape variability of 18 blazars observed by ROSAT/PSPC mode are studied by presenting the correlation of Hardness Ratio 1 versus Count Rates (HR1-CTs). According to our criteria, 10 blazars show a positive HR1-CTs relation, and only 2 blazars display an anti-correlation of HR1 versus CTs. The rest 6 blazars do not indicate any clear correlation. From these we can see that most blazars of our sample statistically show a hardening spectrum during overall flux increase, though some vary randomly. By investigating the photon index of these objects and different radiation theories, we argue that the dominance of the synchrotron or inverse Compton emission in the soft X-ray band may interpret the dichotomy of spectral variability well, and that different spectral variations might represent a sequence of synchrotron peaked frequency.

Linpeng Cheng; Yongheng Zhao; Janyan Wei

2001-10-30

108

Infrared to x-ray spectral energy distributions of high redshift quasars  

NASA Technical Reports Server (NTRS)

We have observed 14 quasars with z greater than 2.8 with the ROSAT-PSPC, and detected 12 of them, including the z=4.11 quasar 0000-263. We present the first x-ray spectrum of a radio quiet quasar with z greater than 3, 1946+768. Its x-ray spectrum is consistent with a power law with spectral index alpha(sub E)=1.8(sup +2.1, sub -1.4) and no evidence for absorption in excess of the galactic column (alpha(sub E)=1.00(sup +0.28, sub -0.32) assuming N(sub H)=N(sub H)(Gal)). A Position Sensitive Proportional Counter (PSPC) hardness ratio is used to constrain the x-ray spectral properties of the quasars for which there were less than 100 photons detected. For the radio quiet quasars, (alpha(sub E)) approximately equals 1.2, if one assumes that there is no absorption in excess of the galactic column. We combine the x-ray data with new ground based optical and near-IR spectrophotometry obtained at the Steward 2.3 m and Multiple Mirror Telescope, and data from the literature. The spectral energy distributions are compared to those of low redshift objects. For the radio quiet quasars with z greater than 2.5, the mean (alpha(sub ox)) is approximately 1.8. This is larger than the mean for quasars with z less than 2.5, but consistent with the expected value for quasars with the high optical luminosities of the objects in this sample. For the radio-loud quasars, (alpha(sub ox)) is approximately 1.4, independent of redshift. This is smaller than the expected value for the optically luminous, high redshift objects in this sample, if they are mostly GHz peaked radio sources and hence comparable to steep-spectrum, compact radio sources at lower redshift. Finally, we compare the spectral energy distributions of two representative objects to the predicted spectrum of a thin accretion disk in the Kerr geometry, and discuss the uncertainties in deriving black hole masses and mass accretion rates.

Bechtold, Jill; Elvis, Martin; Fiore, Fabrizio; Kuhn, Olga; Cutri, Roc M.; Mcdowell, Jonathan C.; Rieke, Marcia; Siemiginowska, Aneta; Wilkes, Belinda J.

1994-01-01

109

Deep galaxy count predictions in the radio, infrared, and X-ray spectral bands  

NASA Technical Reports Server (NTRS)

The existence of a dominant population of strongly evolving starburst sources at moderate redshift is a plausible explanation for the excess number of faint blue galaxies detected in deep sky surveys. Multiwavelength observations at faint magnitudes would allow the existence of such a population to be confirmed. We use observed luminosity correlations and physical properties of known starburst galaxies to predict their contribution to the deep radio, infrared, and X-ray counts, as well as to the diffuse extragalactic background radiation in these various spectral bands.

Treyer, Marie-Agnes; Silk, Joseph

1993-01-01

110

Spectral and Timing Nature of the Symbiotic X-Ray Binary 4U 1954+319: The Slowest Rotating Neutron Star in an X-Ray Binary System  

NASA Astrophysics Data System (ADS)

The symbiotic X-ray binary (SyXB) 4U 1954+319 is a rare system hosting a peculiar neutron star (NS) and an M-type optical companion. Its ~5.4 hr NS spin period is the longest among all known accretion-powered pulsars and exhibited large (~7%) fluctuations over 8 yr. A spin trend transition was detected with Swift/BAT around an X-ray brightening in 2012. The source was in quiescent and bright states before and after this outburst based on 60 ks Suzaku observations in 2011 and 2012. The observed continuum is well described by a Comptonized model with the addition of a narrow 6.4 keV Fe-K? line during the outburst. Spectral similarities to slowly rotating pulsars in high-mass X-ray binaries, its high pulsed fraction (~60%-80%), and the location in the Corbet diagram favor high B-field (gsim 1012 G) over a weak field as in low-mass X-ray binaries. The observed low X-ray luminosity (1033-1035 erg s-1), probable wide orbit, and a slow stellar wind of this SyXB make quasi-spherical accretion in the subsonic settling regime a plausible model. Assuming a ~1013 G NS, this scheme can explain the ~5.4 hr equilibrium rotation without employing the magnetar-like field (~1016 G) required in the disk accretion case. The timescales of multiple irregular flares (~50 s) can also be attributed to the free-fall time from the Alfvén shell for a ~1013 G field. A physical interpretation of SyXBs beyond the canonical binary classifications is discussed.

Enoto, Teruaki; Sasano, Makoto; Yamada, Shin'ya; Tamagawa, Toru; Makishima, Kazuo; Pottschmidt, Katja; Marcu, Diana; Corbet, Robin H. D.; Fuerst, Felix; Wilms, Jörn

2014-05-01

111

Artificial Temperature Anisotropy of Crystals in X-Ray Frequency Range  

SciTech Connect

The effect of artificial temperature anisotropy of crystals in X-ray frequency range was observed for the first time and an effort to theoretically interpret this effect in Bragg-Laue diffraction case was made. It was established that an isotropic crystal optically turns into an artificially anisotropic one with optical axis along the direction of applied external influence as a symmetry axis, giving rise to the double refraction.

Mkrtchyan, Vahram P.; Gasparyan, Laura G.; Balyan, Minas K. [Department of solid state physics, Yerevan State University, Alex Manoogian 1, 0025 Yerevan (Armenia)

2010-04-06

112

pyblocxs: Bayesian Low-Counts X-ray Spectral Analysis in Sherpa  

NASA Astrophysics Data System (ADS)

Typical X-ray spectra have low counts and should be modeled using the Poisson distribution. However, ?2 statistic is often applied as an alternative and the data are assumed to follow the Gaussian distribution. A variety of weights to the statistic or a binning of the data is performed to overcome the low counts issues. However, such modifications introduce biases or/and a loss of information. Standard modeling packages such as XSPEC and Sherpa provide the Poisson likelihood and allow computation of rudimentary MCMC chains, but so far do not allow for setting a full Bayesian model. We have implemented a sophisticated Bayesian MCMC-based algorithm to carry out spectral fitting of low counts sources in the Sherpa environment. The code is a Python extension to Sherpa and allows to fit a predefined Sherpa model to high-energy X-ray spectral data and other generic data. We present the algorithm and discuss several issues related to the implementation, including flexible definition of priors and allowing for variations in the calibration information.

Siemiginowska, A.; Kashyap, V.; Refsdal, B.; van Dyk, D.; Connors, A.; Park, T.

2011-07-01

113

Exact Solution for the Hypergeometric Green's Function Describing Spectral Formation in X-Ray Pulsars  

E-print Network

An eigenfunction expansion method involving hypergeometric functions is used to solve the partial differential equation governing the transport of radiation in an X-ray pulsar accretion column containing a radiative shock. The procedure yields the exact solution for the Green's function, which describes the scattering of monochromatic radiation injected into the column from a source located near the surface of the star. Collisions between the injected photons and the infalling electrons cause the radiation to gain energy as it diffuses through the gas and gradually escapes by passing through the walls of the column. The presence of the shock enhances the energization of the radiation and creates a power-law spectrum at high energies, which is typical for a Fermi process. The analytical solution for the Green's function provides important physical insight into the spectral formation process in X-ray pulsars, and it also has direct relevance for the interpretation of spectral data for these sources. Additional interesting mathematical aspects of the problem include the establishment of a closed-form expression for the quadratic normalization integrals of the orthogonal eigenfunctions, and the derivation of a new summation formula involving products of hypergeometric functions. By taking various limits of the general expressions, we also develop new linear and bilinear generating functions for the Jacobi polynomials.

Peter A. Becker

2005-05-06

114

Exact solution for the hypergeometric Green's function describing spectral formation in x-ray pulsars  

SciTech Connect

An eigenfunction expansion method involving hypergeometric functions is used to solve the partial differential equation governing the transport of radiation in an x-ray pulsar accretion column containing a radiative shock. The procedure yields the exact solution for the Green's function, which describes the scattering of monochromatic radiation injected into the column from a source located near the surface of the star. Collisions between the injected photons and the infalling electrons cause the radiation to gain energy as it diffuses through the gas and gradually escapes by passing through the walls of the column. The presence of the shock enhances the energization of the radiation and creates a power-law spectrum at high energies, which is typical for a Fermi process. The analytical solution for the Green's function provides important physical insight into the spectral formation process in x-ray pulsars, and it also has direct relevance for the interpretation of spectral data for these sources. Additional interesting mathematical aspects of the problem include the establishment of a closed-form expression for the quadratic normalization integrals of the orthogonal eigenfunctions, and the derivation of a new summation formula involving products of hypergeometric functions. By taking various limits of the general expressions, we also develop new linear and bilinear generating functions for the Jacobi polynomials.

Becker, Peter A. [Center for Earth Observing and Space Research, School of Computational Sciences, George Mason University, Fairfax, Virginia 22030-4444 (United States)

2005-05-01

115

Search for X-ray Spectral Features in Two BL Lac Objects  

NASA Technical Reports Server (NTRS)

This grant covered the analysis and interpretation of astrophysical data obtained with the XMM-Newton satellite mission. BL Lac objects are active galactic nuclei that exhibit unusually strong polarization and variability, and are also missing the usual strong optical/ultraviolet emission lines. They are typically strong X-ray sources, but this is the first survey gathering high-quality spectral data from a significant number of these objects. The observations were successful, and all data (for objects in this proposal as well as that of Dr. Perlman s) were of very good quality, as expected. We find that the X-ray spectra of most of these objects are well described by a power-law after allowing for low-energy absorption that can be attributed to neutral gas in the line of sight, presumably located in our own Galaxy. However, in some cases we see indications of a deviation from power-law behavior in the sense that the spectrum appears to be steepening (softening) to higher energies. We are developing a theoretical model in which the steepening is a result of energy-dependent cooling of the radiating particles.We searched for discrete spectral features that might be intrinsic to the objects or their host galaxies, but we found none at the level of sensitivity provided by these data. These are interestingly strong upper bounds.

2003-01-01

116

The Formal Underpinnings of the Response Functions Used in X-Ray Spectral Analysis  

NASA Astrophysics Data System (ADS)

This work provides an in-depth mathematical description of the response functions that are used for spatial and spectral analysis of X-ray data. The use of such functions is well known to anyone familiar with the analysis of X-ray data where they may be identified with the quantities contained in the ancillary response file (ARF), the redistribution matrix file (RMF), and the exposure map. Starting from first principles, explicit mathematical expressions for these functions, for both imaging and dispersive modes, are arrived at in terms of the underlying instrumental characteristics of the telescope including the effects of pointing motion. The response functions are presented in the context of integral equations relating the expected detector count rate to the source spectrum incident upon the telescope. Their application to the analysis of several source distributions is considered. These include multiple, possibly overlapping, spectrally distinct point sources, as well as extended sources. Assumptions and limitations behind the usage of these functions, as well as their practical computation, are addressed.

Davis, John E.

2001-02-01

117

Analysis of nuclear materials by energy dispersive x-ray fluorescence and spectral effects of alpha decay  

SciTech Connect

Energy dispersive X-ray fluorescence (EDXRF) spectra collected from alpha emitters are complicated by artifacts inherent to the alpha decay process, particularly when using portable instruments. For example, {sup 239}Pu EDXRF spectra exhibit a prominent uranium L X-ray emission peak series due to sample alpha decay rather than source-induced X-ray fluorescence. A portable EDXRF instrument was used to collect spectra from plutonium, americium, and a Pu-contaminated steel sample. The plutonium sample was also analyzed by wavelength dispersive XRF to demonstrate spectral differences observed when using these very different instruments.

Worley, Christopher G [Los Alamos National Laboratory

2009-01-01

118

Multilayer X-ray mirrors for the (4.4-5)-nm carbon-window spectral region  

SciTech Connect

Cr/C-based multilayer X-ray mirrors intended for the reflection of X-ray radiation in the 'carbon-window' spectral region ({lambda} = 4.4-5 nm) are fabricated and studied. The structures are formed by magnetron sputtering at different deposition parameters. Under normal incidence, record reflection coefficients up to 15% are reached. The structural parameters of the mirrors are investigated by reflectometry at wavelengths of 0.154 and 4.47 nm.

Andreev, S. S.; Barysheva, M. M.; Vainer, Yu. A.; Gaikovich, P. K.; Pariev, D. E., E-mail: Pariev@ipmras.ru; Pestov, A. E.; Salashchenko, N. N.; Chkhalo, N. I. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

2013-05-15

119

Multi-Spectral Solar Telescope Array. II - Soft X-ray/EUV reflectivity of the multilayer mirrors  

NASA Technical Reports Server (NTRS)

The Multispectral Solar Telescope Array is a rocket-borne observatory which encompasses seven compact soft X-ray/EUV, multilayer-coated, and two compact far-UV, interference film-coated, Cassegrain and Ritchey-Chretien telescopes. Extensive measurements are presented on the efficiency and spectral bandpass of the X-ray/EUV telescopes. Attention is given to systematic errors and measurement errors.

Barbee, Troy W., Jr.; Weed, J. W.; Hoover, Richard B.; Allen, Maxwell J.; Lindblom, Joakim F.; O'Neal, Ray H.; Kankelborg, Charles C.; Deforest, Craig E.; Paris, Elizabeth S.; Walker, Arthur B. C., Jr.

1991-01-01

120

Correlated Temporal and Spectral Variability in Neutron Star and Black Hole X-Ray Binaries  

NASA Technical Reports Server (NTRS)

The variability of neutron star and black hole X-ray sources has several dimensions, because of the roles played by different important time-scales. The variations on time scales of hours, weeks, and months, ranging from 50% to orders of magnitude, arise out of changes in the flow in the disk. The most important driving forces for those changes are probably various possible instabilities in the disk, though there may be effects with other dominant causes. The changes in the rate of flow appear to be associated with changes in the flow's configuration, as the accreting material approaches the compact object, for there are generally correlated changes in both the X-ray spectra and the character of the faster temporal variability. There has been a lot of progress in tracking these correlations, both for Z and Atoll neutron star low-mass X-ray binaries, and for black hole binaries. I will discuss these correlations and what they tell us about the physical states of the systems.

Swank, J.

2006-01-01

121

The Spectral Evolution of Solar Flare Hard X-Ray Emission Observed with BATSE  

NASA Technical Reports Server (NTRS)

We present a more detailed characterization of spectral evolution in solar flare hard X-ray emission than has been previously described. Our characterization is consistent with some earlier results but utilizes higher time resolution data and reveals nuances in spectral evolution that have never been reported. We employ an underutilized data set, the Burst and Transient Source Experiment (BATSE) solar flare catalog, for our investigation and different methodology than previous studies. Our findings support the conclusion that properties of the particle Abstract: acceleration mechanism in flares, such as the acceleration rate or efficiency, are indeed important to understanding spectral evolution. On the other hand, time-of-flight models, which assume accelerator properties to be negligible, cannot explain the observed detailed spectral evolution, and correlations that we would expect to exist between spectral evolution patterns and parameters derived from time-of-flight model inversions are not supported by the data. In this fashion, we establish an observational context in which to interpret future High Energy Solar Spectroscopic Imager (HESSI) observations and delineate some constraints for theoretical models of particle acceleration.

Newton, Elizabeth K.; Giblin, Timothy

2000-01-01

122

The Multi-Spectral Solar Telescope Array. II - Soft X-ray/EUV reflectivity of the multilayer mirrors  

NASA Technical Reports Server (NTRS)

We have developed seven compact soft X-ray/EUV (XUV) multilayer coated and two compact FUV interference film coated Cassegrain and Ritchey-Chretien telescopes for a rocket borne observatory, the Multi-Spectral Solar Telescope Array. We report here on extensive measurements of the efficiency and spectral bandpass of the XUV telescopes carried out at the Stanford Synchrotron Radiation Laboratory.

Barbee, Troy W., Jr.; Weed, J. W.; Hoover, Richard B. C., Jr.; Allen, Max J.; Lindblom, Joakim F.; O'Neal, Ray H.; Kankelborg, Charles C.; Deforest, Craig E.; Paris, Elizabeth S.; Walker, Arthur B. C.

1992-01-01

123

Timing and spectral properties of transient X-ray pulsar GRO J1008-57  

NASA Astrophysics Data System (ADS)

We present the timing and spectral properties of the Be transient high mass X-ray binary pulsar GRO J1008-57 using Suzaku observation in the declining phase of its 2007 outburst. Pulsations with a period of 93.737s were clearly detected in the light curves of the pulsar up to energy of ˜100 keV. The pulse profile was found to be strongly energy dependent, a double peaked profile at soft X-ray energy bands (< 8 keV) and a single peaked smooth profile at hard X-rays. The broadband energy spectrum of the pulsar is well described with three different continuum models viz. (i) a high energy cut-off power-law, (ii) a Negative and Positive power-law with Exponential cut-off (NPEX), and (iii) a partial covering power-law with high energy cut-off. In spite of large value of absorption column density in the direction of the pulsar, a blackbody component of temperature ˜0.17 keV for the soft excess was required for the first two continuum models. A narrow iron K_? emission line was detected in the pulsar spectrum. The partial covering model, however, is found to explain the phase averaged and phase resolved spectra well. The dip like feature in the pulse profile can be explained by the presence of an additional absorption component with high column density and covering fraction at the same pulse phase. The details of the results will be presented.

Naik, Sachindra; Paul, Biswajit; Vadawale, S. V.

124

Processing of spectrally resolved x-ray images of inertial confinement fusion implosion cores recorded with multimonochromatic x-ray imagers  

SciTech Connect

We discuss the processing of data recorded with multimonochromatic x-ray imagers (MMI) in inertial confinement fusion experiments. The MMI records hundreds of gated, spectrally resolved images that can be used to unravel the spatial structure of the implosion core. In particular, we present a new method to determine the centers in all the array of images, a better reconstruction technique of narrowband implosion core images, two algorithms to determine the shape and size of the implosion core volume based on reconstructed broadband images recorded along three-quasiorthogonal lines of sight, and the removal of artifacts from the space-integrated spectra.

Nagayama, T.; Mancini, R. C.; Florido, R. [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States); Tommasini, R.; Koch, J. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Delettrez, J. A.; Regan, S. P.; Smalyuk, V. A. [Laboratory for Laser Energetics, University of Rochester, New York 14623 (United States)

2011-05-01

125

Development of an XSPEC-Based Spectral Analysis System for the Coded-Aperture Hard X-ray Balloon Payload EXITE2  

E-print Network

We present the spectral analysis system for the second-generation Energetic X-ray Imaging Telescope Experiment (EXITE2) balloon payload. EXITE2 is an imaging hard X-ray telescope using a coded-aperture mask and a NaI/CsI phoswich detector operating in the energy range 20--600 keV. The instrument was flown on a high-altitude scientific balloon from Ft. Sumner, NM on 1997 May 7-8. We describe the details of the EXITE2 spectral analysis system, with emphasis on those aspects peculiar to coded-aperture instruments. In particular, we have made our analysis compatible with the standard X-ray spectral fitting package XSPEC by generating a response matrix in the appropriate format including all the effects of a coded-aperture system. The use of XSPEC, which may be a first for coded-aperture data, permits great flexibility in the fitting of spectral models. The additional effects of our phoswich system, or any other detector-specific considerations, may be easily included as well. We test our spectral analysis using observations of the Crab Nebula, and find that the EXITE2 Crab spectrum is consistent with those recorded by previous instruments operating in this energy range.

P. F. Bloser; Y. Chou; J. E. Grindlay; T. Narita; G. Monnelly

2001-09-07

126

The First Hard X-Ray Power Spectral Density Functions of Active Galactic Nucleus  

NASA Astrophysics Data System (ADS)

We present results of our power spectral density (PSD) analysis of 30 active galactic nuclei (AGNs) using the 58 month light curves from Swift's Burst Alert Telescope (BAT) in the 14-150 keV band. PSDs were fit using a Monte Carlo based algorithm to take into account windowing effects and measurement error. All but one source were found to be fit very well using an unbroken power law with a slope of ~ - 1, consistent at low frequencies with previous studies in the 2-10 keV band, with no evidence of a break in the PSD. For five of the highest signal-to-noise ratio sources, we tested the energy dependence of the PSD and found no significant difference in the PSD at different energies. Unlike previous studies of X-ray variability in AGNs, we do not find any significant correlations between the hard X-ray variability and different properties of the AGN including luminosity and black hole mass. The lack of break frequencies and correlations seem to indicate that AGNs are similar to the high state of Galactic black holes.

Shimizu, T. Taro; Mushotzky, Richard F.

2013-06-01

127

THE FIRST HARD X-RAY POWER SPECTRAL DENSITY FUNCTIONS OF ACTIVE GALACTIC NUCLEUS  

SciTech Connect

We present results of our power spectral density (PSD) analysis of 30 active galactic nuclei (AGNs) using the 58 month light curves from Swift's Burst Alert Telescope (BAT) in the 14-150 keV band. PSDs were fit using a Monte Carlo based algorithm to take into account windowing effects and measurement error. All but one source were found to be fit very well using an unbroken power law with a slope of {approx} - 1, consistent at low frequencies with previous studies in the 2-10 keV band, with no evidence of a break in the PSD. For five of the highest signal-to-noise ratio sources, we tested the energy dependence of the PSD and found no significant difference in the PSD at different energies. Unlike previous studies of X-ray variability in AGNs, we do not find any significant correlations between the hard X-ray variability and different properties of the AGN including luminosity and black hole mass. The lack of break frequencies and correlations seem to indicate that AGNs are similar to the high state of Galactic black holes.

Shimizu, T. Taro; Mushotzky, Richard F., E-mail: tshimizu@astro.umd.edu [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

2013-06-10

128

Final Report of B548129: Spectral Analysis of Soft X-Ray Data from NSTX  

SciTech Connect

We present a summary of work performed under subcontract B548129 'Spectral Analysis of Soft X-Ray Data from NSTX'. This summary is comprised of papers and poster presentations prepared under this subcontract. The X-ray and Extreme Ultraviolet Spectrometer (XEUS) has been used to monitor the line emission from various impurity ions on NSTX, in particular the K-shell emission of helium-like and hydrogen-like B, C, N, and O. While C VI typically dominates the spectrum, unusually strong emission from N VII has been observed in multiple discharges during the past run campaign. In this case, the nitrogen concentration can exceed that of carbon by an order of magnitude. Time-dependent measurements show that the nitrogen concentration builds up over the course of the discharge and coincides with a build up of boron. In a few cases we observed several unknown lines. These are clearly lines from heavy impurities, possibly molybdenum. Some of these lines can be explained by the emission from Ti XIII.

Lepson, J K; Jernigan, J G; Beiersdorfer, P

2007-11-09

129

Density and atomic number measurements with spectral x-ray attenuation method  

NASA Astrophysics Data System (ADS)

X-ray attenuation measurements are widely used in medical and industrial applications. The usual results are one- to three-dimensional representations of the attenuation coefficient ?(r). In this paper, we present the ?Z projection algorithm for obtaining the density ?(r) and atomic number Z(r) with an energy-resolving x-ray method. As input data the algorithm uses at least two measurements ?1,?2,… with different spectral weightings of the source spectrum S(E) and/or detector sensitivity D(E). Analytically, ? is a function of ?1-c?2, c=const, and Z is a function of ?1/?2. The full numerical treatment yields ?(?1,?2) and Z(?1,?2) with S(E) and D(E) as commutative parametric functions. We tested the method with dual-energy computed tomography measurements of an organic sample and a set of chemical solutions with predefined ? and Z. The resulting images show ? and Z as complementary information: The density ? reflects the morphology of the objects, whereas the atomic number Z=number of electrons/atom describes the material distribution. For our experimental setup we obtain an absolute precision of 0.1 for Z and 20 mg/cm3 for ?. The ?Z projection can potentially lead to these classes of quantitative information for various scientific, industrial, and medical applications.

Heismann, B. J.; Leppert, J.; Stierstorfer, K.

2003-08-01

130

High-resolution X-ray spectra of solar flares. IV - General spectral properties of M type flares  

NASA Technical Reports Server (NTRS)

The spectral characteristics in selected narrow regions of the X-ray spectrum of class M solar flares are analyzed. High-resolution spectra in the ranges 1.82-1.97, 2.98-3.07, 3.14-3.24 and 8.26-8.53 A, which contain lines important for the determination of electron temperature and departure from ionization equilibrium, were recorded by spaceborne Bragg crystal spectrometers. Temperatures of up to 20,000,000 K are obtained from line ratios during flare rise phases in M as well as X flares, while in the decay phase the calcium temperature can be as low as 8,000,000 K, which is significantly lower than in X flares. Large nonthermal motions (on the order of 130 km/sec at most) are also observed in M as well as X flares, which are largest during the soft X-ray rise phase. Finally, it is shown that the method proposed by Gabriel and Phillips (1979) for detecting departures of electrons from Maxwellian velocity distributions is not sufficiently sensitive to give reliable results for the present data.

Feldman, U.; Doschek, G. A.; Kreplin, R. W.; Mariska, J. T.

1980-01-01

131

Hard X-ray timing and spectral properties of PSR B0540-69  

NASA Astrophysics Data System (ADS)

We report the hard X-ray properties of the young Crab-like LMC pulsar PSR B0540-69, using archival RXTE PCA (2-60 keV) and RXTE HEXTE (15-250 keV) data. Making use of the very long effective exposure of 684 ks, we derived a very detailed master pulse profile for energies 2-20 keV. We confirm the broad single-pulse shape with a dip in the middle and with a significant fine structure to the left of the dip. For the first time pulse profiles in the 10-50 keV energy interval are shown. Remarkably, the coarse pulse shape is stable from the optical up to X-ray energies analogous to the case of the Crab pulsar (PSR B0531+21). The profiles can be described with two Gaussians with a phase separation of ~ 0.2; the distribution of the ratios between the two components from the optical to the X-ray range is consistent with being flat. Therefore we cannot conclude that the profile consists of two distinct components. We also derived a new total pulsed spectrum in the ~ 0.01-50 keV range in a consistent analysis including also archival ROSAT PSPC (0.01-2.5 keV) data. This spectrum cannot be described by a single power-law, but requires an additional energy dependent term. The bending of the spectrum around 10 keV resembles that of the Crab pulsar spectrum. Although model calculations using Outer Gap scenarios could probably explain the high-energy characteristics of PSR B0540-69 as they successfully do for the Crab, our measurements do not entirely agree with the latest calculations by Zhang & Cheng (\\cite{zhang-theorie}). The small discrepancies are likely to be caused by uncertainties in the pulsar's geometry.

de Plaa, J.; Kuiper, L.; Hermsen, W.

2003-03-01

132

A cascaded model of spectral distortions due to spectral response effects and pulse pileup effects in a photon-counting x-ray detector for CT  

SciTech Connect

Purpose: Energy discriminating, photon-counting detectors (PCDs) are an emerging technology for computed tomography (CT) with various potential benefits for clinical CT. The photon energies measured by PCDs can be distorted due to the interactions of a photon with the detector and the interaction of multiple coincident photons. These effects result in distorted recorded x-ray spectra which may lead to artifacts in reconstructed CT images and inaccuracies in tissue identification. Model-based compensation techniques have the potential to account for the distortion effects. This approach requires only a small number of parameters and is applicable to a wide range of spectra and count rates, but it needs an accurate model of the spectral distortions occurring in PCDs. The purpose of this study was to develop a model of those spectral distortions and to evaluate the model using a PCD (model DXMCT-1; DxRay, Inc., Northridge, CA) and various x-ray spectra in a wide range of count rates. Methods: The authors hypothesize that the complex phenomena of spectral distortions can be modeled by: (1) separating them into count-rate independent factors that we call the spectral response effects (SRE), and count-rate dependent factors that we call the pulse pileup effects (PPE), (2) developing separate models for SRE and PPE, and (3) cascading the SRE and PPE models into a combined SRE+PPE model that describes PCD distortions at both low and high count rates. The SRE model describes the probability distribution of the recorded spectrum, with a photo peak and a continuum tail, given the incident photon energy. Model parameters were obtained from calibration measurements with three radioisotopes and then interpolated linearly for other energies. The PPE model used was developed in the authors’ previous work [K. Taguchi et al., “Modeling the performance of a photon counting x-ray detector for CT: Energy response and pulse pileup effects,” Med. Phys. 38(2), 1089–1102 (2011)]. The agreement between the x-ray spectra calculated by the cascaded SRE+PPE model and the measured spectra was evaluated for various levels of deadtime loss ratios (DLR) and incident spectral shapes, realized using different attenuators, in terms of the weighted coefficient of variation (COV{sub W}), i.e., the root mean square difference weighted by the statistical errors of the data and divided by the mean. Results: At low count rates, when DLR < 10%, the distorted spectra measured by the DXMCT-1 were in agreement with those calculated by SRE only, with COV{sub W}'s less than 4%. At higher count rates, the measured spectra were also in agreement with the ones calculated by the cascaded SRE+PPE model; with PMMA as attenuator, COV{sub W} was 5.6% at a DLR of 22% and as small as 6.7% for a DLR as high as 55%. Conclusions: The x-ray spectra calculated by the proposed model agreed with the measured spectra over a wide range of count rates and spectral shapes. The SRE model predicted the distorted, recorded spectra with low count rates over various types and thicknesses of attenuators. The study also validated the hypothesis that the complex spectral distortions in a PCD can be adequately modeled by cascading the count-rate independent SRE and the count-rate dependent PPE.

Cammin, Jochen, E-mail: jcammin1@jhmi.edu, E-mail: ktaguchi@jhmi.edu; Taguchi, Katsuyuki, E-mail: jcammin1@jhmi.edu, E-mail: ktaguchi@jhmi.edu [Division of Medical Imaging Physics, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287 (United States)] [Division of Medical Imaging Physics, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287 (United States); Xu, Jennifer [Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21287 (United States)] [Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21287 (United States); Barber, William C.; Iwanczyk, Jan S.; Hartsough, Neal E. [DxRay, Inc., Northridge, California 91324 (United States)] [DxRay, Inc., Northridge, California 91324 (United States)

2014-04-15

133

Ultrasound artificial anisotropy of crystals in x-ray frequency range  

NASA Astrophysics Data System (ADS)

The effect of ultrasound artificial anisotropy of crystals in X-ray frequency range was observed and an effort to theoretically interpret this effect in Bragg-Laue diffraction case was made. It was established that an isotropic crystal optically turns into an artificially anisotropic one with optical axis along the direction of applied external influence as a symmetry axis, giving rise to the double refraction. Investigations of this kind are important because the results can be applied such as the artificial anisotropy effects in optics (in analogy Kerr effect in optics).

Mkrtchyan, Vahram P.; Gasparyan, Laura G.; Balyan, Minas K.

2010-09-01

134

Development of an XSPEC-Based Spectral Analysis System for the Coded-Aperture Hard X-ray Balloon Payload EXITE2  

E-print Network

We present the spectral analysis system for the second-generation Energetic X-ray Imaging Telescope Experiment (EXITE2) balloon payload. EXITE2 is an imaging hard X-ray telescope using a coded-aperture mask and a NaI/CsI phoswich detector operating in the energy range 20--600 keV. The instrument was flown on a high-altitude scientific balloon from Ft. Sumner, NM on 1997 May 7-8. We describe the details of the EXITE2 spectral analysis system, with emphasis on those aspects peculiar to coded-aperture instruments. In particular, we have made our analysis compatible with the standard X-ray spectral fitting package XSPEC by generating a response matrix in the appropriate format including all the effects of a coded-aperture system. The use of XSPEC, which may be a first for coded-aperture data, permits great flexibility in the fitting of spectral models. The additional effects of our phoswich system, or any other detector-specific considerations, may be easily included as well. We test our spectral analysis using o...

Bloser, P F; Grindlay, J E; Narita, T; Monnelly, G

2001-01-01

135

Relationship between X-ray spectral index and X-ray Eddington ratio for Mrk 335 and Ark 564  

E-print Network

We present a comprehensive flux resolved spectral analysis of the bright Narrow line Seyfert I AGNs, Mrk~335 and Ark~564 using observations by XMM-Newton satellite. The mean and the flux resolved spectra are fitted by an empirical model consisting of two Comptonization components, one for the low energy soft excess and the other for the high energy power-law. A broad Iron line and a couple of low energies edges are required to explain the spectra. For Mrk~335, the 0.3 - 10 keV luminosity relative to the Eddington value, L{$_{X}$}/L$_{Edd}$, varied from 0.002 to 0.06. The index variation can be empirically described as $\\Gamma$ = 0.6 log$_{10}$ L{$_{X}$}/L$_{Edd}$ + 3.0 for $0.005 < L{_{X}}/L_{Edd} < 0.04$. At $ L_{{X}}/L_{Edd} \\sim 0.04$ the spectral index changes and then continues to follow $\\Gamma$ = 0.6 log$_{10}$ L$_{{X}}$/L$_{Edd}$ + 2.7, i.e. on a parallel track. We confirm that the result is independent of the specific spectral model used by fitting the data in the 3 - 10 keV band by only a powe...

Sarma, R; Misra, R; Dewangan, G; Pathak, A; Sarma, J K

2015-01-01

136

The X-ray spectra of galaxies. II - Average spectral properties and emission mechanisms  

NASA Technical Reports Server (NTRS)

The Imaging Proportional Counter data in the Einstein database is used to study the X-ray spectra of normal galaxies. The X-ray emission temperature of spirals is found to be higher on the average than that of ellipticals. This supports the idea that accreting binaries are a major source of X-rays in spirals, while a hot interstellar medium (ISM) is present in ellipticals. The X-ray spectra of Sa galaxies are intermediate between those of ellipticals and spirals, suggesting that these galaxies contain hot gaseous emission as well as emission from accreting binaries. In E and SO galaxies the emission temperature becomes higher with a decreasing X-ray to optical luminosity ratio, which suggests that the emission of X-ray faint early-type galaxies consists of a large evolved stellar component, while the gaseous emission becomes dominant in X-ray brighter galaxies. The group with the lowest X-ray to optical ratio does not follow this trend; in these galaxies a very soft X-ray component, amounting to about half the total X-ray emission, is found in addition to the hard X-ray component. Possible explanations are integrated emission of M stars and a relatively cool ISM. A very soft component is also found in several spiral galaxies. This may indicate that some spirals contain hot gaseous components similar to those seen in NGC 253 and M82.

Kim, D.-W.; Fabbiano, G.; Trinchieri, G.

1992-01-01

137

Absolute x-ray energy calibration over a wide energy range using a diffraction-based iterative method.  

PubMed

In this paper, we report a method of precise and fast absolute x-ray energy calibration over a wide energy range using an iterative x-ray diffraction based method. Although accurate x-ray energy calibration is indispensable for x-ray energy-sensitive scattering and diffraction experiments, there is still a lack of effective methods to precisely calibrate energy over a wide range, especially when normal transmission monitoring is not an option and complicated micro-focusing optics are fixed in place. It is found that by using an iterative algorithm the x-ray energy is only tied to the relative offset of sample-to-detector distance, which can be readily varied with high precision of the order of 10(-5) -10(-6) spatial resolution using gauge blocks. Even starting with arbitrary initial values of 0.1 A?, 0.3 A?, and 0.4 A?, the iteration process converges to a value within 3.5 eV for 31.122 keV x-rays after three iterations. Different common diffraction standards CeO(2), Au, and Si show an energy deviation of 14 eV. As an application, the proposed method has been applied to determine the energy-sensitive first sharp diffraction peak of network forming GeO(2) glass at high pressure, exhibiting a distinct behavior in the pressure range of 2-4 GPa. Another application presented is pair distribution function measurement using calibrated high-energy x-rays at 82.273 keV. Unlike the traditional x-ray absorption-based calibration method, the proposed approach does not rely on any edges of specific elements, and is applicable to the hard x-ray region where no appropriate absorption edge is available. PMID:22755637

Hong, Xinguo; Chen, Zhiqiang; Duffy, Thomas S

2012-06-01

138

Energy dependence of photon-induced K? and K? x-ray production cross-sections for some elements with 38?Z?51 in the energy range 20-50 keV  

NASA Astrophysics Data System (ADS)

The energy dependence of photon-induced K? and K? x-ray production (or x-ray fluorescence) cross-sections for Sr, Y, Mo, Ru, Pd, Ag, In and Sb elements has been studied in the energy range of 20-50 keV using Energy Dispersive X-Ray Fluorescence (EDXRF) Spectrometry. The photon energy dependence of K x-ray production cross-sections was measured with secondary excitation method. A radioisotope point source of 241Am was employed to excite the K x-rays of secondary exciter elements. The L x-ray yields from Th and U were measured to determine IoG (the intensity of exciter K x-rays falling on primary target). The measurements have been made by observing the x-ray emissions with the help of HPGe detector coupled with a multichannel analyzer. The areas of the K? and K? spectral peaks, as well as the net peak areas, have been determined by a fitting process. The measured K? and K? x-ray production cross-sections have been compared with calculated theoretical values in this energy regime. The present experimental results for all the elements were in general agreement with the theoretical values calculated using photoionization cross-sections, fractional rates (based on Hartree-Slater potentials) and fluorescence yields.

Seven, Sabriye

2012-05-01

139

X-ray spectral and timing characteristics of the stars in the young open cluster IC 2391  

NASA Astrophysics Data System (ADS)

We present X-ray spectral and timing analysis of members of the young open cluster IC 2391 observed with the XMM-Newton observatory. We detected 99 X-ray sources by analysing the summed data obtained from MOS1, MOS2 and pn detectors of the EPIC camera; 24 of them are members, or probable members, of the cluster. Stars of all spectral types have been detected, from the early-types to the late-M dwarfs. Despite the capability of the instrument to recognize up to 3 thermal components, the X-ray spectra of the G, K and M members of the cluster are well described with two thermal components (at kT1 ˜ 0.3-0.5 keV and kT2 ˜ 1.0-1.2 keV respectively) while the X-ray spectra of F members require only a softer 1-T model. The Kolmogorov-Smirnov test applied to the X-ray photon time series shows that approximately 46% of the members of IC 2391 are variable with a confidence level >99%. The comparison of our data with those obtained with ROSAT/PSPC, nine years earlier, and ROSAT/HRI, seven years earlier, shows that there is no evidence of significant variability on these time scales, suggesting that long-term variations due to activity cycles similar to that on the Sun are not common, if present at all, among these young stars.

Marino, A.; Micela, G.; Peres, G.; Pillitteri, I.; Sciortino, S.

2005-01-01

140

An optimization model of targets for resonant transition radiation in the X-ray range  

NASA Astrophysics Data System (ADS)

Generation of resonant transition radiation (RTR) is potentially a method to obtain useable fluxes of tuneable, relatively narrow-band soft X-ray radiation from compact (<10 MeV) electron accelerators. The RTR targets to be used are periodic multilayer structures of two materials with low absorption and high refractive-index contrast in the soft X-ray range. We present a model for optimizing the parameters of such targets. The model is based on an extension of the Ginzburg-Franck equation for transition radiation from a single interface. The model also accounts for absorption, elastic scattering, energy spread of the electron beam and inaccuracy in the foil thicknesses. Two examples are treated. First, a multilayer structure consisting of Mo foils and vacuum spacers is optimized for generation of 13.5 nm radiation by an electron beam with energy of 9 MeV. The model predicts a yield of up to 0.045 photons per electron per (eV sr). Second, a multilayer structure consisting of Al foils and vacuum spacers is optimized for generation of 0.83 nm radiation by 150 MeV electrons. For the latter case, the model predicts a yield of up to 3.7 photons per electron per (eV sr).

Corstens, J. M.; van der Wiel, M. J.

2006-09-01

141

Measuring polarization in the X-ray range: New simulation method for gaseous detectors  

NASA Astrophysics Data System (ADS)

In the last few years, many experimental groups developed new instruments to measure linearly polarized X-rays in the energy range of few keV where the dominant interaction process with matter is the photoelectric effect. These instrumental setups are principally based, on micro-pattern gas detectors that are able to measure the photoelectron tracks. These detectors are characterized by many parameters that influence their performance, for example, the gas mixture, the gas pressure, the pitch dimension, the gas electron multiplier (GEM) voltage, etc. Monte Carlo simulations are useful tools to improve these parameters. The Geant4 toolkit has the ability to take into account many detector characteristics. In this work, we suggest Geant4 as a useful toolkit to simulate the photoelectric interaction of linearly polarized X-rays. In particular, we have developed a new calculation of the final state, properly taking into account the direction of the photo-electron. We simulate two experimental setups found in the literature and show that the simulation results obtained are in agreement with the experimental data.

Depaola, G. O.; Longo, F.

2006-10-01

142

Flat panel X-ray detector with reduced internal scattering for improved attenuation accuracy and dynamic range  

DOEpatents

An x-ray detector is disclosed that has had all unnecessary material removed from the x-ray beam path, and all of the remaining material in the beam path made as light and as low in atomic number as possible. The resulting detector is essentially transparent to x-rays and, thus, has greatly reduced internal scatter. The result of this is that x-ray attenuation data measured for the object under examination are much more accurate and have an increased dynamic range. The benefits of this improvement are that beam hardening corrections can be made accurately, that computed tomography reconstructions can be used for quantitative determination of material properties including density and atomic number, and that lower exposures may be possible as a result of the increased dynamic range.

Smith, Peter D. (Santa Fe, NM); Claytor, Thomas N. (White Rock, NM); Berry, Phillip C. (Albuquerque, NM); Hills, Charles R. (Los Alamos, NM)

2010-10-12

143

Advection-dominated Accretion and the Spectral States of Black Hole X-Ray Binaries: Application to Nova MUSCAE 1991  

Microsoft Academic Search

Black hole X-ray binaries (BHXBs) are known to display five distinct spectral states. In order of increasing luminosity these are the quiescent state, low state, intermediate state, high state, and very high state. We present a self-consistent model of accretion flows around black holes that unifies all of these states except the very high state. The model is an extension

Ann A. Esin; Jeffrey E. McClintock; Ramesh Narayan

1997-01-01

144

Parameterization of X-ray mass attenuation coefficients in the energy range of 1-150 keV  

Microsoft Academic Search

Knowledge of X-ray mass attenuation coefficients is necessary when the thick target PIXE method is applied for quantitative elemental analysis of materials. For this purpose, the X-ray mass attenuation coefficients of Veigele [Atom. Data Tables 5 (1973) 51] ave been parameterized in the photon energy range of 1-150 keV for all elements from hydrogen to plutonium (Z = 1-94), taking

J. Braziewicz; E. Braziewicz; M. Pajek

1993-01-01

145

Discovery of Spatial and Spectral Structure in the X-Ray Emission from the Crab Nebula  

Microsoft Academic Search

The Chandra X-Ray Observatory observed the Crab Nebula and pulsar during orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) readout by the Advanced CCD Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray

Martin C. Weisskopf; J. Jeff Hester; Allyn F. Tennant; Ronald F. Elsner; Norbert S. Schulz; Herman L. Marshall; Margarita Karovska; Joy S. Nichols; Douglas A. Swartz; Jeffery J. Kolodziejczak; Stephen L. O'Dell

2000-01-01

146

Removing Spectral Diagnostics of Galactic and Stellar X-Ray Emission from Charged Exchange Recombination  

NASA Technical Reports Server (NTRS)

Our research uses the electron beam ion trap (EBIT) at the Lawrence Livermore National Laboratory to study X-ray emission from the charge exchange (CX) of highly charged ions with neutral gases. The resulting data help to fill a void in existing experimental and theoretical understanding of this atomic physics process, and are needed to explain all or part of the observed X-ray emission from the soft X-ray background, stellar winds, the Galactic Center and Galactic Ridge, supernova ejecta, and photoionized nebulae. Appreciation of the astrophysical relevance of our work continues to grow with the publication of roughly a dozen papers in the past four years describing Chandra and XMM observations of geocoronal and heliospheric CX emission, the temporal variation of such emission and correlation with X-ray emission enhancements observed by ROSAT, the theoretical spatial distribution of that emission, and CX emission around other stars. A similar number of papers were also published during that time describing CX emission from planets and comets. We expect that the launch of ASTRSE2, with its second-generation XRS microcalo- (with 6-eV resolution), will reveal even more clearly the contributions of CX to astrophysical emission. In our EBIT work we collected CX spectra from such ions as H-like and He-like Ne, Ar, and Fe. Our early measurements were made with a high-purity Ge detector, but during the second year we began operation of the first-generation XRS microcalorimeter (a twin of the XRS on ASTRO-E) and greatly improved the resolution of our measurements from roughly 150 eV (FWHM) with the Ge detectors to 10 eV with the XRS. We found that saturation of the XRS counting apparatus, which we described in our proposal as a potential concern, is not a problem for studying CX. During the course of our research, we expanded the number of injection gases permitted by the LLNL safety team, purchased and eventually operated an atomic H source, and clearly demonstrated the feasibility of our longer-range plan. For example, we successfully injected He into EBIT (not a small feat because of the difficulty of maintaining a good vacuum with He and avoiding electrical breakdown) to collect a H-like oxygen CX spectrum. The highest energy CX spectrum recorded with the XRS to date is that of the Ar K-shell emission. These measurements provided the first observation of the relative intensity ratios of resolved He-like singlet and triplet n=2->1 lines. We also carried out measurements of He-like Ne as a function of collision energy (i.e., ion temperature). Significant differences in the resulting x-ray spectra were noted. In all cases, the intensity of high-n H-like Lyman lines is significantly higher than current theoretical CX models predict.

Wargelin, Brad

2004-01-01

147

Image-based spectral distortion correction for photon-counting x-ray detectors  

PubMed Central

Purpose: To investigate the feasibility of using an image-based method to correct for distortions induced by various artifacts in the x-ray spectrum recorded with photon-counting detectors for their application in breast computed tomography (CT). Methods: The polyenergetic incident spectrum was simulated with the tungsten anode spectral model using the interpolating polynomials (TASMIP) code and carefully calibrated to match the x-ray tube in this study. Experiments were performed on a Cadmium-Zinc-Telluride (CZT) photon-counting detector with five energy thresholds. Energy bins were adjusted to evenly distribute the recorded counts above the noise floor. BR12 phantoms of various thicknesses were used for calibration. A nonlinear function was selected to fit the count correlation between the simulated and the measured spectra in the calibration process. To evaluate the proposed spectral distortion correction method, an empirical fitting derived from the calibration process was applied on the raw images recorded for polymethyl methacrylate (PMMA) phantoms of 8.7, 48.8, and 100.0 mm. Both the corrected counts and the effective attenuation coefficient were compared to the simulated values for each of the five energy bins. The feasibility of applying the proposed method to quantitative material decomposition was tested using a dual-energy imaging technique with a three-material phantom that consisted of water, lipid, and protein. The performance of the spectral distortion correction method was quantified using the relative root-mean-square (RMS) error with respect to the expected values from simulations or areal analysis of the decomposition phantom. Results: The implementation of the proposed method reduced the relative RMS error of the output counts in the five energy bins with respect to the simulated incident counts from 23.0%, 33.0%, and 54.0% to 1.2%, 1.8%, and 7.7% for 8.7, 48.8, and 100.0 mm PMMA phantoms, respectively. The accuracy of the effective attenuation coefficient of PMMA estimate was also improved with the proposed spectral distortion correction. Finally, the relative RMS error of water, lipid, and protein decompositions in dual-energy imaging was significantly reduced from 53.4% to 6.8% after correction was applied. Conclusions: The study demonstrated that dramatic distortions in the recorded raw image yielded from a photon-counting detector could be expected, which presents great challenges for applying the quantitative material decomposition method in spectral CT. The proposed semi-empirical correction method can effectively reduce these errors caused by various artifacts, including pulse pileup and charge sharing effects. Furthermore, rather than detector-specific simulation packages, the method requires a relatively simple calibration process and knowledge about the incident spectrum. Therefore, it may be used as a generalized procedure for the spectral distortion correction of different photon-counting detectors in clinical breast CT systems. PMID:22482608

Ding, Huanjun; Molloi, Sabee

2012-01-01

148

Temporal and spectral behavior of sub-picosecond laser-created X-ray sources from low- to moderate-Z elements  

NASA Astrophysics Data System (ADS)

We report on a set of experiments in which solid targets of different atomic numbers ( Z) were irradiated with laser pulses of time durations ranging from 300 fs to 33 ps, and energies up to 26 J. The time-resolved X-ray emission in the 7.6-8.1 Å spectral range was measured using an ultra-fast X-ray streak camera coupled with a conical Bragg crystal. In this way we were able to follow the dramatic modification of the spectral features as a function of the laser duration. The features evolve from a "ns-type" emission, characterized by narrow and well-defined spectral lines, to very broad spectral features, due not only to the Stark broadening but also to the proliferation of satellites lines. The measured spectra also show strong time dependence, which allows us to follow the time evolution of the hydrodynamic parameters. We then compare the derived parameter with the CHIVAS hydro-radiative simulations. The experimental results are also compared with the AVERROES/TRANSPEC collisional-radiative code, and with precise spectral line shape calculations (PPP and PrismSPECT). The results seem to indicate regimes of interaction where hot electrons play an important role on spectral line formation.

Bastiani-Ceccotti, S.; Renaudin, P.; Dorchies, F.; Harmand, M.; Peyrusse, O.; Audebert, P.; Jacquemot, S.; Calisti, A.; Benredjem, D.

2010-01-01

149

X-ray spectral and timing studies of the high mass x-ray binary pulsar 4u 1907+09  

NASA Astrophysics Data System (ADS)

In this thesis, X-ray spectral and pulse timing analysis of the high mass X-ray binary pulsar 4U 1907+09, based on the observations with Rossi X-ray Timing Explorer (RXTE) and International Gamma-Ray Astrophysics Laboratory (INTEGRAL), are presented. INTEGRAL (October 2005 - November 2007) and RXTE (June 2007 - December 2008) observations confirm that the luminosity of the source is highly variable such that, flaring and dipping activities are observed. The results of time-averaged energy spectra of RXTE and INTEGRAL observations are consistent with the previous studies. Orbital phase resolved spectroscopy with RXTE data, reveals that the Hydrogen column density varies through the orbit reaching to its maximum value just after periastron. This variation approves that the location of the absorbing material is the accretion flow. A slight spectral softening with increasing luminosity is aslo observed. 4U 1907+09 had been steadily spinning down for more than ~15 years with a rate of -3.54x10-14 Hz s-1. RXTE observations of the source in 2001 showed a ~60% decrease in the spin-down rate and INTEGRAL observations in 2003 showed a reversal to spin-up. The timing analysis presented in this thesis reveals a new spindown episode with a rate of -3.59x10-14 Hz s-1, which is close to the previous steady spin-down rate. This result implies that a recent torque reversal before June 2007 has taken place. The reversal is a rare event for 4U 1907+09 and it indicates the variations in the mass accretion rate and/or geometry. Using RXTE observations, 24 new pulse periods are measured to demonstrate the period evolution. Energy resolved pulse profiles confirm that the profile has a double peak sinusoidal shape at energies below 20 keV, whereas the leading peak significantly loses its intensity above 20 keV. This energy dependence indicates that the physical circumstances of the two polar caps are different.

Sahiner, Seyda

150

Chandra X-ray Observations of Jovian Low-latitude Emissions: Morphological, Temporal, and Spectral Characteristics  

NASA Technical Reports Server (NTRS)

Chandra observed X-rays from Jupiter during 24-26 February 2003 for about 40 hours with the ACIS-S and HRC-I instruments. The analysis of Jovian low-latitude "disk" Xray emissions are presented and compared with the high-latitude "auroral" emissions. We report the first Chandra ACIS-S measured X-ray spectrum (0.3-2 keV) of Jupiter's low-latitude disk The disk X-ray emission is harder and extends to higher energies than the auroral spectrum. The temporal variation in the Jovian disk X-rays is on an average consistent with those in the solar X-rays observed by GOES, and TIMED/SSE. Contrary to the auroral X-rays, the disk emissions are uniformly distributed over Jupiter; no indication of longitudinal dependence or correlation with surface magneh field strength is visible. Also, unlike the approx. 40 +/- 20 min periodic oscillations seen in the auroral X-ray emissions, the disk emissions do not show any periodic oscillations. The disk spectrum seems to be consistent with resonant and fluorescent scattering of solar X-rays by the Jovian upper atmosphere. Jupiter's disk is found to be about 50% dimmer in soft X-rays in February 2003 compared that in December 2000, which is consistent with the decrease in solar activity. No evidence of lightning-induced X-rays is seen in the Chandra X-ray data. The Jovian disk spectra observed with Chandra-ACIS is stronger than that observed with XMM-Newton two months later during April 28-29, 2003. The XMM-Newton Xray image of Jupiter shows evidence of limb darkening on the anti-sunward side as seen from Earth, as well as an asymmetry with respect to the subsolar point: suggesting a solar driven process.

Bhardwaj, Anil; Elsner, Ronald F.; Gladstone, G. Randall; Cravens, Thomas E.; Waiate J. Hunter, Jr.; Branduardi-Raymont, Graziella; Ford, Peter

2004-01-01

151

Analysis of X-ray spectral variability and black hole mass determination of the NLS1 galaxy Mrk 766  

NASA Astrophysics Data System (ADS)

We present an XMM-Newton time-resolved spectral analysis of the narrow-line Seyfert 1 galaxy Mrk 766. We analysed eight available observations taken between May 2000 and June 2005 with the EPIC-pn camera in order to investigate the X-ray spectral variability produced by changes in the mass accretion rate. The 0.2 - 10 keV spectra are extracted in time bins longer than 3 ks to have at least 3 × 104 net counts in each bin and then accurately trace the variations of the best-fit parameters of our adopted Comptonization spectral model. We tested a bulk-motion Comptonization (BMC) model which is in general applicable to any physical system powered by accretion onto a compact object, and assumes that soft seed photons are efficiently up-scattered via inverse Compton scattering in a hot and dense electron corona. The Comptonized spectrum has a characteristic power law shape, whose slope was found to increase for large values of the normalization of the seed component, which is proportional to the mass accretion rate ? (in Eddington units). Our baseline spectral model also includes a warm absorber lying on the line of sight and radiation reprocessing from the accretion disc or from outflowing matter in proximity to the central compact object. Our study reveals that the normalization-slope correlation, observed in Galactic black hole sources (GBHs), also holds for Mrk 766: variations of the photon index in the range ? ~ 1.9-2.4 are indeed likely to be related to the variations of ?, as observed in X-ray binary systems. We finally applied a scaling technique based on the observed correlation to estimate the BH mass in Mrk 766. This technique is commonly and successfully applied to measure masses of GBHs, and this is the first time it has been applied in detail to estimate the BH mass in an AGN. We obtained a value of MBH = 1.26-0.77+1.00×106 M?, which is in very good agreement with that estimated by the reverberation mapping. Appendix A is available in electronic form at http://www.aanda.org

Giacchè, S.; Gilli, R.; Titarchuk, L.

2014-02-01

152

Joint Spectral Analysis for Early Bright X-ray Flares of ?-Ray Bursts with Swift BAT and XRT Data  

NASA Astrophysics Data System (ADS)

A joint spectral analysis for early bright X-ray flares that were simultaneously observed with Swift BAT and XRT are present. Both BAT and XRT lightcurves of these flares are correlated. Our joint spectral analysis shows that the radiations in the two energy bands are from the same spectral component, which can be well fitted with a single power-law. Except for the flares in GRBs 060904B and 100906A, the photon spectral indices are <2.0, indicating the peak energies (E p) of the prompt ?-rays should be above the high energy end of the BAT band.

Peng, Fang-Kun; Hu, You-Dong; Wang, Xiang-Gao; Lu, Rui-Jing; Liang, En-Wei

2014-11-01

153

Variable q-range x-ray scattering chamber for chemical and materials science at the Advanced Photon Source  

NASA Astrophysics Data System (ADS)

We present here the design of a novel variable q-range x-ray scattering instrument recently installed at Sector 12 of the Advanced Photon Source. This device provides automated, computer-controlled q-range changes for x-ray scattering experiments by varying the sample-to-detector distance within a large vacuum chamber. Eliminating the need to vent the system when changing camera lengths allows for quick and efficient change-overs between experimental setups. The detector cannot operate in a vacuum environment; therefore it is housed within an air chamber open to atmospheric pressure. A large carbon window isolates the detector from vacuum while allowing high x-ray transmission. An array of motorized beam stops mounted directly upstream of the window protects the detector from the direct x-ray beam for various types of scattering experiments. A smaller detector protrudes into the lower front section for simultaneous wide-angle x-ray scattering data collection. A fully automated support structure aligns the vacuum chamber to the x-ray trajectory.

Schmidt, O.; DeBartolo, J.; Kurtz, C.; Lee, B.; Seifert, S.; Winans, R.; Zuo, X.

2014-03-01

154

CAN WE REPRODUCE THE X-RAY BACKGROUND SPECTRAL SHAPE USING LOCAL ACTIVE GALACTIC NUCLEI?  

SciTech Connect

The X-ray background (XRB) is due to the aggregate of active galactic nuclei (AGNs), which peak in activity at z {approx} 1 and is often modeled as the sum of different proportions of unabsorbed, moderately, and heavily absorbed AGN. We present the summed spectrum of a complete sample of local AGN (the Northern Galactic Cap of the 58 month Swift/BAT catalog, z < 0.2) using 0.4-200 keV data and directly determine the different proportions of unabsorbed, moderately and heavily absorbed AGN that make up the summed spectrum. This stacked low redshift AGN spectrum is remarkably similar in shape to the XRB spectrum (when shifted to z {approx} 1), but the observed proportions of different absorption populations differ from most XRB synthesis models. AGN with Compton-thick absorption account for only {approx}12% of the sample, but produce a significant contribution to the overall spectrum. We confirm that Compton reflection is more prominent in moderately absorbed AGN and that the photon index differs intrinsically between unabsorbed and absorbed AGN. The AGN in our sample account for only {approx}1% of the XRB intensity. The reproduction of the XRB spectral shape suggests that strong evolution in individual AGN properties is not required between z {approx} 0 and 1.

Vasudevan, Ranjan V.; Mushotzky, Richard F. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Gandhi, Poshak, E-mail: ranjan@astro.umd.edu [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

2013-06-20

155

FULL SPECTRAL SURVEY OF ACTIVE GALACTIC NUCLEI IN THE ROSSI X-RAY TIMING EXPLORER ARCHIVE  

SciTech Connect

We have analyzed spectra for all active galactic nuclei (AGNs) in the Rossi X-ray Timing Explorer archive. We present long-term average values of absorption, Fe line equivalent width (EW), Compton reflection, and photon index, and calculate fluxes and luminosities in the 2-10 keV band for 100 AGN with sufficient brightness and overall observation time to yield high-quality spectral results. We compare these parameters across the different classifications of Seyferts and blazars. Our distributions of photon indices for Seyfert 1s and 2s are consistent with the idea that Seyferts share a common central engine; however, our distributions of Compton reflection hump strengths do not support the classical picture of absorption by a torus and reflection off a Compton-thick disk with type depending only on inclination angle. We conclude that a more complex reflecting geometry such as a combined disk and torus or clumpy torus is likely a more accurate picture of the Compton-thick material. We find that Compton reflection is present in {approx}85% of Seyferts and by comparing Fe line EW's to Compton reflection hump strengths we have found that on average 40% of the Fe line arises in Compton thick material; however, this ratio was not consistent from object to object and did not seem to be dependent on optical classification.

Rivers, Elizabeth; Markowitz, Alex; Rothschild, Richard, E-mail: erivers@ucsd.edu [Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424 (United States)

2013-08-01

156

A direct comparison of X-ray spectral models for tori in active galactic nuclei  

E-print Network

Several X-ray spectral models for tori in active galactic nuclei (AGNs) are available to constrain the properties of tori; however, the accuracy of these models has not been verified. We recently construct a code for the torus using Geant4, which can easily handle different geometries (Liu & Li 2014). Thus, we adopt the same assumptions as Murphy & Yaqoob (2009, hereafter MY09) and Brightman & Nandra (2011, hereafter BN11) and try to reproduce their spectra. As a result, we can reproduce well the reflection spectra and the strength of the Fe K$\\alpha$ line of MY09, for both $\\NH=10^{24}$ and $10^{25}$ cm$^{-2}$. However, we cannot produce the strong reflection component of BN11 in the low-energy band. The origin of this component is the reflection from the visible inner wall of the torus, and it should be very weak in the edge-on directions under the geometry of BN11. Therefore, the behaviour of the reflection spectra in BN11 is not consistent with their geometry. The strength of the Fe K$\\alpha$ ...

Liu, Yuan

2015-01-01

157

ON THE NATURE OF THE mHz X-RAY QUASI-PERIODIC OSCILLATIONS FROM ULTRALUMINOUS X-RAY SOURCE M82 X-1: SEARCH FOR TIMING-SPECTRAL CORRELATIONS  

SciTech Connect

Using all the archival XMM-Newton X-ray (3-10 keV) observations of the ultraluminous X-ray source (ULX) M82 X-1, we searched for a correlation between its variable mHz quasi-periodic oscillation (QPO) frequency and its hardness ratio (5-10 keV/3-5 keV), an indicator of the energy spectral power-law index. When stellar-mass black holes (StMBHs) exhibit type-C low-frequency QPOs ({approx}0.2-15 Hz), the centroid frequency of the QPO is known to correlate with the energy spectral index. The detection of such a correlation would strengthen the identification of M82 X-1's mHz QPOs as type-C and enable a more reliable mass estimate by scaling its QPO frequencies to those of type-C QPOs in StMBHs of known mass. We resolved the count rates and the hardness ratios of M82 X-1 and a nearby bright ULX (source 5/X42.3+59) through surface brightness modeling. We detected QPOs in the frequency range of 36-210 mHz during which M82 X-1's hardness ratio varied from 0.42 to 0.47. Our primary results are (1) that we do not detect any correlation between the mHz QPO frequency and the hardness ratio (a substitute for the energy spectral power-law index) and (2) similar to some accreting X-ray binaries, we find that M82 X-1's mHz QPO frequency increases with its X-ray count rate (Pearson's correlation coefficient = +0.97). The apparent lack of a correlation between the QPO centroid frequency and the hardness ratio poses a challenge to the earlier claims that the mHz QPOs of M82 X-1 are the analogs of the type-C low-frequency QPOs of StMBHs. On the other hand, it is possible that the observed relation between the hardness ratio and the QPO frequency represents the saturated portion of the correlation seen in type-C QPOs of StMBHs-in which case M82 X-1's mHz QPOs can still be analogous to type-C QPOs.

Pasham, Dheeraj R. [Astronomy Department, University of Maryland, College Park, MD 20742 (United States); Strohmayer, Tod E., E-mail: dheeraj@astro.umd.edu, E-mail: tod.strohmayer@nasa.gov [Astrophysics Science Division, NASA's Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2013-07-10

158

On the Nature of the mHz X-ray Quasi-Periodic Oscillations from Ultraluminous X-ray source M82 X-1: Search for Timing-Spectral Correlations  

NASA Technical Reports Server (NTRS)

Using all the archival XMM-Newton X-ray (3-10 keV) observations of the ultraluminous X-ray source (ULX) M82 X-1, we searched for a correlation between its variable mHz quasi-periodic oscillation (QPO) frequency and its hardness ratio (5-10 keV/3-5 keV), an indicator of the energy spectral power-law index. When stellar-mass black holes (StMBHs) exhibit type-C low-frequency QPOs (0.2-15 Hz), the centroid frequency of the QPO is known to correlate with the energy spectral index. The detection of such a correlation would strengthen the identification of M82 X-1's mHz QPOs as type-C and enable a more reliable mass estimate by scaling its QPO frequencies to those of type-C QPOs in StMBHs of known mass.We resolved the count rates and the hardness ratios of M82 X-1 and a nearby bright ULX (source 5/X42.3+59) through surface brightness modeling.We detected QPOs in the frequency range of 36-210 mHz during which M82 X-1's hardness ratio varied from 0.42 to 0.47. Our primary results are (1) that we do not detect any correlation between the mHz QPO frequency and the hardness ratio (a substitute for the energy spectral power-law index) and (2) similar to some accreting X-ray binaries, we find that M82 X-1's mHz QPO frequency increases with its X-ray count rate (Pearson's correlation coefficient = +0.97). The apparent lack of a correlation between the QPO centroid frequency and the hardness ratio poses a challenge to the earlier claims that the mHz QPOs of M82 X-1 are the analogs of the type-C low-frequency QPOs of StMBHs. On the other hand, it is possible that the observed relation between the hardness ratio and the QPO frequency represents the saturated portion of the correlation seen in type-C QPOs of StMBHs-in which case M82 X-1's mHz QPOs can still be analogous to type-C QPOs.

Pasham, Dheeraj R.; Strohmayer, Tod E.

2013-01-01

159

A Fully Bayesian Method for Jointly Fitting Instrumental Calibration and X-Ray Spectral Models  

NASA Astrophysics Data System (ADS)

Owing to a lack of robust principled methods, systematic instrumental uncertainties have generally been ignored in astrophysical data analysis despite wide recognition of the importance of including them. Ignoring calibration uncertainty can cause bias in the estimation of source model parameters and can lead to underestimation of the variance of these estimates. We previously introduced a pragmatic Bayesian method to address this problem. The method is "pragmatic" in that it introduced an ad hoc technique that simplified computation by neglecting the potential information in the data for narrowing the uncertainty for the calibration product. Following that work, we use a principal component analysis to efficiently represent the uncertainty of the effective area of an X-ray (or ?-ray) telescope. Here, however, we leverage this representation to enable a principled, fully Bayesian method that coherently accounts for the calibration uncertainty in high-energy spectral analysis. In this setting, the method is compared with standard analysis techniques and the pragmatic Bayesian method. The advantage of the fully Bayesian method is that it allows the data to provide information not only for estimation of the source parameters but also for the calibration product—here the effective area, conditional on the adopted spectral model. In this way, it can yield more accurate and efficient estimates of the source parameters along with valid estimates of their uncertainty. Provided that the source spectrum can be accurately described by a parameterized model, this method allows rigorous inference about the effective area by quantifying which possible curves are most consistent with the data.

Xu, Jin; van Dyk, David A.; Kashyap, Vinay L.; Siemiginowska, Aneta; Connors, Alanna; Drake, Jeremy; Meng, Xiao-Li; Ratzlaff, Pete; Yu, Yaming

2014-10-01

160

The Hard X-ray Spectral Evolution in XRBs, AGNs and ULXs  

E-print Network

We explore the relationship between the hard X-ray photon index $\\Gamma$ and the Eddington ratio (\\xi=L_{X}(0.5-25 keV)/L_{Edd}) in six XRBs. We find that different XRBs follow different anti-correlations between $\\Gamma$ and $\\xi$ when $\\xi$ is less than a critical value, while they follow the same positive correlation when $\\xi$ is larger than the critical value. This anti-correlation and positive correlation are also found in LLAGNs and QSOs respectively, and the anti-correlation and positive correlation of different XRBs roughly converge to the same point ($\\log \\xi=-2.1, \\Gamma=1.5$), which may correspond to the accretion mode transition, since that the anti-correlation and positive correlation are consistent with the prediction of ADAFs and standard disk/corona system respectively. The traditional low/hard state are divided into two parts by the cross point $\\log \\xi\\sim-2.1$, i.e., faint-hard state in the anti-correlation part and bright-hard state in the positive correlation part. The accretion process in the bright-hard state may be still the standard accretion disk as that in the high/soft state, which is consistent with that both the cold disk component and broad Fe K emission line are observed in some bright-hard state of XRBs. The ADAF is only important in the faint-hard state XRBs. Motivated by the similarities of the state transition and timing properties of the ULXs to that of XRBs, we then constrain the BH masses for seven luminous ULXs assuming that their X-ray spectral evolution is similar to that of XRBs. We find that the BH masses of these seven ULXs are around $10^{4}M_sun$, which are typical intermediate mass BHs (IMBHs). Our results are roughly consistent with the BH masses constrained from the model fitting with a multi-color disk and/or the timing properties(e.g., QPO and break frequency).

Qingwen Wu; Minfeng Gu

2008-12-17

161

Reabsorption of Soft X-Ray Emission at High X-Ray Free-Electron Laser Fluences  

NASA Astrophysics Data System (ADS)

We report on oxygen K-edge soft x-ray emission spectroscopy from a liquid water jet at the Linac Coherent Light Source. We observe significant changes in the spectral content when tuning over a wide range of incident x-ray fluences. In addition the total emission yield decreases at high fluences. These modifications result from reabsorption of x-ray emission by valence-excited molecules generated by the Auger cascade. Our observations have major implications for future x-ray emission studies at intense x-ray sources. We highlight the importance of the x-ray pulse length with respect to the core-hole lifetime.

Schreck, Simon; Beye, Martin; Sellberg, Jonas A.; McQueen, Trevor; Laksmono, Hartawan; Kennedy, Brian; Eckert, Sebastian; Schlesinger, Daniel; Nordlund, Dennis; Ogasawara, Hirohito; Sierra, Raymond G.; Segtnan, Vegard H.; Kubicek, Katharina; Schlotter, William F.; Dakovski, Georgi L.; Moeller, Stefan P.; Bergmann, Uwe; Techert, Simone; Pettersson, Lars G. M.; Wernet, Philippe; Bogan, Michael J.; Harada, Yoshihisa; Nilsson, Anders; Föhlisch, Alexander

2014-10-01

162

Saturation and Dynamic Range of Microchannel Plate-Based X-Ray Imagers  

SciTech Connect

This paper describes recent advances in Monte Carlo simulations of microchannel plate (MCP)–based x-ray detectors, a continuation of ongoing work in this area. A Monte Carlo simulation model has been developed over the past several years by National Security Technologies, LLC (NSTec). The model simulates the secondary electron emission process in an MCP pore and includes the effects of gain saturation. In this work we focus on MCP gain saturation and dynamic range. We have performed modeling and experimental characterizations of L/D = 46, 10-micron diameter, MCP-based detectors. The detectors are typically operated by applying a subnanosecond voltage pulse, which gates the detector on. Agreement between the simulations and experiment is very good for a variety of voltage pulse waveforms ranging in width from 150 to 300 ps. The results indicate that such an MCP begins to show nonlinear gain around 5 × 10^4 electrons per pore and hard saturation around 105 electrons per pore. The simulations show a difference in MCP sensitivity vs voltage for high flux of photons producing large numbers of photoelectrons on a subpicosecond timescale. Simulations and experiments both indicate an MCP dynamic range of 1 to 10,000, and the dynamic range depends on how the voltage is applied.

,

2012-05-04

163

Sensitivity study of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum  

NASA Astrophysics Data System (ADS)

The paper investigates theoretically the sensitivities of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum. In the simulation, the hohlraum radiation is represented by a Planckian spectrum for the main drive plus a gaussian bump centered at energy Ec for preheating x-rays. Simulation results show that with the increasing of center energy Ec, the Atwood number at the fuel-ablator interface increases rapidly due to the preheating and expanding of the inner undoped CH layer. The growing of Atwood number indicates the hydrodynamic instability (HI) growth and mixing at this interface. On the other hand, the increasing of Ec results in a large density gradient scale length of ablation front and stabilizes the HI growth at ablation front. The changes of the hard x-ray spectrum have significant influences on other important implosion parameters including the ablator mass remaining, shock timing, implosion velocity, and yield as well. High-precision results on the hard x-ray spectral distribution of hohlraum are thus critical for optimizing the ignition capsule design to limit the HI growth.

Gu, Jianfa; Zou, Shiyang; Li, Yongsheng; Dai, Zhensheng; Ye, Wenhua

2012-12-01

164

Sensitivity study of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum  

SciTech Connect

The paper investigates theoretically the sensitivities of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum. In the simulation, the hohlraum radiation is represented by a Planckian spectrum for the main drive plus a gaussian bump centered at energy E{sub c} for preheating x-rays. Simulation results show that with the increasing of center energy E{sub c}, the Atwood number at the fuel-ablator interface increases rapidly due to the preheating and expanding of the inner undoped CH layer. The growing of Atwood number indicates the hydrodynamic instability (HI) growth and mixing at this interface. On the other hand, the increasing of E{sub c} results in a large density gradient scale length of ablation front and stabilizes the HI growth at ablation front. The changes of the hard x-ray spectrum have significant influences on other important implosion parameters including the ablator mass remaining, shock timing, implosion velocity, and yield as well. High-precision results on the hard x-ray spectral distribution of hohlraum are thus critical for optimizing the ignition capsule design to limit the HI growth.

Gu Jianfa; Zou Shiyang; Li Yongsheng; Dai Zhensheng; Ye Wenhua [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

2012-12-15

165

Spectral Modeling of the Comptonized Continua of Accreting X-Ray Pulsars  

NASA Astrophysics Data System (ADS)

We are undertaking a program to analyze the X-ray spectra of the accretion flows onto strongly magnetic neutron stars in high mass binary systems such as Cen X-3, and XTE J1946+274. These accreting pulsars typically have X-ray spectra consisting of broad Comptonized cutoff power-laws. Current theory suggests these X-ray spectra result from radiation-dominated shocks that develop in the high-velocity magnetically channeled plasma accretion flows onto the surfaces of the neutron stars. These X-ray pulsars often, but not always, show cyclotron resonant scattering features implying neutron star surface magnetic field strengths above 1012 G. Proper fitting of cyclotron line centroids (for example, to investigate how the line centroid varies with X-ray luminosity) requires a robust model for the Comptonized X-ray continuum upon which the cyclotron lines are superposed, and this can be provided by a continuum model based on the physics of the accretion column.We discuss in this presentation our ongoing program for the analysis of the X-ray spectra formed in these systems. Our program consists of two parts. First, we are modeling the X-ray spectra from the Suzaku X-ray satellite of accreting X-ray pulsars Cen X-3 and XTE J1946+274 utilizing the best currently existing empirical models. The second part of our program is building a new analysis tool based on the analytical model of Becker and Wolff (2007). In the high temperature optically thick plasma flows, the processes of bremsstrahlung emission from the hot plasma, black body emission from a thermal mound near the neutron star surface, and cyclotron emission from electrons in the first Landau excited state, all contribute to the total observed X-ray spectrum. We show recent results from our new implementation and its comparison with the Suzaku data for these X-ray pulsars.This research is supported by the NASA Astrophysics Data Analysis Program.

Wolff, Michael Thomas; Pottschmidt, Katja; Becker, Peter A.; Marcu, Diana; Wilms, Jörn; Wood, Kent S.

2015-01-01

166

The dependence of the soft X ray spectral slope with radio property, luminosity, and redshift, for a large sample of AGN from the Einstein IPC data base  

NASA Technical Reports Server (NTRS)

The dependence of the soft X-ray spectral slope on radio, optical and X-ray properties, and on redshift are reported for a large sample of Active Galactic Nuclei (AGN). The sample includes 317 optically and radio-selected AGN from a preliminary version of the Einstein Imaging Proportional Counter (IPC) quasar and AGN data base. The main results are: the difference in X-ray slope between radio-loud and radio-quiet AGN were confirmed for an independent and much larger sample of sources; a difference in X-ray slope between flat and steep radio spectrum AGN is observed only in high luminosity sub-sample; in flat radio spectrum AGNs there is an indication for a dependence of the X-ray spectral index on X-ray luminosity redshift and alpha sub 0x.

Brunner, H.; Worrall, D. M.; Wilkes, Belinda J.; Elvis, Martin

1989-01-01

167

Spektr: A computational tool for x-ray spectral analysis and imaging system optimization  

SciTech Connect

A set of computational tools are presented that allow convenient calculation of x-ray spectra, selection of elemental and compound filters, and calculation of beam quality characteristics, such as half-value layer, mR/mAs, and fluence per unit exposure. The TASMIP model of Boone and Seibert is adapted to a library of high-level language (Matlab{sup TM}) functions and shown to agree with experimental measurements across a wide range of kVp and beam filtration. Modeling of beam filtration is facilitated by a convenient, extensible database of mass and mass-energy attenuation coefficients compiled from the National Institute of Standards and Technology. The functions and database were integrated in a graphical user interface and made available online at http://www.aip.org/epaps/epaps.html. The functionality of the toolset and potential for investigation of imaging system optimization was illustrated in theoretical calculations of imaging performance across a broad range of kVp, filter material type, and filter thickness for direct and indirect-detection flat-panel imagers. The calculations reveal a number of nontrivial effects in the energy response of such detectors that may not have been guessed from simple K-edge filter techniques, and point to a variety of compelling hypotheses regarding choice of beam filtration that warrant future investigation.

Siewerdsen, J.H.; Waese, A.M.; Moseley, D.J.; Richard, S.; Jaffray, D.A. [Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario M5G 2M9 (Canada); Departments of Medical Biophysics and Radiation Oncology, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario M5G 2M9 (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario M5G 2M9 (Canada); Departments of Medical Biophysics and Radiation Oncology, University of Toronto, Toronto, Ontario M5G 2M9 (Canada); Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario M5G 2M9 (Canada)

2004-11-01

168

The X-ray spectral evolution of Cygnus X-2 in the framework of bulk Comptonization  

NASA Astrophysics Data System (ADS)

Context: Strong theoretical and observational support exists that the spectral evolution of neutron-star LMXBs, including transient hard X-ray tails, can be explained by the interplay between thermal and bulk motion Comptonization. The introduction of a new XSPEC Comptonization model, Comptb, including thermal and bulk Comptonization, has provided additional support to this interpretation. Aims: We used Comptb to investigate the spectral evolution of the neutron-star LMXB Cyg X-2 along its Z track. We selected a single source to trace in a quantitative way the evolution of the physical parameters of the model. Methods: We analyzed archival broad-band BeppoSAX spectra of Cyg X-2. Five broad-band spectra were newly extracted by using information about the source position in the Z track described in the colour-colour and colour-intensity diagrams. Results: We fitted the spectra of the source with two Comptb components. The first one, with a bulk parameter ? = 0, represents the dominant component of the overall source broad-band spectrum and its origin is related to thermal upscattering (Comptonization) of cold seed photons by warm electrons in a high opacity enviroment. We attribute the origin of these seed photons to the section of the disk that illuminates the outer coronal region (transition layer) located between the accretion disk itself and the neutron-star surface. The physical properties of this thermal component are roughly constant with both time and inferred mass accretion rate. The second Comptb model describes the overall Comptonization (thermal plus bulk, ? > 0) of hotter seed photons that originate in both the inner transition layer and at the neutron-star surface. This component is more significant in the horizontal branch of the colour-colour or hardness-intensity diagram and progressively disappears towards the normal branch, where a pure blackbody spectrum is observed. Conclusions: The spectral evolution of Cyg X-2 is studied and interpreted in terms of changes in the innermost environmental conditions of the system, leading to a variable thermal-bulk Comptonization efficiency.

Farinelli, R.; Paizis, A.; Landi, R.; Titarchuk, L.

2009-05-01

169

Spectral properties of X-ray bright variable sources in the Taurus molecular cloud  

Microsoft Academic Search

Aims:We analyze 19 bright variable X-ray sources detected in the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST), to characterize the variations with time of their coronal properties and to derive information on the X-ray emitting structures. Methods: We performed time-resolved spectroscopy of the EPIC PN and MOS spectra of the XEST sources, using a model with one or

E. Franciosini; I. Pillitteri; B. Stelzer; G. Micela; K. R. Briggs; L. Scelsi; A. Telleschi; M. Audard; F. Palla; M. Güdel

2007-01-01

170

Monitoring Long-Range Electron Transfer Pathways in Proteins by Stimulated Attosecond Broadband X-ray Raman Spectroscopy.  

PubMed

Long-range electron transfer (ET) is a crucial step in many energy conversion processes and biological redox reactions in living organisms. We show that newly developed X-ray pulses can directly probe the evolving oxidation states and the electronic structure around selected atoms with detail not available through conventional time-resolved infrared or optical techniques. This is demonstrated in a simulation study of the stimulated X-ray Raman (SXRS) signals in Re-modified azurin, which serves as a benchmark system for photoinduced ET in proteins. Nonlinear SXRS signals offer a direct novel window into the long-range ET mechanism. PMID:25400875

Zhang, Yu; Biggs, Jason D; Govind, Niranjan; Mukamel, Shaul

2014-11-01

171

Spectral variability in early-type binary X-ray systems  

NASA Technical Reports Server (NTRS)

Theoretical models for the ionization of trace elements in a strong stellar wind by a compact binary X-ray source and for the resulting orbital phase dependence of the emergent soft X-ray spectra and the profiles of ultraviolet resonance lines are presented. Model results agree qualitatively with the X-ray and ultraviolet spectra of the system 4U 0900-40/HD 77581 and explain the suppression of the absorption profiles of the Si IV upsilon 1394 and C IV upsilon 1548 lines when the X-ray sources is in front of the star. The model predicts that the absorption profiles of the N V upsilon 1239 and O VI upsilon 1032 lines will be enhanced rather than suppressed during this orbital phase. We predict phase-dependent linear polarization in the resonance lines profiles. Future observations of these phase dependent effects in early-type binary X-ray systems may be used to investigate the dynamics of stellar winds and their interactions with the X-ray source.

Mccray, R.; Kallman, T. R.; Castor, J. I.; Olson, G. L.

1984-01-01

172

Spectral variability in early-type binary X-ray systems  

NASA Technical Reports Server (NTRS)

Theoretical models for the ionization of trace elements in a strong stellar wind by a compact binary X-ray source and for the resulting orbital phase dependence of the emergent soft X-ray spectra and the profiles of ultraviolet resonance lines are presented. Model results agree qualitatively with the X-ray and ultraviolet spectra of the system 4U 0900-40/HD 77581 and explain the suppression of the absorption profiles of the Si IV upsilon 1394 and C IV upsilon 1548 lines when the X-ray sources are in front of the star. The model predicts that the absorption profiles of the N V upsilon 1239 and O VI upsilon 1032 lines will be enhanced rather than suppresed during this orbital phase.Phase-dependent linear polarization in the resonance lines profiles is predicted. Future observations of these phase dependent effects in early-type binary X-ray systems may be used to investigate the dynamics of stellar winds and their interactions with the X-ray source.

Kallman, T. R.; Castor, J. I.; Olson, G. L.; Mccray, R.

1984-01-01

173

Streaked, x-ray-transmission-grating spectrometer  

SciTech Connect

A free standing x-ray transmission grating has been coupled with a soft x-ray streak camera to produce a time resolved x-ray spectrometer. The instrument has a temporal resolution of approx. 20 psec, is capable of covering a broad spectral range, 2 to 120 A, has high sensitivity, and is simple to use requiring no complex alignment procedure. In recent laser fusion experiments the spectrometer successfully recorded time resolved spectra over the range 10 to 120 A with a spectral resolving power, lambda/..delta..lambda of 4 to 50, limited primarily by source size and collimation effects.

Ceglio, N.M.; Roth, M.; Hawryluk, A.M.

1981-08-01

174

Black Hole X-ray Binary LMC X--1 and LMC X--3: Observations Confront Spectral Models  

NASA Astrophysics Data System (ADS)

We present a comprehensive spectral analysis of black hole X-ray binaries, LMC X--1 and LMC X--3, based on BeppoSAX observations. We test both the commonly-used multi-color disk plus power law (MCD+PL) model and a newly-developed Monte-Carlo simulation-based Comptonized multi-color disk (CMCD) model, by comparing the inferred parameters with independent measurements. While both model give an adequate description of the spectra, we find a significant discrepancy between the MCD+PL inferred X-ray-absorbing gas column density and the absorption-edge measurement based on dispersed X-ray spectra. The MCD+PL fits to the LMC X-1 spectra also require a change in the inner disk radius during the BeppoSAX observation, which may be due to the nonphysical effects inherited in the model. No similar problem is found for the CMCD model. The inferred black hole masses, ˜ 6.8(6.5-7.8) solar mass for LMC X--1 and ˜ 7.2(7.1 - 7.3) solar mass for LMC X--3 (90% confidence limits), and the disk inclination angles, <= 43 degree and <= 69 degree, are all consistent with the optical measurements. The obtained X-ray-absorbing column density, 0.45(0.42 - 0.47) x 1021 cm-2 for LMC X--3, is statistically consistent with the value derived from the X-ray-absorption edge measurement. The spectral state evolution of LMC X--1 within the BeppoSAX observation can naturally be explained by a change in the accretion rate, which leads to an increase in both the inner disk temperature and the Comptonization opacity.

Yao, Y.; Wang, Q. D.; Zhang, S. N.

2004-08-01

175

Diagnosing Direct-Drive, Shock-Heated, and Compressed Plastic Planar Foils with Noncollective Spectrally Resolved X-Ray Scattering  

SciTech Connect

The electron temperature (Te) and average ionization (Z) of nearly Fermi-degenerate, direct-drive, shock-heated, and compressed plastic planar foils were investigated using noncollective spectrally resolved x-ray scattering on the OMEGA Laser System. Plastic (CH) and Br-doped CH foils were driven with six beams, having an overlapped intensity of ~1 × 10^14 W/cm^2 and generating ~15-Mbar pressure in the foil.

Sawada, H.; Regan, S.P.; Meyerhofer, D.D.; Igumenshchev, I.V.; Goncharov, V.N.; Boehly, T.R.; Epstein, R.; Sangster, T.C.; Smalyuk, V.A.; Yaakobi, B.; Gregori, G.; Glenzer, S.H.; Landen, O.L.

2007-12-14

176

Diagnosing direct-drive, shock-heated, and compressed plastic planar foils with noncollective spectrally resolved x-ray scattering  

Microsoft Academic Search

The electron temperature (Te) and average ionization (Z) of nearly Fermi-degenerate, direct-drive, shock-heated, and compressed plastic planar foils were investigated using noncollective spectrally resolved x-ray scattering on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Plastic (CH) and Br-doped CH foils were driven with six beams, having an overlapped intensity of ~1×1014 W\\/cm2 and

H. Sawada; S. P. Regan; D. D. Meyerhofer; I. V. Igumenshchev; V. N. Goncharov; T. R. Boehly; R. Epstein; T. C. Sangster; V. A. Smalyuk; B. Yaakobi; G. Gregori; S. H. Glenzer; O. L. Landen

2007-01-01

177

Spectral analysis of paramagnetic centers induced in human tooth enamel by x-rays and gamma radiation  

NASA Astrophysics Data System (ADS)

Based on study of spectral and relaxation characteristics, we have established that paramagnetic centers induced in tooth enamel by x-rays and gamma radiation are identical in nature. We show that for the same exposure dose, the intensity of the electron paramagnetic resonance (EPR) signal induced by x-radiation with effective energy 34 keV is about an order of magnitude higher than the amplitude of the signal induced by gamma radiation. We have identified a three-fold attenuation of the EPR signal along the path of the x-radiation from the buccal to the lingual side of a tooth, which is evidence that the individual had undergone diagnostic x-ray examination of the dentition or skull. We have shown that the x-ray exposure doses reconstructed from the EPR spectra are an order of magnitude higher than the applied doses, while the dose loads due to gamma radiation are equal to the applied doses. The data obtained indicate that for adequate reconstruction of individual absorbed doses from EPR spectra of tooth enamel in the population subjected to the combined effect of x-radiation and accidental external gamma radiation as a result of the disaster at the Chernobyl nuclear power plant, we need to take into account the contribution to the dose load from diagnostic x-rays in examination of the teeth, jaw, or skull.

Kirillov, V. A.; Kuchuro, I. I.

2010-03-01

178

Efficiency calibrations of cylindrically bent transmission crystals in the 20 to 80 keV x-ray energy range.  

PubMed

Two quartz (10-11) crystals were cylindrically bent to a 25.4 cm radius of curvature and were mounted in identical Cauchois-type transmission spectrometers, and the crystal diffraction efficiencies were measured to 5% absolute accuracy using narrow bandwidth x-ray source fluences in the 20 to 80 keV energy range. The measured integrated reflectivity values were compared to calculations performed using a computational model that accounts for the diffraction geometry of the bent transmission crystal. These crystal calibrations enable the accurate measurement of absolute hard x-ray emission levels from laser-produced plasmas and other laboratory sources. PMID:21499348

Szabo, Csilla I; Feldman, Uri; Seltzer, Stephen; Hudson, Lawrence T; O'Brien, Michelle; Park, Hye-Sook; Seely, John F

2011-04-15

179

The X-ray surface brightness distribution and spectral properties of six early-type galaxies  

NASA Technical Reports Server (NTRS)

Detailed analysis is presented of the Einstein X-ray observations of six early-type galaxies. The results show that effective cooling is probably present in these systems, at least in the innermost regions. Interaction with the surrounding medium has a major effect on the X-ray surface brightness distribution at large radii, at least for galaxies in clusters. The data do not warrant the general assumptions of isothermality and gravitational hydrostatic equilibrium at large radii. Comparison of the X-ray surface brightness profiles with model predictions indicate that 1/r-squared halos with masses of the order of 10 times the stellar masses are required to match the data. The physical model of White and Chevalier (1984) for steady cooling flows in a King law potential with no heavy halo gives a surface brightness distribution that resembles the data if supernovae heating is present.

Trinchieri, G.; Fabbiano, G.; Canizares, C. R.

1986-01-01

180

Soft x-ray free-electron laser imaging by LiF crystal and film detectors over a wide range of fluences.  

PubMed

LiF crystal and film detectors were used to measure the far-field fluence profile of a self-amplified spontaneous-emission free-electron laser beam and diffraction imaging with high spatial resolution. In these measurements the photoluminescence (PL) response of LiF crystal and film was compared over a wide range of soft x-ray fluences. It was found that the soft x-ray fluence dependences of LiF crystal and film differ. At low fluence, the LiF crystal shows higher PL response compared to LiF film, while this comparison is the opposite at higher fluence. Accurate measurement of LiF crystal and film PL response is important for precise characterization of the spatial, spectral, and coherence features of x-ray beams across the full profile and in localized areas. For such measurements, crucial LiF detector attributes are high spatial resolution and high dynamic range. PMID:23338201

Pikuz, Tatiana A; Faenov, Anatoly Ya; Fukuda, Yuji; Kando, Masaki; Bolton, Paul; Mitrofanov, Alexander; Vinogradov, Alexander V; Nagasono, Mitsuru; Ohashi, Haruhiko; Yabashi, Makina; Tono, Kensuke; Senba, Yasunori; Togashi, Tadashi; Ishikawa, Tetsuya

2013-01-20

181

Spectral variability in hard X-rays and discovery of a 13,5 years period in bright quasar 3C273  

NASA Astrophysics Data System (ADS)

SPECTRAL VARIABILITY IN HARD X-RAYS AND DISCOVERY OF A 13.5 YEARS PERIOD IN BRIGHT QUASAR 3C273. R. K. Manchanda Tata Institute of Fundamental Research, Colaba, Mumbai-400005, India. ravi@tifr.res.in/Fax:+91-22-2152110 Among the large variety of active galactic nuclei, 3C 273 is the nearest quasi stellar object. The source has been studied in details in various energy bands and shows a large variety of morphological features. In the X-ray energy range 2-20 keV, the spectrum follows a power law with a spectral index of -1.5, however, the observed value of the spectral index in the 20-120 keV band shows a large variation. In the case of old archival data, the derived spectral index has a value between 1.5 and 2.2 while, the recent data from OSSE experiment showed a flat spectrum with index 0.8. Thus, to fit the GeV fluxes from the source, a break in the spectrum around 1 MeV has been proposed. In this paper we report the balloon-borne hard X-ray observations of 3C273 made with LASE instrument on Nov. 20, 1998 as a part of our continuing programme of balloon borne hard X-ray observations in the 20-200 keV band using high sensitivity Large Area Scintillation counter Experiment. Our data clearly show a steep spectrum in the 20-200 keV with spectral index a = -2.26+ 0.07 and its extrapolation can fit the GeV data. The presence of steep power law index is in complete contrast to earlier observation from OSSE. From a comparison with the available archival data of the source we have discovered that 50 keV flux from the source, shows very strong modulation with a period of about 13.5 years and which is also present at 100 keV and in the spectral index to a lesser degree. We discuss the periodicity in terms of precessing source geometry.

Manchanda, R.

182

An Outburst Scenario for the X-ray Spectral Variability in 3C 111  

NASA Technical Reports Server (NTRS)

We present a combined Suzaku and Swift BAT broad-band E=0.6-200 keV spectral analysis of three 3C 111 observations obtained in 2010. The data are well described with an absorbed power-law continuum and a weak (R approximately equal to 0.2) cold reflection component from distant material. We constrain the continuum cutoff at E(sub C) approximately equal to 150- 200 keV, which is in accordance with X-ray Comptonization corona models and supports claims that the jet emission is only dominant at much higher energies. Fe XXVI Ly alpha emission and absorption lines are also present in the first and second observations, respectively. The modelling and interpretation of the emission line is complex and we explore three possibilities. If originating from ionized disc reflection, this should be emitted at r(sub in) greater than or equal to 50 r(sub g) or, in the lamp-post configuration, the illuminating source should be at a height of h greater than or equal to 30 r(sub g) over the black hole. Alternatively, the line could be modeled with a hot collisionally ionized plasma with temperature kT = 22.0(sup +6.1)(sub -3.2) keV or a photo-ionized plasma with logXi=4.52(sup +0.10)(sub -0.16) erg per second cm, and column density N(sub H) greater than 3×10(sup 23) per square centimeter. However, the first and second scenarios are less favored on statistical and physical grounds, respectively. The blue-shifted absorption line in the second observation can be modelled as an ultra-fast outflow (UFO) with ionization parameter logXi=4.47(sup +0.76) (sub -0.04) erg per second cm, column density NH=(5.3(sup +1.8)(sub -1.3))×10(sup 22) per square centimeter and outflow velocity v(sub out) = 0.104+/-0.006c. Interestingly, the parameters of the photoionized emission model remarkably match those of the absorbing UFO, supporting the possibility that the same material could be responsible for both emission and absorption. We suggest an outburst scenario in which an accretion disc wind, initially lying out of the line of sight and observed in emission, then crosses our view to the source and it is observed in absorption as a mildly-relativistic UFO.

Tombesi, Francesco; Reeves, J. N.; Reynolds, Christopher S.; Garcia, J.; Lohfink, A.

2013-01-01

183

An outburst scenario for the X-ray spectral variability in 3C 111  

NASA Astrophysics Data System (ADS)

We present a combined Suzaku and Swift BAT broad-band E = 0.6-200 keV spectral analysis of three 3C 111 observations obtained in 2010. The data are well described with an absorbed power-law continuum and a weak (R ? 0.2) cold reflection component from distant material. We constrain the continuum cutoff at EC ? 150-200 keV, which is in accordance with X-ray Comptonization corona models and supports claims that the jet emission is only dominant at much higher energies. Fe XXVI Ly? emission and absorption lines are also present in the first and second observations, respectively. The modelling and interpretation of the emission line is complex and we explore three possibilities. If originating from ionized-disc reflection, this should be emitted at rin ? 50 rg or, in the lamp-post configuration, the illuminating source should be at a height of h ? 30 rg above the black hole. Alternatively, the line could be modelled with a hot collisionally ionized plasma with temperature kT = 22.0^{+6.1}_{-3.2} keV or a photoionized plasma with log ? = 4.52^{+0.10}_{-0.16} erg s-1 cm and column density NH > 3 × 1023 cm-2. However, the first and second scenarios are less favoured on statistical and physical grounds, respectively. The blueshifted absorption line in the second observation can be modelled as an ultrafast outflow (UFO) with ionization parameter log ? = 4.47^{+0.76}_{-0.04} erg s-1 cm, column density N_H = (5.3^{+1.8}_{-1.3})× 10^{22} cm-2 and outflow velocity vout = 0.104 ± 0.006c. Interestingly, the parameters of the photoionized emission model remarkably match those of the absorbing UFO, supporting the possibility that the same material could be responsible for both emission and absorption. We suggest an outburst scenario in which an accretion disc wind, initially lying out of the line of sight and observed in emission, then crosses our view to the source and it is observed in absorption as a mildly relativistic UFO.

Tombesi, F.; Reeves, J. N.; Reynolds, C. S.; García, J.; Lohfink, A.

2013-09-01

184

Spectral Resolution for Five-Element, Filtered, X-Ray Detector (XRD) Arrays Using the Methods of Backus and Gilbert  

SciTech Connect

The generalized method of Backus and Gilbert (BG) is described and applied to the inverse problem of obtaining spectra from a 5-channel, filtered array of x-ray detectors (XRD's). This diagnostic is routinely fielded on the Z facility at Sandia National Laboratories to study soft x-ray photons ({le}2300 eV), emitted by high density Z-pinch plasmas. The BG method defines spectral resolution limits on the system of response functions that are in good agreement with the unfold method currently in use. The resolution so defined is independent of the source spectrum. For noise-free, simulated data the BG approximating function is also in reasonable agreement with the source spectrum (150 eV black-body) and the unfold. This function may be used as an initial trial function for iterative methods or a regularization model.

FEHL,DAVID LEE; BIGGS,F.; CHANDLER,GORDON A.; STYGAR,WILLIAM A.

2000-01-17

185

Integration of the Two-Dimensional Power Spectral Density into Specifications for the X-ray Domain -- Problems and Opportunities  

SciTech Connect

An implementation of the two-dimensional statistical scattering theory of Church and Takacs for the prediction of scattering from x-ray mirrors is presented with a graphical user interface. The process of this development has clarified several problems which are of significant interest to the synchrotron community. These problems have been addressed to some extent, for example, for large astronomical telescopes, and at the National Ignition Facility for normal incidence optics, but not in the synchrotron community for grazing incidence optics. Since it is based on the Power Spectral Density (PSD) to provide a description of the deviations from ideal shape of the surface, accurate prediction of the scattering requires an accurate estimation of the PSD. Specifically, the spatial frequency range of measurement must be the correct one for the geometry of use of the optic--including grazing incidence and coherence effects, and the modifications to the PSD of the Optical Transfer Functions (OTF) of the measuring instruments must be removed. A solution for removal of OTF effects has been presented previously, the Binary Pseudo-Random Grating. Typically, the frequency range of a single instrument does not cover the range of interest, requiring the stitching together of PSD estimations. This combination generates its own set of difficulties in two dimensions. Fitting smooth functions to two dimensional PSDs, particularly in the case of spatial non-isotropy of the surface, which is often the case for optics in synchrotron beam lines, can be difficult. The convenient, and physically accurate fractal for one dimension does not readily transfer to two dimensions. Finally, a completely statistical description of scattering must be integrated with a deterministic low spatial frequency component in order to completely model the intensity near the image. An outline for approaching these problems, and our proposed experimental program is given.

McKinney, Wayne R.; Howells, M. R.; Yashchuk, V. V.

2008-09-30

186

Component Separation for Spectral X-ray Imaging using the Hybrid Pixel Camera XPAD3  

E-print Network

incorporated in the microCT demonstrator PIXSCAN. Several experiments have been led on data simulated of materials when compared to classical X-ray data processing in microCT, and to cancel beam hardening was developed and characterized at CPPM ([4], [5]) and incorporated in the micro-CT demonstrator PIXSCAN ([6

Paris-Sud XI, Université de

187

Numerical solution of the radiative transfer equation: X-ray spectral formation from cylindrical accretion onto a magnetized neutron star  

NASA Astrophysics Data System (ADS)

Context. Predicting the emerging X-ray spectra in several astrophysical objects is of great importance, in particular when the observational data are compared with theoretical models. This requires developing numerical routines for the solution of the radiative equation according to the expected physical conditions of the systems under study. Aims: We have developed an algorithm solving the radiative transfer equation in the Fokker-Planck approximation when both thermal and bulk Comptonization take place. The algorithm is essentially a relaxation method, where stable solutions are obtained when the system has reached its steady-state equilibrium. Methods: We obtained the solution of the radiative transfer equation in the two-dimensional domain defined by the photon energy E and optical depth of the system ? using finite-differences for the partial derivatives, and imposing specific boundary conditions for the solutions. We treated the case of cylindrical accretion onto a magnetized neutron star. Results: We considered a blackbody seed spectrum of photons with exponential distribution across the accretion column and for an accretion where the velocity reaches its maximum at the stellar surface and at the top of the accretion column, respectively. In both cases higher values of the electron temperature and of the optical depth ? produce flatter and harder spectra. Other parameters contributing to the spectral formation are the steepness of the vertical velocity profile, the albedo at the star surface, and the radius of the accretion column. The latter parameter modifies the emerging spectra in a specular way for the two assumed accretion profiles. Conclusions: The algorithm has been implemented in the xspec package for X-ray spectral fitting and is specifically dedicated to the physical framework of accretion at the polar cap of a neutron star with a high magnetic field (? 1012 G). This latter case is expected to be typical of accreting systems such as X-ray pulsars and supergiant fast X-ray transients.

Farinelli, R.; Ceccobello, C.; Romano, P.; Titarchuk, L.

2012-02-01

188

High spatial/spectral resolution x-ray observations and volumetric 3d modeling of superheated plasma in the planetary nebula BD+3003639  

NASA Astrophysics Data System (ADS)

Planetary nebulae (PNs) represent the last dying stages of evolution for sun-like stars. Though astronomers have traditionally studied PNs in optical emission lines, which mainly probe UV-photoionized gas, the study of X-ray emission from PNs offers insight into much more energetic process associated with stellar death. I present and analyze the results of multiple Chandra X-ray observations of the X-ray-bright, young PN BD+30.3639°. The Chandra datasets analyzed include a 3.5-day gratings spectroscopy observation for a total of 300 ks exposure and two direct CCD imaging observations. This thesis is based primarily on a detailed spatial/spectral analysis of the gratings data. Modeling of this gratings spectrum indicates the presence of a range of plasma temperatures from Tx ~1.7 × 10^6 K to 2.9 × 10^6 K and conclusively demonstrates that C and Ne are highly enhanced, while N and Fe are depleted. These results are generally consistent with earlier results obtained from X-ray CCD imaging spectroscopy of BD+30.3639°, but are far more precise. I obtained a direct Chandra CCD image in 2009 to compare with the Chandra CCD image obtained in 2000 and thereby to test the hypothesis that the X-ray emission could be due to fast-expanding jets. The error normalized difference image (2009 - 2000) does not reveal an apparent expansion signature, and comparison of flux images does not show any significant change in surface brightness over the 9 year span, indicating that the X-rays are generated by a quasi-spherical wind from the present-day central star. I argue that an exponential decline in flux below ~1 keV is caused by the contamination of the CCD imaging detector rather than a real decline in flux from the PN, and suggest that BD+30.3639° is a good candidate for the long-term calibration of this Chandra instrument. I construct 3-dimensional plasma models to describe the intrinsic structure of the X-ray-emitting region of BD+30.3639° by reproducing the grating spectroscopy results (both the 0th order image and dispersed images), taking into account the physical/chemical plasma components and intervening absorption obtained from spectral model fitting and Chandra's instrumental characteristics. This approach takes advantage of volumetric 3D modeling (V3D) routines under development at MIT's Kavli Institute. I present results in the form of X-ray spectra and images synthesized using spectral-V3D models. I outline how these studies of BD+30.3639° serve to constrain models of stellar evolution and PN morphologies and to guide the development of sophisticated models of the wind interactions responsible for the superheated gas within PNs.

Yu, Young Sam

189

Deconvolving X-Ray Spectral Variability Components in the Seyfert 1.5 NGC 3227  

NASA Astrophysics Data System (ADS)

We present the variability analysis of a 100 ks XMM-Newton observation of the Seyfert 1.5 active galaxy, NGC 3227. The observation found NGC 3227 in a period where its hard power-law component displayed remarkably little long-term variability. This lucky event allows us to clearly observe a soft spectral component undergoing a large-amplitude but slow flux variation. Using combined spectral and timing analysis, we isolate two independent variable continuum components and characterize their behavior as a function of timescale. Rapid and coherent variations throughout the 0.2-10 keV band reveal a spectrally hard (photon index ? ~ 1.7-1.8) power law, dominating the observed variability on timescales of 30 ks and shorter. Another component produces coherent fluctuations in the 0.2-2 keV range and is much softer (? ~ 3); it dominates the observed variability on timescales greater than 30 ks. Both components are viewed through the same absorbers identified in the time-averaged spectrum. The combined spectral and timing analysis breaks the degeneracy between models for the soft excess: it is consistent with a power-law or thermal Comptonized component but not with a blackbody or an ionized reflection component. We demonstrate that the rapid variability in NGC 3227 is intrinsic to continuum-emitting components and is not an effect of variable absorption.

Arévalo, P.; Markowitz, A.

2014-03-01

190

High-Resolution Soft X-Ray Spectral Analysis in the CK Region of Titanium Carbide (TiC) using the DV-X alpha Molecular Orbital Method  

SciTech Connect

We used the DV-X alpha method to analyze the high-resolution soft X-ray emission and absorption spectra in the CK region of titanium carbide (TiC). The spectral profiles of the X-ray emission and absorption can be ssuscfucelly reproduced by the occupied and unoccupied density of states (DOS ), respectively, in the C2p orbitals of the center carbon atoms in a Ti62C63 cluster model, suggesting that the center carbon atom in a large cluster model expanded to the cubic-structured 53 (= 125) atoms provides sufficient DOS for the X-ray spectral analysis of rock-salt structured metal carbides.

Shimomura, Kenta; Muramatsu, Yasuji; Denlinger, Jonathan D.; Gullikson, Eric M.

2008-10-31

191

X-Ray Yields from Elements in the Range Beryllium to Aluminium  

Microsoft Academic Search

ABSOLUTE measurements have been made, it is believed for the first time, of the K X-ray quantum yields resulting from electron bombardment of solid targets containing the elements beryllium, boron, oxygen and fluorine. For beryllium and boron 99 per cent pure targets were used while beryllium oxide and lithium fluoride were used for the oxygen and fluorine yields; corrections were

A. J. Campbell; R. Gibbons

1962-01-01

192

Learning to Apply Metrology Principles to the Measurement of X-ray Intensities in the 500 eV to 110 keV Energy Range  

SciTech Connect

National Security Technologies, LLC (NSTec), Livermore Operations, has two optical radiation calibration laboratories accredited by “the National Voluntary Laboratories Accreditation Program (NVLAP) which is the accrediting body of” the National Institute of Standards and Technology (NIST), and is now working towards accreditation for its X-ray laboratories. NSTec operates several laboratories with X-ray sources that generate X-rays in the energy range from 50 eV to 115 keV. These X-ray sources are used to characterize and calibrate diagnostics and diagnostic components used by the various national laboratories, particularly for plasma analysis on the Lawrence Livermore National Laboratory (LLNL) National Ignition Facility (NIF). Because X-ray photon flux measurement methods that can be accredited, i.e., traceable to NIST, have not been developed for sources operating in these energy ranges, NSTec, NIST, and the National Voluntary Accreditation Program (NVLAP) together have defined a path toward the development and validation of accredited metrology methods for X-ray energies. The methodology developed for the high energy X-ray (HEX) Laboratory was NSTec’s starting point for X-ray metrology accreditation and will be the basis for the accredited processes in the other X-ray laboratories. This paper will serve as a teaching tool, by way of this example using the NSTec X-ray sources, for the process and methods used in developing an accredited traceable metrology.

Haugh, M. J.; Pond, T.; Silbernagel, C.; Torres, P.; Marlett, K.; Goldin, F.; Cyr, S.

2011-02-08

193

Study on the influence of X-ray tube spectral distribution on the analysis of bulk samples and thin films: Fundamental parameters method and theoretical coefficient algorithms  

NASA Astrophysics Data System (ADS)

Knowledge of X-ray tube spectral distribution is necessary in theoretical methods of matrix correction, i.e. in both fundamental parameter (FP) methods and theoretical influence coefficient algorithms. Thus, the influence of X-ray tube distribution on the accuracy of the analysis of thin films and bulk samples is presented. The calculations are performed using experimental X-ray tube spectra taken from the literature and theoretical X-ray tube spectra evaluated by three different algorithms proposed by Pella et al. (X-Ray Spectrom. 14 (1985) 125-135), Ebel (X-Ray Spectrom. 28 (1999) 255-266), and Finkelshtein and Pavlova (X-Ray Spectrom. 28 (1999) 27-32). In this study, Fe-Cr-Ni system is selected as an example and the calculations are performed for X-ray tubes commonly applied in X-ray fluorescence analysis (XRF), i.e., Cr, Mo, Rh and W. The influence of X-ray tube spectra on FP analysis is evaluated when quantification is performed using various types of calibration samples. FP analysis of bulk samples is performed using pure-element bulk standards and multielement bulk standards similar to the analyzed material, whereas for FP analysis of thin films, the bulk and thin pure-element standards are used. For the evaluation of the influence of X-ray tube spectra on XRF analysis performed by theoretical influence coefficient methods, two algorithms for bulk samples are selected, i.e. Claisse-Quintin (Can. Spectrosc. 12 (1967) 129-134) and COLA algorithms (G.R. Lachance, Paper Presented at the International Conference on Industrial Inorganic Elemental Analysis, Metz, France, June 3, 1981) and two algorithms (constant and linear coefficients) for thin films recently proposed by Sitko (X-Ray Spectrom. 37 (2008) 265-272).

Sitko, Rafa?

2008-11-01

194

Experimental study of spectral and spatial distribution of solar X-rays  

NASA Technical Reports Server (NTRS)

The study of the physical conditions within the solar corona and the development of instrumentation and technical expertise necessary for advanced studies of solar X-ray emission are reported. Details are given on the Aerobee-borne-X-ray spectrometer/monochromator and also on the observing program. Preliminary discussions of some results are presented and include studies of helium-like line emission, mapping O(VII) and Ne(IX) lines, survey of O(VII) and Ne(IX) lines, study of plage regions and small flares, and analysis of line emission from individual active regions. It is concluded that the use of large-area collimated Bragg spectrometers to scan narrow wavelength intervals and the capability of the SPARCS pointing control to execute a complex observing program are established.

Acton, L. W.; Catura, R. C.; Culhane, J. L.

1972-01-01

195

3D ISM-Shock Spectral Emission: X-ray models for Radio Galaxy SED Modeling  

E-print Network

Galaxies form out of small fluctuations in a smoothly expanding Universe. However, the initial gravitational collapse phase is accompanied by the formation of supermassive black holes and clusters of massive stars. Black holes and star clusters generate powerful outflows in the form of jets and superwinds that interact with still infalling gas, possibly regulating the galaxy formation process, initiating new sites of star formation, and carrying chemically enriched gas to the intergalactic medium. Unfortunately, beyond this qualitative description our detailed theoretical understanding is poor. New results from 3D simulations of a GPS/CSS galaxy, with gravitational potentials included, shed some new light on the jet driven outflow process in particular. New code capabilites to predict detailed X-ray spectra from multi-dimensional time-dependent dynamics simulations of Galaxy Feedback, and will be useful for future interpretation of X-ray and radio SEDs of forming galaxies.

Ralph S. Sutherland

2005-02-17

196

Time-resolved x-ray transmission grating spectrometer for studying laser-produced plasmas  

Microsoft Academic Search

The development of a new time-resolved x-ray spectrometer is reported in which a free-standing x-ray transmission grating is coupled to a soft x-ray streak camera. The instrument measures continuous x-ray spectra with 20-psec temporal resolution and moderate spectral resolution (..delta..lambda> or =1 A) over a broad spectral range (0.1--5 keV) with high sensitivity and large information recording capacity. Its capabilities

N. M. Ceglio; R. L. Kauffman; A. M. Hawryluk; H. Medecki

1983-01-01

197

Spectral and x-ray diffraction analyses of lanthanide oxide sulfides  

SciTech Connect

Results of investigations are presented of the homogeneity as well as the crystallochemical and optical properties of lanthanide oxide sulfides used as luminophors. The investigations carried out have made it possible to ascertain the unit-cell parameters of the REE oxide sulfides, to obtain for the first time the diffusion reflection spectra, and to show the scope for monitoring the phase composition during the synthesis of REE oxide sulfides by x-ray diffraction analysis.

Laptev, V.I.; Suponitskii, Y.L.; Vorob'ev, A.F.

1985-06-01

198

Diagnosing Shock-Heated, Direct-Drive Plastic Targets with Spectrally Resolved X-Ray Scattering  

Microsoft Academic Search

Initial x-ray scattering experiments have been carried out on OMEGA to measure the n_e, T_e, and Z in shock-heated, direct-drive targets. Plastic, planar foils were irradiated for 3 ns with six overlapped beams providing a uniform drive intensity of ˜10^14 W\\/cm^2 with an ˜0.5-mm laser spot. The 1-D hydrocode LILAC predicts that the shock-heated target will have ne ˜ 2.5

H. Sawada; S. P. Regan; T. R. Boehly; I. V. Igumenshchev; V. N. Goncharov; F. J. Marshall; B. Yaakobi; T. C. Sangster; D. D. Meyerhofer; G. Gregori; D. G. Hicks; S. H. Glenzer; O. L. Landen

2004-01-01

199

A Comprehensive X-ray Spectral Analysis of the Seyfert 1.5 NGC 3227  

E-print Network

We present results of a 100 ks XMM observation of the Seyfert 1.5 NGC 3227. Our best-fit broadband model to the pn spectrum consists of a moderately flat (photon index 1.57) hard X-ray power-law absorbed by cold gas with N_H = 3 * 10^21 cm^-2, plus a strong soft excess, modeled as a steep power law with a photon index of 3.35, absorbed by cold gas with N_H = 9 * 10^20 cm^-2. The soft excess normalization increases by ~20% in ~20 ks, independently of the hard X-ray component, and the UV continuum, tracked via the OM, also shows a strong increasing trend over the observation, consistent with reprocessing of soft X-ray emission. Warm absorber signatures are evident in both the EPIC and RGS; we model two layers, with log(xi) = 1.2 and 2.9 erg cm s^-1, and with similar column densities (~1-2 * 10^21 cm^-2). The outflow velocities relative to systemic of the high- and low-ionization absorbers are estimated to be -(2060(+240,-170)) km/s and -(420(+430,-190)) km/s, respectively. The Fe K alpha line width FWHM is 7000...

Markowitz, A; George, I M; Braito, V; Smith, R; Vaughan, S; Arévalo, P; Tombesi, F

2008-01-01

200

X-Ray Spectral Study of a Newly Ginga-Detected DQ Her  

NASA Technical Reports Server (NTRS)

The goal of this proposal was to observe with ASCA, YY Dra, a DQ Her objected identified using archival Ginga data, in order to complete a high quality ASCA study of Ginga-detected DQ Her stars. There are relatively few DQ Her objects characterized by X-ray pulsations at the white dwarf spin period and optical pulsations at the orbital period and extremely complex X-ray spectra. The ASCA study included seven DQ Her objects. ASCA is able to resolve separate components of the Fe K emission and to set constraints on temperatures in the accretion column, and the mass of the white dwarf. The 40ksec observation, corresponding to roughly three orbital cycles, allowed the study of continuum changes with spin and orbital phase. The ASCA spectrum can be modelled as a bremsstrahlung with evidence for cold, helium-like and hydrogen-like iron emission, and helium-like argon emission. The lines yield a plasma temperature that is compatible with that from the continuum modelling (10-20 keV). The X-ray light-curve clearly shows sinusoidal variation from the spin pulse and shallow absorption dips at the orbital cycle. The derived parameters match well with the -accretion curtain, model for intermediate polars. The results will be presented together with the seven other DQ Her type sources observed with ASCA.

Vrtilek, S.

2001-01-01

201

Spectral and temporal properties of the supergiant fast X-ray transient IGR J18483-0311 observed by INTEGRAL  

NASA Astrophysics Data System (ADS)

Context. IGR J18483-0311 is a supergiant fast X-ray transient whose compact object is located in a wide (18.5 d) and eccentric (e ~ 0.4) orbit, which shows sporadic outbursts that reach X-ray luminosities of ~1036 erg s-1. Aims: We investigated the timing properties of IGR J18483-0311 and studied the spectra during bright outbursts by fitting physical models based on thermal and bulk Comptonization processes for accreting compact objects. Methods: We analysed archival INTEGRAL data collected in the period 2003-2010, focusing on the observations with IGR J18483-0311 in outburst. We searched for pulsations in the INTEGRAL light curves of each outburst. We took advantage of the broadband observing capability of INTEGRAL for the spectral analysis. Results: We observed 15 outbursts, seven of which we report here for the first time. This data analysis almost doubles the statistics of flares of this binary system detected by INTEGRAL. A refined timing analysis did not reveal a significant periodicity in the INTEGRAL observation where a ~21 s pulsation was previously detected. Neither did we find evidence for pulsations in the X-ray light curve of an archival XMM-Newton observation of IGR J18483-0311. In the light of these results the nature of the compact object in IGR J18483-0311 is unclear. The broadband X-ray spectrum of IGR J18483-0311 in outburst is well fitted by a thermal and bulk Comptonization model of blackbody seed photons by the infalling material in the accretion column of a neutron star. We also obtained a new measurement of the orbital period using the Swift/BAT light curve.

Ducci, L.; Doroshenko, V.; Sasaki, M.; Santangelo, A.; Esposito, P.; Romano, P.; Vercellone, S.

2013-11-01

202

Numerical Solution of the Radiative Transfer Equation: X-Ray Spectral Formation from Cylindrical Accretion onto a Magnetized Neutron Star  

NASA Technical Reports Server (NTRS)

Predicting the emerging X-ray spectra in several astrophysical objects is of great importance, in particular when the observational data are compared with theoretical models. This requires developing numerical routines for the solution of the radiative transfer equation according to the expected physical conditions of the systems under study. Aims. We have developed an algorithm solving the radiative transfer equation in the Fokker-Planck approximation when both thermal and bulk Comptonization take place. The algorithm is essentially a relaxation method, where stable solutions are obtained when the system has reached its steady-state equilibrium. Methods. We obtained the solution of the radiative transfer equation in the two-dimensional domain defined by the photon energy E and optical depth of the system pi using finite-differences for the partial derivatives, and imposing specific boundary conditions for the solutions. We treated the case of cylindrical accretion onto a magnetized neutron star. Results. We considered a blackbody seed spectrum of photons with exponential distribution across the accretion column and for an accretion where the velocity reaches its maximum at the stellar surface and at the top of the accretion column, respectively. In both cases higher values of the electron temperature and of the optical depth pi produce flatter and harder spectra. Other parameters contributing to the spectral formation are the steepness of the vertical velocity profile, the albedo at the star surface, and the radius of the accretion column. The latter parameter modifies the emerging spectra in a specular way for the two assumed accretion profiles. Conclusions. The algorithm has been implemented in the XPEC package for X-ray fitting and is specifically dedicated to the physical framework of accretion at the polar cap of a neutron star with a high magnetic field (approx > 10(exp 12) G). This latter case is expected to be of typical accreting systems such as X-ray pulsars and supergiant fast X ray transients.

Fairnelli, R.; Ceccobello, C.; Romano, P.; Titarchuk, L.

2011-01-01

203

A complete X-ray spectral coverage of the 2010 May-June outbursts of Circinus X-1  

NASA Astrophysics Data System (ADS)

Context. Circinus X-1 is a neutron-star-accreting X-ray binary in a wide (Porb = 16.6 d), eccentric orbit. After two years of relatively low X-ray luminosity, in May 2010 Circinus X-1 went into outburst, reaching 0.4 Crab flux. This outburst lasted for about two orbital cycles and was followed by another shorter and fainter outburst in June. Aims: We focus here on the broadband X-ray spectral evolution of the source as it spans about three order of magnitudes in flux. We attempt to relate luminosity, spectral shape, local absorption, and orbital phase. Methods: We use multiple Rossi-XTE/PCA (3.0-25 keV) and Swift/XRT (1.0-9.0 keV) observations and a 20 ks long Chandra/HETGS observation (1.0-9.0 keV), to comprehensively track the spectral evolution of the source during all the outbursting phases. These observations were taken every two/three days and cover about four orbital cycles. The PCA data mostly cover the major outburst, the XRT data monitor the declining phase of the major outburst and all the phases of the minor outburst, and Chandra data provide an essential snapshot of the end of this overall outbursting phase. Results: The X-ray spectrum can be satisfactorily described by a thermal Comptonization model with variable neutral local absorption in all phases of the outburst. No other additive component is statistically required. The first outburst decays linearly, with an ankle in the light curve as the flux decreases below ~5 × 10-10 erg cm-2 s-1. At the same time, the source shows a clear spectral state transition from an optically thick to an optically thin state. While the characteristics of the first, bright, outburst can be interpreted within the disk-instability scenario, the following, minor, outburst shows peculiarities that cannot be easily reconciled in this framework. Tables 1-3 are available in electronic form at http://www.aanda.org

D'Aì, A.; Bozzo, E.; Papitto, A.; Iaria, R.; Di Salvo, T.; Burderi, L.; Riggio, A.; Egron, E.; Robba, N. R.

2012-07-01

204

A statistical analysis of the broadband 0.1 to 3.5 keV spectral properties of X-ray-selected active galactic nuclei  

NASA Technical Reports Server (NTRS)

We survey the broadband spectral properties of approximately 500 X-ray-selected active galactic nuclei (AGNs) observed with the Einstein Observatory. Included in this survey are the approximately 450 AGNs in the Extended Medium Sensitivity Survey (EMSS) of Gioia et al. (1990) and the approximately 50 AGNs in the Ultrasoft Survey of Cordova et al. (1992). We present a revised version of the latter sample, based on the post publication discovery of a software error in the Einstein Rev-1b processing. We find that the mean spectral index of the AGNs between 0.1 and 0.6 keV is softer, and the distribution of indices wider, than previous estimates based on analyses of the X-ray spectra of optically selected AGNs. A subset of these AGNs exhibit flux variabiulity, some on timescales as short as 0.05 days. A correlation between radio and hard X-ray luminosity is confirmed, but the data do not support a correlation between the radio and soft X-ray luminosities, or between radio loudness and soft X-ray spectral slope. Evidence for physically distinct soft and hard X-ray components is found, along with the possibility of a bias in previous optically selected samples toward selection of AGNs with flatter X-ray spectra.

Thompson, R. J.; Cordova, F. A.

1994-01-01

205

Tungsten anode spectral model using interpolating cubic splines: Unfiltered x-ray spectra from 20 kV to 640 kV  

SciTech Connect

Purpose: Monte Carlo methods were used to generate lightly filtered high resolution x-ray spectra spanning from 20 kV to 640 kV. Methods: X-ray spectra were simulated for a conventional tungsten anode. The Monte Carlo N-Particle eXtended radiation transport code (MCNPX 2.6.0) was used to produce 35 spectra over the tube potential range from 20 kV to 640 kV, and cubic spline interpolation procedures were used to create piecewise polynomials characterizing the photon fluence per energy bin as a function of x-ray tube potential. Using these basis spectra and the cubic spline interpolation, 621 spectra were generated at 1 kV intervals from 20 to 640 kV. The tungsten anode spectral model using interpolating cubic splines (TASMICS) produces minimally filtered (0.8 mm Be) x-ray spectra with 1 keV energy resolution. The TASMICS spectra were compared mathematically with other, previously reported spectra. Results: Using pairedt-test analyses, no statistically significant difference (i.e., p > 0.05) was observed between compared spectra over energy bins above 1% of peak bremsstrahlung fluence. For all energy bins, the correlation of determination (R{sup 2}) demonstrated good correlation for all spectral comparisons. The mean overall difference (MOD) and mean absolute difference (MAD) were computed over energy bins (above 1% of peak bremsstrahlung fluence) and over all the kV permutations compared. MOD and MAD comparisons with previously reported spectra were 2.7% and 9.7%, respectively (TASMIP), 0.1% and 12.0%, respectively [R. Birch and M. Marshall, “Computation of bremsstrahlung x-ray spectra and comparison with spectra measured with a Ge(Li) detector,” Phys. Med. Biol. 24, 505–517 (1979)], 0.4% and 8.1%, respectively (Poludniowski), and 0.4% and 8.1%, respectively (AAPM TG 195). The effective energy of TASMICS spectra with 2.5 mm of added Al filtration ranged from 17 keV (at 20 kV) to 138 keV (at 640 kV); with 0.2 mm of added Cu filtration the effective energy was 9 keV at 20 kV and 169 keV at 640 kV. Conclusions: Ranging from 20 kV to 640 kV, 621 x-ray spectra were produced and are available at 1 kV tube potential intervals. The spectra are tabulated at 1 keV intervals. TASMICS spectra were shown to be largely equivalent to published spectral models and are available in spreadsheet format for interested users by emailing the corresponding author (JMB)

Hernandez, Andrew M. [Biomedical Engineering Graduate Group, University of California Davis, Sacramento, California 95817 (United States)] [Biomedical Engineering Graduate Group, University of California Davis, Sacramento, California 95817 (United States); Boone, John M., E-mail: john.boone@ucdmc.ucdavis.edu [Departments of Radiology and Biomedical Engineering, Biomedical Engineering Graduate Group, University of California Davis, Sacramento, California 95817 (United States)

2014-04-15

206

Spectral Modeling of the Charge-exchange X-Ray Emission from M82  

NASA Astrophysics Data System (ADS)

It has been proposed that the charge-exchange (CX) process at the interface between hot and cool interstellar gases could contribute significantly to the observed soft X-ray emission in star-forming galaxies. We analyze the XMM-Newton/reflection grating spectrometer (RGS) spectrum of M82 using a newly developed CX model combined with a single-temperature thermal plasma to characterize the volume-filling hot gas. The CX process is largely responsible for not only the strongly enhanced forbidden lines of the K? triplets of various He-like ions but also good fractions of the Ly? transitions of C VI (~87%), O VIII, and N VII (gsim50%) as well. In total about a quarter of the X-ray flux in the RGS 6-30 Å band originates in the CX. We infer an ion incident rate of 3 × 1051 s-1 undergoing CX at the hot and cool gas interface and an effective area of the interface of ~2 × 1045 cm2 that is one order of magnitude larger than the cross section of the global biconic outflow. With the CX contribution accounted for, the best-fit temperature of the hot gas is 0.6 keV, and the metal abundances are approximately solar. We further show that the same CX/thermal plasma model also gives an excellent description of the EPIC-pn spectrum of the outflow Cap, projected at 11.6 kpc away from the galactic disk of M82. This analysis demonstrates that the CX is potentially an important contributor to the X-ray emission from starburst galaxies and also an invaluable tool to probe the interface astrophysics.

Zhang, Shuinai; Wang, Q. Daniel; Ji, Li; Smith, Randall K.; Foster, Adam R.; Zhou, Xin

2014-10-01

207

Attosecond broadband multilayer mirrors for the water window spectral range  

NASA Astrophysics Data System (ADS)

Recent advances in the development of attosecond soft X-ray sources ranging into the `water window' spectral range, between the carbon 1s and oxygen 1s states (284 eV - 543 eV), are also driving the development of suited broadband multilayer optics for attosecond beam steering and dispersion management. The relatively low intensity of current High Harmonic Generation (HHG) soft X-ray sources calls for an efficient use of photons, thus the development of low-loss multilayer optics is of uttermost importance. Here, we report about the realization of atomically smooth interfaces in broadband CrSc multilayer mirrors by an optimized ion beam deposition and assisted interface polishing process.

Guggenmos, A.; Radünz, S.; Rauhut, R.; Hofstetter, M.; Venkatesan, S.; Wochnik, A.; Scheu, C.; Gullikson, E.; Fischer, S.; Nickel, B.; Kleineberg, U.

2014-09-01

208

X-ray structural and spectral study of the cobalt(II) chloride complex with papaverine  

SciTech Connect

A complex of cobalt(II) chloride with papaverine is characterized by x-ray diffraction method (autodiffractometer, 1917 reflections, R = 0.080). Crystals are tetragonal, a = b = 18.393(2) {angstrom}, c = 12.396(4) {angstrom}, Z = 4, space group P{bar 4}/n. The crystal structure is composed of tetrahedral [CoCl{sub 4}]{sup 2-} anions situated in a special position on the {bar 4} axis, cations of the protonated papaverine, and two types of water molecules. The structure exhibits short hydrogen-bond-type contacts C-H...Cl between anions and cations and C-H...O between cations.

Sabirov, V.Kh.; Struchkov, Yu.T.; Nava, E.U. [Kurnakov Institute of General and Inorganic Chemistry, Moscow (Russian Federation)] [and others

1994-05-01

209

Studies on x-ray and UV emissions in electron cyclotron resonance x-ray sourcea)  

NASA Astrophysics Data System (ADS)

A novel electron cyclotron resonance x-ray source is constructed based on the ECR technique. In this paper, the possibility of using the ECR x-ray source for producing UV rays by optimizing the plasma parameters is explored. X-ray and UV emissions from the ECR x-ray source are carried out for argon, nitrogen, and CO2 plasma. The x-ray spectral and dose measurements are carried with NaI(Tl) based spectrometer and dosimeter, respectively. For UV measurement, a quartz window arrangement is made at the exit port and the UV intensity is measured at 5cm from the quartz plate using UV meter. The x-ray and UV emissions are carried out for different microwave power levels and gas pressures. The x-ray emission is observed in the pressure range ?10-5Torr, whereas the UV emission is found to be negligible for the gas pressures <10-5Torr and it starts increasing in the pressure range between 10-5 and 10-3Torr. At high-pressure range, collision frequency of electron-atom is large which leads to the higher UV flux. At low pressure, the electron-atom collision frequency is low and hence the electrons reach high energy and by hitting the cavity wall produces higher x-ray flux. By choosing proper experimental conditions and plasma gas species, the same source can be used as either an x-ray source or an UV source.

Baskaran, R.; Selvakumaran, T. S.

2008-02-01

210

Versatile high-repetition-rate phase-locked chopper system for fast timing experiments in the vacuum ultraviolet and x-ray spectral region.  

PubMed

A novel light chopper system for fast timing experiments in the vacuum-ultraviolet (VUV) and x-ray spectral region has been developed. It can be phase-locked and synchronized with a synchrotron radiation storage ring, accommodating repetition rates in the range of ~8 to ~120 kHz by choosing different sets of apertures and subharmonics of the ring frequency (MHz range). Also the opening time of the system can be varied from some nanoseconds to several microseconds to meet the needs of a broad range of applications. Adjusting these parameters, the device can be used either for the generation of single light pulses or pulse packages from a microwave driven, continuous He gas discharge lamp or from storage rings which are otherwise often considered as quasi-continuous light sources. This chopper can be utilized for many different kinds of experiments enabling, for example, unambiguous time-of-flight (TOF) multi-electron coincidence studies of atoms and molecules excited by a single light pulse as well as time-resolved visible laser pump x-ray probe electron spectroscopy of condensed matter in the valence and core level region. PMID:22299937

Plogmaker, Stefan; Linusson, Per; Eland, John H D; Baker, Neville; Johansson, Erik M J; Rensmo, Håkan; Feifel, Raimund; Siegbahn, Hans

2012-01-01

211

Characterizations of MCP performance in the hard x-ray range (6-25 keV)a)  

NASA Astrophysics Data System (ADS)

MCP detector performance at hard x-ray energies from 6 to 25 keV was recently investigated using NSLS beamline X15A at BNL. Measurements were made with an NSTec Gen-II (H-CA-65) framing camera, based on a Photonis MCP with ˜10 ?m in diameter pores, ˜12 ?m center-center spacing, an L/D ratio of 46, and a bias angle of 8°. The MCP characterizations were focused on (1) energy and angle dependent sensitivity, (2) energy and angle dependent spatial resolution, (3) energy dependent gain performance, and (4) energy dependent dynamic range. These measurement corroborated simulation results using a Monte Carlo model that included hard x-ray interactions and the subsequent electron cascade in the MCP.

Wu, Ming; Moy, Ken; Kruschwitz, Craig; Rochau, Greg

2014-11-01

212

High quality x-ray absorption spectroscopy measurements with long energy range at high pressure using diamond anvil cell.  

PubMed

We describe an approach for acquiring high quality x-ray absorption fine structure (XAFS) spectroscopy spectra with wide energy range at high pressure using diamond anvil cell (DAC). Overcoming the serious interference of diamond Bragg peaks is essential for combining XAFS and DAC techniques in high pressure research, yet an effective method to obtain accurate XAFS spectrum free from DAC induced glitches has been lacking. It was found that these glitches, whose energy positions are very sensitive to the relative orientation between DAC and incident x-ray beam, can be effectively eliminated using an iterative algorithm based on repeated measurements over a small angular range of DAC orientation, e.g., within +/-3 degrees relative to the x-ray beam direction. Demonstration XAFS spectra are reported for rutile-type GeO2 recorded by traditional ambient pressure and high pressure DAC methods, showing similar quality at 440 eV above the absorption edge. Accurate XAFS spectra of GeO2 glass were obtained at high pressure up to 53 GPa, providing important insight into the structural polymorphism of GeO2 glass at high pressure. This method is expected be applicable for in situ XAFS measurements using a diamond anvil cell up to ultrahigh pressures. PMID:19655966

Hong, Xinguo; Newville, Matthew; Prakapenka, Vitali B; Rivers, Mark L; Sutton, Stephen R

2009-07-01

213

X-ray absorption spectral studies of copper (II) mixed ligand complexes  

NASA Astrophysics Data System (ADS)

X-ray absorption spectra at the K-edge of copper have been studied in two copper mixed ligand complexes, one having tetramethyethylenediamine (tmen) and the other having tetraethyethylenediamine (teen) as one of the ligands. The spectra have been recorded at BL-8 dispersive extended X-ray absorption fine structure (EXAFS) beamline at the 2.5 GeV INDUS- 2 synchrotron, RRCAT, Indore, India. The data obtained has been processed using the data analysis program Athena. The energy of the K-absorption edge, chemical shift, edge-width and shift of the principal absorption maximum in the complexes have been determined and discussed. The values of these parameters have been found to be approximately the same in both the complexes indicating that the two complexes possess similar chemical environment around the copper metal atom. The chemical shift has been utilized to estimate effective nuclear charge on the absorbing atom. The normalized EXAFS spectra have been Fourier transformed. The position of the first peak in the Fourier transform gives the value of first shell bond length, which is shorter than the actual bond length because of energy dependence of the phase factors in the sine function of the EXAFS equation. This distance is thus the phase- uncorrected bond length. Bond length has also been determined by Levy's, Lytle's and Lytle, Sayers and Stern's (LSS) methods. The results obtained from LSS and the Fourier transformation methods are comparable with each other, since both are phase uncorrected bond lengths.

Soni, B.; Dar, Davood Ah; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

2014-09-01

214

Short-range order in amorphous SiO{sub x} by x ray photoelectron spectroscopy  

SciTech Connect

The Si 2p x ray photoelectron spectra of SiO{sub x} with a different composition of 0 {<=} x {<=} 2 have been studied experimentally and theoretically. The SiO{sub x} films were prepared by low-pressure chemical vapor deposition from SiH{sub 4} and N{sub 2}O source at 750 deg. C. Neither random bonding nor random mixture models can adequately describe the structure of these compounds. The interpretation of the experimental results is discussed according to a large scale potential fluctuation due to the spatial variation of chemical composition in SiO{sub x}.

Novikov, Yu. N.; Gritsenko, V. A. [Institute of Semiconductor Physics, Novosibirsk 630090 (Russian Federation)

2011-07-01

215

Warm Absorbers in X-rays (WAX), a comprehensive high resolution grating spectral study of a sample of Seyfert galaxies  

NASA Astrophysics Data System (ADS)

We present results from a homogeneous analysis of the broadband 0.3-10 keV CCD resolution as well as of soft X-ray high-resolution grating spectra of a hard X-ray flux-limited sample of 26 Seyfert galaxies observed with XMM-Newton. We could put a strict lower limit on the detection fraction of 50%. We find a gap in the distribution of the ionisation parameter in the range 0.5X-rays. The WA parameters show no correlation among themselves, except for one case. The shallow slope of the log? versus logv_{out} linear regression (0.12± 0.03) is inconsistent with the scaling laws predicted by radiation or magneto-hydrodynamic-driven winds. Our results suggest also that WA and Ultra Fast Outflows (UFOs) do not represent extreme manifestation of the same astrophysical system.

Laha, S.; Guainazzi, M.; Dewangan, G.; Chakravorty, S.; Kembhavi, A.

2014-07-01

216

Constraints on relativistic jets in quiescent black hole X-ray binaries from broad-band spectral modelling  

NASA Astrophysics Data System (ADS)

The nature of black hole jets at the lowest detectable luminosities remains an open question, largely due to a dearth of observational constraints. Here, we present a new, nearly simultaneous broad-band spectrum of the black hole X-ray binary (BHXB) XTE J1118+480 at an extremely low Eddington ratio (LX ˜ 10-8.5LEdd). Our new spectral energy distribution (SED) includes the radio, near-infrared, optical, ultraviolet, and X-ray wavebands. XTE J1118+480 is now the second BHXB at such a low Eddington ratio with a well-sampled SED, thereby providing new constraints on highly sub-Eddington accretion flows and jets, and opening the door to begin comparison studies between systems. We apply a multizone jet model to the new broad-band SED, and we compare our results to previous fits to the same source using the same model at 4-5 decades higher luminosity. We find that after a BHXB transitions to the so-called quiescent spectral state, the jet base becomes more compact (by up to an order of magnitude) and slightly cooler (by at least a factor of 2). Our preferred model fit indicates that jet particle acceleration is much weaker after the transition into quiescence. That is, accelerated non-thermal particles no longer reach high enough Lorentz factors to contribute significant amounts of synchrotron X-ray emission. Instead, the X-ray waveband is dominated by synchrotron self-Compton emission from a population of mildly relativistic electrons with a quasi-thermal velocity distribution that are associated with the jet base. The corresponding (thermal) synchrotron component from the jet base emits primarily in the infrared through ultraviolet wavebands. Our results on XTE J1118+480 are consistent with broad-band modelling for A0620-00 (the only other comparably low Eddington ratio BHXB with a well-sampled SED) and for Sgr A* (the quiescent supermassive black hole at the Galactic centre). The above could therefore represent a canonical baseline geometry for accreting black holes in quiescence. We conclude with suggestions for future studies to further investigate the above scenario.

Plotkin, Richard M.; Gallo, Elena; Markoff, Sera; Homan, Jeroen; Jonker, Peter G.; Miller-Jones, James C. A.; Russell, David M.; Drappeau, Samia

2015-02-01

217

Range verification for eye proton therapy based on proton-induced x-ray emissions from implanted metal markers  

NASA Astrophysics Data System (ADS)

Metal fiducial markers are often implanted on the back of the eye before proton therapy to improve target localization and reduce patient setup errors. We aim to detect characteristic x-ray emissions from metal targets during proton therapy to verify the treatment range accuracy. Initially gold was chosen for its biocompatibility properties. Proton-induced x-ray emissions (PIXE) from a 15 mm diameter gold marker were detected at different penetration depths of a 59 MeV proton beam at the CATANA proton facility at INFN-LNS (Italy). The Monte Carlo code Geant4 was used to reproduce the experiment and to investigate the effect of different size markers, materials, and the response to both mono-energetic and fully modulated beams. The intensity of the emitted x-rays decreases with decreasing proton energy and thus decreases with depth. If we assume the range to be the depth at which the dose is reduced to 10% of its maximum value and we define the residual range as the distance between the marker and the range of the beam, then the minimum residual range which can be detected with 95% confidence level is the depth at which the PIXE peak is equal to 1.96 ?bkg, which is the standard variation of the background noise. With our system and experimental setup this value is 3 mm, when 20 GyE are delivered to a gold marker of 15 mm diameter. Results from silver are more promising. Even when a 5 mm diameter silver marker is placed at a depth equal to the range, the PIXE peak is 2.1 ?bkg. Although these quantitative results are dependent on the experimental setup used in this research study, they demonstrate that the real-time analysis of the PIXE emitted by fiducial metal markers can be used to derive beam range. Further analysis are needed to demonstrate the feasibility of the technique in a clinical setup.

La Rosa, Vanessa; Kacperek, Andrzej; Royle, Gary; Gibson, Adam

2014-06-01

218

Range verification for eye proton therapy based on proton-induced x-ray emissions from implanted metal markers.  

PubMed

Metal fiducial markers are often implanted on the back of the eye before proton therapy to improve target localization and reduce patient setup errors. We aim to detect characteristic x-ray emissions from metal targets during proton therapy to verify the treatment range accuracy. Initially gold was chosen for its biocompatibility properties. Proton-induced x-ray emissions (PIXE) from a 15 mm diameter gold marker were detected at different penetration depths of a 59 MeV proton beam at the CATANA proton facility at INFN-LNS (Italy). The Monte Carlo code Geant4 was used to reproduce the experiment and to investigate the effect of different size markers, materials, and the response to both mono-energetic and fully modulated beams. The intensity of the emitted x-rays decreases with decreasing proton energy and thus decreases with depth. If we assume the range to be the depth at which the dose is reduced to 10% of its maximum value and we define the residual range as the distance between the marker and the range of the beam, then the minimum residual range which can be detected with 95% confidence level is the depth at which the PIXE peak is equal to 1.96 ?(bkg), which is the standard variation of the background noise. With our system and experimental setup this value is 3 mm, when 20 GyE are delivered to a gold marker of 15 mm diameter. Results from silver are more promising. Even when a 5 mm diameter silver marker is placed at a depth equal to the range, the PIXE peak is 2.1 ?(bkg). Although these quantitative results are dependent on the experimental setup used in this research study, they demonstrate that the real-time analysis of the PIXE emitted by fiducial metal markers can be used to derive beam range. Further analysis are needed to demonstrate the feasibility of the technique in a clinical setup. PMID:24786372

La Rosa, Vanessa; Kacperek, Andrzej; Royle, Gary; Gibson, Adam

2014-06-01

219

X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue  

NASA Astrophysics Data System (ADS)

Context. Aims: Active galactic nuclei are known to have complex X-ray spectra that depend on both the properties of the accreting super-massive black hole (e.g. mass, accretion rate) and the distribution of obscuring material in its vicinity (i.e. the "torus"). Often however, simple and even unphysical models are adopted to represent the X-ray spectra of AGN, which do not capture the complexity and diversity of the observations. In the case of blank field surveys in particular, this should have an impact on e.g. the determination of the AGN luminosity function, the inferred accretion history of the Universe and also on our understanding of the relation between AGN and their host galaxies. Methods: We develop a Bayesian framework for model comparison and parameter estimation of X-ray spectra. We take into account uncertainties associated with both the Poisson nature of X-ray data and the determination of source redshift using photometric methods. We also demonstrate how Bayesian model comparison can be used to select among ten different physically motivated X-ray spectral models the one that provides a better representation of the observations. This methodology is applied to X-ray AGN in the 4 Ms Chandra Deep Field South. Results: For the ~350 AGN in that field, our analysis identifies four components needed to represent the diversity of the observed X-ray spectra: (1) an intrinsic power law; (2) a cold obscurer which reprocesses the radiation due to photo-electric absorption, Compton scattering and Fe-K fluorescence; (3) an unabsorbed power law associated with Thomson scattering off ionised clouds; and (4) Compton reflection, most noticeable from a stronger-than-expected Fe-K line. Simpler models, such as a photo-electrically absorbed power law with a Thomson scattering component, are ruled out with decisive evidence (B > 100). We also find that ignoring the Thomson scattering component results in underestimation of the inferred column density, NH, of the obscurer. Regarding the geometry of the obscurer, there is strong evidence against both a completely closed (e.g. sphere), or entirely open (e.g. blob of material along the line of sight), toroidal geometry in favour of an intermediate case. Conclusions: Despite the use of low-count spectra, our methodology is able to draw strong inferences on the geometry of the torus. Simpler models are ruled out in favour of a geometrically extended structure with significant Compton scattering. We confirm the presence of a soft component, possibly associated with Thomson scattering off ionised clouds in the opening angle of the torus. The additional Compton reflection required by data over that predicted by toroidal geometry models, may be a sign of a density gradient in the torus or reflection off the accretion disk. Finally, we release a catalogue of AGN in the CDFS with estimated parameters such as the accretion luminosity in the 2-10 keV band and the column density, NH, of the obscurer. Appendices and Figs. 6, 9-11 are available in electronic form at http://www.aanda.orgCatalogue and software are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/564/A125

Buchner, J.; Georgakakis, A.; Nandra, K.; Hsu, L.; Rangel, C.; Brightman, M.; Merloni, A.; Salvato, M.; Donley, J.; Kocevski, D.

2014-04-01

220

X-Ray Spectral Studies of AGN with the ASCA Satellite  

NASA Technical Reports Server (NTRS)

This project involved the interpretation of Advanced Satellite for Cosmology and Astrophysics (ASCA) observations of Active Galactic Nuclei (AGN), with emphasis on four different aspects of the AGN phenomenon: (1) Absorption by hot gas in blazars: This anomalous absorption was detected in several objects, notably the BL Lacertae (BL Lac) object 1426+428. (2) Separation of blazar and Seyfert components in superluminal radio galaxies and quasars: Both components were found in the radio galaxies samples, but with no clear trend in which dominates. (3) Detection of high energy Compton components in blazars: Both BL Lacs and quasars show hard X-ray spectra that represent the onset of the Compton-scattered gamma-ray component. (4) Correlation of X- and gamma-ray emission in blazars: Several multiwavelength monitoring campaigns showed a correlation between X- and gamma-rays in blazars.

Urry, C. Megan

1999-01-01

221

Probing the X-ray absorber structure in the AGN population through fast spectral variability  

NASA Astrophysics Data System (ADS)

One of the hot topics in modern astrophysics is the variability of absorbers in Seyfert 2 galaxies, suggesting that these structures could be more complex and located at much smaller distances than the conventional obscuring torus. However, in this framework a statistically representative sample of well-studied sources is still missing. We recently started a project aimed at finding more examples of these objects in order to study the physical properties of the X-ray absorber on a larger statistical basis, and to evaluate the frequency of rapid absorption variability among the active galactic nuclei (AGN) population. Here I will present our project: the source selection, based on the exploitation of the BAT AGN catalogue plus the XRT data archive; few preliminary results on particularly significant individual objects; and the future developments, in particular the expectations for Mrk 915, for which new XMM-Newton + NuSTAR observations have been awarded in the last XMM-Newton call.

Ballo, L.; Severgnini, P.; Moretti, A.; Braito, V.; Vignali, C.; Caccianiga, A.; Campana, S.; Della Ceca, R.; Maccacaro, T.; Fanali, R.

2014-07-01

222

Influence of ground-state geometry on carbon monoxide x-ray emission spectral profiles  

NASA Astrophysics Data System (ADS)

Photon excitation x-ray spectator emission dynamics of the core excited carbon monoxide molecule has been studied using ab initio multiconfiguration self-consistent field calculations and a modified two-step absorption-followed-by-emission approach. The core excitations of the CO molecule and the core ionizations of the 0953-4075/31/16/006/img1 species have been considered as the precursor steps for producing the same decaying electronic states of CO. The purpose of this study is to illustrate the influence of the absorption process, using target species with different ground electronic state geometries, on the de-excitation spectra. Nuclear dynamical effects of the decaying processes of carbon and oxygen core excited states of CO to the singlet low-lying excited (final) states of 0953-4075/31/16/006/img2 and 0953-4075/31/16/006/img3 have been studied. Vibrational envelopes of the decay spectra of CO are simulated.

Wang, Feng; Larkins, Frank P.

1998-08-01

223

A novel single-shot, spectrally resolved x-ray imaging technique of ICF relevant plasmas  

NASA Astrophysics Data System (ADS)

A new diagnostic tool has recently been developed, which allows to get 2D images of X-ray sources with simultaneous energy encoded information. This is achieved by using a pinhole camera scheme in which a CCD camera, forced to operate in the single-photon regime, is used as a detector. The use of this method, initially limited to a single pinhole, multi-shot basis, has recently been extended to single-shot experiments typical of large scale installations using custom pinhole arrays of sub-10?m diameter. Preliminary tests have been carried out at the PALS facility and the diagnostics has been successfully employed in a PW environment in a recent experiment at RAL. The details of the method as well as some results from such recent experiments will be given.

Labate, L.; Cecchetti, C. A.; Ciricosta, O.; Köster, P.; Levato, T.; Gizzi, L. A.

2011-06-01

224

Laboratory Data for X-Ray Astronomy  

NASA Technical Reports Server (NTRS)

Laboratory facilities have made great strides in producing large sets of reliable data for X-ray astronomy, which include ionization and recombination cross sections needed for charge balance calculations as well as the atomic data needed for interpreting X-ray line formation. We discuss data from the new generation sources and pay special attention to the LLNL electron beam ion trap experiment, which is unique in its ability to provide direct laboratory access to spectral data under precisely controlled conditions that simulate those found in many astrophysical plasmas. Examples of spectral data obtained in the 1-160 A wavelength range are given illustrating the type of laboratory X-ray data produced in support of such missions as Chandra, X-Ray Multi-Mirror telescope (XMM), Advanced Satellite for Cosmology and Astrophysics (ASCA) and Extreme Ultraviolet Explorer Satellite (EUVE).

Beiersdorfer, P.; Brown, G. V.; Chen, H.; Gu, M.-F.; Kahn, S. M.; Lepson, J. K.; Savin, D. W.; Utter, S. B.

2000-01-01

225

Multiple-view spectrally resolved x-ray imaging observations of polar-direct-drive implosions on OMEGA  

NASA Astrophysics Data System (ADS)

We present spatially, temporally, and spectrally resolved narrow- and broad-band x-ray images of polar-direct-drive (PDD) implosions on OMEGA. These self-emission images were obtained during the deceleration phase and bang time using several multiple monochromatic x-ray imaging instruments fielded along two or three quasi-orthogonal lines-of-sight, including equatorial and polar views. The instruments recorded images based on K-shell lines from a titanium tracer located in the shell as well as continuum emission. These observations constitute the first such data obtained for PDD implosions. The image data show features attributed to laser imprinting and zero-order hydrodynamics. Equatorial-view images show a "double bun" structure that is consistent with synthetic images obtained from post-processing 2D and 3D radiation-hydrodynamic simulations of the experiment. Polar-view images show a pentagonal, petal pattern that correlates with the PDD laser illumination used on OMEGA, thus revealing a 3D aspect of PDD OMEGA implosions not previously observed. Differences are noted with respect to a PDD experiment performed at National Ignition Facility.

Mancini, R. C.; Johns, H. M.; Joshi, T.; Mayes, D.; Nagayama, T.; Hsu, S. C.; Baumgaertel, J. A.; Cobble, J.; Krasheninnikova, N. S.; Bradley, P. A.; Hakel, P.; Murphy, T. J.; Schmitt, M. J.; Shah, R. C.; Tregillis, I. L.; Wysocki, F. J.

2014-12-01

226

X-ray spectral evolution of Her X-1 in a low state and the following short high state  

NASA Astrophysics Data System (ADS)

We analysed spectral variations of ~8.5-d long Rossi X-ray Timing Explorer (RXTE) monitoring observations of Her X-1 in 2001 December. This set of observations enables, for the first time, frequent continuous monitoring (111 pointings in ~8.5 d) of the source with RXTE including a ~1.7-d-long low state part and the following ~6.8-d-long short high state part. We used an absorbed power-law model with an iron line energy complex modelled as a Gaussian to fit both the 3-60 keV Proportional Counter Array-High Energy X-ray Timing Experiment (PCA-HEXTE) overall short high state spectrum and 3-20 keV individual PCA spectra. An additional partial cold absorber model was used for both cases. Using 3-20 keV individual PCA spectra, absorption in anomalous dips (ADs) and pre-eclipse dips (PDs) in the short high state was compared. Decreasing the ratio of unabsorbed to absorbed flux with increasing unabsorbed flux in ADs and PDs was interpreted as evidence of the fact that the regions causing opaque obscuration and soft absorption are not geometrically far away from each other. Higher iron line peak energies in the low state and the short high state (~6.6-6.9 keV) were interpreted as a clue of the presence of iron line components other than the K? emission line.

?nam, S?tk? Ca?da?; Baykal, Altan

2005-08-01

227

Absolute radiant power measurement for the Au M lines of laser-plasma using a calibrated broadband soft X-ray spectrometer with flat-spectral response.  

PubMed

CEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV < photon energy < 5 keV) use only a filter and a coaxial detector. A further improvement of DMX consists in flat-response X-ray channels for a precise absolute measurement of the photon flux in the photon energy range from 0.1 keV to 6 keV. Such channels are equipped with a filter, a Multilayer Mirror (MLM), and a coaxial detector. We present as an example the development of channel for the gold M emission lines in the photon energy range from 2 keV to 4 keV which has been successfully used on the OMEGA laser facility. The results of the radiant power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods. PMID:24517761

Troussel, Ph; Villette, B; Emprin, B; Oudot, G; Tassin, V; Bridou, F; Delmotte, F; Krumrey, M

2014-01-01

228

Absolute radiant power measurement for the Au M lines of laser-plasma using a calibrated broadband soft X-ray spectrometer with flat-spectral response  

NASA Astrophysics Data System (ADS)

CEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV < photon energy < 5 keV) use only a filter and a coaxial detector. A further improvement of DMX consists in flat-response X-ray channels for a precise absolute measurement of the photon flux in the photon energy range from 0.1 keV to 6 keV. Such channels are equipped with a filter, a Multilayer Mirror (MLM), and a coaxial detector. We present as an example the development of channel for the gold M emission lines in the photon energy range from 2 keV to 4 keV which has been successfully used on the OMEGA laser facility. The results of the radiant power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods.

Troussel, Ph.; Villette, B.; Emprin, B.; Oudot, G.; Tassin, V.; Bridou, F.; Delmotte, F.; Krumrey, M.

2014-01-01

229

Absolute radiant power measurement for the Au M lines of laser-plasma using a calibrated broadband soft X-ray spectrometer with flat-spectral response  

SciTech Connect

CEA implemented an absolutely calibrated broadband soft X-ray spectrometer called DMX on the Omega laser facility at the Laboratory for Laser Energetics (LLE) in 1999 to measure radiant power and spectral distribution of the radiation of the Au plasma. The DMX spectrometer is composed of 20 channels covering the spectral range from 50 eV to 20 keV. The channels for energies below 1.5 keV combine a mirror and a filter with a coaxial photo-emissive detector. For the channels above 5 keV the photoemissive detector is replaced by a conductive detector. The intermediate energy channels (1.5 keV < photon energy < 5 keV) use only a filter and a coaxial detector. A further improvement of DMX consists in flat-response X-ray channels for a precise absolute measurement of the photon flux in the photon energy range from 0.1 keV to 6 keV. Such channels are equipped with a filter, a Multilayer Mirror (MLM), and a coaxial detector. We present as an example the development of channel for the gold M emission lines in the photon energy range from 2 keV to 4 keV which has been successfully used on the OMEGA laser facility. The results of the radiant power measurements with the new MLM channel and with the usual channel composed of a thin titanium filter and a coaxial detector (without mirror) are compared. All elements of the channel have been calibrated in the laboratory of the Physikalisch-Technische Bundesanstalt, Germany's National Metrology Institute, at the synchrotron radiation facility BESSY II in Berlin using dedicated well established and validated methods.

Troussel, Ph.; Villette, B.; Oudot, G.; Tassin, V. [CEA/DAM/DIF, Bruyères le Châtel, 91297 Arpajon (France)] [CEA/DAM/DIF, Bruyères le Châtel, 91297 Arpajon (France); Emprin, B. [CEA/DAM/DIF, Bruyères le Châtel, 91297 Arpajon (France) [CEA/DAM/DIF, Bruyères le Châtel, 91297 Arpajon (France); Laboratoire Charles Fabry, Institut d’Optique, CNRS, University Paris-Sud, 2, Avenue Augustin Fresnel, RD128, 91127 Palaiseau Cedex (France); Bridou, F.; Delmotte, F. [Laboratoire Charles Fabry, Institut d’Optique, CNRS, University Paris-Sud, 2, Avenue Augustin Fresnel, RD128, 91127 Palaiseau Cedex (France)] [Laboratoire Charles Fabry, Institut d’Optique, CNRS, University Paris-Sud, 2, Avenue Augustin Fresnel, RD128, 91127 Palaiseau Cedex (France); Krumrey, M. [Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin (Germany)] [Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587 Berlin (Germany)

2014-01-15

230

Broadband Spectral Modeling of NGC 253 from Hard X-rays to TeV Gamma Rays  

NASA Astrophysics Data System (ADS)

An exciting result from Fermi is the detection of star-forming galaxies at GeV energies, but the relative contributions of various radiative processes to the gamma-ray signal remain uncertain. NuSTAR observations of NGC 253 in the hard X-ray band (10-30 keV) enable the most sensitive search to date for diffuse inverse Compton emission in that bandpass, which in turn will constrain the role of hadronic and leptonic interactions in producing the GeV emission. We present the latest results from detailed broadband spectral modeling of the nearby starburst galaxy NGC 253 from keV to TeV energies in light of new observations from NuSTAR.

Venters, Tonia M.; Wik, Daniel R.; Lehmer, Bret; Hornschemeier, Ann E.; Yukita, Mihoko; Ptak, Andrew; Zezas, Andreas; Antoniou, Vallia; Argo, Megan; Bechtol, Keith; Boggs, Steven E.; Christensen, Finn; Craig, William W.; Hailey, Charles James; Harrison, Fiona; Krivonos, Roman; Maccarone, Thomas J.; Stern, Daniel; Zhang, William

2015-01-01

231

CANDIDATE X-RAY-EMITTING OB STARS IN THE CARINA NEBULA IDENTIFIED VIA INFRARED SPECTRAL ENERGY DISTRIBUTIONS  

SciTech Connect

We report the results of a new survey of massive, OB stars throughout the Carina Nebula using the X-ray point source catalog provided by the Chandra Carina Complex Project (CCCP) in conjunction with infrared (IR) photometry from the Two Micron All-Sky Survey and the Spitzer Space Telescope Vela-Carina survey. Mid-IR photometry is relatively unaffected by extinction, hence it provides strong constraints on the luminosities of OB stars, assuming that their association with the Carina Nebula, and hence their distance, is confirmed. We fit model stellar atmospheres to the optical (UBV) and IR spectral energy distributions (SEDs) of 182 OB stars with known spectral types and measure the bolometric luminosity and extinction for each star. We find that the extinction law measured toward the OB stars has two components: A{sub V} = 1-1.5 mag produced by foreground dust with a ratio of total-to-selective absorption R{sub V} = 3.1 plus a contribution from local dust with R{sub V} > 4.0 in the Carina molecular clouds that increases as A{sub V} increases. Using X-ray emission as a strong indicator of association with Carina, we identify 94 candidate OB stars with L{sub bol} {approx}> 10{sup 4} L{sub sun} by fitting their IR SEDs. If the candidate OB stars are eventually confirmed by follow-up spectroscopic observations, the number of cataloged OB stars in the Carina Nebula will increase by {approx}50%. Correcting for incompleteness due to OB stars falling below the L{sub bol} cutoff or the CCCP detection limit, these results potentially double the size of the young massive stellar population.

Povich, Matthew S.; Townsley, Leisa K.; Broos, Patrick S.; Getman, Konstantin V. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Gagne, Marc [Department of Geology and Astronomy, West Chester University, West Chester, PA 19383 (United States); Babler, Brian L.; Meade, Marilyn R.; Townsend, Richard H. D. [Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53706 (United States); Indebetouw, Remy; Majewski, Steven R. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Robitaille, Thomas P., E-mail: povich@astro.psu.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2011-05-01

232

Electromagnetic-field distribution measurements in the soft x-ray range: full characterization of a soft x-ray laser beam.  

PubMed

We report direct measurement of the electromagnetic-field spatial distribution in a neonlike Ar capillary discharge-driven soft x-ray laser beam. The wave front was fully characterized in a single shot using a Shack-Hartmann diffractive optics sensor. The wave front was observed to be dependent on the discharge pressure and capillary length, as a result of beam refraction variations in the capillary plasma. The results predict approximately 70% of the laser beam energy can be focused into an area 4 times the size of the diffraction-limited spot, reaching intensities of approximately 4 x 10(13) W/cm(2). PMID:12005683

Le Pape, S; Zeitoun, Ph; Idir, M; Dhez, P; Rocca, J J; François, M

2002-05-01

233

A COMPREHENSIVE SPECTRAL ANALYSIS OF THE X-RAY PULSAR 4U 1907+09 FROM TWO OBSERVATIONS WITH THE SUZAKU X-RAY OBSERVATORY  

SciTech Connect

We present results from two observations of the wind-accreting X-ray pulsar 4U 1907+09 using the Suzaku Observatory. The broadband time-averaged spectrum allows us to examine the continuum emission of the source and the cyclotron resonance scattering feature at approx19 keV. Additionally, using the narrow CCD response of Suzaku near 6 keV allows us to study in detail the Fe K bandpass and to quantify the Fe Kbeta line for this source for the first time. The source is absorbed by fully covering material along the line of sight with a column density of N{sub H} approx 2 x 10{sup 22} cm{sup -2}, consistent with a wind-accreting geometry, and a high Fe abundance (approx3-4 times solar). Time- and phase-resolved analyses allow us to study variations in the source spectrum. In particular, dips found in the 2006 observation which are consistent with earlier observations occur in the hard X-ray bandpass, implying a variation of the whole continuum rather than occultation by intervening material, while a dip near the end of the 2007 observation occurs mainly in the lower energies implying an increase in N{sub H} along the line of sight, perhaps indicating clumpiness in the stellar wind.

Rivers, Elizabeth; Markowitz, Alex; Suchy, Slawomir; Rothschild, Richard [Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0424 (United States); Pottschmidt, Katja [CRESST and NASA Goddard Space Flight Center, Astrophysics Science Division, Code 661, Greenbelt, MD 20771 (United States); Roth, Stefanie; Barragan, Laura; Fuerst, Felix; Kreykenbohm, Ingo; Wilms, Joern, E-mail: erivers@ucsd.ed [Dr. Karl-Remeis-Sternwarte and Erlangen Centre for Astroparticle Physics, Sternwartstr. 7, 96049 Bamberg (Germany)

2010-01-20

234

A Comprehensive Spectral Analysis of the X-Ray Pulsar 4U 1907+09 from Two Observations with the Suzaku X-Ray Observatory  

NASA Technical Reports Server (NTRS)

We present results from two observations of the wind-accreting X-ray pulsar 4U 1907+09 using the Suzaku observatory, The broadband time-averaged spectrum allows us to examine the continuum emission of the source and the cyclotron resonance scattering feature at approx. 19 keV. Additionally, using the narrow CCD response of Suzaku near 6 ke V allows us to study in detail the Fe K bandpass and to quantify the Fe Kp line for this source for the first time. The source is absorbed by fully-covering material along the line of sight with a column density of N(sub H) approx. 2 x 10(exp 22)/sq cm, consistent with a wind accreting geometry, and a high Fe abundance (approx. 3 - 4 x solar). Time and phase-resolved analyses allow us to study variations in the source spectrum. In particular, dips found in the 2006 observation which are consistent with earlier observations occur in the hard X-ray bandpass, implying a variation of the whole continuum rather than occultation by intervening material, while a dip near the end of the 2007 observation occurs mainly in the lower energies implying an increase in NH along the line of sight, perhaps indicating clumpiness in the stellar wind

Rivers, Elizabeth; Markowitz, Alex; Pottschmidt, Katja; Roth, Stefanie; Barragan, Laura; Furst, Felix; Suchy, Slawomir; Kreykenbohm, Ingo; Wilms, Jorn; Rothschild, Richard

2009-01-01

235

Task-based weights for photon counting spectral x-ray imaging  

SciTech Connect

Purpose: To develop a framework for taking the spatial frequency composition of an imaging task into account when determining optimal bin weight factors for photon counting energy sensitive x-ray systems. A second purpose of the investigation is to evaluate the possible improvement compared to using pixel based weights. Methods: The Fourier based approach of imaging performance and detectability index d' is applied to pulse height discriminating photon counting systems. The dependency of d' on the bin weight factors is made explicit, taking into account both differences in signal and noise transfer characteristics across bins and the spatial frequency dependency of interbin correlations from reabsorbed scatter. Using a simplified model of a specific silicon detector, d' values for a high and a low frequency imaging task are determined for optimal weights and compared to pixel based weights. Results: The method successfully identifies bins where a large point spread function degrades detection of high spatial frequency targets. The method is also successful in determining how to downweigh highly correlated bins. Quantitative predictions for the simplified silicon detector model indicate that improvements in the detectability index when applying task-based weights instead of pixel based weights are small for high frequency targets, but could be in excess of 10% for low frequency tasks where scatter-induced correlation otherwise degrade detectability. Conclusions: The proposed method makes the spatial frequency dependency of complex correlation structures between bins and their effect on the system detective quantum efficiency easier to analyze and allows optimizing bin weights for given imaging tasks. A potential increase in detectability of double digit percents in silicon detector systems operated at typical CT energies (100 kVp) merits further evaluation on a real system. The method is noted to be of higher relevance for silicon detectors than for cadmium (zink) telluride detectors.

Bornefalk, Hans [Department of Physics, Royal Institute of Technology, SE-106 91 Stockholm (Sweden)

2011-11-15

236

Hard x-ray spectra from laser-generated plasmas recorded by the HENEX spectrometer in the 1 keV40 keV energy range  

Microsoft Academic Search

Hard x-ray spectra were recorded by the High Energy Electronic X-Ray (HENEX) spectrometer from a variety of targets irradiated by the Omega laser at the Laboratory for Laser Energetics. The HENEX spectrometer utilizes four reflection crystals covering the 1 keV to 20 keV energy range and one quartz(10-11) transmission crystal (Laue geometry) covering the 11 keV to 40 keV range.

J. F. Seely; C. A. Back; C. Constantin; R. W. Lee; H.-K. Chung; L. T. Hudson; C. I. Szabo; A. Henins; G. E. Holland; R. Atkin

2005-01-01

237

The Observed Spectral Evolution of Solar Flare Hard X-Ray Emission  

NASA Technical Reports Server (NTRS)

The spectral evolution of flare emission may be characterized using color-color diagrams (CCDs), a technique which has been widely employed by the astrophysics community, but not yet by the solar flare community. CCDs are constructed for a sample of flares observed simultaneously by CGRO/BATSE and Yohkoh/HXT. It is found that flare spectral evolution follows one of only a few patterns, which generally evolve differently than the soft-hard-soft pattern put forth as the norm in previous work. The implications for the nature of flare energy release and acceleration/propagation models are discussed

Newton, Elizabeth; Giblin, Timothy

1999-01-01

238

Evolution of long-range myofibrillar crystallinity in insect flight muscle as examined by X-ray cryomicrodiffraction  

PubMed Central

Insect flight muscle is known for its crystal-quality regularity of contractile protein arrangement within a sarcomere. We have previously shown by X-ray microdiffraction that the crystal-quality regularity in bumble-bee flight muscle is not confined within a sarcomere, but extends over the entire length of a myofibril (>1000 sarcomeres connected in series). Because of this, the whole myofibril may be regarded as a millimetre-long, natural single protein crystal. Using bright X-ray beams from a synchrotron radiation source, we examined how this long-range crystallinity has evolved among winged insects. We analysed >4600 microdiffraction patterns of quick-frozen myofibrils from 50 insect species, covering all the major winged insect orders. The results show that the occurrence of such long-range crystallinity largely coincides with insect orders with asynchronous muscle operation. However, a few of the more skilled fliers among lower-order insects apparently have developed various degrees of structural regularity, suggesting that the demand for skilful flight has driven the lattice structure towards increased regularity. PMID:16608686

Iwamoto, Hiroyuki; Inoue, Katsuaki; Yagi, Naoto

2005-01-01

239

Easy spectrally tunable highly efficient X-ray backlighting schemes based on spherically bent crystals  

Microsoft Academic Search

New easy spectrally tunable backlighting schemes based on a spherically bent crystal are considered. Contrary to traditional backlighting scheme, in which the investigated objects should be placed between the backlighter and the crystal, for the considered schemes an object is placed downstream of the crystal, before the tangential or after the sagittal focus and an image of the object is

T. Pikuz; A. Faenov; I. Skobelev; A. Magunov; L. Labate; L. A. Gizzi; M. Galimberti; A. Zigler; G. Baldacchini; F. Flora; S. Bollanti; P. di Lazzaro; D. Murra; G. Tomassetti; A. Ritucci; A. Reale; L. Reale; M. Francucci; S. Martelluci; G. Petrocelli

2004-01-01

240

X-ray spectral properties of Seyfert 2s observed with BeppoSAX  

NASA Astrophysics Data System (ADS)

We present the results of a homogeneous analysis of BeppoSAX observations of 19 bright Compton-thin Seyfert 2s. Using the wide spectral coverage of BeppoSAX it is possible to determine the single spectral components with unprecedented precision. We find that the intrinsic emission of Seyfert 2s is well reproduced by a power law with a photon index ?=1.79+/-0.01, and a dispersion ?=0.23. A reflection component is present in most spectra. We discuss these results in the view of the unified model, and we show a stacked spectrum obtained adding up the 1-200 keV spectra of all the sources of the sample. Also INAF - Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze, Italy

Risaliti, G.

2004-06-01

241

Is M82 X-1 Really An Intermediate-Mass Black Hole? X-ray Spectral and Timing Evidence  

E-print Network

Ultra-luminous X-ray sources (ULXs) with apparent luminosities up to 100's of times the Eddington luminosity for a neutron star have been discovered in external galaxies. The existence of intermediate mass black holes has been proposed to explain these sources. We present evidence for an intermediate-mass black hole in the ULX M82 X-1 based on the spectral features and timing (QPO) properties of the X-radiation from this source. We revisited XMM Newton and RXTE data for M82 X-1 obtained in 2001 and 1997 for XMM and RXTE respectively. We show for these observations that the source is either in transition or in a high/soft state with photon spectral indices 2.1 and 2.7 respectively. We confirm the early determination of the QPO frequency ~ 55 mHz in this source by Strohmayer & Mushotzky and identify this as the low frequency QPO for the source. We apply a new method to determine the BH mass of M82 X-1. The method uses the index-QPO low frequency correlation that has been recently been established in galactic black hole candidates GRS 1915+105, XTE J1550-564, 4U 1630-47 and others. Using scaling arguments and the correlation derived from consideration of galactic BHs, we conclude that M82 X-1 is an intermediate BH with a mass of the order of 1000 solar masses.

Ralph Fiorito; Lev Titarchuk

2004-09-16

242

Absolute spectral characterization of silicon barrier diode: Application to soft X-ray fusion diagnostics at Tore Supra  

NASA Astrophysics Data System (ADS)

This paper presents an experimental protocol for absolute calibration of photo-detectors. Spectral characterization is achieved by a methodology that unlike the usual line emissions-based method, hinges on the Bremsstrahlung radiation of a Soft X-Ray (SXR) tube only. Although the proposed methodology can be applied virtually to any detector, the application presented in this paper is based on Tore Supra's SXR diagnostics, which uses Silicon Surface Barrier Diodes. The spectral response of these n-p junctions had previously been estimated on a purely empirical basis. This time, a series of second-order effects, like the spatial distribution of the source radiated power or multi-channel analyser non linearity, are taken into account to achieve accurate measurements. Consequently, a parameterised physical model is fitted to experimental results and the existence of an unexpected dead layer (at least 5 ?m thick) is evidenced. This contribution also echoes a more general on-going effort in favour of long-term quality of passive radiation measurements on Tokamaks.

Vezinet, D.; Mazon, D.; Malard, P.

2013-07-01

243

The X-ray spectral properties of the bulge of M31  

NASA Technical Reports Server (NTRS)

The results of a spectral analysis of the Einstein observations of the bulge of M31 are reported. The data can be fitted with a hard thermal spectrum with characteristic temperature kT of about 6-13 keV (at 90 percent confidence). No intrinsic absorption above the galactic value of N(H) is required. These results are in agreement with the presence in the bulge of M31 of a population of low-mass binary sources similar to those of the Milky Way.

Fabbiano, G.; Trinchieri, G.; Van Speybroeck, L. S.

1987-01-01

244

Non-invasive material discrimination using spectral x-ray radiography  

SciTech Connect

Current radiographic methods are limited in their ability to determine the presence of nuclear materials in containers or composite objects. A central problem is the inability to distinguish the attenuation pattern of high-density metals from those with a larger greater thickness of a less- dense material. Here we show that spectrally sensitive detectors can be used to discriminate plutonium from multiple layers of other materials using a single-view radiograph. An inverse algorithm with adaptive regularization is used. The algorithm can determine the presence of plutonium in simulated radiographs with a mass resolution per unit area of at least 0.07 g•cm^-2.

Gilbert, Andrew J.; McDonald, Benjamin S.; Robinson, Sean M.; Jarman, Kenneth D.; White, Timothy A.; Deinert, Mark

2014-04-21

245

Non-invasive material discrimination using spectral x-ray radiography  

SciTech Connect

Current radiographic methods are limited in their ability to determine the presence of nuclear materials in containers or composite objects. A central problem is the inability to distinguish the attenuation pattern of high-density metals from those with a greater thickness of a less dense material. Here, we show that spectrally sensitive detectors can be used to discriminate plutonium from multiple layers of other materials using a single-view radiograph. An inverse algorithm with adaptive regularization is used. The algorithm can determine the presence of plutonium in simulated radiographs with a mass resolution per unit area of at least 0.07?g?cm{sup ?2}.

Gilbert, Andrew J. [Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78715-0162 (United States); Pacific Northwest National Laboratory, Richland, Washington 99354-1793 (United States); McDonald, Benjamin S.; Robinson, Sean M.; Jarman, Ken D.; White, Tim A. [Pacific Northwest National Laboratory, Richland, Washington 99354-1793 (United States); Deinert, Mark R., E-mail: mdeinert@utexas.edu [Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78715-0162 (United States)

2014-04-21

246

GRBs and Lobster Eye X-Ray Telescopes  

NASA Astrophysics Data System (ADS)

A large majority of GRBs exhibit X-ray emission. In addition, a dedicated separate group of GRB, the XRFs, exists which emission dominates in the X-ray spectral range. And the third group of GRB related objects (yet hypothetical) are the group of off-axis observed GRBs (orphan afterglows). These facts justify the consideration of an independent experiment for monitoring, detection and analyses of GRBs and others fast X-ray transients in X-rays. We will present and discuss such experiment based on wide-field X-ray telescopes of Lobster Eye type. We show that the wide field and fine sensitivity of Lobster Eye X-ray All-Sky Monitor make such instruments important tools in study of GRBs.

Hudec, R.; Pina, L.; Marsikova, V.; Inneman, A.

2013-07-01

247

A digital x-ray tomosynthesis coupled near infrared spectral tomography system for dual-modality breast imaging  

PubMed Central

A Near Infrared Spectral Tomography (NIRST) system has been developed and integrated into a commercial Digital Breast Tomosynthesis (DBT) scanner to allow structural and functional imaging of breast in vivo. The NIRST instrument uses an 8-wavelength continuous wave (CW) laser-based scanning source assembly and a 75-element silicon photodiode solid-state detector panel to produce dense spectral and spatial projection data from which spectrally constrained 3D tomographic images of tissue chromophores are produced. Integration of the optical imaging system into the DBT scanner allows direct co-registration of the optical and DBT images, while also facilitating the synergistic use of x-ray contrast as anatomical priors in optical image reconstruction. Currently, the total scan time for a combined NIRST-DBT exam is ~50s with data collection from 8 wavelengths in the optical scan requiring ~42s to complete. The system was tested in breast simulating phantoms constructed using intralipid and blood in an agarose matrix with a 3 cm x 2 cm cylindrical inclusion at 1 cm depth from the surface. Diffuse image reconstruction of total hemoglobin (HbT) concentration resulted in accurate recovery of the lateral size and position of the inclusion to within 6% and 8%, respectively. Use of DBT structural priors in the NIRST reconstruction process improved the quantitative accuracy of the HbT recovery, and led to linear changes in imaged versus actual contrast, underscoring the advantages of dual-modality optical imaging approaches. The quantitative accuracy of the system can be further improved with independent measurements of scattering properties through integration of frequency or time domain data. PMID:23038553

Krishnaswamy, Venkataramanan; Michaelsen, Kelly E.; Pogue, Brian W.; Poplack, Steven P.; Shaw, Ian; Defrietas, Ken; Brooks, Ken; Paulsen, Keith D.

2012-01-01

248

Design and performance of a versatile curved-crystal spectrometer for high-resolution spectroscopy in the tender x-ray range  

SciTech Connect

A complete in-vacuum curved-crystal x-ray emission spectrometer in Johansson geometry has been constructed for a 2-6 keV energy range with sub natural line-width energy resolution. The spectrometer is designed to measure x-ray emission induced by photon and charged particle impact on solid and gaseous targets. It works with a relatively large x-ray source placed inside the Rowland circle and employs position sensitive detection of diffracted x-rays. Its compact modular design enables fast and easy installation at a synchrotron or particle accelerator beamline. The paper presents main characteristics of the spectrometer and illustrates its capabilities by showing few selected experimental examples.

Kavcic, M.; Budnar, M.; Muehleisen, A.; Gasser, F.; Zitnik, M.; Bucar, K.; Bohinc, R. [J. Stefan Institute, Jamova 39, SI-1001, Ljubljana (Slovenia)

2012-03-15

249

Relative x-ray collection efficiency, spatial resolution, and spectral resolution of spherically-bent quartz, mica, germanium, and pyrolytic graphite crystals  

NASA Astrophysics Data System (ADS)

The relative x-ray collection efficiency, spatial resolution, and spectral resolution of spherically-bent quartz, mica, and germanium crystals were compared with cylindrically and spherically-bent highly oriented pyrolytic graphite (HOPG) and spherically-bent highly annealed pyrolytic graphite (HAPG) mosaic crystals. The crystals were characterized using Mn-K-?1 (5898.8 eV) and Mn-K-?2 (5887.6 eV) x-rays generated from a Manson x-ray source. The HOPG and HAPG crystals had about (10-100)× higher x-ray collection efficiency than the quartz, mica, and germanium crystals. However, good spatial resolutions were obtained with the quartz (49 ?m), mica (61 ?m), and germanium (275 ?m) crystals, while the HOPG and HAPG crystals provided no useful spatial resolving power. Deconvolution of the spectral broadening due to the Mn-K-?1 intrinsic width (2.33 eV), source size (320 ?m), and image plate detector resolution (63 ?m) demonstrated the spectral resolutions (E/?E) of the quartz (3800-6600), mica (4600), and germanium (3400-4500) crystals to be considerably higher than that of the HOPG (1200-2400) and HAPG (2500) crystals.

Ao, T.; Harding, E. C.; Bailey, J. E.; Loisel, G.; Patel, S.; Sinars, D. B.; Mix, L. P.; Wenger, D. F.

2014-09-01

250

X-ray sensor development for magnetospheric research  

NASA Technical Reports Server (NTRS)

The ARPA-301 data on the P78-1 satellite provide information on the long-term X-ray environment; specifically, the distributions in total X-ray intensities and energy spectral parameters and the spatial extents of the X-ray sources. The average X-ray intensity near noontime was found to decrease with increasing local time whereas the opposite trend occurs around midnight. At both of these local times, the average flux increases with increasing level of geomagnetic activity. The distributions in flux are also considered for given local time intervals and these span a large dynamic range. The temporal correlation between the X-ray flux in different local time sectors is found to decrease with increasing difference in local time. The average spectral shapes do not depend significantly upon local time or geomagnetic activity.

Imhof, W. L.

1983-01-01

251

Furan derivatives of substituted phenylthiourea: spectral studies, semi-empirical quantum-chemical calculations and X-ray structure analyses  

NASA Astrophysics Data System (ADS)

Fifty new derivatives of 1-(furan-2-carbonyl)- and 1-(furan-3-carbonyl)-3-phenyl substituted thiourea have been synthesised and identified. Intramolecular hydrogen bonds were investigated in detail, using IR spectroscopy. The three-level Fermi resonance effect in the IR spectra was analysed after deconvolution and band separation. Semi-empirical quantum-chemical calculations (AM1 and PM3) support the results of the IR spectroscopic studies. X-ray single crystal diffraction analyses of four selected compounds, namely 1-(furan-3-carbonyl)-3-(2-trifluoromethyl-phenyl)-thiourea ( 1e), 1-(2-methyl-furan-3-carbonyl)-3-(2-trifluoromethyl-phenyl)-thiourea ( 2e), 1-(2,6-dichloro-phenyl)-3-(2-methyl-furan-3-carbonyl)-thiourea ( 2n) and 1-(4-methoxyphenyl)-3-(3-methyl-2-furan-carbonyl)-thiourea ( 3e), corroborated the molecular and crystal structure of these compounds. Relatively strong intramolecular hydrogen bonds of the N-H⋯O dbnd6 C type as well as intermolecular two-centred and bifurcated three-centred hydrogen bonds were observed, confirming the results of the IR spectral study and the semi-empirical quantum-chemical calculations. A variety of intermolecular interactions, yielding the supramolecular architectures in the four crystalline compounds, are discussed in detail.

Hritzová, Ol'ga; ?ernák, Juraj; Šafa?, Peter; Fr?hlichová, Zdenka; Cs?regh, Ingeborg

2005-05-01

252

High spectral resolution observations of the coronal X-ray emission from the RS CVn binary Sigma Corona Borealis  

NASA Technical Reports Server (NTRS)

The results of high-resolution observations of the RS CVn binary star Rho Cr B are reported. The observations were carried out using the Focal Plane Crystal Spectrometer (FPCS) onboard the Einstein Observatory satellite. A spectral scan in the interval 800-840 eV shows clear evidence of an X-ray emission line at 826 eV identified with 1S(0)-1P(1) transition of Fe XVII. A prominent peak at 1007 eV in the scan band 986-1014 eV was attributed to a blend of lines produced by highly ionized iron. On the basis of the observed fluxes of the lines and the theoretical calculations of Raymond and Smith (1977), best-fit values of corona temperature and volume emission measures of 6.92 (+0.84 or -0.75) x 10 to the 6th K, and 1.74 (+0.55 or -0.69) x 10 to the 35th are derived, respectively. Some implications of the results are briefly discussed.

Agrawal, P. C.; Markert, T. H.; Riegler, G. R.

1985-01-01

253

Syntheses, spectral characterization, single crystal X-ray diffraction and DFT computational studies of novel thiazole derivatives  

NASA Astrophysics Data System (ADS)

A novel thiazole (E)-1-((E)-2-methyl-3-phenylallylidene)-2-(4-phenylthiazole-2-yl)hydrazine 2 and its derivatives 3-8 were synthesized by cyclo condensation of (1E)-1-((E)-2-methyl-3-phenylallylidene)thiosemicarbazide 1 with substituted 2-bromoacetophenones. The synthesized thiazole derivatives were characterized by FT-IR, 1H NMR and 13C NMR analyses. For compound 8 single crystals X-ray diffraction analysis and density functional theory (DFT) calculation were carried out. The compound 8 crystallizes in the monoclinic space group P21/c with a = 7.4601 (3) Å, b = 5.7259 (2) Å, c = 41.0823 (13) Å, ? = 90°, ? = 91.715 (2)° and ? = 90°. The molecular geometrical parameters, frontier molecular orbital energies (HOMO, LUMO), their energy gap (?E), molecular electrostatic potential (MEP) and natural bond orbital (NBO) analysis of the compounds 2 and8 have been calculated by using DFT/B3LYP with 6-311G (d, p) level. In addition, IR frequencies, 1H and 13C NMR chemical shifts of compound 8 were also calculated by using DFT calculations at the same level basis set. The calculated geometrical parameters, IR frequencies, 1H and 13C NMR chemical shifts of the compound 8 were in good agreement with the observed single crystal-XRD data, IR, 1H and 13C NMR spectral values.

Anbazhagan, R.; Sankaran, K. R.

2013-10-01

254

Spectral Analysis in Orbital/Superorbital Phase Space and Hints of Superorbital Variability in the Hard X-Rays of LS I +61°303  

NASA Astrophysics Data System (ADS)

We present an INTEGRAL spectral analysis in the orbital/superorbital phase space of LS I +61°303. A hard X-ray spectrum with no cutoff is observed at all orbital/superorbital phases. The hard X-ray index is found to be uncorrelated with the radio index (non-simultaneously) measured at the same orbital and superorbital phases. In particular, the absence of an X-ray spectrum softening during periods of negative radio index does not favor a simple interpretation of the radio index variations in terms of a microquasar's changes of state. We uncover hints of superorbital variability in the hard X-ray flux, in phase with the superorbital modulation in soft X-rays. An orbital phase drift of the radio peak flux and index along the superorbital period is observed in the radio data. We explore its influence on a previously reported double-peak structure of a radio orbital light curve, and present it as a plausible explanation.

Li, Jian; Torres, Diego F.; Zhang, Shu

2014-04-01

255

Spectral variation in the X-ray pulsar GX 1+4 during a low-flux episode  

NASA Astrophysics Data System (ADS)

The X-ray pulsar GX 1+4 was observed with the RXTE satellite for a total of 51ks between 1996 July 19 and 21. During this period the flux decreased smoothly from an initial mean level of ~6x1036ergs-1 to a minimum of ~4x1035ergs-1 (2-60keV, assuming a source distance of 10kpc) before partially recovering towards the initial level at the end of the observation. BATSE pulse timing measurements indicate that a torque reversal took place approximately 10d after this observation. Both the mean pulse profile and the photon spectrum varied significantly. The observed variation in the source may provide important clues as to the mechanism of torque reversals. The single best-fitting spectral model was based on a component originating from thermal photons with kT0~1keV Comptonized by a plasma of temperature kT~7keV. Both the flux modulation with phase during the brightest interval and the evolution of the mean spectra over the course of the observation are consistent with variations in this model component; with, in addition, a doubling of the column density nH contributing to the mean spectral change. A strong flare of duration <~50s was observed during the interval of minimum flux, with the peak flux ~20 times the mean level. Although beaming effects are likely to mask the true variation in M? thought to give rise to the flare, the timing of a modest increase in flux prior to the flare is consistent with dual episodes of accretion resulting from successive orbits of a locally dense patch of matter in the accretion disc.

Galloway, D. K.; Giles, A. B.; Greenhill, J. G.; Storey, M. C.

2000-02-01

256

Atmosphere of a sunspot based on observations in the x-ray, extreme ultraviolet, optical, and radio ranges  

SciTech Connect

It is shown that the lower chromosphere of an umbra is best described within the framework of a model close to that of Teplitskaya et al. This model can be extended to higher levels using a large temperature gradient, so that Troughly-equal40 000 K and an electron density n/sub e/roughly-equal4x10/sup 10/ cm/sup -3/ are reached at a height zroughly-equal2000 km above the umbral photosphere. These values are defined by the EUV data of the HRTS instrument. At higher levels one must presume the existence of at least two components: The hot component, which occupies ..cap alpha..roughly-equal0.8--0.9 of the total volume, has a narrow transition layer, and the coronal values of Troughly-equal1.8x10/sup 6/ K and n/sub e/roughly-equal5x10/sup 8/ even at a height z = 3000--5000 km. These values are consistent both with the absence of an x-ray emission flux above large sunspots and with the high brightness temperature T/sub b/ = 1.8x10/sup 6/ K of emission in the centimeter range from the same region. This hot coronal matter surrounds the bases of cool loops emerging from the umbra in the form of bundles, and they emit the EUV lines observed at 10/sup 4/< or =T< or =10/sup 6/ K. In the corona the z dependence of all the physical quantities, including ..cap alpha.., over a distance of several thousand kilometers can be taken as weak. Along the axis of a loop T grows slowly, the loops become more horizontal, and at distances and heights of several tens of thousands of kilometers above a flocculus they appear as hot x-ray loops.

Staude, J.; Fuerstenberg, F.; Hildebrandt, J.; Krueger, A.; Jakimiec, J.; Obridko, V.N.; Siarkowski, M.; Sylwester, B.; Sylwester, J.

1984-09-01

257

Explorer Program: X-ray Timing Explorer  

NASA Technical Reports Server (NTRS)

This booklet describes the X-ray Timing Explorer (XTE), one in a series of Explorer missions administered by the National Aeronautics and Space Administration's (NASA) Office of Space Science and managed by the NASA Goddard Space Flight Center (GSFC). The X-ray astronomy observatory is scheduled for launch into low-Earth orbit by Delta 2 expendable launch vehicle in late summer of 1995. The mission is expected to operate for at least 2 years and will carry out in-depth timing and spectral studies of the X-ray sources in the 2 to 200 kilo-electron Volt (keV) range. XTE is intended to study the temporal and broad-band spectral phenomena associated with stellar and galactic systems containing compact objects, including neutron stars, white dwarfs, and black holes.

1995-01-01

258

Combined microstructure x-ray optics  

SciTech Connect

Multilayers are man-made microstructures which vary in depth and are now of sufficient quality to be used as x-ray, soft x-ray and extreme ultraviolet optics. Gratings are man-made in plane microstructures which have been used as optic elements for most of this century. Joining of these two optical microstructures to form combined microstructure optical microstructures to form combined microstructure optical elements has the potential for greatly enhancing both the throughput and the resolution attainable in these spectral ranges. The characteristics of these new optic elements will be presented and compared to experiment with emphasis on the unique properties of these combined microstructures. These results reported are general in nature and not limited to the soft x-ray or extreme ultraviolet spectral domains and also apply to neutrons. 19 refs., 7 figs., 4 tabs.

Barbee, T.W. Jr.

1989-02-01

259

Hard X-ray spectral variability of the brightest Seyfert AGN in the Swift/BAT sample  

NASA Astrophysics Data System (ADS)

Aims: We analyse data from a 58 month long, continuous Swift/Burst Alert Telescope (BAT) series of observations of the five brightest Seyfert galaxies at hard X-rays, to study their flux and spectral variability in the 20-100 keV energy band. The column density in these objects is less than 1024 cm-2, which implies that the Swift/BAT data allow us to study the "true" variability of the central source. Methods: We used 2-day binned light curves in the (20-50) and (50-100) keV bands to estimate their fractional variability amplitude, and the same band 20-day binned light curves to compute hardness ratios and construct "colour-flux" diagrams. We also considered a thermal Comptonization model, together with a reflection component with constant flux, and produced model "colour-flux" diagrams, assuming realistic variations in the model parameter values, which we then compared with the observed diagrams. Results: All objects show significant variations, with an amplitude that is similar to the AGN variability amplitude at energies below 10 keV. We found evidence of an anti-correlation between variability amplitude and black hole mass. The light curves in both bands are well-correlated with each other, with no significant delays on time scales as short as two days. We find that both NGC 4151 and NGC 2110 display no spectral variability, but that there is a significant anti-correlation between hardness ratios and source flux in NGC 4388 (and NGC 4945, IC 4329, to a lesser extent). This "softer when brighter" behaviour is similar to that observed at energies below 10 keV, and cannot be explained if the continuum varies only in flux; the intrinsic shape should also steepen with increasing flux. Conclusions: The detection of significant flux variations indicate that the central source in these objects is intrinsically variable on time scales as short as ~1-2 days. The intrinsic slope of the continuum varies with the flux (at least in NGC 4388). The positive "spectral slope-flux" correlation can be explained if the temperature of the hot corona decreases with increasing flux. The lack of spectral variations in two objects (NGC 4151 and NGC 2110) might indicate that they are in a different "state", as their accretion rate is less than 1% of the Eddington limit (significantly lower than the rate of the other three objects in the sample).

Caballero-Garcia, M. D.; Papadakis, I. E.; Nicastro, F.; Ajello, M.

2012-01-01

260

X-ray timing and spectral observations of galactic black hole candidate XTE J1550-564 during outburst  

NASA Astrophysics Data System (ADS)

The timing and spectral properties of the soft X-ray transient (SXT) and microquasar XTE J1550-564 during outburst are studied, emphasizing observations made by the Unconventional Stellar Aspect (USA) Experiment. USA data show a low-frequency quasi-periodic oscillation (LFQPO) with a centroid frequency that tends to increase with increasing flux and a fractional rms amplitude which is correlated with the USA hardness ratio. Several high- frequency quasi-periodic oscillations (HFQPOs) were detected by RXTE, during periods where the LFQPO is seen to be weakening or not detectable at all. The evolution of the USA hardness ratio with time and source flux is examined. The hardness-intensity diagram shows counterclockwise cyclical evolution and possibly indicates the presence of two independent accretion flows: a geometrically thin, optically thick accretion disk and a hot sub-Keplerian flow. A model for production of the LFQPO in XTE J1550-564 is proposed, assuming that the LFQPO is a result of acoustic oscillations in a hot sub-Keplerian transition layer (TL). Under this acoustic oscillation model (AOM), the TL is an acoustic cavity having an outer boundary at RTL, where R TL ? Rinner, with Rinner being the radius of the accretion disk inner edge. TL resonance is interpreted as a mechanism for the LFQPO and the eigenfrequencies are associated with the LFQPO frequencies, ? LFQPO. This LFQPO mechanism requires the presence of a TL, capable of inverse-Compton scattering, with RTL regulated by a cool Keplerian accretion disk. Support for the AOM is provided by the correlation of the LFQPO percent rms amplitude with the USA hardness ratio, and other correlations and anti-correlations found in the USA, RXTE and BATSE observations. LFQPO data show increasing rms amplitude with increasing high energy flux and increasing ?LFQPO with increasing low energy flux. These observations indicate that ? LFQPO is set by the accretion disk inner edge. The spectrally inferred Rinner is commensurate, showing a decrease with increasing ? LFQPO. Finally, RXTE spectral data indicate that the LFQPO is detectable only when the power law contribution is greater than 20% of the low energy flux, providing evidence that the LFQPO mechanism is dependent on the TL. The AOM is consistent with all of the above observations and it has the ability to predict the approximate value of Rinner. Comparison between spectrally determined Rinner and the AOM measurement of RTL shows good agreement.

Reilly, Kaice Theodore

2003-09-01

261

The x-ray calibration facility of the laser integration line in the 0.9-10 keV range: The high energy x-ray source and some applications  

Microsoft Academic Search

The laser integration line (LIL) located at CEA-CESTA is equipped with x-ray plasma diagnostics using different kinds of x-ray components such as filters, mirrors, crystals, detectors, and cameras. The CEA-DAM of Arpajon is currently developing x-ray calibration methods and carrying out absolute calibration of LIL x-ray photodetectors. To guarantee LIL measurements, detectors such as x-ray cameras must be regularly calibrated

S. Hubert; J. L. Dubois; D. Gontier; G. Lidove; C. Reverdin; G. Soullié; P. Stemmler; B. Villette

2010-01-01

262

Testing MOND over a Wide Acceleration Range in X-Ray Ellipticals  

NASA Astrophysics Data System (ADS)

The gravitational fields of two isolated ellipticals, NGC 720 and NGC 1521, have been recently measured to very large galactic radii (˜100 and ˜200kpc), assuming hydrostatic balance of the hot gas enshrouding them. They afford, for the first time to my knowledge, testing modified Newtonian dynamics (MOND) in ellipticals with force and quality that, arguably, approach those of rotation-curve tests in disk galaxies. In the context of MOND, it is noteworthy that the measured accelerations span a wide range, from more than 10a0 to about 0.1a0, unprecedented in individual ellipticals. I find that MOND predicts correctly the measured dynamical mass runs (apart from a possible minor tension in the inner few kpc of NGC 720, which might be due to departure from hydrostatic equilibrium): The predicted mass discrepancy increases outward from none near the center, to ˜10 at the outermost radii. The implications for the MOND-versus-dark-matter controversy go far beyond the simple fact of two more galaxies conforming to MOND.

Milgrom, Mordehai

2012-09-01

263

Testing MOND over a wide acceleration range in x-ray ellipticals.  

PubMed

The gravitational fields of two isolated ellipticals, NGC 720 and NGC 1521, have been recently measured to very large galactic radii (~100 and ~200 kpc), assuming hydrostatic balance of the hot gas enshrouding them. They afford, for the first time to my knowledge, testing modified Newtonian dynamics (MOND) in ellipticals with force and quality that, arguably, approach those of rotation-curve tests in disk galaxies. In the context of MOND, it is noteworthy that the measured accelerations span a wide range, from more than 10a(0) to about 0.1a(0), unprecedented in individual ellipticals. I find that MOND predicts correctly the measured dynamical mass runs (apart from a possible minor tension in the inner few kpc of NGC 720, which might be due to departure from hydrostatic equilibrium): The predicted mass discrepancy increases outward from none near the center, to ~10 at the outermost radii. The implications for the MOND-versus-dark-matter controversy go far beyond the simple fact of two more galaxies conforming to MOND. PMID:23030078

Milgrom, Mordehai

2012-09-28

264

Spectral Softening Between Outburst and Quiescence In The Neutron Star Low-Mass X-Ray Binary SAX J1750.8-2900  

E-print Network

Tracking the spectral evolution of transiently accreting neutron stars between outburst and quiescence probes relatively poorly understood accretion regimes. Such studies are challenging because they require frequent monitoring of sources with luminosities below the thresholds of current all-sky X-ray monitors. We present the analysis of over 30 observations of the neutron star low-mass X-ray binary SAX J1750.8-2900 taken across four years with the X-ray telescope aboard Swift. We find spectral softening with decreasing luminosity both on long ($\\sim$1 year) and short ($\\sim$days to week) timescales. As the luminosity decreases from $4\\times10^{36}$ erg s$^{-1}$ to $ \\sim1\\times10^{35} $ erg s$^{-1}$ (0.5-10 keV), the power law photon index increases from from 1.4 to 2.9. Although not statistically required, our spectral fits allow an additional soft component that displays a decreasing temperature as the luminosity decreases from $4 \\times 10^{36} $ to $6 \\times 10^{34}$ erg s$^{-1}$. Spectral softening exhi...

Allen, Jessamyn L; Homan, Jeroen; Chakrabarty, Deepto

2015-01-01

265

SAXES, a high resolution spectrometer for resonant x-ray emission in the 400-1600 eV energy range  

SciTech Connect

We present a 5 m long spectrometer for soft x rays to be used at a synchrotron radiation beamline for resonant x-ray emission spectroscopy and resonant inelastic x-ray scattering in the 400-1600 eV energy range. It is based on a variable line spacing spherical grating (average groove density of 3200 mm{sup -1}, R=58.55 m) and a charge coupled device two dimensional detector. With an x-ray spot on the sample of 10 {mu}m, the targeted resolving power is higher than 10 000 at all energies below 1100 eV and better than 7000 at 1500 eV. The off-line tests made with Al and Mg K{alpha}{sub 1,2} fluorescence emissions indicate that the spectrometer can actually work at 12 000 and 17 000 resolving power at the L{sub 3} edges of Cu (930 eV) and of Ti (470 eV), respectively. SAXES (superadvanced x-ray emission spectrometer) is mounted on a rotating platform allowing to vary the scattering angle from 25 degree sign to 130 degree sign . The spectrometer will be operational at the ADRESS (advanced resonant spectroscopies) beamline of the Swiss Light Source from 2007.

Ghiringhelli, G.; Piazzalunga, A.; Dallera, C.; Trezzi, G.; Braicovich, L.; Schmitt, T.; Strocov, V. N.; Betemps, R.; Patthey, L.; Wang, X.; Grioni, M. [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan (Italy); Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Institut de Physique des Nanostructures, Ecole Polytechnique Fedederale de Lausanne, CH-1015 Lausanne (Switzerland)

2006-11-15

266

X-ray optics of gold nanoparticles.  

PubMed

Gold nanoparticles have been investigated as contrast agents for traditional x-ray medical procedures, utilizing the strong absorption characteristics of the nanoparticles to enhance the contrast of the detected x-ray image. Here we use the Kramers-Kronig relation for complex atomic scattering factors to find the real and imaginary parts of the index of refraction for the medium composed of single-element materials or compounds in the x-ray range of the spectrum. These complex index of refraction values are then plugged into a Lorenz-Mie theory to calculate the absorption efficiency of various size gold nanoparticles for photon energies in the 1-100 keV range. Since the output from most medical diagnostic x-ray devices follows a wide and filtered spectrum of photon energies, we introduce and compute the effective intensity-absorption-efficiency values for gold nanoparticles of radii varying from 5 to 50 nm, where we use the TASMIP model to integrate over all spectral energies generated by typical tungsten anode x-ray tubes with kilovolt potentials ranging from 50 to 150 kVp. PMID:25402878

Letfullin, Renat R; Rice, Colin E W; George, Thomas F

2014-11-01

267

Empirical and semi-empirical interpolation of L X-ray fluorescence parameters for elements in the atomic range 50?Z?92  

NASA Astrophysics Data System (ADS)

In this study, interpolations (empirical and semi-empirical) of L sub-shell fluorescence yield and L shell Coster-Kronig transition probability values and the measured L X-ray production cross-sections, intensity ratios and L sub-shell fluorescence yield values of elements have been performed in the range of 50?Z?92. In this experimental setup, two sources (50 mCi 55Fe and 50 mCi 241Am) were used. L X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV.

Aylikci, V.; Kahoul, A.; Kup Aylikci, N.; Tira?o?lu, E.; Karahan, ?. H.; Abassi, A.; Dogan, M.

2015-01-01

268

Ionization-Gasdynamics Modelling, and X-ray Spectral Calculations, of Wind-Bubbles around Massive Stars  

NASA Astrophysics Data System (ADS)

Using a code that employs a self-consistent method for computing the effects of photo-ionization on circumstellar gas dynamics, we model the formation of wind-driven nebulae around massive stars. Our algorithm incorporates a simplified model of the photo-ionization source, computes the fractional ionization of hydrogen due to the photo-ionizing flux and recombination, and determines self-consistently the energy balance due to ionization, photo-heating and radiative cooling. We take into account changes in stellar properties and mass-loss over the star's evolution. Our multi-dimensional simulations clearly reveal the presence of strong ionization front instabilities, similar to those seen in galactic ionization fronts. Using various X-ray emission models, we compute the X-ray flux and spectra from our wind bubble models, taking the absorption of the X-rays by the ionized bubble into account. Our simulated X-ray spectra compare reasonably well with observed spectra of Wolf-Rayet bubbles. They suggest that X-ray nebulae around massive stars may not be easily detectable, consistent with observations.

Dwarkadas, V.; Rosenberg, D.

2014-07-01

269

On X-Ray Variability in Seyfert Galaxies  

NASA Technical Reports Server (NTRS)

This paper presents a quantification of the X-ray variability amplitude for 79 ASCA observations of 36 Seyfert 1 galaxies. We find that consideration of sources with the narrowest permitted lines in the optical band introduces scatter into the established correlation between X-ray variability and nuclear luminosity. Consideration of the X-ray spectral index and variability properties together shows distinct groupings in parameter space for broad and narrow-line Seyfert 1 galaxies, confirming previous studies. A strong correlation is found between hard X-ray variability and FWHM Hbeta. A range of nuclear mass and accretion rate across the Seyfert population can explain the differences observed in X-ray and optical properties. An attractive alternative model, which does not depend on any systematic difference in central mass, is that the circumnuclear gas of NLSy1s is different to BLSy1s in temperature, optical depth, density or geometry.

Turner, T. J.; George, I. M.; Nandra, K.; Turcan, D.

1999-01-01

270

Small area silicon diffused junction x-ray detectors  

SciTech Connect

The low temperature performance of silicon diffused junction detectors in the measurement of low energy x-rays is reported. The detectors have an area of 0.04 cm/sup 2/ and a thickness of 100 ..mu..m. The spectral resolutions of these detectors were found to be in close agreement with expected values indicating that the defects introduced by the high temperature processing required in the device fabrication were not deleteriously affecting the detection of low energy x-rays. Device performance over a temperature range of 77 to 150/sup 0/K is given. These detectors were designed to detect low energy x-rays in the presence of minimum ionizing electrons. The successful application of silicon diffused junction technology to x-ray detector fabrication may facilitate the development of other novel silicon x-ray detector designs.

Walton, J.T.; Pehl, R.H.; Larsh, A.E.

1981-10-01

271

Hard-Soft-Hard Flare Spectra and Their Energy Dependence in Spectral Evolution of a Solar Hard X-Ray Flare  

NASA Astrophysics Data System (ADS)

In this Letter, we studied the time evolution of the energy-dependent spectral indices for the 2004 November 3 solar hard X-ray flare observed by RHESSI. The common soft-hard-soft (SHS) pattern spectra were found at the lower energies, while a new feature, hard-soft-hard (HSH), was found at higher energies for each subpeak. As the energy increases, the SHS pattern is gradually converted into the HSH pattern. Some possible explanations for the spectral evolution and its energy dependence are discussed, such as the return current.

Shao, Chengwen; Huang, Guangli

2009-04-01

272

Uncertainty analysis in the simulation of X-ray spectra in the diagnostic range using the MCNP5 code.  

PubMed

An accurate knowledge of the photonic spectra emitted by X-ray tubes in radiodiagnostics is essential to better estimate the imparted dose to patients and to improve the image quality obtained with these devices. In this work, several X-ray spectra have been simulated using the MCNP5 code to simulate X-ray production in a commercial device. To validate the Monte Carlo results, simulated spectra have been compared to those extracted from the IPEM 78 database. The uncertainty associated to some geometrical features of the tube and its effect on the simulated spectra has been analyzed using the Noether-Wilks formula. This analysis has been focused on the thickness of collimators, filters, shielding and barrel shutter. Furthermore, results show that the uncertainty due to geometrical parameters (0.98% in terms of Root Mean Squared) is higher than the statistical uncertainty associated to the MCNP5 calculations. PMID:22254330

Gallardo, S; Querol, A; Ródenas, J; Verdú, G

2011-01-01

273

X-ray Spectral Measurements of the Most Massive Stars: Stellar Wind Mass-Loss Rates and Shock Physics  

E-print Network

Physics David Cohen Department of Physics & Astronomy Swarthmore College Maurice Leutenegger (Goddard/Themes: Significant technological advances in X-ray astronomy have driven discovery over the last few decades. New smaller #12;small spatial scales can be studied using spectroscopy #12;Ultraviolet spectrum showing wind

Cohen, David

274

Time-dependent, x-ray spectral unfolds and brightness temperatures for intense Li + ion beam-driven hohlraums  

NASA Astrophysics Data System (ADS)

X-ray-producing hohlraums are being studied as indirect drives for inertial confinement fusion targets. In a 1994 target series on the PBFAII accelerator, cylindrical hohlraum targets were heated by an intense Li+ ion beam and viewed by an array of 13 time-resolved, filtered x-ray detectors (XRDs). The unfold operator (UFO) code and its suite of auxiliary functions were used extensively in obtaining time-resolved x-ray spectra and radiation temperatures from this diagnostic. The UFO was also used to obtain fitted response functions from calibration data, to simulate data from blackbody x-ray spectra of interest, to determine the suitability of various unfolding parameters (e.g., energy domain, energy partition, smoothing conditions, and basis functions), to interpolate the XRD signal traces, and to unfold experimental data. The simulation capabilities of the code were useful in understanding an anomalous feature in the unfolded spectra at low photon energies (?100 eV). Uncertainties in the differential and energy-integrated unfolded spectra were estimated from uncertainties in the data. The time-history of the radiation temperature agreed well with independent calculations of the wall temperature in the hohlraum.

Fehl, D. L.; Chandler, G. A.; Biggs, F.; Dukart, R. J.; Moats, A. R.; Leeper, R. J.

1997-01-01

275

Use of depth information from in-depth photon counting detectors for x-ray spectral imaging: a preliminary simulation study  

NASA Astrophysics Data System (ADS)

Purpose: Photon counting x-ray detectors (PCXD) may improve dose-efficiency but are hampered by limited count rate. They generally have imperfect energy response. Multi-layer ("in-depth") detectors have been proposed to enable higher count rates but the potential benefit of the depth information has not been explored. We conducted a simulation study to compare in-depth detectors against single layer detectors composed of common materials. Both photon counting and energy integrating modes were studied. Methods: Polyenergetic transmissions were simulated through 25cm of water and 1cm of calcium. For PCXD composed of Si, GaAs or CdTe a 120kVp spectrum was used. For energy integrating x-ray detectors (EIXD) made from GaAs, CdTe or CsI, spectral imaging was done using 80 and 140kVp and matched dose. Semi-ideal and phenomenological energy response models were used. To compare these detectors, we computed the Cramér-Rao lower bound (CRLB) of the variance of basis material estimates. Results: For PCXDs with perfect energy response, depth data provides no additional information. For PCXDs with imperfect energy response and for EIXDs the improvement can be significant. E.g., for a CdTe PCXD with realistic energy response, depth information can reduce the variance by ~50%. The improvement depends on the x-ray spectrum. For a semi-ideal Si detector and a narrow x-ray spectrum the depth information has minimal advantage. For EIXD, the in-depth detector has consistent variance reduction (15% and 17%~19% for water and calcium, respectively). Conclusions: Depth information is beneficial to spectral imaging for both PCXD and EIXD. The improvement depends critically on the detector energy response.

Yao, Yuan; Bornefalk, Hans; Hsieh, Scott S.; Danielsson, Mats; Pelc, Norbert J.

2014-03-01

276

Momentum and polarization dependence of single-magnon spectral weight for CuL3 -edge resonant inelastic x-ray scattering from layered cuprates  

NASA Astrophysics Data System (ADS)

Recently it was predicted theoretically and confirmed experimentally that in cuprates single-magnon dispersions can be mapped out with resonant inelastic x-ray scattering (RIXS) at the copper L3 edge. To further establish RIXS as a viable technique we investigate the momentum and incident photon polarization dependence of the single-magnon spectral weight in a variety of layered undoped antiferromagnetic compounds. The agreement of experimental and theoretical results bolsters the assignment of RIXS spectral features to single magnons. This detailed analysis allows to disentangle single-magnon scattering from other spectral contributions. Moreover, it is a necessary premise for future research aimed at investigating processes that modulate spectral weights beyond the predictions of linear spin-wave theory.

Braicovich, L.; Moretti Sala, M.; Ament, L. J. P.; Bisogni, V.; Minola, M.; Balestrino, G.; di Castro, D.; de Luca, G. M.; Salluzzo, M.; Ghiringhelli, G.; van den Brink, J.

2010-05-01

277

PXAMS -- Projectile X ray AMS: X ray yields and applications  

SciTech Connect

Characteristic x rays have recently been explored as a method for the detection and identification of ions in accelerator mass spectrometry (AMS). After analysis in the AMS spectrometer, the ions stop in an appropriately chosen target and the induced x rays identify the ions by atomic number. For the application of AMS to higher mass isotopes, characteristic x rays allow significantly better discrimination of competing atomic isobars than is possible using energy loss detectors. Characteristic x rays also show promise as a convenient component in hybrid detection systems. Measurements of x ray yields are presented for Si, Fe, Ni, Se, Mo, and Pd ions of 0.5--2 MeV/AMU. The yields rise by more than a factor of 10 over this energy range, and approach 1 x-ray per incident ion at 2 MeV/AMU for the lighter ions. Preliminary work on the application of PXAMS to the detection of {sup 79}Se is described.

McAninch, J.E.; Bench, G.S.; Freeman, S.P.H.T.; Roberts, M.L.; Southon, J.R.; Vogel, J.S.; Proctor, I.D. [Lawrence Livermore National Lab., CA (United States). Center for Accelerator Mass Spectrometry

1994-10-07

278

Characterization of a deep depletion, back-illuminated charge-coupled device in the x-ray range  

SciTech Connect

In this Note we report on the characterization of a 'deep depletion' charge-coupled device (CCD) in the keV range. Measurement of quantum efficiency for different energies from 4.5 until 27 keV is given. A measurement of the capability of the CCD to detect single photons is also reported together with a determination of the spatial and spectral resolution. A Monte Carlo simulation was used to give a quantitative comparison with the measured spatial resolution.

Zamponi, Flavio; Kaempfer, Tino; Morak, Andreas; Uschmann, Ingo; Foerster, Eckhart [Roentgenoptik Arbeitsgruppe, Institut fuer Optik und Quantenelektronik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany)

2005-11-15

279

An accurate X-ray spectrographic method for the analysis of a wide range of geological samples  

Microsoft Academic Search

For accurate X-ray spectrographic analysis of geological samples of widely varying composition, a fusion with lithium borate containing lanthanum oxide is used to make a suitable glass disc. Mg, Al, Si, P, K, Ca, Ti, Mn and Fe are determined on this disc, using similar discs made with pure chemicals for calibration. \\

K. Norrish; J. T. Hutton

1969-01-01

280

Absolute x-ray energy calibration over a wide energy range using a diffraction-based iterative method  

E-print Network

) Soft x-ray scattering facility at the Advanced Light Source with real-time data processing and analysis of an inverse Compton scattering source local spectrum using k-edge filters Appl. Phys. Lett. 100, 164104 (2012 Rev. Sci. Instrum. 83, 045110 (2012) Precision linac and laser technologies for nuclear photonics

Duffy, Thomas S.

281

The 2006-2007 Active Phase Of Anomalous X-Ray Pulsar 4U 0142+61: Radiative and Timing Changes, Bursts, and Burst Spectral Features  

NASA Technical Reports Server (NTRS)

After at least 6 years of quiescence, Anomalous X-ray Pulsar (AXP) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission. The bursts, the first seen from this AXP in >11 years of Rossi X-ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from 8-3x10(exp 3)s. The first five burst spectra are well modeled by blackbodies, with temperatures kT approx. 2 - 6 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus three emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9+/-0.4)x10(exp -7) Hz, which recovered with a decay time of 17+/-2 days by more than the initial jump, implying a net spin-down of the pulsar. We discuss these events in the context of the magnetar model.

Gavril, Fotis P.; Dib, Rim; Kaspi, Victoria M.

2009-01-01

282

Bent crystal spectrometer for solar X-ray spectroscopy  

NASA Technical Reports Server (NTRS)

A bent crystal spectrometer employs a collimated beam of X-rays incident on the crystal over a range of Bragg angles determined by the orientation and curvature of the crystal surface. It provides continuous and simultaneous coverage of all X-ray wavelengths within its spectral range. In-flight testing for solar X-ray spectroscopy was performed using a small instrument to supplement the wavelength coverage of several scanning spectrometers used to study solar active regions in the 9-24 A range. Later testing included modifications to alleviate problems caused by ultraviolet radiation. Future usage of the device will include studies of time variable emission from solar flares or discrete galactic X-ray sources, and the first major experiment to utilize bent crystal spectrometers will be the Solar Maximum Mission satellite in 1979.

Rapley, C. G.; Culhane, J. L.; Acton, L. W.; Catura, R. C.; Joki, E. G.; Bakke, J. C.

1977-01-01

283

X-ray microtomography  

SciTech Connect

In this tutorial, we describe X-ray microtomography as a technique to nondestructively characterize material microstructure in three dimensions at a micron level spatial resolution. While commercially available laboratory scale instrumentation is available, we focus our attention on synchrotron-based systems, where we can exploit a high flux, monochromatic X-ray beam to produce high fidelity three-dimensional images. A brief description of the physics and the mathematical analysis behind the technique is followed by example applications to specific materials characterization problems, with a particular focus on the utilization of three-dimensional image processing that can be used to extract a wide range of useful information.

Landis, Eric N., E-mail: landis@maine.edu [Department of Civil and Environmental Engineering, University of Maine, 5711 Boardman Hall, Orono, Maine 04469 (United States); Keane, Denis T., E-mail: dtkeane@northwestern.edu [Department of Materials Science and Engineering, Northwestern University (United States); DND-CAT, Advanced Photon Source, Argonne National Laboratory, Bldg. 432/A002, 9700 S. Cass Ave, Argonne, Illinois 60439 (United States)

2010-12-15

284

Miniature x-ray source  

DOEpatents

A miniature x-ray source capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature x-ray source comprises a compact vacuum tube assembly containing a cathode, an anode, a high voltage feedthru for delivering high voltage to the anode, a getter for maintaining high vacuum, a connection for an initial vacuum pump down and crimp-off, and a high voltage connection for attaching a compact high voltage cable to the high voltage feedthru. At least a portion of the vacuum tube wall is highly x-ray transparent and made, for example, from boron nitride. The compact size and potential for remote operation allows the x-ray source, for example, to be placed adjacent to a material sample undergoing analysis or in proximity to the region to be treated for medical applications.

Trebes, James E. (Livermore, CA); Stone, Gary F. (Livermore, CA); Bell, Perry M. (Tracy, CA); Robinson, Ronald B. (Modesto, CA); Chornenky, Victor I. (Minnetonka, MN)

2002-01-01

285

Transmission crystal x-ray spectrometer covering the 6 keV-18 keV energy range with E??E = 1800 instrumental resolving power.  

PubMed

A high-resolution x-ray spectrometer utilizing a thin quartz transmission crystal and covering the 6 keV-18 keV energy range has been developed and tested. The spectrometer consists of a cylindrically bent crystal in a vacuum housing. The crystal position and the range of Bragg angles that are incident on the crystal can be adjusted to record an ?4 keV wide spectrum in the 6 keV-18 keV range. The spectrometer is of the Cauchois type and has a compact linear geometry that is convenient for deployment at laser-produced plasma, EBIT, and other x-ray sources. Test spectra of the W L and Mo K lines from laboratory sources have linewidths as small as 11 eV, approaching the natural widths, and instrumental resolving power as high as 1800. Techniques for enhancing the energy resolution are experimentally demonstrated. PMID:23126934

Seely, John; Feldman, Uri; Brown, Charles; Pereira, Nino; Hudson, Lawrence; Glover, Jack; Silver, Eric

2012-10-01

286

Advanced x-ray imaging spectrometer  

NASA Technical Reports Server (NTRS)

An x-ray spectrometer that also provides images of an x-ray source. Coded aperture imaging techniques are used to provide high resolution images. Imaging position-sensitive x-ray sensors with good energy resolution are utilized to provide excellent spectroscopic performance. The system produces high resolution spectral images of the x-ray source which can be viewed in any one of a number of specific energy bands.

Callas, John L. (Inventor); Soli, George A. (Inventor)

1998-01-01

287

Soft x-ray solar polarimeter-spectrometer  

NASA Astrophysics Data System (ADS)

We present an innovative soft X-ray polarimeter and spectrometer SOLPEX, the instrument to be mounted aboard the International Space Station (ISS) in 2015/2016. The SOLPEX will be composed of three individual measuring units: the soft X-ray polarimeter with 1-2% linear polarization detection limit, a fast-rotating drum X-ray spectrometer with very high time resolution (0.1s) and a simple pin-hole soft X-ray imager-spectrometer with moderate spatial (~20arcsec), spectral (0.5 keV) and high time resolution (0.1s). This set of instruments will provide unique opportunity to complement the efforts to reliably measure the X-ray polarization and contribute towards understanding the physics of solar flares. The standard flare model states that electrons are being accelerated in specific regions of the corona at or near magnetic reconnection site and then propagate along reconnected magnetic field lines toward the atmospheric denser layers. There, they are decelerated and lose their energy mainly through the bremsstrahlung process. Deposited energy is readily converted to directed evaporation of the plasma to be detected through the Doppler-shifted emission lines in extreme ultraviolet and soft X-ray spectral ranges Due to highly anisotropic character of impulsive phase electron beams, resulting emission is expected to be polarized. Both these processes: bremsstrahlung emission of supposedly polarized X-ray flux and accompanying plasma evaporation velocities are to be simultaneously observed by the proposed SOLPEX instruments.

Ste?licki, Marek; Sylwester, Janusz; Siarkowski, Marek; Kowali?ski, Miros?aw; P?ocieniak, Stefan; B?ka?a, Jaros?aw; Szaforz, ?aneta; Kuzin, Sergey

2014-12-01

288

X-Ray Data Booklet  

NSDL National Science Digital Library

The X-Ray Data Booklet is provided by the Center for X-ray Optics and Advanced Light Source of the Lawrence Berkeley National Laboratory, which is funded by the US Department of Energy. The online publication contains topics such as x-ray properties of elements, mass absorption coefficients, synchrotron radiation, scattering processes, low-energy electron ranges in matter, optics and detectors, specular reflectivities for grazing-incidence mirrors, and other practical information that has been produced and gathered as a result of research at the center. Additional features of the informative site include an interactive periodic table of X-Ray properties and free deliverable hardcopies of the document.

Attwood, David.

2000-01-01

289

X-RAY POINT-SOURCE POPULATIONS CONSTITUTING THE GALACTIC RIDGE X-RAY EMISSION  

SciTech Connect

Apparently diffuse X-ray emission has been known to exist along the central quarter of the Galactic Plane since the beginning of X-ray astronomy; this is referred to as the Galactic Ridge X-ray emission (GRXE). Recent deep X-ray observations have shown that numerous X-ray point sources account for a large fraction of the GRXE in the hard band (2-8 keV). However, the nature of these sources is poorly understood. Using the deepest X-ray observations made in the Chandra bulge field, we present the result of a coherent photometric and spectroscopic analysis of individual X-ray point sources for the purpose of constraining their nature and deriving their fractional contributions to the hard-band continuum and Fe K line emission of the GRXE. Based on the X-ray color-color diagram, we divided the point sources into three groups: A (hard), B (soft and broad spectrum), and C (soft and peaked spectrum). The group A sources are further decomposed spectrally into thermal and non-thermal sources with different fractions in different flux ranges. From their X-ray properties, we speculate that the group A non-thermal sources are mostly active galactic nuclei and the thermal sources are mostly white dwarf (WD) binaries such as magnetic and non-magnetic cataclysmic variables (CVs), pre-CVs, and symbiotic stars, whereas the group B and C sources are X-ray active stars in flares and quiescence, respectively. In the log N-log S curve of the 2-8 keV band, the group A non-thermal sources are dominant above Almost-Equal-To 10{sup -14} erg cm{sup -2} s{sup -1}, which is gradually taken over by Galactic sources in the fainter flux ranges. The Fe K{alpha} emission is mostly from the group A thermal (WD binaries) and the group B (X-ray active stars) sources.

Morihana, Kumiko [Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)] [Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Tsujimoto, Masahiro; Ebisawa, Ken [Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, 3-1-1 Yoshino-dai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)] [Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, 3-1-1 Yoshino-dai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Yoshida, Tessei, E-mail: morihana@crab.riken.jp [National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan)] [National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan)

2013-03-20

290

Neutron spectral measurements in an intense photon field associated with a high-energy x-ray radiotherapy machine.  

PubMed

High-energy x-ray radiotherapy machines in the supermegavoltage region generate complex neutron energy spectra which make an exact evaluation of neutron shielding difficult. Fast neutrons resulting from photonuclear reactions in the x-ray target and collimators undergo successive collisions in the surrounding materials and are moderated by varying amounts. In order to examine the neutron radiation exposures quantitatively, the neutron energy spectra have been measured inside and outside the treatment room of a Sagittaire medical linear accelerator (25-MV x rays) located at Yale-New Haven Hospital. The measurements were made using a Bonner spectrometer consisting of 2-, 3-, 5-, 8-, 10- and 12-in.-diameter polyethylene spheres with 6Li and 7Li thermoluminescent dosimeter (TLD) chips at the centers, in addition to bare and cadmium-covered chips. The individual TLD chips were calibrated for neutron and photon response. The spectrometer was calibrated using a known PuBe spectrum Spectrometer measurements were made at Yale Electron Accelerator Laboratory and results compared with a neutron time-of-flight spectrometer and an activation technique. The agreement between the results from these independent methods is found to be good, except for the measurements in the direct photon beam. Quality factors have been inferred for the neutron fields inside and outside the treatment room. Values of the inferred quality factors fall primarily between 4 and 8, depending on location. PMID:412048

Holeman, G R; Price, K W; Friedman, L F; Nath, R

1977-01-01

291

X-ray timing and spectral analysis of the old gamma-ray pulsar J1836+5925  

NASA Astrophysics Data System (ADS)

PSR J1836+5925 is a bright gamma-ray source with a long observational history in various energy bands. Its radio-quietness, and non-detection of X-ray pulsations in previous observations have hindered a detailed analysis of this source. At the characteristic age of 1.83 Myr, it is one of the oldest non-recycled gamma-ray pulsars known, making it a useful object for understanding evolution of high-energy emission from rotation powered pulsars. In our 80 ks XMM-Newton observation of this pulsar, we detected unambiguous 5.77 Hz pulsations, consistent with its known gamma-ray ephemeris and assessed a low X-ray pulsed fraction of ˜ 0.34. In the 0.15 - 10 keV phase-integrated spectrum, non-thermal emission with the photon index Gamma ? 1.8 ± 0.2 dominates above 0.7 keV, whereas at lower energies, the spectrum requires a dominant kT = 63 ± 5 eV blackbody or, alternatively, a 24 ± 3 eV neutron star atmosphere model. We will also present the phase-resolved analysis of the pulsar spectrum and phase-matched X-ray and gamma-ray pulse profiles. Finally, we will discuss the implications of our results for thermal and magnetospheric emission of rotation powered pulsars.

Arumugasamy, Prakash; Pavlov, George; Blake, Joseph

292

Timing and Spectral Properties of Be/X-Ray Pulsar EXO 2030+375 during a Type I Outburst  

NASA Astrophysics Data System (ADS)

We present results from a study of broadband timing and spectral properties of EXO 2030+375 using a Suzaku observation. Pulsations with a period of 41.41 s and strong energy-dependent pulse profiles were clearly detected up to 100 keV. Narrow dips are seen in the profiles up to ~70 keV. The presence of prominent dips at several phases in the profiles up to such high energy ranges was not seen before. At higher energies, these dips gradually disappeared and the profile appeared to be single-peaked. The 1.0-200.0 keV broadband spectrum is found to be well described by a partial covering high-energy cutoff power-law model. Several low-energy emission lines are also detected in the pulsar spectrum. We fitted the spectrum using neutral as well as partially ionized absorbers along with the above continuum model yielding similar parameter values. The partial covering with a partially ionized absorber resulted in a marginally better fit. The spectral fitting did not require any cyclotron feature in the best-fit model. To investigate the changes in spectral parameters at dips, we carried out pulse-phase-resolved spectroscopy. During the dips, the value of the additional column density was estimated to be high compared to other pulse phases. While using a partially ionized absorber, the value of the ionization parameter is also higher at the dips. This may be the reason for the presence of dips up to higher energies. No other spectral parameters show any systematic variation with pulse phases of the pulsar.

Naik, Sachindra; Maitra, Chandreyee; Jaisawal, Gaurava K.; Paul, Biswajit

2013-02-01

293

Short-range order of undercooled melts of PdZr2 intermetallic compound studied by X-ray and neutron scattering experiments  

NASA Astrophysics Data System (ADS)

The short-range order in undercooled melts of the intermetallic Zr2Pd glass-forming alloy is investigated by combining electrostatic levitation (ESL) with high-energy X-ray diffraction and neutron diffraction. Experimentally determined structure factors are measured and analyzed with respect to various structures of short-range order. The comparative X-ray and neutron scattering experiments allow for investigations of topological and chemical short-range order. Based on these studies, no preference of a specific short-range order is found for the liquid Zr2Pd glass-forming alloy, even in the metastable state of the deeply undercooled melt. This is in agreement with an earlier report from X-ray diffraction and molecular-dynamics studies of a Zr75.5Pd24.5 liquid, which showed a broad distribution of cluster types. The results for the Zr2Pd liquid are discussed with respect to the glass-forming ability of this melt.

Klein, S.; Holland-Moritz, D.; Herlach, D. M.; Mauro, N. A.; Kelton, K. F.

2013-05-01

294

Bragg reflection x ray optics  

Microsoft Academic Search

After a brief summary of the properties of x rays and of materials in the x ray frequency range, the ray optics and microscopic wavefield optics of Bragg reflection in perfect crystals are reviewed. Particular attention is given to the phase relationships between fields, to the spatial modulation of wavefields and to the role of the structure amplitude in determining

M. Hart

1971-01-01

295

Magnetic Fields of Neutron Stars in X-Ray Binaries  

NASA Astrophysics Data System (ADS)

A substantial fraction of the known neutron stars resides in X-ray binaries -- systems in which one compact object accretes matter from a companion star. Neutron stars in X-ray binaries have magnetic fields among the highest found in the Universe, spanning at least the range from $\\sim10^8$ to several 10$^{13}$ G. The magnetospheres around these neutron stars have a strong influence on the accretion process, which powers most of their emission. The magnetic field intensity and geometry, are among the main factors responsible for the large variety of spectral and timing properties observed in the X-ray energy range, making these objects unique laboratories to study the matter behavior and the radiation processes in magnetic fields unaccessible on Earth. In this paper we review the main observational aspects related to the presence of magnetic fields in neutron star X-ray binaries and some methods that are used to estimate their strength.

Revnivtsev, Mikhail; Mereghetti, Sandro

2014-12-01

296

Skull x-ray  

MedlinePLUS

X-ray - head; X-ray - skull; Skull radiography; Head x-ray ... will be asked to lie on the x-ray table or sit in a chair. Your head ... is little or no discomfort during an x-ray. If there is a head injury , positioning the ...

297

X-Ray Diffraction Apparatus  

NASA Technical Reports Server (NTRS)

An x-ray diffraction apparatus for use in analyzing the x-ray diffraction pattern of a sample is introduced. The apparatus includes a beam source for generating a collimated x-ray beam having one or more discrete x-ray energies, a holder for holding the sample to be analyzed in the path of the beam, and a charge-coupled device having an array of pixels for detecting, in one or more selected photon energy ranges, x-ray diffraction photons produced by irradiating such a sample with said beam. The CCD is coupled to an output unit which receives input information relating to the energies of photons striking each pixel in the CCD, and constructs the diffraction pattern of photons within a selected energy range striking the CCD.

Blake, David F. (Inventor); Bryson, Charles (Inventor); Freund, Friedmann (Inventor)

1996-01-01

298

Very fast X-ray spectral variability in Cygnus X-1: origin of the hard- and soft-state emission components  

NASA Astrophysics Data System (ADS)

The way in which the X-ray photon index, ?, varies as a function of count rate is a strong diagnostic of the emission processes and emission geometry around accreting compact objects. Here we present the results from a study using a new, and simple, method designed to improve sensitivity to the measurement of the variability of ? on very short time-scales. We have measured ? in ˜2 million spectra, extracted from observations with a variety of different accretion rates and spectral states, on time-scales as short as 16 ms for the high-mass X-ray binary Cygnus X-1 (and in a smaller number of spectra for the low-mass X-ray binary GX 339-4), and have cross-correlated these measurements with the source count rate. In the soft-state cross-correlation functions (CCFs), we find a positive peak at zero lag, stronger and narrower in the softer observations. Assuming that the X-rays are produced by Compton scattering of soft seed photons by high-energy electrons in a corona, these results are consistent with Compton cooling of the corona by seed photons from the inner edge of the accretion disc, the truncation radius of which increases with increasing hardness ratio. The CCFs produced from the hard-state observations, however, show an anti-correlation which is most easily explained by variation in the energy of the electrons in the corona rather than in variation of the seed photon flux. The hard-state CCFs can be decomposed into a narrow anti-correlation at zero lag, which we tentatively associate with the effects of self-Comptonization of cyclo-synchrotron seed photons in either a hot, optically thin accretion flow or the base of the jet, and a second, asymmetric component which we suggest is produced as a consequence of a lag between the soft and hard X-ray emission. The lag may be caused by a radial temperature/energy gradient in the Comptonizing electrons combined with the inward propagation of accretion rate perturbations.

Skipper, Chris J.; McHardy, Ian M.; Maccarone, Thomas J.

2013-09-01

299

Interpretation of the X-ray Spectral Variation of 1H0707-495 with a Variable Double Partial Covering Model  

E-print Network

The Narrow-line Seyfert 1 galaxy 1H0707-495 is known to exhibit significant X-ray spectral variations. Its X-ray energy spectrum is characterized by a strong soft excess emission, an extremely deep iron K-edge structure at ~7 keV, and a putative iron L-line/edge feature at ~1 keV. We have found that the energy spectrum of 1H0707-495 in 0.5-10 keV is successfully explained by a "variable double partial covering model" where the original continuum spectrum, which is composed of the soft multi-color disk blackbody component and the hard power-law component, is partially covered by two ionized absorption layers with different ionization states and the same partial covering fraction. The lower-ionized and thicker absorption layer primarily explains the iron K-edge feature, and the higher-ionized and thinner absorption layer explains the L-edge feature. We have discovered that the observed significant intensity/spectral variation within a ~ day is mostly explained by only variation of the partial covering fraction....

Mizumoto, Misaki; Sameshima, Hiroaki

2014-01-01

300

Variability of Soft X-ray Spectral Shape: Narrow-Line Seyfert 1 Galaxies versus Broad-Line Seyfert 1 Galaxies  

E-print Network

In order to understand how the soft X-ray spectra vary we present the Hardness Ratio 1 versus Count Rates (HR1-CTs) correlation of 8 Narrow-line Seyfert 1 Galaxies (NLS1s) and 14 Broad-line Seyfert1 Galaxies (BLS1s) obtained during the ROSAT PSPC pointing observations. According to our criteria, six of the NLS1s show a positive HR1-CTs correlation, and seven of the BLS1s display an anti-correlation of HR1 versus CTs. The other 2 NLS1s and 7 BLS1s do not show a clear HR1-CTs correlation. From these we can see that the NLS1s statistically show a different spectral shape variability with flux change from the BLS1s: the spectra of NLS1s become harder as total flux increases while those of BLS1s soften. We attribute the different spectral variations to a strong stable 'soft excess' in NLS1s, while it is weak in BLS1s. For two types of objects, the power law component similarly becomes softer with increasing intensity. These imply that the soft excess originates from the Big Blue Bump and power law emission is from Compton upscattering of UV or Soft X-ray photons. Our results are consistent with what is widely accepted that NLS1s have smaller black hole masses and higher accretion rates than BLS1s.

Linpeng Cheng; Jianyan Wei; Yongheng Zhao

2001-10-26

301

Ultra-thin curved transmission crystals for high resolving power (up to E/?E = 6300) x-ray spectroscopy in the 6-13??keV energy range.  

PubMed

Ultra-thin curved transmission crystals operating in the Cauchois spectrometer geometry were evaluated for the purpose of achieving high spectral resolution in the 6-13 keV x-ray energy range. The crystals were silicon (111) and sapphire R-cut wafers, each 18 ?m thick, and a silicon (100) wafer of 50-?m thickness. The W L?1 spectral line at 8.398 keV from a laboratory source was used to evaluate the resolution. The highest crystal resolving power, E/?E=6300, was achieved by diffraction from the (33-1) planes of the Si(100) wafer that was cylindrically bent to a radius of curvature of 254 mm, where the (33-1) planes have an asymmetric angle of 13.26° from the normal of the crystal surface facing the x-ray source. This work demonstrates the ability to measure highly resolved line shapes of the K transitions of the elements Fe through Kr and the L transitions of the elements Gd through Th using a relatively compact spectrometer optical system and readily available thin commercial wafers. The intended application is as a diagnostic of laser-produced plasmas where the presence of multiple charged states and broadenings from high temperature and density requires high-resolution methods that are robust in a noisy source environment. PMID:25503010

Seely, John F; Hudson, Lawrence T; Glover, Jack L; Henins, Albert; Pereira, Nino

2014-12-15

302

X-ray luminescence based spectrometer for investigation of scintillation properties  

SciTech Connect

A new x-ray luminescence based spectrometer was developed and installed to examine the scintillation properties of materials while revealing the origins of luminescence and investigating trapping defects. Measurements were performed on a number of undoped and Ce doped yttrium aluminum garnet crystals and various luminescence centers were characterized. The measured x-ray luminescence spectra provide information about the spectral range and the scintillation efficiency and linearity. The efficiency of charge-carriers production due to x ray, their energy transfer to the luminescence centers, and the efficiency of luminescence are all reflected in the efficiency of x-ray luminescence.

Varney, C. R.; Khamehchi, M. A.; Ji, Jianfeng; Selim, F. A. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States)

2012-10-15

303

X-ray absorption spectral studies of copper(II) mixed ligand complexes having ethylenediamine as one of the ligands  

NASA Astrophysics Data System (ADS)

X-ray absorption spectra of copper(II) mixed ligand complexes, having ethylenediamine (en) as one of the ligands, have been recorded at the K-edge of copper at the dispersive extended X- ray absorption fine structure (EXAFS) beamline (BL-8) at the 2.5 GeV INDUS-2 Synchrotron, RRCAT, Indore, India. The samples studied are: Cu(en)2(ClO4)2, Cu(en)2Br2.H2O and Cu(en)2SO4. The data obtained has been processed using EXAFS data analysis program Athena. The K-edge has been found to split in two edges K and K' in each of the complex. The energies of the edges K(EK) and K'(EK') and the principal absorption maximum A(EA) have been determined from the derivative spectra. The chemical shift has been utilized to determine the oxidation state of copper in the complexes and to estimate effective nuclear charge (ENC) on the absorbing atom. The EXAFS data has been used to determine the bond lengths in the complexes using three different graphical methods. The bond lengths, obtained from one of these methods and the Fourier transformation method, are comparable with each other, showing that both of these methods give phase uncorrected bond lengths.

Dwivedi, Shikha; Joshi, S. K.; Hinge, V. K.; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

2014-09-01

304

EXIST: All-Sky Hard X-ray Imaging and Spectral-Temporal Survey for Black Holes  

E-print Network

The Energetic X-ray Imaging Survey Telescope (EXIST) is under study for the proposed Black Hole Finder Probe, one of the three Einstein Probe missions in NASA's proposed Beyond Einstein Program. EXIST would have unique capabilities: it would survey the full sky at 5-600 keV each 95min orbit with 0.9-5 arcmin, 10microsec - 45min, and ~0.5-5 keV resolution to locate sources to 10arcsec and enable black holes to be surveyed and studied on all scales. With 5sigma survey sensitivity (0.5-1y) Fx(40-80 keV) ~5 x 10^-13 cgs, or comparable to the ROSAT soft X-ray (0.3-2.5 keV) sky survey, a large sample (~2-4 x 10^4) of obscured AGN will be identified and a complete sample of accreting stellar mass BHs in the Galaxy will be found. The all-sky/all-time coverage will allow rare events to be measured, such as possible stellar disruption flares from dormant AGN out to ~200 Mpc. A large sample (~2-3/day) of GRBs will be located (<~10arcsec) at sensitivities and bandwidths much greater than previously and likely yield the highest redshift events and constraints on Pop III BHs. An outline of the mission design from the ongoing concept study is presented.

Jonathan E. Grindlay

2005-12-30

305

EXIST: All-sky hard X-ray imaging and spectral-temporal survey for black holes [review article  

NASA Astrophysics Data System (ADS)

The energetic X-ray imaging survey telescope (EXIST) is under study for the proposed Black Hole Finder Probe, one of the three Einstein Probe missions in NASA's proposed Beyond Einstein Program. EXIST would have unique capabilities: it would survey the full sky at 5-600 keV each 95 min orbit with 0.9-5', 10 ?s-45 min and ˜0.5-5 keV resolution to locate sources to 10? and enable black holes to be surveyed and studied on all scales. With a 1y/5 ? survey sensitivity Fx (40-80 keV) ˜ 5 × 10 -13 erg cm -2 s -1, comparable to the ROSAT soft X-ray (0.3-2.5 keV) sky survey, a large sample (?2-4 × 10 4) of obscured AGN will be identified and a complete sample of accreting stellar mass BHs in the Galaxy will be found. The all-sky/all-time coverage will allow rare events to be measured, such as possible stellar disruption flares from dormant AGN out to ˜100 Mpc. A large sample (˜2-3/day) of GRBs will be located (?10?) at sensitivities and bandwidths much greater than previously and likely yield the highest redshift events and constraints on Pop III BHs. An outline of the mission design from the ongoing concept study is presented.

Grindlay, Jonathan E.

2005-11-01

306

Interpretation of the X-ray spectral variation of 1H 0707-495 with a variable double partial covering model  

NASA Astrophysics Data System (ADS)

The narrow-line Seyfert 1 galaxy 1H 0707-495 is known to exhibit significant X-ray spectral variations. Its X-ray energy spectrum is characterized by a strong soft excess emission, an extremely deep iron K-edge structure at ˜ 7 keV, and a putative iron L-line/edge feature at ˜ 1 keV. We have found that the energy spectrum of 1H 0707-495 in 0.5-10 keV is successfully explained by a "variable double partial covering model" where the original continuum spectrum, which is composed of a soft multi-color disk blackbody component and a hard power-law component, is partially covered by two ionized absorption layers with different ionization states and the same partial covering fraction. The lower-ionized and thicker absorption layer primarily explains the iron K-edge feature, and the higher-ionized and thinner absorption layer explains the L-edge feature. We have discovered that the observed significant intensity/spectral variation within ˜ 1 d is mostly explained by varying only the partial covering fraction. In our model, the intrinsic luminosity and spectral shape are hardly variable within ˜ 1 d, while some intrinsic variability above 3 keV is recognized. This is consistent with the picture that the multi-color disk blackbody spectrum is almost invariable on this timescale, and the hard power-law component is more variable. We propose that the observed spectral variation of 1H 0707-495 is caused by three physically independent variations with different timescales; (1) intrinsic luminosity variation over days, (2) variation of partial covering fraction on a timescale of hours, and (3) small intrinsic hard component variation above 3 keV on a timescale of hours or less.

Mizumoto, Misaki; Ebisawa, Ken; Sameshima, Hiroaki

2014-12-01

307

The 2006-2007 Active Phase of Anomalous X-Ray Pulsar 4U 0142+61: Radiative and Timing Changes, Bursts,and Burst Spectral Features  

NASA Technical Reports Server (NTRS)

After at least 6 years of quiescence, Anomalous X-ray Pulsar (AXP) 4U 0142+61 entered an active phase in 2006 March that lasted several months and included six X-ray bursts as well as many changes in the persistent X-ray emission. The bursts, the first seen from this AXP in > 11 years of Rossi X-ray Timing Explorer monitoring, all occurred in the interval between 2006 April 6 and 2007 February 7. The burst durations ranged from 0.4 - 1.8 x 10(exp 3) s. The first five burst spectra are well modeled by blackbodies, with temperatures kT approx 2 - 9 keV. However, the sixth burst had a complicated spectrum that is well characterized by a blackbody plus two emission features whose amplitude varied throughout the burst. The most prominent feature was at 14.0 keV. Upon entry into the active phase the pulsar showed a significant change in pulse morphology and a likely timing glitch. The glitch had a total frequency jump of (1.9+/-0.4) x 10(exp -7) Hz, which recovered with a decay time of 17+/-2 days by more than the initial jump, implying a net spin-down of the pulsar. Within the framework of the magnetar model, the net spin-down of the star could be explained by regions of the superfluid that rotate. slower than the rest. The bursts, flux enhancements, and pulse morphology changes can be explained as arising from crustal deformations due to stresses imposed by the highly twisted internal magnetic field. However, unlike other AXP outbursts, we cannot account for a major twist being implanted in the magnetosphere.

Gavriil, Fotis P.; Dib, Rim; Kaspi, Victoria M.

2011-01-01

308

A solar spectral line list between 10 and 200 A modified for application to high spectral resolution X-ray astronomy  

NASA Technical Reports Server (NTRS)

A spectral line list for the 10-200 A range is developed from existing solar spectra for application to high spectral resolution measurements of astrophysical plasmas. The solar spectral line lists are merged into a single comprehensive list. The effect of the solar emission measure distribution is removed from the line intensities, which results in a set of emission rates for the lines that can be applied to many optically thin, low density high temperature plasmas in ionization equilibrium. In addition to the measured solar lines, 250 theoretical lines are added to this list. These lines fall in wavelength regions where the existing solar lists have few lines because of limitations in instrumental sensitivity. Also, some lines have been added because the sun has very little plasma at temperatures of about one million K, and consequently these lines are weak or absent in solar spectra. The entire list contains about 600 lines. Finally, predicted spectra of the two RS CVn stars, alpha Aur (Capella) and UX Ari, are presented at 1 and 0.25 A spectral resolution. Also, the solar spectrum is shown at 1 A resolution, and the emission rate spectrum (spectrum not modified by an emission measure distribution) is shown at very high spectral resolution. The predicted spectra for Capella and UX Ari are based on results obtained from the Einstein and International Ultraviolet Explorer (IUE) spacecraft.

Doschek, G. A.; Cowan, R. D.

1984-01-01

309

X-ray microdiffraction of biominerals.  

PubMed

Biominerals have complex and heterogeneous architectures, hence diffraction experiments with spatial resolutions between 500 nm and 10 ?m are extremely useful to characterize them. X-ray beams in this size range are now routinely produced at many synchrotrons. This chapter provides a review of the different hard X-ray diffraction and scattering techniques, used in conjunction with efficient, state-of-the-art X-ray focusing optics. These include monochromatic X-ray microdiffraction, polychromatic (Laue) X-ray microdiffraction, and microbeam small-angle X-ray scattering. We present some of the most relevant discoveries made in the field of biomineralization using these approaches. PMID:24188780

Tamura, Nobumichi; Gilbert, Pupa U P A

2013-01-01

310

Joint x-ray  

MedlinePLUS

X-ray - joint; Arthrography; Arthrogram ... x-ray technologist will help you position the joint to be x-rayed on the table. Once in place, pictures are taken. The joint may be moved into other positions for more ...

311

X-Rays  

MedlinePLUS

X-rays are a type of radiation called electromagnetic waves. X-ray imaging creates pictures of the inside of ... different amounts of radiation. Calcium in bones absorbs x-rays the most, so bones look white. Fat ...

312

Long-range chemical sensitivity in the sulfur K-edge X-ray absorption spectra of substituted thiophenes.  

PubMed

Thiophenes are the simplest aromatic sulfur-containing compounds and are stable and widespread in fossil fuels. Regulation of sulfur levels in fuels and emissions has become and continues to be ever more stringent as part of governments' efforts to address negative environmental impacts of sulfur dioxide. In turn, more effective removal methods are continually being sought. In a chemical sense, thiophenes are somewhat obdurate and hence their removal from fossil fuels poses problems for the industrial chemist. Sulfur K-edge X-ray absorption spectroscopy provides key information on thiophenic components in fuels. Here we present a systematic study of the spectroscopic sensitivity to chemical modifications of the thiophene system. We conclude that while the utility of sulfur K-edge X-ray absorption spectra in understanding the chemical composition of sulfur-containing fossil fuels has already been demonstrated, care must be exercised in interpreting these spectra because the assumption of an invariant spectrum for thiophenic forms may not always be valid. PMID:25116792

George, Graham N; Hackett, Mark J; Sansone, Michael; Gorbaty, Martin L; Kelemen, Simon R; Prince, Roger C; Harris, Hugh H; Pickering, Ingrid J

2014-09-11

313

X-ray source for microstructure imaging under air conditions based on fs laser plasma  

NASA Astrophysics Data System (ADS)

X-ray emission and possibility of obtaining radiography images with laser plasma X-ray source operating at atmospheric pressure and room temperature is investigated. Table top 40 fs 100 uJ laser and Cu and Fe bulk metal targets were used to produce X-ray emission in spectral range of 3-10 keV. The spectra, yield and size of X-ray source were measured under different experimental conditions. X-ray photons of up to 10 keV energy are produced effectively even by relatively low laser intensity < 1015 W/cm2. The source is applied for absorption imaging provided the sensitivity on 10 ?m sample thickness and 30 ?m spatial resolution of microstructures. The ability to perform phase contrast measurements is demonstrated. The advantages of the proposed method are in smart setup of investigated object within air environment; spectral range tunability; and sensitivity to low-contrast or micron thin details.

Pikuz, S. A., Jr.; Chefonov, O. V.; Gasilov, S. V.; Komarov, P. S.; Ovchinnikov, A. V.; Skobelev, I. Y. U.; Ashitkov, S. Y. U.; Agranat, M. V.; Faenov, A. Y. A.

2010-08-01

314

Determination of sulfur and chlorine in fodder by X-ray fluorescence spectral analysis and comparison with other analytical methods  

NASA Astrophysics Data System (ADS)

Sulfur and chlorine are essential elements in the metabolic processes of ruminants, and correct planning strategy of ruminant nutrition should provide a sufficient content of S and Cl in the animal's body. S and Cl can be found in various types of animal fodder in the form of organic compounds and minerals. In this work, the Cl and S content in forage was determined by X-ray fluorescence spectrometry (XRF), and its performance was then compared in parallel analyses by instrumental neutron activation analysis (INAA), inductively coupled plasma atomic emission spectrometry (ICP-AES) and potentiometric methods. The results were compared and critically evaluated in order to assess the performance and capability of the XRF technique in analysis of animal fodder.

Ne?emer, Marijan; Kump, Peter; Raj?evi?, Marija; Ja?imovi?, Radojko; Budi?, Bojan; Ponikvar, Maja

2003-07-01

315

X-ray Power Spectral Densities of Mkn 79 and NGC 4593 using Markov Chain Monte Carlo  

NASA Astrophysics Data System (ADS)

Strong and highly variable X-ray emission is one of the defining characteristics of active galaxies. The power spectrum of the light curve typically takes the form of a broken power law, with the break frequency closely related to the black hole mass and accretion rate. Previous efforts to measure the break frequency involved Monte Carlo simulations which are often computationally intensive, and do not provide a clear estimate of errors for parameters. Here we apply Markov Chain Monte Carlo methods to estimate the power spectra of 2 objects, Mkn 79 and NGC 4593. Break frequencies are clearly detected in each object. For NGC 4593 the detected break frequency is close to the expected value. However for Mkn 79, the measured break timescale is significantly shorter than expectations. This may be due to variability arising in a truncated accretion disk. We also discuss in detail the method used to calculate each power spectrum, along with interpretation of the results and their uncertainties.

Marshall, Kevin

2015-01-01

316

Spectral observation of the soft X-ray background and of the North Polar Spur with solid state spectrometers  

NASA Technical Reports Server (NTRS)

Soft X-ray diffuse background observations in the 0.3-1.5 keV interval of two sky regions, near the north galactic pole and the North Polar Spur (NPS) are reported. Data were taken with a solid-state spectrometer carried by a rocket. The near-polar region exhibited O VII ion emissions at 530 eV. A second component was not identified but was attributed to the Galactic Halo. Fe XVIII, Ne IX, and O VIII contributions were detected in the NPS, along with an enhancement at 1.35 keV from Mg XI lines. A two-temperature contour was fit to the spectra and chi-square confidence levels of 90 and 68 percent were obtained.

Rocchia, R.; Arnaud, M.; Blondel, C.; Cheron, C.; Christy, J. C.; Koch, L.; Rothenflug, R.; Schnopper, H. W.; Delvaille, J. P.

1983-01-01

317

On the Nature of the Variability Power Decay towards Soft Spectral States in X-Ray Binaries. Case Study in Cyg X-1  

NASA Technical Reports Server (NTRS)

A characteristic feature of the Fourier Power Density Spectrum (PDS) observed from black hole X-ray binaries in low/hard and intermediate spectral states is a broad band-limited noise, characterized by a constant below some frequency (a "break" frequency) and a power law above this frequency. It has been shown that the variability of this type can be produced by the inward diffusion of the local driving perturbations in a bounded configuration (accretion disk or corona). In the framework of this model, the perturbation diffusion time to is related to the phenomenological break frequency, while the PDS power-law slope above the "break" is determined by the viscosity distribution over the configuration. The perturbation diffusion scenario explains the decay of the power of X-ray variability observed in a number of compact sources (containing black hole and neutron star) during an evolution of theses sources from low/hard to high/soft states. We compare the model predictions with the subset of data from Cyg X-1 collected by the Rossi X-ray Time Explorer (RXTE). Our extensive analysis of the Cyg X-1 PDSs demonstrates that the observed integrated power P(sub x), decreases approximately as a square root of the characteristic frequency of the driving oscillations v(sub dr). The RXTE observations of Cyg X-1 allow us to infer P(sub dr), and t(sub o) as a function of v(sub dr). We also apply the basic parameters of observed PDSs, power-law index and low frequency quasiperiodic oscillations. to infer Reynolds (Re) number from the observations using the method developed in our previous paper. Our analysis shows that Re-number increases from values about 10 in low/hard state to that about 70 during the high/soft state. Subject headings: accretion, accretion disks-black hole physics-stars:individual (Cyg X-1) :radiation mechanisms: nonthermal-physical data and processes

Titarchuk, Lev; Shaposhinikov, Nikolai

2007-01-01

318

X-ray Flares from Markarian 501  

E-print Network

Motivated by the recent finding of hierarchical X-ray flaring phenomenon in Mrk 421, we conducted a systematic search for X-ray flares from Mrk 501, another well-known TeV blazar, by making use of the rich {\\em RXTE} archival database. We detected flares over a wide range of timescales, from months down to minutes, as in the case of Mrk 421. However, the flares do not seem to occur nearly as frequently in Mrk 501 as in Mrk 421 on any of the timescales. The flaring hierarchy also seems apparent in Mrk 501, suggesting that it might be common among TeV blazars. The results seem to imply a scale-invariant physical origin of the flares (large or small). The X-ray spectrum of the source shows a general trend of hardening toward the peak of long-duration flares, with indication of spectral hysteresis, which is often seen in TeV blazars. However, the data are not of sufficient quality to allow us to draw definitive conclusions about spectral variability associated with more rapid but weaker flares. We critically examine a reported sub-hour X-ray flare from Mrk 501, in light of intense background flaring activity at the time of the observation, and concluded that the flare is likely an artifact. On the other hand, we did identify a rapid X-ray flare that appears to be real. It lasted only for about 15 minutes, during which the flux of the source varied by about 30%. Sub-structures are apparent in its profile, implying variabilities on even shorter timescales. Such rapid variabilities of Mrk 501 place severe constraints on the physical properties of the flaring region in the jet, which have serious implications on the emission models proposed for TeV blazars.

Yongquan Xue; Wei Cui

2004-12-09

319

The feasibility of independent observations/detections of GRBs in X-rays  

NASA Astrophysics Data System (ADS)

According to the observational statistics a large majority of all GRBs exhibit X-ray emission. In addition, a dedicated separate group of GRB, the XRFs, exists which emission dominates in the X-ray spectral range. And the third group of GRB related objects (yet hypothetical) are the group of off-axis observed GRBs (orphan afterglows). These facts justify the consideration of an independent experiment for monitoring, detection and analyses of GRBs and others fast X-ray transients in X-rays. We will present and discuss such experiment based on wide-field X-ray telescopes of Lobster Eye type. The wide field and fine sensitivity of Lobster Eye X-ray All-Sky Monitor make such instruments important tools in study of GRBs and related objects.

Hudec, R.; Pina, L.; Marsikova, V.; Inneman, A.; Skulinova, M.

2011-08-01

320

The feasibility of independent observations/detections of GRBs in X-rays  

NASA Astrophysics Data System (ADS)

According to the observational statistics a large majority of all GRBs exhibit X-ray emission. In addition, a dedicated separate group of GRB, the XRFs, exists which emission dominates in the X-ray spectral range. And the third group of GRB related objects (yet hypothetical) are the group of off-axis observed GRBs (orphan afterglows). These facts justify the consideration of an independent experiment for monitoring, detection and analyses of GRBs and others fast X-ray transients in X-rays. We will present and discuss such experiment based on wide-field X-ray telescopes of Lobster Eye type. The wide field and fine sensitivity of Lobster Eye X-ray All-Sky Monitor make such instruments important tools in study of GRBs and related objects.

Hudec, R.; Pina, L.; Sveda, L.; Semencova, V.; Inneman, A.; Skulinova, M.

2009-05-01

321

The feasibility of independent observations/detections of GRBs in X-rays  

SciTech Connect

According to the observational statistics a large majority of all GRBs exhibit X-ray emission. In addition, a dedicated separate group of GRB, the XRFs, exists which emission dominates in the X-ray spectral range. And the third group of GRB related objects (yet hypothetical) are the group of off-axis observed GRBs (orphan afterglows). These facts justify the consideration of an independent experiment for monitoring, detection and analyses of GRBs and others fast X-ray transients in X-rays. We will present and discuss such experiment based on wide-field X-ray telescopes of Lobster Eye type. The wide field and fine sensitivity of Lobster Eye X-ray All-Sky Monitor make such instruments important tools in study of GRBs and related objects.

Hudec, R.; Skulinova, M. [Astronomical Institute, Academy of Sciences of the Czech Republic, 251 65 Ondrejov (Czech Republic); Pina, L.; Sveda, L. [Czech Technical University, Prague (Czech Republic); Semencova, V.; Inneman, A. [Rigaku Innovative Techniologies Europe, Prague (Czech Republic)

2009-05-25

322

The Implementation of an Imaging X-Ray Spectrometer for the International X-Ray Observatory  

NASA Astrophysics Data System (ADS)

We are studying the implementation of a high-resolution x-ray imaging spectrometer for the International X-Ray Observatory (IXO) based on an array of transition edge sensor calorimeters. This technology has shown excellent potential for meeting the observatory requirements for high spectral resolution over a wide range of energies (0.1-10 keV), and with pixel sizes matched to the performance of the x-ray mirror for true imaging x-ray spectroscopy over a field of view of 5 x 5 arcmin. The array will consist of a 40 x 40 central core that has 3 arcsec pixels with better than 2.5 eV spectral resolution (corresponding to a resolving power of over 2400 at 6 keV, the energy of the abundant Fe K emission complex.) This will be surrounded by an outer array with 52 pixels on a side, each subtending 6 arcsec, that will extend the field of view to 5.4 arcmin. To read out the array, we will use a multiplexed SQUID system to reduce the wire count and heat loads to the cryogenic system. The outer array will be multiplexed further in a sense by having four x-ray absorbers coupled to a single SQUID amplifier. The operating temperature of 0.1K for the array will be maintained by a cryogen-free system based on a multi-stage ADR and mechanical cooler (pulse tube for our present study, but a Joule-Thomson cooler is also viable.) This system will provide continuous operation for more than five years. In this poster we will illustrate the IXO calorimeter spectrometer design and give the expected system performance for high resolution imaging x-ray spectroscopy.

Kelley, Richard L.; Doriese, W.; Bandler, S. R.; Brekosky, R. P.; Brown, A.; Chervenak, J. A.; DiPirro, M. J.; Eckart, M. E.; Finkbeiner, F. M.; Hilton, G. C.; Irwin, K. D.; Kilbourne, C. A.; Porter, F.; Reintsema, C. D.; Shirron, P.; Smith, S. J.; Ullom, J. N.; Whitehouse, P. L.

2009-01-01

323

Short-range order in Fe-based metallic glasses: Wide-angle X-ray scattering studies  

NASA Astrophysics Data System (ADS)

The local atomic structure of the Fe80B20, Fe70Nb10B20 and Fe62Nb8B30 glasses prepared in the form of ribbons has been studied by wide-angle X-ray scattering. Structural information about the amorphous ribbons has been derived from analysis of the radial distribution functions using the least-squares curve-fitting method. The obtained structural parameters indicate that Fe-Fe, Fe-B, Fe-Nb and Nb-B contributions are involved in the near-neighbor coordination spheres. The possible similarities of the local atomic arrangement in the investigated glasses and the crystalline Fe3B, Fe23B6 and bcc Fe structures are also discussed.

Babilas, Rafa?; Hawe?ek, ?ukasz; Burian, Andrzej

2014-11-01

324

Phase unwrapping in spectral x-ray differential phase-contrast imaging with an energy-resolving photon-counting pixel detector.  

PubMed

Grating-based differential phase-contrast imaging has proven to be feasible with conventional X-ray sources. The polychromatic spectrum generally limits the performance of the interferometer but benefit can be gained with an energy-sensitive detector. In the presented work, we employ the energy-discrimination capability to correct for phasewrapping artefacts. We propose to use the phase shifts, which are measured in distinct energy bins, to estimate the optimal phase shift in the sense of maximum likelihood. We demonstrate that our method is able to correct for phasewrapping artefacts, to improve the contrast-to-noise ratio and to reduce beam hardening due to the modelled energy dependency. The method is evaluated on experimental data which are measured with a laboratory Talbot-Lau interferometer equipped with a conventional polychromatic X-ray source and an energy-sensitive photon-counting pixel detector. Our work shows, that spectral imaging is an important step to move differential phase-contrast imaging closer to pre-clinical and clinical applications, where phase wrapping is particularly problematic. PMID:25163054

Epple, Franz M; Ehn, Sebastian; Thibault, Pierre; Koehler, Thomas; Potdevin, Guillaume; Herzen, Julia; Pennicard, David; Graafsma, Heinz; Noel, Peter B; Pfeiffer, Franz

2014-08-21

325

Modeling the Radio to X-ray SED of Galaxies  

E-print Network

Our multi-wavelength model GRASIL for the SED of galaxies is described, in particular the recent extension to the radio and X-ray range. With our model we can study different aspects of galaxy evolution by exploiting all available spectral observations, where different emission components dominate.

L. Silva; G. L. Granato; A. Bressan; P. Panuzzo

2002-08-17

326

Multiscale spectral mapping of the physical properties of the X-ray emitting gas within groups and clusters of galaxies.  

NASA Astrophysics Data System (ADS)

Clusters and groups of galaxies have formed by accreting substructures located along the filamentary overdensities of the Universe. They sucessively have undergo merging processes of subgroups and relaxation phases, leading to close to self-graviting structures. The physical properties of the X-ray emitting Intra-Cluster and Intra-Group Medium (ICM-IGM), such as its temperature, entropy and metallicity are strongly affected by the non gravitationnal heating and cooling processes, but also the mixing processes occuring during the lifetime of the clusters and groups of galaxies. The ultimate advanced X-ray telescopes Chandra and XMM-Newton now enable to map these properties with unprecedented accuracy. In order to exploit the new capabilities of these telescopes, we have developped a new multi-scale spectro-imagery algorithm so as to map the spatial distribution of the ICM-IGM properties. The today algorithm has been designed for analyzing data from the EPIC MOS1, MOS2 and PN spectro-imagers on board of the XMM-Newton telescope, but future developpments concerning the Chandra telescope are planned. The algorithm basically works in two steps. First of all, the mapped parameter is locally estimated within square resolution elements at different scales following a dyadic scheme. To do so, a minimum variance estimator enables to fit an emission model to the data set, even in case of quite poor statistics, taking into account the local instrumental response and backgrounds. Then spatial variations of the parameter are coded in the wavelet space which enables an accurate and optimal de-noising of the map. The algorithm has been tested on a series of toy-model EPIC-XMM observations, as well as on simulated observations of numerically simulated merging clusters, evidencing an unprecedented ability to map accurately the temperature variations of the ICM occuring in such a context due to shock waves, shock fronts and cold cores (Bourdin et al., A&A, 414, 429). It is now used in the framework of a systematic study of a sample of bright merging clusters observed by the XMM-Newton telescope at different stages of the merging process, where various shock and gas heating processes have been investigated and associated with collisions at different time scales, thanks to a combined 1-D/2-D analysis of the ICM temperature and entropy distributions (see also Belsole et al., this conference).

Bourdin, H.; Sauvageot, J. L.; Slezak, E.; Bijaoui, A.; Belsole, E.; Pratt, G. W.; Teyssier, R.

327

X ray imaging microscope for cancer research  

NASA Technical Reports Server (NTRS)

The NASA technology employed during the Stanford MSFC LLNL Rocket X Ray Spectroheliograph flight established that doubly reflecting, normal incidence multilayer optics can be designed, fabricated, and used for high resolution x ray imaging of the Sun. Technology developed as part of the MSFC X Ray Microscope program, showed that high quality, high resolution multilayer x ray imaging microscopes are feasible. Using technology developed at Stanford University and at the DOE Lawrence Livermore National Laboratory (LLNL), Troy W. Barbee, Jr. has fabricated multilayer coatings with near theoretical reflectivities and perfect bandpass matching for a new rocket borne solar observatory, the Multi-Spectral Solar Telescope Array (MSSTA). Advanced Flow Polishing has provided multilayer mirror substrates with sub-angstrom (rms) smoothnesss for the astronomical x ray telescopes and x ray microscopes. The combination of these important technological advancements has paved the way for the development of a Water Window Imaging X Ray Microscope for cancer research.

Hoover, Richard B.; Shealy, David L.; Brinkley, B. R.; Baker, Phillip C.; Barbee, Troy W., Jr.; Walker, Arthur B. C., Jr.

1991-01-01

328

Chest x-ray  

MedlinePLUS

Chest radiography; Serial chest x-ray; X-ray - chest ... You stand in front of the x-ray machine. You will be told to hold your breath when the x-ray is taken. Two images are usually taken. You will need ...

329

X-Ray Imaging  

Cancer.gov

X-ray imaging is perhaps the most familiar type of imaging. Images produced by X-rays are due to the different absorption rates of different tissues. Calcium in bones absorbs X-rays the most, so bones look white on a film recording of the X-ray image,

330

The ASTRO-H Mission: Unprecedented Spectral Coverage in the X-ray and Soft Gamma-Ray Bands  

NASA Astrophysics Data System (ADS)

Following in the footsteps of the ASCA and Suzaku satellites, the joint Japan-US-European ``ASTRO-H" space mission is considerably more ambitious and represents a major step forward in our ability to study the high-energy universe. Construction of the satellite is well underway, with an anticipated launch date in late 2015. The unprecedented suite of instruments on Astro-H enables simultaneous observations covering 0.1 to 600 keV, including: calorimeter (~5 eV) energy resolution in the 6-7 keV iron line band, good angular resolution and sensitivity, comparable to NuSTAR, at higher energies due to hard X-ray focusing optics, and significant polarization sensitivity above ~50 keV provided by Compton camera electronics. Here we present examples of the spectra expected in a typical 100 kilosecond observation for several classes of sources, focusing on how the combination of Astro-H's instruments enables us to finally break several of the degeneracies that currently hamper modeling efforts for these sources.

Astro-H Collaboration

2015-01-01

331

Spectral observations of the soft X-ray background with solid-state detectors - Evidence for line emissions  

NASA Technical Reports Server (NTRS)

The soft X-ray radiation from several regions of the sky was observed with solid-state detectors Si(Li) between 0.3 and 1.2 keV during two rocket flights. The thermal nature of the diffuse emission coming from the hot bubble surrounding the solar system is confirmed by the observation of C V-C VI and O VII lines which are typical of a temperature of about 10 to the 6th K. Evidence for the existence of a weak component at a higher temperature is given. This component, well visible in the high latitude spectra, could be produced by a hot galactic halo. In the direction of the enhancement region centered on the North Polar Spur, the radiation excess spectra are well represented by a two-temperature plasma model with rather standard abundances. The two components have temperatures of 10 to the 6th and 4.7 x 10 to the 6th K.

Rocchia, R.; Arnaud, M.; Blondel, C.; Cheron, C.; Christy, J. C.; Rothenflug, R.; Schnopper, H. W.; Delvaille, J. P.

1984-01-01

332

On the Radio/X-ray Correlation in Microquasars  

E-print Network

[Context] The broadband spectral energy distribution of microquasars has proven to be a valuable tool for assessing the roles of jets and accretion flows in microquasars, as well as the coupling between the two. The coupling might manifest itself observationally in the correlated radio and X-ray variabilities of a source. Such a radio/X-ray correlation has indeed been seen in several microquasars during the low-hard state and subsequently been claimed to be universal for all. If proven, the universal correlation would have profound implications on theoretical models. However, there is already observational evidence that suggests otherwise. [Aims] In this paper, we critically examine the radio/X-ray correlation in a sample of microquasars, in the low-hard state as well as during state transitions, with a goal of testing the claimed universality of the correlation on observational grounds. [Methods] We have assembled a comprehensive data set from the simultaneous/contemporaneous radio and X-ray observations of representative microquasars. The data have allowed us to quantify the radio/X-ray correlation on a source by source basis. [Results] We find that the radio/X-ray correlation of microquasars exhibits diverse behaviors, both in the low-hard and transitional states, ranging from being very week (or none at all) to very strong. There is even a hint of spectral dependence of the correlation in some cases. [Conclusions] Our results rule out the claimed universality of the radio/X-ray correlation of microquasars, even for the low-hard state. On the other hand, we do find that the radio and X-ray variabilities are, to varying degrees, correlated in most cases.

Yongquan Xue; Wei Cui

2007-02-26

333

Circinus X-1: a Laboratory for Studying the Accretion Phenomenon in Compact Binary X-Ray Sources. Ph.D. Thesis - Maryland Univ.  

NASA Technical Reports Server (NTRS)

Observations of the binary X-ray source Circinus X-1 provide samples of a range of spectral and temporal behavior whose variety is thought to reflect a broad continuum of accretion conditions in an eccentric binary system. The data support an identification of three or more X-ray spectral components, probably associated with distinct emission regions.

Robinson-Saba, J. L.

1983-01-01

334

A Unified Timing and Spectral Model for the Anomalous X-ray Pulsars XTE J1810-197 and CXOU J164710.2-455216  

NASA Astrophysics Data System (ADS)

Anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs) are two small classes of X-ray sources strongly suspected to host a magnetar, i.e., an ultra-magnetized neutron star with B ? 1014-1015 G. Many SGRs/AXPs are known to be variable, and recently the existence of genuinely "transient" magnetars was discovered. Here, we present a comprehensive study of the pulse profile and spectral evolution of the two transient AXPs (TAXPs) XTE J1810-197 and CXOU J164710.2-455216. Our analysis was carried out in the framework of the twisted magnetosphere model for magnetar emission. Starting from three-dimensional Monte Carlo simulations of the emerging spectrum, we produced a large database of synthetic pulse profiles which was fitted to observed light curves in different spectral bands and at different epochs. This allowed us to derive the physical parameters of the model and their evolution with time, together with the geometry of the two sources, i.e., the inclination of the line of sight and the magnetic axis with respect to the rotation axis. We then fitted the (phase-averaged) spectra of the two TAXPs at different epochs using a model similar to that used to calculate the pulse profiles (ntzang in XSPEC) freezing all parameters to the values obtained from the timing analysis and leaving only the normalization free to vary. This provided acceptable fits to XMM-Newton data in all the observations we analyzed. Our results support a picture in which a limited portion of the star surface close to one of the magnetic poles is heated at the outburst onset. The subsequent evolution is driven both by the cooling/varying size of the heated cap and by a progressive untwisting of the magnetosphere.

Albano, A.; Turolla, R.; Israel, G. L.; Zane, S.; Nobili, L.; Stella, L.

2010-10-01

335

Long-range structure of Cu(InxGa1-x)3Se5: A complementary neutron and anomalous x-ray diffraction study  

NASA Astrophysics Data System (ADS)

Distinguishing the scattering contributions of isoelectronic atomic species by means of conventional x-ray- and/or electron diffraction techniques is a difficult task. Such a problem occurs when determining the crystal structure of compounds containing different types of atoms with equal number of electrons. We propose a new structural model of Cu(InxGa1-x)3Se5 which is valid for the entire compositional range of the CuIn3Se5-CuGa3Se5 solid solution. Our model is based on neutron and anomalous x-ray diffraction experiments. These complementary techniques allow the separation of scattering contributions of the isoelectronic species Cu+ and Ga3+, contributing nearly identically in monoenergetic x-ray diffraction experiments. We have found that CuIII3Se5 (III=In,Ga) in its room temperature near-equilibrium modification exhibits a modified stannite structure (space group I4¯2m). Different occupation factors of the species involved, Cu+, In3+, Ga3+, and vacancies have been found at three different cationic positions of the structure (Wyckoff sites 2a, 2b, and 4d) depending on the composition of the compound. Significantly, Cu+ does not occupy the 2b site for the In-free compound, but does for the In-containing case. Structural parameters, including lattice constants, tetragonal distortions, and occupation factors are given for samples covering the entire range of the CuIn3Se5-CuGa3Se5 solid solution. At the light of the result, the denotation of Cu-poor 1:3:5 compounds as chalcopyrite-related materials is only valid in reference to their composition.

Lehmann, S.; Marrón, D. fürtes; León, M.; Feyerherm, R.; Dudzik, E.; Friedrich, E. J.; Tovar, M.; Tomm, Y.; Wolf, C.; Schorr, S.; Schedel-Niedrig, Th.; Lux-Steiner, M. Ch.; Merino, J. M.

2011-01-01

336

An evaluation of multilayer mirrors for the soft x ray and extreme ultraviolet wavelength range that were irradiated with neutrons  

NASA Astrophysics Data System (ADS)

The Plasma Spectroscopy Group at the Johns Hopkins University develops high photon throughput multilayer mirror (MLM) based soft x ray and extreme ultraviolet (XUV 10 Å

Regan, S. P.; May, M. J.; Soukhanovskii, V.; Finkenthal, M.; Moos, H. W.; Farnum, E. H.; Clinard, F. W., Jr.; Tarrio, C.; Watts, R.

1997-01-01

337

BESSY soft X-ray FEL  

NASA Astrophysics Data System (ADS)

The BESSY soft X-ray FEL is planned as a linac-based single pass FEL multi user facility covering the VUV to soft X-ray spectral range (0.02 keV????1 keV) [1,2]. A Photoinjector and a superconducting CW linac [3] will feed three independent SASE-FEL-lines consisting of APPLE II type undulators providing variable polarized radiation [2,4]. The performance of the SASE-FEL can be enhanced using a coherent seed which dominates the spontaneous emission at the beginning of the process. We present simulation studies for three BESSY-SASE-FELs as well as for possible multistage high-gain harmonic generation (HGHG) FELs and discuss their performance in terms of pulse power, pulse duration, pulse shape and signal-to-noise ratio.

Meseck, A.; Abo-Bakr, M.; Krämer, D.; Kuske, B.; Reiche, S.

2004-08-01

338

An advanced multivariate approach for processing X-ray fluorescence spectral and hyperspectral data from non-invasive in situ analyses on painted surfaces.  

PubMed

In the last decades, in situ non-invasive analytical techniques have been widely used for the analysis of paintings. These techniques are useful to extensively map the surface in a non-invasive way, in order to identify the most representative areas to be sampled. When spectroscopic investigations, such as X ray fluorescence (XRF), are conducted, they usually imply the acquisition of a huge amount of measurements. Subsequently, all these data should be processed in situ, in order to immediately support the sampling strategies. To this aim, an appropriate and fast strategy for multivariate treatment of XRF spectral and hyperspectral data sets is presented, able to account for inter-correlation among variables, which is an issue of high importance for elemental analyses. The main advantage of the approach is that XRF spectral profiles are analysed directly, without computation of derived parameters, by means of principal component analysis (PCA). This procedure allows a fast interpretation of results that can be accomplished in situ. Particular attention was paid to the selection of proper spectral pre-treatments to be applied on data together with the use of several chemometric tools (peak alignment, spectra normalisation and exploratory analysis) aimed at improving the interpretation of XRF results. In addition, the application of multivariate exploratory analysis on XRF hyperspectral maps was studied by using an interactive brushing procedure. The multivariate approach was validated on data obtained from the analysis of the famous Renaissance panel painting "The Ideal City", exhibited in Palazzo Ducale of Urbino, Italy. PMID:23101649

Sciutto, Giorgia; Oliveri, Paolo; Prati, Silvia; Quaranta, Marta; Bersani, Silvia; Mazzeo, Rocco

2012-11-01

339

X-ray--luminous, IR-selected H II Galaxies and the X-ray Background  

NASA Astrophysics Data System (ADS)

No known class of extragalactic X-ray sources has been shown conclusively to have the properties necessary to explain the origin of the cosmic X-ray background (XRB). It has been suggested that star-forming galaxies could make a significant contribution to the XRB, and a convincing scenario for how these galaxies could have both high individual luminosities and the hard X-ray spectra required for such a contribution has been proposed (Griffiths & Padovani 1990). We have employed the Einstein, ROSAT, and ASCA observatories to examine this proposal. Recently, a sample of 242 IR-selected ROSAT sources was published and the discovery of a new class of X-ray--luminous normal spiral galaxies (20 objects) was claimed (Boller et al. 1992). In addition to reexamining the classifications of 17 of these 20 objects, we have obtained optical spectra for 87 of the unclassified objects from the Boller et al. sample and for 53 IR-selected objects from a new catalog of faint Einstein sources. The majority of the objects observed are AGNs. While there appear to be a few H II galaxies with high X-ray luminosities (> 10(42) ergs s(-1) ), only one of these, NGC 3256, is a confirmed X-ray source. An ASCA observation of NGC 3256 indicates that its broad-band spectrum is very soft and that its true X-ray luminosity is at most 5 times 10(41) ergs s(-1) (.4 - 8 keV). Thus, there is no evidence for a class of X-ray--luminous H II galaxies in these samples. Furthermore, the X-ray spectrum of NGC 3256 indicates that it and similar objects do not have the spectral characteristics necessary to explain the spectrum of the XRB. The most promising discovery in this survey is a substantial number of H II/Seyfert composite galaxies. Their optical spectra are dominated by starburst characteristics; however, broad [O III] lines and sometimes very faint, broad H? emission betray their true Seyfert identities. Yet these optically innocuous galaxies have L_X in the range 10(42.7}-10({43.7)) ergs s(-1) , typical for bright Seyfert 1 galaxies. The nature of these galaxies and their contribution to the XRB must be studied further.

Moran, Edward C.

1994-12-01

340

X-Ray Vision  

NASA Technical Reports Server (NTRS)

We are fabricating optics for the hard-x-ray region using electroless nickel replication. The attraction of this process, which has been widely used elsewhere, is that the resulting full shell optics are inherently stable and thus can have very good angular resolution. The challenge with this process is to develop lightweight optics (nickel has a relatively high density of 8.9 g/cu cm), and to keep down the costs of mandrel fabrication. We accomplished the former through the development of high-strength nickel alloys that permit very thin shells without fabrication- and handling-induced deformations. For the latter, we have utilized inexpensive grinding and diamond turning to figure the mandrels and then purpose-built polishing machines to finish the surface. In-house plating tanks and a simple water-bath separation system complete the process. To date we have built shells ranging in size from 5 cm diameter to 50 cm, and with thickness down to 100 micron. For our HERO balloon program, we are fabricating over 200 iridium-coated shells, 250 microns thick, for hard-x-ray imaging up to 75 keV. Early test results on these have indicated half-power-diameters of 15 arcsec. The status of these and other hard-x-ray optics will be reviewed.

Ramsey, B. D.; Elsner, R. F.; Engelhaupt, D.; Kolodziejczak, J. J.; ODell, S. L.; Speegle, C. O.; Weisskopf, M. C.

2004-01-01

341

Nanoscale X-ray imaging  

Microsoft Academic Search

Recent years have seen significant progress in the field of soft- and hard-X-ray microscopy, both technically, through developments in source, optics and imaging methodologies, and also scientifically, through a wide range of applications. While an ever-growing community is pursuing the extensive applications of today's available X-ray tools, other groups are investigating improvements in techniques, including new optics, higher spatial resolutions,

Anne Sakdinawat; David Attwood

2010-01-01

342

Developing a Compton Polarimeter to Measure Polarization of Hard X-Rays in the 50-300 keV Energy Range  

E-print Network

This paper discusses the latest progress in the development of GRAPE (Gamma-Ray Polarimeter Experiment), a hard X-ray Compton Polarimeter. The purpose of GRAPE is to measure the polarization of hard X-rays in the 50-300 keV energy range. We are particularly interested in X-rays that are emitted from solar flares and gamma-ray bursts (GRBs). Accurately measuring the polarization of the emitted radiation from these sources will lead, to a better understating of both the emission mechanisms and source geometries. The GRAPE design consists of an array of plastic scintillators surrounding a central high-Z crystal scintillator. We can monitor individual Compton scatters that occur in the plastics and determine whether the photon is photo absorbed by the high-Z crystal or not. A Compton scattered photon that is immediately photo absorbed by the high-Z crystal constitutes a valid event. These valid events provide us with the interaction locations of each incident photon and ultimately produces a modulation pattern for the Compton scattering of the polarized radiation. Comparing with Monte Carlo simulations of a 100% polarized beam, the level of polarization of the measured beam can then be determined. The complete array is mounted on a flat-panel multi-anode photomultiplier tube (MAPMT) that can measure the deposited energies resulting from the photon interactions. The design of the detector allows for a large field-of-view (>pi steradian), at the same time offering the ability to be close-packed with multiple modules in order to reduce deadspace. We plan to present in this paper the latest laboratory results obtained from GRAPE using partially polarized radiation sources.

J. S. Legere; P. Bloser; J. R. Macri; M. L. McConnell; T. Narita; J. M. Ryan

2005-08-14

343

A complementary dual-slope ADC with high frame rate and wide input range for fast X-ray imaging  

NASA Astrophysics Data System (ADS)

The single-slope analog-to-digital converter (SS-ADC) is the most commonly used column-level ADC for high-speed industrial, complementary metal-oxide semiconductor (CMOS)-based X-ray image sensors because of its small chip area (the width of a pixel), its simple circuit structure, and its low power consumption. However, it generally has a long conversion time, so we propose an innovative design: a complimentary dual-slope ADC (CDS-ADC) that uses two opposite ramp signals instead of a single ramp to double the conversion speed. This CDS-ADC occupies only 15% more area than the original SS-ADC. A prototype 12-bit CDS-ADC and a 12-bit SS-ADC were fabricated using a 0.35-µm 1P 4M CMOS process. During comparison of the two, the measured maximum differential non-linearity (DNL) of the CDS-ADC was a 0.49 least significant bit (LSB), the maximum integral non-linearity (INL) was a 0.43 LSB, the effective number of bits (ENOB) was 9.18 bits, and the figure of merit (FOM) was 0.03 pJ/conversion. The total power consumption was 0.031 uW. The conversion time of the new CDS-ADC was half that of the SS-ADC. The proposed dual-slope concept can be extended to further multiply the conversion speed by using multiple pairs of dual-slope ramps.

Lee, Daehee; Cho, Minsik; Kang, Dong-Uk; Kim, Myung Soo; Kim, Hyunduk; Cho, Gyuseong

2014-02-01

344

X-ray Flaring Activity of Mrk 421  

E-print Network

We report results from a systematic search for X-ray flares from Mrk 421, using archival data from the Rossi X-ray Timing Explorer (RXTE) satellite. The flares are clearly seen over a wide range of timescales. The quasi-continuous coverage of the source with the All-Sky Monitor (ASM) reveals frequent occurrence of major flares that last for months. On a few occasions, the source was intensively monitored with the more sensitive pointing instruments aboard RXTE. The data from these observations shows the presence of X-ray flares of much shorter durations, ranging from weeks down to less than an hour. For the first time, we clearly resolved the sub-hour flares from Mrk 421. Moreover, Fourier analyses reveal variability on even shorter timescales, up to about 0.01 Hz. The source appears to behave differently in its spectral properties during different flares, large or small, which is intriguing. While significant hysteresis is observed to be associated with spectral evolution in some cases, little is seen in other cases. Sometimes, the shape of the X-ray spectrum hardly varies across a flare. Therefore, the phenomenology is complex. The observed hierarchical structure of the X-ray flares seems to imply the scale-invariant nature of the phenomenon, perhaps similar to solar flares or rapid X-ray flares observed of stellar-mass black holes in this regard. Combined with other results, the observed flaring timescales seriously constrain the physical properties of X-ray emitting regions in the jets of Mrk 421.

Wei Cui

2004-01-12

345

Synchrotron x-ray microbeam characteristics for x-ray fluorescence analysis  

SciTech Connect

X-ray fluorescence analysis using a synchrotron x-ray microprobe has become an indispensable technique for non-destructive micro-analysis. One of the most important parameters that characterize the x-ray microbeam system for x-ray fluorescence analysis is the beam size. For practical analysis, however, the photon flux, the energy resolution and the available energy range are also crucial. Three types of x-ray microbeam systems, including monochromatic and continuum excitation systems, were compared with reference to the sensitivity, the minimum detection limit and the applicability to various types of x-ray spectroscopic analysis. 16 refs., 5 figs.

Iida, Atsuo; Noma, Takashi [National Laboratory for High Energy Physics, Ibaraki (Japan)

1995-12-31

346

The Focusing Optics Solar X-ray Imager (FOXSI)  

NASA Astrophysics Data System (ADS)

The Focusing Optics x-ray Solar Imager is a sounding rocket payload funded under the NASA Low Cost Access to Space program to test hard x-ray focusing optics and position-sensitive solid state detectors for solar observations. Today's leading solar hard x-ray instrument, the Reuven Ramaty High Energy Solar Spectroscopic Imager provides excellent spatial (2 arcseconds) and spectral (1~keV) resolution. Yet, due to its use of indirect imaging, the derived images have a low dynamic range (<30) and sensitivity. These limitations make it difficult to study faint x-ray sources in the solar corona which are crucial for understanding the solar flare acceleration process. Grazing-incidence x-ray focusing optics combined with position-sensitive solid state detectors can overcome both of these limitations enabling the next breakthrough in understanding particle acceleration in solar flares. The foxsi project is led by the Space Science Laboratory at the University of California. The NASA Marshall Space Flight Center, with experience from the HERO balloon project, is responsible for the grazing-incidence optics, while the Astro H team (JAXA/ISAS) will provide double-sided silicon strip detectors. FOXSI will be a pathfinder for the next generation of solar hard x-ray spectroscopic imagers. Such observatories will be able to image the non-thermal electrons within the solar flare acceleration region, trace their paths through the corona, and provide essential quantitative measurements such as energy spectra, density, and energy content in accelerated electrons.

Christe, S.; Glesener, L.; Krucker, S.; Ramsey, B.; Ishikawa, S.; Takahashi, T.

2009-12-01

347

The discrete X-ray source population in M31  

NASA Technical Reports Server (NTRS)

Results of an analysis of the complete set of Einstein imaging observations of M31 are reported. One-hundred-eight individual X-ray sources are detected, with (0.2-4.0 keV) luminosities ranging from 5 x 10 exp 36 ergs/s to above 10 exp 38 ergs/s at the distance of M31. Fourteen of these sources are luminous enough to perform a spectral fit of the X-ray data. Fourteen sources are found to vary between Einstein observations, in addition to the two sources already reported by Collura, Reale, and Peres (1990). Contrary to earlier reports, no substantial difference is found between the luminosity distributions of X-ray sources in the bulge and in the disk. Contour maps of the X-ray emission in the central region is presented, and the radial distribution of the surface brightness is compared with the optical profiles. It is inferred that the disk is relatively underluminous in X-rays, relative to the stellar content. The spatial distribution of bulge sources is compared with that of optical novae and with emission-like images of the bulge. These comparisons constrain models of the formation of low-mass X-ray binaries.

Trinchieri, G.; Fabbiano, G.

1991-01-01

348

Quantitative extraction of spectral line intensities and widths from x-ray spectra recorded with gated microchannel plate detectors  

SciTech Connect

Plasma spectroscopy requires determination of spectral line intensities and widths. At Sandia National Laboratories Z facility we use elliptical crystal spectrometers equipped with gated microchannel plate detectors to record time and space resolved spectra. We collect a large volume of data typically consisting of five to six snapshots in time and five to ten spectral lines with 30 spatial elements per frame, totaling to more than 900 measurements per experiment. This large volume of data requires efficiency in processing. We have addressed this challenge by using a line fitting routine to automatically fit each spectrum using assumed line profiles and taking into account photoelectron statistics to efficiently extract line intensities and widths with uncertainties. We verified that the random data noise obeys Poisson statistics. Rescale factors for converting film exposure to effective counts required for understanding the photoelectron statistics are presented. An example of the application of these results to the analysis of spectra recorded in Z experiments is presented.

Dunham, Greg; Bailey, J. E.; Rochau, G. A.; Lake, P. W.; Nielsen-Weber, L. B. [Ktech Corporation, 1300 Eubank Boulevard, SE Albuquerque, New Mexico 87123 (United States); Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-1196 (United States); Ktech Corporation, 1300 Eubank Boulevard, SE Albuquerque, New Mexico 87123 (United States)

2007-06-15

349

Miniature x-ray source  

DOEpatents

A miniature x-ray source utilizing a hot filament cathode. The source has a millimeter scale size and is capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature source consists of a compact vacuum tube assembly containing the hot filament cathode, an anode, a high voltage feedthru for delivering high voltage to the cathode, a getter for maintaining high vacuum, a connector for initial vacuum pump down and crimp-off, and a high voltage connection for attaching a compact high voltage cable to the high voltage feedthru. At least a portion of the vacuum tube wall is fabricated from highly x-ray transparent materials, such as sapphire, diamond, or boron nitride.

Trebes, James E. (Livermore, CA); Bell, Perry M. (Tracy, CA); Robinson, Ronald B. (Modesto, CA)

2000-01-01

350

SUZAKU VIEW OF X-RAY SPECTRAL VARIABILITY OF THE RADIO GALAXY CENTAURUS A: PARTIAL COVERING ABSORBER, REFLECTOR, AND POSSIBLE JET COMPONENT  

SciTech Connect

We observed a nearby radio galaxy, Centaurus A (Cen A), three times with Suzaku in 2009 and measured the wide-band X-ray spectral variability more accurately than previous measurements. The Cen A was in an active phase in 2009, and the flux became higher by a factor of 1.5-2.0 and the spectrum became harder than that in 2005. The Fe-K line intensity increased by 20%-30% from 2005 to 2009. The correlation of the count rate between the XIS 3-8 keV and PIN 15-40 keV band showed a complex behavior with a deviation from a linear relation. The wide-band X-ray continuum in 2-200 keV can be fitted with an absorbed power-law model plus a reflection component, or a power law with a partial covering Compton-thick absorption. The difference spectra between high and low flux periods in each observation were reproduced by a power law with a partial covering Compton-thick absorption. Such a Compton-thick partial covering absorber was observed for the first time in Cen A. The power-law photon index of the difference spectra in 2009 is almost the same as that of the time-averaged spectra in 2005, but steeper by {approx}0.2 than that of the time-averaged spectra in 2009. This suggests an additional hard power-law component with a photon index of <1.6 in 2009. This hard component could be a lower part of the inverse-Compton-scattered component from the jet, whose gamma-ray emission has recently been detected with the Fermi Large Area Telescope.

Fukazawa, Yasushi; Hiragi, Kazuyoshi; Yamazaki, Syoko; Mizuno, Motohiro; Hayashi, Kazuma; Hayashi, Katsuhiro; Nishino, Sho; Takahashi, Hiromitsu; Ohno, Masanori, E-mail: fukazawa@hep01.hepl.hiroshima-u.ac.jp [Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)

2011-12-20

351

Precise measurement of the lattice spacing of LaB{sub 6} standard powder by the x-ray extended range technique using synchrotron radiation  

SciTech Connect

We used the basis of the x-ray extended range technique to measure the lattice spacing of LaB{sub 6} standard powder samples relative to silicon 640b standard powder samples with an accuracy of 5x10{sup -5} A. Measurements were not constrained to one energy but were carried out over a 5 keV-20 keV energy range. These measurements used powder diffraction to determine the synchrotron beam energy, to diagnose discrepancies in the nominal calibrated beam energies, and to determine beam energy bandwidths as a function of energy. More specifically, this technique is able to yield a result independent of certain energy-dependent systematics and to yield the most accurate determination of the lattice spacing of NIST SRM 660 LaB{sub 6} standard powder so far undertaken. This has direct application to beam line energy calibration, structural evaluation, edge energy calibration, and lattice spacing determinations.

Chantler, C.T.; Tran, C.Q. [School of Physics, University of Melbourne, Victoria 3010 (Australia); Cookson, D.J. [ANSTO, Private Mail Bag 1, Menai, New South Wales 2234 (Australia); Chem-Mat-CARS-CAT (Sector 15, Building 434D), Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 6043 (United States)

2004-04-01

352

Intermediate-range order in water ices : nonresonant inelastic x-ray scatterig measurements and real-space full multiple scattering calculations.  

SciTech Connect

We report measurements of the nonresonant inelastic x-ray scattering (NRIXS) from the O 1s orbitals in ice Ih, and also report calculations of the corresponding spectra for ice Ih and several other phases of water ice. We find that the intermediate-energy fine structure may be calculated well using an ab initio real-space full multiple scattering approach and that it provides a strong fingerprint of the intermediate-range order for some ice phases. Both experiment and theory find that the intermediate-range fine structure, unlike the near-edge structure, is independent of momentum transfer (q) to very high q. These results have important consequences for future NRIXS measurements of high-pressure phases of ice.

Fister, T. T.; Nagel, K. P.; Vila, F. D.; Seidler, G. T.; Hamner, C.; Cross, J. O.; Rehr, J. J.; Univ. Washington; Washington State Univ.

2009-01-01

353

The Athena X-ray Observatory: observing luminous extragalactic transients  

NASA Astrophysics Data System (ADS)

The ESA Athena X-ray observatory will combine exceptionally high throughout with high spectral-energy resolution. Athena will revolutionize many aspects of high-energy astrophysics. Here we concentrate on the subject of time-domain astronomy. Many of the most powerful transient sources, including gamma-ray bursts and tidal disruptions events, are bright X-ray sources. Athena will be designed to have a fast-response capability, permitting efficient observations of many transients. We will summarize the proposed capability of the mission and illustrate science programs to study transients ranging from the most distant GRBs to nuclear activity in nearby galaxies.

O'Brien, P. T.; Jonker, Peter G

2014-08-01

354

The NIF x-ray spectrometer calibration campaign at Omega  

NASA Astrophysics Data System (ADS)

The calibration campaign of the National Ignition Facility X-ray Spectrometer (NXS) was carried out at the Omega laser facility. Spherically symmetric, laser-driven, millimeter-scale x-ray sources of K-shell and L-shell emission from various mid-Z elements were designed for the 2-18 keV energy range of the NXS. The absolute spectral brightness was measured by two calibrated spectrometers. We compare the measured performance of the target design to radiation hydrodynamics simulations.

Pérez, F.; Kemp, G. E.; Regan, S. P.; Barrios, M. A.; Pino, J.; Scott, H.; Ayers, S.; Chen, H.; Emig, J.; Colvin, J. D.; Bedzyk, M.; Shoup, M. J.; Agliata, A.; Yaakobi, B.; Marshall, F. J.; Hamilton, R. A.; Jaquez, J.; Farrell, M.; Nikroo, A.; Fournier, K. B.

2014-11-01

355

The NIF x-ray spectrometer calibration campaign at Omega.  

PubMed

The calibration campaign of the National Ignition Facility X-ray Spectrometer (NXS) was carried out at the Omega laser facility. Spherically symmetric, laser-driven, millimeter-scale x-ray sources of K-shell and L-shell emission from various mid-Z elements were designed for the 2-18 keV energy range of the NXS. The absolute spectral brightness was measured by two calibrated spectrometers. We compare the measured performance of the target design to radiation hydrodynamics simulations. PMID:25430189

Pérez, F; Kemp, G E; Regan, S P; Barrios, M A; Pino, J; Scott, H; Ayers, S; Chen, H; Emig, J; Colvin, J D; Bedzyk, M; Shoup, M J; Agliata, A; Yaakobi, B; Marshall, F J; Hamilton, R A; Jaquez, J; Farrell, M; Nikroo, A; Fournier, K B

2014-11-01

356

The SWIRE/Chandra Survey: The X-ray Sources  

NASA Astrophysics Data System (ADS)

We report a moderate-depth (70 ks), contiguous 0.7 deg2 Chandra survey in the Lockman Hole Field of the Spitzer/SWIRE Legacy Survey coincident with a completed, ultra-deep VLA survey with deep optical and near-infrared imaging in-hand. The primary motivation is to distinguish starburst galaxies and active galactic nuclei (AGNs), including the significant, highly obscured (log N H > 23) subset. Chandra has detected 775 X-ray sources to a limiting broadband (0.3-8 keV) flux ~4 × 10-16 erg cm-2 s-1. We present the X-ray catalog, fluxes, hardness ratios, and multi-wavelength fluxes. The log N versus log S agrees with those of previous surveys covering similar flux ranges. The Chandra and Spitzer flux limits are well matched: 771 (99%) of the X-ray sources have infrared (IR) or optical counterparts, and 333 have MIPS 24 ?m detections. There are four optical-only X-ray sources and four with no visible optical/IR counterpart. The very deep (~2.7 ?Jy rms) VLA data yield 251 (>4?) radio counterparts, 44% of the X-ray sources in the field. We confirm that the tendency for lower X-ray flux sources to be harder is primarily due to absorption. As expected, there is no correlation between observed IR and X-ray fluxes. Optically bright, type 1, and red AGNs lie in distinct regions of the IR versus X-ray flux plots, demonstrating the wide range of spectral energy distributions in this sample and providing the potential for classification/source selection. Many optically bright sources, which lie outside the AGN region in the optical versus X-ray plots (fr /fx >10), lie inside the region predicted for red AGNs in IR versus X-ray plots, consistent with the presence of an active nucleus. More than 40% of the X-ray sources in the VLA field are radio-loud using the classical definition, RL . The majority of these are red and relatively faint in the optical so that the use of RL to select those AGNs with the strongest radio emission becomes questionable. Using the 24 ?m to radio flux ratio (q 24) instead results in 13 of the 147 AGNs with sufficient data being classified as radio-loud, in good agreement with the ~10% expected for broad-lined AGNs based on optical surveys. We conclude that q 24 is a more reliable indicator of radio-loudness. Use of RL should be confined to the optically selected type 1 AGN.

Wilkes, Belinda J.; Kilgard, Roy; Kim, Dong-Woo; Kim, Minsun; Polletta, Mari; Lonsdale, Carol; Smith, Harding E.; Surace, Jason; Owen, Frazer N.; Franceschini, A.; Siana, Brian; Shupe, David

2009-12-01

357

X-ray (image)  

MedlinePLUS

X-rays are a form of ionizing radiation that can penetrate the body to form an image on ... will be shades of gray depending on density. X-rays can provide information about obstructions, tumors, and other ...

358

X-ray FE line studies  

NASA Technical Reports Server (NTRS)

We present the first broadband, moderate-resolution X-ray spectral observations of the Seyfert galaxies NGC 4151 and NGC 1068. The Seyfert 1 galaxy NGC 4151 is shown to have a complex X-ray spectrum with multiple components and a strong, intrinsically narrow Fe K emission line. The characteristics of the scattering medium of the Seyfert 2 galaxy NGC 1068 are determined using the very strong Fe line emission and the lack of features due to oxygen in the X-ray spectrum. The soft X-ray flux from Mrk 3 and Mrk 348 are consistent with that expected from electron scattered X-rays from an obscured Seyfert 1 nucleus. A survey of the X-ray properties of Seyfert 2 galaxies indicates that a substantial fraction may have column densities of about 10 exp 23, suggesting that NGC 1068 has an unusually thick obscuring torus.

Marshall, F. E.; Arnaud, K.; Boldt, E. A.; Holt, S. S.; Jahoda, K. M.; Kelley, R.; Mushotzky, R. F.; Netzer, H.; Petre, R.; Serlemitsos, P. J.

1992-01-01

359

Using spherically bent crystals for obtaining high-resolution, large-field, monochromatic X-ray backlighting imaging for wide range of Bragg angles  

Microsoft Academic Search

Summary form only given, as follows. The new advantages of well-known combination of a laser-produced X-ray plasma source and spherically bent crystal for the soft X-ray region backlighting scheme were experimentally demonstrated and theoretically modelling by ray-tracing package SHADOW. The X-ray source was produced by heating radiation of Ti:sapphire laser (120 fs, 3-5 mJ, laser flux density 10 13 W\\/cm2)

T. A. Pikuz; A. Ya. Faenov; M. Fraenkel; A. Zigler; F. Flora; S. Bollanti; P. Di Lazzaro; T. Letardi; A. Grilli; L. Palladino; G. Tomassetti; A. Reale; L. Reale; A. Scafati; T. Limongi; F. Bonfigli; L. Alainelli; M. Sanchez del Rio

2000-01-01

360

X-Rays  

MedlinePLUS

... X-Rays htmProcedureXray X-rays are waves of electromagnetic radiation that are used to form images of structures ... What Is It? X-rays are waves of electromagnetic radiation that are used to create images of organs ...

361

Hand x-ray  

MedlinePLUS

X-ray - hand ... A hand x-ray is taken in a hospital radiology department or your health care provider's office by an ... technician. You will be asked to place your hand on the x-ray table, and keep it ...

362

Sinus x-ray  

MedlinePLUS

Paranasal sinus radiography; X-ray - sinuses ... sinus x-ray is taken in a hospital radiology department. Or the x-ray may be taken ... Anslow P. Ear, nose and throat radiology. In: Adam A, Dixon AK, ... Radiology: A Textbook of Medical Imaging . 5th ed. Philadelphia, ...

363

X-ray lithography using holographic images  

DOEpatents

A non-contact X-ray projection lithography method for producing a desired X-ray image on a selected surface of an X-ray-sensitive material, such as photoresist material on a wafer, the desired X-ray image having image minimum linewidths as small as 0.063 .mu.m, or even smaller. A hologram and its position are determined that will produce the desired image on the selected surface when the hologram is irradiated with X-rays from a suitably monochromatic X-ray source of a selected wavelength .lambda.. On-axis X-ray transmission through, or off-axis X-ray reflection from, a hologram may be used here, with very different requirements for monochromaticity, flux and brightness of the X-ray source. For reasonable penetration of photoresist materials by X-rays produced by the X-ray source, the wavelength X, is preferably chosen to be no more than 13.5 nm in one embodiment and more preferably is chosen in the range 1-5 nm in the other embodiment. A lower limit on linewidth is set by the linewidth of available microstructure writing devices, such as an electron beam.

Howells, Malcolm R. (Berkeley, CA); Jacobsen, Chris (Sound Beach, NY)

1995-01-01

364

Flat Field Anomalies in an X-ray CCD Camera Measured Using a Manson X-ray Source  

SciTech Connect

The Static X-ray Imager (SXI) is a diagnostic used at the National Ignition Facility (NIF) to measure the position of the X-rays produced by lasers hitting a gold foil target. The intensity distribution taken by the SXI camera during a NIF shot is used to determine how accurately NIF can aim laser beams. This is critical to proper NIF operation. Imagers are located at the top and the bottom of the NIF target chamber. The CCD chip is an X-ray sensitive silicon sensor, with a large format array (2k x 2k), 24 ?m square pixels, and 15 ?m thick. A multi-anode Manson X-ray source, operating up to 10kV and 10W, was used to characterize and calibrate the imagers. The output beam is heavily filtered to narrow the spectral beam width, giving a typical resolution E/?E?10. The X-ray beam intensity was measured using an absolute photodiode that has accuracy better than 1% up to the Si K edge and better than 5% at higher energies. The X-ray beam provides full CCD illumination and is flat, within ±1% maximum to minimum. The spectral efficiency was measured at 10 energy bands ranging from 930 eV to 8470 eV. We observed an energy dependent pixel sensitivity variation that showed continuous change over a large portion of the CCD. The maximum sensitivity variation occurred at 8470 eV. The geometric pattern did not change at lower energies, but the maximum contrast decreased and was not observable below 4 keV. We were also able to observe debris, damage, and surface defects on the CCD chip. The Manson source is a powerful tool for characterizing the imaging errors of an X-ray CCD imager. These errors are quite different from those found in a visible CCD imager.

M. J. Haugh and M. B. Schneider

2008-10-31

365

X-ray emission from an Ap star /Phi Herculis/ and a late B star /Pi Ceti/  

NASA Technical Reports Server (NTRS)

Using the HEAO 1 soft X-ray sky survey, a search was conducted for X-ray emission from 18 stars in the spectral range B5-A7. The detection of 0.25 keV X-ray sources consistent with the positions of Pi Ceti, a normal B7 V star, and Phi Herculis, a classic Ap star was reported. The detection of these stars argues for large mass motions in the upper layers of stars in this spectral range, and argues against radiative diffusion as the source of abundance anomalies in Ap stars.

Cash, W.; Snow, T. P., Jr.; Charles, P.

1979-01-01

366

Monte Carlo Simulations of High-Speed, Time-Gated MCP-based X-ray Detectors: Saturation Effects in DC Pulsed Modes and Detector Dynamic Range  

SciTech Connect

We present here results of continued efforts to understand the performance of microchannel plate (MCP)–based, high-speed, gated, x-ray detectors. This work involves the continued improvement of a Monte Carlo simulation code to describe MCP performance coupled with experimental efforts to better characterize such detectors. Our goal is a quantitative description of MCP saturation behavior in both static and pulsed modes. A new model of charge buildup on the walls of the MCP channels is briefly described. The simulation results agree favorably with experimental data obtained with a short-pulse, high-intensity ultraviolet (UV) laser. These results indicate that a weak saturation can change the exponent of gain with voltage and that a strong saturation lead to a gain plateau. These results also demonstrate that the dynamic range of an MCP in pulsed mode has a value of between 10^2 and 10^3.

Craig Kruschwitz, Ming Wu, Ken Moy, Greg Rochau

2008-05-30

367

Recent X-ray Variability of Eta Car Approaching The X-ray Eclipse  

NASA Technical Reports Server (NTRS)

We discuss recent X-ray spectral variability of the supermassive star Eta Car in the interval since the last X-ray eclipse in 1998. We concentrate on the interval just prior to the next X-ray eclipse which is expected to occur in June 2003. We compare the X-ray behavior during the 2001-2003 cycle with the previous cycle (1996-1998) and note similarities and differences in the temporal X-ray behavior. We also compare a recent X-ray observation of Eta Car obtained with the Chandra high energy transmission grating in October 2002 with an earlier observation from Nov 2002, and interpret these results in terms of the proposed colliding wind binary model for the star. In addition we discuss planned observations for the upcoming X-ray eclipse.

Corcoran, M.; Swank, J. H.; Ishibashi, K.; Gull, T.; Humphreys, R.; Damineli, A.; Walborn, N.; Hillier, D. J.; Davidson, K.; White, S. M.

2002-01-01

368

A small, battery-operated fluoroscopic system - Lixiscope with X-ray generator  

NASA Technical Reports Server (NTRS)

A small, battery-operated X-ray generator has been developed to be used as part of a small-format fluoroscopic system, the Lixiscope (Low Intensity X-ray Imaging Scope). The X-ray generator consists of a grounded rod-anode X-ray tube with a 0.2 mm focal spot and a specially designed, battery-operated, 0 to -80 kV high-voltge supply. Total power consumption is about 10 W. The fine focal spot, in conjunction with the continuously variable X-ray intensity and spectral distribution, helps to extend both the versatility and the performance of the Lixiscope toward a much wider range of terrestrial and spacecraft applications. The complete fluoroscopic system is described, and some examples of possible applications are shown.

Yin, L. I.; Trombka, J. I.; Ruitberg, A. P.; Seltzer, S. M.

1983-01-01

369

A search for hyperluminous X-ray sources in the XMM-Newton source catalog  

NASA Astrophysics Data System (ADS)

We present a method to search for off-nuclear X-ray sources in the XMM-Newton source catalog by cross-matching it with large spectroscopic galaxy catalogs (e.g. SDSS) using special non-central match condition. Known distances to expected host galaxies then allow to select X-ray sources from their outskirts within specific luminosity range, 10^{41} < L_{X} < 10^{44} erg s^{-1}. We attempt to discard various possible contaminating foreground and background object classes such as AGN, BL Lacs, Galactic stars and compact objects by analyzing broadband radio-to-X-ray spectral energy distribution properties of selected sources available from other public wide area surveys. As an early result of our method we present several candidates to hyperluminous X-ray sources with high X-ray-to-optical flux ratios that can hardly be explained by invoking any conventional object type.

Zolotukhin, I.; Webb, N.; Godet, O.; Bachetti, M.; Barret, D.

2014-07-01

370

X-ray Spectral Evolution of Her X-1 in a Low State and the Following Short High State  

E-print Network

We analyzed spectral variations of $\\sim 8.5$ days long RXTE monitoring observations of Her X-1 in December 2001. This set of observations enables, for the first time, frequent continuous monitoring (111 pointings in $\\sim 8.5$ days) of the source with RXTE including $\\sim 1.7$ days long low state part and the following $\\sim 6.8$ days long short high state part. We used absorbed power law model with iron line energy complex modeled as a Gaussian to fit both the 3-60 keV PCA-HEXTE overall short high state spectrum and 3-20 keV individual PCA spectra. Additional partial cold absorber model was used for both cases. Using 3-20 keV individual PCA spectra, absorption in anomalous dips and preeclipse dips in short high state were compared. Decreasing ratio of unabsorbed flux to absorbed flux with increasing unabsorbed flux in anomalous and preeclipse dips was interpreted as an evidence of the fact that the regions causing opaque obscuration and soft absorption are not geometrically far away from each other. Higher iron line peak energies in low state and short high state ($\\sim 6.6-6.9$ keV) were interpreted as a clue of the presence of iron line components other than K$\\alpha$ emission line.

S. C. Inam; A. Baykal

2005-06-10

371

Structure and Orientation of the Mn4Ca Cluster in PlantPhotosystem II Membranes Studied by Polarized Range-Extended X-rayAbsorption Spectroscopy  

SciTech Connect

X-ray absorption spectroscopy has provided importantinsights into the structure and function of the Mn4Ca cluster in theoxygen-evolving complex (OEC) of Photosystem II (PS II). The range of Mnextended X-ray absorption fine structure (EXAFS) data collected from PSII until now has been, however, limited by the presence of Fe in PS II.Using a crystal spectrometer with high energy resolution to detect solelythe Mn K alpha fluorescence, we are able to extend the EXAFS range beyondthe onset of the Fe absorption edge. This results in improvement inresolution of the Mn-backscatterer distances in PS II from 0.14 Angstromto 0.09 Angstrom. The high-resolution data obtained from oriented spinachPS II membranes in the S1 state show that there are threedi-?-oxo-bridged Mn-Mn distances of ~;2.7 Angstrom and ~;2.8 Angstrom ina 2:1 ratio and that these three Mn-Mn vectors are aligned at an averageorientation of ~;60 deg relative to the membrane normal. Furthermore, weare able to observe the separation of the Fourier peaks corresponding tothe ~;3.2 Angstrom Mn-Mn and the ~;3.4 Angstrom Mn-Ca interactions inoriented PS II samples and determine their orientation relative to themembrane normal. The average of the Mn-Ca vectors at ~;3.4 Angstrom isaligned along the membrane normal, while the ~;3.2 Angstrom Mn-Mn vectoris oriented near the membrane plane. A comparison of this structuralinformation with the proposed Mn4Ca cluster models based on spectroscopicand diffraction data provide input for refining and selecting among thesemodels.

Pushkar, Yulia; Yano, Junko; Glatzel, Pieter; Messinger,Johannes; Lewis, Azul; Sauer, Kenneth; Bergmann, Uwe; Yachandra, Vittal K.

2006-11-10

372

X-Ray Spectra  

NSDL National Science Digital Library

In this activity, learners use simple materials to simulate the effect of X-rays in a safe way. Learners place a piece of window screen over a box and a cardboard pattern on top of the screen. They sprinkle sand over the area of the box. The sand simulates X-rays passing through the screen to the bottom of the box, except where they are blocked by the cardboard. Use this activity to demonstrate how X-rays create an image, including "soft" and shorter wavelength X-rays as well as X-rays from space.

Neil Fetter

2007-01-01

373

Optics-free x-ray FEL oscillator  

SciTech Connect

There is a need for an Optics-Free FEL Oscillators (OFFELO) to further the advantages of free-electron lasers and turning them in fully coherent light sources. While SASE (Self-Amplified Spontaneous Emission) FELs demonstrated the capability of providing very high gain and short pulses of radiation and scalability to the X-ray range, the spectra of SASE FELs remains rather wide ({approx}0.5%-1%) compared with typical short wavelengths FEL-oscillators (0.01%-0.0003% in OK-4 FEL). Absence of good optics in VUV and X-ray ranges makes traditional oscillator schemes with very high average and peak spectral brightness either very complex or, strictly speaking, impossible. In this paper, we discuss lattice of the X-ray optics-free FEL oscillator and present results of initial computer simulations of the feedback process and the evolution of FEL spectrum in X-ray OFFELO. We also discuss main limiting factors and feasibility of X-ray OFFELO.

Litvinenko, V.N.; Hao, Y.; Kayran, D.; Trbojevic, D.

2011-03-28

374

L-edge X-ray absorption study of mononuclear vanadium complexes and spectral predictions using a restricted open shell configuration interaction ansatz.  

PubMed

A series of mononuclear V((V)), V((IV)) and V((III)) complexes were investigated by V L-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The spectra show significant sensitivity to the vanadium oxidation state and the coordination environment surrounding the vanadium center. The L-edge spectra are interpreted with the aid of the recently developed Density Functional Theory/Restricted Open Shell Configuration Interaction Singles (DFT/ROCIS) method. This method is calibrated for the prediction of vanadium L-edges with different hybrid density functionals and basis sets. For the B3LYP/def2-TZVP(-f) and BHLYP/def2-TZVP(-f) functional/basis-set combinations, good to excellent agreement between calculated and experimental spectra is obtained. A treatment of the spin-orbit coupling interaction to all orders is achieved by quasi-degenerate perturbation theory (QDPT), in conjunction with DFT/ROCIS for the calculation of the molecular multiplets while accounting for dynamic correlation and anisotropic covalency. The physical origin of the observed spectral features is discussed qualitatively and quantitatively in terms of spin multiplicities, magnetic sublevels and individual 2p to 3d core level excitations. This investigation is an important prerequisite for future applications of the DFT/ROCIS method to vanadium L-edge absorption spectroscopy and vanadium-based heterogeneous catalysts. PMID:24247594

Maganas, Dimitrios; Roemelt, Michael; Weyhermüller, Thomas; Blume, Raoul; Hävecker, Michael; Knop-Gericke, Axel; DeBeer, Serena; Schlögl, Robert; Neese, Frank

2014-01-01

375

Geometry and spectral properties of the protonated homodimer of pyridine in the liquid and solid states. A combined NMR, X-ray diffraction and inelastic neutron scattering study.  

PubMed

The structure and spectral signatures of the protonated homodimer of pyridine in its complex with a poorly coordinating anion have been studied in solution in CDF(3)/CDClF(2) down to 120 K and in a single crystal. In both phases, the hydrogen bond is asymmetric. In the solution, the proton is involved in a fast reversible transfer that determines the multiplicity of NMR signals and the sign of the primary H/D isotope effect of --0.95 ppm. The proton resonates at 21.73 ppm that is above any value reported in the past and is indicative of a very short hydrogen bond. By combining X-ray diffraction analysis with model computations, the position of the proton in the crystal has been defined as d(N-H) = 1.123 Å and d(H···N) = 1.532 Å. The same distances have been estimated using a (15)N NMR correlation. The frequency of the protonic out-of-plane bending mode is 822 cm(-1) in agreement with Novak's correlation. PMID:21644583

Kong, S; Borissova, A O; Lesnichin, S B; Hartl, M; Daemen, L L; Eckert, J; Antipin, M Yu; Shenderovich, I G

2011-07-14

376

RESIK observations of highly ionized argon and potassium X-ray emission lines in solar flares  

Microsoft Academic Search

The first detailed solar X-ray spectra obtained by the RESIK bent crystal spectrometer aboard the CORONAS-F obervatory are presented and instrument performance discussed. RESIK is a bent crystal spectrometer covering four soft X-ray spectral ranges (3.369-3.879 Å, 3.821-4.326 Å, 4.307-4.890 Å 4.960-6.086 Å), some of which have not been well covered by previous instruments. RESIK forms spectra in each of

J. Sylwester; J. L. Culhane; G. A. Doschek; V. N. Oraevsky; K. J. H. Phillips; B. Sylwester

2002-01-01

377

Molecular imaging using X-ray free-electron lasers.  

PubMed

The opening of hard X-ray free-electron laser facilities, such as the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory in the United States, has ushered in a new era in structural determination. With X-ray pulse durations down to 10 fs or shorter, and up to 10(13) transversely coherent photons per pulse in a narrow spectral bandwidth, focused irradiances of 10(18) to 10(21) W cm(-2) or higher can be produced at X-ray energies ranging from 500 eV to 10 keV. New techniques for determining the structure of systems that cannot be crystallized and for studying the time-resolved behavior of irreversible reactions at femtosecond timescales are now available. PMID:23331310

Barty, Anton; Küpper, Jochen; Chapman, Henry N

2013-01-01

378

An X-ray Grating Spectrometer for the ISS  

NASA Astrophysics Data System (ADS)

We present the design approach for a X-ray grating spectrometer mission to be deployed on the International Space Station. The baseline design uses sub-apertured X-ray optics feeding into off-plane gratings to achieve both high spectral resolution with a large effective area; the read out is by high-TRL CCDs in the focal plane. The mission will use a pointing system with a novel technology to reduce vibrations from the ISS propagating into the telescope, and would be ready to be attached to the ISS in 2021. The mission parameters are similar to those of the IXO X-ray Grating Spectrometer of R=3000 and ~1000 sq. cm at 0.5 keV, with a bandpass from ~0.3-1 keV, enabling a wide range of science objectives.

Bookbinder, Jay A.; McEntaffer, Randall L.; Daigneau, Peter; Smith, Randall K.; Bautz, Mark W.; Burrows, David N.; Willingale, Richard; Petre, Robert; Wilms, Jörn; Falcone, Abraham; Brickhouse, Nancy S.; Ptak, Andrew; Foster, Adam; Bregman, Joel N.

2014-06-01

379

X-Ray Data Booklet X-RAY DATA BOOKLET  

E-print Network

X-Ray Data Booklet X-RAY DATA BOOKLET Center for X-ray Optics and Advanced Light Source Lawrence Berkeley National Laboratory Introduction X-Ray Properties of Elements Electron Binding Energies X-Ray Levels of Few Electron Ions Now Available Order X-Ray Data Booklet http://xdb.lbl.gov/ (1 of 3) [2

Meagher, Mary

380

CdTe quantum dots and polymer nanocomposites for x-ray scintillation and imaging  

PubMed Central

Investigations are reported on the x-ray scintillation and imaging application of CdTe quantum dots (QDs) and their polymer nanocomposites. Aqueous CdTe QDs with emissions ranging between 510 and 680 nm were prepared and incorporated into polyvinyl alcohol or polymethyl methacrylate polymer matrices. The x-ray luminescent properties were evaluated and a resolution of 5 lines?mm was obtained from the nanocomposite films. Additionally, the fast decay time, nonafterglow, and superior spectral match to conventional charge coupled devices, show that CdTe QD nanocomposites have high promise for x-ray imaging applications. PMID:21629562

Kang, Zhitao; Zhang, Yuelan; Menkara, Hisham; Wagner, Brent K.; Summers, Christopher J.; Lawrence, William; Nagarkar, Vivek

2011-01-01

381

Calibration of a high resolution grating soft x-ray spectrometer  

SciTech Connect

The calibration of the soft x-ray spectral response of a large radius of curvature, high resolution grating spectrometer (HRGS) with a back-illuminated charge-coupled device detector is reported. The instrument is cross-calibrated for the 10-50 A waveband at the Lawrence Livermore National Laboratory electron beam ion trap (EBIT) x-ray source with the EBIT calorimeter spectrometer. The HRGS instrument is designed for laser-produced plasma experiments and is important for making high dynamic range measurements of line intensities, line shapes, and x-ray sources.

Magee, E. W.; Dunn, J.; Brown, G. V.; Beiersdorfer, P. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Cone, K. V.; Park, J. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Department of Applied Sciences, University of California, Davis, California 95616 (United States); Porter, F. S.; Kilbourne, C. A.; Kelley, R. L. [Goddard Space Flight Center, NASA, Greenbelt, Maryland 20770 (United States)

2010-10-15

382

Complete Hard X-Ray Surveys, AGN Luminosity Functions and the X-Ray Background  

NASA Technical Reports Server (NTRS)

AGN are believed to make up most of the Cosmic X-Ray Background (CXB) above a few keV, but this background cannot be fully resolved at energies less than 10 keV due to absorption. The Swift/BAT and INTEGRAL missions are performing the first complete hard x-ray surveys with minimal bias due to absorption. The most recent results for both missions will be presented. Although the fraction of the CXB resolved by these surveys is small, it is possible to derive unbiased number counts and luminosity functions for AGN in the local universe. The survey energy range from 15-150 keV contains the important reflection and cutoff spectral features dominate the shape of the AGN contribution to the CXB. Average spectral characteristics of survey detected AGN will be presented and compared with model distributions. The numbers of hard x-ray blazars detected in these surveys are finally sufficient to estimate this important component's contribution the cosmic background. Constraints on CXB models and their significance will be discussed.

Tueller, Jack

2011-01-01

383

Analyzing the Spectra of Accreting X-Ray Pulsars  

NASA Astrophysics Data System (ADS)

This proposal seeks funding for the analysis of accretion-powered X-ray pulsar spectra from NASA/ HEASARC archived X-ray data. Spectral modeling of accreting X-ray pulsars can tell us a great deal about the physical conditions in and near high mass X-ray binary systems. Such systems have accretion flows where plasma is initially channeled from an accretion disk by the strong neutron star magnetic field, eventually falling onto the magnetic polar cap of the neutron star compact object. Many of these accreting X-ray pulsars have X-ray spectra that consist of broad power-law continua with superposed cyclotron resonant scattering features indicating magnetic field strengths above 10^12 G. The energies of these cyclotron line features have recently been shown to vary with X-ray luminosity in a number of sources such as Her X-1 and V 0332+53, a phenomenon not well understood. Another recent development is the relatively new analytic model for the spectral continuum formation in accretion-powered pulsar systems developed by Becker & Wolff. In their formalism the accretion flows are assumed to go through radiation- dominated radiative shocks and settle onto the neutron star surface. The radiation field consists of strongly Comptonized bremsstrahlung emission from the entire plasma, Comptonized cyclotron emission from the de-excitations of Landau-excited electrons in the neutron star magnetic field, and Comptonized black-body emission from a thermal mound near the neutron star surface. We seek to develop the data analysis tools to apply this model framework to the X-ray data from a wide set of sources to make progress characterizing the basic accretion properties (e.g., magnetic field strength, plasma temperatures, polar cap size, accretion rate per unit area, dominance of bulk vs. thermal Comptonization) as well as understanding the variations of the cyclotron line energies with X-ray luminosity. The three major goals of our proposed work are as follows: In the first year, we will develop the new software module (essentially a computer code representing the theoretical model) necessary to perform the analysis of accretion-powered pulsar X-ray spectra in the XSPEC spectral analysis environment. Also in this first year we will analyze new Suzaku Cycle 6 Target of Opportunity observations of GX 304-1 and 4U 0115+63, two known cyclotron line sources, that we have recently carried out. In the second year of this study we will apply our new XSPEC spectral continuum module to the archival X-ray observational data from a number of accreting X-ray pulsars from the RXTE/PCA/HEXTE and Suzaku/XIS/HXD instruments to extract basic accretion parameters. Our source list contains eight pulsars, seven of which have observed cyclotron scattering lines. These pulsars span a range in magnetic field strength, luminosity, expected accretion rate, expected polar cap size, and Comptonizing temperature. In the second year of this work we also plan to make our new fully tested XSPEC continuum analysis module available to the Goddard Space Flight Center HEASARC for distribution to the astrophysical research community. The development and analysis tasks proposed here will provide for the first time a physical basis for the analysis and interpretation of data on accreting X-ray pulsar spectra.

Wolff, Michael

384

Measurement of the x-ray mass attenuation coefficient and determination of the imaginary component of the atomic form-factor of tin over the energy range of 29 keV-60 keV.  

SciTech Connect

We use the x-ray extended-range technique (XERT) [C. T. Chantler et al., Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of tin in the x-ray energy range of 29-60 keV to 0.04-3 % accuracy, and typically in the range 0.1-0.2 %. Measurements made over an extended range of the measurement parameter space are critically examined to identify, quantify, and correct a number of potential experimental systematic errors. These results represent the most extensive experimental data set for tin and include absolute mass attenuation coefficients in the regions of x-ray absorption fine structure, extended x-ray absorption fine structure, and x-ray absorption near-edge structure. The imaginary component of the atomic form factor f{sub 2} is derived from the photoelectric absorption after subtracting calculated Rayleigh and Compton scattering cross sections from the total attenuation. Comparison of the result with tabulations of calculated photoelectric absorption coefficients indicates that differences of 1-2 % persist between calculated and observed values.

de Jonge, M. D.; Tran, C. Q.; Chantler, C. T.; Barnea, Z.; Dhal, B. P.; Paterson, D.; Kanter, E. P.; Southworth, S. H.; Young, L.; Beno, M. A.; Linton, J. A.; Jennings, G.; Univ. of Melbourne; Australian Synchrotron Project

2007-01-01

385

X-Ray Absorbed, Broad-Lined, Red AGN and the Cosmic X-Ray Background  

NASA Technical Reports Server (NTRS)

We have obtained XMM spectra for five red, 2MASS AGN, selected from a sample observed by Chandra to be X-ray bright and to cover a range of hardness ratios. Our results confirm the presence of substantial absorbing material in three sources which have optical classifications ranging from Type 1 to Type 2, with an intrinsically flat (hard) power law continuum indicated in the other two. The presence of both X-ray absorption and broad optical emission lines with the usual strength suggests either a small (nuclear) absorber or a favored viewing angle so as to cover the X-ray source but not the broad emission line region (BELR). A soft excess is detected in all three Type 1 sources. We speculate that this soft X-ray emission may arise in an extended region of ionized gas, perhaps linked with the polarized (scattered) light which is a feature of these sources. The spectral complexity revealed by XMM emphasizes the limitations of the low S/N Chandra data. Overall, the new XMM results strengthen our conclusions (Wilkes et al. 2002) that the observed X-ray continua of red AGN are unusually hard at energies greater than 2 keV. Whether due to substantial line-of-sight absorption or to an intrinsically hard or reflection-dominated spectrum, these 'red' AGN have an observed spectral form consistent with contributing significantly to the missing had absorbed population of the Cosmic X-ray Background (CXRB). When absorption and or reflection is taken into account, all these AGN have power law slopes typical of broad-line (Type 1) AGN (Gamma approximately 1.9). This appears to resolve the spectral paradox which for so long has existed between the CXRB and the AGN thought to be the dominant contributors. It also suggests two scenarios whereby Type 1 AGN/QSOs may be responsible for a significant fraction of the CXRB at energies above 2 keV: 1) X-ray absorbed AGN/QSOs with visible broad emission lines; 2) AGN/QSOs with complex spectra whose hardness greater than 2 keV is not detectable in the typically low S/N data of X-ray surveys. Even if absorption is present in only half of the population, the large number of 'red' AGN suggests a development of unification models, where the continuum source is surrounded, over a substantial solid angle, by the wind or atmosphere of an accretion disk/torus. X-ray observations of such AGN not only provide a check on the presence of absorption, but also a unique probe of the absorbing material. Improved information on their space density, in particular as a function of redshift, will soon be provided by Spitzer-Chandra wide area surveys, allowing better estimates of both the importance of red AGN to the full AGN population and their contribution to the CXRB.

Mushotzky, Richard (Technical Monitor); Wilkes, Belinda

2005-01-01

386

Metal concentration and X-ray cool spectral component in the central region of the Centaurus cluster of galaxies  

NASA Technical Reports Server (NTRS)

Spatially resolved energy spectra in the energy range 0.5-10 keV have been measured for the Centaurus cluster of galaxies with Advanced Satellite for Cosmology and Astrophysics (ASCA). Within 10 min (200 kpc) from the cluster center, the helium-like iron K emission line exhibits a dramatic increase toward the center rising from an equivalent width approximately 500 eV to approximately 1500 eV corresponding to an abundance change from 0.3 to 1.0 solar. The presence of strong iron L lines indicates an additional cool component (kT approximately 1 keV) within 10 min from the center. The cool component requires absorption in excess of the galactic value and this excess absorption increases towards the central region of the cluster. In the surrounding region with radius greater than 10 min, the spectra are well described by a single temperature thermal model with kT approximately 4 keV and spatially uniform abundances at about 0.3-0.4 times solar. The detection of metal-rich hot and cool gas in the cluster center implies a complex nature of the central cluster gas which is likely to be related to the presence of the central cD galaxy NGC 4696.

Fukazawa, Yasushi; Ohashi, Takaya; Fabian, Andrew C.; Canizares, Claude R.; Ikebe, Yasushi; Makishima, Kazuo; Mushotzky, Richard F.; Yamashita, Koujun

1994-01-01

387

Plasmon measurements with a seeded x-ray laser  

NASA Astrophysics Data System (ADS)

Plasmon measurements hold great promise for providing highly accurate data on the physical properties of plasmas in the high-energy density physics regime. To this end we demonstrate in recent experiments at the Linac Coherent Light Source the first spectrally-resolved measurements of plasmons using a seeded 8-keV x-ray laser beam. Forward x-ray Thomson scattering spectra from isochorically heated solid aluminum show a well-resolved plasmon feature that is down-shifted in energy by 19 eV from the incident 8 keV elastic scattering feature. In this spectral range, the simultaneously measured backscatter spectrum shows no spectral features indicating observation of collective plasmon oscillations on a scattering length comparable to the screening length. This technique is a prerequisite for Thomson scattering measurements in compressed matter where the plasmon shift is a sensitive function of the free electron density and where the plasmon intensity provides information on temperature.

Fletcher, L. B.; Galtier, E.; Heimann, P.; Lee, H. J.; Nagler, B.; Welch, J.; Zastrau, U.; Hastings, J. B.; Glenzer, S. H.

2013-11-01

388

First Hard X-Ray Detection of the Non-Thermal Emission Around the Arches Cluster: Morphology and Spectral Studies With NuSTAR  

NASA Technical Reports Server (NTRS)

The Arches cluster is a young, densely packed massive star cluster in our Galaxy that shows a high level of star formation activity. The nature of the extended non-thermal X-ray emission around the cluster remains unclear. The observed bright Fe K(alpha) line emission at 6.4 keV from material that is neutral or in a low ionization state can be produced either by X-ray photoionization or by cosmic-ray particle bombardment or both. In this paper, we report on the first detection of the extended emission around the Arches cluster above 10 keV with the NuSTAR mission, and present results on its morphology and spectrum. The spatial distribution of the hard X-ray emission is found to be consistent with the broad region around the cluster where the 6.4 keV line is observed. The interpretation of the hard X-ray emission within the context of the X-ray reflection model puts a strong constraint on the luminosity of the possible illuminating hard X-ray source. The properties of the observed emission are also in broad agreement with the low-energy cosmic-ray proton excitation scenario. Key words: cosmic rays - Galaxy: center - ISM: general - X-rays: individual (Arches cluster)

Krivonos, Roman A.; Tomsick, John A.; Bauer, Franz E.; Baganoff, Frederick K.; Barriere, Nicolas M.; Bodaghee, Arash; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Grefenstette, Brian W.; Hailey, Charles J.; Harrison, Fiona A.; Hong, JaeSub; Madsen, Kristin K.; Mori, Kaya; Nynka, Melania; Stern, Daniel; Zhang, William W.

2014-01-01

389

Polarized Range-Extended X-Ray Absorption Spectroscopy of Oriented Photosystem Ii Membranes in the S (1) State  

SciTech Connect

Detailed information about the orientation of particular Mn-Mn and Mn-Ca vectors in the oxygen evolving complex (OEC) of the Photosystem II in the S{sub 1} state provide a critical starting point for the analysis of the structural changes in the OEC along the catalytic S{sub i}-state cycle. The method of polarized range-extended EXAFS is an important technical development, that allows: (i) resolution of the 2.7 {angstrom} and 2.8 {angstrom} Mn-Mn interactions; (ii) resolution of 3.2 {angstrom} Mn-Mn and 3.4 {angstrom} Mn-Ca; (iii) determination of 2.7 {angstrom}, 2.8 {angstrom}, 3.2 {angstrom} Mn-Mn and 3.4 {angstrom} Mn-Ca vectors orientation relative to the membrane normal.

Pushkar, Y.; Yano, J.; Glatzel, P.; Messinger, J.; Lewis, A.; Sauer, K.; Bergmann, U.; Yachandra, V.K.

2009-06-05

390

Einstein Observatory magnitude-limited X-ray survey of late-type giant and supergiant stars  

NASA Technical Reports Server (NTRS)

Results are presented of an extensive X-ray survey of 380 giant and supergiant stars of spectral types from F to M, carried out with the Einstein Observatory. It was found that the observed F giants or subgiants (slightly evolved stars with a mass M less than about 2 solar masses) are X-ray emitters at the same level of main-sequence stars of similar spectral type. The G giants show a range of emissions more than 3 orders of magnitude wide; some single G giants exist with X-ray luminosities comparable to RS CVn systems, while some nearby large G giants have upper limits on the X-ray emission below typical solar values. The K giants have an observed X-ray emission level significantly lower than F and F giants. None of the 29 M giants were detected, except for one spectroscopic binary.

Maggio, A.; Vaiana, G. S.; Haisch, B. M.; Stern, R. A.; Bookbinder, J.

1990-01-01

391

Time-resolved x-ray diffraction with subpicosecond x-ray pulses  

Microsoft Academic Search

The emission from plasmas created with fs-lasers provides sub-picosecond x-ray pulses in the keV-range. Intense emission of K(alpha) lines as well as quasi continuum x-rays can be used for time-resolved diffraction and spectroscopy, i.e. to study lattice or atomic dynamics with sub-picosecond resolution by using a laser pump x-ray probe technique. The x-ray yield and x-ray pulse duration of the

Ingo Uschmann; Eckhart Foerster; Paul Gibbon; Christian Reich; Thomas Feurer; Andreas Morak; Roland A. Sauerbrey; Antoine Rousse; Patrick Audebert; Jean-Paul Geindre; Jean-Claude J. Gauthier

2001-01-01

392

The Focusing Optics X-ray Solar Imager (FOXSI)  

NASA Astrophysics Data System (ADS)

The Focusing Optics x-ray Solar Imager (FOXSI) is a sounding rocket payload funded under the NASA Low Cost Access to Space program to test hard x-ray (HXR) focusing optics and position-sensitive solid state detectors for solar observations. Today's leading solar HXR instrument, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) provides excellent spatial (2 arcseconds) and spectral (1 keV) resolution. Yet, due to its use of an indirect imaging system, the derived images have a low dynamic range (typically <10) and sensitivity. These limitations make it difficult to study faint x-ray sources in the solar corona which are crucial for understanding the particle acceleration processes which occur there. Grazing-incidence x-ray focusing optics combined with position-sensitive solid state detectors can overcome both of these limitations enabling the next breakthrough in understanding impulsive energy release on the Sun. The FOXSI project is led by the Space Sciences Laboratory at the University of California, Berkeley. The NASA Marshall Space Flight Center is responsible for the grazingincidence optics, while the Astro-H team at JAXA/ISAS has provided double-sided silicon strip detectors. FOXSI is a pathfinder for the next generation of solar hard x-ray spectroscopic imagers. Such observatories will be able to image the non-thermal electrons within the solar flare acceleration region, trace their paths through the corona, and provide essential quantitative measurements such as energy spectra, density, and energy content in accelerated electrons.

Krucker, Säm; Christe, Steven; Glesener, Lindsay; Ishikawa, Shin-nosuke; McBride, Stephen; Glaser, David; Turin, Paul; Lin, R. P.; Gubarev, Mikhail; Ramsey, Brian; Saito, Shinya; Tanaka, Yasuyuki; Takahashi, Tadayuki; Watanabe, Shin; Tanaka, Takaaki; Tajima, Hiroyasu; Masuda, Satoshi

2011-09-01

393

X-ray Polarimetry  

NASA Astrophysics Data System (ADS)

1. X-ray polarimetry: historical remarks and other considerations; Part I. Polarimetry Techniques: 2. Scattering polarimetry in high energy astronomy; 3. Photoelectric polarimeters; 4. Bragg crystal polarimeters; 5. X-ray polarimetry with the photon counting pixel detector timepix; 6. HE polarized photon interactions with matter: simulations with geant4; 7. The GPD as a polarimeter: theory and facts; 8. Ideal gas electron multipliers (GEMs) for x-ray polarimeters; 9. Broad-band soft x-ray polarimetry; 10. Feasibility of x-ray photoelectric polarimeters with large field of view; 11. Angular resolution of a photoelectric polarimeter; 12. Development of a Thomson x-ray polarimeter; 13. Hard x / soft gamma ray polarimetry using a Laue lens; Part II. Polarized Emission in X-ray Sources: 14. Probing strong gravity effects with x-ray polarimetry; 15. X-ray polarization from black holes in the thermal state; 16. Strong-gravity effects acting on polarization from orbiting spots; 17. Polarization of thermal emission from accreting black holes; 18. X-ray polarimetry and radio-quiet AGN; 19. The soft x-ray polarization in obscured AGN; 20. The polarization of complex x-ray sources; 21. Polarization of Compton x-rays from jets in AGN; 22. Polarization of x-ray lines from galaxy clusters and elliptical galaxies; 23. Polarization characteristics of rotation-powered pulsars; 24. Polarized x-rays from magnetized neutron stars; 25. Polarization properties of x-ray millisecond pulsars; 26. X-ray polarization signatures of neutron stars; 27. Polarization from the oscillating magnetized accretion torus; 28. X-ray polarization from accreting white dwarfs and associated systems; 29. Polarization of pulsar wind nebulae; 30. X-ray polarization of gamma-ray bursts; 31. Central engine afterglow from GRBs and the polarization signature; 32. GRB afterglow polarimetry. Past, present and future; 33. Gamma-ray polarimetry with SPI; 34. INTEGRAL/IBIS observations of the Crab Nebula and GRB 041219A; 35. Fermi results on the origin of high energy emission in pulsars; 36. Diagnostics of the evolution of spiral galaxies in a cluster environment; Part III. Future Missions: 37. Gravity and extreme magnetism SMEX (GEMS); 38. Programs of x-ray polarimetry in Italy; 39. A polarimeter for IXO; 40. Polarimetry with ASTRO-H soft gamma-ray detector; 41. EXIST and its polarization sensitivity; 42. PoGOLite: a balloon-borne soft gamma-ray polarimeter; 43. Studies of neutron background rejection in the PoGOLite polarimeter; 44. Observing polarized x-rays with PoGOLite; 45. Pre-flight qualification tests of the PoGOLite detector system; 46. The gamma-ray polarimeter experiment (GRAPE) Balloon Payload; 47. POLAR: an instrument dedicated to GRB polarization measurement; 48. Polarisation detection capability of GRIPS; 49. X-ray and y-ray polarimetry small satellite mission polaris; 50. GAP aboard the solar powered sail mission; 51. Hard x-ray polarimeter for small satellite missions; 52. Performance of hard x-ray polarimeter: PHENEX; 53. GRB polarimetry with POET; Index.

Bellazzini, Ronaldo; Costa, Enrico; Matt, Giorgio; Tagliaferri, Gianpiero

2010-07-01

394

X-Ray Production by V1647 Ori During Optical Outbursts  

NASA Technical Reports Server (NTRS)

The pre-main-sequence (PMS) star V1647 Ori has recently undergone two optical/near-infrared (OIR) outbu