Note: This page contains sample records for the topic x-ray spectral range from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Relative calibration of photodiodes in the soft-x-ray spectral range  

SciTech Connect

A method of obtaining a relative calibration of Si photodiodes for the spectral range of soft x rays (1--30 keV) is presented. A simple mathematical model of the {ital p}-{ital n} diode is adopted which allows the response to be described in terms of a small set of parameters. The diffusion length as well as the thickness of a dead layer below the front surface of the diodes are obtained from measurements of angular dependences of the photoinduced current. It is shown that a precise characterization of the diode response and an accurate relative calibration can be obtained using this method. However, it was found that the presence of a dead layer a few tenths of a micrometer thick can pose severe restrictions on the use of planar diode arrays in x-ray tomography systems where uniformity of response is crucial. The method has been applied to the diode arrays equipping the x-ray tomography system built for the TCV tokamak, a magnetic fusion research device. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Anton, M.; Dutch, M.J.; Weisen, H. [Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Federale de Lausanne, Association EURATOM-Confederation Suisse, Avenue des Bains 21, CH-1007 Lausanne (Switzerland)] [Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Federale de Lausanne, Association EURATOM-Confederation Suisse, Avenue des Bains 21, CH-1007 Lausanne (Switzerland)

1995-07-01

2

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

PubMed

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 ? 50. It has been used at the LULI-2000 laser facility at E?cole Polytechnique (France) to measure the ?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. PMID:23126955

Reverdin, Charles; Thais, Frédéric; Loisel, Guillaume; Busquet, M; Bastiani-Ceccotti, S; Blenski, T; Caillaud, T; Ducret, J E; Foelsner, W; Gilles, D; Gilleron, F; Pain, J C; Poirier, M; Serres, F; Silvert, V; Soullie, G; Turck-Chieze, S; Villette, B

2012-10-01

3

Spectral slicing X-ray telescope  

NASA Technical Reports Server (NTRS)

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.

1986-01-01

4

The explanation of the spectral relation of radio range and X-ray range by the effect of random magnetic fields.  

NASA Astrophysics Data System (ADS)

We calculate numerically the radiation spectrum from relativistic electrons moving in small-scale turbulent magnetic fields, in relevance to the collisionless shocks of high energy celestial objects. The radiation spectrum is characterized by the strength parameter a = ? e B/mc^2 (? is the length of the turbulent field), If a >> ?, synchrotron approximation is valid ( ? is the Lorentz factor of radiating electron). However, for a < ?, synchrotron approximation is not trivial. Although for a << 1 the electron orbit is approximately straight and we can calculate analytically the radiation from the electron (jitter radiation), for a > 1 we can no longer assume the straight electron orbit. For the most interesting case of 1 < a < ? we cannot use either approximations, so that we should use the most direct method to evaluate the radiation spectrum. Therefore we generate random magnetic fields assuming Kolmogorov turbulence, and we inject monoenergetic electrons in this field, solve the equation of motion, and calculate the radiation spectrum by using the Lienard-Wiechert potential. We performed calculations for several values of a, with ? = 10, and we obtain various types of spectra ranging between jitter radiation and synchrotron radiation. For a = 7, the spectrum takes a novel shape which had not been noticed before. It is like a synchrotron spectrum in the middle energy region, but in the low energy region it is a broken power law and in the high frequency region an extra power-law component appears beyond the synchrotron cutoff. Therefore, if the spectral break is detected at the radio range and extra component is detected at the X-ray range when someone observe the synchrotron spectra of some high energy celstial object, the feature may be caused by random magnetic fields.

Teraki, Yuto; Takahara, Fumio

2012-07-01

5

THE SECOND STAGE OF FERMI@ELETTRA: A SEEDED FEL IN THE SOFT X-RAY SPECTRAL RANGE  

SciTech Connect

The second stage of the FERMI FEL, named FEL-2, is based on the principle of high-gain harmonic generation and relies on a double-seeded cascade. Recent developments stimulated a revision of the original setup, which was designed to cover the spectral range between 40 and 10 nm. The numerical simulations we present here show that the nominal (expected) electron-beam performance allows extension of the FEL spectral range down to 4 nm. A significant amount of third harmonic power can be also expected. We also show that the proposed setup is flexible enough for exploiting future developments of new seed sources, e.g., high harmonic generation in gases.

Allaria, E.; DeNinno, G.; Fawley, W. M.

2009-08-14

6

X-ray Spectral Properties of Low-Mass X-ray Binaries in Nearby Galaxies  

NASA Astrophysics Data System (ADS)

We have investigated the X-ray spectral properties of a collection of low-mass X-ray binaries (LMXBs) within a sample of 15 nearby early-type galaxies using proprietary and archival data from the Chandra X-ray Observatory. We find that the spectrum of the sum of the sources in a given galaxy is remarkably similar from galaxy to galaxy when sources with X-ray luminosities less than 1039 ergs s-1 (0.3--10 keV) are considered. Fitting these lower luminosity sources in all galaxies simultaneously with a power law model led to a best-fit value of Gamma = 1.56 +/- 0.02 (90% confidence), and using a thermal bremsstrahlung model yielded kTbrem = 7.3 +/- 0.3 keV. This is the tightest constraint to date on the spectral properties of LMXBs in external galaxies. In addition, the spectral properties of the LMXBs do not vary with galactic radius out to three effective radii. Although few in number in any given galaxy, sources with luminosities in the 1-2 x 1039 ergs s-1 range are present in 10 of the galaxies. The spectra of these luminous sources are statistically softer than the spectra of the rest of the sources, and are consistent with the spectra of Galactic black hole X-ray binary candidates when they are in their very high/flare state. The number of sources with apparent luminosities above 2 x 1039 ergs s-1 when determined using the distance of the galaxy is equal to the number of expected background AGN and thus appear to be not associated with the galaxy, indicating that very luminous sources are absent or very rare in early-type galaxies. Using the constraints and seemingly, universally applicable results of the hard component, we have also determined the X-ray luminosity of the hot gas in four of the galaxies with exceptionally low LX/Lopt ratios. The derived luminosities are substantially lower than was determined with previous X-ray telescopes, owing to the inability of previous instruments to resolve out AGN and LMXBs in these galaxies. Further studies of X-ray faint elliptical galaxies with Chandra benefit from the tight constraints placed on the hard component and will help refine our view of how gas is retained/lost from a galaxy as a result of hydrodynamical and/or environmental effects.

Irwin, J. A.; Athey, A. E.; Bregman, J. N.

2002-12-01

7

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

8

Tomographic imaging of coherent x-ray scatter momentum transfer distribution using spectral x-ray detection and polycapillary optic  

NASA Astrophysics Data System (ADS)

Quantitation of coherent x-ray scatter traditionally involves measuring the intensity of the scattered x-ray over a range of angles (?) from the illuminating monochromatic x-ray beam. Spectral x-ray imaging produces the same information at a single ? when bremsstrahlung x-ray exposure is used. We used a 200?m thick sheet-illumination of a phantom (lucite cylinder containing holes with water, polyethylene, collagen, polycarbonate, and nylon) and a polycapillary x-ray optic collimator to provide measurements at a fixed ?. A Medipix2 x-ray detection array (2562 (55?m)2 pixels) provided the spectral (E, 10 - 22 keV in 3keV energy bins) spread needed to generate the momentum transfer (q) profile information at one angle. The tungsten x-ray source anode (aluminum filter) was operated at 35kVp at 20mA. The detected scatter intensity was corrected for attenuation of the incident and the scattered x-ray by use of the regular CT image of the phantom generated at the same energy bins. The phantom was translated normal to the plane of the fan beam in 65, 0.2mm, steps to generate the 3D image data. The momentum transfer profiles generated with this approach were compared to published momentum transfer profiles obtained by other methods.

Eaker, Diane R.; Jorgensen, Steven M.; Butler, Anthony P. H.; Ritman, Erik L.

2010-08-01

9

Soft X-ray spectral observations of quasars and high X-ray luminosity Seyfert galaxies  

NASA Technical Reports Server (NTRS)

Results of the analysis of 28 Einstein SSS observations of 15 high X-ray luminosity (L(x) 10 to the 435 power erg/s) quasars and Seyfert type 1 nuclei are presented. The 0.75-4.5 keV spectra are in general well fit by a simple model consisting of a power law plus absorption by cold gas. The average spectral index alpha is 0.66 + or -0.36, consistent with alpha for the spectrum of these objects above 2 keV. In all but one case, no evidence was found for intrinsic absorption, with an upper limit of 2 x 10 to the 21st power/sq cm. Neither was evidence found for partial covering of the active nucleus by dense, cold matter (N sub H greater than 10 to the 22nd power/sq cm); the average upper limit on the partial covering fraction is 0.5. There is no obvious correlation between spectral index and 0.75-4.5 keV X-ray luminosity (which ranges from 3 x 10 to the 43rd to 47th powers erg/s) or with other source properties. The lack of intrinsic X-ray absorption allows us to place constraints on the density and temperature of the broad-line emission region, and narrow line emission region, and the intergalactic medium. Previously announced in STAR as N84-14082

Petre, R.; Mushotzky, R. F.; Holt, S. S.; Krolik, J. H.

1984-01-01

10

Soft X-ray spectral observations of quasars and high X-ray luminosity Seyfert galaxies  

NASA Technical Reports Server (NTRS)

Results of the analysis of 28 Einstein SSS observations of 15 high X-ray luminosity (L(x) 10 to the 435 power erg/s) quasars and Seyfert type 1 nuclei are presented. The 0.75-4.5 keV spectra are in general well fit by a simple model consisting of a power law plus absorption by cold gas. The averager spectral index alpha is 0.66 + or - .36, consistent with alpha for the spectrum of these objects above 2 keV. In all but one case, no evidence was found for intrinsic absorption, with an upper limit of 2 x 10 to the 21st power/sq cm. Neither was evidence found for partial covering of the active nucleus by dense, cold matter (N(H) 10 to the 22nd power/sq cm; the average upper limit on the partial covering fraction is 0.5. There is no obvious correlation between spectral index and 0175-4.5 keV X-ray luminosity (which ranges from 3 x 10 to the 43rd to 47th powers erg/s or with other source properties. The lack of intrinsic X-ray absorption allows us to place constraints on the density and temperature of the broad-line emission region, and narrow line emission region, and the intergalactic medium.

Petre, R.; Mushotzky, R. F.; Krolik, J. H.; Holt, S. S.

1983-01-01

11

A new technique for X-ray spectroscopy of laser-plasmas with simultaneous 2D spatial resolution over a broad spectral range  

SciTech Connect

Over the past few years, a new X-ray diagnostic technique has been developed by the group of the Intense Laser Irradiation Laboratory of the CNR in Pisa. Here we give a brief description of this new diagnostic tool, which basically allows X-ray spectroscopy of laser-produced plasmas to be performed over a broad photon energy range with a simultaneous 2D spatial resolution. An outline of recent results will be also given in order to assess the diagnostic capabilities.

Labate, L.; Cecchetti, C. A.; Giulietti, A.; Giulietti, D.; Koester, P.; Levato, T.; Pathak, N.; Gizzi, L. A. [Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Pisa (Italy); Dipartimento di Fisica, Universita di Pisa (Italy); Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Pisa (Italy); Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare (Italy); Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Pisa (Italy)

2012-05-25

12

Extended range X-ray telescope  

NASA Technical Reports Server (NTRS)

An X-ray telescope system is described which is comprised of a tubular mount having a collecting region remote from the one axial end. A soft X-ray/XUV subsystem associated with the collecting region directs only relatively soft, near on-axis X-rays/XUV radiation incident on a first portion of the collecting region into a first detector sensitive to relatively soft X-rays/XUV radiation. A hard X-ray subsystem associated with the collecting region directs only relatively hard near on-axis X-rays incident on a second portion of the collecting region into a second detector sensitive to relatively hard X-rays.

Hoover, R. B. (inventor)

1981-01-01

13

Jet spectral breaks in black hole X-ray binaries  

NASA Astrophysics Data System (ADS)

In X-ray binaries, compact jets are known to commonly radiate at radio to infrared frequencies, whereas at optical to ?-ray energies, the contribution of the jet is debated. The total luminosity, and hence power of the jet, is critically dependent on the position of the break in its spectrum, between optically thick (self-absorbed) and optically thin synchrotron emission. This break, or turnover, has been reported in just one black hole X-ray binary (BHXB) thus far, GX 339-4, and inferred via spectral fitting in two others, A0620-00 and Cyg X-1. Here, we collect a wealth of multi-wavelength data from the outbursts of BHXBs during hard X-ray states, in order to search for jet breaks as yet unidentified in their spectral energy distributions. In particular, we report the direct detection of the jet break in the spectrum of V404 Cyg during its 1989 outburst, at ?b = (1.8 ± 0.3) × 1014 Hz (1.7 ± 0.2 ?m). We increase the number of BHXBs with measured jet breaks from three to eight. Jet breaks are found at frequencies spanning more than two orders of magnitude, from ?b = (4.5 ± 0.8) × 1012 Hz for XTE J1118+480 during its 2005 outburst, to ?b > 4.7 × 1014 Hz for V4641 Sgr in outburst. A positive correlation between jet break frequency and luminosity is expected theoretically; ?b?L˜ 0.5?, jet if other parameters are constant. With constraints on the jet break in a total of 12 BHXBs including two quiescent systems, we find a large range of jet break frequencies at similar luminosities and no obvious global relation (but such a relation cannot be ruled out for individual sources). We speculate that different magnetic field strengths and/or different radii of the acceleration zone in the inner regions of the jet are likely to be responsible for the observed scatter between sources. There is evidence that the high-energy cooling break in the jet spectrum shifts from UV energies at LX ˜ 10-8LEdd (implying the jet may dominate the X-ray emission in quiescence) to X-ray energies at ˜10-3LEdd. Finally, we find that the jet break luminosity scales as L?, jet?L0.56 ± 0.05X (very similar to the radio-X-ray correlation), and radio-faint BHXBs have fainter jet breaks. In quiescence the jet break luminosity exceeds the X-ray luminosity.

Russell, D. M.; Markoff, S.; Casella, P.; Cantrell, A. G.; Chatterjee, R.; Fender, R. P.; Gallo, E.; Gandhi, P.; Homan, J.; Maitra, D.; Miller-Jones, J. C. A.; O'Brien, K.; Shahbaz, T.

2013-02-01

14

New results on magnetars' X-ray spectral modeling  

Microsoft Academic Search

We present preliminary results on the spectral modeling of magnetars' X-ray emission through a resonant cyclotron scattering model. We fit the soft and hard X-ray spectrum of all magnetars with a main component representing a thermal emission from the neutron star surface which scatters (through a resonant cyclotron scattering process) on a slab of mildly relativistic magnetospheric electrons. Here we

N. Rea; S. Zane; R. Turolla; M. Lyutikov; D. Götz

2008-01-01

15

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

16

Spectral and lateral resolved characterisation of X-ray microbeams  

Microsoft Academic Search

A detailed knowledge of the lateral and spectral flux density profile of X-ray microbeams is essential for micro-X-ray spectrometry. We present a scanning technique for the spectral and lateral resolved characterization of the focal profile of microbeams. As an example, the beam profile of a polycapillary lens in its focal plane is investigated. Furthermore, limitations of the scanning technique are

Birgit Kanngießer; Natalia Kemf; Wolfgang Malzer

2002-01-01

17

Spectral and lateral resolved characterisation of X-ray microbeams  

NASA Astrophysics Data System (ADS)

A detailed knowledge of the lateral and spectral flux density profile of X-ray microbeams is essential for micro-X-ray spectrometry. We present a scanning technique for the spectral and lateral resolved characterization of the focal profile of microbeams. As an example, the beam profile of a polycapillary lens in its focal plane is investigated. Furthermore, limitations of the scanning technique are discussed.

Kanngießer, Birgit; Kemf, Natalia; Malzer, Wolfgang

2002-12-01

18

[X-ray radiographic imaging technique with high dynamic range].  

PubMed

In conventional X-ray radiographic imaging system with a fixed energy parameter, the acquired X-ray images are usually overexposed and have no useful information available. It is due to some constraints, like special structure of component, different attenuation coefficients of materials and dynamic range of optoelectronic devices. When maximum of transmitted X-ray luminous exceed capacity limitation of X-ray radiographic imaging system in one scene, the device up to saturate. Also when minimum of transmitted X-ray luminous is below the thermal noise level of imaging system, no useful information is available for imaging. To solve the problem of difficulties in acquiring transmitted X-ray luminous in a wide dynamic range by conventional X-ray radiographic imaging system, we put forward a new X-ray radiographic imaging technique with high dynamic range based on adjusting tube voltage. In the article, the influence by charge capacity of X-ray radiographic imaging system on effective irradiating thickness is analyzed. Through experiments of some standard samples, we gained the relationship between voltage range of X-ray tube and materials or structure of component for best testing sensitivity. Then we put forward an adjusting strategy of tube voltage and effective subgraphs extraction method from acquired raw X-ray images. By the mentioned method, we carried out X-ray radiographic imaging experiments with high dynamic range for components with thickness from 0 to 20 mm. The results show that X-ray radiographic imaging technique with high dynamic range is effective to realize imaging for some components with different thickness. It is available for us to find more detailed projection information from fusion images. PMID:25007638

Liu, Bin; Wang, Li-Ming; Su, Xin-Yan

2014-04-01

19

Spectral Variation of Hard X-Ray Emission from the Crab Nebula with the Suzaku Hard X-Ray Detector  

NASA Astrophysics Data System (ADS)

The Crab Nebula is one of the brightest and most stable sources in the X-ray sky. Year-scale flux variation from the object was recently revealed in the hard X-ray band by four satellites. This marked the first detection of year-scale variability from pulsar wind nebulae in the hard X-ray band. The Crab Nebula has been observed at least once a year for calibration purposes with the Suzaku Hard X-ray Detector (HXD) since its launch in 2005. In order to investigate possible spectral changes as well as flux variation, archival data of the HXD were analyzed. The flux variation reported by other instruments was confirmed in the 25-100 keV band by the HXD at a few percent level, but flux above 100 keV did not follow the trend in variation below 100 keV. The hardness ratios produced utilizing the PIN and GSO sensors installed in the HXD exhibit significant scattering, thereby indicating spectral variations in the hard X-ray band. The spectral changes were quantified by spectral fitting with a broken power-law model. The difference between the two photon indexes of the broken power-law model in harder and softer energy bands is in the range of < 2.54. Taking into account a flux variation of 6.3% and a spectral variation time-scale of a few days, multi components of the broken power-law-shaped synchrotron emission with different cooling times are suggested.

Kouzu, Tomomi; Tashiro, Makoto S.; Terada, Yukikatsu; Yamada, Shin'ya; Bamba, Aya; Enoto, Teruaki; Mori, Koji; Fukazawa, Yasushi; Makishima, Kazu

2013-08-01

20

X-ray surveys - X-ray spectral analysis of bright Chandra-COSMOS sources  

NASA Astrophysics Data System (ADS)

We present the X-ray spectral analysis of the 405 brightest sources in the Chandra- COSMOS catalog (Elvis et al. 2009) that present at least 70 net counts in the 0.5-7 keV band. This bright sample has a ~100% completeness in optical-IR identification, with ~73% of the sample having a spectroscopic redshift and ~23% a photometric redshift (with accuracy ?(z)/(1+z)~1.5%). This allow us to accurately determine both the intrinsic absorption distribution and the intrinsic L2-10 of all the sources in the sample, and to study the evolution of X-ray spectral parameters in redshift. We analyze the statistical distribution of X-ray spectral properties in the sample (e.g. NH and L2-10 distribution, fraction of obscured sources) and their correlation with multiwavelength properties. Finally, 294 sources present a detected counterpart in the XMM-COSMOS survey. For this sources we performed a simultaneous spectral fit with the XMM-Newton data, in order to search for systematic differences in the constraint on spectral parameters and, eventually, for variability in the values of flux and obscuration.

Lanzuisi, Giorgio

2012-09-01

21

X-ray and EUV spectral instruments for plasma source characterization  

NASA Astrophysics Data System (ADS)

A set of spectral analytic instruments has been developed for absolute intensity measurements in a spectral range of 1 - 600 Å: (1) several modifications of grazing incidence spectrographs; (2) EUV monochromator- spectrometer with a constant angle of deviation; (3) focusing crystal von Hamos spectrometer using cylindrical mica and pyrolytic graphite crystals and a CCD linear array as a detector. These instruments are useful for plasma diagnostics, x-ray and EUV spectroscopy of laser-generated plasmas and capillary discharge plasmas, x-ray and EUV reflectometry, radiometry and x-ray fluorescence application.

Shevelko, Alexander P.; Kasyanov, Yuri S.; Knight, Larry V.; Phillips, James; Turley, R. Steven; Turner, D. Clark; Yakushev, Oleg F.

2004-01-01

22

Optimal material discrimination using spectral x-ray imaging  

NASA Astrophysics Data System (ADS)

Spectral x-ray imaging using novel photon counting x-ray detectors (PCDs) with energy resolving abilities is capable of providing energy-selective images. PCDs have energy thresholds, enabling the classification of photons into multiple energy bins. The extra energy information provided may allow materials such as iodine and calcium, or water and fat to be distinguishable. The information content of spectral x-ray images, however, depends on how the photons are grouped together. In this work, we present a model to optimize energy windows for maximum material discrimination. Multivariate statistics allows the confidence region of the correlated uncertainties to be mapped in the thickness space. Minimization of the uncertainties enables optimization of energy windows. Applications related to small animal imaging and breast imaging are considered.

Nik, S. J.; Meyer, J.; Watts, R.

2011-09-01

23

Spectral curvature behavior during X-ray flares in GRB afterglow emission  

NASA Astrophysics Data System (ADS)

One of the most impressive recent discovery of SWIFT is the evidence that X-ray flares occurring during the GRB afterglows are quite common, being observed in roughly 50% of the afterglows. These X-ray flares range fluences comparable with the GRB prompt emission and could be also repetitive. Several pictures have been proposed on their origin and among them the most accepted regards the internal shock scenario, interpreting the X-ray flares as late time activity of the GRB central engine. We propose to describe the spectral shape of the X-ray flares adopting the same physical model recently used to interpret the GRB prompt emission: the log-parabolic function. In particular, we show that their spectral energy distribution (SED) is remarkably curved, while no significant curvature appears in the underlying X-ray afterglow emission. In addition, the log-parabolic function is statistically favored with respect to other proposed spectral models. By using a time resolved spectral analysis, we show the evolution of the peak energy and the curvature parameters of the SED during the X-ray flares in two of the brightest GRBs afterglows observed by SWIFT. We found that in the X-ray flares there is an anti-correlation between the peak energy and the curvature, as expected in a stochastic acceleration scenario.

Massaro, F.; Grindlay, J. E.

2011-08-01

24

X-Ray Spectral Properties of Low-Mass X-Ray Binaries in Nearby Galaxies  

NASA Astrophysics Data System (ADS)

We have investigated the X-ray spectral properties of a collection of low-mass X-ray binaries (LMXBs) within a sample of 15 nearby early-type galaxies using proprietary and archival data from the Chandra X-Ray Observatory. We find that the spectrum of the sum of the sources in a given galaxy is remarkably similar from galaxy to galaxy when only sources with X-ray luminosities less than 1039 ergs s-1 (0.3-10 keV) are considered. Fitting these lower luminosity sources in all galaxies simultaneously with a power-law model led to a best-fit power-law exponent of ?=1.56+/-0.02 (90% confidence), and using a thermal bremsstrahlung model yielded kTbrem=7.3+/-0.3 keV. This is the tightest constraint to date on the spectral properties of LMXBs in external galaxies. The spectral properties of the LMXBs do not vary with galactic radius out to three effective radii. There is also no apparent difference between the spectral properties of LMXBs that reside within globular clusters and those that do not. We demonstrate how the uniformity of the spectral properties of LMXBs can lead to more accurate determinations of the temperature and metallicity of the hot gas in galaxies that have comparable amounts of X-ray emission from hot gas and LMXBs. Although few in number in any given galaxy, sources with luminosities of (1-2)×1039 ergs s-1 are present in 10 of the galaxies. The spectra of these luminous sources are softer than the spectra of the rest of the sources and are consistent with the spectra of Galactic black hole X-ray binary candidates when they are in their very high state. The spatial distribution of these sources is much flatter than the optical light distribution, suggesting that a significant portion of them must reside within globular clusters. The simplest explanation of these sources is that they are ~10-15 Msolar black holes accreting near their Eddington limit. The spectra of these sources are very different from those of ultraluminous X-ray sources (ULXs) that have been found within spiral galaxies, suggesting that the two populations of X-ray-luminous objects have different formation mechanisms. The number of sources with apparent luminosities above 2×1039 ergs s-1 when determined using the distance of the galaxy is equal to the number of expected background active galactic nuclei and thus appears not to be associated with the galaxy, indicating that very luminous sources are absent or very rare in early-type galaxies. The lack of ULXs within elliptical galaxies strengthens the argument that ULXs are associated with recent star formation.

Irwin, Jimmy A.; Athey, Alex E.; Bregman, Joel N.

2003-04-01

25

Image streak techniques: ISKRA-5 facility X-ray space-time and spectral characteristics recording  

SciTech Connect

Presented below are the X-ray image streak techniques used to study the spectral- and spectral-spatial time behavior of the ISKRA-5 facility laser-irradiated target X-ray radiation. For this purpose, we developed several 0.1-10 keV range X-ray slit streak cameras with 3x10{sup {minus}11}-s time resolution. Our X-ray imaging layout made it possible to simultaneously project several target images (in different spectral intervals) to the photocathode and streak them synchroniously. These techniques made it possible to: Study the microsphere target and plasma corona implosion dynamics; investigate the well-adjacent plasma electron temperature behavior; determine the compressed core lifetime; and monitor the state of the external (non-irradiated) target surface. 7 refs., 4 figs.

Lazarchuk, V.P.; Murugov, V.M.; Petrov, S.I.; Senik, A.V. [VNIIEF Russian Federal Nuclear Center, Novgorod (Russian Federation)

1994-12-31

26

X-ray Spectral Measurements of the JMAR High Power Laser-plasma Source  

NASA Astrophysics Data System (ADS)

X-ray spectra of Cu plasmas at the focus of a four-beam, solid-state diode-pumped laser have been recorded. This laser-plasma X-ray source is being developed for JMAR's lithography systems aimed at high- performance semiconductor integrated circuits. The unique simultaneous overlay of the four sub-nanosecond laser beams at 300 Hertz produces a bright, point-plasma X-ray source. PIN diode measurements of the X-ray output indicate that the conversion efficiency (ratio of X-ray emission energy into 2? steradians to incident laser energy) was approximately 9 percent with average X-ray power yields of greater than 10 Watts. Spectra were recorded on calibrated Kodak DEF film in a curved-crystal spectrograph. A KAP crystal (2d = 26.6 Angstroms) was used to disperse the 900 eV to 3000 eV spectral energies onto the film. Preliminary examination of the films indicated the existence of Cu and Cu XX ionization states. Additional spectra as a function of laser input power were also recorded to investigate potential changes in X-ray yields. These films are currently being analyzed. The analysis of the spectra provide absolute line and continuum intensities, and total X-ray output in the measured spectral range.

Whitlock, Robert R.; Dozier, Charles M.; Newman, Daniel A.; Turcu, I. C. Edmond; Gaeta, Celestino J.; Cassidy, Kelly L.; Powers, Michael F.; Kleindolph, Thomas; Morris, James H.; Forber, Richard A.

2002-09-01

27

X-ray Spectral Measurements of a Dense Plasma Focus  

NASA Astrophysics Data System (ADS)

Absolute intensities of spectra in a dense-plasma-focus (DPF) source have been recorded and analyzed. This DPF source has been identified as one of the more promising sources for X-ray lithography. The source, developed by Science Research Laboratory, Inc., is currently undergoing testing and further development at BAE Systems, Inc. The DPF operates at 60 Hz and produces an average output pulse of ~5 J of X rays into 4? steradians in a continuous operation mode. In all runs, there was an initial number of pulses, typically between 30 to 40, during which the X-ray output increased and the DPF appeared to be undergoing a conditioning process, and after which a "steady-state" mode was achieved where the average X-ray power was relatively constant. Each spectral run was exposed to ~600 J of output, as measured by the PIN. The X-ray spectral region between 0.8 and 3 keV was recorded on Kodak DEF film in a potassium acid phthalate (KAP) convex curved-crystal spectrograph. The source emits neon line radiation from Ne IX and Ne X ionization stages in the 900 to 1300 eV region, suitable for lithographic exposures of photoresist. Two helium-like neon lines contribute more than 50% of the total energy. From continuum shape, plasma temperatures were found to be approximately 170-200 eV. The absolute, integrated spectral outputs were verified to within 30% by comparison with measurements by a PIN detector and a radiachromic X-ray dosimeter.

Whitlock, Robert R.; Dozier, Charles M.; Newman, Daniel A.; Petr, Rodney A.; Freshman, Jay; Hoey, David W.; Heaton, John

2002-09-01

28

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

29

Tunable thin film polarizer for the vacuum ultraviolet and soft x-ray spectral regions  

NASA Astrophysics Data System (ADS)

A low pass polarizer that suppresses higher-order diffraction light from vacuum ultraviolet and soft x-ray monochromators is presented in this paper. This vacuum ultraviolet and soft x-ray polarizer is based on a concept of sandwiched metal-dielectric-metal triple reflection configuration. By appropriate optimization of material and angle of incidence, the proposed Au-SiC-Au polarizer demonstrates the capability of matching to desired cutoff edge of photon energy. Furthermore, the optimized soft x-ray polarizer shows the possibility to tune cutoff photon energy in a broadband spectral region ranging from 80 down to down to 20 eV.

Yang, Minghong; Cobet, Christoph; Esser, Norbert

2007-03-01

30

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

31

Advances toward high spectral resolution quantum X-ray calorimetry  

NASA Technical Reports Server (NTRS)

Thermal detectors for X-ray spectroscopy combining high spectral resolution and quantum efficiency have been developed. These microcalorimeters measure the energy released in the absorption of a single photon by sensing the rise in temperature of a small absorbing structure. The ultimate energy resolution of such a device is limited by the thermodynamic power fluctuations in the thermal link between the calorimeter and isothermal bath and can in principle be made as low as 1 eV. The performance of a real device is degraded due to noise contributions such as excess 1/f noise in the thermistor and incomplete conversion of energy into phonons. The authors report some recent advances in thermometry, X-ray absorption and thermalization, fabrication techniques, and detector optimization in the presence of noise. These improvements have resulted in a device with a spectral resolution of 17 eV FWHM, measured at 6 keV.

Moseley, S. H.; Kelley, R. L.; Schoelkopf, R. J.; Szymkowiak, A. E.; Mccammon, D.

1988-01-01

32

Different X-Ray Spectral Evolution for Black Hole X-Ray Binaries in Dual Tracks of Radio-X-Ray Correlation  

NASA Astrophysics Data System (ADS)

Recently, an "outlier" track of radio-X-ray correlation was found, which is much steeper than the former universal correlation, where dual tracks were speculated to be triggered by different accretion processes. In this work, we test this issue by exploring hard X-ray spectral evolution in four black-hole X-ray binaries with multiple, quasi-simultaneous radio and X-ray observations. First, we find that hard X-ray photon indices, ?, are negatively and positively correlated with X-ray fluxes when the X-ray flux, F 3-9 keV, is below and above a critical flux, F X, crit, which are consistent with predictions of the advection-dominated accretion flow and the disk-corona model, respectively. Second, and most importantly, we find that the radio-X-ray correlations are also clearly different when the X-ray fluxes are higher and lower than the critical flux as defined by X-ray spectral evolution. The data points with F 3-9 keV >~ F X, crit have a steeper radio-X-ray correlation (F_X\\propto F_R^{b} and b ~ 1.1-1.4), which roughly forms the "outlier" track. However, the data points with anti-correlation of ? - F 3-9 keV either stay in the universal track with b ~ 0.61 or stay in the transition track (from the universal to "outlier" tracks or vice versa). Therefore, our results support that the universal and "outlier" tracks of radio-X-ray correlations are regulated by radiatively inefficient and radiatively efficient accretion model, respectively.

Cao, Xiao-Feng; Wu, Qingwen; Dong, Ai-Jun

2014-06-01

33

Spectral Properties of X-Ray Binaries in Centaurus A  

NASA Astrophysics Data System (ADS)

We present a spectral investigation of X-ray binaries (XBs) 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 N H, and present the spectral parameters of sources with Lx >~ 2 × 1037 erg s-1. 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 M ?. 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 M ? to produce the observed peak luminosities. This requirement for more massive donors may also explain recent results that claim a steepening of the X-ray luminosity function with age at Lx >= 5 × 1038 erg s-1 for the XB population of early-type galaxies; for older stellar populations, there are fewer stars >~ 1 M ?, which are required to form the more luminous sources.

Burke, Mark J.; Raychaudhury, Somak; 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; Jordán, Andrés; Sarazin, Craig L.; Voss, Rasmus; Worrall, Diana M.; Zhang, Zhongli

2013-04-01

34

X-Ray Spectral Variation of eta Carinae through the 2003 X-Ray Minimum  

Microsoft Academic Search

We report the results of an observing campaign on eta Car around the 2003 X-ray minimum, mainly using the XMM-Newton observatory. These are the first spatially resolved X-ray monitoring observations of the stellar X-ray spectrum during the minimum. The hard X-ray emission, associated with the wind-wind collision (WWC) in the binary system, varied strongly in flux on timescales of days,

Kenji Hamaguchi; Michael F. Corcoran; Theodore Gull; Kazunori Ishibashi; Julian M. Pittard; D. John Hillier; Augusto Damineli; Kris Davidson; Krister E. Nielsen; Gladys Vieira Kober

2007-01-01

35

Spectral slicing X-ray telescope with variable magnification  

NASA Technical Reports Server (NTRS)

A telescope for viewing high frequency radiation (soft X-ray, extreme ultraviolet) is described. This telescope has a long focal length with a selection of magnifications despite a short housing. Light enters the telescope and is reflected by the telescope's primary optical system to one of several secondary mirrors at different locations on a movable frame. The secondary mirrors have varying degrees of magnification and select narrow spectral slices of the incident radiation. Thus, both the magnification and effective focal length field of view and wavelength can be altered by repositioning the moving frame. Configurations for spaceborne applications are discussed.

Hoover, R. B.; Hildner, E. (inventors)

1985-01-01

36

X-ray observations of spiral galaxies. II - Images and spectral parameters of 13 galaxies  

NASA Technical Reports Server (NTRS)

The results of a spatial and spectral analysis of a sample of spiral galaxies observed in X-rays with the Einstein satellite indicate that the X-ray emission is generally extended and complex. In some cases, discrete, very bright X-ray sources are detected, some of these coincident with the nuclear regions. The spectral fit of the IPC data to a thermal bremsstrahlung spectrum with a low-energy absorption cutoff shows that the average spectrum could be rather hard with kT greater than 2 keV, and with low-energy cutoff consistent with line-of-sight absorption. Results on NGC 4631, NGC 6946, and the nuclei of IC 342 and NGC 1313 are discussed and compared with previous observations in different energy ranges.

Fabbiano, G.; Trinchieri, G.

1987-01-01

37

SPECTRAL PROPERTIES OF X-RAY BINARIES IN CENTAURUS A  

SciTech Connect

We present a spectral investigation of X-ray binaries (XBs) 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 N{sub H}, and present the spectral parameters of sources with L{sub x} {approx}> 2 Multiplication-Sign 10{sup 37} erg s{sup -1}. 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 {approx}2-5 M{sub Sun }. We propose that BH LMXBs are preferentially found in the dust lane, and suggest this is because of the younger stellar population. The majority ({approx}70%-80%) of potential Roche lobe filling donors in the Cen A halo are {approx}> 12 Gyr old, while BH LMXBs require donors {approx}> 1 M{sub Sun} to produce the observed peak luminosities. This requirement for more massive donors may also explain recent results that claim a steepening of the X-ray luminosity function with age at L{sub x} {>=} 5 Multiplication-Sign 10{sup 38} erg s{sup -1} for the XB population of early-type galaxies; for older stellar populations, there are fewer stars {approx}> 1 M{sub Sun }, which are required to form the more luminous sources.

Burke, Mark J.; Raychaudhury, Somak [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)] [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Kraft, Ralph P.; Forman, William R.; Jones, Christine; Murray, Stephen S.; Birkinshaw, Mark; Evans, Daniel A.; Jordan, Andres [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Maccarone, Thomas J.; Croston, Judith H. [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)] [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Brassington, Nicola J.; Hardcastle, Martin J.; Goodger, Joanna L. [School of Physics, Astronomy, and Mathematics, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom)] [School of Physics, Astronomy, and Mathematics, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Kainulainen, Jouni [Max-Planck-Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)] [Max-Planck-Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Woodley, Kristin A. [Department of Physics and Astronomy, University of British Columbia, Vancouver BC V6T 1Z1 (Canada)] [Department of Physics and Astronomy, University of British Columbia, Vancouver BC V6T 1Z1 (Canada); Sivakoff, Gregory R. [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada)] [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada); Gilfanov, Marat [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85741, Garching (Germany)] [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85741, Garching (Germany); Sarazin, Craig L. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)] [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Voss, Rasmus, E-mail: mburke@star.sr.bham.ac.uk [Department of Astrophysics/IMAPP, Radboud, University Nijmegen, P.O. Box 9010, NL-6500 GL Nijmegen (Netherlands)] [Department of Astrophysics/IMAPP, Radboud, University Nijmegen, P.O. Box 9010, NL-6500 GL Nijmegen (Netherlands); and others

2013-04-01

38

The X-ray spectral properties of X-ray-selected AGN: ROSAT spectra of EMSS AGN  

Microsoft Academic Search

Using a sample of 63 active galactic nuclei (AGN) extracted from the Einstein Extended Medium Sensitivity Survey (EMSS), we study the X-ray spectral properties of X-ray-selected AGN in the 0.1-2.4 keV ROSAT band. These objects are all the EMSS AGN detected with more than 300 net counts in ROSAT Position Sensitive Proportional Counter (PSPC) images available from the public archive

Paolo Ciliegi; Tommaso Maccacaro

1996-01-01

39

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

40

X-ray spectral states of accreting black holes binaries  

NASA Astrophysics Data System (ADS)

I present INTEGRAL observations of the prototypical sources Cygnus X-1 and GX 339-4 in various X-ray spectral states (including during the TeV detection of Cygnus X-1 by MAGIC). Detailed spectral analysis of the evolution of these sources during state transitions allows us to follow the spectral evolution from the Low Hard State (LHS: dominated by thermal comptonisation) to the High Soft State (HSS: dominated by the accretion disc thermal emission and non-thermal comptonisation in the corona). Across the transition, the accretion disc luminosity increases by at least one order of magnitude while the comptonised coronal luminosity does not changes dramatically. We also attempt to model the observed spectra using a new Fokker-Planck code accounting for the so-called 'synchrotron boiler effect'. These numerical simulations indicate that in both spectral states the magnetised corona could be powered essentially through acceleration of non-thermal particles. The main differences between the LHS and HSS coronal emission can then be understood as the consequence of the strong cooling soft photon flux from the disc present in the HSS and absent in the LHS. This suggests that, contrary to current beliefs, the corona of the HSS and that of the LHS could be of very similar nature.

Malzac, Julien

41

X-ray spectral states of black holes binaries  

NASA Astrophysics Data System (ADS)

I present INTEGRAL observations of the prototypical sources Cygnus X-1 and GX 339-4 in various X-ray spectral states (including during the TeV detection of Cygnus X-1 by MAGIC). Detailed spectral analysis of the evolution of these sources during state transitions allows us to follow the spectral evolution from the Low Hard State (LHS: dominated by thermal comptonisation) to the High Soft State (HSS: dominated by the accretion disc thermal emission and non-thermal comptonisation in the corona). Across the transition, the accretion disc luminosity increases by at least one order of magnitude while the comptonised coronal luminosity does not changes dramatically. We also attempt to model the observed spectra using a new Fokker-Planck code accounting for the so-called 'synchrotron boiler effect'. These numerical simulations indicate that in both spectral states the magnetised corona could be powered essentially through acceleration of non-thermal particles. The main differences between the LHS and HSS coronal emission can then be understood as the consequence of the strong cooling soft photon flux from the disc present in the HSS and absent in the LHS. This suggests that, contrary to current beliefs, the corona of the HSS and that of the LHS could be of very similar nature.

Malzac, Julien

42

X-ray signatures: New time scales and spectral features  

NASA Technical Reports Server (NTRS)

The millisecond bursts from Cyg X-1 are investigated and the overall chaotic variability for the bulk of the Cyg X-1 emission is compared to that of Sco X-1, showing that the essential character is remarkably similar (i.e. shot noise) although the fundamental time scales involved differ widely, from a fraction of a second (for Cyg X-1) to a fraction of a day (for Sco X-1). Recent OSO-8 observations of spectra features attributable to iron are reviewed. In particular, line emission is discussed within the context of a model for thermal radiation by a hot evolved gas in systems as different as supernova remnants and clusters of galaxies. Newly observed spectral structure in the emission from the X-ray pulsar Her X-1 is reported.

Boldt, E. A.

1977-01-01

43

Recent advances in observations and modeling of ultraviolet and X-ray spectral irradiance  

Microsoft Academic Search

There have been significant recent advances in understanding the solar ultraviolet UV and X-ray spectral irradiance from the several different satellite missions and from new efforts in modeling the variations of the solar spectral irradiance The recent satellite missions with solar UV and X-ray spectral irradiance observations include the X-Ray Sensor XRS aboard the series of NOAA GOES spacecraft the

T. N. Woods

2006-01-01

44

Recent advances in observations and modeling of the solar ultraviolet and X-ray spectral irradiance  

Microsoft Academic Search

There have been significant, recent advances in understanding the solar ultraviolet (UV) and X-ray spectral irradiance from several different satellite missions and from new efforts in modeling the variations of the solar spectral irradiance. The recent satellite missions with solar UV and X-ray spectral irradiance observations include the X-ray Sensor (XRS) aboard the series of NOAA GOES spacecraft, the Upper

Thomas N. Woods

2008-01-01

45

Spectral variability of ultraluminous X-ray sources  

NASA Astrophysics Data System (ADS)

We study spectral variability of 11 ultraluminous X-ray sources (ULX) using archived XMM-Newton and Chandra observations. We use three models to describe the observed spectra: a power law, a multicolour disc (MCD) and a combination of these two models. We find that seven ULXs show a correlation between the luminosity LX and the photon index ?. Furthermore, four out of these seven ULXs also show spectral pivoting in the observed energy band. We also find that two ULXs show an LX-? anticorrelation. The spectra of four ULXs in the sample can be adequately fitted with a MCD model. We compare these sources to known black hole binaries (BHB) and find that they follow similar paths in their luminosity-temperature diagrams. Finally, we show that the `soft excess' reported for many of these ULXs at ~0.2 keV seems to roughly follow a trend Lsoft ~ T-3.5 when modelled with a power law plus a `cool' MCD model. This is contrary to the L ~ T4 relation that is expected from theory and what is seen for many accreting BHBs. The observed trend could instead arise from disc emission beamed by an outflowing wind around a ~10Msolar black hole.

Kajava, Jari J. E.; Poutanen, Juri

2009-09-01

46

Energy dependence of power-spectral noise in X-ray binaries  

NASA Astrophysics Data System (ADS)

Black hole and neutron star X-ray binaries show variability on time-scales ranging from milliseconds to years. In the last two decades a detailed phenomenological picture of short-term variability in low-mass X-ray binaries has emerged mainly based on RXTE observations that cover energies above 3 keV. This picture comprises periodic or quasi-periodic variability, seen as spikes or humps in power density spectra, that are superposed on broad noise components. The overall shape of the noise components as well as the occurrence of quasi-periodic oscillations is known to vary with the state of the X-ray binary. We are accomplishing a comprehensive study of archival XMM-Newton observations in timing or burst mode of more than ten black hole and more than thirty neutron star low-mass X-ray binaries to investigate the variability properties of these sources at softer energies where the thermal disk component starts to emerge.Here we present some results of the energy dependence of the noise component in power density spectra: a discussion of the energy dependence of the power spectral state that we found in the “plateau” state of GRS 1915+105 and the intermediate state of 4U 1630-47; the dependence of the break-frequency of the band-limited noise component as well as the quasi-periodic oscillations on the studied energy band in several X-ray binaries like GX 339-4 or Swift J1753.5-0127. We will discuss the implications of these findings for the picture of the accretion geometry in black hole X-ray binaries.

Stiele, Holger; Yu, Wenfei

2014-08-01

47

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

48

Broadband high resolution X-ray spectral analyzer  

DOEpatents

A broad bandwidth high resolution x-ray fluorescence spectrometer has a performance that is superior in many ways to those currently available. It consists of an array of 4 large area microcalorimeters with 95% quantum efficiency at 6 keV and it produces x-ray spectra between 0.2 keV and 7 keV with an energy resolution of 7 to 10 eV. The resolution is obtained at input count rates per array element of 10 to 50 Hz in real-time, with analog pulse processing and thermal pile-up rejection. This performance cannot be matched by currently available x-ray spectrometers. The detectors are incorporated into a compact and portable cryogenic refrigerator system that is ready for use in many analytical spectroscopy applications as a tool for x-ray microanalysis or in research applications such as laboratory and astrophysical x-ray and particle spectroscopy.

Silver, Eric H. (Berkeley, CA); Legros, Mark (Berkeley, CA); Madden, Norm W. (Livermore, CA); Goulding, Fred (Lafayette, CA); Landis, Don (Pinole, CA)

1998-01-01

49

Broadband high resolution X-ray spectral analyzer  

DOEpatents

A broad bandwidth high resolution X-ray fluorescence spectrometer has a performance that is superior in many ways to those currently available. It consists of an array of 4 large area microcalorimeters with 95% quantum efficiency at 6 keV and it produces X-ray spectra between 0.2 keV and 7 keV with an energy resolution of 7 to 10 eV. The resolution is obtained at input count rates per array element of 10 to 50 Hz in real-time, with analog pulse processing and thermal pile-up rejection. This performance cannot be matched by currently available X-ray spectrometers. The detectors are incorporated into a compact and portable cryogenic refrigerator system that is ready for use in many analytical spectroscopy applications as a tool for X-ray microanalysis or in research applications such as laboratory and astrophysical X-ray and particle spectroscopy. 6 figs.

Silver, E.H.; Legros, M.; Madden, N.W.; Goulding, F.; Landis, D.

1998-07-07

50

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

51

X-ray spectral indices of the Fermi/LAT blazars  

NASA Astrophysics Data System (ADS)

In this work, we analyze the X-ray spectral indices of the 245 Fermi-detected blazars. Relations between the ?-ray emission and the X-ray emission are our research focuses. Our analysis shows that: (1) the X-ray spectral indices of the Fermi/LAT-detected-blazars ( ? X| Fermi ), have similar distributions with those of non-Fermi-detected blazars ( ? X| non- Fermi ), and the averaged value ; (2) X-ray spectral indices are strong anti-correlated with the logarithmic Doppler factors, log( ?)=-(0.27±0.10) ? X +(1.09±0.14), with the correlative coefficient R=-0.33, the chance probability P=1.9 %; (3) X-ray spectral indices ( ? X ) and ?-ray spectral indices ( ? ? ) show strong anti-correlation, ? X =-(0.62±0.11) ? ? +(1.91±0.12), R=-0.35, P<0.001 %.

Yuan, Yuhai; Fan, Junhui

2014-07-01

52

Spectral-based 2D/3D X-ray to CT image rigid registration  

NASA Astrophysics Data System (ADS)

We present a spectral-based method for the 2D/3D rigid registration of X-ray images to a CT scan. The method uses a Fourier-based representation to decompose the six rigid transformation parameters problem into a twoparameter out-of-plane rotation and a four-parameter in-plane transformation problems. Preoperatively, a set of Digitally Reconstructed Radiographs (DRRs) are generated offline from the CT in the expected in-plane location ranges of the fluoroscopic X-ray imaging devices. Each DRR is transformed into a imaging device in-plane invariant features space. Intraoperatively, a few 2D projections of the patient anatomy are acquired with an X-ray imaging device. Each projection is transformed into its in-plane invariant representation. The out-of-plane parameters are first computed by maximization of the Normalized Cross-Correlation between the invariant representations of the DRRs and the X-ray images. Then, the in-plane parameters are computed with the phase correlation method based on the Fourier-Mellin transform. Experimental results on publicly available data sets show that our method can robustly estimate the out-of-plane parameters with accuracy of 1.5° in less than 1sec for out-of-plane rotations of 10° or more, and perform the entire registration in less than 10secs.

Freiman, M.; Pele, O.; Hurvitz, A.; Werman, M.; Joskowicz, L.

2011-03-01

53

X-Ray Spectral Variability in NGC 7469  

NASA Technical Reports Server (NTRS)

We present analyses of two Ginga observations and two observations from the ROSAT database of NGC 7469, focusing on the spectral variability observed on timescales of days and longer. During the 1988 Ginga observation, the hardness ratio (8-21 keV/3.4-5.7 keV) increased significantly as the total flux decreased by 30%. As the spectrum is well fit by the reflection model and since the spectra variability dominates the higher energy band, this could be explained by either a variation in the power law index or in the effective covering fraction of the reflecting material. This ambiguity is inherent in reflection modeling of Ginga spectra from moderate flux Seyfert 1 galaxies. Assuming that the power law index did not change, we find that the reflected flux is consistent with being constant, suggesting that much of the reflecting material may be located more than 3 light-days from the continuum source with the molecular torus being a plausible site. This scenario is also supported by the report of a narrow rather than broad iron K-alpha line in the ASCA data by Guainazzi et al. NGC 7469 was faint during the 1989 Ginga observation, but variability was observed with doubling timescale of 5 hr, and the spectrum was harder. A reflection component could not be constrained, and the change in the spectrum could be explained by an increase in neutral absorption. The brighter of two ROSAT spectra was significantly softer, and in both spectra there was evidence of spectral complexity, as has been previously reported by Turner, George, & Mushotzky and Brandt et al. The spectrum could be fit by a variety of two-component models, including a warm absorber model, an ionized disk model, and a thermal model with single-component blackbody spectrum, but joint fitting of the 1988 average Ginga spectrum and the nonsimultaneous ROSAT spectra favored thermal models, and other models required an anomalously high reflection ratio. This model is supported by the observation of a soft excess component and the lack of ionized absorption edges in the ASCA spectrum by Guainazzi et al. The long-term spectral variability could be explained by relative variability between the power-law and soft excess component normalizations, perhaps implying that hard X-ray reprocessing in thermal material does not dominate on long timescales.

Leighly, Karen; Kunieda, Hideyo; Awaki, Hisamitsu; Tsuruta, Sachiko

1996-01-01

54

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, Sagamihara /KIPAC, Menlo Park /Tokyo Metropolitan U. /Kogakuin U. /Columbia U., Astron. Astrophys.

2006-07-10

55

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

56

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

57

Unveiling Obscured AGN with X-ray Spectral Analysis  

NASA Astrophysics Data System (ADS)

The circumnuclear medium enshrouding AGN can now be thoroughly investigated in X-rays using physically motivated, self-consistent models that have recently become available. These advanced models allow reliable column densities (N_Hs) to be derived and can provide insight into the complex geometry of the X-ray reprocessor, constraining both the line-of-sight and global column densities. We fit the X-ray spectra of 19 SDSS [OIII] 5007 Angstrom selected type 2 AGN with these models. Though our sources represent an X-ray bright subset of the parent [OIII]-selected type 2 AGN samples, most are heavily obscured (N_H > 10^23 cm^-2) to Compton-Thick (N_H > 1.25 x 10^24 cm^-2). Four objects have different global and line-of-sight column densities. We correct the X-ray emission for absorption, calculating the intrinsic X-ray luminosity, and find that the mean Lx/L_[OIII] ratio for this sample is nearly equivalent to that of the average value for Seyfert 1 (i.e., unabsorbed) AGN.

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

2014-08-01

58

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

59

Spectral Characteristics of the Hard X Ray Emission from a Plasma Focus Device  

SciTech Connect

An indirect method to infer the spectra, based on the measurement of the beam intensity transmission through different metallic samples, is described in this communication. A Plasma Focus device (5.67 kJ, 30 kV) was studied as a pulsed hard x ray source, operated with deuterium at a filling pressure in the range of 3 to 5 mbar. Relevant spectral components belonging to the 50 - 150 keV range with a single maximum located in the 75 - 85 keV region were obtained for the radiation coming out of the Plasma Focus chamber, which is made of stainless steel.

Raspa, V.; Sigaut, L.; Moreno, C. [Laboratorio Plasma Focus - PLADEMA - Instituto de Fisica del Plasma - Departamento de Fisica, FCEyN - Universidad de Buenos Aires (Argentina); Vieytes, R. [Laboratorio Plasma Focus - PLADEMA - Instituto de Fisica del Plasma - Departamento de Fisica, FCEyN - Universidad de Buenos Aires (Argentina); Escuela Superior Tecnica Manuel N. Savio, EST (Argentina); Clausse, A. [Universidad Nacional del Centro, PLADEMA-CNEA - CONICET (Argentina)

2006-12-04

60

X-ray Spectral Fitting of AGN in the ChaMP  

NASA Astrophysics Data System (ADS)

X-ray selected AGN posess a wide range of absorption properties that challenge and broaden the concepts of AGN Unification. Objects that seem unabsorbed optically can show evidence for large absorbing columns in the X-rays, while heavily optically-reddened objects may show little such evidence. Most previous samples are heterogeneous both in selection and measurement. The Chandra Multiwavelength Project (ChaMP) is producing a large sample of X-ray selected AGN out to redshift 5 via deep optical followup of serendipitous sources in the Chandra archive. We have developed software which uses CIAO and Sherpa to to automatically extract ChaMP point source spectra and fit a variety of spectral models. We present the results of fitting and investigate the correlation of total gas absorption and continuum power-law index with luminosity, redshift, and spectral class. In addition to fitting each object individually, we make use of simultaneous fitting of many objects to improve the signal to noise within luminosity or redshift bins.

Aldcroft, T. L.; Silverman, J. D.; Green, P. J.; Kim, D.-W.; Barkhouse, W. A.; Cameron, R. A.; Mossman, A.; Wilkes, B. J.; Ghosh, H.; Jannuzi, B.

2004-10-01

61

The dynamic range of X-ray imaging with image plates  

NASA Astrophysics Data System (ADS)

The dynamic range of X-ray detection with image plates is investigated. A dynamic range larger than 10 8 in X-ray dose is experimentally observed using the Fastscan detector, which allows a wide range of sensitivity settings. At X-ray doses lower than 0.1 Gy a proportionality between photo-stimulated luminescence (PSL) intensity and X-ray dose is found, while at higher doses the PSL intensity starts to saturate. This saturation effect can be attributed to the coloration of heavily X-rayed image-plates by radiation-induced F-centers.

Thoms, M.

1997-02-01

62

Monochromatic focusing of subpicosecond x-ray pulses in the keV range  

NASA Astrophysics Data System (ADS)

An effective x-ray optical method to focus keV x-ray pulses shorter than one picosecond by using spherically or toroidally bent crystals is presented. The spectral, spatial, and time-dependent properties of focusing by two-dimensional bent crystals are calculated by considering geometrical effects, physical limitation in high performance crystal optics, and reflectivities obtained by x-ray diffraction theory. These properties are compared with first experimental results of focusing x rays from a plasma created by a laser pulse with 4.5 mJ energy and 100 fs pulse length. The x-ray signals, simultaneously obtained from a von Hámos spectrometer and two-dimensional bent crystals are compared and found in good agreement with theoretical data. The possibilities and aspects of laser pump x-ray probe experiments using this type of x-ray optics system and currently available laser systems are discussed.

Missalla, T.; Uschmann, I.; Förster, E.; Jenke, G.; von der Linde, D.

1999-02-01

63

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

64

Spectral resolution measurement of an x-ray imaging crystal spectrometer for KSTAR  

SciTech Connect

A spectral resolution measurement of the x-ray imaging crystal spectrometer for the Korea Superconducting Tokamak Advanced Research machine utilizing a segmented position-sensitive detector and time-to-digital converter based delay-line readout electronics was performed by using an x-ray tube in a laboratory. The measured spectral resolution is about 12 600, which means the actual energy resolution is 0.32 eV for the x-ray tube's bremsstrahlung peak energy of 4 keV. The results from the spectral resolution measurement are described.

Lee, S. G.; Bak, J. G. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Nam, U. W. [Korea Astronomy and Space Science Institute, 305-348 Daejeon (Korea, Republic of); Moon, M. K.; Cheon, J. K. [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Bitter, M.; Hill, K. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2008-10-15

65

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

66

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

67

Chemical bonding effects in X-ray spectral analysis  

Microsoft Academic Search

In this review we examine the use of chemical bonding effects apparent in x-ray spectra (chemical shift, change in shape and intensity of the lines) for qualitative and quantitative analysis of the chemical state of elements (charge state, valency, coordination number, chemical bond type, etc.), and also for direct identification of chemical compounds. In this connection, we examine methods of

L. N. Mazalov; B. A. Treiger

1983-01-01

68

Spectral Slicing X-Ray Telescope with Variable Magnification.  

National Technical Information Service (NTIS)

A telescope for viewing high frequency radiation (soft X-ray, extreme ultraviolet) is described. This telescope has a long focal length with a selection of magnifications despite a short housing. Light enters the telescope and is reflected by the telescop...

R. B. Hoover E. Hildner

1984-01-01

69

Spectral slicing X-ray telescope with variable magnification  

Microsoft Academic Search

A telescope for viewing high frequency radiation (soft X-ray, extreme ultraviolet) is described. This telescope has a long focal length with a selection of magnifications despite a short housing. Light enters the telescope and is reflected by the telescope's primary optical system to one of several secondary mirrors at different locations on a movable frame. The secondary mirrors have varying

R. B. Hoover; E. Hildner

1985-01-01

70

Practical energy response estimation of photon counting detectors for spectral X-ray imaging  

NASA Astrophysics Data System (ADS)

Spectral X-ray imaging is a promising technique to drastically improve the diagnostic quality of radiography and computed tomography (CT), since it enables material decomposition and/or identification based on the energy dependency of material-specific X-ray attenuation. Unlike the charge-integration based X-ray detectors, photon counting X-ray detectors (PCXDs) can discriminate the energies of incident X-ray photons and thereby multi-energy images can be obtained in single exposure. However, the measured data are not accurate since the spectra of incident X-rays are distorted according to the energy response function (ERF) of a PCXD. Thus ERF should be properly estimated in advance for accurate spectral imaging. This paper presents a simple method for ERF estimation based on a polychromatic X-ray source that is widely used for medical imaging. The method consists of three steps: source spectra measurement, detector spectra reconstruction, and ERF inverse estimation. Real spectra of an X-ray tube are first measured at all kVs by using an X-ray spectrometer. The corresponding detector spectra are obtained by threshold scans. The ERF is then estimated by solving the inverse problem. Simulations are conducted to demonstrate the concept of the proposed method.

Kang, Dong-Goo; Lee, Jongha; Sung, Younghun; Lee, Seongdeok

2010-03-01

71

X-Ray Spectral Properties of the BAT AGN Sample  

NASA Astrophysics Data System (ADS)

The 9-month Swift Burst Alert Telescope (BAT) catalog provides the first unbiased (NH < 1024 cm-2) look at local (langzrang = 0.03) active galactic nuclei (AGNs). In this paper, we present the collected X-ray properties (0.3-12 keV) for the 153 AGNs detected. In addition, we examine the X-ray properties for a complete sample of nonbeamed sources, above the Galactic plane (b >= 15°). Of these, 45% are best fit by simple power law models, while 55% require the more complex partial covering model. One of our goals was to determine the fraction of "hidden" AGNs, which we define as sources with scattering fractions less than or equal to 0.03 and ratios of soft to hard X-ray flux less than or equal to 0.04. We found that "hidden" AGNs constitute a high percentage of the sample (24%), proving that they are a very significant portion of local AGNs. Further, we find that the fraction of absorbed sources does increase at lower unabsorbed 2-10 keV luminosities, as well as accretion rates. This suggests that the unified model requires modification to include luminosity dependence, as suggested by models such as the "receding torus" model. Some of the most interesting results for the BAT AGN sample involve the host galaxy properties. We found that 33% are hosted in peculiar/irregular galaxies and only 5/74 are hosted in ellipticals. Further, 54% are hosted in interacting/merger galaxies. Finally, we present both the average X-ray spectrum (0.1-10 keV) and log N-log S in the 2-10 keV band. With our average spectrum, we have the remarkable result of reproducing the measured CXB X-ray power law slope of ? ? 1.4. From the log N-log S relationship, we show that we are complete to log S >= -11 in the 2-10 keV band. Below this value, we are missing as many as 3000 sources at log S = -12. Both the collected X-ray properties of our uniform sample and the log N-log S relationship will now provide valuable input to X-ray background models for z ? 0.

Winter, Lisa M.; Mushotzky, Richard F.; Reynolds, Christopher S.; Tueller, Jack

2009-01-01

72

Extended range X-ray telescope: X-ray microscope design  

NASA Technical Reports Server (NTRS)

A glancing incidence X-ray microscope using a confocal hyperboloid ellipsoid mirror was designed to couple optically a Wolter 1 telescope to a CCD focal plane detector. Both the RMS spot size and the point spread function calculations were used to evaluate the resolution, defocusing, and vignetting effects of the system for microscope focal lengths of 1, 1.5, and 2 meters and for magnifications varying from 2 to 10x. For the specific application with the S-056 telescope, a 2 meter, 8x microscope with a fabrication ratio of the microscope mirror length to the inner diameter at hyperboloid ellipsoid intersection of 2.5 was designed to be used with a thinned, back illuminated CCD detector array with 320 by 512, 30 micron pixels.

Shealy, D. L.; Kassim, A.; Chao, S.

1982-01-01

73

X-ray spectral power measurements utilizing the diffraction pattern of a slit  

NASA Astrophysics Data System (ADS)

An instrument is described which can obtain x-ray spectral power measurements utilizing the diffraction pattern produced when x rays pass through a slit. Traditionally, these types of measurements yielding low to moderate spectral resolution have been made with filtered x-ray diodes or with a transmission grating. The instrument described below has several advantages over filtered x-ray diodes in determining the spectral power profile such as an insensitivity to surface contamination. In addition, this instrument does not require the use of filters which can be destroyed during a shot making absolute measurements difficult and very time consuming. The advantages over a transmission grating system include cost, mechanical robustness, and fewer components which require spectral calibration.

Baker, K. L.; Porter, J. L.; Ruggles, L. E.; Chrien, R. E.; Idzorek, G. C.

1999-03-01

74

Direct spectral recovery using X-ray fluorescence measurements for material decomposition applications using photon counting spectral X-ray detectors  

NASA Astrophysics Data System (ADS)

We present investigations into direct, calibration-free recovery of distorted spectral x-ray measurements with the Medipix 2 detector. Spectral x-ray measurements using pixelated photon counting spectral x-ray detectors are subject to significant spectral distortion. For detectors with small pixel size, charge sharing between adjacent electrodes often dominates this distortion. In material decomposition applications, a popular spectral recovery technique employs a calibration phantom with known spectral properties. This works due to the similarity of the attenuation properties of the phantom and the material to be studied. However, this approach may be too simplistic for clinical imaging applications as it assumes the homogeneity (and knowledge) of exactly the properties whose variation accounts entirely for the diagnostic content of the spectral data obtained by the photon counting detector. It may also be difficult to find the right calibration phantom for varying patient size and tissue densities on a case-by-case basis. Thus, it is desirable to develop direct correction strategies, based on the objectively measurable response of the detector. We model analytically the distortion of a spectral signal in a PCSXD by applying Gaussian broadening and a charge-sharing model. The model parameters are fitted to the measured fluorescence of several metals. While we are investigating the methodology using Medipix detectors, it should be applicable to other PCXDs as well.

Campbell-Ricketts, Tom; Das, Mini

2014-03-01

75

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

76

X-ray spectral variation of the Crab Nebula in arc-second scale  

NASA Astrophysics Data System (ADS)

We present spectral analysis results of the Crab Nebula with the Chandra X-ray observatory. The Crab Nebula in X-ray wavelength shows an axisymmetric structure about the polar jet running in northeast-southwest direction. In the equatorial plane containing the Crab Pulsar, the torus and the inner ring can be seen. Chandra's imaging capability enables us to study a spatially-resolved spectroscopy of the Crab Nebula in arc-second scale. The spectral property characterized by power-law model varies across the nebula. From the spectroscopic point of view, the nebula can be divided into four regions: regions within the torus, the peripheral region of the torus, the jet, and the northwestern region of the torus. Spectra of region within the torus are the hardest of photon index ? of ˜ 1.9 and almost constant regardless of the surface brightness. On the contrary, at periphery of the torus, the spectrum gradually softens in outer and lower surface brightness regions up to ? of ˜ 2.5. Although the surface brightness of the jet is almost the same as those of the peripheral regions, the spectrum of the jet is harder with ? of ˜ 2.0. On the other hand, comparing the region within the torus, northwestern regions of the torus exhibit softer spectra although both regions have wide range of surface brightness of 0.2 -- 0.7 count sec-1 arcsec-2. A column density variation across the nebula is also indicated. Considering the spectral slope variation in the equatorial plane, it is suggested that the torus is a synchrotron burn-off boundary where the synchrotron loss becomes significant to X-ray emitting particle.

Mori, K.; Burrows, D. N.; Hester, J. J.; Tsunemi, H.

2002-12-01

77

Thermal X-Ray Spectral Tools. I. Parameterizing Impulsive X-Ray Heating with a Cumulative Initial Temperature (CIT) Distribution  

NASA Astrophysics Data System (ADS)

In collisional ionization equilibrium, the X-ray spectrum from a plasma depends on the differential emission measure (DEM), distributed over temperature. Due to the well-known ill conditioning problem, no precisely resolved DEM can be inverted directly from the spectrum, so often only a gross parameterization of the DEM is used to approximate the data, in hopes that the parameterization can provide useful model-independent constraints on the heating process. However, ill conditioning also introduces ambiguity into the various different parameterizations that could approximate the data, which may spoil the perceived advantages of model independence. Thus, this paper instead suggests a single parameterization for both the heating mechanism and the X-ray sources, based on a model of impulsive heating followed by radiative cooling. This approach is similar to a "cooling flow" approach but allows injection at multiple initial temperatures and applies even when the steady state is a distribution of different shock strengths, as for a standing shock with a range of obliquities, or for embedded stochastic shocks that are only steady in a statistical sense. This produces an alternative parameterization for X-ray spectra that is especially streamlined for higher density plasmas with efficient radiative cooling and minimal thermal conduction and mixing. The method also provides some internal consistency checks on the validity of its assumptions. A heuristic general version is then applied over a wide range of astrophysical applications to schematically explore potential alternative models for these phenomena.

Gayley, Kenneth G.

2014-06-01

78

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

79

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

80

TW Hya: Spectral Variability, X-Rays, and Accretion Diagnostics  

NASA Astrophysics Data System (ADS)

The nearest accreting T Tauri star, TW Hya was intensively and continuously observed over ~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? 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? 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? and H? lines is followed by He I (?5876) broadening near the photosphere. Optical veiling resulting from the heated photosphere increases with a delay of ~2 hr after the X-ray accretion event. The response of the stellar coronal emission to an increase in the veiling follows ~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.; Bessell, M. S.; Bonanos, A.; Crause, L. A.; Lawson, W. A.; Mallik, S. V.; Schuler, S. C.

2012-05-01

81

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

82

X-ray spectral analysis of niobium hydroxide  

SciTech Connect

The authors have derived an x-ray method of determining Ta/sub 2/O/sub 5/, TiO/sub 2/, Fe/sub 2/O/sub 3/, Nb/sub 2/O/sub 5/, C1 and SiO2 with a KRF-18 quantometer. The method should provide accuracy in determining these elements characterized by relative derivations. The main components of niobium hydroxide were ground for improved determination. The method allows one to analyze a sample in 30 min. In a six hour working day, an assistant can analyze up to 25 samples. The time required for one sample in the chemical method is about 30 hours.

Khabeev, I.A.; Belkina, V.A.; Makarova, R.V.; Mel'nikova, R.A.; Smagunova, A.N.

1986-02-01

83

The Far-Infrared Spectral Energy Distributions of X-Ray-selected Active Galaxies  

NASA Astrophysics Data System (ADS)

Hard X-ray selection is, arguably, the optimal method for defining a representative sample of active galactic nuclei (AGNs). Hard X-rays are unbiased by the effects of obscuration and reprocessing along the line of sight intrinsic/external to the AGN, which result in unknown fractions of the population being missed from traditional optical/soft X-ray samples. We present the far-infrared (far-IR) observations of 21 hard X-ray-selected AGNs from the HEAO 1 A2 sample observed with Infrared Space Observatory (ISO). We characterize the far-IR continua of these X-ray-selected AGNs and compare them with those of various radio and optically selected AGN samples and with models for an AGN-heated, dusty disk. The X-ray-selected AGNs show broad, warm IR continua covering a wide temperature range (~20-1000 K in a thermal emission scenario). Where a far-IR turnover is clearly observed, the slopes are less than 2.5 in all but three cases so that nonthermal emission remains a possibility, although the presence of cooler dust resulting in a turnover at wavelengths longward of the ISO range is considered more likely. The sample also shows a wider range of optical/UV shapes than the optical/radio-selected samples, extending to redder near-IR colors. The bluer objects are type 1 Seyfert galaxies, while the redder AGNs are mostly intermediate or type 2 Seyfert galaxies. This is consistent with a modified unification model in which obscuration increases as we move from a face-on toward a more edge-on line of sight. However, this relation does not extend to the mid-infrared as the 25/60 ?m ratios are similar in Seyfert galaxies with differing type and optical/UV reddening. The resulting limits on the column density of obscuring material through which we are viewing the redder AGNs (NH~1022 cm-2) are inconsistent with standard optically thick torus models (NH~1024 cm-2) and simple unification models. Instead our results support more complex models in which the amount of obscuring material increases with viewing angle and may be clumpy. Such a scenario, already suggested by differing optical/near-IR spectroscopic and X-ray AGN classifications, allows for different amounts of obscuration of the continuum emission in different wave bands and of the broad emission line region, which, in turn, results in a mixture of behaviors for AGNs with similar optical emission-line classifications. The resulting decrease in the optical depth of the obscuring material also allows the AGN to heat more dust at larger radial distances. We show that an AGN-heated, flared, dusty disk with mass of ~109 Msolar and size of approximately a few hundred parsecs is able to generate optical-far-IR spectral energy distributions (SEDs) that reproduce the wide range of SEDs present in our sample with no need for an additional starburst component to generate the long-wavelength, cooler part of the IR continuum. Based on observations with the Infrared Space Observatory, which is an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.

Kuraszkiewicz, Joanna K.; Wilkes, Belinda J.; Hooper, Eric J.; McLeod, Kim K.; Wood, Kenneth; Bjorkman, Jon; Delain, Kisha M.; Hughes, David H.; Elvis, Martin S.; Impey, Chris D.; Lonsdale, Carol J.; Malkan, Matt A.; McDowell, Jonathan C.; Whitney, Barbara

2003-06-01

84

Multivariate statistical analysis for x-ray photoelectron spectroscopy spectral imaging: Effect of image acquisition time  

Microsoft Academic Search

The acquisition of spectral images for x-ray photoelectron spectroscopy (XPS) is a relatively new approach, although it has been used with other analytical spectroscopy tools for some time. This technique provides full spectral information at every pixel of an image, in order to provide a complete chemical mapping of the imaged surface area. Multivariate statistical analysis techniques applied to the

D. E. Peebles; J. A. Ohlhausen; P. G. Kotula; S. Hutton; C. Blomfield

2004-01-01

85

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

NASA Astrophysics Data System (ADS)

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 ratio 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 high-mass X-ray binaries, 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. Based on astronomical observations at the European Southern Observatory La Silla in programmes 077.D-0415 and 079.D-0371. E-mail: vanessa@soton.ac.uk (VAM)

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

2008-08-01

86

Facilities and techniques for x-ray diagnostic calibration in the 100-eV to 100-keV energy range  

SciTech Connect

The Lawrence Livermore National Laboratory (LLNL) has been a pioneer in the field of x-ray diagnostic calibration for more than 20 years. We have built steady state x-ray sources capable of supplying fluorescent lines of high spectral purity in the 100-eV to 100-keV energy range, and these sources have been used in the calibration of x-ray detectors, mirrors, crystals, filters, and film. This paper discusses our calibration philosophy and techniques, and describes some of our x-ray sources. Examples of actual calibration data are presented as well.

Gaines, J.L.; Wittmayer, F.J.

1986-06-01

87

Metrology in the soft x-ray range: from EUV to the water window  

NASA Astrophysics Data System (ADS)

Metrology in the soft X-ray range has various applications ranging from instrumentation for solar astronomy to plasma experiments and EUV Lithography. The Physikalisch-Technische Bundesanstalt (PTB) with its laboratory at the electron storage ring BESSY II is a centre of soft X-ray radiometry and supports national and European research and development by carrying out high-accuracy at-wavelength measurements. The absolute detection efficiency of entire detection systems, diodes or cameras can be traced to SI units with a typical relative uncertainty of 0.5 % to 1 % using a cryogenic electrical substitution radiometer. For reflectometry on multilayer mirrors (MLMs) PTB operates a large reflectometer accommodating samples of up to 550 mm in diameter and 50 kg in weight, allowing sample alignment in 6 degrees of freedom. The relative measurement uncertainty for the spectral reflectance is typically in the range of 0.15 % and the long-term reproducibility in the range of 0.10 %. To investigate roughness, scatterometry is employed where scattered light around the specular beam is mapped using a calibrated CCD.

Laubis, Christian; Scholze, Frank; Ulm, Gerhard

2008-09-01

88

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

89

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

NASA Astrophysics Data System (ADS)

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.; 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

90

THE CORRELATION BETWEEN X-RAY LINE IONIZATION AND OPTICAL SPECTRAL TYPES OF THE OB STARS  

SciTech Connect

Marked correlations are reported between the ionization of the X-ray line spectra of normal OB stars, as observed by the Chandra X-Ray Observatory, and their optical spectral types. These correlations include the progressive weakening of the higher ionization relative to the lower ionization X-ray lines with advancing spectral type, and the similarly decreasing intensity ratios of the H-like to He-like lines of the alpha ions. These relationships were not predicted by models, nor have they been clearly evident in astrophysical studies of a few objects; rather, they have emerged from morphological analysis of an adequate (albeit still small) sample, from which known peculiar objects such as magnetic stars and very rapid rotators have been isolated to reveal the normal trends. This process is analogous to that which first demonstrated the strong relationships between the UV wind profiles and the optical spectral types of normal OB stars, which likely bear a physical as well as a historical connection to the present X-ray results. Since the optical spectral types are calibrated in terms of fundamental stellar parameters, it follows that the winds and X-ray spectra are determined by the latter. These observations provide strong guidance for further astrophysical modeling of these phenomena.

Walborn, Nolan R. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Nichols, Joy S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Waldron, Wayne L., E-mail: walborn@stsci.ed, E-mail: jnichols@cfa.harvard.ed, E-mail: wwaldron@satx.rr.co [Eureka Scientific, Inc., 2452 Delmer Street, Suite 100, Oakland, CA 94602 (United States)

2009-09-20

91

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

92

Spectral response calibrations of x-ray diode photocathodes in the 50-5900 eV photon energy region  

NASA Astrophysics Data System (ADS)

X-ray diode photocathodes are employed in diagnostic instruments on the Helen laser at the Atomic Weapons Establishment (AWE) Aldermaston, UK. The photocathodes are mainly used in the Dante fast diode array and flat response diodes. These diagnostics enable the soft x-ray spectral emissions of laser irradiated targets to be determined. To derive quantitative spectral information, the quantum efficiency of the photocathodes must be known over the range of x-ray energies of interest. The photocathodes were manufactured in 1982, and were initially calibrated at that time. Since then further measurements have been performed in 1988 and 1999. The photocathodes have been exposed to a wide range of conditions during their lives, ranging from use in experiments to storage in a dry nitrogen environment. Reported here are the results of calibrations performed in 1999 at the soft x-ray calibration facility EXCALIBUR at AWE, Aldermaston, and at the National Synchrotron Light Source in Brookhaven NY. An assessment of their current condition and an evaluation of the change in their response over time, and the possible reasons for these changes, are made.

Bentley, C. D.; Simmons, A. C.

2001-01-01

93

Long-term wind-driven X-ray spectral variability of NGC 1365 with Swift  

NASA Astrophysics Data System (ADS)

We present long-term (months-years) X-ray spectral variability of the Seyfert 1.8 galaxy NGC 1365 as observed by Swift, which provides well-sampled observations over a much longer time-scale (six years) and a much larger flux range than is afforded by other observatories. At very low luminosities, the spectrum is very soft, becoming rapidly harder as the luminosity increases and then, above a particular luminosity, softening again. At a given flux level, the scatter in hardness ratio is not very large, meaning that the spectral shape is largely determined by the luminosity. The spectra were therefore summed in luminosity bins and fitted with a variety of models. The best-fitting model consists of two power laws, one unabsorbed and another, more luminous, which is absorbed. In this model, we find a range of intrinsic 0.5-10.0 keV luminosities of approximately 1.1-3.5 erg s-1, and a very large range of absorbing columns, of approximately 1022-1024 cm-2. Interestingly, we find that the absorbing column decreases with increasing luminosity, but that this result is not due to changes in ionization. We suggest that these observations might be interpreted in terms of a wind model in which the launch radius varies as a function of ionizing flux and disc temperature and therefore moves out with increasing accretion rate, i.e. increasing X-ray luminosity. Thus, depending on the inclination angle of the disc relative to the observer, the absorbing column may decrease as the accretion rate goes up. The weaker, unabsorbed, component may be a scattered component from the wind.

Connolly, S. D.; McHardy, I. M.; Dwelly, T.

2014-06-01

94

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

95

Experimental measurements of selenium x-ray laser spectral line profiles  

SciTech Connect

The authors discuss their recent measurements of the spectral width of the 206.38 {Angstrom} x-ray laser transition in Ne-like Se. These measurements used a high-resolution grating spectrometer and were performed over a wide range of laser amplifier lengths. The data have enabled them to extrapolate the intrinsic line width and to observe the effects of gain-narrowing and saturation on the line profile. They find an intrinsic width which is 1.4 times the Doppler width, they observe gain-narrowing in intermediate length amplifiers, and they observe no re-broadening in long, saturated amplifiers. These results suggest that collisional line-broadening has a significant effect on the line profile and saturation behavior of this laser.

Koch, J.A.; MacGowan, B.J.; Da Silva, L.B.; Matthews, D.L.; London, R.A.; Lee, R.W.; Mrowka, S. [Lawrence Livermore National Lab., CA (US); Underwood, J.H.; Batson, P.J. [Lawrence Berkeley Lab., CA (US)

1993-03-01

96

Simulation of experimental investigations of X-ray spectral path lengths on Iskra-5 laser facility  

NASA Astrophysics Data System (ADS)

We describe an improved Slater average-ion model employed in the numerical-theoretical analysis of experimental data, which were obtained in the investigation of X-ray spectral path lengths performed on the Iskra-5 laser facility at the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF). The proposed model permits determining the spectral characteristics of the X-ray radiation with an accuracy of a few electronvolts. We outline the results of simulations of experiments with X-ray radiation-heated aluminium and germanium specimens of initial thickness of ~0.1 mm, in which absorption lines arising from 1s—2p transitions in Al and the absorption band arising from 2p—3d transitions in Ge were recorded.

Bel'kov, S. A.; Sharov, O. O.

2011-10-01

97

Simulation of experimental investigations of X-ray spectral path lengths on Iskra-5 laser facility  

SciTech Connect

We describe an improved Slater average-ion model employed in the numerical-theoretical analysis of experimental data, which were obtained in the investigation of X-ray spectral path lengths performed on the Iskra-5 laser facility at the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF). The proposed model permits determining the spectral characteristics of the X-ray radiation with an accuracy of a few electronvolts. We outline the results of simulations of experiments with X-ray radiation-heated aluminium and germanium specimens of initial thickness of {approx}0.1 mm, in which absorption lines arising from 1s-2p transitions in Al and the absorption band arising from 2p-3d transitions in Ge were recorded.

Bel'kov, S A; Sharov, O O [Russian Federal Nuclear Center 'All-Russian Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation)

2011-10-31

98

[Measurement technology for multi-parameter spectral responsivity of X-ray scintillation crystals].  

PubMed

Aimed at the measurement demand for development of better X-ray scintillation crystals, a photoelectrical detector for integrally test the multi-parameter spectral responsivity of scintillation crystals was developed. The conversion spectrum of the scintillation crystal excited by various X-ray energies under the critical focal length could be measured directly through the spectral output interface by one spectrometer, and the photovoltaic effect voltage of the PIN photodiode could be tested through the voltage output interface by one oscilloscope. Furthermore, the output power of fluorescence was calculated using an equivalent circuit. The measurement results show that the conversion efficiency of the scintillator declined along with the current increase of the X-ray tube while it has weak relation with the change in tube voltage. The experimental results show that the method presented in this paper is helpful for testing the scintillator properties. PMID:20939335

Li, Rui-hong; Han, Yue-ping; Zhou, Han-chang; Han, Yan

2010-08-01

99

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

100

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.

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

2012-01-01

101

New consistency tests for high-accuracy measurements of X-ray mass attenuation coefficients by the X-ray extended-range technique  

SciTech Connect

An extension of the X-ray extended-range technique is described for measuring X-ray mass attenuation coefficients by introducing absolute measurement of a number of foils - the multiple independent foil technique. Illustrating the technique with the results of measurements for gold in the 38-50 keV energy range, it is shown that its use enables selection of the most uniform and well defined of available foils, leading to more accurate measurements; it allows one to test the consistency of independently measured absolute values of the mass attenuation coefficient with those obtained by the thickness transfer method; and it tests the linearity of the response of the counter and counting chain throughout the range of X-ray intensities encountered in a given experiment. In light of the results for gold, the strategy to be ideally employed in measuring absolute X-ray mass attenuation coefficients, X-ray absorption fine structure and related quantities is discussed.

Chantler, C.T.; Islam, M.T.; Rae, N.A.; Tran, C.Q.; Glover, J.L.; Barnea, Z. (La Trobe); (Melbourne)

2012-09-25

102

An X-Ray Free-Electron Laser Oscillator for Record High Spectral Purity and Average Brightness (Progress and Prospects for X-ray Free Electron Lasers)  

SciTech Connect

With the success of the LCLS at SLAC, synchrotron radiation community is entering the era of x-ray free-electron lasers (FELs) with an enormous jump in brightness and coherence over that possible with third-generation x-ray sources. The LCLS is a single-pass, high-gain device producing quasi-coherent x-rays known as self-amplified spontaneous emission. Hard x-ray FELs are also feasible in an oscillator (XFELO) configuration, in which an x-ray pulse is trapped a low-loss optical cavity consisting of diamond crystals, permitting build-up in the intensity and coherence over several hundred passes. An XFELO produces ultrahigh spectral purity and brightness-average brightness several orders of magnitude higher than, and peak brightness comparable to, self-amplified spontaneous emission devices; opening up new scientific opportunities as well as drastically improving and complementing experimental techniques developed at third-generation x-ray facilities. We discuss unique R&D issues in accelerator and x-ray optics and encouraging progress to date.

Kim, Kwang-Je (ANL) [ANL

2009-06-24

103

A Catalog of 157 X-ray Spectra and 84 Spectral Energy Distributions of Blazars Observed with BeppoSAX  

NASA Astrophysics Data System (ADS)

As a special contribution to the proceedings of the BeppoSAX workshop dedicated to blazar astrophysics we present a catalog of 157 X-ray spectra and the broad-band Spectral Energy Distribution (SED) of 84 blazars observed by BeppoSAX during its first five years of operations. The SEDs have been built by combining BeppoSAX LECS, MECS and PDS data with (mostly) non-simultaneous multi-frequency photometric data, obtained from NED and from other large databases, including the GSC2 and the 2MASS surveys. All BeppoSAX data have been taken from the public archive and have been analysed in a uniform way. For each source we present a nu f(nu) vs nu plot, and for every BeppoSAX observation we give the best fit parameters of the spectral model that best describes the data. The energy where the maximum of the synchrotron power is emitted spans at least six orders of magnitudes ranging from about 0.1 eV to over 100 keV. A wide variety of X-ray spectral slopes have been seen depending on whether the synchrotron or inverse Compton component, or both, are present in the X-ray band. The wide energy bandpass of BeppoSAX allowed us to detect, and measure with good accuracy, continuous spectral curvature in many objects whose synchrotron radiation extends to the X-ray band. This convex curvature, which is described by a logarithmic parabola law better than other models, may be the spectral signature of a particle acceleration process that becomes less and less efficient as the particles energy increases. Finally some brief considerations about other statistical properties of the sample are presented.

Giommi, P.; Capalbi, M.; Fiocchi, M.; Memola, E.; Perri, M.; Piranomonte, S.; Rebecchi, S.; Massaro, E.

104

Anticipating HESSI's View of Spectral Evolution in Flare Hard X-Ray Emission  

NASA Technical Reports Server (NTRS)

The spectral evolution of observed flares' hard X-ray emission is found to conform to certain patterns in color-color diagrams (CCDs). By combining the spectral resolution of BATSE data with the spatial resolution of HXT data, we are able to address the nature of flare energy release and anticipate what kind of observations HESSI may make of the energy release/particle acceleration site in flares. The implications of these observations for theoretical models of acceleration and propagation is considered.

Newton, Elizabeth K.; Miller, James A.

1999-01-01

105

Processing of spectral X-ray data with principal components analysis  

Microsoft Academic Search

The goal of the work was to develop a general method for processing spectral x-ray image data. Principle component analysis (PCA) is a well understood technique for multivariate data analysis and so was investigated. To assess this method, spectral (multi-energy) computed tomography (CT) data was obtained using a Medipix2 detector in a MARS-CT (Medipix All Resolution System). PCA was able

Anthony P. H. Butler; Jochen Butzer; Nanette Schleich; Nicholas J. Cook; Nigel G. Anderson; Nicola Scott; Niels de Ruiter; Raphael Grasset; Lukas Tlustos; Philip H. Butler

2011-01-01

106

X-RAY SPECTRAL CONSTRAINTS FOR z {approx} 2 MASSIVE GALAXIES: THE IDENTIFICATION OF REFLECTION-DOMINATED ACTIVE GALACTIC NUCLEI  

SciTech Connect

We use the 4 Ms Chandra Deep Field-South (CDF-S) survey to place direct constraints on the ubiquity of z {approx} 2 heavily obscured active galactic nuclei (AGNs) in K < 22 BzK-selected galaxies. Forty-seven ({approx}21%) of the 222 BzK-selected galaxies in the central region of the CDF-S are detected at X-ray energies, 11 ({approx}5%) of which have hard X-ray spectral slopes ({Gamma} {approx}< 1), indicating the presence of heavily obscured AGN activity (N{sub H} {approx}> 3 x 10{sup 23} cm{sup -2}). The other 36 X-ray detected BzK galaxies appear to be relatively unobscured AGNs and starburst galaxies; we use X-ray variability analyses over a rest-frame baseline of {approx}3 years to further confirm the presence of AGN activity in many of these systems. The majority (7 out of 11) of the heavily obscured AGNs have excess infrared emission over that expected from star formation (termed 'infrared-excess galaxies'). However, we find that X-ray detected heavily obscured AGNs only comprise {approx}25% of the infrared-excess galaxy population, which is otherwise composed of relatively unobscured AGNs and starburst galaxies. We find that the typical X-ray spectrum of the heavily obscured AGNs is better characterized by a pure reflection model than an absorbed power-law model, suggesting extreme Compton-thick absorption (N{sub H} {approx}> 10{sup 24} cm{sup -2}) in some systems. We verify this result by producing a composite rest-frame 2-20 keV spectrum, which has a similar shape as a reflection-dominated X-ray spectrum and reveals an emission feature at rest-frame energy {approx}6.4 keV, likely to be due to Fe K. These heavily obscured AGNs are likely to be the distant analogs of the reflection-dominated AGNs recently identified at z {approx} 0 with >10 keV observatories. On the basis of these analyses, we estimate the space density for typical (intrinsic X-ray luminosities of L{sub 2-10keV} {approx}> 10{sup 43} erg s{sup -1}) heavily obscured and Compton-thick AGNs at z {approx} 2. Our space-density constraints are conservative lower limits but they are already consistent with the range of predictions from X-ray background models.

Alexander, D. M.; Hickox, R. C.; Del Moro, A.; Goulding, A. D.; Mullaney, J. R. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Bauer, F. E. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Brandt, W. N.; Luo, B.; Xue, Y. Q.; Young, M.; Rafferty, D. A.; Schneider, D. P. [Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States); Daddi, E. [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/SAp, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Lehmer, B. D. [The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Comastri, A.; Gilli, R. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-04127 Bologna (Italy); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Mainieri, V. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Paolillo, M. [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', Complesso Universitario di Monte S. Angelo V. Cinthia, 9, I-80126 Napoli (Italy); Shemmer, O. [Department of Physics, University of North Texas, Denton, TX 76203 (United States)

2011-09-01

107

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

Microsoft Academic Search

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 alphaE=1.8+2.1,-1.4 and no evidence for absorption in excess

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

1994-01-01

108

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

109

C IV EMISSION AND THE ULTRAVIOLET THROUGH X-RAY SPECTRAL ENERGY DISTRIBUTION OF RADIO-QUIET QUASARS  

SciTech Connect

In the rest-frame ultraviolet (UV), two of the parameters that best characterize the range of emission-line properties in quasar broad emission-line regions are the equivalent width and the blueshift of the C IV {lambda}1549 line relative to the quasar rest frame. We explore the connection between these emission-line properties and the UV through X-ray spectral energy distribution (SED) for radio-quiet (RQ) quasars. Our sample consists of a heterogeneous compilation of 406 quasars from the Sloan Digital Sky Survey (at z > 1.54) and Palomar-Green survey (at z < 0.4) that have well-measured C IV emission-line and X-ray properties (including 164 objects with measured {Gamma}). We find that RQ quasars with both strong C IV emission and small C IV blueshifts can be classified as 'hard-spectrum' sources that are (relatively) strong in the X-ray as compared to the UV. On the other hand, RQ quasars with both weak C IV emission and large C IV blueshifts are instead 'soft-spectrum' sources that are (relatively) weak in the X-ray as compared to the UV. This work helps to further bridge optical/soft X-ray 'eigenvector 1' relationships to the UV and hard X-ray. Based on these findings, we argue that future work should consider systematic errors in bolometric corrections (and thus accretion rates) that are derived from a single mean SED. Detailed analysis of the C IV emission line may allow for SED-dependent corrections to these quantities.

Kruczek, Nicholas E.; Richards, Gordon T.; Deo, Rajesh P.; Krawczyk, Coleman M. [Department of Physics, Drexel University, Philadelphia, PA 19104 (United States); Gallagher, S. C. [Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada); Hall, Patrick B. [Department of Physics and Astronomy, York University, Toronto, Ontario M3J 1P3 (Canada); Hewett, Paul C. [Institute of Astronomy, Cambridge CB3 0HA (United Kingdom); Leighly, Karen M. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Proga, Daniel [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 891541 (United States)

2011-10-15

110

X-Ray Spectral and Temporal Studies of the Ultra-Compact System X1916-05  

NASA Technical Reports Server (NTRS)

Rossi x-ray timing Explorer (RXTE) Cycle 1 data on the ultra-compact low mass x- ray binary (LMXB) X1916-05 is analyzed. In this current report, the scientific objectives of this investigation of hard x-ray studies of bursters and the results achieved are summarized. The scientific objectives are: (1) Period of the x-ray dips in X1916-05; (2) Phase stability of the x-ray dip period; (3) Spectral break energy and its dependence on mass transfer rate; and (4) Qpos detected from this LMXB. A list of published papers resulted from this project is also included.

Grindlay, Jonathan E.

1998-01-01

111

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

112

Correlations between Spectral Properties and Spin-down Rate in Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars  

Microsoft Academic Search

Anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are X-ray sources with unusual properties distinguishing them from both rotation-powered and most accretion-powered pulsars. Using archival ASCA data over the energy range 0.5-10.0 keV, we have studied the spectra of the persistent emission from these sources and their variation with spin-down rate. Using a single-power-law spectral model, we find that

D. Marsden; N. E. White

2001-01-01

113

X-Ray Spectral and Timing Behavior of Scorpius X-1. Spectral Hardening during the Flaring Branch  

NASA Astrophysics Data System (ADS)

We present an analysis of the spectral and timing properties of X-ray emission from the Z-source Sco X-1 during its evolution between the horizontal (HB) and flaring (FB) branches observed with the Rossi X-ray Timing Explorer during the 1996-2002 period. We find that the broadband (3-250 keV) energy spectra during all spectral states can be adequately reproduced by a model, consisting of two Comptonized components and an iron line. We suggest that the seed photons of kT s1 <~ 0.7 keV coming from the disk and of temperature kT s2 <~ 1.8 keV coming from the neutron star (NS) are each upscattered by hot electrons of a "Compton cloud" (hereafter the Comptb1 and Comptb2 components, respectively, which are associated with the similarly subscripted parameters). The photon power-law index ?2 is almost constant (?2 ~ 2) for all spectral states. In turn, ?1 demonstrates a two-phase behavior with the spectral state: ?1 is quasi-constant at the level ?1 ~ 2 for the HB–NB and ?1 is less than 2, namely in the range of 1.3 < ?1 < 2, when the source traces the FB. We also detect a decrease kT s2 from 1.8 keV to 0.7 keV during the FB. We interpret this apparent quasi-stability of the indices during the HB–NB in the framework of the model in which the spectrum is determined by the Comptonized thermal components. This effect established for the Comptonized spectral components of the Z-source Sco X-1 is similar to what was previously found in the atoll sources 4U 1728-34, GX 3+1 and 4U 1820-30 and the Z-source GX 340+0 through all spectral states. However, we interpret the index reduction phase detected during the FB in Sco X-1 within the framework of a model in which the spectrum at the FB is determined by high radiation pressure from the NS surface.

Titarchuk, Lev; Seifina, Elena; Shrader, Chris

2014-07-01

114

Kilohertz-range harder pulsed x-ray generator utilizing a hot-cathode diode  

NASA Astrophysics Data System (ADS)

The constructions and the fundamental studies of two types of kilohertz-range harder pulsed x- ray generators are described. The multiple-pulse generator was primarily designed in order to increase the x-ray intensities even when the x-ray duration increased. In contrast, as the damped oscillation of the tube voltage was prevented by using two high-voltage diodes, we designed the single-pulse generator to obtain short x-ray durations. Each generator employed the following essential components: a thyratron pulser, a high-voltage double transformer, a storage battery for the hot cathode (filament), and an x-ray tube. The main condenser in the pulser was charged from 8 to 16 kV, and the electric charges in the condenser were repetitively discharged to the primary coils of the transformer. Because the high-voltage impulses from the secondary coils were then applied to the x-ray tube, repetitive x rays were generated. The x-ray tube was of a diode having a hot-cathode with a maximum temperature of about 2,000 K. The tube voltage increased in proportion to the charged voltage, and the maximum value was about 170 kV. The tube current was primarily determined by both the filament temperature and the tube voltage and had values of less than 1.5 A. The maximum intensities of the multiple and single types were about 48 and 16 nC/kg at 0.5 m per pulse. The x-ray pulse widths obtained by the single generator were less than 250 ns, and the maximum repetition rate was approximately 10 kHz.

Sato, Eiichi; Sagae, Michiaki; Oizumi, Teiji; Yamamoto, Mariko; Takabe, Akihito; Sakamaki, Kimio; Ojima, Hidenori; Takayama, Kazuyoshi; Tamakawa, Yoshiharu; Yanagisawa, Toru

1995-09-01

115

pyBLoCXS: Bayesian Low-Count X-ray Spectral analysis  

NASA Astrophysics Data System (ADS)

pyBLoCXS is a sophisticated Markov chain Monte Carlo (MCMC) based algorithm designed to carry out Bayesian Low-Count X-ray Spectral (BLoCXS) analysis in the Sherpa environment. The code is a Python extension to Sherpa that explores parameter space at a suspected minimum using a predefined Sherpa model to high-energy X-ray spectral data. pyBLoCXS includes a flexible definition of priors and allows for variations in the calibration information. It can be used to compute posterior predictive p-values for the likelihood ratio test. The pyBLoCXS code has been tested with a number of simple single-component spectral models; it should be used with great care in more complex settings.

Siemiginowska, Aneta; Kashyap, Vinay; Refsdal, Brian; van Dyk, David; Connors, Alanna; Park, Taeyoung

2012-04-01

116

Investigating the "missing baryon problem'' with XEUS: Mapping and spectral analysis of the Galactic soft X-ray emission  

NASA Astrophysics Data System (ADS)

The X-ray Evolving Universe Spectroscopy (XEUS) mission is primarily designed to study contents and structure of the primordial universe and thus to look back to redshifts of z ~ 10. To investigate this distant matter in the X-ray regime emission from the nearby universe has to be taken into account as a line-of-sight samples all emission and thus times from now until the early epochs. It is therefore necessary to have a handle on the thermal galactic emission components. Furthermore, higher energetic lines are redshifted into the ``galactic`` energy range and are thus blended. A successful XEUS mission therefore needs high spectral resolution at the low-energy band-pass. Cosmological simulations predict that about 30 - 40% of the baryonic matter in the Universe should be heated to temperatures of 105 - 107 K during structure formation to account for the discrepancy of baryons from observations between redshifts z=3 and z=0. Due to limiting sensitivity and spectral resolution of X-ray telescopes and detectors, no positive detections have been reported hitherto, and only crude upper limits for the contribution of a warm-hot intergalactic medium (WHIM) exist. The problem has been exacerbated due to recent deep pointed XMM-Newton and Chandra observations, in which more than 80 % of the diffuse soft X-ray background has been resolved into point sources (mainly AGN) between 0.5 - 2 keV. We show that the key to the determination of the WHIM contribution lies in the detailed mapping and spectral analysis of the galactic foreground and background emission. Our preliminary results from XMM-Newton EPIC shadowing experiments show that improved spectral resolution at the softest energies offers the unique possibility to disentangle diffuse emission components. Thus XEUS will be ideal for probing the diffuse galactic and intergalactic medium at increasing redshifts.

Freyberg, M. J.; Breitschwerdt, D.

117

THE SIMULTANEOUS OPTICAL-TO-X-RAY SPECTRAL ENERGY DISTRIBUTION OF SOFT X-RAY SELECTED ACTIVE GALACTIC NUCLEI OBSERVED BY SWIFT  

SciTech Connect

We report Swift observations of a sample of 92 bright soft X-ray selected active galactic nuclei (AGNs). This sample represents the largest number of AGNs observed to study the spectral energy distribution (SED) of AGNs with simultaneous optical/UV and X-ray data. The principal motivation of this study is to understand the SEDs of AGNs in the optical/UV to X-ray regime and to provide bolometric corrections which are important in determining the Eddington ratio L/L {sub Edd}. In particular, we rigorously explore the dependence of the UV-EUV contribution to the bolometric correction on the assumed EUV spectral shape. We find strong correlations of the spectral slopes {alpha}{sub X} and {alpha}{sub UV} with L/L {sub Edd}. Although narrow-line Seyfert 1 galaxies (NLS1s) have steeper {alpha}{sub X} and higher L/L {sub Edd} than broad-line Seyfert 1 galaxies (BLS1s), their optical/UV to X-ray spectral slopes {alpha}{sub ox} and optical/UV slopes {alpha}{sub UV} are very similar. The mean SED of NLS1s shows that in general this type of AGNs appears to be fainter in the UV and at hard X-ray energies than BLS1s. We find a strong correlation between {alpha}{sub X} and {alpha}{sub UV} for AGNs with X-ray spectral slopes {alpha}{sub X}<1.6. For AGNs with steeper X-ray spectra, both this relation and the relation between {alpha}{sub X} and L/L {sub Edd} break down. At {alpha}{sub X}{approx}1.6, L/L {sub Edd} reaches unity. We note an offset in the {alpha}{sub UV}-L/L {sub Edd} relation between NLS1s and BLS1s. We argue that {alpha}{sub UV} is a good estimator of L/L {sub Edd} and suggest that {alpha}{sub UV} can be used to estimate L/L {sub Edd} in high-redshift QSOs. Although NLS1s appear to be highly variable in X-rays, they only vary marginally in the UV.

Grupe, Dirk [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Komossa, Stefanie [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstr., D-85748 Garching (Germany); Leighly, Karen M. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States); Page, Kim L. [Department of Astronomy, University of Leicester, Leicester (United Kingdom)], E-mail: grupe@astro.psu.edu, E-mail: skomossa@mpe.mpg.de, E-mail: leighly@nhn.ou.edu

2010-03-01

118

Average spectral properties of galactic X-ray binaries with 3 years of MAXI data  

NASA Astrophysics Data System (ADS)

The energy spectra of X-ray binaries (XRBs) have been investigated during the last few decades with many observatories in different energy bands and with different energy resolutions. However, these studies are carried out in selected states of XRBs like during outbursts, transitions, quiescent states, and are always done in limited time windows of pointed observations. It is now possible to investigate the long term averaged spectra of a large number of X-ray binaries with the all sky monitor MAXI, which also has a broad energy band. Here we present the average spectral behaviour of a few representative XRBs. The long term averaged spectrum of Cyg X-1 is described by a sum of two power-laws having ?_{1} ˜2.8 and ?_{2} ˜1.2, along with a multi color disk blackbody having an inner disk temperature of 0.5 keV, GX 301-2 is described by a power-law with a high energy cut-off at E_{c} ˜ 15 keV and a blackbody component at 0.2 keV and that of Aql X-1 is described by a multi color disk blackbody at 2 keV and a power-law of ? ˜ 2.2. We have also constructed the combined X-ray spectrum of the X-ray binaries in the Milky Way, which can be compared to the XRBs spectra of other galaxies observed with Chandra and XMM-Newton. These measurements are also relevant to investigate the X-ray interaction with the ISM and its contribution to the ionizing X-ray background in the early universe.

Islam, Nazma; Mihara, T.; Sugizaki, M.; Paul, B.; Nath, Biman B.

119

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

120

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

121

X-Ray Spectral Characteristics of GINGA Gamma-Ray Bursts  

Microsoft Academic Search

We have investigated the spectral characteristics of a sample of bright gamma-ray bursts detected with the gamma-ray burst sensors aboard the satellite Ginga. This instrument employed a proportional and scintillation counter to provide sensitivity to photons in the 2-400 keV region and as such provided a unique opportunity to characterize the largely unexplored X-ray properties of gamma-ray bursts. The photon

T. E. Strohmayer; E. E. Fenimore; T. Murakami; A. Yoshida

1998-01-01

122

Spectral dependence of point defect production by x rays in RbBr  

SciTech Connect

{ital F}-center formation by monochromatic x rays has been studied above and below the bromine and rubidium {ital K}-absorption edges in crystals of RbBr. The x-ray beam from a double silicon crystal monochromator on an undulator at the Advanced Photon Source was used to produce these point defects, which were detected by a sensitive laser-induced luminescence method. Experiments were carried out over a wide range of monochromatic x-ray intensity, with emphasis on the nearly linear initial slope of defect formation with exposure. No significant increase in {ital F}-center formation efficiency was found upon crossing the bromine {ital K} edge, which indicates that additional Auger-cascade mechanisms do not appreciably add to the usual multiple ionization electron-hole recombination processes known to generate point defects. {copyright} {ital 1999} {ital The American Physical Society}

Brown, F.C. [Department of Physics, University of Washington, Box 351560, Seattle, Washington 98195 (United States)] [Department of Physics, University of Washington, Box 351560, Seattle, Washington 98195 (United States); Heald, S.M. [Pacific Northwest Laboratory, ANL-APS, Argonne, Illinois 60439 (United States)] [Pacific Northwest Laboratory, ANL-APS, Argonne, Illinois 60439 (United States); Jiang, D. [Department of Physics, Simon Fraser University, Burnaby, British Columbia (Canada)] [Department of Physics, Simon Fraser University, Burnaby, British Columbia (Canada); Brewe, D.L.; Kim, K.H.; Stern, E.A. [Department of Physics, University of Washington, Box 351560, Seattle, Washington 98195 (United States)] [Department of Physics, University of Washington, Box 351560, Seattle, Washington 98195 (United States)

1999-09-01

123

Intensity and spectral variability of strong galactic X-ray sources observed by ANS  

NASA Technical Reports Server (NTRS)

Hard X-ray observations by the ANS are used to analyze the energy spectrum and intensity fluctuations on time scales of seconds to days for 20 luminous galactic sources, of which 11 are galactic-bulge (GX) sources having no obvious identification with source categories. It is found that: (1) most GX sources are best fitted in the energy range from about 1 to 20 keV by exponential spectra with a source temperature (kT) of approximately 5 keV; (2) iron line emission around 6.7 keV is always detected as a persistent spectral feature of at least six and possibly seven of the sources studied; (3) most of the iron-line sources exhibit a direct correlation between kT and intensity (I) in the band from 1.4 to 7.2 keV; (4) no burst source counterparts or candidates show a direct correlation between kT and I, at least two show an inverse correlation, and no iron line emission is detected at a 3-sigma level from burster counterparts during burst-active states. A classification scheme for GX sources is proposed, and several observational tests for this scheme and for possible source models are described.

Parsignault, D. R.; Grindlay, J. E.

1978-01-01

124

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

125

Femtosecond X-Ray Free Electron Laser Pulse Duration Measurement from Spectral Correlation Function  

SciTech Connect

We present a novel method for measuring the duration of femtosecond x-ray pulses from self-amplified spontaneous emission free electron lasers by performing statistical analysis in the spectral domain. Analytical expressions of the spectral correlation function were derived in the linear regime to extract both the pulse duration and the spectrometer resolution. Numerical simulations confirmed that the method can be also used in the nonlinear regime. The method was demonstrated experimentally at the Linac Coherent Light Source by measuring pulse durations down to 13 fs FWHM.

Lutman, A. A

2012-04-17

126

Spectral and timing properties of the accreting X-ray millisecond pulsar IGR J17498-2921  

NASA Astrophysics Data System (ADS)

Context. IGR J17498-2921 is the third X-ray transient accreting millisecond pulsar discovered by INTEGRAL. It was in outburst for about 40 days beginning on August 08, 2011. Aims: We analyze the spectral and timing properties of the object and the characteristics of X-ray bursts to constrain the physical processes responsible for the X-ray production in this class of sources. Methods: We studied the broad-band spectrum of the persistent emission in the 0.6-300 keV energy band using simultaneous INTEGRAL, RXTE, and Swift data obtained in August-September 2011. We also describe the timing properties in the 2-100 keV energy range such as the outburst lightcurve, pulse profile, pulsed fraction, pulsed emission, time lags, and study the properties of X-ray bursts discovered by RXTE, Swift, and INTEGRAL and the recurrence time. Results: The broad-band average spectrum is well-described by thermal Comptonization with an electron temperature of kTe ~ 50 keV, soft seed photons of kTbb ~ 1 keV, and Thomson optical depth ?T ~ 1 in a slab geometry. The slab area corresponds to a black body radius of Rbb ~ 9 km. During the outburst, the spectrum stays remarkably stable with plasma and soft seed photon temperatures and scattering optical depth that are constant within the errors. This behavior has been interpreted as indicating that the X-ray emission originates above the neutron star (NS) surface in a hot slab (either the heated NS surface or the accretion shock). The INTEGRAL, RXTE, and Swift data reveal the X-ray pulsation at a period of 2.5 ms up to ~65 keV. The pulsed fraction is consistent with being constant, i.e. energy independent and has a typical value of 6-7%. The nearly sinusoidal pulses show soft lags that seem to saturate near 10 keV at a rather small value of ~-60 ?s with those observed in other accreting pulsars. The short burst profiles indicate that there is a hydrogen-poor material at ignition, which suggests either that the accreted material is hydrogen-deficient, or that the CNO metallicity is up to a factor of about two times solar. However, the variation in the burst recurrence time as a function of ? (inferred from the X-ray flux) is much smaller than predicted by helium-ignition models.

Falanga, M.; Kuiper, L.; Poutanen, J.; Galloway, D. K.; Bozzo, E.; Goldwurm, A.; Hermsen, W.; Stella, L.

2012-09-01

127

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

128

Dramatic X-Ray Spectral Variability of the Broad Absorption Line Quasar PG 2112+059  

NASA Astrophysics Data System (ADS)

With a 1999 ASCA observation, PG 2112+059 became notable as the first broad absorption line (BAL) quasar found to exhibit a typical radio-quiet quasar X-ray continuum underlying a large amount of intrinsic absorption. We present a recent Chandra ACIS-S3 observation of PG 2112+059 that demonstrates remarkable spectral and luminosity variability since that time. In addition to a decrease in the continuum normalization by a factor of ~3.5, the absorption column density has apparently increased substantially, and a strong feature in the Fe K? region has appeared. Concurrent Hubble Space Telescope (HST) STIS data compared with archival HST data from earlier epochs show evidence for variability of the continuum (up to a factor of ~1.7 in the ultraviolet), and in some absorption features of the C IV ?1549 BAL since 1992; however, the O VI BAL structure is consistent with a 1995 observation. We also present evidence for Ly?-O VI ?1037.62 and Ly?-N V ?1242.80 line-locked absorption systems, supporting the assumption that ultraviolet line pressure is driving the BAL outflow. Whereas ultraviolet BALs typically exhibit only modest equivalent width variability over timescales of years, the dramatic X-ray variability of PG 2112+059 suggests that X-ray spectral variability studies of BAL quasars have great potential for probing the physics of quasar winds.

Gallagher, S. C.; Brandt, W. N.; Wills, Beverley J.; Charlton, J. C.; Chartas, G.; Laor, A.

2004-03-01

129

New X-ray spectral observations of NGC 4151 with ASCA  

NASA Technical Reports Server (NTRS)

We present new X-ray spectral data for the well-studied Seyfert galaxy NGC 4151, which was observed twice for about 20 ks each during the ASCA performance verification phase, once on 1993 May 25 and again on 1993 November 5. The source underwent complex spectral variability, and the observed 2-10 keV flux increased by a factor of 2 while the intrinsic 2-10 keV flux increased by no more than 20%. The data can be modeled with either a dual cold absorber plus a soft X-ray excess consisting of scattered continuum flux and an additional 'ultrasoft' X-ray excess component, or a warm absorber plus scattered continuum flux. There is evidence for variability at less than 1 keV energies that is unrelated to the 2-10 keV continuum. For an ionized-absorber description of NGC 4151, changes in the ionization state of the absorber appear to be unrelated to changes in the ionizing continuum.

Weaver, K. A.; Yaqoob, T.; Holt, S. S.; Mushotzky, R. F.; Matsuoka, M.; Yamauchi, M.

1994-01-01

130

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

131

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

132

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  

NASA Astrophysics Data System (ADS)

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 close to the facility. A new x-ray facility is currently available to perform these absolute x-ray calibrations. This paper presents the x-ray tube based high energy x-ray source delivering x-ray energies ranging from 0.9 to 10 keV by means of an anode barrel. The purpose of this source is mainly to calibrate LIL x-ray cameras but it can also be used to measure x-ray filter transmission of plasma diagnostics. Different x-ray absolute calibrations such as x-ray streak and framing camera yields, x-ray charge-coupled device quantum efficiencies, and x-ray filter transmissions are presented in this paper. A x-ray flat photocathode detector sensitivity calibration recently performed for a CEA Z-pinch facility is also presented.

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

2010-05-01

133

Doping evolution of Zhang-Rice singlet spectral weight: A comprehensive examination by x-ray absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The total spectral weight S of the emergent low-energy quasiparticles in high-temperature superconductors (HTSCs) is explored by x-ray absorption spectroscopy. In order to examine the applicability of the Hubbard model, regimes that cover from zero doping to overdoping are investigated. In contrast to results of mean-field theory, we found that S deviates from linear dependence on the doping level p. The slope of S versus p changes continuously throughout the whole doping range with no sign of saturation up to p=0.23. Therefore, the picture of the Zhang-Rice singlet remains intact within the most prominent doping regimes of HTSCs.

Chen, Y.-J.; Jiang, M. G.; Luo, C. W.; Lin, J.-Y.; Wu, K. H.; Lee, J. M.; Chen, J. M.; Kuo, Y. K.; Juang, J. Y.; Mou, Chung-Yu

2013-10-01

134

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.

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

2011-01-01

135

Spectral Modeling of the Comptonized Continua of Accreting X-Ray Pulsars: Recent Progress  

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 Her X-1, Cen X-3, and LMC X-4. These accreting pulsars typically have X-ray spectra consisting of broad Comptonized cutoff power-laws. Current theory suggests these X-ray spectra result from the impact of the high-velocity magnetically channeled plasma accretion flows onto the surfaces of the neutron stars. The flows have such high energy density that shocks developing in the plasmas can be radiation-dominated. These X-ray pulsars often, but not always, show cyclotron resonant scattering features implying neutron star surface magnetic field strengths above 10^12 G. Over the past few years a number of studies have reported both positive and negative correlations of the cyclotron line energy centroids with X-ray luminosity in a number of pulsars. However, the detailed analysis of the cyclotron line centroids suffers from the lack of a robust model for the Comptonized X-ray continuum upon which the cyclotron lines are superposed. We discuss in this presentation our progress in developing tools for the analysis of the X-ray spectra formed in these systems. The range of parameter conditions presented by the many known real accreting pulsar systems substantially exceeds that of the limited set of pulsars on which the original analytic model of Becker and Wolff (2007) was validated. In the high temperature optically thick plasmas, 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 local photon population in the shock structure. We discuss our strategy for numerically accounting for the relative contribution to the full X-ray spectrum made by each of these physical processes. Solving for the integrated spectrum involves numerical integrations of complicated analytic series that presents different challenges in each of the three cases of cyclotron, black body, and bremsstrahlung emission. We discuss the issues involved for each physical process.

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

2014-01-01

136

Hercules X-1: Spectral Variability of an X-Ray Pulsar in a Stellar Binary System. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

A cosmic X-ray spectroscopy experiment onboard the Orbiting Solar Observatory 8 (OSO-8), observed Her x-1 continuously for approximately 8 days. Spectral-temporal correlations of the X-ray emission were obtained. The major results concern observations of: (1) iron band emission, (2) spectral hardening (increase in effective x-ray temperature) within the X-ray pulse, and (3) a transition from an X-ray low state to a high state. The spectrum obtained prior to the high state can be interpreted as reflected emission from a hot coronal gas surrounding an accretion disk, which itself shields the primary X-ray source from the line of sight during the low state. The spectral hardening within the X-ray pulse was indicative of the beaming mechanism at the neutron star surface. The hardest spectrum by pulse phase was identified with the line of sight close to the Her x-1 magnetic dipole axis, and the X-ray pencil beam become harder with decreasing angle between the line of sight and the dipole axis.

Pravdo, S. H.

1976-01-01

137

X-Ray Attenuation of Silicon in the Energy Range 25 - 50 KeV.  

National Technical Information Service (NTIS)

Precise measurements of the X-ray attenuation coefficient of crystalline silicon have been made in the energy range 25 to 50 keV. A systematic discrepancy between theory and experiment is observed. The most likely cause of the disagreement is thought to b...

J. F. Mika Z. Barnea

1984-01-01

138

Short Range Order in some Polymer Melts from x ray Diffraction  

Microsoft Academic Search

Wide angle x ray diffraction measurements were performed on a series of polymer melts, to study the dependence of the short range structure of polymer liquids on chain architecture. These results are useful in testing single chain models of vinyl polymers, which in turn are needed to validate integral equation theories of polymer melts and blends. The polymers studied were

A. Habenschuss; J. D. Londono; J. J. Rajasekaran; J. G. Curro; J. D. Honeycutt

1996-01-01

139

Ultraluminous X-ray sources: a deeper insight into their spectral evolution  

NASA Astrophysics Data System (ADS)

We select a sample of nearby ultraluminous X-ray sources with long XMM-Newton observations and analyse all the available XMM-Newton data using both X-ray spectral fitting techniques and hardness-intensity diagrams. The sample includes IC 342 X-1, NGC 5204 X-1, NGC 5408 X-1, Holmberg IX X-1, Holmberg II X-1, NGC 1313 X-1, NGC 1313 X-2 and NGC 253 X-1. We found that, although a common reference model can be used to describe the X-ray spectra, the sources show different spectral evolutions, phenomenologically described in terms of variations in the properties of a soft component and a high-energy tail. Variations at low energies are accounted for (mostly) by changes in the normalization of the soft component and/or in the column density to the source, while variations in the high-energy tail by changes in the parameters of an optically thick corona. This spectral variability is rather well characterized on a colour-colour and hardness-intensity diagram in terms of suitably defined hardness ratios. We suggest the existence of a variability pattern on the hardness-intensity diagram and we interpret it in terms of the switch between a near-Eddington and a super-Eddington accretion regime. The transition between the two regimes seems to be driven mostly by changes in the contribution of the soft component, which can be explained in terms of the increasing importance of wind emission. The analysis is complemented by an investigation of the short-term time variability of all the sources. In general, no clear correlation between the spectral and temporal properties is found.

Pintore, Fabio; Zampieri, Luca; Wolter, Anna; Belloni, Tomaso

2014-04-01

140

Maximizing spectral flux from self-seeding hard x-ray free electron lasers  

NASA Astrophysics Data System (ADS)

Fully coherent x rays can be generated by self-seeding x-ray free electron lasers (XFELs). Self-seeding by a forward Bragg diffraction (FBD) monochromator has been recently proposed [G. Geloni, V. Kocharyan, and E. Saldin, J. Mod. Opt. 58, 1391 (2011)JMOPEW0950-034010.1080/09500340.2011.586473] and demonstrated [J. Amann , Nat. Photonics 6, 693 (2012)NPAHBY1749-488510.1038/nphoton.2012.180]. Characteristic time T0 of FBD determines the power, spectral, and time characteristics of the FBD seed [Yu. Shvyd’ko and R. Lindberg, Phys. Rev. ST Accel. Beams 15, 100702 (2012)PRABFM1098-440210.1103/PhysRevSTAB.15.100702]. Here we show that for a given electron bunch with duration ?e the spectral flux of the self-seeding XFEL can be maximized, and the spectral bandwidth can be respectively minimized by choosing T0˜?e/? and by optimizing the electron bunch delay ?e. The choices of T0 and ?e are not unique. In all cases, the maximum value of the spectral flux and the minimum bandwidth are primarily determined by ?e. Two-color seeding takes place if T0??e/?. The studies are performed, for a Gaussian electron bunch distribution with the parameters, close to those used in the short-bunch (?e?5fs) and long-bunch (?e?20fs) operation modes of the Linac Coherent Light Source XFEL.

Yang, Xi; Shvyd'ko, Yuri

2013-12-01

141

Rapid spectral and flux time variations in a solar burst observed at various dm-mm wavelengths and at hard X-rays  

NASA Technical Reports Server (NTRS)

A solar burst was observed with high sensitivity and time resolution at cm-mm wavelengths by two different radio observatories (Itapetinga and Algonquin), with high spectral time resolution at dm-mm wavelengths by patrol instruments (Sagamore Hill), and at hard X-rays (HXM Hinotori). At the onset of the major burst time structure there was a rapid rise in the spectral turnover frequency (from 5 to 15 GHz), in about 10s, coincident to a reduction of the spectral index in the optically thin part of the spectrum. The burst maxima were not time coincident at the optically thin radio frequencies and at the different hard X-ray energy ranges. The profiles at higher radio frequencies exhibited better time coincidence to the high energy X-rays. The hardest X-ray spectrum (-3) coincided with peak radio emission at the higher frequency (44 GHz). The event appeared to be built up by a first major injection of softer particles followed by other injections of harder particles. Ultrafast time structures were identified as superimposed on the burst emission at the cm-mm high sensitivity data at X-rays, with predominant repetition rates ranging from 2.0 to 3.5 Hz.

Zodivaz, A. M.; Kaufmann, P.; Correia, E.; Costa, J. E. R.; Takakura, T.; Cliver, E. W.; Tapping, K. F.

1986-01-01

142

X-Ray Spectral Cutoff and the Lack of Hard X-Ray Emission from Two Ultraluminous X-Ray Sources M81 X-6 and Holmberg IX X-1  

NASA Astrophysics Data System (ADS)

We present broadband X-ray spectral study of two ultraluminous X-ray sources (ULXs), M81 X-6 and Holmberg IX X-1, based on Suzaku and XMM-Newton observations. We perform joint broadband spectral analysis of the brightest sources in the field, i.e., the two ULXs and the active galactic nucleus (AGN) in M81, and demonstrate that the X-ray spectra of the ULXs cut off at energies >~ 3 keV with negligible contribution at high energies in the Suzaku HXD/PIN band. The 90% upper limit on the 10-30 keV band luminosity of an underlying broadband power-law component is 3.5 × 1038 erg s-1 for M81 X-6 and 1.2 × 1039 erg s-1 for Holmberg IX X-1. These limits are more than an order of magnitude lower than the bolometric (0.1-30 keV) luminosity of 6.8 × 1039 erg s-1 for M81 X-6 and 1.9 × 1040 erg s-1 for Holmberg IX X-1. Our results confirm earlier indications of spectral cutoffs inferred from the XMM-Newton observations of bright ULXs and show that there is not an additional high-energy power-law component contributing significantly to the X-ray emission. The spectral form of the two ULXs are very different from those of Galactic black hole X-ray binaries (BHBs) or AGNs. This implies that the ULXs are neither simply scaled-up versions of stellar-mass BHBs nor scaled-down versions of AGNs.

Dewangan, G. C.; Jithesh, V.; Misra, R.; Ravikumar, C. D.

2013-07-01

143

Multicolor operation and spectral control in a gain-modulated x-ray free-electron laser.  

PubMed

We show that the spectral properties of a self-amplified spontaneous emission x-ray free-electron laser can be controlled by modulating the gain in magnetic undulators, thus producing one or several spectral lines within a single few femtosecond pulse. By varying the magnetic field along the undulator and the electron beam transport line, the system we demonstrate can tailor the x-ray spectrum to optimally meet numerous experimental requirements for multicolor operation. PMID:24116783

Marinelli, A; Lutman, A A; Wu, J; Ding, Y; Krzywinski, J; Nuhn, H-D; Feng, Y; Coffee, R N; Pellegrini, C

2013-09-27

144

New consistency tests for high-accuracy measurements of X-ray mass attenuation coefficients by the X-ray extended-range technique.  

PubMed

An extension of the X-ray extended-range technique is described for measuring X-ray mass attenuation coefficients by introducing absolute measurement of a number of foils - the multiple independent foil technique. Illustrating the technique with the results of measurements for gold in the 38-50 keV energy range, it is shown that its use enables selection of the most uniform and well defined of available foils, leading to more accurate measurements; it allows one to test the consistency of independently measured absolute values of the mass attenuation coefficient with those obtained by the thickness transfer method; and it tests the linearity of the response of the counter and counting chain throughout the range of X-ray intensities encountered in a given experiment. In light of the results for gold, the strategy to be ideally employed in measuring absolute X-ray mass attenuation coefficients, X-ray absorption fine structure and related quantities is discussed. PMID:22338654

Chantler, C T; Islam, M T; Rae, N A; Tran, C Q; Glover, J L; Barnea, Z

2012-03-01

145

Challenges to quantitative multivariate statistical analysis of atomic-resolution X-ray spectral.  

PubMed

A new aberration-corrected scanning transmission electron microscope equipped with an array of Si-drift energy-dispersive X-ray spectrometers has been utilized to acquire spectral image data at atomic resolution. The resulting noisy data were subjected to multivariate statistical analysis to noise filter, remove an unwanted and partially overlapping non-sample-specific X-ray signal, and extract the relevant correlated X-ray signals (e.g., channels with L and K lines). As an example, the Y?Ti?O? pyrochlore-structured oxide (assumed here to be ideal) was interrogated at the [011] projection. In addition to pure columns of Y and Ti, at this projection, there are also mixed 50-50 at. % Y-Ti columns. An attempt at atomic-resolution quantification is presented. The method proposed here is to subtract the non-column-specific signal from the elemental components and then quantify the data based upon an internally derived k-factor. However, a theoretical basis to predict this non-column-specific signal is needed to make this generally applicable. PMID:22849798

Kotula, Paul G; Klenov, Dmitri O; von Harrach, H Sebastian

2012-08-01

146

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

NASA Astrophysics Data System (ADS)

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 × 10^23 cm-3, Te ˜ 10 eV, and Z ˜ 1. Just prior to shock breakout, the uniformly compressed region of the target was irradiated with 9-keV, He_? emission from a Zn backlighter. The x rays scattered at either 90^rc or 120^rc were dispersed with a Bragg crystal and recorded with an x-ray framing camera. The plasma conditions inferred from the spectral line shapes of the elastic and inelastic components will be compared with the LILAC predictions. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

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

2004-11-01

147

Crosscheck of different techniques for two dimensional power spectral density measurements of x-ray optics  

SciTech Connect

The consistency of different instruments and methods for measuring two-dimensional (2D) power spectral density (PSD) distributions are investigated. The instruments are an interferometric microscope, an atomic force microscope (AFM) and the X-ray Reflectivity and Scattering experimental facility, all available at Lawrence Berkeley National Laboratory. The measurements were performed with a gold-coated mirror with a highly polished stainless steel substrate. It was shown that these three techniques provide essentially consistent results. For the stainless steel mirror, an envelope over all measured PSD distributions can be described with an inverse power-law PSD function. It is also shown that the measurements can be corrected for the specific spatial frequency dependent systematic errors of the instruments. The AFM and the X-ray scattering measurements were used to determine the modulation transfer function of the interferometric microscope. The corresponding correction procedure is discussed in detail. Lower frequency investigation of the 2D PSD distribution was also performed with a long trace profiler and a ZYGO GPI interferometer. These measurements are in some contradiction, suggesting that the reliability of the measurements has to be confirmed with additional investigation. Based on the crosscheck of the performance of all used methods, we discuss the ways for improving the 2D PSD characterization of X-ray optics.

Yashchuk, Valeriy V.; Irick, Steve C.; Gullikson, Eric M.; Howells, Malcolm R.; MacDowell, Alastair A.; McKinney, Wayne R.; Salmassi, Farhad; Warwick, Tony

2005-07-12

148

An X-Ray Spectral Model for Clumpy Tori in Active Galactic Nuclei  

NASA Astrophysics Data System (ADS)

We construct an X-ray spectral model for the clumpy torus in an active galactic nucleus (AGN) using Geant4, which includes the physical processes of the photoelectric effect, Compton scattering, Rayleigh scattering, ? conversion, fluorescence line, and Auger process. Since the electrons in the torus are expected to be bounded instead of free, the deviation of the scattering cross section from the Klein-Nishina cross section has also been included, which changes the X-ray spectra by up to 25% below 10 keV. We have investigated the effect of the clumpiness parameters on the reflection spectra and the strength of the fluorescent line Fe K?. The volume filling factor of the clouds in the clumpy torus only slightly influences the reflection spectra, however, the total column density and the number of clouds along the line of sight significantly change the shapes and amplitudes of the reflection spectra. The effect of column density is similar to the case of a smooth torus, while a small number of clouds along the line of sight will smooth out the anisotropy of the reflection spectra and the fluorescent line Fe K?. The smoothing effect is mild in the low column density case (N H = 1023 cm-2), whereas it is much more evident in the high column density case (N H = 1025 cm-2). Our model provides a quantitative tool for the spectral analysis of the clumpy torus. We suggest that the joint fits of the broad band spectral energy distributions of AGNs (from X-ray to infrared) should better constrain the structure of the torus.

Liu, Yuan; Li, Xiaobo

2014-05-01

149

The X-ray spectrum and spectral energy distribution of FIRST J155633.8+351758: a LoBAL quasar with a probable polar outflow  

NASA Astrophysics Data System (ADS)

We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD Imaging Spectrometer S-array (ACIS-S) observation of the reddened, radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We investigated a number of models of varied sophistication to fit the 531-photon spectrum. These models ranged from simple power laws to power laws absorbed by hydrogen gas in differing ionization states and degrees of partial covering. Preferred fits indicate that the intrinsic X-ray flux is consistent with that expected for quasars of similarly high luminosity, i.e. an intrinsic, dereddened and unabsorbed optical to X-ray spectral index of -1.7. We cannot tightly constrain the intrinsic X-ray power-law slope, but find indications that it is flat (photon index ? = 1.7 or flatter at a >99 per cent confidence for a neutral hydrogen absorber model). Absorption is present, with a column density a few times 1023 cm-2, with both partially ionized models and partially covering neutral hydrogen models providing good fits. We present several lines of argument that suggest the fraction of X-ray emissions associated with the radio jet is not large. We combine our Chandra data with observations from the literature to construct the spectral energy distribution of FIRST J1556+3517 from radio to X-ray energies. We make corrections for Doppler beaming for the pole-on radio jet, optical dust reddening and X-ray absorption, in order to recover a probable intrinsic spectrum. The quasar FIRST J1556+3517 seems to be an intrinsically normal radio-quiet quasar with a reddened optical/UV spectrum, a Doppler-boosted but intrinsically weak radio jet and an X-ray absorber not dissimilar from that of other broad absorption line quasars.

Berrington, Robert C.; Brotherton, Michael S.; Gallagher, Sarah C.; Ganguly, Rajib; Shang, Zhaohui; DiPompeo, Michael; Chatterjee, Ritaban; Lacy, Mark; Gregg, Michael D.; Hall, Patrick B.; Laurent-Muehleisen, S. A.

2013-12-01

150

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

151

NLTE Spectral Analysis of Accretion Discs in Ultracompact X-ray Binaries  

NASA Astrophysics Data System (ADS)

We present first results of a NLTE spectral analysis of the accretion discs in the ultracompact X-ray binaries 4U 0614+091 and 4U 1626-67, performed with our accretion disc code AcDc. We show, that it is possible to give an upper limit for the abundances of hydrogen. The emission line features seen in the spectrum of 4U 1626-67 can be modeled qualitatively with irradiation of the accretion disc by the central neutron star.

Nagel, T.; Hammer, N. J.; Rauch, T.; Werner, K.; Dreizler, S.

2005-08-01

152

A survey of the industrial use of x-ray spectral analysis for steels  

SciTech Connect

The authors describe a method of x-ray spectral analysis for steels during startup operations. It has been possible to do this because of advances in methods in the construction of theoretical correlation equations applicable for determining elements and total composition on any grade of steel. A model is used to determine the coefficients in the correlation equation. The calibration-specimen compositions (%) are presented for C, Si, P, S, Ti, V, Cr, Mn, Fe, Ni, Cu, W, and Mo. Calibrations are also performed for cobalt and tungsten in high-speed steels.

Kalinin, B.D.

1986-08-01

153

Characterization of Medium-Range Order in Noncrystalline Systems by Fluctuation X-ray Microscopy  

SciTech Connect

In recent years, materials research has increasingly focused on developing a better understanding of the disordered state of matter. Much of our understanding amorphous materials has depended upon the atomic pair distribution function (PDF) obtained from diffraction experiments. However, the PDF method has poor sensitivity to medium-range order (MRO), the characterization of which is a long standing problem. Recently, fluctuation electron microscopy (FEM) was developed and successfully used for probing MRO in amorphous materials. This technique gains its sensitivity to MRO by examining fluctuations in coherently scattered (speckle) intensity patterns from very small sample volumes, on a length scale determined by the illuminated radius or associated imaging resolution. The speckle variance depends on two-, three- and four-body atomic correlation functions, whereas the average, which is just the diffracted intensity, depends only on the two-body PDF. Higher order correlation functions are more sensitive to MRO. In the x-ray regime, many techniques exist to probe long- and short-range order in matter, in real space by imaging and in reciprocal space by diffraction and scattering. The average intensity obtained from scattering and diffraction experiments is routinely inverted to give the atomic PDF. At present, no x-ray technique effectively probes MRO. By comparison to electrons, x-rays provide access to longer length scales due to their longer wavelengths and offer greater sample penetration with less radiation damage, as well as elemental and chemical sensitivity through resonant effects. Consequently, we are developing fluctuation x-ray microscopy (FXM) at the 2-ID-B soft x-ray beamline to study MRO in bulk samples, solutions and films at nanometer and larger length scales. Compared to FEM, FXM is better suited to materials with larger characteristic length scales such as polymers, biological macromolecules and their complexes, as well as other nanostructured materials, nanocomposites and hybrids.

Paterson, D.; Fan, L.; McNulty, I.; Gibson, J.M.; Treacy, M.M.M.J. (AZU)

2007-05-24

154

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

155

The Far-Infrared Spectral Energy Distributions of X-ray Selected Active Galaxies  

NASA Technical Reports Server (NTRS)

This paper reports the ISO results on hard X-ray selected AGN which are less biased against red/obscured objects than other selection wavebands. We find that, as predicted, the IR continuum of these sources extends to redder sources than in optically/radio selected sample. This indicates that the latter samples miss a portion of the population which is fainter in the optical but can be easily picked up in the hard X-ray. The range of IR SEDs is roughly consistent with reddening of the IR continuum up to column densities of around 10(exp 23)/cu cm. Modeling of the full SED using dusty disk models demonstrated that varying the viewing angle can explain the observed SEDs, though rather large disks are required to fit the cooler, long wavelength emission. From the fits we can obtain estimates of the mass and inclination of the system.

Kuraszkiewicz, J. K.; Wilkes, B. J.; Hooper, E. J.

2003-01-01

156

Spectral sensitivity calibration of Au and CsI photocathodes of high speed x-ray scanning camera  

NASA Astrophysics Data System (ADS)

High speed X-ray scanning camera (XSC) is an extra precision temporal and spatial diagnostic instrument in the inertial confinement fusion (ICF) experiment. In order to quantitatively analyze the measurement results, the spectral sensitivity of XSC, which depends on the response of the transmission photocathode, is necessary to be absolutely calibrated. A method of measuring the spectral response of Au and CsI transmission photocathodes of XSC is described. Based on Beijing Synchrotron Radiation Facility (BSRF), Au and CsI transmission photocathodes with slits are calibrated in the photon energy range of 60 eV-1500 eV and 2.1 keV-5.5 keV. Utilizing the quantum efficiency of the standard detector AXUV-100, the calibrated quantum efficiency of Au and CsI photocathodes are derived. The calibration data agree well with the photoelectric emission theory of Henke.

Yuan, Zheng; Zeng, Peng; Deng, Bo; Chen, Tao; Cao, Zhurong; Liu, Shenye; Yuan, Yongteng

2012-10-01

157

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

158

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

159

Probing chemistry within the membrane structure of wood with soft X-ray spectral microscopy  

NASA Astrophysics Data System (ADS)

Scanning Transmission Soft X-ray spectral microscopy on Carbon's 1s absorption edge reveals the distribution of structural biopolymers within cell membrane regions of modern cedar and oak. Cellulose is extremely susceptible to beam damage. Spectroscopic studies of beam damage reveals that the chemical changes resulting from secondary electron impact may be highly selective and is consistent with hydroxyl eliminations and structural rearrangement of pyranose rings in alpha-cellulose to hydroxyl substituted ? pyrones. A study of acetylated cellulose demonstrates significantly different chemistry; principally massive decarboxylation. Defocusing the beam to a 2 ?m spot size allows for the acquisition of ``pristine'' cellulose spectra. Spectral deconvolution is used to assess the distribution of lignin and cellulose in the different regions of the cell membrane. Using the intensity of the hydroxylated aromatic carbons 1s-?* transition, the ratio of coniferyl and syringyl based lignin within the middle lamellae and secondary cell wall of oak, an angiosperm can be determined. .

Cody, George D.

2000-05-01

160

Determination of electron energy, spectral width, and beam divergence at the exit window for clinical megavoltage x-ray beams  

PubMed Central

Monte Carlo simulations of x-ray beams typically take parameters of the electron beam in the accelerating waveguide to be free parameters. In this paper, a methodology is proposed and implemented to determine the energy, spectral width, and beam divergence of the electron source. All treatment head components were removed from the beam path, leaving only the exit window. With the x-ray target and flattener out of the beam, uncertainties in physical characteristics and relative position of the target and flattening filter, and in spot size, did not contribute to uncertainty in the energy. Beam current was lowered to reduce recombination effects. The measured dose distributions were compared with Monte Carlo simulation of the electron beam through the treatment head to extract the electron source characteristics. For the nominal 6 and 18 MV x-ray beams, the energies were 6.51±0.15 and 13.9±0.2 MeV, respectively, with the uncertainties resulting from uncertainties in the detector position in the measurement and in the stopping power in the simulations. Gaussian spectral distributions were used, with full widths at half maximum ranging from 20±4% at 6 MV to 13±4% at 18 MV required to match the fall-off portion of the percent-depth ionization curve. Profiles at the depth of maximum dose from simulations that used the manufacturer-specified exit window geometry and no beam divergence were 2–3 cm narrower than measured profiles. Two simulation configurations yielding the measured profile width were the manufacturer-specified exit window thickness with electron source divergences of 3.3° at 6 MV and 1.8° at 18 MV and an exit window 40% thicker than the manufacturer’s specification with no beam divergence. With the x-ray target in place (and no flattener), comparison of measured to simulated profiles sets upper limits on the electron source divergences of 0.2° at 6 MV and 0.1° at 18 MV. A method of determining source characteristics without mechanical modification of the treatment head, and therefore feasible in clinics, is presented. The energies and spectral widths determined using this method agree with those determined with only the exit window in the beam path.

Sawkey, D. L.; Faddegon, B. A.

2009-01-01

161

Sample holder assembly covering a wide range of temperatures for surface X-ray diffraction  

Microsoft Academic Search

We describe a sample holder assembly which can control a sample temperature in a wide range. The assembly is attached to a six-circle surface X-ray diffractometer with an ultrahigh-vacuum chamber. Samples up to 16.5 mm square can be held at constant temperatures between 50 and 1350 K with a tantalum heater on a pyrolytic boron nitride plate and a closed-cycle

H. Tajiri; K. Sumitani; S. Nakatani; T. Takahashi; K. Akimoto; H. Sugiyama; X. Zhang; H. Kawata

2004-01-01

162

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

163

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

164

Monochromatic X-Ray Sampling Imager for Laser-Imploded Core Plasma Observation with Highly Spatial, Temporal, and Spectral Resolutions  

Microsoft Academic Search

A novel x-ray imaging method, providing spatial resolution of 10 mum, temporal resolution 10 ps, and spectral resolution of E\\/DeltaE = 200 (E: photon energy), is suggested to diagnose laser driven fusion plasma. This scheme consists of a monochromatic x-ray imager with the use of two-dimensional (2D) curved crystals and an imagesampling streak camera. Feasibility of the method was studied

Minoru Tanabe; Hiroaki Nishimura; Shinsuke Fujioka; Hiroki Ishimaru; Yuichi Inubushi; Keiji Nagai; Hiroyuki Shiraga; Takayoshi Norimatsu; Hiroshi Azechi; Kunioki Mima

2008-01-01

165

Development of high spectral resolution CdZnTe pixel detectors for astronomical hard X-ray telescopes  

Microsoft Academic Search

Cadmium zinc telluride detectors (CdZnTe) offer the possibility of achieving excellent spectral and spatial resolution for compact hard X-ray sensors operated without cryogenics. These characteristics make these detectors ideal for several astrophysical applications, including focal plane sensors for multilayer hard X-ray telescopes, and in the image plane of coded-aperture imagers. We are developing a CdZnTe pixel detector and low-noise VLSI

A. E. Bolotnikov; W. R. Cook; S. E. Boggs; F. A. Harrison; S. M. Schindler

2001-01-01

166

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

167

An XMM search for quiescient low-mass X-ray binaries in globular cluster using X-ray spectral identification  

NASA Astrophysics Data System (ADS)

Low-mass X-ray binaries (LMXBs) are now routinely used for neutron star (NS) radius measurements. Observations of these systems in their quiescent stage (qLMXB) is one method leading to precise measurements. However, the dominant source of uncertainty on the NS radii remains the distance to the binary systems. Globular clusters (GCs) are therefore the places to look for more qLMXBs, due to their known or measurable distances and their abundance of binary systems. This thesis reports the discovery of seven candidate qLMXBs in six GCs, using observations from the XMM-Newton satellite, based on X-ray spectral consistency with NS hydrogen atmosphere models. The goal of this program of observations is to increase the population of known GC qLMXBs, for which longer follow-up exposures will permit high precision radius measurements. Nine candidates were initially identified based on their X-ray spectra with signal-to-noise ratio S/N > 3. Two candidates in NGC 6304 were tentatively confirmed, with consistent best-fit parameters, in a follow-up Chandra observation. One low-S/N candidate in NGC 6540 ( S/N = 7) was subsequently excluded by a deeper, higher S/N ( S/N = 17) observation. One other candidate was also excluded on the basis of the spatial velocity of the associated companion star, precluding cluster membership. Thus, the present work has added seven new qLMXB candidates to the eleven previously known.

Guillot, Sebastien

168

Spectral Softening in the X-Ray Afterglow of GRB 130925A as Predicted by the Dust Scattering Model  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts (GRBs) usually occur in a dense star-forming region with a massive circumburst medium. The small-angle scattering of intense prompt X-ray emission off the surrounding dust grains will have observable consequences and sometimes can dominate the X-ray afterglow. In most of the previous studies, only the Rayleigh-Gans (RG) approximation is employed for describing the scattering process, which works accurately for the typical size of grains (with radius of a <= 0.1 ?m) in the diffuse interstellar medium. When the size of the grains may significantly increase, as in a more dense region where GRBs would occur, the RG approximation may not be valid enough for modeling detailed observational data. In order to study the temporal and spectral properties of the scattered X-ray emission more accurately with potentially larger dust grains, we provide a practical approach using the series expansions of anomalous diffraction (AD) approximation based on the complicated Mie theory. We apply our calculations to understand the puzzling X-ray afterglow of recently observed GRB 130925A that showed a significant spectral softening. We find that the X-ray scattering scenarios with either AD or RG approximation adopted could well reproduce both the temporal and spectral profile simultaneously. Given the plateau present in the early X-ray light curve, a typical distribution of smaller grains as in the interstellar medium would be suggested for GRB 130925A.

Zhao, Yi-Nan; Shao, Lang

2014-07-01

169

Exploring the accessible frequency range of phase-resolved ferromagnetic resonance detected with x-rays  

NASA Astrophysics Data System (ADS)

We present time- and element-resolved measurements of the magnetization dynamics in a ferromagnetic trilayer structure. A pump-probe scheme was utilized with a microwave magnetic excitation field phase-locked to the photon bunches and x-ray magnetic circular dichroism in transmission geometry. Using a relatively large photon bunch length with a full width at half maximum of 650 ps, the precessional motion of the magnetization was resolved up to frequencies of 2.5 GHz, thereby enabling sampling at frequencies significantly above the inverse bunch length. By simulating the experimental data with a numerical model based on a forced harmonic oscillator, we obtain good correlation between the two. The model, which includes timing jitter analysis, is used to predict the accessible frequency range of x-ray detected ferromagnetic resonance.

Warnicke, P.; Knut, R.; Wahlström, E.; Karis, O.; Bailey, W. E.; Arena, D. A.

2013-01-01

170

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

171

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

172

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

173

Spectral response compensation for photon-counting clinical x-ray CT using sinogram restoration  

NASA Astrophysics Data System (ADS)

The x-ray spectrum recorded by a photon-counting x-ray detector (PCXD) is distorted due to the following physical effects which are independent of the count rate: finite energy-resolution, Compton scattering, charge-sharing, and Kescape. If left uncompensated, the spectral response (SR) of a PCXD due to the above effects will result in image artifacts and inaccurate material decomposition. We propose a new SR compensation (SRC) algorithm using the sinogram restoration approach. The two main contributions of our proposed algorithm are: (1) our algorithm uses an efficient conjugate gradient method in which the first and second derivatives of the cost functions are directly calculated analytically, whereas a slower optimization method that requires numerous function evaluations was used in other work; (2) our algorithm guarantees convergence by combining the non-linear conjugate gradient method with line searches that satisfy Wolfe conditions, whereas the algorithm in other work is not backed by theorems from optimization theory to guarantee convergence. In this study, we validate the performance of the proposed algorithm using computer simulations. The bias was reduced to zero from 11%, and image artifacts were removed from the reconstructed images. Quantitative K-edge imaging in possible only when SR compensation is done.

Srivastava, Somesh; Cammin, Jochen; Fung, George S. K.; Tsui, Benjamin M. W.; Taguchi, Katsuyuki

2012-02-01

174

Spectral comparison of weak short bursts to the persistent X-rays from the magnetar 1E 1547.0-5408 in its 2009 outburst  

NASA Astrophysics Data System (ADS)

In 2009 January, the 2.1-s anomalous X-ray pulsar 1E 1547.0-5408 evoked intense burst activity. A follow-up Suzaku observation on January 28 recorded enhanced persistent emission in both soft and hard X-rays. Through a reanalysis of the same Suzaku data, 18 short bursts were identified in the X-ray events recorded by the Hard X-ray Detector (HXD) and the X-ray Imaging Spectrometer (XIS). Their spectral peaks appear in the HXD-PIN band, and their 10-70 keV X-ray fluences range from ˜2 × 10-9 to 10-7 erg cm-2. Thus, the 18 events define a significantly weaker burst sample than has ever been obtained previously, ˜10-8-10-4 erg cm-2. In the ˜0.8 to ˜300 keV band, the spectra of the three brightest bursts can be represented successfully by a two-blackbody model, or a few alternative models. A spectrum that is constructed by stacking 13 weaker short bursts with fluences in the range (0.2-2) × 10-8 erg s-1 is less curved, and its ratio to the persistent emission spectrum becomes constant at ˜170 above ˜8 keV. As a result, the two-blackbody model was able to reproduce the stacked weaker-burst spectrum only after adding a power-law model, for which the photon index is fixed at 1.54 as measured by the persistent spectrum. These results imply that there is a possibility that the spectrum composition that employs an optically thick component and a hard power-law component can describe the wide-band spectra of both the persistent and weak-burst emissions, despite the fact that their fluxes differ by two orders of magnitude. Based on the spectral similarity, we discuss a possible connection between the unresolved short bursts and the persistent emission.

Enoto, T.; Nakagawa, Y. E.; Sakamoto, T.; Makishima, K.

2012-12-01

175

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

PubMed Central

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 , “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 (COVW), 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 COVW'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, COVW 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; Xu, Jennifer; Barber, William C.; Iwanczyk, Jan S.; Hartsough, Neal E.; Taguchi, Katsuyuki

2014-01-01

176

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

177

X-ray and Ultraviolet Spectral Evolution of LMC X-3 During Normal and Anomalous Low States  

NASA Astrophysics Data System (ADS)

The bright black-hole X-ray binary LMC X-3 is a lower-mass high-mass X-ray binary with a 1.7 day orbital period. Both the X-ray source and its bright optical/UV companion show non-periodic high amplitude variability on timescales much longer than this (100-300 days). Previous observations do not present a clean picture of whether Roche-lobe overflow or wind accretion is the dominant mechanism driving this dramatic long-term variability. RXTE monitoring has recently revealed that LMC X-3 undergoes surprising anomalous low states (ALSs), during which the X-ray source is virtually indistinguishable from background, and stays low for three to six months at a time (Smale & Boyd 2012). The cause of these ALSs is not known. NASA's Swift telescope is uniquely capable of shedding light on this mystery by providing simultaneous X-ray, UV, and optical observations of the source during its normal long-term variability. Swift has obtained simultaneous multiwavelength data at a variety of X-ray fluxes while the system was displaying its normal variability state, as well as dense monitoring during an ALS and during a recent normal low state. Comparison of X-ray spectral modeling with the UV variability offers the best chance to disentangle the various sources of UV radiation in the system. We present the results of spectral fitting of the Swift XRT and, when available, XMM/Newton spectra which probe the accretion state of the black hole. We compare these with the UV flux arising from the stellar surface and outer accretion disk, searching for correlations and lags that could reveal whether a substantial fraction of the UV flux is due to reprocessing of X-rays within the system, or arises from another mechanism.

Torpin, Trevor; Boyd, P. T.; Smale, A. P.

2014-01-01

178

Spectral Constraints on SEYFERT-2 Galaxies as Major Contributors to the Hard 3-100-KEV X-Ray Background  

NASA Astrophysics Data System (ADS)

It has been suggested that the flat spectrum of the X-ray background (XRB) above 3 keV and below ~15 keV could be explained by the superposition of absorbed sources at different redshifts. To explain the steepening of the XRB spectrum above ~15 keV, the intrinsic source spectrum should cut off at ~50-100 keV, as observed in NGC 4151 and galactic black hole candidates. Here, assuming that Seyfert 2 galaxies are Seyfert 1 galaxies obscured by intervening matter in the line of sight, as postulated by the unified model, and that they provide the major contribution to the XRB in the 3-100 keV energy range, we derive some constraints on their spectrum and evolution, and indicate, in view of future ASCA measurements, the use of iron spectral features as a test of the model.

Matt, G.; Fabian, A. C.

1994-03-01

179

Automated X-ray Spectral Classification of Young Stellar Sources Detected in Chandra Orion Ultradeep Project Observations  

NASA Astrophysics Data System (ADS)

We are developing an automated classification technique to group X-ray sources detected in CCD imaging into clusters based on X-ray spectral attributes. The algorithm is non-parametric and uses established multivariate statistics and pattern recognition techniques. We have applied this spectral classification technique to a sample of sources selected from among the 1616 X-ray sources detected in Chandra Orion Ultradeep Project (COUP) imaging. The COUP dataset was compiled from an 850 ks Chandra observation of the Orion Nebula Cluster (ONC) that was obtained in January 2003 with the Advanced CCD Imaging Spectrometer (ACIS), and represents by far the most sensitive and comprehensive description of X-ray emission from a pre-main sequence star cluster (Getman et al. 2005, ApJS, in press; astro-ph/0410136). We describe preliminary classification results for a subset of approximately 440 COUP sources for which high-quality ACIS spectra can be extracted. These results demonstrate that our spectral clustering technique can be used to efficiently identify pre-main sequence X-ray sources that lack optical or near-infrared counterparts and that display strong Fe K? line emission and/or large-amplitude, impulsive flares. Within the COUP dataset, such sources likely represent the youngest protostars in the ONC.

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

2004-12-01

180

High Resolution Temporal and Spectral Monitoring of Eta Carinae's X-Ray Emission the June Eclipse  

NASA Technical Reports Server (NTRS)

The supermassive and luminous star Eta Carinae undergoes strong X-ray variations every 5.5 years when its 2-10 keV X-ray emission brightens rapidly with wild fluctuations before dropping by a factor of 100 to a minimum lasting 3 months. The most recent X-ray "eclipse" began in June 2003 and during this time Eta Carinae was intensely observed throughout the electromagnetic spectrum. Here we report the first results of frequent monitoring of the 2-10 keV band X-ray emission by the Rossi X-ray Timing Explorer along wit high resolution X-ray spectra obtained with the transmission gratings on the Chandra X-ray Observatory. We compare these observations to those results obtained during the previous X-ray eclipse in 1998, and interpret the variations in the X-ray brightness, in the amount of absorption, in the X-ray emission measure and in the K-shell emission lines in terms of a colliding wind binary model.

Corcoran, M. F.; Hamaguchi, K.; Henley, D.; Pittard, J. M.; Gull, T. R.; Davidson, K.; Swank, J. H.; Petre, R.; Ishibashi, K.

2004-01-01

181

The Broadband X-Ray Spectral Features of a Sample of Seyfert 1 Galaxies  

NASA Astrophysics Data System (ADS)

The archival BeppoSAX (MECS and PDS) data, for a sample of the fifteen brightest Seyfert 1 galaxies, are analyzed to examine the broad-band X-ray spectral features of Compton reflection and iron line flourescence, which arise from the inner regions around the supermassive black hole, such as the putative torus and/or the accretion disk. The results from the Chandra HETG observations for this sample (see Yaqoob & Padmanabhan 2004) are used to fix the line core parameters, with the intensity of the line free to vary as the two instruments are not cross normalized. We checked for the presence of a relativistically broadened iron line and tried to constrain the line parameters. We also looked for variability in the spectral features since many of the objects in our sample had been observed multiple times by BeppoSAX. Lastly we looked for evidence of a relation between the equivalent width W of the iron line and the reflection coefficient R and the equivalent width W and the slope of the power law.

Padmanabhan, Urmila; Weaver, K. A.; Yaqoob, T.

2006-12-01

182

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

183

Morphometry, scanning electron microscopy and x-ray spectral microanalysis of protostylid pits on human lower third molars  

Microsoft Academic Search

Protostylid pits on 50 lower third molars were studied. The depth and width of the pits, the thickness of the enamel at the pit bottom and the concavity of the dentino-enamel junction under the pit were measured by light microscopy. The pit content was examined by scanning electron microscopy and X-ray spectral microanalysis. The results show that the morphometric variables

Dominik Gašperši?

1996-01-01

184

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

185

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

186

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

SciTech Connect

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.

Ding Huanjun; Molloi, Sabee [Department of Radiological Sciences, University of California, Irvine, California 92697 (United States)

2012-04-15

187

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

SciTech Connect

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{sup -5}-10{sup -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{sub 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{sub 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.

Hong Xinguo; Chen Zhiqiang [Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794 (United States); Duffy, Thomas S. [Department of Geosciences, Princeton University, Princeton, New Jersey 08544 (United States)

2012-06-15

188

Linking the X-ray timing and spectral properties of the glitching AXP 1RXS J170849-400910  

Microsoft Academic Search

Aims:Previous studies of the X-ray flux and spectral properties of 1RXS J170849-400910 showed a possible correlation with the spin glitches that occurred in 1999 and 2001. However, due to the sparseness of spectral measurements and the paucity of detected glitches, no firm conclusion could be drawn. Methods: We retrieved and analysed archival Rossi-XTE pointings of 1RXS J170849-400910 covering the time

G. L. Israel; D. Götz; S. Zane; S. Dall'Osso; N. Rea; L. Stella

2007-01-01

189

Multi-spectral solar telescope array II; Soft x-ray/euv reflectivity of the multilayer mirrors  

SciTech Connect

In this paper, the authors 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. The authors report on extensive measurements of the efficiency and spectral bandpass of the XUV telescopes carried out at the Stanford Synchrotron Radiation Laboratory.

Barbee, T.W. Jr.; Weed, J.W. (Lawrence Livermore National Lab., Livermore, CA (US)); Hoover, R.M. (NASA Marshall Space Flight Center, Space Science Lab., Huntsville, AL (US)); Allen, M.J.; Lindblom, J.F.; O'Neal, R.H.; Kankelborg, C.C.; DeForest, C.E.; Paris, E.S.; Walker, A.B.C. Jr.; Willis, T.D. (Stanford Univ., Center for Space Science and Astrophysics, Stanford, CA (US)); Gluskin, E. (Argonne National Lab., Argonne, IL (US)); Pianetta, P. (Stanford Univ., Stanford Synchrotron Radiation Lab., Stanford, CA (US)); Baker, P.C. (Baker Consulting, Walnut Creek, CA (US))

1991-08-01

190

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

191

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

192

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

193

Effective dynamic range measurement for a CCD in full-field industrial x-ray imaging applications  

Microsoft Academic Search

CCD cameras are widely used for different applications. Recently they are employed for imaging in industrial X-ray digital radiography or computed tomography inspections. Scientific grade CCD sensors are usually characterized for what concern defects (bad pixels), resolution capability, spectral sensitivity, dark current, pixel full well capacity and so on. In former times CCDs were mostly used in astronomy and dark

Matteo Bettuzzi; Rosa Brancaccio; Maria Pia Morigi; Franco Casali

2007-01-01

194

High dynamic range pixel architecture for advanced diagnostic medical x-ray imaging applications  

SciTech Connect

The most widely used architecture in large-area amorphous silicon (a-Si) flat panel imagers is a passive pixel sensor (PPS), which consists of a detector and a readout switch. While the PPS has the advantage of being compact and amenable toward high-resolution imaging, small PPS output signals are swamped by external column charge amplifier and data line thermal noise, which reduce the minimum readable sensor input signal. In contrast to PPS circuits, on-pixel amplifiers in a-Si technology reduce readout noise to levels that can meet even the stringent requirements for low noise digital x-ray fluoroscopy (<1000 noise electrons). However, larger voltages at the pixel input cause the output of the amplified pixel to become nonlinear thus reducing the dynamic range. We reported a hybrid amplified pixel architecture based on a combination of PPS and amplified pixel designs that, in addition to low noise performance, also resulted in large-signal linearity and consequently higher dynamic range [K. S. Karim et al., Proc. SPIE 5368, 657 (2004)]. The additional benefit in large-signal linearity, however, came at the cost of an additional pixel transistor. We present an amplified pixel design that achieves the goals of low noise performance and large-signal linearity without the need for an additional pixel transistor. Theoretical calculations and simulation results for noise indicate the applicability of the amplified a-Si pixel architecture for high dynamic range, medical x-ray imaging applications that require switching between low exposure, real-time fluoroscopy and high-exposure radiography.

Izadi, Mohammad Hadi; Karim, Karim S. [School of Engineering Science, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada)

2006-05-15

195

The Drop in X-ray Flux at Spectral Type B1: Evidence for a B-Star Dividing Line?  

NASA Astrophysics Data System (ADS)

All B star luminosity classes show a substantial drop in their X-ray emission between spectral type B1 and B2 suggesting an H-R diagram B-star dividing line somewhat analogous to the one for K giants. This emission appears to be related to the bi-stability jump at spectral type B1. But our analyses of B supergiant and giant XMM data revealed several interesting and unexpected results that do not support theoretical predictions. There seems to be a fundamental, unknown, underlying process at work in this spectral region. We now wish to extent our study by requesting XMM EPIC observations of 4 B main sequence stars and 2 additional B giants to help us explain the abrupt X-ray changes that are occurring in this intriguing region of the H-R diagram.

Waldron, Wayne

2009-10-01

196

The Drop in X-ray Flux at Spectral Type B1: Evidence for a B-Star Dividing Line?  

NASA Astrophysics Data System (ADS)

All B star luminosity classes show a substantial drop in their X-ray emission between spectral type B1 and B2 suggesting an H-R diagram B-star dividing line somewhat analogous to the one for K giants. This emission appears to be related to the bi-stability jump at spectral type B1. But our analyses of B supergiant and giant XMM data revealed several interesting and unexpected results that do not support theoretical predictions. There seems to be a fundamental, unknown, underlying process at work in this spectral region. We now wish to extent our study by requesting XMM EPIC observations of 4 B main sequence stars and 1 additional B giant to help us explain the abrupt X-ray changes that are occurring in this intriguing region of the H-R diagram.

Waldron, Wayne

2010-10-01

197

Evaluating the impact of x-ray spectral shape on image quality in flat-panel CT breast imaging  

SciTech Connect

In recent years, there has been an increasing interest in exploring the feasibility of dedicated computed tomography (CT) breast imaging using a flat-panel digital detector in a truncated cone-beam imaging geometry. Preliminary results are promising and it appears as if three-dimensional tomographic imaging of the breast has great potential for reducing the masking effect of superimposed parenchymal structure typically observed with conventional mammography. In this study, a mathematical framework used for determining optimal design and acquisition parameters for such a CT breast imaging system is described. The ideal observer signal-to-noise ratio (SNR) is used as a figure of merit, under the assumptions that the imaging system is linear and shift invariant. Computation of the ideal observer SNR used a parallel-cascade model to predict signal and noise propagation through the detector, as well as a realistic model of the lesion detection task in breast imaging. For all evaluations, the total mean glandular dose for a CT breast imaging study was constrained to be approximately equivalent to that of a two-view conventional mammography study. The framework presented was used to explore the effect of x-ray spectral shape across an extensive range of kVp settings, filter material types, and filter thicknesses. The results give an indication of how spectral shape can affect image quality in flat-panel CT breast imaging.

Glick, Stephen J.; Thacker, Samta; Gong Xing; Liu, Bob [Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655 (United States); Radiation Monitoring Devices, Inc., 44 Hunt Street, Watertown, Massachusetts 02172 (United States); Department of Medical Physics and Radiation Oncology, Rush University Medical Center, Chicago, Illinois, 60612 (United States); Massachusetts General Hospital, Boston, Massachusetts 02114 (United States)

2007-01-15

198

Novel instrumentation for spectrally resolved soft x-ray plasma tomography: Development and pilot results on TEXTOR  

NASA Astrophysics Data System (ADS)

A novel instrumentation for wavelength- and time-resolved plasma emission tomography in the range 0.1-4 keV has been demonstrated on the Torus Experiment for Technology Oriented Research (TEXTOR). The technique is intended for reconstruction of distributions of local emission coefficients (LEC) for selected spectral lines of impurity ions. Further determination (with additional data on electron density and temperature) of spatial distributions of impurity ions at particular ionization stages will become feasible. Spectrally selective plasma images at several viewpoints around plasma are obtained with miniature pinhole cameras supplemented with multilayer mirrors as dispersion elements. The x-ray image is converted to a visible image and transported by a fiber bundle to a gain enhanced recording camera with an electron bombarded charge coupled device tube. A part of the system has been installed on temporary TEXTOR ports. First demonstration results have been obtained on plasma imaging and on subsequent LEC reconstruction using a modified iterative sinogram restoration tomography algorithm. The complete diagnostics will be operational after the TEXTOR shutdown in 2001.

Shmaenok, L. A.; Golovkin, S. V.; Govorun, V. N.; Ekimov, A. V.; Salashchenko, N. N.; Pickalov, V. V.; Belik, V. P.; Schüller, F. C.; Donné, A. J. H.; Oomens, A. A. M.; Prokhorov, K. A.; Andreev, S. S.; Sorokin, A. A.; Podlaskin, B. G.; Khasanov, L. V.

2001-02-01

199

Spectral and Timing Investigations of Dwarf Novae Selected in Hard X-Rays  

NASA Technical Reports Server (NTRS)

There are 9 dwarf novae (DN) among the 43 cataclysmic variables (accreting white dwarfs in close binary systems) that were detected during the HEAO-1 all-sky X-ray survey (1977-1979). On the other hand, there are roughly one hundred dwarf novae that are closer and/or optically brighter and yet they were not detected as hard X-ray sources. Two of the HEAO-1 DN show evidence for X-ray pulsations that imply strong magnetic fields on the white dwarf surface, and magnetic CVs are known to be strong X-ray sources. However, substantial flux in hard X-rays may be caused by non-magnetic effects, such as an optically thin boundary layer near a massive white dwarf. We proposed RXTE observations to measure plasma temperatures and to search for X-ray pulsations. The observations would distinguish whether these DN belong to one of (rare) magnetic subclasses. For those that do not show pulsations, the observations support efforts to define empirical relations between X-ray temperature, the accretion rate, and the mass of the white dwarf. The latter is determined via optical studies of the dynamics of the binary constituents.

Thorstensen, John; Remillard, Ronald A.

2000-01-01

200

High-power 1 kHz laser-plasma x-ray source for ultrafast x-ray absorption near-edge spectroscopy in the keV range  

Microsoft Academic Search

A high average power broadband x-ray source is developed in the multi-keV range, based on the thermal emission of plasmas produced with a 1 kHz fs laser focused on high Z element target. This compact ultrafast x-ray source is used to measure the x-ray absorption near-edge spectroscopy of aluminum K-edge (1.559 keV) with noise lower than 1% of the absorption

F. Dorchies; M. Harmand; D. Descamps; C. Fourment; S. Hulin; S. Petit; O. Peyrusse; J. J. Santos

2008-01-01

201

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

NASA Technical Reports Server (NTRS)

The proposed research uses the electron beam ion trap at the Lawrence Livermore National Laboratory (LLNL) to study X-ray emission from charge-exchange recombination of highly charged ions with neutral gases. The resulting data 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, supernova ejecta, and photoionized nebulae. Progress made during the first year of the grant is described, as is work planned for the second year.

Wargelin, B.

2002-01-01

202

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

203

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

204

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

205

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

206

X-ray laser resonator for the kilo-electron-volt range  

SciTech Connect

We have designed, constructed, and tested an x-ray laser resonator operating in the hard x-ray, keV energy region. This ring x-ray laser cavity is formed by four highly oriented pyrolytic graphite crystals. The crystals are set at the Bragg angles that allow for the complete 360 Degree-Sign round trip of the 2.37 A, 5.23 keV L{sub {alpha}} line of neodymium. In addition, we also present experimental data of a similar ring laser resonator that utilizes the Cr K{sub {alpha}}, 5.41 keV, x-ray line to propagate through the four mirrors of the cavity. The specific properties of these x-ray laser resonator mirrors, including reflection losses and cavity arrangement, are presented.

Chen, Jie [Department of Chemistry, University of California, Irvine, California 92697 (United States) [Department of Chemistry, University of California, Irvine, California 92697 (United States); Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Tomov, Ivan V.; Er, Ali O.; Rentzepis, Peter M. [Department of Chemistry, University of California, Irvine, California 92697 (United States)] [Department of Chemistry, University of California, Irvine, California 92697 (United States)

2013-04-29

207

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

208

The Hard X-Ray - and Spectral Characteristics of Millisecond Pulsar PSR J0218+4232  

NASA Astrophysics Data System (ADS)

We propose to observe millisecond pulsar PSR J0218+4232 for 200 ks with RXTE to determine its hard X-ray characteristics in detail. In a recent BeppoSAX MECS observation pulsed 1.6-10 keV X-rays have been detected with a double peak lightcurve. The total pulsed spectrum is the hardest measured for any radio pulsar . Remarkably, at high gamma-ray energies pulsed emission is most likely detected in CGRO EGRET data (0.1 - 1 GeV). A RXTE observation will yield a hard X-ray pulse profile above 10 keV in absolute phase which can only be obtained with RXTE among current X-ray observatories. The aligned pulse profiles from radio up to gamma-rays will provide indispensable information to study the production processes and sites of high-energy radiation in the magnetosphere of this pulsar.

Kuiper, Lucien

209

X-ray spectral variability in PG 1535+547: the changing look of a ``soft X-ray weak'' AGN  

Microsoft Academic Search

Context: PG 1535+547 is a bright Narrow Line Seyfert 1 galaxy, whose high-energy emission shows strong variability both in shape and flux. On the basis of ROSAT observations, it is classified as ``soft X-ray weak quasi-stellar object (QSO)'', a class of objects whose X-ray-to-optical flux ratio is smaller than in typical QSOs. Their X-ray spectra are often characterized by highly-ionized,

L. Ballo; M. Giustini; N. Schartel; M. Cappi; E. Jiménez-Bailón; E. Piconcelli; M. Santos-Lleó; C. Vignali

2008-01-01

210

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

NASA Technical Reports Server (NTRS)

The proposed research uses the electron beam ion trap at the Lawrence Livermore National Laboratory to study the X-ray emission from charge-exchange recombination of highly charged ions with neutral gases. The resulting data fill a void in the existing experimental and theoretical data and are needed to explain all or part of the observed X-ray emission from the Galactic Ridge, solar and stellar winds, the Galactic Center, supernova ejecta, and photoionized nebulae.

Wargelin, B.

2003-01-01

211

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

212

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

Microsoft Academic Search

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

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

1985-01-01

213

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

214

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

215

Prediction and Measurement of X-Ray Spectral and Intensity Distributions from Low Energy Electron Impact Sources  

NASA Technical Reports Server (NTRS)

In-vacuum electron beam welding is a technology that NASA considered as a joining technique for manufacture of space structures. The interaction of energetic electrons with metal produces x-rays. The radiation exposure to astronauts performing the in-vacuum electron beam welding must be characterized and minimized to insure safe operating conditions. This investigation characterized the x-ray environment due to operation of an in-vacuum electron beam welding tool. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the United States Space Shuttle. This series of experiments was named the International Space Welding Experiment (ISWE). The hardware associated with the ISWE was leased to NASA, by the Paton Welding Institute (PWI) in Ukraine, for ground based welding experiments in preparation for flight. Two tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests consisted of Thermoluminescence Dosimeters (TLD's) shielded with material currently used by astronauts during Extra Vehicular Activities (EVA) and exposed to x-ray radiation generated by operation of an in-vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x-rays of energy less than 10 KeV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was verified. Therefore, alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by electron impact with metal. These x-ray spectra were used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in good agreement with the TLD values.

Edwards, David L.

1999-01-01

216

The X-ray flux and spectral variability of the Einstein Extended Medium Sensitivity Survey AGN  

Microsoft Academic Search

Fifteen ROSAT PSPC observations available in the public archive are analyzed in order to study time and spectral variability of the 12 Einstein Extended Medium Sensitivity Survey (EMSS) AGN detected by ROSAT with more than 2000 net counts. Time variability was investigated on 13 different time-scales, ranging from 400 to 3.15 x 10 exp 6 s (1 yr). Of the

Paolo Ciliegi; Tommaso Maccacaro

1997-01-01

217

X-ray lithography fabrication of a zone plate for X-rays in the range from 15 to 30 keV  

Microsoft Academic Search

Progress on the fabrication of zone plates for hard X-rays is reported. The issue of achieving a high aspect ratio for lithographic structures has been addressed by developing a specific fabrication protocol based on the combined use of electron beam and proximity X-ray lithography. An example of a 1 mm diameter wide zone plate, optimized for a 23 keV X-ray

Matteo Altissimo; Filippo Romanato; Lisa Vaccari; Luca Businaro; Danut Cojoc; Burkhard Kaulich; Stefano Cabrini; Enzo Di Fabrizio

2002-01-01

218

Determining the X-ray Contribution of Hard State X-ray Binary Jets: New Results from Simultaneous Broadband Spectral Fitting  

NASA Astrophysics Data System (ADS)

The hard state of X-ray binaries (XRBs) is associated with a hard power law spectrum in the X-ray band, generally modeled via inverse Comptonization of thermal disk photons by a corona. This state is also associated with compact, continuous jets whose radio synchrotron emission is correlated with the hard X-rays. The exact nature of this relationship is still under debate, and an effective way of addressing this question is to model the entire broadband spectrum self-consistently. Depending on the location of the optically thick-to-thin break and the emitting particle distribution, jet synchrotron radiation can contribute significantly to the X-ray band, in addition to synchrotron self-Compton emission from near the base of the jets. We have imported our jet models into X-ray data analysis software to allow the simultaneous fitting of radio and IR data along with the traditional X-ray bands. We present the fits to broadband simultaneous data sets, including X-ray data from the Rossi XTE mission, for several XRBs, including Cyg X-1 and GX 339-4. Our best results show contributions from both direct synchrotron radiation as well as a strong SSC component. With the addition of line and reflection features, jet models provide as good a description of the X-ray data as thermal Comptonization models, while also addressing the radio/IR components. S.M. is supported by an NSF Astronomy & Astrophysics postdoctoral fellowship.

Markoff, S.; Nowak, M. A.; Wilms, J.

2004-08-01

219

THE CHANDRA MULTI-WAVELENGTH PROJECT: OPTICAL SPECTROSCOPY AND THE BROADBAND SPECTRAL ENERGY DISTRIBUTIONS OF X-RAY-SELECTED AGNs  

SciTech Connect

From optical spectroscopy of X-ray sources observed as part of the Chandra Multi-wavelength Project (ChaMP), we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow-up using the FLWO/1.5 m, SAAO/1.9 m, WIYN 3.5 m, CTIO/4 m, KPNO/4 m, Magellan/6.5 m, MMT/6.5 m, and Gemini/8 m telescopes, and from archival Sloan Digital Sky Survey (SDSS) spectroscopy. We classify the optical counterparts as 50% broad-line active galactic nuclei (AGNs), 16% emission line galaxies, 14% absorption line galaxies, and 20% stars. We detect QSOs out to z {approx} 5.5 and galaxies out to z {approx} 3. We have compiled extensive photometry, including X-ray (ChaMP), ultraviolet (GALEX), optical (SDSS and ChaMP-NOAO/MOSAIC follow-up), near-infrared (UKIDSS, Two Micron All Sky Survey, and ChaMP-CTIO/ISPI follow-up), mid-infrared (WISE), and radio (FIRST and NVSS) bands. Together with our spectroscopic information, this enables us to derive detailed spectral energy distributions (SEDs) for our extragalactic sources. We fit a variety of template SEDs to determine bolometric luminosities, and to constrain AGNs and starburst components where both are present. While {approx}58% of X-ray Seyferts (10{sup 42} erg s{sup -1} < L{sub 2-10keV} <10{sup 44} erg s{sup -1}) require a starburst event (>5% starburst contribution to bolometric luminosity) to fit observed photometry only 26% of the X-ray QSO (L{sub 2-10keV} >10{sup 44} erg s{sup -1}) population appear to have some kind of star formation contribution. This is significantly lower than for the Seyferts, especially if we take into account torus contamination at z > 1 where the majority of our X-ray QSOs lie. In addition, we observe a rapid drop of the percentage of starburst contribution as X-ray luminosity increases. This is consistent with the quenching of star formation by powerful QSOs, as predicted by the merger model, or with a time lag between the peak of star formation and QSO activity. We have tested the hypothesis that there should be a strong connection between X-ray obscuration and star formation but we do not find any association between X-ray column density and star formation rate both in the general population or the star-forming X-ray Seyferts. Our large compilation also allows us to report here the identification of 81 X-ray Bright Optically inactive Galaxies, 78 z > 3 X-ray sources, and eight Type-2 QSO candidates. Also, we have identified the highest redshift (z = 5.4135) X-ray-selected QSO with optical spectroscopy.

Trichas, Markos; Green, Paul J.; Aldcroft, Tom; Kim, Dong-Woo; Mossman, Amy [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Silverman, John D. [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8568 (Japan); Barkhouse, Wayne [Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202 (United States); Cameron, Robert A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Constantin, Anca [Department of Physics and Astronomy, James Madison University, PHCH, Harrisonburg, VA 22807 (United States); Ellison, Sara L. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 1A1 (Canada); Foltz, Craig [Division of Astronomical Sciences, National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22230 (United States); Haggard, Daryl [Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Jannuzi, Buell T. [NOAO, Kitt Peak National Observatory, Tucson, AZ 85726 (United States); Marshall, Herman L. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Perez, Laura M. [Department of Astronomy, California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125 (United States); Romero-Colmenero, Encarni [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Ruiz, Angel [Osservatorio Astronomico di Brera-INAF, Milan (Italy); Smith, Malcolm G., E-mail: mtrichas@cfa.harvard.edu [Cerro Tololo Interamerican Observatory, La Serena (Chile); and others

2012-06-01

220

The X-ray spectral properties of the AGN population in the XMM-Newton bright serendipitous survey  

NASA Astrophysics Data System (ADS)

Context. X-ray surveys are a key instrument in the study of active galactic nuclei (AGN). Thanks to their penetrating ability, X-rays are able to map the innermost regions close to the central super massive black hole (SMBH) as well as to detect and characterize its emission up to high redshift. Aims: We present here a detailed X-ray spectral analysis of the AGN belonging to the XMM-Newton bright survey (XBS). The XBS is composed of two flux-limited samples selected in the complementary 0.5-4.5 and 4.5-7.5 keV energy bands and comprising more than 300 AGN up to redshift ~2.4. Methods: We performed an X-ray analysis following two different approaches: by analyzing individually each AGN X-ray spectrum and by constructing average spectra for different AGN types. Results: From the individual analysis, we find that there seems to be an anti correlation between the spectral index and the sources' hard X-ray luminosity, such that the average photon index for the higher luminosity sources (>1044 erg s-1) is significantly (>2?) flatter than the average for the lower luminosity sources. We also find that the intrinsic column density distribution agrees with AGN unified schemes, although a number of exceptions are found (3% of the whole sample), which are much more common among optically classified type 2 AGN. We also find that the so-called "soft-excess", apart from the intrinsic absorption, constitutes the principal deviation from a power-law shape in AGN X-ray spectra and it clearly displays different characteristics, and likely a different origin, for unabsorbed and absorbed AGN. Regarding the shape of the average spectra, we find that it is best reproduced by a combination of an unabsorbed (absorbed) power law, a narrow Fe K? emission line and a small (large) amount of reflection for unabsorbed (absorbed) sources. We do not significantly detect any relativistic contribution to the line emission and we compute an upper limit for its equivalent width (EW) of 230 eV at the 3? confidence level. Finally, by dividing the type 1 AGN sample into high- and low-luminosity sources, we marginally detect a decrease in the narrow Fe K? line EW and in the amount of reflection as the luminosity increases, the "so-called" Iwasawa-Taniguchi effect. Appendix and Tables 2, 3 are available in electronic form at http://www.aanda.org

Corral, A.; Della Ceca, R.; Caccianiga, A.; Severgnini, P.; Brunner, H.; Carrera, F. J.; Page, M. J.; Schwope, A. D.

2011-06-01

221

Solar active region physical parameters inferred from a thermal cyclotron line and soft X-ray spectral lines  

NASA Technical Reports Server (NTRS)

Simultaneous high-resolution observations of coronal loops were made at the 20-cm wavelength with the VLA and at soft X-ray wavelengths with the SMM FCS. The images obtained at both wavelengths have nearly identical sizes and ellipsoidal shapes, with the emission stretching between and across regions of opposite magnetic polarity in the underlying photosphere. The results indicate that the radiation at 20 cm and soft X-ray wavelengths originates from the same region, and that 20 cm maps can image X-ray coronal loops. The X-ray spectral lines were used to obtain values of electron temperature, T(e), of about 2.6 x 10 to the 6th K and electron density, N(e), of about 3.1 x 10 to the 9th/cu cm. These parameters were used to show that the layers emitting 20-cm radiation can be optically thick to either thermal bremsstrahlung or thermal gyroresonance radiation, depending upon unknown but plausible values of loop thickness, magnetic scale height, and magnetic field strength.

Lang, Kenneth R.; Willson, Robert F.; Smith, Kermit L.; Strong, Keith T.

1987-01-01

222

The Need for X-Ray Spectroscopy  

NASA Technical Reports Server (NTRS)

For over four decades, X-ray, EUV, and UV spectral observations have been used to measure physical properties of the solar atmosphere. During this time, there has been substantial improvement in the spectral, spatial, and temporal resolution of the observations for the EUV and UV wavelength ranges. At wavelengths below 100 Angstroms, however, observations of the solar corona with simultaneous spatial and spectral resolution are limited, and not since the late 1970's have spatially resolved solar X-ray spectra been measured. The soft-X-ray wavelength range is dominated by emission lines formed at high temperatures and provides diagnostics unavailable in any other wavelength range. In this presentation, we will discuss the important science questions that can be answered using spatially and spectrally resolved X-ray spectra.

Winebarger, Amy R.; Cirtain, Jonathan; Kobayashi, Ken

2011-01-01

223

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

224

Phase Resolved X-Ray Spectral Analysis of Intermediate Polars EX Hya and FO Aqr  

NASA Astrophysics Data System (ADS)

Intermediate Polars (IPs): EX Hya and FO Aqr whichs are a subclass of Cataclysmic Variables (CVs) where a white dwarf with magnetic field strength of about 1-10MG accretes material from a main sequence companion through a truncated disc. In this talk we present orbital and spin phase-resolved X-ray spectroscopy of EX Hya and orbital phase-resolved X-ray spectroscopy of FO Aqr. We utilize XMM-Newton archive data of these objects for analysis. We investigate the change of the source spectrum over the spin and orbital periods. This analysis enhances our understanding about the accretion structure in these systems, temperature and composition of the X-ray emitting region together with the structure of the outer accretion disc and absorption in the system

Pekön, Yakup; Balman, ?lölen

2014-01-01

225

The Diffuse X-ray Spectrometer Experiment  

NASA Astrophysics Data System (ADS)

The Diffuse X-ray Spectrometer Experiment, or 'DXS', is designed to measure the spectrum of the low-energy diffuse X-ray background with about 10 eV energy resolution and 15-deg spatial resolution. During a 5-day Space Shuttle mission, DXS is to measure the spectrum of ten 15 x 15 deg regions lying along a single 150-deg-long great circle arc on the sky. DXS carries two large-area X-ray Bragg spectrometers for the 44-84 A wavelength range; these permit measurement of the wavelength spectrum of the cosmic low-energy diffuse X-ray background with good spectral resolution.

Sanders, W. T.; Edgar, R. J.; Juda, M.; Kraushaar, W. L.; McCammon, D.; Snowden, S. L.; Zhang, J.; Skinner, M. A.

1992-10-01

226

High Spectral Resolution X-ray Observation of Magnetic CVs: EX Hya  

SciTech Connect

In magnetic cataclysmic variables (CVs) the primary is a highly magnetized white dwarf (WD) whose field controls the accretion flow close to the WD, leading to a shock and accretion column that radiate chiefly in X-rays. We present preliminary results from a 500 ks Chandra HETG observation of the brightest magnetic CV EX Hya. From the observational dataset we are able to measure the temperature and density at different points of the cooling accretion column using sensitive line ratios. We also construct line-based light curves to search for rotational modulation of the X-ray emission.

Luna, G; Brickhouse, N S; Mauche, C W

2008-04-07

227

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

228

Speciation of copper in a range of food types by X-ray absorption spectroscopy.  

PubMed

Copper (Cu) is an essential element and the effects of diets deficient in it are well established. However, the effects of long-term high copper intake are less clear. The chemical form of copper from food sources and its resultant bioavailability is a potentially important factor in its biological activity. X-ray Absorption Near-Edge Structure (XANES) was used to determine the chemical forms of Cu in a range of foods that would make significant contributions to total copper absorption in a standard diet, as well as a chlorinated tap water sample. Analysis of the Cu K-edge XANES spectra suggested that Cu existed in both Cu(I) and Cu(II) forms, with the following five model compounds: Cu(I) acetate; Cu(II) acetate; Cu(I)-glutathione; Cu(I)-cysteine; and, Cu(II)-histidine being fitted to the sample spectra. This research suggested that the absorption of dietary copper could vary markedly dependent on the types of food consumed and the different bioavailability of the Cu species they contain. PMID:24996304

Ceko, Melanie J; Aitken, Jade B; Harris, Hugh H

2014-12-01

229

Soft X-ray spectral fits of Geminga with model neutron star atmospheres  

NASA Technical Reports Server (NTRS)

The spectrum of the soft X-ray pulsar Geminga consists of two components, a softer one which can be interpreted as thermal-like radiation from the surface of the neutron star, and a harder one interpreted as radiation from a polar cap heated by relativistic particles. We have fitted the soft spectrum using a detailed magnetized hydrogen atmosphere model. The fitting parameters are the hydrogen column density, the effective temperature T(sub eff), the gravitational redshift z, and the distance to radius ratio, for different values of the magnetic field B. The best fits for this model are obtained when B less than or approximately 1 x 10(exp 12) G and z lies on the upper boundary of the explored range (z = 0.45). The values of T(sub eff) approximately = (2-3) x 10(exp 5) K are a factor of 2-3 times lower than the value of T(sub eff) obtained for blackbody fits with the same z. The lower T(sub eff) increases the compatibility with some proposed schemes for fast neutrino cooling of neutron stars (NSs) by the direct Urca process or by exotic matter, but conventional cooling cannot be excluded. The hydrogen atmosphere fits also imply a smaller distance to Geminga than that inferred from a blackbody fit. An accurate evaluation of the distance would require a better knowledge of the ROSAT Position Sensitive Proportional Counter (PSPC) response to the low-energy region of the incident spectrum. Our modeling of the soft component with a cooler magnetized atmosphere also implies that the hard-component fit requires a characteristic temperature which is higher (by a factor of approximately 2-3) and a surface area which is smaller (by a factor of 10(exp 3), compared to previous blackbody fits.

Meyer, R. D.; Pavlov, G. G.; Meszaros, P.

1994-01-01

230

Temporal variations and spectral properties of the Be/X-ray pulsar GRO J1008—57 studied by INTEGRAL  

NASA Astrophysics Data System (ADS)

The spin period variations and hard X-ray spectral properties of the Be/X-ray pulsar GRO J1008—57 are studied with INTEGRAL observations during two outbursts in 2004 June and 2009 March. The pulsation periods of ~ 93.66 s in 2004 and ~ 93.73 s in 2009 are determined. Pulse profiles of GRO J1008—57 during outbursts are strongly energy dependent with a double-peaked profile from 3-7 keV and a single-peaked profile in hard X-rays above 7 keV. Combined with previous measurements, we find that GRO J1008—57 has undergone a spin-down trend from 1993-2009 with a rate of ~ 4.1 × 10-5 s d-1, and could have changed into a spin-up trend after 2009. We find a relatively soft spectrum in the early phase of the 2009 outburst with cutoff energy ~ 13 keV. Above a hard X-ray flux of ~ 10-9 erg cm-2 s-1, the spectra of GRO J1008—57 during outbursts need an enhanced hydrogen absorption with column density ~ 6 × 1022 cm-2. The observed dip-like pulse profile of GRO J1008—57 in soft X-ray bands could be caused by this intrinsic absorption. Around the outburst peaks, a possible cyclotron resonance scattering feature at ~ 74 keV is detected in the spectra of GRO J1008—57 which is consistent with the feature that was reported in MAXI/GSC observations, making the source a neutron star with the highest known magnetic field (~ 6.6 × 1012 G) among accreting X-ray pulsars. This marginal feature is supported by the present detections in GRO J1008—57 following the correlation between the fundamental line energies and cutoff energies in accreting X-ray pulsars. Finally we discovered two modulation periods at ~ 124.38 d and ~ 248.78 d using RXTE/ASM light curves of GRO J1008—57. Two flare peaks appearing in the folded light curve had different spectral properties. The normal outburst lasting 0.1 of an orbital phase had a hard spectrum and could not be significantly detected below 3 keV. The second flare lasting ten days showed a very soft spectrum without significant detections above 5 keV. GRO J1008—57 is a good candidate of an accreting system with an equatorial circumstellar disk around the companion star. The neutron star passing the disk of the Be star near periastron and apastron produces two X-ray flares. The soft spectral properties in the secondary flares still need further detailed studies with soft X-ray spectroscopy.

Wang, Wei

2014-05-01

231

X-ray spectral analysis of sulfur in the technology of hollow glass microspheres  

Microsoft Academic Search

A modern method for the analysis of silicate materials, which have found increasing use lately, is that of x-ray fluorescence analysis (XRFA) [3]. This method has been used, in particular, to determine the sulfur content in glass in studies of SO 3 solubility in melts of sodalime silicate glasses as part of the study of clarification of those glasses [3,

V. V. Budov; V. I. Fetikov

1992-01-01

232

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.

233

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

234

Particle beam modulation techniques for the generation of subfemtosecond photon pulses in the VUV/soft X-ray range  

NASA Astrophysics Data System (ADS)

In this paper we consider the energy modulation of a short subinterval of an electron bunch at the scale length of visible/UV laser light. Possibilities for converting this modulation into a high-gain FEL-type density fluctuation to produce a coherently-enhanced subfemtosecond radiation pulse in the VUV/soft X-ray range are discussed.

Tatchyn, Roman

1995-02-01

235

Spectrally Resolved Imaging of X-Ray Self Emission from NIF Implosions  

NASA Astrophysics Data System (ADS)

Accurately assessing and optimizing the implosion performance of inertial confinement fusion capsules is a crucial step to achieving ignition on the NIF. We have applied differential filtering (matched Ross filter pairs) to provide spectrally resolved time-integrated absolute emission images of the imploded core of cryogenic layered targets. By limiting the spectral range of imaging, we can diagnose the hydrodynamic mix of Ge-doped ablator mass within the hot spot, core symmetry without interpenetration mix, shell assembly, and distribution of temperature and hot spot mass. Further, the measured brightness of Ge K-shell emission and bremsstrahlung allows for the inference of burn-weighted electron temperature, hot spot mass, rhoR, density, and pressure. Experimental results and a simple hot spot pressure model will be presented.

Ma, T.; Izumi, N.; Bradley, D. K.; Cerjan, C. J.; Dixit, S.; Landen, O. L.; MacKinnon, A. J.; Meezan, N. B.; Prasad, R. R.; Springer, P. T.; Town, R. P. J.; Weber, S. V.; Glenzer, S. H.; Kline, J. L.; Kyrala, G.

2011-11-01

236

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

237

Structural, infrared, x-ray photoelectron, and Raman spectral characterization of electrochromic nickel oxide films  

NASA Astrophysics Data System (ADS)

Nickel oxide films were deposited onto indium-tin oxide coated substrates by electron-beam evaporation and were electrochemically colored and bleached in KOH electrolyte. X-ray diffraction, infrared, x-ray photoelectronic and Raman spectroscopy were used to characterize the films. Results show that the as-deposited films are composed of crystallites with preferential orientation of cubic NiO(111), and retain their original structure after electrochromic redox reaction. The boundary and surface of the NiO crystallites play a critical role in the electrochromic reaction, the sites of the injection and ejection of OH- ions and relevant electrochromic reaction are at the interface of NiO crystallites, the major composition at the interfaces of the crystallites are NiO for the as-deposited films, NiOOH for the colored films and Ni(OH)2 for the bleached films.

Wu, Yonggang; Wu, Guangming; Ni, Xingyuan; Wu, Xiang

2000-11-01

238

``Transition-Edge Sensors for Solar X-ray Spectral Observations - An Update''  

Microsoft Academic Search

ABSTRACT: The advent of cryogenic microcalorimeters (operating at temperatures of ˜ 0.1 K) in ground-based and space-based astronomy promises a revolution of new discoveries. Particularly, Transition-Edge Sensors (TES) have demonstrated high-energy resolution measurements of soft X-rays of up to E\\/Delta E ˜ 1500 (at 6keV) and with high temporal resolution of a msec or less in photon pulse detections. Fabricated

D. S. Martinez-Galarce; R. Stern; B. Cabrera; S. Deiker; D. Alexander; T. Metcalf; K. Irwin; P. Brink; P. F. Boerner; K. Morse; S. Leman; L. Shing; A. Rausch; T. D. Nichols; S. Chakraborty

2004-01-01

239

Measurements of x-ray spectral flux and intensity distribution of APS/CHESS undulator radiation  

SciTech Connect

Absolute radiation flux and polarization measurements of the APS undulators may have to be made under high thermal loading conditions. A method that may circumvent the high-heat-load problem was tested during a recent APS/CHESS undulator run. The technique makes use of a Si(Li) energy-dispersive detector to measure 5--35 keV x-rays scattered from a well-defined He gas volume at controlled pressure.

Ilinski, P.; Yun, W.; Lai, B.; Gluskin, E.; Cai, Z.

1994-09-01

240

Measurements of x-ray spectral flux of high brightness undulators by gas scattering  

SciTech Connect

Absolute radiation flux and polarization measurements of the Advanced Photon Source (APS) undulators may have to be made under high thermal loading conditions. A method that may circumvent the high-heat-load problem was tested during a recent APS/CHESS undulator run. The technique makes use of a Si(Li) energy-dispersive detector to measure 5--35 keV x rays scattered from a well-defined He gas volume at controlled pressure.

Ilinski, P.; Yun, W.; Lai, B.; Gluskin, E.; Cai, Z. (Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States))

1995-02-01

241

Design and performance of a tunable polarizer for VUV and soft x-ray spectral regions  

NASA Astrophysics Data System (ADS)

A low pass polarizer is presented for suppressing higher order diffraction light from vacuum ultraviolet and soft x-ray monochromators. By optimization of materials combination and angle of incidence, the polarizer demonstrates the capability to match to the desired photon energy cut-off. With the proposed hybrid polarizer, a higher order suppression unit, such as a thin film filter, gas filter or double reflecting mirror, is no longer required. The filtering effect of higher harmonics is integrated within the proposed polarizer.

Yang, Minghong

2007-10-01

242

Unsupervised classification of single-particle X-ray diffraction snapshots by spectral clustering  

NASA Astrophysics Data System (ADS)

Single-particle experiments using X-ray Free Electron Lasers produce more than 105 snapshots per hour, consisting of an admixture of blank shots (no particle intercepted), and exposures of one or more particles. Experimental data sets also often contain unintentional contamination with different species. We present an unsupervised method able to sort experimental snapshots without recourse to templates, specific noise models, or user-directed learning. The results show 90% agreement with manual classification.

Yoon, Chun Hong; Schwander, Peter; Abergel, Chantal; Andersson, Inger; Andreasson, Jakob; Aquila, Andrew; Bajt, Saša.; Barthelmess, Miriam; Barty, Anton; Bogan, Michael J.; Bostedt, Christoph; Bozek, John; Chapman, Henry N.; Claverie, Jean-Michel; Coppola, Nicola; Deponte, Daniel P.; Ekeberg, Tomas; Epp, Sascha W.; Erk, Benjamin; Fleckenstein, Holger; Foucar, Lutz; Graafsma, Heinz; Gumprecht, Lars; Hajdu, Janos; Hampton, Christina Y.; Hartmann, Andreas; Hartmann, Elisabeth; Hartmann, Robert; Hauser, Gunter; Hirsemann, Helmut; Holl, Peter; Kassemeyer, Stephan; Kimmel, Nils; Kiskinova, Maya; Liang, Mengning; Duane Loh, Ne-Te; Lomb, Lukas; Maia, Filipe R. N. C.; Martin, Andrew V.; Nass, Karol; Pedersoli, Emanuele; Reich, Christian; Rolles, Daniel; Rudek, Benedikt; Rudenko, Artem; Schlichting, Ilme; Schulz, Joachim; Seibert, Marvin; Seltzer, Virginie; Shoeman, Robert L.; Sierra, Raymond G.; Soltau, Heike; Starodub, Dmitri; Steinbrener, Jan; Stier, Gunter; Strüder, Lothar; Svenda, Martin; Ullrich, Joachim; Weidenspointner, Georg; White, Thomas A.; Wunderer, Cornelia; Ourmazd, Abbas

2011-08-01

243

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

Microsoft Academic Search

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

J. H. Siewerdsen; A. M. Waese; D. J. Moseley; S. Richard; D. A. Jaffray

2004-01-01

244

Comparing spectral models for ultraluminous X-ray sources with NGC 4517 ULX1  

NASA Astrophysics Data System (ADS)

We present the previously unanalysed high-quality XMM-Newton spectrum of an ultraluminous X-ray source (ULX) candidate in NGC 4517. As with other high-quality ULX spectra, a downturn in the spectrum is observed at ˜6 keV. Both of the recent disc reflection and Comptonization interpretations of this feature are applied, in order to present a direct comparison, and are found to provide statistically equivalent representations of the current data. We find that the reflection model requires the accretion disc to have a highly supersolar iron abundance, while the Comptonization model requires low-temperature Comptonizing electrons, and for the corona to be optically thick. These physical requirements are discussed in detail, and physically motivated scenarios are highlighted in which each model can be considered a viable explanation for the observed emission. By extending our consideration of these two interpretations to high energies, we demonstrate that observations of ULXs at energies ?10 keV should be extremely useful when attempting to distinguish between them. With current instrumentation, it is only viable to perform these observations for M82 X-1, but future high angular resolution hard X-ray imaging spectrometers, such as the Hard X-ray Imaging System due to fly on Astro-H, should go a long way to resolving this issue.

Walton, D. J.; Gladstone, J. C.; Roberts, T. P.; Fabian, A. C.; Caballero-Garcia, M. D.; Done, C.; Middleton, M. J.

2011-06-01

245

SPATIAL, TEMPORAL, AND SPECTRAL PROPERTIES OF X-RAY EMISSION FROM THE MAGNETAR SGR 0501+4516  

SciTech Connect

SGR 0501+4516 was discovered with the Swift satellite on 2008 August 22 after it emitted a series of very energetic bursts. Since then, the source was extensively monitored with Swift and the Rossi X-ray Timing Explorer (RXTE) and observed with Chandra and XMM-Newton, providing a wealth of information about its outburst behavior and burst-induced changes of its persistent X-ray emission. Here, we report the most accurate location of SGR 0501+4516 (with an accuracy of 0.''11) derived with Chandra. Using the combined RXTE, Swift/X-ray Telescope, Chandra, and XMM-Newton observations, we construct a phase-connected timing solution with the longest time baseline ({approx}240 days) to date for the source. We find that the pulse profile of the source is energy dependent and exhibits remarkable variations associated with the SGR 0501+4516 bursting activity. We also find significant spectral evolution (hardening) of the source persistent emission associated with bursts. Finally, we discuss the consequences of the SGR 0501+4516 proximity to the supernova remnant, SNR G160.9+2.6 (HB9).

Goegues, Ersin; Kaneko, Yuki [Sabanci University, Orhanli-Tuzla, Istanbul 34956 (Turkey); Woods, Peter M. [Corvid Technologies, 689 Discovery Drive, Huntsville, AL 35806 (United States); Kouveliotou, Chryssa [Space Science Office, VP-62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Gaensler, Bryan M. [Sydney Institute for Astronomy, School of Physics A29, University of Sydney, NSW 2006 (Australia); Chatterjee, Shami, E-mail: ersing@sabanciuniv.ed [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)

2010-10-10

246

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

SciTech Connect

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, approx.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 approx.10/sup 5/ K, and consequently these lines are weak or absent in solar spectra. The entire list contains approx.600 lines. Finally, predicted spectra of the two RS CVn stars, ..cap 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.

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

1984-09-01

247

Application of maximum-entropy spectral estimation to deconvolution of XPS data. [X-ray Photoelectron Spectroscopy  

NASA Technical Reports Server (NTRS)

A comparison is made between maximum-entropy spectral estimation and traditional methods of deconvolution used in electron spectroscopy. The maximum-entropy method is found to have higher resolution-enhancement capabilities and, if the broadening function is known, can be used with no adjustable parameters with a high degree of reliability. The method and its use in practice are briefly described, and a criterion is given for choosing the optimal order for the prediction filter based on the prediction-error power sequence. The method is demonstrated on a test case and applied to X-ray photoelectron spectra.

Vasquez, R. P.; Klein, J. D.; Barton, J. J.; Grunthaner, F. J.

1981-01-01

248

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

249

Exploring the Small Magellanic Cloud to the Faintest X-ray Fluxes: Source Catalog, Timing, and Spectral Analysis  

NASA Astrophysics Data System (ADS)

We present the results of a pair of 100 ks Chandra observations in the Small Magellanic Cloud (SMC) to survey high-mass X-ray binaries (HMXBs), stars, and low-mass X-ray binaries (LMXBs)/cataclysmic variables down to Lx = 4.3 × 1032 erg s-1. The two SMC Deep Fields (DFs) are located in the most active star-forming region of the bar, with Deep Field-1 positioned at the most pulsar-rich location identified from previous surveys. Two new pulsars were discovered in the outburst: CXOU J004929.7-731058 (P = 892 s), CXOU J005252.2-721715 (P = 326 s), and three new HMXB candidates were identified. Of the 15 Be-pulsars now known in the field, 13 were detected, with pulsations seen in 9 of them. Ephemerides demonstrate that 6 of the 10 pulsars known to exhibit regular outbursts were seen outside their periastron phase, and quiescent X-ray emission at LX = 1033-1034 erg s-1 is shown to be common. Comparison with ROSAT, ASCA, and XMM-Newton catalogs resulted in positive identification of several previously ambiguous sources. Bright optical counterparts exist for 40 of the X-ray sources, of which 33 are consistent with early-type stars (MV < -2, B - V < 0.2), and are the subject of a companion paper. The results point to an underlying HMXB population density up to double that of active systems. The full catalog of 394 point sources is presented along with detailed analyses of timing and spectral properties.

Laycock, Silas; Zezas, Andreas; Hong, Jaesub; Drake, Jeremy J.; Antoniou, Valsamo

2010-06-01

250

The 2005 Accretion Outburst in V1118 Ori: Evidence for A Spectral Change in X-rays  

NASA Astrophysics Data System (ADS)

We present results from our X-ray monitoring campaign of the 2005 accretion outburst in the young low-mass star V1118 Ori. Optical and near-infrared photometry are presented as well. The X-ray data from early 2005 indicate that the X-ray flux and luminosity varied within a factor of two only, and were similar to the pre-outburst values measured in a serendipitous observation in 2002. Similarly, the hydrogen column density showed no evidence for significant excursions from the pre-outburst value of a few times 1021 cm-2. However, we observed a spectral change from a dominant hot plasma ( ˜ 25 MK) in 2002 and in January 2005 to a cooler plasma ( ˜ 8 MK) in February and March 2005. We argue that the closing in of the accretion disk during the outburst disrupted the hot magnetic loops high in the corona, whereas the lower cooler loops were less affected and became the dominant coronal component. We acknowledge support by NASA through Chandra award DD5-6029X and through XMM-Newton award NNG05GI96G to Columbia University. The Chandra X-ray Observatory Center is operated by the Smithsonian Astrophysical Observatory for and on behalf of the NASA under contract NAS8-03060. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. The PSI group acknowledges support from the Swiss National Science Foundation (grants 20-58827.99 and 20-66875.01). Stony Brook's participation in SMARTS is made possible by support from the offices of the Provost and the Vice President for Research. We thank J. Allyn Smith, P. McGehee, J. Espinoza, and D. Gonzalez for doing the observations with the SMARTS telescopes. We also thank H. Tannanbaum, N. Schartel, and the VLA TOO panel for granting time to observe V1118 Ori.

Audard, M.; Güdel, M.; Skinner, S. L.; Briggs, K. R.; Walter, F. M.; Stringfellow, G.; Hamilton, R. T.; Guinan, E. F.

2005-12-01

251

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

252

X-ray spectral models of Galactic bulge sources - The emission-line factor  

NASA Technical Reports Server (NTRS)

Current difficulties in finding unique and physically meaningful models for the X-ray spectra of Galactic bulge sources are exacerbated by the presence of strong, variable emission and absorption features that are not resolved by the instruments observing them. Nine Einstein solid state spectrometer (SSS) observations of five Galactic bulge sources are presented for which relatively high resolution objective grating spectrometer (OGS) data have been published. It is found that in every case the goodness of fit of simple models to SSS data is greatly improved by adding line features identified in the OGS that cannot be resolved by the SSS but nevertheless strongly influence the spectra observed by SSS.

Vrtilek, S. D.; Swank, J. H.; Kallman, T. R.

1988-01-01

253

Mcps-range photon-counting x-ray computed tomography system  

NASA Astrophysics Data System (ADS)

10 Mcps photon counting was carried out using a detector consisting of a 2.0 mm-thick ZnO (zinc oxide) single-crystal scintillator and an MPPC (multipixel photon counter) module in an X-ray computed tomography (CT) system. The maximum count rate was 10 Mcps (mega counts per second) at a tube voltage of 70 kV and a tube current of 2.0 mA. Next, a photon-counting X-ray CT system consists of an X-ray generator, a turntable, a scan stage, a two-stage controller, the ZnO-MPPC detector, a counter card (CC), and a personal computer (PC). Tomography is accomplished by repeated linear scans and rotations of an object, and projection curves of the object are obtained by the linear scan with a scan velocity of 25 mm/s. The pulses of the event signal from the module are counted by the CC in conjunction with the PC. The exposure time for obtaining a tomogram was 600 s at a scan step of 0.5 mm and a rotation step of 1.0°, and photon-counting CT was accomplished using iodine-based contrast media.

Sato, Eiichi; Oda, Yasuyuki; Abudurexiti, Abulajiang; Hagiwara, Osahiko; Enomoto, Toshiyuki; Sugimura, Shigeaki; Endo, Haruyuki; Sato, Shigehiro; Ogawa, Akira; Onagawa, Jun

2011-09-01

254

X-ray spectral analysis of the low-luminosity active galactic nucleus NGC 7213 using long XMM-Newton observations  

NASA Astrophysics Data System (ADS)

We present the X-ray spectral results from the longest X-ray Multi-mirror Mission-Newton observation, 133 ks, of the low-luminosity active galactic nucleus NGC 7213. The hardness-ratio analysis of the X-ray light curves discloses a rather constant X-ray spectral shape, at least for the observed exposure time, enabling us to perform X-ray spectral studies using the total observed spectrum. Apart from a neutral Fe K? emission line, we also detect narrow emission lines from the ionized iron species, Fe XXV and Fe XXVI. Our analysis suggests that the neutral Fe K? originates from a Compton-thin reflector, while the gas responsible for the high-ionization lines is collisionally excited. The overall spectrum, in the 0.3-10 keV energy band, registered by the European Photon Imaging Camera can be modelled by a power-law component (with a slope of ? ? 1.9) plus two thermal components at 0.36 and 8.84 keV. The low-energy thermal component is entirely consistent with the X-ray spectral data obtained by the Reflection Grating Spectrometer between 0.35-1.8 keV.

Emmanoulopoulos, D.; Papadakis, I. E.; Nicastro, F.; McHardy, I. M.

2013-03-01

255

Optical constants for hard x-ray multilayers over the energy range E = 35 - 180 keV  

NASA Astrophysics Data System (ADS)

We have determined experimentally optical constants for eight thin film materials that can be used in hard X-ray multilayer coatings. Thin film samples of Ni.97V.03, Mo, W, Pt, C, B4C, Si and SiC were deposited by magnetron sputtering onto superpolished optical flats. Optical constants were determined from fits to reflectance-vs-incidence angle measurements made using synchrotron radiation over the energy range E=35 180 keV. We have also measured the X-ray reflectance of a prototype W/SiC multilayer coating over the energy range E=35 100 keV, and we compare the measured reflectance with a calculation using the newly derived optical constants.

Windt, David L.; Donguy, Soizik; Hailey, Charles J.; Koglin, Jason E.; Honkimaki, Veijo; Ziegler, Eric; Christensen, Finn E.; Harrison, Fiona A.

2004-02-01

256

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

257

Micro-X-ray spectral determination of iodine in alloys based on bismuth telluride  

SciTech Connect

The authors have developed a procedure for determining the iodine content in Bi/sub 2/Te/sub 3/ single crystals and solid solutions based on it with the help of an x-ray microanalyzer. The crystals were grown by Czochralski's method with the liquid phase fed from a floating crucible. the iodine was injected into the alloys in the form of the compound SbI/sub 3/. It is evident, according to the authors, that changing the iodine content from 0.08 to 0.12 mass % appreciably affects the electrophysical properties of the melt. The amount of iodine determined using the procedure developed corresponds well with its content in the starting charge.

Kul'bachevskaya, E.V.; Chizhevskaya, S.N.; Svechnikova, T.E.

1986-08-01

258

Spectral analysis of x-ray emission created by intense laser irradiation of copper materials.  

PubMed

We have measured the x-ray emission, primarily from K(?),K(?), and He(?) lines, of elemental copper foil and "foam" targets irradiated with a mid-10(16) W/cm(2) laser pulse. The copper foam at 0.1 times solid density is observed to produce 50% greater He(?) line emission than copper foil, and the measured signal is well-fit by a sum of three synthetic spectra generated by the atomic physics code FLYCHK. Additionally, spectra from both targets reveal characteristic inner shell K(?) transitions from hot electron interaction with the bulk copper. However, only the larger-volume foam target produced significant K(?) radiation, confirming a lower bulk temperature in the higher volume sample. PMID:23126936

Huntington, C M; Kuranz, C C; Malamud, G; Drake, R P; Park, H-S; Maddox, B R

2012-10-01

259

Spectral analysis of x-ray emission created by intense laser irradiation of copper materials  

SciTech Connect

We have measured the x-ray emission, primarily from K{sub {alpha}},K{sub {beta}}, and He{sub {alpha}} lines, of elemental copper foil and 'foam' targets irradiated with a mid-10{sup 16} W/cm{sup 2} laser pulse. The copper foam at 0.1 times solid density is observed to produce 50% greater He{sub {alpha}} line emission than copper foil, and the measured signal is well-fit by a sum of three synthetic spectra generated by the atomic physics code FLYCHK. Additionally, spectra from both targets reveal characteristic inner shell K{sub {alpha}} transitions from hot electron interaction with the bulk copper. However, only the larger-volume foam target produced significant K{sub {beta}} radiation, confirming a lower bulk temperature in the higher volume sample.

Huntington, C. M.; Kuranz, C. C.; Drake, R. P. [Atmospheric, Oceanic, Space Science, University of Michigan, Ann Arbor, Michigan 48103 (United States); Malamud, G. [Atmospheric, Oceanic, Space Science, University of Michigan, Ann Arbor, Michigan 48103 (United States); Department of Physics, Nuclear Research Center - Negev, 84190 Beer-Sheva (Israel); Park, H.-S.; Maddox, B. R. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2012-10-15

260

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

261

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

262

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: High spectral and spatial resolution of monochromatic x-ray shadowgraphy of an expanding laser plasma  

NASA Astrophysics Data System (ADS)

A focusing spectrograph with a spherical crystal was used to obtain two-dimensional images of an expanding laser plasma which transmitted monochromatic x-ray radiation from a plasma source. Experiments characterised by a high spectral (?/?? ~ 104) and spatial (?r < 10 ?m) resolution showed that the brightness of the shadow images depended on the x-ray absorption mechanism and on the parameters of the investigated plasma. The method is suitable, in principle, for determination of the plasma parameters.

Dyakin, V. M.; Magunov, A. I.; Pikuz, T. A.; Skobelev, I. Yu; Faenov, A. Ya

1997-01-01

263

On the Nature of the mHz X-Ray QPOs from ULX M82 X-1: Evidence for Timing-Spectral (anti) Correlation  

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 energy spectral power-law index. These quantities are known to correlate in stellar mass black holes (StMBHs) exhibiting Type-C QPOs (approx 0.2-15 Hz). The detection of such a correlation would strengthen the identification of its 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 of M82 X-1 and a nearby bright ULX (source 5/X42.3+59) through surface brightness modeling and identify observations in which M82 X-1 was at least as bright as source 5. Using only those observations, we detect QPOs in the frequency range of 36-210 mHz during which the energy spectral power-law index varied from 1.7-2.2. Interestingly, we find evidence for an anti-correlation (Pearsons correlation coefficient = -0.95) between the power-law index and the QPO centroid frequency. While such an anti-correlation is observed in StMBHs at high Type-C QPO frequencies (approx 5-15 Hz), the frequency range over which it holds in StMBHs is significantly smaller (factor of approx 1.5-3) than the QPO range reported here from M82 X-1 (factor of 6). However, it remains possible that contamination from source 5 can bias our result. Joint Chandra/XMM-Newton observations in the future can resolve this problem and confirm the timing-spectral anti-correlation reported here.

Pasham, Dheeraj R.; Strohmayer, Tod E.

2013-01-01

264

High Quality x-ray absorption spectrosocopy measuements with long energy range at high pressure using diamond anvil cell  

SciTech Connect

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{sup o} relative to the x-ray beam direction. Demonstration XAFS spectra are reported for rutile-type GeO{sub 2} recorded by traditional ambient pressure and high pressure DAC methods, showing similar quality at 440 eV above the absorption edge. Accurate XAFS spectra of GeO{sub 2} glass were obtained at high pressure up to 53 GPa, providing important insight into the structural polymorphism of GeO{sub 2} glass at high pressure. This method is expected be applicable for in situ XAFS measurements using a diamond anvil cell up to ultrahigh pressures.

Hong, X.; Newville, M.; Prakapenka, V.; Rivers, M.; Sutton, S.

2009-07-29

265

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

SciTech Connect

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{sup o} relative to the x-ray beam direction. Demonstration XAFS spectra are reported for rutile-type GeO{sub 2} recorded by traditional ambient pressure and high pressure DAC methods, showing similar quality at 440 eV above the absorption edge. Accurate XAFS spectra of GeO{sub 2} glass were obtained at high pressure up to 53 GPa, providing important insight into the structural polymorphism of GeO{sub 2} glass at high pressure. This method is expected be applicable for in situ XAFS measurements using a diamond anvil cell up to ultrahigh pressures.

Hong, X.; Newville, M.; Prakapenka, V.B.; Rivers, M.L.; Sutton, S.R.; (Cornell CHESS); (UC)

2009-07-31

266

Characterizing the Evolving X-Ray Spectral Features during a Superburst from 4U 1636-536  

NASA Astrophysics Data System (ADS)

Recent studies have shown that runaway thermonuclear burning of material accreted onto neutron stars, i.e., Type I X-ray bursts, may affect the accretion disk. We investigate this by performing a detailed time-resolved spectral analysis of the superburst from 4U 1636-536 observed in 2001 with the Rossi X-Ray Timing Explorer. Superbursts are attributed to the thermonuclear burning of carbon, and are approximately 1000 times more energetic than the regular short Type I bursts. This allows us to study detailed spectra for over 11 ks, compared to, at most, 100 s for regular bursts. A feature is present in the superburst spectra around 6.4 keV that is well fit with an emission line and an absorption edge, suggestive of reflection of the superburst off the accretion disk. The line and edge parameters evolve over time: the edge energy decreases from 9.4 keV at the peak to 8.1 keV in the tail, and both features become weaker in the tail. This is only the second superburst for which this has been detected and shows that this behavior is present even without strong radius expansion. Furthermore, we find the persistent flux more than doubles during the superburst and returns to the pre-superburst value in the tail. The combination of reflection features and increased persistent emission indicates that the superburst had a strong impact on the inner accretion disk and it emphasizes that X-ray bursts provide a unique probe of accretion physics.

Keek, L.; Ballantyne, D. R.; Kuulkers, E.; Strohmayer, T. E.

2014-07-01

267

Properties of X ray emission from X ray novae  

NASA Astrophysics Data System (ADS)

Some properties of x ray novae, considered to contain a black hole are described. 71% of the black hole candidates belong to x ray novae. From the spectral study of these novae, at the rising phase, the appearance of hard x rays beyond 100 keV is found. The origin of these hard x rays is described. The probability that a black hole candidate is an x ray nova is shown. The observation of a component comptonized by hot electrons around the soft x ray peak indicates the existence of nonthermal energetic phenomena at the early phase of the nova activity. A model including jet phenomena is discussed.

Kitamoto, Shunji

1993-05-01

268

The physical origin of the X-ray power spectral density break timescale in accreting black holes  

NASA Astrophysics Data System (ADS)

X-ray variability of active galactic nuclei (AGN) and black hole binaries can be analysed by means of the power spectral density (PSD). The break observed in the power spectrum defines a characteristic variability timescale of the accreting system. The empirical variability scaling that relates characteristic timescale, black hole mass, and accretion rate (TB ? M_BH2.1/dot{M0.98}) extends from supermassive black holes in AGN down to stellar-mass black holes in binary systems. We suggest that the PSD break timescale is associated with the cooling timescale of electrons in the Comptonisation process at the origin of the observed hard X-ray emission. We find that the Compton cooling timescale directly leads to the observational scaling and naturally reproduces the functional dependence on black hole mass and accretion rate (tC ? M_BH2/dot{M}). This result simply arises from general properties of the emission mechanism and is independent of the details of any specific accretion model.

Ishibashi, W.; Courvoisier, T. J.-L.

2012-04-01

269

The COUP Abundance Study: Spectral analysis of the X-ray brightest late-type stars in Orion  

NASA Astrophysics Data System (ADS)

We present preliminary results of a detailed X-ray spectral analysis of 55 sources in the Chandra Orion Ultra-deep field, identified with late-type stars and having more that 10^4 extracted counts. The aim of this analysis is to provide a census of element abundances in the coronae of these young stars, and to study possible dependences of such abundances on the magnetic activity level, the presence of circumstellar disks, indicators of accretion, and the properties of the local environment. We present here the methodology of such an analysis and results related to the thermal structure of the selected sources, their global metallicity, and abundance determinations for some individual elements. In particular, we show that the COUP X-ray bright sources tend to be metal poor (Fe abundances less than half the solar one, with most frequent values of 0.1-0.2 solar), while they show a larger scatter of Ne abundances, and Ne/Fe ratios from ˜1 up to ˜10.

Maggio, Antonio; Flaccomio, E.; Micela, G.; Sciortino, S.; Favata, F.; Feigelson, E. D.

2005-07-01

270

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

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

2014-06-01

271

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

272

A Broad-band Spectral and Timing Study of the X-Ray Binary System Centaurus X-3  

NASA Technical Reports Server (NTRS)

This dissertation describes a multi-mission investigation of the high mass X-ray binary pulsar Centaurus X-3. Cen X-3 was observed with the Broad Band X-Ray Telescope (BBXRT) in December 1990. This was the first high-resolution solid state X-ray spectrometer to cover the iron K fluorescence region. The Fe K emission feature was resolved into two components for the first time. A broad 6.7 keV feature was found to be a blend of lines from Fe XXI-Fe XXVI with energies ranging from 6.6 to 6.9 keV due to photoionization of the companion's stellar wind. A narrow line at 6.4 keV due to fluorescence of iron in relatively low ionization states was also found. The quasi-periodic oscillations (QPO) at about 40 mHz were used to estimate the surface magnetic field of Cen X-3 as approx. 2.6 x 10(exp 12) G and to predict that there should be a cyclotron scattering resonance absorption feature (CSRF) near 30 keV. In order to further resolve the iron line complex and to investigate the pulse-phase dependence of the iron line intensities, Cen X-3 was observed with the Advanced Satellite for Cosmology and Astrophysics (ASCA). Using ASCA's state-of-the-art non-dispersive X-ray spectrometers the 6.4 keV fluorescent iron line was found to be pulsing while the intensities of the 6.7 and 6.9 keV recombination lines do not vary with pulse phase. This confirms that the 6.4 keV line is due to reflection by relatively neutral matter close to the neutron star while the recombination lines originate in the extended stellar wind. The continuum spectrum was found to be modified by reflection from matter close to the neutron star. Observations with the EXOSAT GSPC were used to search for a CSRF. The EXOSAT spectra were consistent with the presence of a CSRF but an unambiguous detection was not possible because of a lack of sensitivity at energies higher than the cyclotron energy. Cen X-3 was then observed with the Rossi X-Ray Timing Explorer (RXTE) and evidence for a CSRF at 25.1 +/- 0.3 keV was found. This corresponds to a magnetic field of (2.16 +/- 0.03) X 10(exp 12) G and is consistent with the value obtained from the QPO analysis.

Audley, Michael Damian

1998-01-01

273

Miocrowave spectral imaging, H-alpha and hard X-ray observations of a solar limb flare  

NASA Astrophysics Data System (ADS)

We compare the microwave, H-alpha, and hard X-ray observations for a west limb C7.3 flare that occurred at 17:10 UT, 1992 June 26. H-alpha movies were obtained at Big Bear Solar Observatory. Before the onset of the flare, overexposed H-alpha images show the complicated flux loop structure above the limb. Material was observed to descend along the loops toward the site where the flare occurred hours later. Using the five-antenna solar array at Owens Valley Radio Observatory, we obtain two-dimensional maps of flare emission from 1.4 to 14 GHz. In all three temporal peaks of the microwave bursts, the maps show the same characteristics. The peak low-frequency emission comes from the top of one bundle of the H-alpha loops and gradually shifts to the foot-point of the loops (the location of H-alpha flare) as the frequency increases. The location of the emission peak shifts 88 sec between 1 and 14 GHz. Seventy percent of the shift occurs between 1 and 5 GHz. The locus of the shift of the emission peak follows the shape of an H-alpha surge that occurred after the flare. For each point along the locus, we create the microwave brightness temperature spectrum and compare the radio-derived electron distribution with that derived from the high-resolution hard X-ray spectra measured with Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory (CGRO). We find that the peak frequency changes from approximately 3 GHz at the loop top to approximately 7 GHz at the footprint, presumably due to the increase of the magnetic field from approximately 160 GHz at the loop top to approximately 300 G at the footpoint. The high-frequency slope of the microwave power-law spectrum decreases from approximately 10 at the loop top to approximately 5 at the footprint due to a change in the energy distribution of the dominant electrons. The microwave brightness temperature spectral index predicted by the BATSE power-law hard X-ray spectra agrees with the measured value only at the footpoint. At the loop top, the emission may be thermal gyrosynchrotron with a temperature of 3.5 x 107 K, which is likely to correspond to the superhot component seen in the hard X-ray emission.

Wang, H.; Gary, D. E.; Lim, J.; Schwartz, R. A.

1994-09-01

274

Miocrowave spectral imaging, H-alpha and hard X-ray observations of a solar limb flare  

NASA Technical Reports Server (NTRS)

We compare the microwave, H-alpha, and hard X-ray observations for a west limb C7.3 flare that occurred at 17:10 UT, 1992 June 26. H-alpha movies were obtained at Big Bear Solar Observatory. Before the onset of the flare, overexposed H-alpha images show the complicated flux loop structure above the limb. Material was observed to descend along the loops toward the site where the flare occurred hours later. Using the five-antenna solar array at Owens Valley Radio Observatory, we obtain two-dimensional maps of flare emission from 1.4 to 14 GHz. In all three temporal peaks of the microwave bursts, the maps show the same characteristics. The peak low-frequency emission comes from the top of one bundle of the H-alpha loops and gradually shifts to the foot-point of the loops (the location of H-alpha flare) as the frequency increases. The location of the emission peak shifts 88 sec between 1 and 14 GHz. Seventy percent of the shift occurs between 1 and 5 GHz. The locus of the shift of the emission peak follows the shape of an H-alpha surge that occurred after the flare. For each point along the locus, we create the microwave brightness temperature spectrum and compare the radio-derived electron distribution with that derived from the high-resolution hard X-ray spectra measured with Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory (CGRO). We find that the peak frequency changes from approximately 3 GHz at the loop top to approximately 7 GHz at the footprint, presumably due to the increase of the magnetic field from approximately 160 GHz at the loop top to approximately 300 G at the footpoint. The high-frequency slope of the microwave power-law spectrum decreases from approximately 10 at the loop top to approximately 5 at the footprint due to a change in the energy distribution of the dominant electrons. The microwave brightness temperature spectral index predicted by the BATSE power-law hard X-ray spectra agrees with the measured value only at the footpoint. At the loop top, the emission may be thermal gyrosynchrotron with a temperature of 3.5 x 10(exp 7) K, which is likely to correspond to the superhot component seen in the hard X-ray emission.

Wang, H.; Gary, D. E.; Lim, J.; Schwartz, R. A.

1994-01-01

275

X-ray attenuation coefficients and photoelectric cross sections of Cu, Fe and Sn for the energy range 3-29 KeV.  

National Technical Information Service (NTIS)

The document contains the following two papers: X-ray attenuation coefficient and photoelectric cross sections of Sn for the Energy Range 3.3 KeV to 29.1 KeV - by Wang Dachun, Yang Hua and Luo Pingan. X-ray attenuation coefficients and photoelectric cross...

Wang Dachun Yang Hua Luo Pingan Ding Xunliang Wang Xinfu

1991-01-01

276

Soft X-ray laser cavities  

Microsoft Academic Search

We report progress in the development of multilayer components for use in multiple pass soft X-ray laser cavities operating in the 100A to 300A spectral range. Our work includes fabrication and characterization of multilayer components; simple resonant cavity design; damage threshold assessment for multilayers in the X-ray laser environment; and multipass cavity experiments for efficiency enhancement and transverse mode selection.

N. M. Ceglio; D. G. Stearns; A. M. Hawryluk; T. M. Barbee; K. Danzmann; M. Kuehne; P. Mueller; B. Wende; M. B. Stearns; A. K. Petford-Long; C.-H. CHANG

1986-01-01

277

Soft x-ray laser cavities  

SciTech Connect

We report progress in the development of multilayer components for use in multiple pass soft x-ray laser cavities operating in the 100A to 300A spectral range. Our work includes fabrication and characterization of multilayer components; simple resonant cavity design; damage threshold assessment for multilayers in the x-ray laser environment; and multipass cavity experiments for efficiency enhancement and transverse mode selection. 14 refs., 9 figs.

Ceglio, N.M.; Stearns, D.G.; Hawryluk, A.M.; Barbee, T.M.; Danzmann, K.; Kuehne, M.; Mueller, P.; Wende, B.; Stearns, M.B.; Petford-Long, A.K.

1986-07-08

278

Is M82 X-1 Really an Intermediate-Mass Black Hole? X-Ray Spectral and Timing Evidence  

NASA Technical Reports Server (NTRS)

Ultraluminous X-ray sources (ULXs) with apparent luminosities up to hundreds 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 (quasi-periodic oscillation [QPO]) properties of the X-radiation from this source. We revisited XMM-Newton and Rossi X-Ray Timing Explorer (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 nu approx. = 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 black hole mass of M82 X-1. The method uses the index-QPO low-frequency correlation that has been recently established in Galactic black hole candidates GRS 1915+105, XTE JI550-564, 4U 1630-47, and others. Using scaling arguments and the correlation derived from the consideration of Galactic black holes, we conclude that M82 X-1 is an intermediate black hole with a mass of the order of 1000 solar mass,.

Fiorito, Ralph; Titarchuk, Lev

2004-01-01

279

Structure investigation, spectral, thermal, X-ray and mass characterization of piroxicam and its metal complexes  

NASA Astrophysics Data System (ADS)

[M(H 2L) 2](A) 2. yH 2O (where H 2L: neutral piroxicam (Pir), A: Cl - in case of Ni(II) or acetate anion in case of Cu(II) and Zn(II) ions and y=0-2.5) and [M(H 2L) 3](A) z. yH 2O (A: SO 42- in case of Fe(II) ion ( z=1) or Cl - in case of Fe(III) ( z=3) and Co(II) ions ( z=2) and y=1-4) chelates are prepared and characterized using elemental analyses, IR, magnetic and electronic reflectance measurements, mass spectra and thermal analyses. IR spectra reveal that Pir behaves a neutral bidentate ligand coordinated to the metal ions through the pyridyl-N and carbonyl-O of the amide moiety. The reflectance and magnetic moment measurements reveal that these chelates have tetrahedral, square planar and octahedral geometrical structures. Mass spectra and thermal analyses are also used to confirm the proposed formulae and the possible fragments resulted from fragmentation of Pir and its chelates. The thermal behaviour of the chelates (TGA and DTA) are discussed in detail and the thermal stability of the anhydrous chelates follow the order Ni(II)?Cu(II)X-ray powder diffraction was also used as a confirmatory tool to elucidate the crystallinity of the chelates.

Zayed, M. A.; Nour El-Dien, F. A.; Mohamed, Gehad G.; El-Gamel, Nadia E. A.

2004-10-01

280

Low temperature X-ray molecular structure, tautomerism and spectral properties of 2,3-dihydroxyquinoxaline  

NASA Astrophysics Data System (ADS)

The solid state molecular structure of 2,3-dihydroxyquinoxaline (DHQ) has been studied using X-ray single crystallography. The equilibrium geometry of six possible DHQ isomers have been calculated using the B3LYP/6-311++G(d,p) method in order to predict the most stable gas-phase isomer. The effect of solvent polarity on the relative stability of these isomers is assessed at the same level of theory using PCM. In agreement with the experimental results, it was found that keto form, DHQ1, is the most stable isomer both in the gaseous state and solution. The scaled harmonic vibrational frequencies are in good agreement with the experimental data. The effect of solvent on the vibrational frequencies of the DHQ1 tautomer showed a bathochromic shift for the ?(Cdbnd O) and ?(Nsbnd H) bands. These shifts increase with the polarity of the solvent. The electronic transitions of the most stable isomer DHQ1 were calculated using TDDFT and the NMR chemical shifts were calculated using the GIAO method. The NLO properties are predicted to be greater than urea by a factor of five. Two stable dimer forms of DHQ were calculated at same level of theory. Dimer A is more stable by 13.38 kcal mol-1 than dimer B. The former is stabilized by stronger Nsbnd H⋯O H-bonds compared to the weaker Csbnd H⋯O interactions in the latter. The effect of these H-bonding interactions on the molecular structure and vibrational spectra of these compounds are predicted.

Soliman, Saied M.; Albering, Jörg; Abu-Youssef, Morsy A. M.

2013-12-01

281

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

282

Refractive microlens array for wave-front analysis in the medium to hard x-ray range  

NASA Astrophysics Data System (ADS)

We report an alternative approach to x-ray wave-front analysis that uses a refractive microlens array as a Shack-Hartmann sensor. The sensor was manufactured by self-assembly and electroplating techniques and is suitable for high-resolution wave-front analysis of medium to hard x rays. We demonstrate its effectiveness at an x-ray energy of 3 keV for analysis of x-ray wave-front perturbations caused by microscopic objects. The sensor has potential advantages over other methods for x-ray phase imaging and will also be useful for the characterization of x-ray beams and optics.

Mayo, Sheridan C.; Sexton, Brett

2004-04-01

283

Increased power, pulse length, and spectral purity free-electron laser for inverse-Compton X-ray production and laser induced breakdown spectroscopy of thin film photovoltaics  

NASA Astrophysics Data System (ADS)

The free-electron laser (FEL) system can be configured to produce X-ray or extreme ultraviolet (EUV) light via Compton backscattering and to perform many types of spectroscopy including laser induced breakdown spectroscopy (LIBS). In it's most common incarnation, the FEL is limited by three major factors: average laser power, laser spectral purity, and laser pulse length. Some examples of the limitations that these shortcomings give rise to include limiting the range of remote spectroscopy, degrading spectroscopic precision, and lowering the attainable x-ray flux, respectively. In this work, we explored three methods of improving the FEL. First, a beam expanding optic dubbed the TIRBBE was designed, built, and tested to prevent laser damage to the resonator mirrors and allow for higher average power. This optic had the added benefit of increasing the spectral purity. Second, a intra-cavity etalon filter dubbed the FROZEN FISH was designed, built, and tested to increase spectral purity and eliminate the frequency pulling (tendency of an FEL to pull towards longer wavelengths during a macropulse) all in a high damage threshold, fully wavelength adjustable package. Finally, a laser cooling scheme which allows for extension of the electron beam macropulse used to create the FEL light by counter-acting electron back-heating was explored. The first measurements of the back-heating temperature rise were taken, calculations of the required laser parameters were made, design of the full system was completed, and construction has begun. Experimental work using LIBS to characterize thin film solar cells was also completed in anticipation of using the improved FEL to better characterize such materials. The frequency tunability and picosecond micropulse width of the FEL will allow for exploration of the frequency response of LIBS ablation and fine resolution of the make up of these materials with depth unattainable with a conventional fixed frequency nanosecond pulse laser.

Kowalczyk, Jeremy M.

284

Novel parallel vacuum ultra-violet/X-ray fluorescence spectrometer  

NASA Astrophysics Data System (ADS)

Novel instrumentation developments in X-ray spectroscopy for parallel spectral measurements with soft X-rays are described. The significant performance improvements are achieved utilising Fresnel diffraction from structures built onto the surface of a total external reflection mirror. An array of reflection zone plates was tested as a wavelength-dispersive fluorescence spectrometer for soft X-rays in the energy range of 100-550 eV.

Erko, A.; Firsov, A.; Senf, F.

2012-01-01

285

Computer simulations and models for the performance characteristics of spectrally equivalent X-ray beams in medical diagnostic radiology  

PubMed Central

In order to achieve uniformity in radiological imaging, it is recommended that the concept of equivalence in shape (quality) and size (quantity) of clinical Xray beams should be used for carrying out the comparative evaluation of image and patient dose. When used under the same irradiation geometry, X-ray beams that are strictly or relatively equivalent in terms of shape and size will produce identical or relatively identical image quality and patient dose. Simple mathematical models and software program EQSPECT.FOR were developed for the comparative evaluation of the performance characteristics in terms of contrast (C), contrast to noise ratio (CNR) and figure-of-merit (FOM = CNR2/DOSE) for spectrally equivalent beams transmitted through filter materials referred to as conventional and k-edged. At the same value of operating potential (kVp), results show that spectrally equivalent beam transmitted through conventional filter with higher atomic number (Z-value) in comparison with that transmitted through conventional filter with lower Z-value resulted in the same value of C and FOM. However, in comparison with the spectrally equivalent beam transmitted through filter of lower Z-value, the beam through filter of higher Z-value produced higher value of CNR and DOSE at equal tube loading (mAs) and kVp. Under the condition of equivalence of spectrum, at scaled (or reduced) tube loading and same kVp, filter materials of higher Z-value can produce the same values of C, CNR, DOSE and FOM as filter materials of lower Z-value. Unlike the case of comparison of spectrally equivalent beam transmitted through one conventional filter and that through another conventional filter, it is not possible to derive simple mathematical formulations for the relative performance of spectrally equivalent beam transmitted through a given conventional filter material and that through kedge filter material.

Okunade, Akintunde A.

2007-01-01

286

Multi-Spectral Solar Telescope Array. IV - The soft X-ray and extreme ultraviolet filters  

NASA Technical Reports Server (NTRS)

NASA's Multi-Spectral Solar Telescope Array uses various combinations of thin foil filters composed of Al, C, Te, Be, Mo, Rh, and phthalocyanine to achieve the requisite radiation-rejection characteristics. Such rejection is demanded by the presence of strong EUV radiation at longer wavelengths where the specular reflectivity of multilayer mirrors can cause 'contamination' of the image in the narrow band defined by the Bragg condition.

Lindblom, Joakim F.; O'Neal, Ray H.; Walker, Arthur B. C., Jr.; Powell, Forbes R.; Barbee, Troy W., Jr.; Hoover, Richard B.

1991-01-01

287

Calibration of X-ray detectors in the 8 to 115 keV energy range and their application to diagnostics on the National Ignition Facility  

SciTech Connect

The calibration of X-ray diagnostics is of paramount importance to the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). National Security Technologies LLC (NSTec) fills this need by providing a wide variety of calibration and diagnostic development services in support of the ongoing research efforts at NIF. The X-ray source in the High Energy X-ray lab utilizes induced fluorescence in a variety of metal foils to produce a beam of characteristic X rays ranging from 8 to 111 keV. Presented are the methods used for calibrating a High Purity Germanium detector, which has been absolutely calibrated using radioactive check sources, compared against a silicon photodiode calibrated at Physikalisch Technische Bundesanstalt (PTB). Also included is a limited presentation of results from the recent calibration of the upgraded Filter Fluorescer X ray Spectrometer.

J. J. Lee, M. J. Haugh, G. LaCaille, and P. Torres

2012-10-01

288

Spectral separation of the efficiencies of the inside and outside orders of soft-x-ray-extreme-ultraviolet gratings at near normal incidence  

SciTech Connect

It is shown from both a phenomenological study and exact modeling that the reason for the experimentally observed substantial (a few angstroms or nanometers) separation in wavelength between the maxima of the inside (negative numbered) and outside (positive numbered) diffraction orders of a multilayer-coated grating, operating at near normal incidence and close to the Bragg condition in the soft-x-ray and extreme-ultraviolet (EUV) regions, is related to the different angles of deviation of the orders. This wavelength separation is also a feature of uncoated diffraction gratings, although not clearly noticeable. The widely used approximate approach for calculating the absolute efficiency, the product of the relative grating efficiency and the reflectance of its multilayer coating, has until recently been considered accurate enough for the analysis of soft-x-ray and EUV near-normal-incidence multilayer-coated gratings. The inapplicability of this approximation for the analysis of the precise positions and shapes of the efficiency curves for the inside and outside orders, despite the small ratios of wavelength and groove depth to period and the small angles of incidence, is demonstrated using gratings with realistic groove profiles and operating in the EUV region. The rigorous modified integral method (MIM), which is a variant of boundary integral equation methods and is designed for the calculation of the efficiency of multilayer gratings with arbitrary layer thicknesses and boundary shapes (including microroughness) and over a wide wavelength range, is proposed in a general operator formalism. An analysis of a derived simple phenomenological expression and the exact numerical study indicates that the spectral separation between the inside and the outside orders grows with increasing either wavelength, angle of incidence, groove frequency, or diffraction order number |m|. The efficiency modeling carried out with the commercial program PCGRATE-SX, based on the MIM, gave not only the exact values of the spectral separation between the inside and outside orders of Mo{sub 4}Ru{sub 6}/Be, Mo/Si, and Mo/Y multilayer-coated gratings with various real groove profiles measured using atomic force microscopy (AFM) but also good agreement with synchrotron radiation measurements, including high orders as well. To determine the shapes and positions of efficiency curves in the soft-x-ray-EUV range of close to normal-incidence bulk and multilayer-coated gratings with real groove profiles (measured by AFM), one should use codes based on rigorous electromagnetic theory such as the MIM. The modeling is important for developing high efficiency and dispersion gratings for high-resolution spectroscopic studies of laboratory, solar, and astrophysical radiation sources.

Goray, Leonid I.; Seely, John F.; Sadov, Sergey Yu. [International Intellectual Group, Inc., P.O. Box 335, Penfield, New York 14526 and Institute for Analytical Instrumentation, Russian Academy of Sciences, Rizhsky Prospect 26, Saint-Petersburg 190103 (Russian Federation); Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland A1C 5S7 (Canada)

2006-11-01

289

Accounting for Calibration Uncertainties in X-ray Analysis: Effective Areas in Spectral Fitting  

NASA Astrophysics Data System (ADS)

While considerable advance has been made to account for statistical uncertainties in astronomical analyses, systematic instrumental uncertainties have been generally ignored. This can be crucial to a proper interpretation of analysis results because instrumental calibration uncertainty is a form of systematic uncertainty. Ignoring it can underestimate error bars and introduce bias into the fitted values of model parameters. Accounting for such uncertainties currently requires extensive case-specific simulations if using existing analysis packages. Here, we present general statistical methods that incorporate calibration uncertainties into spectral analysis of high-energy data. We first present a method based on multiple imputation that can be applied with any fitting method, but is necessarily approximate. We then describe a more exact Bayesian approach that works in conjunction with a Markov chain Monte Carlo based fitting. We explore methods for improving computational efficiency, and in particular detail a method of summarizing calibration uncertainties with a principal component analysis of samples of plausible calibration files. This method is implemented using recently codified Chandra effective area uncertainties for low-resolution spectral analysis and is verified using both simulated and actual Chandra data. Our procedure for incorporating effective area uncertainty is easily generalized to other types of calibration uncertainties.

Lee, Hyunsook; Kashyap, Vinay L.; van Dyk, David A.; Connors, Alanna; Drake, Jeremy J.; Izem, Rima; Meng, Xiao-Li; Min, Shandong; Park, Taeyoung; Ratzlaff, Pete; Siemiginowska, Aneta; Zezas, Andreas

2011-04-01

290

ACCOUNTING FOR CALIBRATION UNCERTAINTIES IN X-RAY ANALYSIS: EFFECTIVE AREAS IN SPECTRAL FITTING  

SciTech Connect

While considerable advance has been made to account for statistical uncertainties in astronomical analyses, systematic instrumental uncertainties have been generally ignored. This can be crucial to a proper interpretation of analysis results because instrumental calibration uncertainty is a form of systematic uncertainty. Ignoring it can underestimate error bars and introduce bias into the fitted values of model parameters. Accounting for such uncertainties currently requires extensive case-specific simulations if using existing analysis packages. Here, we present general statistical methods that incorporate calibration uncertainties into spectral analysis of high-energy data. We first present a method based on multiple imputation that can be applied with any fitting method, but is necessarily approximate. We then describe a more exact Bayesian approach that works in conjunction with a Markov chain Monte Carlo based fitting. We explore methods for improving computational efficiency, and in particular detail a method of summarizing calibration uncertainties with a principal component analysis of samples of plausible calibration files. This method is implemented using recently codified Chandra effective area uncertainties for low-resolution spectral analysis and is verified using both simulated and actual Chandra data. Our procedure for incorporating effective area uncertainty is easily generalized to other types of calibration uncertainties.

Lee, Hyunsook; Kashyap, Vinay L.; Drake, Jeremy J.; Ratzlaff, Pete; Siemiginowska, Aneta, E-mail: hlee@cfa.harvard.edu, E-mail: vkashyap@cfa.harvard.edu, E-mail: jdrake@cfa.harvard.edu, E-mail: rpete@head.cfa.harvard.edu, E-mail: asiemiginowska@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

2011-04-20

291

Spectral Evolution of the Black Hole X-ray Binary XTE J1752-223 Observed with MAXI  

NASA Astrophysics Data System (ADS)

The MAXI/GSC observed the black hole candidate XTE J1752-223 in the 2009-2010 outburst from the onset to the end. From the GSC light curve, it spent about three months to enter the high/soft state (HSS) through two plateau phases in the rising part of the outburst. The source definitely lies in the extreme low/hard state (LHS) during the first plateau period, and in the intermediate state just after the second plateau period, which was confirmed by RXTE, but spectral properties during the second plateau period (from the beginning of the December 2009 to mid-January 2010) were not well investigated due to the solar avoidance limitation of many X-ray satellites. Only the MAXI/GSC and Swift/BAT could this interesting phase, so we performed a broadband spectral analysis of the entire outburst using a combination of MAXI-GSC and Swift-BAT survey data. In this paper, we will report on the entire outburst behavior, and will discuss the difference between the first and second plateau phase from both observational and theoretical points of view.

Nakahira, Satoshi; Yamaoka, Kazutaka; Negoro, Hitoshi; Ueda, Yoshihiro; Maxi Team

2010-12-01

292

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.

Iwamoto, Hiroyuki; Inoue, Katsuaki; Yagi, Naoto

2005-01-01

293

Selection and suppression of soft x-ray spectral features using optimized multilayer coatings  

NASA Astrophysics Data System (ADS)

The design of multilayer mirrors which specifically select or suppress spectral features is described. To illustrate the method, the spectra from laser-produced plasmas of carbon and aluminium are used. By using a suitable mirror the intensity of the C V He? line at ? = 4.03 nm can be reduced to 1.1×10-4 of that in the C VI Ly? line at ? = 3.37 nm, compared to 0.97 in the source emission spectrum and 1.6×10-2 for a periodic multilayer. In the aluminium spectrum, two closely spaced lines at ? = 3.505 and 3.660 nm, which have comparable emitted intensities, can be individually selected using pairs of multilayers. The reflected intensity ratios are under ten for periodic multilayers, but can be over 300 for the shorter wavelength line and almost 140 for the longer using optimized pairs of mirrors.

Michette, A. G.; Wang, Z.

2001-01-01

294

X-ray and optical observations of X-ray-selected BL Laceratae objects  

NASA Technical Reports Server (NTRS)

Results from several X-ray and optical observations of five X-ray-selected BL Lacertae objects are reported. X-ray light curves covering periods of up to 6 yr reveal that the X-ray flux from these objects does not show large-amplitude trends over this time scale. Variations of up to 2 mag have been observed in the optical. The soft X-ray spectra of three objects have been measured with the Exosat Medium Energy detectors. Energy spectral indices range between one and two. In one case (1E 1415.6 + 2557), evidence for photoelectric absorption in excess of that due to the local interstellar medium has been found. A new optical flare from 1E 1402.3 + 0416, with rise and decay time of order of a few weeks, has been detected.

Giommi, P.; Barr, P.; Garilli, B.; Gioia, I. M.; Maccacaro, T.

1987-01-01

295

X-RAY SPECTRAL VARIATIONS IN THE YOUNGEST GALACTIC SUPERNOVA REMNANT G1.9+0.3  

SciTech Connect

The discovery of the youngest Galactic supernova remnant (SNR) G1.9+0.3 has allowed a look at a stage of SNR evolution never before observed. We analyze the 50 ks Chandra observation with particular regard to spectral variations. The very high column density (N{sub H} {approx} 6 x 10{sup 22} cm{sup -2}) implies that dust scattering is important, and we use a simple scattering model in our spectral analysis. The integrated X-ray spectrum of G1.9+0.3 is well described by synchrotron emission from a power-law electron distribution with an exponential cutoff. Using our measured radio flux and including scattering effects, we find a rolloff frequency of 5.4(3.0, 10.2) x 10{sup 17} Hz (h{nu}{sub roll} = 2.2 keV). Including scattering in a two-region model gives lower values of {nu}{sub roll} by over a factor of 2. Dividing G1.9+0.3 into six regions, we find a systematic pattern in which spectra are hardest (highest {nu}{sub roll}) in the bright southeast and northwest limbs of the shell. They steepen as one moves around the shell or into the interior. The extensions beyond the bright parts of the shell have the hardest spectra of all. We interpret the results in terms of dependence of shock acceleration properties on the obliquity angle {theta}{sub Bn} between the shock velocity and a fairly uniform upstream magnetic field. This interpretation probably requires a Type Ia event. If electron acceleration is limited by synchrotron losses, the spectral variations require obliquity-dependence of the acceleration rate independent of the magnetic-field strength.

Reynolds, Stephen P.; Borkowski, Kazimierz J. [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States); Green, David A. [Cavendish Laboratory, 19 J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Hwang, Una; Harrus, Ilana; Petre, Robert [NASA/GSFC, Code 660, Greenbelt, MD 20771 (United States)], E-mail: stephen_reynolds@ncsu.edu

2009-04-20

296

Observations of solar X-ray bursts in the energy range 5-15 keV  

NASA Technical Reports Server (NTRS)

Bursts of solar X-rays in the energy range 5-15 keV are associated with flares and are due to thermal emission from a hot coronal plasma. The results of the first study of a large sample of separate bursts, 197 events associated with subflares, and of a few events of importance 1 are presented. The observations were made by a proportional counter on the satellite OSO-7 from October, 1971 to June, 1972. In most cases, the temperature characterizing the X-ray spectrum rises impulsively at the onset of the burst and then declines slowly throughout the remainder of the burst. The emission measure rises exponentially with a time scale of 30-100 sec and then declines slowly on a time scale of the order of 1,000 sec. It is shown that the growth of the thermal energy in the flare plasma throughout the burst can be due to the heating of new cool material.

Datlowe, D. W.; Hudson, H. S.; Peterson, L. E.

1974-01-01

297

Microwave and hard X-ray imaging of a solar flare on 1980 November 5  

Microsoft Academic Search

An analysis is given of the flare of 1980 November 5 at 22:26 UT on the basis of radio imaging data from the Very Large Array (VLA) at 15 GHz, X-ray imaging data from the hard X-ray imaging spectrometer (HXIS) in the range 3.5--30 keV, radio and X-ray spectral data, and optical data. The flare produced two impulsive hard X-ray

P. Hoyng; K. A. Marsh; H. Zirin; B. R. Dennis

1983-01-01

298

The complex X ray spectra of AGN  

NASA Technical Reports Server (NTRS)

X-ray spectral surveys of large samples of Seyfert galaxies are discussed. The spectral shape in the 0.1 to 20 keV energy range is considered. Two new spectral survey are undertaken, one involving 105 Imaging Proportional Counter (IPC) observations of 75 Seyfert galaxies, the other using IPC and Monitor Proportional Counter (MPC) data from 28 observations of 23 Seyfert galaxies. The X-ray spectra of active galactic nuclei (AGN) are complex, with in most cases considerable steepening at the lowest energies. At higher energies (2 to 20 keV), the existence of a universal, canonical power law is confirmed, independent of X-ray luminosity over four orders of magnitude.

Urry, C. M.; Arnaud, Keith; Edelson, R. A.; Kruper, J. S.; Mushotzky, R. F.

1989-01-01

299

A Multi-Epoch Timing and Spectral Study of the Ultraluminous X-Ray NGC 5408 X-1 with XMM-Newton  

NASA Technical Reports Server (NTRS)

We present results of new XMM-Newton observations of the ultraluminous X-ray source (ULX) NGC 5408 X-1, one of the few ULXs to show quasi-periodic oscillations (QPOs). We detect QPOs in each of four new (approximately equal to 100 ks) pointings, expanding the range of frequencies observed from 10 to 40 mHz. We compare our results with the timing and spectral correlations seen in stellar-mass black hole systems, and find that the qualitative nature of the timing and spectral behavior of NGC 5408 X-1 is similar to systems in the steep power-law state exhibiting Type-C QPOs. However, in order for this analogy to quantitatively hold we must only be seeing the so-called saturated portion of the QPO frequency-photon index (or disk flux) relation. Assuming this to be the case, we place a lower limit on the mass of NGC 5408 X-1 of greater than or equal to 800 solar mass. Alternatively, the QPO frequency is largely independent of the spectral parameters, in which case a close analogy with the Type-C QPOs in stellar system is problematic. Measurement of the source's timing properties over a wider range of energy spectral index is needed to definitively resolve this ambiguity. We searched all the available data for both a broad Fe emission line as well as high-frequency QPO analogs (0.1- 1 Hz), but detected neither. We place upper limits on the equivalent width of any Fe emission feature in the 6-7 keV band and of the amplitude (rms) of a high-frequency QPO analog of approximately equal to 10 eV and approximately equal to 4%, respectively.

Dheeraj, Pasham; Strohmayer, Tod E.

2012-01-01

300

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

301

The Spectral Analysis of X-Ray Binaries from the XMM-Newton Space Craft Data using SAS Software  

NASA Astrophysics Data System (ADS)

A spectral data analysis on a luminous object of sky-coordinates 12h52m24.28s-29d115'02.3'12.6arcsec using Science Analysis Software (SAS) is presented. The analysis, based on data acquired by the Reflection Grating Spectrometer (RGS) camera aboard the XMM-Newton Space satellite, shows that the primary constituents of the X-ray source are Fe (Iron) and O (oxygen). This suggests that the source may be a magnetized plasma in a binary system and as this magnetic field accelerates the cooling of a star, one may speculate that this may be a compact star in its last stages of a thermonuclear fusion process. Nous présentons une analyse du spectre d'une source a rayons X située -- en coordonnées sidérales - à 12h52m24.28s - 29d115'02.312.6 arcsec. Science Analysis Software (SAS) est le programme informatique utilisé pour l'analyse des données. Cette analyse est basée sur les données provenant du spectromètre à haute résolution (RGS) à bord du satellite spatiale XMM-Newton. Nous montrons que ladite source est principalement constituée de Fer (Fe) et d'oxygene (O). Ce résultat suggère que la source pourrait être un plasma magnétisé au sein d'un système binaire. Et du fait que ce champ magnétique accélère le refroidissement de l'étoile, nous supposons que cette étoile pourrait ètre un objet compact en phase terminale d'un processus de fusion thermonucléaire.

Baki, P.; Mito, C. O.

2009-10-01

302

Development of a soft x-ray diffractometer for a wideband multilayer grating with a novel layer structure in the 2-4 keV range  

SciTech Connect

We have been developing a wavelength-dispersive soft x-ray spectrograph covering an energy region of 50-4000 eV to attach to a conventional electron microscope. Observation of soft x-ray emission in the 2-4 keV range needs a multilayer coated grating. In order to evaluate the performance of the optical component in the energy region, a goniometric apparatus has been newly developed and the preliminary performance has been tested using synchrotron radiation.

Imazono, Takashi; Koike, Masato; Kawachi, Tetsuya; Hasegawa, Noboru; Koeda, Masaru; Nagano, Tetsuya; Sasai, Hiroyuki; Oue, Yuki; Yonezawa, Zeno; Kuramoto, Satoshi; Terauchi, Masami; Takahashi, Hideyuki; Handa, Nobuo; Murano, Takanori [Quantum Beam Science Directorate, Japan Atomic Energy Agency, 8-1-7 Umemidai, Kizugawa, Kyoto 619-0215 (Japan); Device Dept., Shimadzu Corp., 1 Nishinokyo-Kuwabara-cho, Nakagyo-ku, Kyoto 604-8511 (Japan); IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); ECBU, JEOL Ltd., 3-1-2 Musashino, Akishima, Tokyo 196-8558 (Japan)

2012-07-11

303

Absolute detection efficiency of a micro-channel plate detector to x-rays in the 1--100 KeV energy range  

Microsoft Academic Search

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional unaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front

G. A. Burginyon; B. A. Jacoby; J. K. Wobser; R. D. Ernst; D. S. Ancheta; K. G. Tirsell

1992-01-01

304

Absolute detection efficiency of a microchannel plate detector to X rays in the 1-100 KeV energy range  

Microsoft Academic Search

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional imaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front

Gary A. Burginyon; Barry A. Jacoby; James K. Wobser; Richard Ernst; Dione S. Ancheta; Kenneth G. Tirsell

1993-01-01

305

Absolute detection efficiency of a micro-channel plate detector to X-rays in the 1 - 100 keV energy range  

Microsoft Academic Search

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high X-ray energies. The authors have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional imaging X-ray detector in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of

G. A. Burginyon; B. A. Jacoby; J. K. Wobser; R. D. Ernst; D. S. Ancheta; K. G. Tirsell

1993-01-01

306

X-ray spectral microanalysis of composition of individual lunar regolith particles  

NASA Technical Reports Server (NTRS)

Determinations were made of the chemical compositions of selected olivine crystals, spherical particles ranging in size from 170 to 350 micrometer, spinels, and magnetic particles. The olivines contain 30 to 50 mole percent fayalite. The spherical particles of various colors are aluminosilicate glasses, significantly enriched in CaO compared with the mean composition of the regolith. The degree of coloration depends on the FeO content and also the admixtures TiO2, MnO, and Cr2O3. Compositionally, the spinel was interpreted to be chromopicotites. Magnetic particles were shown to be complex intergrowths of nickelous iron and aluminosilicates. The composition of the metallic phase of one particle (in percent) was: Fe - 86, Ni - 13.6, and Co - 0.16 in combination with plagioclase and microinclusions of ilmenite in silicate. Kamacite was determined in another intergrowth of Fe, Ni, and Co.

Ilin, N. P.; Loseva, L. Y.; Senin, V. G.

1974-01-01

307

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

308

Calibrating of x-ray detectors in the 8 to 111 keV energy range and their application to diagnostics on the National Ignition Facility  

NASA Astrophysics Data System (ADS)

The calibration of X-ray diagnostics is of paramount importance to the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL). National Security Technologies LLC (NSTec) fills this need by providing a wide variety of calibration and diagnostic development services in support of the ongoing research efforts at NIF. The Xray source in the High Energy X-ray lab utilizes induced fluorescence in a variety of metal foils to produce a beam of characteristic X-rays ranging from 8 to 111 keV. Presented are the methods used for calibrating a High Purity Germanium detector, using NIST traceable radioactive sources, and compared against a silicon photodiode calibrated at Physikalisch Technische Bundesanstalt (PTB). A limited presentation of results from the recent calibration of the upgraded Filter Fluorescer X-ray Spectrometer is included.

Lee, Joshua J.; Haugh, Michael J.; LaCaille, Greg; Torres, Peter

2012-10-01

309

Exploring the Full Range of Properties of Quasar Spectral Distributions  

NASA Technical Reports Server (NTRS)

The aim of this work is to support our ISO, far-infrared (IR) observing program of quasars and active galaxies. We have obtained, as far as possible, complete spectral energy distributions (radio-X-ray) of the ISO sample in order to fully delineate the continuum shapes and to allow detailed modelling of that continuum. This includes: ground-based optical, near-IR and mm data, the spectral ranges closest to the ISO data, within 1-2 years of the ISO observations themselves. ISO was launched in Nov 1995 and is currently observing routinely. It has an estimated lifetime is 2 years. All near-IR and optical imaging and spectroscopy are now in hand and in the process of being reduced, mm data collection and proposal writing continues.

Wilkes, B.

1998-01-01

310

Feedback at the Working Surface: A Joint X-ray and Low-Frequency Radio Spectral Study of the Cocoon Shock in Cygnus A  

NASA Astrophysics Data System (ADS)

We report on preliminary results from a joint spectral analysis of the cocoon shock region in Cygnus A using deep archival Chandra data and new low-frequency radio data from LOFAR. Being both bright in X-rays and the most powerful radio source in the local universe, the FRII radio galaxy Cygnus A represents an ideal opportunity to study the interaction between the jets produced by the central AGN and the surrounding intracluster medium (ICM) in which that AGN is embedded. Using the entire 235 ksec archival Chandra exposure, we have performed a spatially resolved, X-ray spectral analysis of the ICM in Cygnus A. By combining the resulting X-ray images and temperature maps with spectral index maps between 30-80 MHz and 120-180 MHz calculated from a recent, deep LOFAR observation, we can resolve the X-ray and radio emitting plasmas in any given region on spatial scales of 3-4 kpc over the central 100 kpc. We clearly resolve the cocoon shock surrounding Cygnus A and determine the Mach number of the shock as a function of position angle. Temperature jumps associated with this shock are detected over a large fraction of the total shock circumference. Significant non-thermal emission is also detected in the regions surrounding the SE and NW leading edges of the shock near the hotspots. In this talk, we will present a detailed analysis of the energetics of this interface region between the radio plasma inside the cocoon shock and the X-ray emitting gas outside the shock. Inside the shock, we will present constraints on the emission mechanisms in the jet, counter-jet, and hotspots based on the combined radio and X-ray spectra. Using maps of the spectral age derived from the LOFAR data and independent age estimates based on various cavity features seen in the X-ray image, we will present a picture of the evolution of the shock region in Cygnus A over the past 50 Myr. Finally, we will discuss the implications these observations have for AGN feedback models as well as the energy transfer mechanism itself.

Wise, Michael W.; Rafferty, D. A.; McKean, J. P.

2013-04-01

311

CO-ANALYSIS OF SOLAR MICROWAVE AND HARD X-RAY SPECTRAL EVOLUTIONS. II. IN THREE SOURCES OF A FLARING LOOP  

SciTech Connect

Based on the spatially resolvable data of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Nobeyama Radio Heliograph (NoRH), co-analysis of solar hard X-ray and microwave spectral evolution is performed in three separate sources located in one looptop (LT) and two footpoints (FPs) of a huge flaring loop in the 2003 October 24 flare. The RHESSI image spectral evolution in 10-100 keV is always fitted by the well-known soft-hard-soft (SHS) pattern in the three sources. When the total energy is divided into four intervals similar to the Yohkoh/Hard X-ray Telescope, i.e., 12.5-32.5 keV, 32.5-52.5 keV, 52.5-72.5 keV, and 72.5-97.5 keV, the SHS pattern in lower energies is converted gradually to the hard-soft-hard (HSH) pattern in higher energies in all three sources. However, the break energy in the LT and the northeast FP ({approx}32.5 keV) is evidently smaller than that in the southwest FP ({approx}72.5 keV). Regarding microwave spectral evolution of the NoRH data, the well-known soft-hard-harder pattern appeared in the southwest FP, while the HSH pattern coexisted in the LT and the northeast FP. The different features of the hard X-ray and microwave spectral evolutions in the three sources may be explained by the loop-loop interaction with another huge loop in the LT and with a compact loop in the northeast FP, where the trapping effect is much stronger than that in the southwest FP. The comparison between the LT and FP spectral indices suggests that the radiation mechanism of X-rays may be quite different in different energy intervals and sources. The calculated electron spectral indices from the predicted mechanisms of X-rays gradually become closer to those from the microwave data with increasing X-ray energies.

Huang Guangli; Li Jianping, E-mail: glhuang@pmo.ac.cn, E-mail: jpli@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2011-10-10

312

Comprehensive Monitoring of Gamma-Ray Bright Blazars. I. Statistical Study of Optical, X-Ray, and Gamma-Ray Spectral Slopes  

NASA Astrophysics Data System (ADS)

We present ?-ray, X-ray, ultraviolet, optical, and near-infrared light curves of 33 ?-ray bright blazars over 4 years that we have been monitoring since 2008 August with multiple optical, ground-based telescopes and the Swift satellite, and augmented by data from the Fermi Gamma-ray Space Telescope and other publicly available data from Swift. The sample consists of 21 flat-spectrum radio quasars (FSRQs) and 12 BL Lac objects (BL Lacs). We identify quiescent and active states of the sources based on their ?-ray behavior. We derive ?-ray, X-ray, and optical spectral indices, ??, ? X , and ? o , respectively (F ?vprop??), and construct spectral energy distributions during quiescent and active states. We analyze the relationships between different spectral indices, blazar classes, and activity states. We find (1) significantly steeper ?-ray spectra of FSRQs than for BL Lacs during quiescent states, but a flattening of the spectra for FSRQs during active states while the BL Lacs show no significant change; (2) a small difference of ? X within each class between states, with BL Lac X-ray spectra significantly steeper than in FSRQs; (3) a highly peaked distribution of X-ray spectral slopes of FSRQs at ~ –0.60, but a very broad distribution of ? X of BL Lacs during active states; (4) flattening of the optical spectra of FSRQs during quiescent states, but no statistically significant change of ? o of BL Lacs between states; and (5) a positive correlation between optical and ?-ray spectral slopes of BL Lacs, with similar values of the slopes. We discuss the findings with respect to the relative prominence of different components of high-energy and optical emission as the flux state changes.

Williamson, Karen E.; Jorstad, Svetlana G.; Marscher, Alan P.; Larionov, Valeri M.; Smith, Paul S.; Agudo, Iván; Arkharov, Arkady A.; Blinov, Dmitry A.; Casadio, Carolina; Efimova, Natalia V.; Gómez, José L.; Hagen-Thorn, Vladimir A.; Joshi, Manasvita; Konstantinova, Tatiana S.; Kopatskaya, Evgenia N.; Larionova, Elena G.; Larionova, Liudmilla V.; Malmrose, Michael P.; McHardy, Ian M.; Molina, Sol N.; Morozova, Daria A.; Schmidt, Gary D.; Taylor, Brian W.; Troitsky, Ivan S.

2014-07-01

313

Aperiodic variability and broad band spectral properties of the X-ray burster GS1826-24  

NASA Astrophysics Data System (ADS)

GS1826-24, discovered by GINGA in September 1988, was first classified as a black hole candidate, because of its hard spectrum and extreme rapid variability in X-rays. However, on the basis of its low X-ray and hard X-ray luminosities, it was later hypothesized that the compact object in GS1826-24 could be a neutron star. Recently SAX observed type I X-ray bursts from GS1826-24, thus excluding its black hole nature, and confirming the neutron star hypothesis. GS1826-24 was observed by RXTE for about 40 ksec on November 5th and 6th, 1997. In this paper, we present results from the study of both its aperiodic variability and its broad band (2-200 keV) energy spectrum.

Boirin, L.; Barret, D.; Olive, J.-F.; Grindlay, J. E.

1998-12-01

314

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

315

Application of the Monte Carlo codes PENELOPE and MCNP5 to unfold X-ray spectra in the diagnostic energy range  

NASA Astrophysics Data System (ADS)

Obtaining primary X-ray spectra is a complex task, mainly due to the high fluence of X-rays. In order to avoid the pile up effect in the detector, an indirect method based on the Compton scattering interactions in a low density rod material can be successfully applied in the diagnostic energy range. In this work, the Monte Carlo codes PENELOPE and MCNP5 have been used to simulate the indirect method based on a simplified Compton spectrometry technique. Both models include the X-ray focus, a poly(mehtylmethacrylate) (PMMA) rod and an HPGe detector. Because the probability that primary photons scattered in the PMMA will be emitted towards the detector is small, it is necessary to consider appropriate values for cut-offs and other simulation parameters. With these models, a response function can be determined, relating the response of the detector to the primary X-ray spectrum. This function can be normally expressed as a matrix, which can be calculated by simulating the response detector to several monochromatic X-ray beams. The main goal of this work is to test the capability of the Monte Carlo codes PENELOPE and MCNP5, together with unfolding methods to estimate the primary spectrum when the response matrix and the response of the detector for a given conditions are known. The reliability of unfolded X-ray spectra is studied by comparing them with theoretical spectra obtained from the IPEM 78 catalog and calculating the Root Mean Squared (RMS) and Quality parameters.

Gallardo, Sergio; Querol, Andrea; Pozuelo, Fausto; Verdú, Gumersindo; Ródenas, José

2014-02-01

316

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

Microsoft Academic Search

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

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

1997-01-01

317

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

Microsoft Academic Search

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{sup +} 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

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

1997-01-01

318

X-Rays from Accelerated Ion Interactions  

NASA Astrophysics Data System (ADS)

We have developed in detail the theory of X-ray line and continuum production due to atomic interactions of accelerated ions, incorporating in our calculations information from a broad range of laboratory measurements. We applied our calculations to the Orion region from which nuclear gamma-ray line observations with the COMPTEL instrument on the Compton Gamma Ray Observatory (CGRO) were reported. The accelerated particles which produce this gamma-ray emission via nuclear reactions also produce X-ray lines via atomic interactions. We predict strong, relatively broad line emission in the range from 0.5 to 1 keV, mainly due to de-excitations in fast O ions. Current ROSAT observations of Orion do not provide unambiguous signatures for X-ray production by accelerated ions. However, if future X-ray observations with high spectral resolution would confirm the predicted X-rays, the combined analysis of the X-ray and gamma-ray data will set important constraints on the origin of the accelerated particles and their interaction model.

Tatischeff, Vincent; Ramaty, Reuven; Kozlovsky, Benzion

1998-09-01

319

Tunable, short pulse hard x rays from a compact laser synchrotron source  

Microsoft Academic Search

The development of a compact, tunable, near monochromatic hard x-ray source would have profound and wide ranging applications in a number of areas. These areas include x ray diagnostics, medical imaging, microscopy, nuclear resonance absorption, solid-state physics and material sciences. The properties of the x-ray beam which are important for these applications include spectral width, spectral brightness, photon flux, pulse

Phillip Sprangle; Antonio Ting; Eric Esarey; Amnon Fisher

1992-01-01

320

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

321

Spectral variability in hard X-rays and evidence for 13.5 years period in bright quasar 3C273  

NASA Astrophysics Data System (ADS)

We report the observation of nearest quasar 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 power law spectral index alpha=2.26 +- 0.07. This is in complete contrast to the reported data from OSSE and BeppoSAX which suggest the value of 1.3 to 1.6 for the power law index in the X-ray energy band, but is quite consistent with the value derived for the high energy gamma ray data. A single power law fit in the X-ray and gamma ray energy bands points to a common origin of these photons and the absence of spectral break around 1 MeV as suggested in literature. We have reanalyzed the available data to study the temporal variability of the spectrum in the hard X-ray band. Our analysis reveals that 50 keV flux from the source, shows a strong modulation with a period of about 13.5 years. The analysis of the optical light curve of the source also supports the 5000 day period. We discuss the emission mechanism and the possible sites for X-ray photons along with the implications of the long term periodicity with respect to source geometry.

Manchanda, R. K.

2002-12-01

322

Emission lines from X ray binaries  

NASA Technical Reports Server (NTRS)

Emission lines are probes of the conditions in the accretion flows associated with binary X-ray sources. The hard X-ray iron K line, soft X-ray lines, and UV lines, and what they indicate about the conditions in binary X-ray sources are discussed. These lines are interpreted using an X-ray illuminated accretion disk model. The structure and dynamics of the heated disk, its spectral signatures, and the major unsolved theoretical issues surrounding them are investigated.

Kallman, T. R.

1989-01-01

323

Long-term spectral and timing properties of the soft gamma-ray repeater SGR 1833-0832 and detection of extended X-ray emission around the radio pulsar PSR B1830-08  

Microsoft Academic Search

SGR 1833-0832 was discovered on 2010 March 19, thanks to the Swift detection of a short hard X-ray burst and follow-up X-ray observations. Since then, it was repeatedly observed with Swift, Rossi X-ray Timing Explorer and XMM-Newton. Using these data, which span about 225 d, we studied the long-term spectral and timing characteristics of SGR 1833-0832. We found evidence for

P. Esposito; G. L. Israel; R. Turolla; F. Mattana; A. Tiengo; A. Possenti; S. Zane; N. Rea; M. Burgay; D. Götz; S. Mereghetti; L. Stella; M. H. Wieringa; J. M. Sarkissian; T. Enoto; P. Romano; T. Sakamoto; Y. E. Nakagawa; K. Makishima; K. Nakazawa; H. Nishioka; C. François-Martin

2011-01-01

324

Design of an ultrahigh-energy-resolution and wide-energy-range soft X-ray beamline.  

PubMed

A new ultrahigh-energy-resolution and wide-energy-range soft X-ray beamline has been designed and is under construction at the Shanghai Synchrotron Radiation Facility. The beamline has two branches: one dedicated to angle-resolved photoemission spectroscopy (ARPES) and the other to photoelectron emission microscopy (PEEM). The two branches share the same plane-grating monochromator, which is equipped with four variable-line-spacing gratings and covers the 20-2000?eV energy range. Two elliptically polarized undulators are employed to provide photons with variable polarization, linear in every inclination and circular. The expected energy resolution is approximately 10?meV at 1000?eV with a flux of more than 3 × 10(10)?photons?s(-1) at the ARPES sample positions. The refocusing of both branches is based on Kirkpatrick-Baez pairs. The expected spot sizes when using a 10?µm exit slit are 15?µm × 5?µm (horizontal × vertical FWHM) at the ARPES station and 10?µm × 5?µm (horizontal × vertical FWHM) at the PEEM station. The use of plane optical elements upstream of the exit slit, a variable-line-spacing grating and a pre-mirror in the monochromator that allows the influence of the thermal deformation to be eliminated are essential for achieving the ultrahigh-energy resolution. PMID:24365949

Xue, L; Reininger, R; Wu, Y-Q; Zou, Y; Xu, Z-M; Shi, Y-B; Dong, J; Ding, H; Sun, J-L; Guo, F-Z; Wang, Y; Tai, R-Z

2014-01-01

325

Comparison of thermo-luminescent detectors and X-ray vacuum detectors for measurement of X-ray yield from gold plasma produced by a sub-nanosecond Nd:glass laser  

NASA Astrophysics Data System (ADS)

Measurement of X-ray flux from laser-produced plasmas has always been important for several applications of the laser-plasma X-ray source. A CaSO 4:Dy thermo-luminescent dosimeter (TLD) in powder form has been used in experiments reported in this paper to measure absolute X-ray yield from a gold laser plasma in a spectral region of 0.7-10 keV. The results are compared with indigenously developed X-ray vacuum photodiodes (XVPD). The TLD is a simple and accurate diagnostics for the X-ray measurements in a wide (few eV up to MeV) X-ray spectral region. It is extremely sensitive, capable of measuring an X-ray dose as low as ?Gy and also has a dynamic range of almost 10 6, which is several orders of magnitude higher compared to the XVPD. Therefore, TLD is very well suited for integrated X-ray measurements from laser plasmas. Multi-channel arrays of TLD and XVPD are used with various X-ray filters to cover the desired spectral range. A comparative measurement was also carried out between X-ray yield from laser-produced plasma and a conventional X-ray generator operated at low voltage. It was observed that the X-ray dose in laser-produced plasma is almost 10 9 orders higher than the conventional X-ray generator.

Chaurasia, S.; Kumar, Munish; Poswal, A. K.; Munda, D. S.; Dhareshwar, L. J.; Kher, R. K.; Chourasiya, G.

2008-10-01

326

Certain Results of X-Ray Spectral Investigation of the Chemical Bond in Variable-Composition (Ti-TiO(0.48) Titanium Oxides.  

National Technical Information Service (NTIS)

The structure of x-ray absorption and emission of Ti in the lower oxides in a specific composition was investigated under analogous experimental conditions; in this composition range, a continuous series of solid solutions of O in alpha Ti exists. The gen...

E. E. Vainshtein V. I. Chirkov S. M. Blokhin

1969-01-01

327

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

328

Spectral and Timing Properties of the Black Hole X-Ray Binary H1743–322 in the Low/Hard State Studied with Suzaku  

NASA Astrophysics Data System (ADS)

We report on the results from Suzaku observations of the Galactic black hole X-ray binary H1743–322 in the low/hard state during its outburst in 2012 October. We appropriately take into account the effects of dust scattering to accurately analyze the X-ray spectra. The time-averaged spectra in the 1-200 keV band are dominated by a hard power-law component of a photon index of ?1.6 with a high-energy cutoff at ?60 keV, which is well described with the Comptonization of the disk emission by the hot corona. We estimate the inner disk radius from the multi-color disk component, and find that it is 1.3-2.3 times larger than the radius in the high/soft state. This suggests that the standard disk was not extended to the innermost stable circular orbit. A reflection component from the disk is detected with R = ?/2? ? 0.6 (? is the solid angle). We also successfully estimate the stable disk component independent of the time-averaged spectral modeling by analyzing short-term spectral variability on a ~1 s timescale. A weak low-frequency quasi-periodic oscillation at 0.1-0.2 Hz is detected, whose frequency is found to correlate with the X-ray luminosity and photon index. This result may be explained by the evolution of the disk truncation radius.

Shidatsu, M.; Ueda, Y.; Yamada, S.; Done, C.; Hori, T.; Yamaoka, K.; Kubota, A.; Nagayama, T.; Moritani, Y.

2014-07-01

329

Characterization of thin film CCD filters on board the German astronomy satellite ABRIXAS by soft x-ray transmission measurements  

Microsoft Academic Search

We have developed optical filters for the German X-ray astronomy satellite ABRIXAS (A BRoadband Imaging X-ray All Sky Survey)(1). Specific CCD's (2) will be used as detectors in the focal plane on board the observatory. Since these detectors are sensitive from the X-ray to the near infrared spectral range, X-ray observations require optical filters, which combine high transmittance for photon

K.-H. Stephan; H. Braeuninger; F. Haberl; P. Predehl; H. J. Maier; J. Friedrich; D. Schmitz; F. Scholze; G. Ulm

1999-01-01

330

Absolute detection efficiency of a micro-channel plate detector to x-rays in the 1--100 KeV energy range  

SciTech Connect

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional unaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of the MCP (optimized for Ni K[sub [alpha

Burginyon, G.A.; Jacoby, B.A.; Wobser, J.K.; Ernst, R.D.; Ancheta, D.S.; Tirsell, K.G.

1992-09-03

331

Reduction in the intensity of solar X-ray emission in the 2- to 15-keV photon energy range and heating of the solar corona  

SciTech Connect

The time profiles of the energy spectra of low-intensity flares and the structure of the thermal background of the soft X-ray component of solar corona emission over the period of January-February, 2003, are investigated using the data of the RHESSI project. A reduction in the intensity of X-ray emission of the solar flares and the corona thermal background in the 2- to 15-keV photon energy range is revealed. The RHESSI data are compared with the data from the Interball-Geotail project. A new mechanism of solar corona heating is proposed on the basis of the results obtained.

Mirzoeva, I. K., E-mail: colombo2006@mail.ru [Russian Academy of Sciences, Space Research Institute (Russian Federation)

2013-04-15

332

Imaging X-ray detector front-end with high dynamic range: IDeF-X HD  

NASA Astrophysics Data System (ADS)

Presented circuit, IDeF-X HD (Imaging Detector Front-end) is a member of the IDeF-X ASICs family for space applications. It has been optimized for a half millimeter pitch CdTe or CdZnTe pixelated detector arranged in 16×16 array. It is aimed to operate in the hard X-ray range from few keV up to 250 keV or more. The ASIC has been realized in AMS 0.35 ?m CMOS process. The IDeF-X HD is a 32 channel analog front-end with self-triggering capability. The architecture of the analog channel includes a chain of charge sensitive amplifier with continuous reset system and non-stationary noise suppressor, adjustable gain stage, pole-zero cancellation stage, adjustable shaping time low pass filter, baseline holder and peak detector with discriminator. The power consumption of the IDeF-X HD is 800 ?W per channel. With the in-channel variable gain stage the nominal 250 keV dynamic range of the ASIC can be extended up to 1 MeV anticipating future applications using thick sensors. Measuring the noise performance without a detector at the input with minimized leakage current (programmable) at the input, we achieved ENC of 33 electrons rms at 10.7 ?s peak time. Measurements with CdTe detector show good energy resolution FWHM of 1.1 keV at 60 keV and 4.3 keV at 662 keV with detection threshold below 4 keV. In addition, an absolute temperature sensor has been integrated with resolution of 1.5 °C.

Gevin, O.; Lemaire, O.; Lugiez, F.; Michalowska, A.; Baron, P.; Limousin, O.; Delagnes, E.

2012-12-01

333

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

334

Application of Tikhonov and MTSVD methods to unfold experimental X-ray spectra in the radiodiagnostic energy range.  

PubMed

A thorough knowledge of the primary spectrum is very important for Quality Control (QC) of X-ray tubes. A methodology to assess primary spectrum using a Compton spectrometer has been simulated with the MCNP5 code based on the Monte Carlo (MC) method. The Pulse Height Distribution (PHD) recorded in the detector is related with the primary X-ray spectrum by means of a Response matrix. Tikhonov and Modified Truncated Singular Values Decomposition (MTSVD) unfolding methods have been applied to the Response matrix to assess the primary spectrum. Both methods are tested comparing unfolded results with theoretical spectra from IPEM-78 catalogue. PMID:21095662

Querol, A; Gallardo, S; Rodenas, J; Verdu, G

2010-01-01

335

Hard X-Ray Emission of X-Ray Bursters  

NASA Technical Reports Server (NTRS)

The primary goal of this proposal was to perform an accurate measurement of the broadband x-ray spectrum of a neutron-star low-mass x-ray binary found in a hard x-ray state. This goal was accomplished using data obtained under another proposal, which has provided exciting new information on the hard x-ray emission of neutron-star low-mass x-ray binaries. In "BeppoSAX Observations of the Atoll X-Ray Binary 4U0614+091", we present our analysis of the spectrum of 4U0614+091 over the energy band from 0.3-150 keV. Our data confirm the presence of a hard x-ray tail that can be modeled as thermal Comptonization of low-energy photons on electrons having a very high temperature, greater than 220 keV, or as a non-thermal powerlaw. Such a very hard x-ray spectrum has not been previously seen from neutron-star low-mass x-ray binaries. We also detected a spectral feature that can be interpreted as reprocessing, via Compton reflection, of the direct emission by an optically-thick disk and found a correlation between the photon index of the power-law tail and the fraction of radiation reflected which is similar to the correlation found for black hole candidate x-ray binaries and Seyfert galaxies. A secondary goal was to measure the timing properties of the x-ray emission from neutronstar low-mass x-ray binaries in their low/hard states.

Kaaret, P.

1999-01-01

336

Absolute detection efficiency of a micro-channel plate detector to x-rays in the 1--100 KeV energy range  

SciTech Connect

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional unaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of the MCP (optimized for Ni K{sub {alpha}} (x-rays)) to convert x-rays to electrons, an MCP to amplify the electrons, and a fast In:CdS phosphor that converts the electron`s kinetic energy to light. The phosphor is coated on fiber-optic faceplate to transmit the light out of the vacuum system. Electrostatic focusing electrodes compress the electron current out of the MCP in one dimension while preserving spatial resolution in the other. The calibration geometry, dictated by a recent experiment, required grazing incidence x-rays (15.6{degree}) onto the MCP detector in order to maximize deliverable current. The experiment also used a second detector made up of 0.071 in. thick BC422 plastic scintillator material from the Bicron corporation. We compare the absolute efficiencies of these two detectors in units of optical W/cm{sup 2} into 4{pi} per x-ray, W/cm{sup 2} incident. At 7.47 keV and 900 volts MCP bias, the MCP detector delivers {approximately}1400 time more light than the scintillator detector.

Burginyon, G.A.; Jacoby, B.A.; Wobser, J.K.; Ernst, R.D.; Ancheta, D.S.; Tirsell, K.G.

1992-09-03

337

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

338

Experiment with the SPR-N Instrument Onboard the CORONAS-F Satellite: Polarization, Temporal, and Spectral Characteristics of the Hard X-Ray of the Solar Flares  

NASA Astrophysics Data System (ADS)

During the experiment with a polarimeter SPR-N onboard the CORONAS-F satellite, polarization of the X-ray of solar flares within the energy ranges of 20-40, 40-60, and 60-100 keV was measured according to Thomson scattering of X-ray photons in Beryllium plates with the following registration of the scattered photons by means of a system of six scintillation detectors based on Cs I(Na). As a result of observations for the period from August 2001 till December 2005, hard X-ray radiation was registered for 128 solar flares. During the event of 29 October 2003 degree of polarization of the radiation within the channels 40-60 and 60-100 keV exceeded 70 %, and within the channel 20-40 keV—50 %. Time profiles of the part of polarized radiation, orientation of the maximum polarization on the solar disc were obtained. The upper limit of the polarized radiation part for 25 events was estimated at the level of 8-40 %. For all registered flares time profiles (with resolution of up to 4 s) were registered, hard X-ray fluxes were determined, and spectrum factor was estimated. For the most powerful events which were observed during October-November 2003 and on January 20, 2005, the data on the dynamics of the characteristics of thermal and non-thermal components of X-radiation were obtained.

Zhitnik, I. A.; Logachev, Yu. I.; Bogomolov, A. V.; Bogomolov, V. V.; Denisov, Yu. I.; Kavanosyan, S. S.; Kuznetsov, S. N.; Morozov, O. V.; Myagkova, I. N.; Svertilov, S. I.; Ignatiev, A. P.; Oparin, S. N.; Pertsov, A. A.

339

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

340

The XMM-Newton survey of the ELAIS-S1 field. I. Number counts, angular correlation function and X-ray spectral properties  

NASA Astrophysics Data System (ADS)

Aims.The formation and evolution of cosmic structures can be probed by studying the evolution of the luminosity function of the Active Galactic Nuclei (AGNs), galaxies and clusters of galaxies and of the clustering of the X-ray active Universe, compared to the IR-UV active Universe. Methods: .To this purpose, we have surveyed with XMM-Newton the central ~0.6 deg2 region of the ELAIS-S1 field down to flux limits of ~5.5 × 10-16 erg~cm-2~s-1 (0.5-2 keV, soft band, S), ~2 × 10-15 erg~cm-2~s-1 (2-10 keV, hard band, H), and ~4 × 10-15 erg~cm-2~s-1 (5-10 keV, ultra hard band, HH). We present here the analysis of the XMM-Newton observations, the number counts in different energy bands and the clustering properties of the X-ray sources. Results: .We detect a total of 478 sources, 395 and 205 of which detected in the S and H bands respectively. We identified 7 clearly extended sources and estimated their redshift through X-ray spectral fits with thermal models. In four cases the redshift is consistent with z=0.4, so we may have detected a large scale structure formed by groups and clusters of galaxies through their hot intra-cluster gas emission. We have computed the angular correlation function of the sources in the S and H bands finding best fit correlation angles ?_0=5.2 ± 3.8 arcsec and ?_0=12.8 ± 7.8 arcsec in the two bands respectively. The correlation angle of H band sources is therefore formally ~2.5 times that of the S band sources, although the difference is at only ~1? confidence level. A rough estimate of the present-day correlation length r0 can be obtained inverting the Limber equation and assuming an appropriate redshift distribution dN/dz. The results range between 12.8 and 9.8 h-1 Mpc in the S band and between 17.9 and 13.4 h-1 Mpc in the H band, with 30-40% statistical errors, assuming either smooth redshift distributions or redshift distributions with spikes accounting for the presence of significant structure at z=0.4. The relative density of the S band sources is higher near the clusters and groups at z˜0.4 and extends toward East and toward South/West. This suggests that the structure is complex, with a size comparable to the full XMM-Newton field. Conversely, the highest relative source densities of the H band sources are located in the central-west region of the field.

Puccetti, S.; Fiore, F.; D'Elia, V.; Pillitteri, I.; Feruglio, C.; Grazian, A.; Brusa, M.; Ciliegi, P.; Comastri, A.; Gruppioni, C.; Mignoli, M.; Vignali, C.; Zamorani, G.; La Franca, F.; Sacchi, N.; Franceschini, A.; Berta, S.; Buttery, H.; Dias, J. E.

2006-10-01

341

Timing and spectral analysis of the unusual X-ray transient XTE J0421+560/CI Camelopardalis  

NASA Astrophysics Data System (ADS)

We present a detailed X-ray study of the 2003 XMM-Newton observation of the high-mass X-ray binary XTE J0421+560/CI Camelopardalis. The continuum of the X-ray spectrum is well described by a flat power law (? = 1.0 ± 0.2) with a large intrinsic absorbing column (NH = (4.4 ± 0.5) × 1023 cm-2). We have decomposed the broad iron line into three separate components: Fe I-K?, Fe I-K? and Fe XXIV-XXVK?. It is unclear how both neutral and almost fully ionized iron can exist simultaneously; however, we suggest that this could be evidence that the compact object is embedded in the circumstellar material. This does not appear to be consistent with the X-ray flux and spectrum of the source, which has remained essentially unchanged since the initial outburst. The iron abundance implied by the ratio of the neutral Fe-K? and Fe-K? is compatible with solar. We search for lags in the neutral Fe-K? with respect to the continuum and find marginal evidence for a lag at ˜10 ks. We interpret this as the light crossing time of the torus which would suggest that the neutral iron is located at a radius of 10 au. This result depends on several assumptions including the distance to the system, the inclination, the mass of system and the orbital period, none of which are known with any great certainty. Better constraints on these system parameters and further observations of this system are required to confirm this result. We discuss the nature of this system in light of our results and place it in context with other binary B[e] stars.

Bartlett, E. S.; Clark, J. S.; Coe, M. J.; Garcia, M. R.; Uttley, P.

2013-02-01

342

Spectral and photometric evolution of the B[e]/X-ray transient CI Cam after its outburst in 1998  

NASA Astrophysics Data System (ADS)

CI Cam (MWC 84, XTE J0421+560, IRAS 04156+5552) is well known owing to its strong X-ray, optical, and radio outburst in 1998 April 1. The star has ejected relativistic radio jets during the outburst, like those by SS 433. We have combined results of UBV R photometry and moderate resolution spectroscopy taken during three years since 1998 to 2001.

Barsukova, E. A.; Borisov, N. V.; Fabrika, S. N.; Goranskij, V. P.; Metlova, N. V.

2002-01-01

343

DCIV and spectral charge-pumping studies of ?-ray and X-ray irradiated power VDMOSFET devices  

Microsoft Academic Search

This paper reports the total dose effects and post-irradiation anneal effects on the two recombination current peaks and the bottom current in commercial power VDMOSFET devices irradiated with 137Cs ?-ray or X-ray radiation. The two interface recombination current peaks show a slightly different rate of increase as a function of the radiation dose. Slightly different diode ideality factors are found

M.-S. Park; I. M. Na; C. I. Lee; C. R. Wie

2002-01-01

344

Benchmark oxygen-oxygen pair-distribution function of ambient water from x-ray diffraction measurements with a wide Q-range  

SciTech Connect

Four recent x-ray diffraction measurements of ambient liquid water are reviewed here. Each of these measurements represents a significant development of the x-ray diffraction technique applied to the study of liquid water. Sources of uncertainty from statistical noise, Q-range, Compton scattering, and self-scattering are discussed. The oxygen-hydrogen contribution to the measured x-ray scattering pattern was subtracted using literature data to yield an experimental determination, with error bars, of the oxygen-oxygen pair-distribution function, g{sub OO}(r), which essentially describes the distribution of molecular centers. The extended Q-range and low statistical noise of these measurements has significantly reduced truncation effects and related errors in the g{sub OO}(r) functions obtained. From these measurements and error analysis, the position and height of the nearest neighbor maximum in g{sub OO}(r) were found to be 2.80(1) A and 2.57(5) respectively. Numerical data for the coherent differential x-ray scattering cross-section I{sub X}(Q), the oxygen-oxygen structure factor S{sub OO}(Q), and the derived g{sub OO}(r) are provided as benchmarks for calibrating force-fields for water.

Skinner, Lawrie B. [Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794-2100 (United States); X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Huang, Congcong [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, P.O. Box 20450, Stanford, California 94309 (United States); Schlesinger, Daniel; Pettersson, Lars G. M. [Department of Physics, AlbaNova University Center, Stockholm University, S-10691 Stockholm (Sweden); Nilsson, Anders [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, P.O. Box 20450, Stanford, California 94309 (United States); Department of Physics, AlbaNova University Center, Stockholm University, S-10691 Stockholm (Sweden); Benmore, Chris J. [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2013-02-21

345

The X-Ray Power Spectral Density Function and Black Hole Mass Estimate for the Seyfert Active Galactic Nucleus IC 4329a  

NASA Astrophysics Data System (ADS)

We present the X-ray broadband power spectral density function (PSD) of the X-ray-luminous Seyfert IC 4329a, constructed from light curves obtained via Rossi X-ray Timing Explorer monitoring and an XMM-Newton observation. Modeling the 3-10 keV PSD using a broken power-law PSD shape, a break in power-law slope is significantly detected at a temporal frequency of 2.5+2.5 -1.7 × 10-6 Hz, which corresponds to a PSD break timescale T b of 4.6+10.1 -2.3 days. Using the relation between T b, black hole mass M BH, and bolometric luminosity as quantified by McHardy and coworkers, we infer a black hole mass estimate of M BH = 1.3+1.0 -0.3 × 108 M sun and an accretion rate relative to Eddington of 0.21+0.06 -0.10 for this source. Our estimate of M BH is consistent with other estimates, including that derived by the relation between M BH and stellar velocity dispersion. We also present PSDs for the 10-20 and 20-40 keV bands; they lack sufficient temporal frequency coverage to reveal a significant break, but are consistent with the same PSD shape and break frequency as in the 3-10 keV band.

Markowitz, A.

2009-06-01

346

X-ray imaging with laser-Compton scattering X-ray at AIST  

Microsoft Academic Search

An X-ray facility with a compact electron linear accelerator via laser-Compton scattering (LCS X-ray) is recently installed at AIST. The LCS X-ray facility in approximately 8-m square consists of a 40-MeV linac, a femtosecond terawatt laser and an X-ray beamline. The LCS X-ray facility produces quasi-monochromatic X-rays with energy in the range of 12 ~ 40 keV which are commonly

M. Yasumoto; R. Kuroda; H. Ikeura-Sekiguchi; H. Toyokawa; N. Sei; H. Ogawa; M. Koike; K. Yamada; K. Mori; F. Sakai; S. Tamura

2009-01-01

347

MAXI/GSC detection of a rapid X-ray spectral change in the black hole candidate 4U 1630-472  

NASA Astrophysics Data System (ADS)

We report on a detection of an X-ray spectral change in the black hole candidate 4U 1630-472 with MAXI/GSC. The outburst(ATel#3830,#3945) began on 2011 December 17 (MJD 55912), and the flux peaked at 600 mCrab(2-20 keV) on 2011 December 30 (MJD 55925). From 2012 January 14 (MJD 55940) until 2012 April 13 (MJD 56030), the source stayed in the soft state holding a similar flux around ~270 mCrab (2-20 keV).

Nakahira, S.; Ueda, Y.; Yamaoka, K.; Tomida, H.; Ishikawa, M.; Ueno, S.; Mihara, T.; Sugizaki, M.; Serino, M.; Yamamoto, T.; Matsuoka, M.; Negoro, H.; Nakajima, M.; Suwa, F.; Asada, M.; Sakakibara, H.; Serita, N.; Morii, N. Kawai M.; Usui, R.; Yoshida, A.; Tsunemi, H.; Kimura, M.; Hiroi, K.; Shidatsu, M.; Sato, R.; Tsuboi, Y.; Yamauchi, M. Higa M.; Nishimura, Y.; Hanayama, T.

2012-04-01

348

Precise measurement of the lattice spacing of LaB6 standard powder by the x-ray extended range technique using synchrotron radiation  

Microsoft Academic Search

We used the basis of the x-ray extended range technique to measure the lattice spacing of LaB6 standard powder samples relative to silicon 640b standard powder samples with an accuracy of 5× 10-5 Å . 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

C. T. Chantler; C. Q. Tran; D. J. Cookson

2004-01-01

349

Low energy x-ray spectrometer  

SciTech Connect

A subkilovolt spectrometer has been produced to permit high-energy-resolution, time-dependent x-ray intensity measurements. The diffracting element is a curved mica (d = 9.95A) crystal. To preclude higher order (n > 1) diffractions, a carbon x-ray mirror that reflects only photons with energies less than approx. 1.1 keV is utilized ahead of the diffracting element. The nominal energy range of interest is 800 to 900 eV. The diffracted photons are detected by a gold-surface photoelectric diode designed to have a very good frequency response, and whose current is recorded on an oscilloscope. A thin, aluminium light barrier is placed between the diffracting crystal and the photoelectric diode detector to keep any uv generated on or scattered by the crystal from illuminating the detector. High spectral energy resolution is provided by many photocathodes between 8- and 50-eV wide placed serially along the diffracted x-ray beam at the detector position. The spectrometer was calibrated for energy and energy dispersion using the Ni L..cap alpha../sub 1/ /sub 2/ lines produced in the LLNL IONAC accelerator and in third order using a molybdenum target x-ray tube. For the latter calibration the carbon mirror was replaced by one surfaced with rhodium to raise the cut-off energy to about 3 keV. The carbon mirror reflection dependence on energy was measured using one of our Henke x-ray sources. The curved mica crystal diffraction efficiency was measured on our Low-Energy x-ray (LEX) machine. The spectrometer performs well although some changes in the way the x-ray mirror is held are desirable. 16 figures.

Woodruff, W.R.

1981-06-05

350

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

351

OPTICAL SPECTRAL PROPERTIES OF SWIFT BURST ALERT TELESCOPE HARD X-RAY-SELECTED ACTIVE GALACTIC NUCLEI SOURCES  

SciTech Connect

The Swift Burst Alert Telescope survey of active galactic nuclei (AGNs) is providing an unprecedented view of local AGNs ((z) {approx} 0.03) and their host galaxy properties. In this paper, we present an analysis of the optical spectra of a sample of 64 AGNs from the nine month survey, detected solely based on their 14-195 keV flux. Our analysis includes both archived spectra from the Sloan Digital Sky Survey and our own observations from the 2.1 m Kitt Peak National Observatory telescope. Among our results, we include line ratio classifications utilizing standard emission line diagnostic plots, [O III] 5007 A luminosities, and Hbeta-derived black hole masses. As in our X-ray study, we find the type 2 sources to be less luminous (in [O III] 5007 A and 14-195 keV luminosities) with lower accretion rates than the type 1 sources. We find that the optically classified low-ionization narrow emission line regions, H II/composite galaxies, and ambiguous sources have the lowest luminosities, while both broad-line and narrow-line Seyferts have similar luminosities. From a comparison of the hard X-ray (14-195 keV) and [O III] luminosities, we find that both the observed and extinction-corrected [O III] luminosities are weakly correlated with X-ray luminosity. In a study of the host galaxy properties from both continuum fits and measurements of the stellar absorption indices, we find that the hosts of the narrow-line sources have properties consistent with late-type galaxies.

Winter, Lisa M.; Keeney, Brian [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO (United States); Lewis, Karen T. [Department of Physics and Astronomy, Dickinson College, Carlisle, PA (United States); Koss, Michael; Veilleux, Sylvain; Mushotzky, Richard F. [Department of Astronomy, University of Maryland, College Park, MD (United States)

2010-02-10

352

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

353

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.; Gullikson, Eric.; Howells, Malcolm.; Kim, Kwang-Je.; Kirz, Janos.; Kortright, Jeff.

2000-01-01

354

Evolution of stress and microstructure in Ni/C multilayers used as x-ray optics in a wide energy range  

NASA Astrophysics Data System (ADS)

The evolution of intrinsic stress in multilayers and its behavior with growing number of periods and/or during radiation exposure, i.e. thermal treatment, becomes important in many X-ray optical applications. In Ni/C X-ray optical multilayers fabricated by pulsed laser deposition (PLD) at room temperature with typical period thickness d» 4.0 nm microstructure and intrinsic stress are analyzed with growing period number up to the layer stack delamination. Microstructure of single layers and interfaces and morphology of the total layer stack were investigated by means of transmission electron microscopy (TEM), X-ray reflectometry and diffraction. A clear indication of nano-crystallites was found for the Ni-layers, whereas the carbon layers were always amorphous. The diffraction pattern of a 300 period Ni/C layer stack hint at a hexagonal structure of the Ni crystallites with the (011)-lattice plane parallel to the Si substrate surface. Thus the elastic misfit between the Ni- and C-layers seems to be minimized. To investigate the evolution of stresses in the growing up Ni/C multilayers depth dependent stresses in the Si (100) substrate were analyzed using X-ray results of the stress tensor for Si-crystal of the substrate averaged over different penetration depths (0.6 and 3.6 µm). The found dependence of the substrate stresses on the total layer thickness point at low compressive stresses in the PLD-fabricated Ni/C X-ray optics in the range below -100 MPa at least up to a total layer thickness of 1200 nm (300 periods). An increase of the compressive stresses was obtained only for stacks of more than 300 periods. A delamination of the layer stack in part was observed at 900 periods.

Dietsch, Reiner; Holz, Thomas; Weiflbach, Danny; Melov, Valeri; Schreiber, Jurgen; Scholz, Roland

2001-11-01

355

Hard x-ray spectrometers for NIF (abstract)  

NASA Astrophysics Data System (ADS)

A National Ignition Facility (NIF) core diagnostic instrument has been designed and will be fabricated to record x-ray spectra in the 1.2-20 keV energy range. The high-energy electronic x-ray instrument has four reflection crystals with overlapping coverage of 1.2-10.9 keV and one transmission crystal covering 8.6-20 keV. The spectral resolving power varies from approximately 1000 at low energies to 315 at 20 keV. The spectrum produced by each crystal is recorded by a modified commercial dental x-ray charge coupled device (CCD) detector. The scintillators on the CCD detectors are optimized for the energy ranges. A one-channel x-ray spectrometer, using one transmission crystal covering 12-60 keV, will be fabricated for the OMEGA laser facility. The transmission crystal spectrometers are based on instruments originally designed at National Institute for Standards and Technology for the purpose of characterizing the x-ray flux from medical radiography sources. Utilizing one of those instruments and a commercial dental x-ray CCD detector, x-ray images were recorded using a single pulse from a laboratory x-ray source with a peak charging voltage of 200 kV. A resolving power of 300 was demonstrated by recording on film the K?1 and K?2 characteristic x-ray lines near 17 keV from a molybdenum anode. The continuum radiation from a tungsten anode was recorded in the 20-50 keV energy range. The transmission crystal spectrometer has sufficient spectral resolution and sensitivity to record the line and continuum radiation from high-Z targets irradiated by the NIF laser and the OMEGA laser.

Seely, John; Holland, Glenn; Brown, Charles; Deslattes, Richard; Hudson, Lawrence; Bell, Perry; Miller, Michael; Back, Christina

2001-01-01

356

Focusing crystal von Hamos spectrometer for x-ray spectroscopy and x-ray fluorescence applications  

NASA Astrophysics Data System (ADS)

The use of bent crystals with high integrated reflectivity in focusing crystal spectrometers (Johann and von Hamos schemes) is considered. It is shown that in a von Hamos scheme mosaic focusing takes place. Thus a mosaic crystal simultaneously provides high spectral resolution and high efficiency. Expressions for the mosaic focusing are obtained. Focusing mica and graphite crystal von Hamos spectrometers (radius of crystal curvature is 20 mm) are investigated: spectral and spatial resolution and absolute efficiency are measured in a spectral range of 2 - 2.6 angstroms using laser-produced plasma and iron isotope x-ray sources. The mica crystal spectrometer showed high spatial (up to 10 micrometers ) and spectral ((lambda) /(delta) (lambda) approximately 1000) resolution, whereas the graphite spectrometer showed very high efficiency (30 - 70 times higher than the mica crystal) and moderate spectral resolution ((lambda) /(delta) (lambda) approximately 500 - 750). In the latter case mosaic focusing is observed: spectral resolution is 10 - 15 times higher than spectral resolution determined by the mosaic spread of the crystal ((lambda) /(delta) (lambda) approximately 50). The results allow one to estimate a maximum efficiency for focusing crystal spectrometers. Prospects for using the von Hamos spectrometers for x-ray spectroscopy and x-ray fluorescence are considered.

Shevelko, Alexander P.; Antonov, Alexander A.; Grigorieva, Inna G.; Kasyanov, Yury S.; Knight, Larry V.; Reyes-Mena, Arturo; Turner, Clark; Wang, Quan; Yakushev, Oleg F.

2000-11-01

357

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

358

Real-time Quantitative X-Ray Spectroscopy with a von Hamos Spectrometer  

NASA Astrophysics Data System (ADS)

The real-time quantitative spectroscopy of laser-produced plasmas is explored using a compact von Hamos spectrometer and linear CCD array. This system provides excellent spectral resolution and high dynamic range for compact x-ray sources. Possible uses of this spectrometer include applications in x-ray lithography and laser produced plasma diagnostics.

Weeks, Tyler; Johnson, Michael; Raymond, Scott; Johnson, Jon Paul; Knight, Larry; Shevelko, Alexander

2004-10-01

359

Variability and Spectral Modeling of the Hard X-ray Emission of GX 339-4 in a Bright Low/Hard State  

NASA Astrophysics Data System (ADS)

We study the high-energy emission of the Galactic black hole candidate GX 339-4 using INTEGRAL/SPI and simultaneous RXTE/PCA data. By the end of 2007 January, when it reached its peak luminosity in hard X-rays, the source was in a bright hard state. The SPectrometer on INTEGRAL (SPI) data from this period show a good signal-to-noise ratio, allowing a detailed study of the spectral energy distribution up to several hundred keV. As a main result, we report on the detection of a variable hard spectral feature (>=150 keV) which represents a significant excess with respect to the cutoff power-law shape of the spectrum. The SPI data suggest that the intensity of this feature is positively correlated with the 25-50 keV luminosity of the source and the associated variability timescale is shorter than 7 hr. The simultaneous Proportional Counter Array data, however, show no significant change in the spectral shape, indicating that the source is not undergoing a canonical state transition. We analyzed the broadband spectra in the lights of several physical models, assuming different heating mechanisms and properties of the Comptonizing plasma. For the first time, we performed quantitative model fitting with the new versatile Comptonization code BELM, accounting self-consistently for the presence of a magnetic field. We show that a magnetized medium subject to pure non-thermal electron acceleration provides a framework for a physically consistent interpretation of the observed 4-500 keV emission. Moreover, we find that the spectral variability might be triggered by the variations of only one physical parameter, namely the magnetic field strength. Therefore, it appears that the magnetic field is likely to be a key parameter in the production of the Comptonized hard X-ray emission.

Droulans, R.; Belmont, R.; Malzac, J.; Jourdain, E.

2010-07-01

360

Black Hole Mass Determination in the X-Ray Binary 4U 1630-47: Scaling of Spectral and Variability Characteristics  

NASA Astrophysics Data System (ADS)

We present the results of a comprehensive investigation on the evolution of spectral and timing properties of the Galactic black hole candidate 4U 1630-47 during its spectral transitions. In particular, we show how a scaling of the correlation of the photon index of the Comptonized spectral component ? with low-frequency quasi-periodic oscillations (QPOs), ? L , and mass accretion rate, \\dot{M}, can be applied to the black hole mass and the inclination angle estimates. We analyze the transition episodes observed with the Rossi X-Ray Timing Explorer and BeppoSAX satellites. We find that the broadband X-ray energy spectra of 4U 1630-47 during all spectral states can be modeled by a combination of a thermal component, a Comptonized component, and a red-skewed iron-line component. We also establish that ? monotonically increases during transition from the low-hard state to the high-soft state and then saturates for high mass accretion rates. The index saturation levels vary for different transition episodes. Correlations of ? versus ? L also show saturation at ? ~ 3. \\Gamma {--}\\dot{M} and ?-? L correlations with their index saturation revealed in 4U 1630-47 are similar to those established in a number of other black hole candidates and can be considered as an observational evidence for the presence of a black hole in these sources. The scaling technique, which relies on XTE J1550-564, GRO 1655-40, and H1743-322 as reference sources, allows us to evaluate a black hole mass in 4U 1630-47 yielding M BH ~ 10 ± 0.1 solar masses and to constrain the inclination angle of i <~ 70°.

Seifina, Elena; Titarchuk, Lev; Shaposhnikov, Nikolai

2014-07-01

361

X-ray imaging and x-ray source development at Lawrence Livermore National Laboratory  

SciTech Connect

The Laser Program at Lawrence Livermore National Laboratory has a continuing effort to develop both x-ray sources and x-ray sources and x-ray microscopy. This effort includes the ongoing development of: (1) a wide range of x-ray lasers at the Nova Laser Facility, (2) a zone plate lens--multilayer mirror based x-ray microscope (3) three dimensional, high resolution x-ray microscopy (4) short wavelength, normal incidence multilayer x-ray mirrors, (5) compact, high average power lasers for producing x-ray lasers and laser plasma x-ray sources. We have constructed and operated an x-ray laser based transmission x-ray microscope. The advantage offered by the x-ray laser source is the extreme high brightness allows high resolution images to be made on a timescale faster than that for x-ray damage effects to appear. The microscope, consists of: the x-ray laser, a multilayer coated, near normal incidence spherical mirror used as a condenser, a silicon nitride specimen holder, an x-ray zone plate used as an objective lens, and a microchannel plate x-ray detector. The x-ray laser used is the Ni-like Ta x-ray laser operating with a wavelength of 4.48 nm, a pulselength of 200 spec, a divergence of 10 mrad, and an output energy of 10 microjoules.

Trebes, J.; Balhorn, R. [Lawrence Livermore National Lab., CA (United States); Anderson, E. [Lawrence Berkeley Lab., CA (United States)] [and others

1993-12-01

362

On the stability of the thermal Comptonization index in neutron star low-mass X-ray binaries in their different spectral states  

NASA Astrophysics Data System (ADS)

Context. Most of the spectra of neutron star low-mass X-ray binaries (NS LMXBs), whether they are persistent or transient, are characterized by the presence of a strong thermal Comptonization bump, which is thought to originate in the transition layer (TL) between the accretion disk and the NS surface. The observable quantities that characterize this component, which is dominating the emission below 30 keV, are the spectral index ? and the rollover energy, both related to the electron temperature and optical depth of the plasma. Aims: Starting from observational results on a sample of NS LMXBs in different spectral states, we formulate the problem of X-ray spectral formation in the TL of these sources. We predict a stability of the thermal Comptonization spectral index in different spectral states if the energy release in the TL is much higher than the intercepted flux coming from the accretion disk. Methods: We use an equation for the energy balance and the radiative transfer diffusion equation for a slab geometry in the TL to derive a formula for the thermal Comptonization index ?. We show that in this approximation the TL electron temperature kTe and optical depth ?0 can be written as a function of the energy flux from the disk intercepted by the corona (TL) and that in the corona itself, Qdisk/Qcor. Because the spectral index ? depends on kTe and ?0, this in turn leads to a relation ? = f(Qdisk/Qcor), with ? ~ 1 when Qdisk/Qcor ? 1. Results: We show that the observed spectral index ? for the sample of sources here considered lies in a belt around 1 ± 0.2 apart for the case of GX 354-0. Comparing our theoretical predictions with observations, we claim that this result, which is consistent with the condition Qdisk/Qcor ? 1, can give us constraints on the accretion geometry of these systems, an issue that seems difficult to be solved with only the spectral analysis method.

Farinelli, R.; Titarchuk, L.

2011-01-01

363

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

364

Accurate measurement and physical insight: The X-ray extended range technique for fundamental atomic physics, condensed matter research and biological sciences  

NASA Astrophysics Data System (ADS)

Research in core physics or atomic and condensed matter science is increasingly relevant for diverse fields and are finding application in chemistry, engineering and biological sciences, linking to experimental research at synchrotrons, reactors and specialised facilities. Over recent synchrotron experiments and publications we have developed methods for measuring the absorption coefficient far from the edge and in the XAFS (X-ray absorption fine structure) region in neutral atoms, simple compounds and organometallics reaching accuracies of below 0.02%. This is 50-500 times more accurate than earlier methods, and 50-250 times more accurate than claimed uncertainties in theoretical computations for these systems. The data and methodology are useful for a wide range of applications, including major synchrotron and laboratory techniques relating to fine structure, near-edge analysis and standard crystallography. Experiments are sensitive to theoretical and computational issues, including correlation between convergence of electronic and atomic orbitals and wavefunctions. Hence, particularly in relation to the popular techniques of XAFS and XANES (X-ray absorption near-edge structure), this development calls for strong theoretical involvement but has great applications in solid state structural determination, catalysis and enzyme environments, active centres of biomolecules and organometallics, phase changes and fluorescence investigations and others. We discuss key features of the X-ray extended range technique (XERT) and illustrate applications.

Chantler, C. T.

2010-02-01

365

Spatial resolution of a hard x-ray CCD detector.  

PubMed

The spatial resolution of an x-ray CCD detector was determined from the widths of the tungsten x-ray lines in the spectrum formed by a crystal spectrometer in the 58 to 70 keV energy range. The detector had 20 microm pixel, 1700 by 1200 pixel format, and a CsI x-ray conversion scintillator. The spectral lines from a megavolt x-ray generator were focused on the spectrometer's Rowland circle by a curved transmission crystal. The line shapes were Lorentzian with an average width after removal of the natural and instrumental line widths of 95 microm (4.75 pixels). A high spatial frequency background, primarily resulting from scattered gamma rays, was removed from the spectral image by Fourier analysis. The spectral lines, having low spatial frequency in the direction perpendicular to the dispersion, were enhanced by partially removing the Lorentzian line shape and by fitting Lorentzian curves to broad unresolved spectral features. This demonstrates the ability to improve the spectral resolution of hard x-ray spectra that are recorded by a CCD detector with well-characterized intrinsic spatial resolution. PMID:20697439

Seely, John F; Pereira, Nino R; Weber, Bruce V; Schumer, Joseph W; Apruzese, John P; Hudson, Lawrence T; Szabo, Csilla I; Boyer, Craig N; Skirlo, Scott

2010-08-10

366

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

367

X-ray spectroscopy of five BL Lacertae objects  

NASA Technical Reports Server (NTRS)

Five X-ray bright BL Lacertae objects were observed in the energy range 0.6-4.5 keV with the solid state spectrometer (SSS) of the Einstein Observatory. The 14 SSS spectra obtained represent most of the X-ray spectra of BL Lac objects with resolution better than approximately 3. These data do not reveal the presence of large amounts of thermal gas, with upper limits for the equivalent width of individual spectral features typically less that about 100 eV. However, the SSS spectra are the first set of X-ray data to indicate low-energy absorption in excess of that caused by the cold interstellar matter in the Galaxy. Comparison with contemporaneous, lower energy X-ray data implies that this absorption does not arise in cold neutral material, but in hotter, highly ionized material, probably intrinsic to the source. All five BL Lac objects have X-ray continua that are well fitted by power-law models, with power-law energy indices usually greater than about 1. In a few cases, a flattening at higher energies is observed; these and other data suggest that two-component X-ray spectra, steep at low energies and flat at high energies, are a common feature of BL Lac objects. Three of the five sources clearly vary between SSS observations, with time scales ranging from days to years. A historical synopsis of the X-ray spectral data confirms the tendency for BL Lacertae objects to be highly variable in the X-ray band but reveals no correlation between spectral and intensity changes.

Urry, C. M.; Mushotzky, R. F.; Holt, S. S.

1986-01-01

368

Soft x-ray interferometry  

SciTech Connect

The purpose of the soft x-ray interferometry workshop held at Lawrence Berkeley Laboratory was to discuss with the scientific community the proposed technical design of the soft x-ray Fourier-transform spectrometer being developed at the ALS. Different design strategies for the instrument`s components were discussed, as well as detection methods, signal processing issues, and how to meet the manufacturing tolerances that are necessary for the instrument to achieve the desired levels of performance. Workshop participants were encouraged to report on their experiences in the field of Fourier transform spectroscopy. The ALS is developing a Fourier transform spectrometer that is intended to operate up to 100 eV. The motivation is solely improved resolution and not the throughput (Jaquinot) or multiplex (Fellgett) advantage, neither of which apply for the sources and detectors used in this spectral range. The proposed implementation of this is via a Mach-Zehnder geometry that has been (1) distorted from a square to a rhombus to get grazing incidence of a suitable angle for 100 eV and (2) provided with a mirror-motion system to make the path difference between the interfering beams tunable. The experiment consists of measuring the emergent light intensity (I(x)) as a function of the path difference (x). The resolving power of the system is limited by the amount of path difference obtainable that is 1 cm (one million half-waves at 200{angstrom} wavelength) in the design thus allowing a resolving power of one million. The free spectral range of the system is limited by the closeness with which the function I(x) is sampled. It is proposed to illuminate a helium absorption cell with roughly 1%-band-width light from a monochromator thus allowing one hundred aliases without spectral overlap even for sampling of I(x) at one hundredth of the Nyquist frequency.

Not Available

1993-09-01

369

A Comprehensive Analysis of Swift XRT Data. I. Apparent Spectral Evolution of Gamma-Ray Burst X-Ray Tails  

Microsoft Academic Search

An early steep decay component following the prompt GRBs is commonly observed in Swift XRT light curves, which is regarded as the tail emission of the prompt gamma rays. Prompted by the observed strong spectral evolution in the tails of GRBs 060218 and 060614, we present a systematic time-resolved spectral analysis for the Swift GRB tails detected between 2005 February

Bin-Bin Zhang; En-Wei Liang; Bing Zhang

2007-01-01

370

Cosmic x ray physics  

NASA Technical Reports Server (NTRS)

The annual progress report on Cosmic X Ray Physics for the period 1 Jan. to 31 Dec. 1990 is presented. Topics studied include: soft x ray background, new sounding rocket payload: x ray calorimeter, and theoretical studies.

Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.

1991-01-01

371

Cosmic x ray physics  

NASA Technical Reports Server (NTRS)

The annual progress report on Cosmic X Ray Physics is presented. Topics studied include: the soft x ray background, proportional counter and filter calibrations, the new sounding rocket payload: X Ray Calorimeter, and theoretical studies.

Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.

1990-01-01

372

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 ...

373

X-Ray Astronomy  

NASA Technical Reports Server (NTRS)

Dr. S. N. Zhang has lead a seven member group (Dr. Yuxin Feng, Mr. XuejunSun, Mr. Yongzhong Chen, Mr. Jun Lin, Mr. Yangsen Yao, and Ms. Xiaoling Zhang). This group has carried out the following activities: continued data analysis from space astrophysical missions CGRO, RXTE, ASCA and Chandra. Significant scientific results have been produced as results of their work. They discovered the three-layered accretion disk structure around black holes in X-ray binaries; their paper on this discovery is to appear in the prestigious Science magazine. They have also developed a new method for energy spectral analysis of black hole X-ray binaries; four papers on this topics were presented at the most recent Atlanta AAS meeting. They have also carried Monte-Carlo simulations of X-ray detectors, in support to the hardware development efforts at Marshall Space Flight Center (MSFC). These computation-intensive simulations have been carried out entirely on the computers at UAH. They have also carried out extensive simulations for astrophysical applications, taking advantage of the Monte-Carlo simulation codes developed previously at MSFC and further improved at UAH for detector simulations. One refereed paper and one contribution to conference proceedings have been resulted from this effort.

Wu, S. T.

2000-01-01

374

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.

375

Diamond Photodetectors for X-Ray Absorption Spectroscopy Applications  

SciTech Connect

Synchrotron radiation (SR) is a fundamental tool for X-ray research. In particular, X-ray absorption spectroscopy (XAS) accesses information as electronic properties, local structure or chemical-physical state in condensed-matter studies. Ionization chambers (ICs) are the most widely used XAS detectors for transmission measurements because of their reliability, high linearity and good stability. Recently, solid-state detectors have been considered and Si p-i-n has been applied to high fluxes (10{sup 11} ph/s), where the linearity of ICs is no longer guaranteed. Silicon photodiodes exhibit an extremely linear response in at least 5 decades but show diffraction peaks. Diamond is an ideal substrate to produce radiation-hard, low dark current (<1 pA/cm{sup 2}), visible-blind and fast-response X-ray detectors with a high S/N ratio. Diamond detectors were tested as SR monitor capable to withstand the high photon flux density of the 3{sup rd} generation SR sources. Being the lowest X-ray-absorbing solid-state dielectric material, diamond maximizes the flux through thin self-standing devices with minimal spectral effect down to the soft x-ray range. We will present results of X-ray tests of photoconductors based on different diamond substrates. The results will be compared to standard ICs for XAS applications in terms of spectral quality, noise and linearity in the 4-13 keV energy range.

Pace, Emanuele; De Sio, Antonio [Dip. di Astronomia e Scienza dello Spazio, Universita di Firenze, L.go E. Fermi 2, 50125 Firenze (Italy); Pan Zhiyun; Wu Ziyu [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 200023 (China); Marcelli, Augusto [INFN-Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044, Frascati, Roma (Italy)

2010-06-23

376

Absolute calibration of Kodak Biomax-MS film response to x rays in the 1.5- to 8-keV energy range  

NASA Astrophysics Data System (ADS)

The absolute response of Kodak Biomax-MS film to x rays in the range from 1.5- to 8-keV has been measured using a laboratory electron-beam generated x-ray source. The measurements were taken at specific line energies by using Bragg diffraction to produce monochromatic beams of x rays. Multiple exposures were taken on Biomax MS film up to levels exceeding optical densities of 2 as measured by a microdensitometer. The absolute beam intensity for each exposure was measured with a Si(Li) detector. Additional response measurements were taken with Kodak direct exposure film (DEF) so as to compare the results of this technique to previously published calibrations. The Biomax-MS results have been fitted to a semiempirical mathematical model (Knauer et al., these proceedings). Users of the model can infer absolute fluences from observed exposure levels at either interpolated or extrapolated energies. To summarize the results: Biomax MS has comparable sensitivity to DEF film below 3 keV but has reduced sensitivity above 3 keV (~50%). The lower exposure results from thinner emulsion layers, designed for use with phosphor screens. The ease with which Biomax-MS can be used in place of DEF (same format film, same developing process, and comparable sensitivity) makes it a good replacement.

Marshall, F. J.; Knauer, J. P.; Anderson, D.; Schmitt, B. L.

2006-10-01

377

Measured conversion efficiencies of P45, paraterphenyl, tetraphenyl butadiene, and sodium salicylate phosphors in the soft-x-ray wavelength range  

SciTech Connect

The measured conversion efficiencies at 9.89, 23.6, 44.7, and 160 A of P45 phosphor screens, as well as those of paraterphenyl, tetraphenyl butadiene, and sodium salicylate at 9.89, 44.7, and 67.6 A, are presented. The conversion efficiency is defined as the ratio of photoelectrons ejected from the photocathode of a visible detector, which are excited by the scintillated photons that are emitted from the phosphor in a solid angle of 2[pi], to the number of soft-x-ray photons incident on the phosphor. The effect of the phosphor's thickness on the conversion efficiency was studied. The P45 phosphor converts the soft-x-ray photon (10--200 A) into an order of magnitude more visible photons than the low-[ital Z] phosphors. The P45 phosphor screen used in conjunction with a photomultiplier tube offers a soft-x-ray photodetector with a conversion efficiency that ranges from 0.5 at 160 A to 12 at 9.89 A and a high electronic gain.

Regan, S.P.; Huang, L.K.; May, M.J.; Moos, H.W. (Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218 (United States)); Stutman, D.; Kovnovich, S.; Finkenthal, M. (Racah Institute of Physics, The Hebrew University, Jerusalem (Israel))

1994-06-01

378

An in-vacuum x-ray diffraction microscope for use in the 0.7-2.9 keV range  

SciTech Connect

A dedicated in-vacuum coherent x-ray diffraction microscope was installed at the 2-ID-B beamline of the Advanced Photon Source for use with 0.7-2.9 keV x-rays. The instrument can accommodate three common implementations of diffractive imaging; plane wave illumination; defocused-probe (Fresnel diffractive imaging) and scanning (ptychography) using either a pinhole, focused or defocused probe. The microscope design includes active feedback to limit motion of the optics with respect to the sample. Upper bounds on the relative optics-to-sample displacement have been measured to be 5.8 nm(v) and 4.4 nm(h) rms/h using capacitance micrometry and 27 nm/h using x-ray point projection imaging. The stability of the measurement platform and in-vacuum operation allows for long exposure times, high signal-to-noise and large dynamic range two-dimensional intensity measurements to be acquired. Finally, we illustrate the microscope's stability with a recent experimental result.

Vine, D. J. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); School of Physics, University of Melbourne, Victoria 3010 (Australia); Argonne National Laboratory, Argonne, Illinois 60439 (United States); Williams, G. J. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Clark, J. N. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia); London Centre for Nanotechnology, University College, London WC1E 6BT (United Kingdom); Putkunz, C. T.; Abbey, B.; Nugent, K. A. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); School of Physics, University of Melbourne, Victoria 3010 (Australia); Pfeifer, M. A. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); Cornell High Energy Synchrotron Source, Cornell University, Ithaca, New York 14850 (United States); Legnini, D.; Roehrig, C.; Wrobel, E.; McNulty, I. [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Huwald, E. [Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia); Riessen, G. van; Peele, A. G. [Australian Research Council Centre of Excellence for Coherent X-ray Science (Australia); Department of Physics, La Trobe University, Bundoora, Victoria 3086 (Australia); Beetz, T.; Irwin, J.; Feser, M.; Hornberger, B. [Xradia, Inc., 4385 Hopyard Road, Pleasanton, California 94588 (United States)

2012-03-15

379

Atmospheric electron x-ray spectrometer  

NASA Technical Reports Server (NTRS)

The present invention comprises an apparatus for performing in-situ elemental analyses of surfaces. The invention comprises an atmospheric electron x-ray spectrometer with an electron column which generates, accelerates, and focuses electrons in a column which is isolated from ambient pressure by a:thin, electron transparent membrane. After passing through the membrane, the electrons impinge on the sample in atmosphere to generate characteristic x-rays. An x-ray detector, shaping amplifier, and multi-channel analyzer are used for x-ray detection and signal analysis. By comparing the resultant data to known x-ray spectral signatures, the elemental composition of the surface can be determined.

Feldman, Jason E. (Inventor); George, Thomas (Inventor); Wilcox, Jaroslava Z. (Inventor)

2002-01-01

380

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

381

The Chandra X-ray Observatory: An Astronomical Facility Available to the World  

NASA Technical Reports Server (NTRS)

The Chandra X-ray observatory, one of NASA's "Great Observatories," provides high angular and spectral resolution X-ray data which is freely available to all. In this review I describe the instruments on chandra along with their current calibration, as well as the chandra proposal system, the freely-available Chandra analysis software package CIAO, and the Chandra archive. As Chandra is in its 6th year of operation, the archive already contains calibrated observations of a large range of X-ray sources. The Chandra X-ray Center is committed to assisting astronomers from any country who wish to use data from the archive or propose for observations

Smith, Randall K.

2006-01-01