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1

Diffuse X-Ray Emission from the Quiescent Superbubble M17, the Omega Nebula  

NASA Astrophysics Data System (ADS)

The emission nebula M17 contains a young ~1 Myr old open cluster; the winds from the OB stars of this cluster have blown a superbubble around the cluster. ROSAT observations of M17 detected diffuse X-ray emission peaking at the cluster and filling the superbubble interior. The young age of the cluster suggests that no supernovae have yet occurred in M17; therefore, it provides a rare opportunity to study hot gas energized solely by shocked stellar winds in a quiescent superbubble. We have analyzed the diffuse X-ray emission from M17 and compared the observed X-ray luminosity of ~2.5×1033 ergs s-1 and the hot gas temperature of ~8.5×106 K and mass of ~1 Msolar to model predictions. We find that bubble models with heat conduction overpredict the X-ray luminosity by 2 orders of magnitude; the strong magnetic fields in M17, as measured from H I Zeeman observations, have most likely inhibited heat conduction and associated mass evaporation. Bubble models without heat conduction can explain the X-ray properties of M17, but only if cold nebular gas can be dynamically mixed into the hot bubble interior and the stellar winds are clumpy with mass-loss rates reduced by a factor of >=3. Future models of the M17 superbubble must take into account the large-scale density gradient, small-scale clumpiness, and strong magnetic field in the ambient interstellar medium.

Dunne, Bryan C.; Chu, You-Hua; Chen, C.-H. Rosie; Lowry, Justin D.; Townsley, Leisa; Gruendl, Robert A.; Guerrero, Martín A.; Rosado, Margarita

2003-06-01

2

Further Constraints on Thermal Quiescent X-Ray Emission from SAX J1808.4-3658  

NASA Astrophysics Data System (ADS)

We observed SAX J1808.4-3658 (1808), the first accreting millisecond pulsar, in deep quiescence with XMM-Newton and (near simultaneously) Gemini-South. The X-ray spectrum of 1808 is similar to that observed in quiescence in 2001 and 2006, describable by an absorbed power law with photon index 1.74 ± 0.11 and unabsorbed X-ray luminosity LX = 7.9 ± 0.7 × 1031 ergs s-1, for NH = 1.3 × 1021 cm-2. Fitting all the quiescent XMM-Newton X-ray spectra with a power law, we constrain any thermally emitting neutron star (NS) with a hydrogen atmosphere to have a temperature less than 30 eV and L NS (0.01-10 keV) <6.2 × 1030 ergs s-1. A thermal plasma model also gives an acceptable fit to the continuum. Adding an NS component to the plasma model produces less stringent constraints on the NS; a temperature of 36+4 -8 eV and L NS (0.01-10 keV) = 1.3+0.6 -0.8 × 1031 ergs s-1. In the framework of the current theory of NS heating and cooling, the constraints on the thermal luminosity of 1808 and 1H 1905+000 require strongly enhanced cooling in the cores of these NSs. We compile data from the literature on the mass transfer rates and quiescent thermal flux of the largest possible sample of transient NS low-mass X-ray binaries. We identify a thermal component in the quiescent spectrum of the accreting millisecond pulsar IGR J00291+5934, which is consistent with the standard cooling model. The contrast between the cooling rates of IGR J00291+5934 and 1808 suggests that 1808 may have a significantly larger mass. This can be interpreted as arising from differences in the binary evolution history or initial NS mass in these otherwise similar systems. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Heinke, C. O.; Jonker, P. G.; Wijnands, R.; Deloye, C. J.; Taam, R. E.

2009-02-01

3

Strongly absorbed quiescent X-ray emission from the X-ray transient XTE J0421+56 (CI Cam) observed with XMM-Newton  

Microsoft Academic Search

We have observed the X-ray transient XTE J0421+56 in quiescence with XMM-Newton. The observed spectrum is highly unusual being dominated by an emission feature at ~ 6.5 keV. The spectrum can be fit using a partially covered power-law and Gaussian line model, in which the emission is almost completely covered (covering fraction of 0.98 -0.06+0.02) by neutral material and is

L. Boirin; A. N. Parmar; T. Oosterbroek; D. Lumb; M. Orlandini; N. Schartel

2002-01-01

4

The Variable Quiescent X-Ray Emission of the Neutron Star Transient XTE J1701-462  

NASA Astrophysics Data System (ADS)

We have monitored the cooling of the neutron star in the transient low-mass X-ray binary XTE J1701-462 with Chandra and XMM-Newton since the source entered quiescence in 2007 after an exceptionally luminous 19-month outburst. A recent Chandra observation made almost 1200 days into quiescence indicates that the neutron star crust is likely still slowly cooling toward thermal equilibrium with the core. The current surface temperature is high compared to other quiescent neutron star transients, with an implied bolometric thermal flux of 5×1033 erg/s. The overall cooling curve seems to have followed a broken power-law shape as predicted by theoretical models, although the observed break is considerably earlier than what is expected from theory. After rapid cooling during the first 200 days of quiescence---strongly indicating a highly conductive neutron star crust---the source unexpectedly showed a large temporary increase in both thermal and non-thermal flux. Prompted by this we conducted a Swift monitoring program of the source during April-October 2010, with short observations taking place once every two weeks. During the program we detected short-term flares up to at least 1×1035 erg/s, a factor of 20 higher than the normal quiescent level. We compare this flaring---presumably arising from episodic low-level accretion---with the behavior observed from faint Galactic transients, and discuss whether flaring in XTE J1701-462 can significantly affect the cooling of the source and whether it can to some extent explain the high temperature of the neutron star core implied by our Chandra observations.

Fridriksson, Joel K.; Homan, J.; Wijnands, R.; Cackett, E. M.; Degenaar, N.; Mendez, M.; Altamirano, D.; Brown, E. F.; Belloni, T. M.; Lewin, W. H. G.

2011-01-01

5

A New Method to Search for Quiescent Low-Mass X-ray Binary  

NASA Astrophysics Data System (ADS)

We explore a new method in searching for quiescent Low-Mass X-ray Binary (qLMXB). To date, almost all the accretion-powered BH-LMXBs, which stay in their quiescent state most of the time, were only found during their X-ray outburst. Our method explores a new way to find accretion binaries in their quiescent states. We search objects with spectral types earlier than K and M_V more than 2-? brighter than that expected for a main-sequence star, then look for stars in the above sample with log(F_X/F_R) (0.5-2. keV) more than 2-? greater than that seen in typical subgiant stars. Most likely there is an accretion disk responsible for the extra X-ray emission. We show one example target of this study, with its X-ray and optical data.

Zhao, Ping; Grindlay, J. E.; Hong, J.; Servillat, M.; Van Den Berg, M.

2013-01-01

6

A DEEP RADIO SURVEY OF HARD STATE AND QUIESCENT BLACK HOLE X-RAY BINARIES  

SciTech Connect

We have conducted a deep radio survey of a sample of black hole X-ray binaries in the hard and quiescent states to determine whether any systems were sufficiently bright for astrometric follow-up with high-sensitivity very long baseline interferometric arrays. The one hard-state system, Swift J1753.5-0127, was detected at a level of 0.5 mJy beam{sup -1}. All 11 quiescent systems were not detected. In the three cases with the highest predicted quiescent radio brightnesses (GRO J0422+32, XTE J1118+480, and GRO J1655-40), the new capabilities of the Expanded Very Large Array were used to reach noise levels as low as 2.6 {mu}Jy beam{sup -1}. None of the three sources were detected to 3{sigma} upper limits of 8.3, 7.8, and 14.2 {mu}Jy beam{sup -1}, respectively. These observations represent the most stringent constraints to date on quiescent radio emission from black hole X-ray binaries. The uncertainties in the source distances, quiescent X-ray luminosities at the times of the observations, and the power-law index of the empirical correlation between radio and X-ray luminosities make it impossible to determine whether these three sources are significantly less luminous in the radio band than expected. Thus it is not clear whether that correlation holds all the way down to quiescence for all black hole X-ray binaries.

Miller-Jones, J. C. A. [International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA 6845 (Australia); Jonker, P. G. [SRON, Netherlands Institute for Space Research, 3584 CA, Utrecht (Netherlands); Maccarone, T. J.; Calvelo, D. E. [School of Physics and Astronomy, University of Southampton, Highfield SO17 IBJ (United Kingdom); Nelemans, G., E-mail: james.miller-jones@curtin.edu.au [Department of Astrophysics, IMAPP, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen (Netherlands)

2011-09-20

7

A New Method to Search for Quiescent Low-Mass X-ray Binary  

NASA Astrophysics Data System (ADS)

We explore a new method in searching for quiescent Low-Mass X-ray Binaries (qLMXBs). To date, almost all the accretion-powered BH-LMXBs, which stay in their quiescent state most of the time, were only found during their X-ray outburst. Our method explores a new way to find accretion binaries in their quiescent states. We search objects with spectral types earlier than K and M$_V$ more than 2-$\\sigma$ brighter than that expected for a main-sequence star, then look for stars in the above sample with $log(F_X/F_R)$ (0.5-2. keV) more than 2-$\\sigma$ greater than that seen in typical subgiant stars. Most likely there is an accretion disk responsible for the extra X-ray emission. We show one example target of this study, with its X-ray and optical data. This approach opens a new way to search for accretion binaries hidden in the Galactic plane.

Zhao, Ping; Grindlay, J. E.; Hong, J.; Servillat, M.; Van Den Berg, M.

2013-04-01

8

Doppler tomography of the black hole binary A0620-00 and the origin of chromospheric emission in quiescent X-ray binaries  

NASA Astrophysics Data System (ADS)

Context. Doppler tomography of emission line profiles in low-mass X-ray binaries allows us to disentangle the different emission sites and study the structure and variability of accretion disks. Aims: We present UVES high-resolution spectroscopic observations of the black hole binary A0620-00 at quiescence. Methods: These spectroscopic data constrain the orbital parameters Porb = 0.32301405(1) d and K2 = 437.1 ± 2.0 km s-1. These values, together with the mass ratio q = M2/M1 = 0.062 ± 0.010, imply a minimum mass for the compact object of M1 sin3 i = 3.15 ± 0.10 M_?, consistent with previous works. Results: The H? emission from the accretion disk is much weaker than in previous studies, possibly because of a decrease in disk activity. Doppler imaging of the H? line shows for the first time a narrow component coming from the secondary star, with an observed equivalent width of 1.4 ± 0.3 Å, perhaps associated to chromospheric activity. Subtracting a K-type template star and correcting for the veiling of the accretion disk yields an equivalent width of 2.8 ± 0.3 Å. A bright hot spot is also detected at the position where the gas stream trajectory intercepts the accretion disk. Conclusions: The H? flux associated to the secondary star is too large to be powered by X-ray irradiation. It is comparable to those observed in RS CVn binaries with similar orbital periods and is probably triggered by the rapid stellar rotation. Based on observations obtained with UVES at VLT Kueyen 8.2 m telescope in programme 66.D-0157(A).

González Hernández, J. I.; Casares, J.

2010-06-01

9

The Quiescent X-Ray Properties of the Accreting Millisecond X-Ray Pulsar and Eclipsing binary Swift J1749.4-2807  

NASA Astrophysics Data System (ADS)

Swift J1749.4-2807 is a transient neutron star low-mass X-ray binary that contains an accreting millisecond X-ray pulsar spinning at 518 Hz. It is the first of its kind that displays X-ray eclipses, which holds significant promise to precisely constrain the mass of the neutron star. We report on a ~= 105 ks long XMM-Newton observation performed when Swift J1749.4-2807 was in quiescence. We detect the source at a 0.5-10 keV luminosity of sime1 × 1033(D/6.7 kpc)2 erg s-1. The X-ray light curve displays three eclipses that are consistent in orbital phase and duration with the ephemeris derived during outburst. Unlike most quiescent neutron stars, the X-ray spectrum can be adequately described with a simple power law, while a pure-hydrogen atmosphere model does not fit the data. We place an upper limit on the 0.01-100 keV thermal luminosity of the cooling neutron star of <~ 2 × 1033 erg s-1 and constrain its temperature to be <~ 0.1 keV (for an observer at infinity). Timing analysis does not reveal evidence for X-ray pulsations near the known spin frequency of the neutron star or its first overtone with a fractional rms of <~ 34% and <~ 28%, respectively. We discuss the implications of our findings for dynamical mass measurements, the thermal state of the neutron star, and the origin of the quiescent X-ray emission.

Degenaar, N.; Patruno, A.; Wijnands, R.

2012-09-01

10

X-ray emission from comets.  

PubMed

The discovery of x-ray emission from comet Hyakutake was surprising given that comets are known to be cold. Observations by x-ray satellites such as the Röntgen Satellite (ROSAT) indicate that x-rays are produced by almost all comets. Theoretical and observational work has demonstrated that charge-exchange collisions of highly charged solar wind ions with cometary neutral species can explain this emission. X-ray observations of comets and other solar system objects may be used to determine the structure and dynamics of the solar wind. PMID:12004110

Cravens, T E

2002-05-10

11

The X-ray Polarization Signature of Quiescent Magnetars: Effect of Magnetospheric Scattering and Vacuum Polarization  

NASA Astrophysics Data System (ADS)

In the magnetar model, the quiescent non-thermal soft X-ray emission from anomalous X-ray pulsars and soft gamma repeaters is thought to arise from resonant Comptonization of thermal photons by charges moving in a twisted magnetosphere. Robust inference of physical quantities from observations is difficult, because the process depends strongly on geometry, and current understanding of the magnetosphere is not very deep. The polarization of soft X-ray photons is an independent source of information, and its magnetospheric imprint remains only partially explored. In this paper, we calculate how resonant cyclotron scattering would modify the observed polarization signal relative to the surface emission, using a multidimensional Monte Carlo radiative transfer code that accounts for the gradual coupling of polarization eigenmodes as photons leave the magnetosphere. We employ a globally twisted, self-similar, force-free magnetosphere with a power-law momentum distribution, assume a blackbody spectrum for the seed photons, account for general relativistic light deflection close to the star, and assume that vacuum polarization dominates the dielectric properties of the magnetosphere. The latter is a good approximation if the pair multiplicity is not much larger than unity. Phase-averaged polarimetry is able to provide a clear signature of the magnetospheric reprocessing of thermal photons and to constrain mechanisms generating the thermal emission. Phase-resolved polarimetry, in addition, can characterize the spatial extent and magnitude of the magnetospheric twist angle at ~100 stellar radii, and discern between uni- or bidirectional particle energy distributions, almost independently of every other parameter in the system. We discuss prospects for detectability with the Gravity and Extreme Magnetism (GEMS) mission.

Fernández, Rodrigo; Davis, Shane W.

2011-04-01

12

Quest for quiescent neutron star low mass x-ray binaries in the Small Magellanic Cloud  

NASA Astrophysics Data System (ADS)

We present the first spectral search for neutron stars (NSs) in low-mass X-ray binaries (LMXBs) between outbursts in the Small Magellanic Cloud (SMC). We identify and discuss candidate LMXBs in quiescence in the SMC using deep Chandra X-ray observations of two portions of the SMC. We produce X-ray color-magnitude-diagrams of XRSs of these two fields and identify 10 candidates for quiescent NS LMXBs. Spectral fitting and searches for optical counterparts rule out five, leaving five candidate quiescent NS LMXBs. We estimate that we are sensitive to ˜ 10% of quiescent NS LMXBs in our fields. Our fields include 4.4 × 10^7 M? of stellar mass, giving an upper limit of 10^-6 LMXBs per M? in the SMC. We place a lower limit on the average duty cycle of NS LMXBs as ˜ 0.003.

Chowdhury, Mizanul Huq

13

The Planetary X-ray Emission  

Microsoft Academic Search

\\u000a With the advent of Chandra and XMM-Newton X-ray observatories, several new solar system bodies have been discovered to be\\u000a an X-ray source at energies below 2?keV: leading to significant advances in the field of planetary X-ray emission and astronomy\\u000a during the last one decade. Apart from the Sun, the known X-ray emitters now include Venus, Earth, Mars, Jupiter, and Saturn,

Anil Bhardwaj

2010-01-01

14

Proton induced x ray emission analysis  

Microsoft Academic Search

A solid mathematical basis is established for the use of thick target Proton Induced X ray Emission (PIXE) analysis to determine the trace element concentrations in solid samples. With the advent of high resolution Si(Li) detectors there was a revival of interest in the use of characteristic x ray induced by high energy particle beams. It was shown that it

Eric Clayton

1988-01-01

15

Champlane's Search For Quiescent High-mass X-ray Binaries  

NASA Astrophysics Data System (ADS)

The ongoing Chandra Multiwavelength Plane Survey has built a vast database of 15,000 serendipitous Chandra sources in archival ACIS pointings in the Galactic plane. With follow-up deep optical/nIR imaging and spectroscopy, we aim to constrain the Galactic population of low-luminosity (Lx<10^34 erg/s) compact accreting binaries. Here we present the results of a search for candidate high-mass quiescent X-ray binaries (qHMXBs). We have selected O/B counterparts to Chandra sources and examine their measured X-ray spectral hardness, X-ray variability, X-ray-to-optical flux ratio, and inferred distance and X-ray luminosity; in this way we identify 1 promising qHMXB candidate. We compare the properties of the likely isolated O/B stars to those known from earlier shallower (e.g. ROSAT) surveys.

Quinn, Samuel; van den Berg, M.; Hong, J.; Laycock, S.; Grindlay, J.; Zhao, P.

2009-01-01

16

X-ray emissions associated with thunderstorms  

NASA Astrophysics Data System (ADS)

We used an x-ray detector, including a NaI scintillator and a photomultiplier tube, to (1) compare x-ray emissions during thunderstorm and non-thunderstorm days and (2) examine x-ray emissions associated with specific lightning processes. X-ray data were acquired in 2010 and 2011 at the Lightning Observatory in Gainesville (LOG) [e.g., Mallick et al., 2011] in conjunction with corresponding electric field and electric field derivative waveforms (for thunderstorm days). Record length was 240 ms. The system was triggered on the electric field during thunderstorms and manually on non-thunderstorm days. The average x-ray rate on thunderstorm days, 124 counts per second, is higher than that, 95 counts per second, on non-thunderstorm days, and the difference is statistically significant. Non-thunderstorm days were defined as those with no thunderstorms within at least 15 km of LOG. X-ray emissions on these days are attributed to cosmic rays and natural Earth radioactivity. Fig. 1 shows average x-ray counts per second in different energy ranges for both thunderstorm and non-thunderstorm days. On July 31st, 2011, we recorded x-ray bursts associated with three close multiple-stroke natural lightning flashes along with their electric field and electric field derivative waveforms. These flashes transported negative charge to ground. The total number of bursts is six, and they are all apparently associated with stepped and dart-stepped leaders. Interestingly, some subsequent-stroke leaders are more prolific x-ray producers than first-stroke leaders. Also, for the same leader, some steps are accompanied by pronounced x-ray signals, while others are not. Reference Mallick, S. et al., On Remote Measurements of Lightning Peak Currents, XIV International Conference on Atmospheric Electricity (ICAE), August 08-12, 2011, Rio de Janeiro, Brazil.

Mallick, S.; Rakov, V. A.; Dwyer, J. R.; Hill, J. D.

2011-12-01

17

ASCA Observation of the Quiescent X-Ray Counterpart to SGR 1627-41.  

PubMed

We present a 2-10 keV ASCA observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power-law, blackbody, or bremsstrahlung function, with unabsorbed flux approximately 5x10-12 ergs cm-2 s-1. We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both of which were noted in the earlier BeppoSAX observations. PMID:10587486

Hurley; Strohmayer; Li; Kouveliotou; Woods; van Paradijs J; Murakami; Hartmann; Smith; Ando; Yoshida; Sugizaki

2000-01-01

18

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

Microsoft Academic Search

A novel electron cyclotron resonance x-ray source is constructed based on the ECR technique. In this paper, the possibility of using the ECR x-ray source for producing UV rays by optimizing the plasma parameters is explored. X-ray and UV emissions from the ECR x-ray source are carried out for argon, nitrogen, and CO2 plasma. The x-ray spectral and dose measurements

R. Baskaran; T. S. Selvakumaran

2008-01-01

19

Constraining the neutron star equation of state using quiescent low-mass X-ray binaries  

SciTech Connect

Chandra or XMM-Newton observations of quiescent low-mass X-ray binaries can provide important constraints on the equation of state of neutron stars. The mass and radius of the neutron star can potentially be determined from fitting a neutron star atmosphere model to the observed X-ray spectrum. For a radius measurement it is of critical importance that the distance to the source is well constrained since the fractional uncertainty in the radius is at least as large as the fractional uncertainty in the distance. Uncertainties in modelling the neutron star atmosphere remain. At this stage it is not yet clear if the soft thermal component in the spectra of many quiescent X-ray binaries is variable on timescales too short to be accommodated by the cooling neutron star scenario. This can be tested with a long XMM-Newton observation of the neutron star X-ray transient Cen X-4 in quiescence. With such an observation one can use the Reflection Grating Spectrometer spectrum to constrain the interstellar extinction to the source. This removes this parameter from the X-ray spectral fitting of the EPIC pn and MOS spectra and allows one to investigate whether the variability observed in the quiescent X-ray spectrum of this source is due to variations in the soft thermal spectral component or variations in the power law spectral component coupled with variations in N{sub H}. This will test whether the soft thermal component can indeed be due to the hot thermal glow of the neutron star. Irrespective of the outcome of such a study, the observed cooling in quiescence in sources for which the crust is significantly out of thermal equilibrium with the core due to a prolonged outburst, such as KS 1731-260, seem excellent candidates for mass and radius determinations through modelling the observed X-rays with a neutron star atmosphere model (the caveats about the source distance and atmosphere modelling do also apply here obviously and presently prevent one from obtaining such constraints). Finally, the fact that the soft thermal glow in sources such as SAX J1808.4-3658 and 1H 1905+000 has not been detected in quiescence means that the neutron star cores of these sources must be cold. The most plausible explanation seems to be that the neutron stars are more massive than 1.4 M{sub {center_dot}} and cool via the direct URCA process.

Jonker, P. G. [SRON, Netherlands Institute for Space Research, 3584 CA, Utrecht (Netherlands); Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, Massachusetts (United States); Astronomical Institute, Utrecht University, 3508 TA, Utrecht (Netherlands)

2008-02-27

20

Constraining the neutron star equation of state using quiescent low-mass X-ray binaries  

NASA Astrophysics Data System (ADS)

Chandra or XMM-Newton observations of quiescent low-mass X-ray binaries can provide important constraints on the equation of state of neutron stars. The mass and radius of the neutron star can potentially be determined from fitting a neutron star atmosphere model to the observed X-ray spectrum. For a radius measurement it is of critical importance that the distance to the source is well constrained since the fractional uncertainty in the radius is at least as large as the fractional uncertainty in the distance. Uncertainties in modelling the neutron star atmosphere remain. At this stage it is not yet clear if the soft thermal component in the spectra of many quiescent X-ray binaries is variable on timescales too short to be accommodated by the cooling neutron star scenario. This can be tested with a long XMM-Newton observation of the neutron star X-ray transient Cen X-4 in quiescence. With such an observation one can use the Reflection Grating Spectrometer spectrum to constrain the interstellar extinction to the source. This removes this parameter from the X-ray spectral fitting of the EPIC pn and MOS spectra and allows one to investigate whether the variability observed in the quiescent X-ray spectrum of this source is due to variations in the soft thermal spectral component or variations in the power law spectral component coupled with variations in NH. This will test whether the soft thermal component can indeed be due to the hot thermal glow of the neutron star. Irrespective of the outcome of such a study, the observed cooling in quiescence in sources for which the crust is significantly out of thermal equilibrium with the core due to a prolonged outburst, such as KS 1731-260, seem excellent candidates for mass and radius determinations through modelling the observed X-rays with a neutron star atmosphere model (the caveats about the source distance and atmosphere modelling do also apply here obviously and presently prevent one from obtaining such constraints). Finally, the fact that the soft thermal glow in sources such as SAX J1808.4-3658 and 1H 1905+000 has not been detected in quiescence means that the neutron star cores of these sources must be cold. The most plausible explanation seems to be that the neutron stars are more massive than 1.4 Msolar and cool via the direct URCA process.

Jonker, P. G.

2008-02-01

21

The Quiescent X-ray Spectrum: Constraints from Stellar Mass Black Holes  

NASA Astrophysics Data System (ADS)

The quiescent state (L_x \\lesssim 1e-6 L_Edd) is the dominant accretion mode for black holes on all mass scales. However, our knowledge of the X-ray spectral shape is limited by the combination of low S/N and the presence of significant contamination in the case of SMBHs. Galactic stellar mass black holes present an environment free of the contamination present in galactic nuclei, but are still affected by low S/N. Here, we present a re-analysis of all archival observations of the dynamically confirmed stellar mass back holes in the quiescent state (resulting in a sample of 8 black holes). The spectra are found to be consistent with a common spectral shape for all systems. Assuming this to be so, we model all spectra simultaneously to obtain the best available constraints on the X-ray spectral shape at low luminosity. These results will be discussed in the context of models for the quiescent accretion flow onto black holes.

Reynolds, Mark; Reis, R. C.; Miller, J. M.; Cackett, E.; Degenaar, N.

2013-04-01

22

Discovery of a very extended X-ray halo around a quiescent spiral galaxy The “missing link” of galaxy formation  

NASA Astrophysics Data System (ADS)

Hot gaseous haloes surrounding galaxies and extending well beyond the distribution of stars are a ubiquitous prediction of galaxy formation scenarios. The haloes are believed to consist of gravitationally trapped gas with a temperature of millions of Kelvin. The existence of such hot haloes around massive elliptical galaxies has been established through their X-ray emission. While gas out-flowing from starburst spiral galaxies has been detected, searches for hot haloes around normal, quiescent spiral galaxies have so far failed, casting doubts on the fundamental physics in galaxy formation models. Here we present the first detection of a hot, large-scale gaseous halo surrounding a normal, quiescent spiral galaxy, NGC 5746, alleviating a long-standing problem for galaxy formation models. In contrast to starburst galaxies, where the X-ray halo can be powered by the supernova energy, there is no such power source in NGC 5746. The only compelling explanation is that we are here witnessing a galaxy forming from gradually in-flowing hot and dilute halo gas.

Pedersen, Kristian; Rasmussen, Jesper; Sommer-Larsen, Jesper; Toft, Sune; Benson, Andrew J.; Bower, Richard G.

2006-05-01

23

X-ray emission from supernova remnants  

SciTech Connect

This thesis deals with the x-ray spectra of supernova remnants (SNRs) and, in particular, the x-ray spectra of the two young Type I SNRs SN1006 and Tycho. An extensive grid of nonequilibrium model spectra of SNRs in the adiabatic blast wave stage of evolution is computed, and numerous diagnostics of the state and composition of the blast wave plasma are plotted over parameter space. It is demonstrated that the spectrum of an adiabatic blast wave is a good approximation to several other model SNR structures in which emission is dominated by gas undergoing quasi steady state ionization near a shock front, including the one-fluid isothermal blast wave similarity solution. None of these structures appears able to account for the observed spectra of SN1006 or Tycho. A new similarity solution for the early time evolution of uniform ejecta moving into an external medium is presented. It is argued that the x-ray spectra of SN1006 and Tycho are consistent with emission mainly from a reverse shock into 1.4 solar masses of initially uniform density SN ejecta consisting of pure heavy elements, moving into a uniform medium. Satisfactory fits to the observed spectra are obtained with a two layer structure of ejecta, an outer layer of unprocessed material, and an inner layer of mixed processed heavy elements. Various salient aspects of the physics of a shock-heated pure heavy element plasma are discussed.

Sackville Hamilton, A.J.

1985-01-01

24

Solar Flare Doppler Blueshifted Soft X-Ray Emission and Hard X-Ray Bursts  

NASA Astrophysics Data System (ADS)

Hard X-ray emission and the dynamics of soft X-ray emitting plasma are among the most immediate manifestations of solar flare energy release. To understand better the early impulsive phase of solar flare energy release, we have examined Ca XIX and Fe XXV soft X-ray resonance line spectra that exhibit strong blue-wing asymmetries from 32 flares. These spectra were obtained with the Bragg Crystal Spectrometer on the Japanese Yohkoh spacecraft, which is up to 10 times more sensitive than previously flown crystal spectrometers. The increased sensitivity allowed the comparison of Doppler blueshifted X-ray emission to hard X-ray emission observed with the Compton Gamma Ray Observatory's Burst and Transient Source Experiment, the Yohkoh Wide Band Spectrometer, and Yohkoh Hard X-Ray Telescope. We found that (1) hard X-ray burst light curves and resonance line blue-wing light curves are similar for most flares that exhibit strong blueshifts; (2) the time evolution of the intensity ratio of the blue wing to the peak unshifted spectral component resembles higher energy hard X-ray emission more closely than the blue-wing light curve alone; (3) though many flares had blue-wing/resonance peak ratios that resembled or peaked at the same time as the hard X-ray burst, nearly one-third of the flares exhibited ratio curves that either were nonzero before the detection of burst hard X-rays or peaked before the hard X-ray burst peaked-a few of these flares exhibited small blueshifted line profiles before the detection of hard X-ray emission; (4) a few flares with strong blueshifts had little or no detectable emission above 30 keV; and (5) the time derivative of the resonance peak emission usually resembles the blue-wing light curve. The implication of these results for current flare models is discussed.

Rilee, M. L.; Doschek, G. A.

2001-06-01

25

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

NASA Astrophysics Data System (ADS)

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

Baskaran, R.; Selvakumaran, T. S.

2008-02-01

26

Synchrotron-Radiation Induced X-Ray Emission (SRIXE)  

Microsoft Academic Search

Elemental analysis using emission of characteristic x rays is a well-established scientific method. The success of this analytical method is highly dependent on the properties of the source used to produce the x rays. X-ray tubes have long existed as a principal excitation source, but electron and proton beams have also been employed extensively. The development of the synchrotron radiation

Keith W

1999-01-01

27

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

SciTech Connect

A novel electron cyclotron resonance x-ray source is constructed based on the ECR technique. In this paper, the possibility of using the ECR x-ray source for producing UV rays by optimizing the plasma parameters is explored. X-ray and UV emissions from the ECR x-ray source are carried out for argon, nitrogen, and CO{sub 2} plasma. The x-ray spectral and dose measurements are carried with NaI(Tl) based spectrometer and dosimeter, respectively. For UV measurement, a quartz window arrangement is made at the exit port and the UV intensity is measured at 5 cm from the quartz plate using UV meter. The x-ray and UV emissions are carried out for different microwave power levels and gas pressures. The x-ray emission is observed in the pressure range {<=}10{sup -5} Torr, whereas the UV emission is found to be negligible for the gas pressures <10{sup -5} Torr and it starts increasing in the pressure range between 10{sup -5} and 10{sup -3} Torr. At high-pressure range, collision frequency of electron-atom is large which leads to the higher UV flux. At low pressure, the electron-atom collision frequency is low and hence the electrons reach high energy and by hitting the cavity wall produces higher x-ray flux. By choosing proper experimental conditions and plasma gas species, the same source can be used as either an x-ray source or an UV source.

Baskaran, R.; Selvakumaran, T. S. [Radiological Safety Division, Indira Gandhi Center for Atomic Research, Kalpakkam 603 102, Tamil Nadu (India)

2008-02-15

28

X-ray emission from GPS and CSS sources  

NASA Astrophysics Data System (ADS)

Many X-ray observations of GigaHertz Peaked Spectrum and Compact Steep Spectrum sources have been made with Chandra X-ray Observatory and XMM-Newton Observatory over the last few years. The X-ray spectra contribute the important information to the total energy distribution of the compact radio sources. In addition the spatial resolution of Chandra allows for studies of the X-ray morphology of these sources on arcsec scales and provide a direct view of their environments. This paper gives a review of the current status of the X-ray observations and their contribution to our understanding of the nature of these compact radio sources. It also describes primary physical processes that lead to the observed X-ray emission and summarize X-ray emission properties expected from interactions between an expanding radio source and the intergalactic environment.

Siemiginowska, A.

2009-02-01

29

Field emission arrays for medical x-ray imaging  

SciTech Connect

Experiments demonstrate the feasibility of using microfabricated cold field emission cathodes in x-ray sources for medical imaging. Electron beam currents of 25 mA at voltages of 25 kV have been used to produce x-ray source focal spot diameters of 0.2 mm. Analysis of both filtered and unfiltered x-ray spectra from molybdenum anodes show clear characteristic x-ray lines. These x-ray source characteristics are consistent with the requirements for human breast imaging.

Schwoebel, P.R. [SRI International, Menlo Park, California 94025 (United States)

2006-03-13

30

Crustal Heating and Quiescent Emission from Transiently Accreting Neutron Stars  

NASA Astrophysics Data System (ADS)

Nuclear reactions occurring at densities ~1012 g cm-3 in the crust of a transiently accreting neutron star efficiently maintain the core at a temperature ~ (5-10)x107 K. When accretion halts, the envelope relaxes to a thermal equilibrium set by the flux from the hot core, as if the neutron star were newly born. For the time-averaged accretion rates (<~10-10 Msolar yr-1) typical of low-mass X-ray transients, standard neutrino cooling is unimportant and the core thermally reradiates the deposited heat. The resulting luminosity is ~ 5x1032-5x1033 ergs s-1 and agrees with many observations of transient neutron stars in quiescence. Confirmation of this mechanism would strongly constrain rapid neutrino cooling mechanisms for neutron stars (e.g., a pion condensate). Thermal emission had previously been dismissed as a predominant source of quiescent emission since blackbody spectral fits implied an emitting area much smaller than a neutron star's surface. However, as with thermal emission from radio pulsars, fits with realistic emergent spectra will imply a substantially larger emitting area. Other emission mechanisms, such as accretion or a pulsar shock, can also operate in quiescence and generate intensity and spectral variations over short timescales. Indeed, quiescent accretion may produce gravitationally redshifted metal photoionization edges in the quiescent spectra (detectable with AXAF and XMM). We discuss past observations of Aql X-1 and note that the low-luminosity (less than 1034 ergs s-1) X-ray sources in globular clusters and the Be star/X-ray transients are excellent candidates for future study.

Brown, Edward F.; Bildsten, Lars; Rutledge, Robert E.

1998-09-01

31

HARD X-RAY EMISSION ASSOCIATED WITH WHITE DWARFS. III  

SciTech Connect

Hard X-ray emission associated with white dwarfs (WDs) can be used to diagnose the presence of late-type binary companions, mass accretion from companions, or physical processes with unknown origins. Since our previous systematic searches for hard X-ray emission associated with WDs, the Galactic WD catalog has been augmented by >10,000 new WDs from the Sloan Digital Sky Survey and new X-ray point-source catalogs from XMM-Newton and ROSAT have become available. Therefore, we have extended the search using the updated catalogs, and found 17 new cases of WDs associated with hard X-ray emission. The 32 WDs associated with hard X-ray emission, from the current and previous searches, can be divided into five categories: (1) binary WD with a coronal companion, (2) binary WD with mass transfer from a companion, (3) single hot WD with a hard X-ray component peaking near 1 keV in addition to a soft photospheric component, (4) two PG 1159 stars with very faint X-ray emission in the 0.9-2.0 keV band, and (5) two DA WDs whose photospheric emission component has a hard shoulder extending to 0.5-0.9 keV. The origin of the hard X-ray emission in the latter three categories is not yet known. Deeper X-ray observations with higher angular and spectral resolutions are needed to help us understand these WDs' hard X-ray emission.

BilIkova, Jana; Chu, You-Hua; Gruendl, Robert A.; Maddox, Larry A. [Astronomy Department, University of Illinois at Urbana-Champaign, 1002 W. Green St., Urbana, IL 61801 (United States)

2010-11-15

32

Constraints on X-ray emissions from the reionization era  

NASA Astrophysics Data System (ADS)

We examine the constraints on soft X-ray photon emissions from the reionization era. It is generally assumed that the Universe was reionized by ultraviolet photons radiated from massive stars. However, it has been argued that X-ray photons associated with the death of these stars would have contributed ˜10 per cent to the total number of ionizations via several channels. The parameter space for a significant component of cosmological reionization to be sourced by X-rays is limited by a few observations. We revisit the unresolved soft X-ray background constraint on high-redshift X-ray production and show that soft X-ray background measurements significantly limit the contribution to reionization from several potential sources: X-rays from X-ray binaries, from Compton scattering off supernovae-accelerated electrons, and from the annihilation of dark matter particles. We discuss the additional limits on high-redshift X-ray photon production from (1) z ˜ 3 measurements of metal absorption lines in quasar spectra, (2) the consensus that helium reionization was ending at z ? 3 and (3) measurements of the intergalactic medium's thermal history. We show that observations of z ˜ 3 metal lines allow little room for extra coeval soft X-ray emission from a non-standard X-ray sources. In addition, we show that the late reionization of helium makes it quite difficult to also ionize the hydrogen at z > 6 with a single source population (such as quasars) and that it likely requires the spectrum of ionizing emissions to soften with increasing redshift. However, we find that it is difficult to constrain an X-ray contribution to reionization from the intergalactic temperature history. We show that the intergalactic gas would have been heated to a narrower range of temperatures than is typically assumed at reionization, 2-3 × 104 K, with this temperature depending weakly on the ionizing sources' spectra.

McQuinn, Matthew

2012-10-01

33

X-Ray Emission from the Guitar Nebula.  

National Technical Information Service (NTIS)

We have detected weak soft X-ray emission from the pulsar wind nebula trailing the high-velocity star PSR 2224+65 (the 'Guitar Nebula'). This X-ray flux gives evidence of gamma approximately 10(exp 7) eV particles in the pulsar wind and constrains the pro...

R. W. Romani J. M. Cordes I. A. Yadigaroglu

1997-01-01

34

Image x-ray emission converters and microstrip porous dielectric x-ray detector  

SciTech Connect

The effective, fast, and accurate registration of x ray depends on the quality conversion of the X-quanta to photoelectrons. In this respect, of high interest are porous x-ray emission converters (PXECs). They are analogs of porous secondary electron emitters (PSEEs); the only difference is that active porous material should have high absorption properties for the X-quanta energies to be detected. Microstrip porous dielectric detector (MSPDD) is highly effective for x-ray registration without preliminary conversion of the X-quanta. Earlier it was shown that PSEE similar to PXEC has a high emission factor for 1-2 MeV {beta}-particles and 5 MeV {alpha}-particles. It was shown that MSPDDs and PSEEs are very stable.

Lorikyan, M. P. [Yerevan Physics Institute, 2 Alikhanian Br. Str., Yerevan 0036 (Armenia)

2008-11-01

35

The X-ray Emission of Galaxies  

NASA Astrophysics Data System (ADS)

The systematic study of galaxies in X-rays began with the high-resolution imaging X-ray telescope, the Einstein Observatory, launched by NASA in 1978. In the more than 30 years since, culminating with Chandra, X-ray observations have shown a different view of galaxies, consisting of gravity-driven populations of compact sources (XRBs, AGNs), and copious amounts of X-ray emitting plasmas. This gaseous component is either mechanically heated by supernovae, galaxy interactions and jets, or photo-ionized by AGNs, or gravity-confined by galaxy dark halos; and in all cases enriched in metals by the evolving stellar population. Observations of XRB populations have provided a new tool for understanding the evolution of binary stars in different environments, and for relating it to the evolution of the parent galaxy. Imaging and spectral observations of hot plasmas provide unique data for understanding the physical and chemical evolution of the gaseous component of galaxies, in comparison with models and theoretical simulations. Finally, peering deep into the nuclear regions, we are beginning to acquire direct new observational insight on the interaction of AGNs with their surroundings, and discover the nuclear remnants of galaxy mergers.

Fabbiano, P.

2012-09-01

36

A tidal disruption-like X-ray flare from the quiescent galaxy SDSS J120136.02+300305.5  

NASA Astrophysics Data System (ADS)

Aims: The study of tidal disruption flares from galactic nuclei has historically been hampered by a lack of high quality spectral observations taken around the peak of the outburst. Here we introduce the first results from a program designed to identify tidal disruption events at their peak by making near-real-time comparisons of the flux seen in XMM-Newton slew sources with that seen in ROSAT. Methods: Flaring extragalactic sources, which do not appear to be AGN, are monitored with Swift and XMM-Newton to track their temporal and spectral evolution. Timely optical observations are made to monitor the reaction of circumnuclear material to the X-ray flare. Results: SDSS J120136.02+300305.5 was detected in an XMM-Newton slew from June 2010 with a flux 56 times higher than an upper limit from ROSAT, corresponding to LX ~ 3 × 1044 erg s-1. It has the optical spectrum of a quiescent galaxy (z = 0.146). Overall the X-ray flux has evolved consistently with the canonical t-5/3 model, expected for returning stellar debris, fading by a factor ~300 over 300 days. In detail the source is very variable and became invisible to Swift between 27 and 48 days after discovery, perhaps due to self-absorption. The X-ray spectrum is soft but is not the expected tail of optically thick thermal emission. It may be fit with a Bremsstrahlung or double-power-law model and is seen to soften with time and declining flux. Optical spectra taken 12 days and 11 months after discovery indicate a deficit of material in the broad line and coronal line regions of this galaxy, while a deep radio non-detection implies that a jet was not launched during this event. Partly based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck-institut für Astronomie Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC) and observations made with the WHT operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

Saxton, R. D.; Read, A. M.; Esquej, P.; Komossa, S.; Dougherty, S.; Rodriguez-Pascual, P.; Barrado, D.

2012-05-01

37

X-ray Emission from the Guitar Nebula  

Microsoft Academic Search

We have detected weak soft X-ray emission from the Pulsar Wind Nebula\\u000atrailing the high velocity star PSR 2224+65 (the `Guitar Nebula'). This X-ray\\u000aflux gives evidence of \\\\gamma~10^7 eV particles in the pulsar wind and\\u000aconstrains the properties of the post-shock flow. The X-ray emission is most\\u000aeasily understood if the shocked pulsar wind is partly confined in the

Roger W. Romani; James M. Cordes; I.-A. Yadigaroglu

1997-01-01

38

X-Ray and Gamma-Ray Emissions from Rotation Powered Millisecond Pulsars  

NASA Astrophysics Data System (ADS)

The Fermi Large Area Telescope has revealed that rotation powered millisecond pulsars (MSPs) are a major contributor to the Galactic ?-ray source population. Such pulsars may also be important in modeling the quiescent state of several low-mass X-ray binaries (LMXBs), where optical observations of the companion star suggest the possible existence of rotation powered MSPs. To understand the observational properties of the different evolutionary stages of MSPs, the X-ray and ?-ray emissions associated with the outer gap model are investigated. For rotation powered MSPs, the size of the outer gap and the properties of the high-energy emission are controlled by either the photon-photon pair-creation process or magnetic pair-creation process near the surface. For these pulsars, we find that the outer gap model controlled by the magnetic pair-creation process is preferable in explaining the possible correlations between the ?-ray luminosity or non-thermal X-ray luminosity versus the spin-down power. For the accreting MSPs in quiescent LMXBs, the thermal X-ray emission at the neutron star (NS) surface resulting from deep crustal heating can control the conditions in the outer gap. We argue that the optical modulation observed in the quiescent state of several LMXBs originates from the irradiation of the donor star by ?-rays from the outer gap. In these systems, the irradiation luminosity required for the optical modulation of the source such as SAX J1808.4-3658 can be achieved for a NS of high mass. Finally, we discuss the high-energy emission associated with an intra-binary shock in black widow systems, e.g., PSR B1957+20.

Takata, J.; Cheng, K. S.; Taam, Ronald E.

2012-01-01

39

X-RAY AND GAMMA-RAY EMISSIONS FROM ROTATION POWERED MILLISECOND PULSARS  

SciTech Connect

The Fermi Large Area Telescope has revealed that rotation powered millisecond pulsars (MSPs) are a major contributor to the Galactic {gamma}-ray source population. Such pulsars may also be important in modeling the quiescent state of several low-mass X-ray binaries (LMXBs), where optical observations of the companion star suggest the possible existence of rotation powered MSPs. To understand the observational properties of the different evolutionary stages of MSPs, the X-ray and {gamma}-ray emissions associated with the outer gap model are investigated. For rotation powered MSPs, the size of the outer gap and the properties of the high-energy emission are controlled by either the photon-photon pair-creation process or magnetic pair-creation process near the surface. For these pulsars, we find that the outer gap model controlled by the magnetic pair-creation process is preferable in explaining the possible correlations between the {gamma}-ray luminosity or non-thermal X-ray luminosity versus the spin-down power. For the accreting MSPs in quiescent LMXBs, the thermal X-ray emission at the neutron star (NS) surface resulting from deep crustal heating can control the conditions in the outer gap. We argue that the optical modulation observed in the quiescent state of several LMXBs originates from the irradiation of the donor star by {gamma}-rays from the outer gap. In these systems, the irradiation luminosity required for the optical modulation of the source such as SAX J1808.4-3658 can be achieved for a NS of high mass. Finally, we discuss the high-energy emission associated with an intra-binary shock in black widow systems, e.g., PSR B1957+20.

Takata, J.; Cheng, K. S. [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Taam, Ronald E., E-mail: takata@hku.hk, E-mail: hrspksc@hkucc.hku.hk, E-mail: r-taam@northwestern.edu [Department of Physics and Astronomy, Northwestern University, 2131 Tech Drive, Evanston, IL 60208 (United States)

2012-01-20

40

Search for Hard X-Ray Emission from the Soft X-Ray Transient Aquila X-1  

Microsoft Academic Search

We are investigating the possibility of hard x-ray emission from the recurrent soft x-ray transient and x-ray burst source Aquila X-1 (Aql X-1). Outbursts of this source are relatively frequent with a spacing of ~ 4-10 months (Kitamoto, S. et al. 1993, ApJ, 403, 315). The recent detections of hard tails (\\\\(>\\\\)20 keV) in low luminosity x-ray bursters (Barret, D.

B. A. Harmon; S. N. Zhang; W. S. Paciesas; M. Tavani; P. Kaaret; E. Ford

1994-01-01

41

X-ray emissions from comets detected in the Röntgen X-ray satellite all-sky survey  

Microsoft Academic Search

After the unexpected discovery of X-rays emitted from comet C\\/1996 B2 (Hyakutake) with the Röntgen X-ray Satellite (ROSAT) in March 1996, X-ray emissions from comets C\\/1990 K1 (Levy), C\\/1990 N1 (Tsuchiya-Kiuchi), 45P (Honda-Mrkos-Pajdusakova), and C\\/1991 A2 (Arai), optically 300 to 30000 times fainter than Hyakutake, were discovered in archival ROSAT data. These findings establish comets as a class of X-ray

K. Dennerl; J. Englhauser; J. Trümper

1997-01-01

42

Stimulated X-ray emission for materials science.  

PubMed

Resonant inelastic X-ray scattering and X-ray emission spectroscopy can be used to probe the energy and dispersion of the elementary low-energy excitations that govern functionality in matter: vibronic, charge, spin and orbital excitations. A key drawback of resonant inelastic X-ray scattering has been the need for high photon densities to compensate for fluorescence yields of less than a per cent for soft X-rays. Sample damage from the dominant non-radiative decays thus limits the materials to which such techniques can be applied and the spectral resolution that can be obtained. A means of improving the yield is therefore highly desirable. Here we demonstrate stimulated X-ray emission for crystalline silicon at photon densities that are easily achievable with free-electron lasers. The stimulated radiative decay of core excited species at the expense of non-radiative processes reduces sample damage and permits narrow-bandwidth detection in the directed beam of stimulated radiation. We deduce how stimulated X-ray emission can be enhanced by several orders of magnitude to provide, with high yield and reduced sample damage, a superior probe for low-energy excitations and their dispersion in matter. This is the first step to bringing nonlinear X-ray physics in the condensed phase from theory to application. PMID:23965622

Beye, M; Schreck, S; Sorgenfrei, F; Trabant, C; Pontius, N; Schüßler-Langeheine, C; Wurth, W; Föhlisch, A

2013-08-21

43

Proton-Induced X-Ray Emission Analysis  

Microsoft Academic Search

The aim of this thesis is to establish a solid mathematical basis for the use of thick target Proton Induced X-ray Emission (PIXE) analysis to the determination of trace element concentrations in solid samples. With the advent of high resolution Si(Li) detectors there was a revival of interest in the use of characteristic X-rays induced by high energy particle beams.

Eric John Clayton

1989-01-01

44

Unresolved Soft X-Ray Emission from the Galactic Disk  

NASA Astrophysics Data System (ADS)

The soft X-ray sky below 1 keV is spatially smooth after subtracting the local structure. In high galactic latitude regions, emissions from faint unresolved extragalactic point sources, i.e., the Cosmic X-ray Background (CXB), are responsible for ~40 % of the soft X-ray emission in the ROSAT R45 band 0.44-1.0 keV) (McCammom et al. 2002). Since the interstellar X-ray absorption column density is high enough 10^22 cm^-2) to block the extragalactic X-ray photons below 1 keV totally in the galactic midplane, it is naturally expected that the X-ray surface brightness in the R45 band decreases by ~40 %. However, the R45 band surface brightness reduces only by ~20 % or less from high galactic latitude regions to the midplane regions. This issue has been known as the “M band problem” (McCammom & Sanders 1990; Cox 2005). M band itself is a name of the energy band which is almost the same as the ROSAT R45 band. Masui et al. (2009) discovered the existence of an unresolved emission in its energy spectrum from a region located in the midplane for the first time and this excess emission is considered to be partly filling the decrease of the extragalactic component in the midplane. Spectral analysis revealed that this excess emission is represented well by a thin thermal emission with a temperature of abount 0.8 keV. If this excess emission is an answer for the M band problem, this should be observed in other midplane regions. We searched for this excess emission using archival data of Suzaku which has the lowest and stable background and therefore is optimum for faint soft X-ray emissions. Systematic analysis for over 100 observations with the galactic latitude of |b| < 5 was conducted and finally we detected excess emissions successfully from different 11 regions in the midplane (Mitsuishi et al. in prep). Temperatures ranges from 0.6 keV to 1.3 keV with different intensities. Our results suggests that these excess emissions are distributed in the whole galactic disk region such as CXB and the Galactic ridge X-ray emission. The origin for these excess emissions is also discussed in this conference.

Mitsuishi, Ikuyuki; Sato, T.; Kimura, S.; Mitsuda, K.; Yamasaki, N. Y.; Takei, Y.; Ohashi, T.; McCammon, D.

2013-04-01

45

Auroral X-ray emission at Jupiter: Depth effects  

NASA Astrophysics Data System (ADS)

Auroral X-ray emissions from Jupiter with a total power of about 1 GW have been observed by the Einstein Observatory, Roentgen satellite, Chandra X-ray Observatory, and XMM-Newton. Previous theoretical studies have shown that precipitating energetic sulfur and oxygen ions can produce the observed X-rays. This study presents the results of a hybrid Monte Carlo (MC) model for sulfur and oxygen ion precipitation at high latitudes, looks at differences with the continuous slow-down model, and compares the results to synthetic spectra fitted to observations. We concentrate on the effects of altitude on the observed spectrum. The opacity of the atmosphere to the outgoing X-ray photons is found to be important for incident ion energies greater than about 1.2 MeV per nucleon for both sulfur and oxygen. Model spectra are calculated for intensities with and without any opacity effects. These synthetic spectra were compared with the results shown by Hui et al. (2010) which fit Chandra X-ray Observatory observations for the north and south Jovian auroral emissions. Quenching of long-lived excited states of the oxygen ions is found to be important. Opacity considerably diminishes the outgoing X-ray intensity calculated, particularly when the viewing geometry is not favorable.

Ozak, N.; Schultz, D. R.; Cravens, T. E.; Kharchenko, V.; Hui, Y.-W.

2010-11-01

46

On the soft X-ray emission of M82  

NASA Astrophysics Data System (ADS)

We present a spatial analysis of the soft X-ray and H? emissions from the outflow of the starburst galaxy M82. We find that the two emissions are tightly correlated on various scales. The O VII triplet of M82, as resolved by X-ray grating observations of XMM-Newton, is dominated by the forbidden line, inconsistent with the thermal prediction. The O VII triplet also shows some spatial variations. We discuss three possible explanations for the observed O VII triplet, including the charge exchange at interfaces between the hot outflow and neutral cool gas, a collisional non-equilibrium-ionization recombining plasma, and resonance scattering.

Liu, J.; Wang, Q. D.; Mao, S.

2012-04-01

47

Auger-electron, X-ray and optical emissions  

NASA Astrophysics Data System (ADS)

A system to simultaneously measure Auger-electron, X-ray and optical emissions, induced by 100-400 keV heavy ions from surfaces, has been designed, constructed and tested. The Auger spectrometer is a rotatable, 30°-entrance-angle, parallel-plate electron energy analyzer with a channeltron detector and it has a resolution of 0.29%. The X-ray and optical emissions are measured with a standard Si(Li) PIXE detector and electronics and with a Jarrell-Ash monochrometer, respectively. Preliminary data are presented.

Trbojevic, D.; Treado, P. A.; Lambert, J. M.

1985-05-01

48

Detecting X-ray Emission from Cometary Atmospheres Using the Suzaku X-ray Imaging Spectrometer  

SciTech Connect

The Suzaku X-ray imaging spectrometer has been used to observe the X-ray emission from comets 73P/Schwassmann-Wachmann 3C and 8P/Tuttle. Comet 73P/Schwassmann-Wachmann 3C was observed during May and June of 2006, while it was near perihelion and passed within 0.1 AU of the Earth. Comet 8P/Tuttle was observed during January of 2008 when it was at its closest approach to the Earth at 0.25 AU, and again near perihelion at a distance of 0.5 Au from Earth. In the case of comet 73P/Schwassmann Wachmann 3C, the XIS spectra show line emission from highly charged oxygen and carbon ions as well as emission from what is most likely L-shell transitions from Mg, Si, and S ions. This line emission is caused by charge exchange recombination between solar wind ions and cometary neutrals, and can be used as a diagnostic of the solar wind. Here we present some of the results of the observation of the comet 73P/Schwassmann-Wachmann 3C.

Brown, G V; Beiersdorfer, P; Bodewits, D; Porter, F S; Ezoe, Y; Hamaguchi, K; Hanya, M; Itoh, M; Kilbourne, C A; Kohmura, T; Maeda, Y; Negoro, H; Tsuboi, Y; Tsunemi, H; Urata, Y

2009-11-16

49

Tentative study on x-ray enhancement by fluorescent emission of radiation by plasma x-ray source  

Microsoft Academic Search

Tentative study on characteristic x-ray enhancement by fluorescent emission of radiation by plasma x-ray source is described. The enhancement was performed by the plasma flash x-ray generator having a cold-cathode triode. And the generator employs a high-voltage power supply, a low-impedance coaxial transmission line with a gap switch, a high-voltage condenser with a capacity of 200 nF, a turbo-molecular pump,

Eiichi Sato; Michiaki Sagae; Toshio Ichimaru; Yasuomi Hayasi; Hidenori Ojima; Kazuyoshi Takayama; Hideaki Ido; Kimio Sakamaki; Yoshiharu Tamakawa

1999-01-01

50

The correlation of solar flare hard X-ray bursts with Doppler blueshifted soft X-ray flare emission  

Microsoft Academic Search

We have investigated the temporal correlation between hard X-ray bursts and the intensity of Doppler blueshifted soft X-ray spectral line emission. We find a strong correlation for many events that have intense blueshifted spectral signatures and some correlation in events with modest blueshifts. The onset of hard X-rays frequently coincides to within a few seconds with the onset of blueshifted

R. D. Bentley; G. A. Doschek; G. M. Simnett; M. L. Rilee; J. T. Mariska; J. L. Culhane; T. Kosugi; T. Watanabe

1994-01-01

51

X-ray emission through the stages of stellar activity  

NASA Astrophysics Data System (ADS)

X-ray emission from cool stars is the main tracer for stellar activity. The X-ray luminosity has been established to mark different levels of activity and four orders of magnitude are covered by stars of spectral types M-F. Low spectral resolution provided by X-ray observations of stellar coronae in the past allowed us to determine temperature distributions and elemental abundances by use of atomic databases (listing line emissivities and bremsstrahlung continuum for given temperature structure). The new missions XMM-Newton and Chandra carry X-ray gratings that provide unprecedented spectral resolution, and individual X-ray lines can be resolved. My talk will focus on the potential provided by the measurement of line fluxes. It is possible to determine plasma temperatures and associated densities (thus pressures for constrained temperature regions). The new density measurements can also be used to constrain emitting volumes and scaling laws can be applied to infer structural information. I will show results from a large sample of stellar coronae selected from all stages of activity.

Ness, J.-U.

52

X-RAY EMISSION ANALYSIS: SAMPLE LOSSES DURING EXCITATION  

EPA Science Inventory

Many samples of atmospheric aerosols and biological materials containing volatile or unstable species are now being examined by X-ray emission analysis, and loss of these species by sample heating is a critical consideration. The amount of heat energy deposited in a sample by the...

53

X-ray Emissions Detected From Elusive Cosmic Objects  

NASA Astrophysics Data System (ADS)

A type of celestial object that has long stumped astronomers has been found to emit X-rays, thus proving a theory of how the objects form. Dr. Steven Pravdo of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and other scientists have concluded that these objects, called Herbig Haro objects, are produced by high velocity shocks. Pravdo is the lead author of a paper published in the Oct. 18 issue of the journal Nature. Herbig Haro objects are found in regions where new stars are forming. They are nebulas, or dust and gas clouds. They form when high-velocity gas emitted from young stars collides with clouds of interstellar material. The collision heats the gas in the surrounding nebula to sufficiently high temperatures to produce X-rays. Observations for the past 20 years showed no evidence of X-ray emission from these objects, which are named for astronomers George Herbig and Guillermo Haro. Previous instruments lacked the resolution and sensitivity necessary to 'see' these X-rays. The discovery of the X-ray emissions was possible through the very powerful Advanced CCD Imaging Spectrometer on NASA's Chandra X-ray Observatory, which has been in orbit since 1999. On Oct. 8, 2000, astrophysicists used the instrument to study HH2, one of the brightest and closest Herbig Haro objects in the Orion Nebula. They determined that HH2 contains shock-heated material with a temperature of about 1 million degrees Kelvin. Pravdo and his team used three criteria to rule out the possibility that the emissions came from any other source. First, Chandra's high spatial resolution pinpointed the location of the X-rays at HH2. Second, the X-rays appeared to be covering a region bigger than a star. Third, the temperature of the X-rays was about 1 million degrees, cooler than nearby X-ray stars. One million degrees is about the temperature expected if material moving at about 300 kilometers per second (about 600,000 miles per hour) collides. At this speed, you could go from Los Angeles to San Diego and back in one second. The principal investigator of the Advanced CCD Imaging Spectrometer, Dr. Gordon Garmire of Pennsylvania State University, University Park, is a co-author of the paper. Other co-authors include Drs. Yohko Tsuboi, Yoshitomo Maeda and Eric Feigelson, all from Pennsylvania State University, and Dr. John Bally from the University of Colorado, Boulder. The Advanced CCD Imaging Spectrometer X-ray camera was developed for NASA by Pennsylvania State University and the Massachusetts Institute of Technology, Cambridge, Mass. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. TRW, Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Mass. Images associated with this release are available on the World Wide Web at: http://chandra.harvard.edu AND http://chandra.nasa.gov The Chandra X-ray Observatory is managed for NASA by the Smithsonian Astrophysical Observatory, Cambridge, Mass. JPL is managed for NASA by the California Institute of Technology in Pasadena.

2001-10-01

54

TYPING SUPERNOVA REMNANTS USING X-RAY LINE EMISSION MORPHOLOGIES  

SciTech Connect

We present a new observational method to type the explosions of young supernova remnants (SNRs). By measuring the morphology of the Chandra X-ray line emission in 17 Galactic and Large Magellanic Cloud SNRs with a multipole expansion analysis (using power ratios), we find that the core-collapse SNRs are statistically more asymmetric than the Type Ia SNRs. We show that the two classes of supernovae can be separated naturally using this technique because X-ray line morphologies reflect the distinct explosion mechanisms and structure of the circumstellar material. These findings are consistent with recent spectropolarimetry results showing that core-collapse supernovae explosions are intrinsically more asymmetric.

Lopez, L. A.; Ramirez-Ruiz, E. [Department of Astronomy and Astrophysics, University of California Santa Cruz, 159 Interdisciplinary Sciences Building, 1156 High Street, Santa Cruz, CA 95064 (United States); Badenes, C. [Department of Astrophysical Sciences, Princeton University Peyton Hall, Ivy Lane, Princeton, NJ 08544 (United States); Huppenkothen, D. [Astronomical Institute, 'Anton Pannekoek', University of Amsterdam, P.O. Box 94249, 1090 GE Amsterdam (Netherlands); Jeltema, T. E. [UCO/Lick Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Pooley, D. A., E-mail: lopez@astro.ucsc.ed [Astronomy Department, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States)

2009-11-20

55

EUV and x-ray emission of nonmagnetic catacysmic variables  

SciTech Connect

Recent results are presented and discussed regarding the EUV and X-ray emission of nonmagnetic cataclysmic variables. Emphasis is given to high accretion rate systems (novalike variables and dwarf novae in outburst), and to a number of apparent discrepancies between observations and the theory of the boundary layer between the accretion disk and the surface of the white dwarf. Discussed are EUV and X-ray light curves, dwarf nova oscillations, and spectra, with new and previously unpublished results on SS Cyg and OY Car.

Mauche, C.W.

1997-09-01

56

Soft X-ray emission spectroscopy of polycyclic aromatichydrocarbons  

SciTech Connect

High-resolution CK X-ray emission spectra of polycyclicaromatic hydrocarbons (PAH) were measured using synchrotron radiation.The main peak energies in the PAH X-ray spectra shifted to a higherenergy region as the ratio of hydrogenated outer carbon atoms tothenon-hydrogenated inner carbon atoms increased. Discrete variational(DV)-Xa molecular orbital calculations provided theoretical confirmationthat the spectral features depend on the ratio ofhydrogenated/non-hydrogenated carbon atoms, which suggests that thefeatures around the main peaks provide the information of the degree ofhydrogenation in PAH compounds.

Muramatsu, Yasuji; Tomizawa, Kana; Denlinger, Jonathan D.; Perera, Rupert C.C.

2004-04-02

57

Enhanced hard x-ray emission from microdroplet preplasma  

SciTech Connect

We perform a comparative study of hard x-ray emission from femtosecond laser plasmas in 15 {mu}m methanol microdroplets and Perspex target. The hard x-ray yield from droplet plasmas is {approx_equal}68 times more than that obtained from solid plasmas at 2x10{sup 15} W cm{sup -2}. A 10 ns prepulse at about 5% of the main pulse appears to be essential for hard x-ray generation from droplets. Hot electron temperature of 36 keV is measured from the droplets at 8x10{sup 14} W cm{sup -2}, whereas a three times higher intensity is needed to obtain similar hot electron temperatures from Perspex plasmas. Particle-in-cell simulations with very long scale-length density profiles support experimental observations.

Anand, M.; Kahaly, S.; Ravindra Kumar, G.; Krishnamurthy, M.; Sandhu, A.S.; Gibbon, P. [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India); JILA, University of Colorado, Boulder, Colorado 80303 (United States); John-von-Neumann Institute for Computing, ZAM, Forschungszentrum Juelich, D-52425 Juelich (Germany)

2006-05-01

58

X-ray Emission from Thunderstorms and Lightning  

ScienceCinema

How lightning is initiated in the relatively low electric fields inside thunderclouds and how it can then propagate for tens of kilometers through virgin air are two of the great unsolved problems in the atmospheric sciences. Until very recently it was believed that lightning was entirely a conventional discharge, involving only low-energy (a few eV) electrons. This picture changed completely a few years ago with the discovery of intense x-ray emission from both natural cloud-to-ground lightning and rocket-triggered lightning. This energetic emission cannot be produced by a conventional discharge, and so the presence of x-rays strongly implies that runaway breakdown plays a role in lightning processes. During runaway breakdown, electrons are accelerated through air to nearly the speed of light by strong electric fields. These runaway electrons then emit bremsstrahlung x-rays and gamma-rays during collisions with air. Indeed, the x-ray and gamma-ray emission produced by runaway breakdown near the tops of thunderstorms is bright enough to be seen from outer space, 600 km away. As a result, the physics used for decades to describe thunderstorm electrification and lightning discharges is incomplete and needs to be revisited.

59

On X-ray Emission from Highly Loaded Hydrides  

Microsoft Academic Search

X-ray emission (1-2 keV) has been observed in various experiments using electrolytic or plasma methods for loading of hydride targets such as Pd-D to atom ratios > 0.8. Intensities vary from very low-level emission up to laser-like focused beams, depending on experimental conditions(A.G. Lipson et al, JETP Letters, (submitted)). Bremsstralung during thermalization of energetic alphas\\/protons created by nuclear reactions in

George H. Miley; Heinrich Hora; Nie Luo; Andrei Lipson

2004-01-01

60

Stellar X-ray Emission in the Orion Nebula Region  

NASA Astrophysics Data System (ADS)

We present results from two comprehensive imaging X-ray surveys of the Orion Nebula star-forming complex. We have analyzed three deep ROSAT High Resolution Imager (HRI) pointings of a 0.8 square degree region around the Trapezium. In addition, we have completed our analysis of 17 Einstein Imaging Proportional Counter and 6 Einstein HRI fields covering roughly 4.5 square degrees, also centered on the Trapezium. In total, more than 450 distinct sources of emission brighter than L_X ~ 10(30) erg s(-1) have been detected; ~ 320 of these have been identified with certain or probable cluster members. The vast majority of the X-ray sources are associated with intermediate and low-mass pre-main sequence (PMS) cluster members. No correlation between X-ray activity and rotation is evident among the handful of stars with measured rotational velocity and/or period. The low-mass PMS stars show signs of saturated X-ray activity, with relative X-ray luminosity L_X/L_bol ~ 10(-3) . We compare these results with those obtained in other star-forming regions such as rho Ophiuchi, Taurus-Aurigae, and Chamaeleon I. Nearly all the O and B-type stars observed by ROSAT were detected with L_X/L_bol in the range 10(-7.3) to 10(-5.3) . Also detected by ROSAT are 5 sources whose only candidate optical counterparts are main-sequence B6-A5 stars. These stars are thought to be incapable of producing detectable X-ray emission. Since only ~ 20% of the observed B6-A5 stars are detected, we argue that the observed emission is probably not produced by the B6-A5 stars but, rather, in the coronae of unseen late-type companions. An X-ray light-curve analysis has been performed on both the Einstein and ROSAT data sets, revealing a total of ~ 25 flaring events. Over the course of the Einstein and ROSAT observations, emission from a number of sources was measured many times, allowing us to examine long-term variability on the time scale of a few months between individual Einstein or ROSAT exposures and on the time scale of a decade between the two missions. Research support has been provided by NASA through grants NAGW-2698, NAG5-1608, and NAG5-1610.

Gagne, M.; Caillault, J.-P.; Stauffer, J. R.

1993-12-01

61

Novel X-Ray Source Using Rear Side X-Ray Emission from the Foil Target  

Microsoft Academic Search

Development of a novel and compact x-ray source is described. The first direct evidence of L-shell x-ray transport through an Al foil target was determined by observing the soft x-ray spectra from the rear side and this is explained in terms of ionization burnthrough. In contrast to other work, the x-ray spectral profile from the rear side of the target

H. Hirose; K. Ando; K. Miyazawa; T. Hara; K. Kodate; Y. Aoyagi

1996-01-01

62

Novel x-ray source using rear side x-ray emission from the foil target  

Microsoft Academic Search

Development of a novel and compact x-ray source is described. The first direct evidence of L-shell x-ray transport through an Al foil target was determined by observing the soft x-ray spectra from the rear side and this is explained in terms of ionization hurnthrough. Contrary to the other works, the x-ray spectral protile from the rear side of the target

H. Hirose; K. Ando; Y. Aoyagi

1996-01-01

63

X-ray emission and the winds of cataclysmic variables  

SciTech Connect

X-ray and ultraviolet observations of cataclysmic variable stars reveal a variety of exotic behavior - pulsations, winds, and episodic outbursts - are these related, what do they tell us about the nature of the outburst, about the environment of the accreting white dwarf. The author summarizes the observed changes in the x-ray and uv continuum and spectral features through the outbursts of the dwarf novae. The author then discusses how the modeling of these data have refined our ideas about the location and nature of the emissions, and the source of the outbursts. The author shows how comparisons of the x-ray and uv properties of cataclysmic variables with similar phenomena in other astronomical systems - the solar corona, OB stars, and Be stars - suggest ways in which the x-ray and uv emissions in CVs may be related, and point to further, specific observations that would elucidate our understanding of the behavior and role of the white dwarf in the outburst. 26 references.

Cordova, F.A.

1985-01-01

64

Determination of total x-ray absorption coefficient using non-resonant x-ray emission  

PubMed Central

An alternative measure of x-ray absorption spectroscopy (XAS) called inverse partial fluorescence yield (IPFY) has recently been developed that is both bulk sensitive and free of saturation effects. Here we show that the angle dependence of IPFY can provide a measure directly proportional to the total x-ray absorption coefficient, µ(E). In contrast, fluorescence yield (FY) and electron yield (EY) spectra are offset and/or distorted from µ(E) by an unknown and difficult to measure amount. Moreover, our measurement can determine µ(E) in absolute units with no free parameters by scaling to µ(E) at the non-resonant emission energy. We demonstrate this technique with measurements on NiO and NdGaO3. Determining µ(E) across edge-steps enables the use of XAS as a non-destructive measure of material composition. In NdGaO3, we also demonstrate the utility of IPFY for insulating samples, where neither EY or FY provide reliable spectra due to sample charging and self-absorption effects, respectively.

Achkar, A. J.; Regier, T. Z.; Monkman, E. J.; Shen, K. M.; Hawthorn, D. G.

2011-01-01

65

"X-Ray Transients in Star-Forming Regions" and "Hard X-Ray Emission from X-Ray Bursters"  

NASA Astrophysics Data System (ADS)

This grant funded work on the analysis of data obtained with the Burst and Transient Experiment (BATSE) on the Compton Gamma-Ray Observatory. The goal of the work was to search for hard x-ray transients in star forming regions using the all-sky hard x-ray monitoring capability of BATSE. Our initial work lead to the discovery of a hard x-ray transient, GRO J1849-03. Follow-up observations of this source made with the Wide Field Camera on BeppoSAX showed that the source should be identified with the previously known x-ray pulsar GS 1843-02 which itself is identified with the x-ray source X1845-024 originally discovered with the SAS-3 satellite. Our identification of the source and measurement of the outburst recurrence time, lead to the identification of the source as a Be/X-ray binary with a spin period of 94.8 s and an orbital period of 241 days. The funding was used primarily for partial salary and travel support for John Tomsick, then a graduate student at Columbia University. John Tomsick, now Dr. Tomsick, received his Ph.D. from Columbia University in July 1999, based partially on results obtained under this investigation. He is now a postdoctoral research scientist at the University of California, San Diego.

Halpern, Jules P.; Kaaret, Philip

1999-09-01

66

An optimal design of X-ray target for uniform X-ray emission from an electronic brachytherapy system  

NASA Astrophysics Data System (ADS)

We present a novel design of an X-ray target to deliver uniform dose from an electronic brachytherapy system (EBS). This design comprises of a combination of both the reflection- and transmission-type target geometries. Monte-Carlo simulation code MCNP5 has been employed for the calculation of angular distribution of the X-ray intensity produced from various morphologies of X-ray targets. The simulation results reveal that the combinatorial target-assembly is promising and effective in achieving uniformity of X-ray emission over the entire space of solid angle of 4? in comparison to a transmission-type target that produces X-rays mainly in the forward direction and a reflection-type target that generates X-rays mostly in the backward direction. As a direct consequence of the uniformity of X-ray emission, the combinatorial target-assembly can impart a uniform dose distribution which makes it suitable as a target of an X-ray tube for EBS.

Ihsan, Aamir; Heo, Sung Hwan; Kim, Hyun Jin; Kang, Chang Mu; Cho, Sung Oh

2011-05-01

67

X-ray emission from the outer planets: Albedo for scattering and fluorescence of solar X rays  

Microsoft Academic Search

Soft X-ray emission has been observed from the low-latitude “disk” of both Jupiter and Saturn as well as from the auroral regions of these planets. The disk emission as observed by ROSAT, the Chandra X-Ray Observatory, and XMM-Newton appears to be uniformly distributed across the disk and to be correlated with solar activity. These characteristics suggest that the disk X

T. E. Cravens; J. Clark; A. Bhardwaj; R. Elsner; J. H. Waite Jr; A. N. Maurellis; G. R. Gladstone; G. Branduardi-Raymont

2006-01-01

68

X-ray emission from cataclysmic variables with accretion disks. I - Hard X-rays. II - EUV\\/soft X-ray radiation  

Microsoft Academic Search

Theoretical models explaining the hard-X-ray, soft-X-ray, and EUV emission of accretion-disk cataclysmic variables in terms of the disk boundary layer (DBL) are developed on the basis of a survey of the published observational data. The data are compared with model predictions in graphs for systems with high or low (greater than or less than 10-Pg\\/s) accretion rates. Good agreement is

J. Patterson; J. C. Raymond

1985-01-01

69

Nonthermal X-ray emission from winds of OB supergiants  

SciTech Connect

The mechanisms responsible for the hard X-ray emission of OB supergiants (OBSGs) are investigated theoretically, modifying the periodic-shock model of Lucy (1982). The physical processes discussed include (1) the particle acceleration (PA) mechanism and its effect on the structure of individual shocks, (2) the energy cutoff and spectral index of the relativistic electrons and ions, and (3) the efficiency of PA by shocks and its implications for the number densities of relativistic particles. The model is used to predict the spectrum and intensity of the dominant nonthermal X-ray emission source from OBSGs, and the results are shown to be in good agreement with Einstein Observatory Solid-State Spectrometer observations of three OBSGs in Orion (Cassinelli and Swank, 1983). It is inferred that the surface magnetic fields of OBSGs are no greater than a few G, and that the PA rates are significantly lower than generally predicted for collisionless astrophysical shocks. 66 refs.

Chen, W.; White, R.L. (Johns Hopkins Univ., MD (USA) Space Telescope Science Institute, Baltimore, MD (USA))

1991-01-01

70

Innovations in X-ray-induced electron emission spectroscopy (XIEES)  

SciTech Connect

Currently, a pressing need has arisen for controlling the local atomic and electron structure of materials irrespective of their aggregate state. Efficient approaches to the studies of short-range order are based on phenomena accompanied by interference of secondary electrons excited by primary X-ray radiation. The set of such approaches are commonly referred to as the X-ray absorption fine structure (XAFS) methods. In reality, the XAFS methods are based on the use of synchrotron radiation and applied to structural studies in two modes of measurements, transmission analysis and recording of secondary effects. Only two such effects-specifically, the X-ray fluorescence an d X-ray-induced electron emission effect-are commonly discussed. Access to synchrotron accelerators is problematic for most researchers, so a demand is created for designing laboratory systems that make direct access possible. Since the power of laboratory systems is much lower than that of synchrotrons, it is essential to use much more efficient detectors of secondary electrons. In addition, it is of interest to analyze energy characteristics with a high spatial resolution. Channel multipliers and multichannel boards are incapable of providing such a possibility. For this reason, an improved electron detector has been developed to analyze the photoemission effect in an accelerating field.

Pogrebitsky, K. Ju., E-mail: mischar@mail.ioffe.ru; Sharkov, M. D. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2010-06-15

71

Diffuse X-Ray Emission from M101  

NASA Astrophysics Data System (ADS)

The total 0.45-1.0 keV luminosity of M101 is 3.2×1039 ergs s-1, of which 2.3×1039 ergs s-1 is due to diffuse emission. (Chandra observes only ~60% of the diffuse emission observed by ROSAT because of its superior point-source detection.) Of the diffuse emission seen by Chandra, no more than 6% can be due to luminous unresolved point sources, such as X-ray binaries, and ~10% is likely due to dwarf stars. The diffuse emission traces the spiral arms and is roughly correlated with the H? and far-UV emission. The radial distribution closely follows the optical profile. The bulk of the diffuse emission is characterized by a two-thermal component spectrum with kT=0.20 and 0.75 keV, and the ratio of the emission measures of the two components is roughly constant as a function of both radius and surface brightness. The softer component has a sufficiently large covering factor that the bulk of the emission is likely extraplanar. We find no evidence of an extended axisymmetric X-ray halo, suggesting that any such halo has a strength much smaller than current predictions.

Kuntz, K. D.; Snowden, S. L.; Pence, W. D.; Mukai, K.

2003-05-01

72

The Evolution of X-Ray Emission in Young Stars  

NASA Astrophysics Data System (ADS)

The evolution of magnetic activity in late-type stars is part of the intertwined rotation-age-activity relation, which provides an empirical foundation to the theory of magnetic dynamos. We study the age-activity relation in the pre-main-sequence (PMS) regime, for the first time using mass-stratified subsamples. The effort is based on the Chandra Orion Ultradeep Project (COUP), which provides very sensitive and homogenous X-ray data on a uniquely large sample of 481 optically well-characterized low-extinction low-mass members of the Orion Nebula Cluster, for which individual stellar masses and ages could be determined. More than 98% of the stars in this sample are detected as X-ray sources. Within the PMS phase for stellar ages in the range ~0.1-10 Myr, we establish a mild decay in activity with stellar age ? roughly as LX~?-1/3. On longer timescales, when the Orion stars are compared to main-sequence stars, the X-ray luminosity decay law for stars in the 0.5 MsolarX-ray luminosity LX/Lbol and the X-ray surface flux are considered as activity indicators, the decay law index is similarly slow for the first 1-100 Myr but accelerates for older stars. The magnetic activity history for M stars with masses 0.1 MsolarX-ray luminosity, and even a mild increase in LX/Lbol and FX, is seen over the 1-100 Myr range, though the X-ray emission does decay over long timescales on the main sequence. Together with COUP results on the absence of a rotation-activity relation in Orion stars, we find that the activity-age decay is strong across the entire history of solar-type stars but is not attributable to rotational deceleration during the early epochs. A combination of tachocline and distributed convective dynamos may be operative in young solar-type stars. The results for the lowest mass stars are most easily understood by the dominance of convective dynamos during both the PMS and main-sequence phases.

Preibisch, Thomas; Feigelson, Eric D.

2005-10-01

73

X-RAY EMISSION FROM THE SOMBRERO GALAXY: DISCRETE SOURCES  

SciTech Connect

We present a study of discrete X-ray sources in and around the bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival Chandra observations with a total exposure of {approx}200 ks. With a detection limit of L{sub X} {approx} 10{sup 37} erg s{sup -1} and a field of view covering a galactocentric radius of {approx}30 kpc (11.'5), 383 sources are detected. Cross-correlation with Spitler et al.'s catalog of Sombrero globular clusters (GCs) identified from HST/ACS observations reveals 41 X-ray sources in GCs, presumably low-mass X-ray binaries (LMXBs). Metal-rich GCs are found to have a higher probability of hosting these LMXBs, a trend similar to that found in elliptical galaxies. On the other hand, the four most luminous GC LMXBs, with apparently super-Eddington luminosities for an accreting neutron star, are found in metal-poor GCs. We quantify the differential luminosity functions (LFs) for both the detected GC and field LMXBs, whose power-law indices ({approx}1.1 for the GC-LF and {approx}1.6 for field-LF) are consistent with previous studies for elliptical galaxies. With precise sky positions of the GCs without a detected X-ray source, we further quantify, through a fluctuation analysis, the GC-LF at fainter luminosities down to 10{sup 35} erg s{sup -1}. The derived index rules out a faint-end slope flatter than 1.1 at a 2{sigma} significance, contrary to recent findings in several elliptical galaxies and the bulge of M31. On the other hand, the 2-6 keV unresolved emission places a tight constraint on the field LF, implying a flattened index of {approx}1.0 below 10{sup 37} erg s{sup -1}. We also detect 101 sources in the halo of Sombrero. The presence of these sources cannot be interpreted as galactic LMXBs whose spatial distribution empirically follows the starlight. Their number is also higher than the expected number of cosmic active galactic nuclei (52 {+-} 11 [1{sigma}]) whose surface density is constrained by deep X-ray surveys. We suggest that either the cosmic X-ray background is unusually high in the direction of Sombrero, or a distinct population of X-ray sources is present in the halo of Sombrero.

Li Zhiyuan; Jones, Christine; Forman, William R.; Kraft, Ralph P.; Stefano, Rosanne Di [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Spitler, Lee R. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Tang, Shikui; Wang, Q. Daniel [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Gilfanov, Marat [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str 1, 85741 Garching bei Muenchen (Germany); Revnivtsev, Mikhail, E-mail: zyli@cfa.harvard.ed [Excellence Cluster Universe, Technische Universitaet Muenchen, Boltzmannstr. 2, 85748 Garching (Germany)

2010-10-01

74

Statistical data of X-ray emission from laboratory sparks  

NASA Astrophysics Data System (ADS)

In this study we present a summary of the data of 1331 long laboratory sparks in atmospheric pressure intended for a statistical analysis. A 2 MV, 17kJ Marx generator were used to generate 1.2/52?s shape pulses positive and negative polarity. The generator was connected to a spark gap with cone-shaped electrodes. The distance between high-voltage and grounded electrodes was 1.08 meters. Breakdown voltage between electrodes was about 1MV. X-rays have been detected during the development of the discharge channel. The currents through the grounded electrode and through the high-voltage electrode were recorded separately and simultaneously with the voltage and the X-ray signal. X-rays were registered by two LaBr3(Ce+) scintillation detectors in different positions with respect to the forming discharge channel. Detector D1 was placed immediately under the grounded electrode at 15cm distance. Detector D2 was placed at horizontal distances of 143cm and 210cm, at mid-gap height. We also used lead shields of 1.5, 3, and 4 mm thickness for radiation attenuation measurements. For detector collimation we used shields up to 2 cm thickness. Also no metallic objects with pointed surfaces were present within 2 m from the spark gap. Typical plot of positive discharge presented in Figure 1a. Table 1 shows the summary of the X-ray registrations. Signal detection occurred significantly more for positive polarity discharges than for negative. This dependence was observed for both detectors. For detector D2 the probability of X-ray registration decreased proportional to 1/d2 with increasing the distance d to the breakdown gap from 1m43 to 2m10. Detailed energy spectra and time distribution of X-ray emission were obtained; see for example Fig. 1b. For both polarities of the high voltage, the X-rays only occurred when there was a current at the cathode.

Kochkin, P.; Deursen, D. V.

2011-12-01

75

Unveiling GRB Hard X-ray Afterglow Emission  

NASA Astrophysics Data System (ADS)

Despite the enormous progress occurred in the last 15 years, the Gamma-Ray Bursts (GRB) phenomenon is still far to be fully understood. One of the most important open issues that have still to be settled is the afterglow emission above 10 keV, which is almost completely unexplored. This is due to the lack of sensitive enough detectors operating in this energy band. The only detection, by the BeppoSAX/PDS instrument (15-200 keV), of hard X-ray emission from a GRB (the very bright GRB 990123), combined with optical and radio observations, seriously challenged the standard scenario in which the dominant mechanism is synchrotron radiation produced in the shock of a ultra-relativistic fireball with the ISM, showing the need of a substantial revision of present models. In this respect, next generation X-ray telescopes capable to focus X-rays up to several tens of keV, which will fly in the near future on board the NuSTAR and ASTRO-H missions, and gamma-ray Laue lenses cabable to focus soft gamma-rays up to several hundreds of keV, currently under development, will provide, through follow-up observations of bright GRBs detected and localized by GRB dedicated experiments, an important breakthrough in the GRB field.

Amati, L.

2011-09-01

76

Fine structure splitting in argon x-ray emission spectra  

SciTech Connect

X-ray emission spectrometry is a method of growing importance for a large number of problems in physics and applications in other fields, e.g. investigations of heavy ion sources, plasma diagnostics in connection with fusion research, astrophysics and basic research in other fields of physics. However, there is a lack of data required for the interpretation of spectra obtained especially in the region of highly ionized atoms. Since this is mainly caused by experimental difficulties, theoretical calculations are required to provide data that are necessary for the current studies. Therefore, the authors developed a program package to calculate various atomic properties of neutral and ionized atoms. In the present paper they analyze, how the fine structure splitting influences the x-ray spectrum emitted by atoms of a given element at various stages of ionization.

Reiche, I.; Fritzsche, S.; Musiol, G.; Zschornack, G. (Technische Univ. Dresden (Germany))

1989-05-01

77

The hard X-ray emission of Centaurus A  

NASA Astrophysics Data System (ADS)

Context. The radio galaxy Cen A has been detected all the way up to the TeV energy range. This raises the question about the dominant emission mechanisms in the high-energy domain. Aims: Spectral analysis allows us to put constraints on the possible emission processes. Here we study the hard X-ray emission, in order to distinguish between a thermal and a non-thermal inverse Compton process. Methods: Using hard X-ray data provided by INTEGRAL, we determined the cut-off of the power-law spectrum in the hard X-ray domain (3-1000 keV). In addition, INTEGRAL data are used to study the spectral variability. The extended emission detected in the gamma-rays by Fermi/LAT is investigated using the data of the spectrometre SPI in the 40-1000 keV range. Results: The hard X-ray spectrum of Cen A shows a significant cut-off at energies EC = 434 {+106 atop -73} keV with an underlying power-law of photon index ? = 1.73 ± 0.02. A more physical model of thermal Comptonisation (compPS) gives a plasma temperature of kTe = 206 ± 62 keV within the optically thin corona with Compton parameter y = 0.42 {+0.09 atop -0.06}. The reflection component is significant at the 1.9? level with R = 0.12 {+0.09 atop -0.10}, and a reflection strength R > 0.3 can be excluded on a 3? level. Time resolved spectral studies show that the flux, absorption, and spectral slope varied in the range f3-30 keV = 1.2-9.2 × 10-10 erg cm-2 s-1, NH = 7-16 × 1022 cm-2, and ? = 1.75-1.87. Extending the cut-off power-law or the Comptonisation model to the gamma-ray range shows that they cannot account for the high-energy emission. On the other hand, a broken or curved power-law model can also represent the data, therefore a non-thermal origin of the X-ray to GeV emission cannot be ruled out. The analysis of the SPI data provides no sign of significant emission from the radio lobes and gives a 3? upper limit of f40-1000 keV ? 1.1 × 10-3 ph cm-2 s-1. Conclusions: While gamma-rays, as detected by CGRO and Fermi, are caused by non-thermal (jet) processes, the main process in the hard X-ray emission of Cen A is still not unambiguously determined, since it is either dominated by thermal inverse Compton emission or by non-thermal emission from the base of the jet. Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland and Spain), the Czech Republic, and Poland and with participation of Russia and the US.

Beckmann, V.; Jean, P.; Lubi?ski, P.; Soldi, S.; Terrier, R.

2011-07-01

78

Hard X-ray Emission by Resonant Compton Upscattering in Magnetars  

NASA Astrophysics Data System (ADS)

Flat spectrum, non-thermal X-ray quiescent emission extending between 10 keV and around 150 keV has been seen in a number of magnetars by RXTE, INTEGRAL, Suzaku and Fermi-GBM. For inner magnetospheric models of such hard X-ray emission, resonant Compton upscattering is anticipated to be the most efficient process for generating continuum radiation. This is because the scattering becomes resonant at the cyclotron frequency, and the effective cross section exceeds the classical Thomson value by over two orders of magnitude, thereby enhancing the efficiency of continuum production and the cooling of relativistic electrons. We present angle-dependent hard X-ray upscattering model spectra for uncooled monoenergetic relativistic electrons injected in inner regions of pulsar magnetospheres. These spectra are integrated over closed field lines and obtained for different observing perspectives. The spectral cut-off energies are critically dependent on the observer viewing angles and electron Lorentz factor. We find that electrons with energies less than around 15 MeV will emit most of their radiation below 250 keV, consistent with the observed turnovers in magnetar hard X-ray tails. Moreover, electrons of higher energy still emit most of the radiation below 1 MeV, except for very select viewing perspectives that sample tangents to field lines, thereby making it difficult to observe signals extending into the Fermi-LAT band. Our spectral computations use, for the first time, a new Sokolov and Ternov (ST) formulation of the QED Compton scattering cross section in strong magnetic fields. Such an ST formalism is formally correct for treating spin-dependent effects that are important in the cyclotron resonance.

Wadiasingh, Zorawar; Baring, M. G.; Gonthier, P. L.

2013-04-01

79

Capturing ultrafast molecular dynamics with time-resolved x-ray absorption, x-ray emission, and x-ray scattering  

NASA Astrophysics Data System (ADS)

Ultrafast, time-resolved, laser-pump, x-ray-probe experiments are powerful tools for understanding and controlling the behavior of matter at the molecular level. Transient structural changes, both geometric and electronic, of single molecules after excitation by a laser pulse can be probed with high resolution and within complex or disordered environments, such as gases and liquids, taking advantage of the superior spatial resolution, elemental specificity and penetration power of x-rays. Third generation synchrotron sources, particularly the Advanced Photon Source (APS), provide x-rays with a unique combination of properties that are well suited for precision time-resolved measurements. These include a high flux (10^13 photons/second/0.01% bandwidth) that is distributed in short pulses (˜100 ps) with moderate intensity (˜10^6 photons/pulse) at a high repetition rate (MHz). Over the last decade laser-pump, x-ray-probe studies have been carried out at synchrotrons but a major challenge has been the low repetition rate (kHz) of standard amplified lasers resulting in underutilization of the synchrotron's high flux. This limitation has recently been removed with the installation of a high repetition rate laser system at 7ID-D at the APS. In this talk I will discuss measurements on the light-induced switching of Fe(II) complexes at 3.26 MHz pump-probe repetition rates which efficiently use the available x-ray flux. This efficiency enabled the complementary techniques x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES) and liquid phase x-ray scattering (XRS) to be used simultaneously to collect information on the structural and electronic dynamics on the picosecond time scale.

March, Anne Marie

2012-06-01

80

Optical Emission of the Black Hole X-Ray Transient MAXI J1659-152 during Quiescence  

NASA Astrophysics Data System (ADS)

We report on the optical detection of the black hole X-ray transient MAXI J1659-152 during its quiescent state. By using the Canada-France-Hawaii Telescope, we observed MAXI J1659-152 about seven months after the end of an X-ray outburst. The optical counterpart of MAXI J1659-152 is clearly detected with an r'-band magnitude of 23.6-23.8. The detection confirms that the optical emission of MAXI J1659-152 during quiescence is relatively bright compared to other black hole X-ray transients. This implies that the distance to MAXI J1659-152 is 4.6-7.5 kpc for an M2 dwarf companion star or 2.3-3.8 kpc for an M5 dwarf companion star. By comparing with other measurements, an M2 dwarf companion is more likely.

Kong, Albert K. H.

2012-12-01

81

OPTICAL EMISSION OF THE BLACK HOLE X-RAY TRANSIENT MAXI J1659-152 DURING QUIESCENCE  

SciTech Connect

We report on the optical detection of the black hole X-ray transient MAXI J1659-152 during its quiescent state. By using the Canada-France-Hawaii Telescope, we observed MAXI J1659-152 about seven months after the end of an X-ray outburst. The optical counterpart of MAXI J1659-152 is clearly detected with an r'-band magnitude of 23.6-23.8. The detection confirms that the optical emission of MAXI J1659-152 during quiescence is relatively bright compared to other black hole X-ray transients. This implies that the distance to MAXI J1659-152 is 4.6-7.5 kpc for an M2 dwarf companion star or 2.3-3.8 kpc for an M5 dwarf companion star. By comparing with other measurements, an M2 dwarf companion is more likely.

Kong, Albert K. H., E-mail: akong@phys.nthu.edu.tw [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2012-12-01

82

NEUTRON STAR RADIUS MEASUREMENT WITH THE QUIESCENT LOW-MASS X-RAY BINARY U24 IN NGC 6397  

SciTech Connect

This paper reports the spectral and timing analyses of the quiescent low-mass X-ray binary (qLMXB) U24 observed during five archived Chandra/ACIS exposures of the nearby globular cluster NGC 6397, for a total of 350 ks. We find that the X-ray flux and the parameters of the hydrogen atmosphere spectral model are consistent with those previously published for this source. On short timescales, we find no evidence of aperiodic intensity variability, with 90% confidence upper limits during five observations ranging between <8.6% rms and <19% rms, in the 0.0001-0.1 Hz frequency range (0.5-8.0 keV); and no evidence of periodic variability, with maximum observed powers in this frequency range having a chance probability of occurrence from a Poisson-deviated light curve in excess of 10%. We also report the improved neutron star (NS) physical radius measurement, with statistical accuracy of the order of {approx}10%: R{sub NS} = 8.9{sup +0.9}{sub -0.6} km for M{sub NS} = 1.4 M{sub sun}. Alternatively, we provide the confidence regions in mass-radius space as well as the best-fit projected radius R{sub {infinity}} = 11.9{sup +1.0}{sub -0.8} km, as seen by an observer at infinity. The best-fit effective temperature, kT{sub eff} = 80{sup +4}{sub -5} eV, is used to estimate the NS core temperature which falls in the range T{sub core} = (3.0-9.8) x 10{sup 7} K, depending on the atmosphere model considered. This makes U24 the third most precisely measured NS radius among qLMXBs, after those in {omega} Cen and M13.

Guillot, Sebastien; Rutledge, Robert E. [Department of Physics, McGill University, 3600 rue University, Montreal, QC H3A-2T8 (Canada); Brown, Edward F., E-mail: guillots@physics.mcgill.ca, E-mail: rutledge@physics.mcgill.ca [Department of Physics and Astronomy, Michigan State University, 3250 Biomedical Physical Science Building, East Lansing, MI 48824-2320 (United States)

2011-05-10

83

DISCOVERY OF A CANDIDATE QUIESCENT LOW-MASS X-RAY BINARY IN THE GLOBULAR CLUSTER NGC 6553  

SciTech Connect

This paper reports the search for quiescent low-mass X-ray binaries (qLMXBs) in the globular cluster (GC) NGC 6553 using an XMM-Newton observation designed specifically for that purpose. We spectrally identify one candidate qLMXB in the core of the cluster, based on the consistency of the spectrum with a neutron star H-atmosphere model at the distance of NGC 6553. Specifically, the best-fit radius found using the three XMM European Photon Imaging Camera spectra is R{sub NS} = 6.3{sub -}0{sub .8}{sup +2.3} km (for M{sub NS} = 1.4 M{sub sun}) and the best-fit temperature is kT{sub eff} = 136{sub -34}{sup +21} eV. Both physical parameters are in accordance with typical values of previously identified qLMXBs in GC and in the field, i.e., R{sub NS} {approx} 5-20 km and kT{sub eff} {approx} 50-150 eV. A power-law (PL) component with a photon index {Gamma} = 2.1{sup +0.5}{sub -0.8} is also required for the spectral fit and contributes {approx}33% of the total flux of the X-ray source. A detailed analysis supports the hypothesis that the PL component originates from nearby sources in the core, unresolved with XMM. The analysis of an archived Chandra observation provides marginal additional support to the stated hypothesis. Finally, a catalog of all the sources detected within the XMM field of view is presented here.

Guillot, Sebastien; Rutledge, Robert E. [Department of Physics, McGill University, 3600 rue University, Montreal, QC H3A-2T8 (Canada); Brown, Edward F. [Department of Physics and Astronomy, Michigan State University, 3250 Biomedical Physical Science Building, East Lansing, MI 48824-2320 (United States); Pavlov, George G. [Department of Physics and Astronomy, Pennsylvania State University, 512 Davey Lab, University Park, PA 16802 (United States); Zavlin, Vyacheslav E., E-mail: guillots@physics.mcgill.ca, E-mail: rutledge@physics.mcgill.ca [Space Science Laboratory, Universities Space Research Association, NASA MSFC VP62, Huntsville, AL 35805 (United States)

2011-09-10

84

X-ray studies of quasars with the Einstein Observatory. IV X-ray dependence on radio emission  

SciTech Connect

The X-ray properties of a sample of 114 radio-loud quasars observed with the Einstein Observatory are examined, and the results are compared with those obtained from a large sample of radio-quiet quasars. The results of statistical analysis of the dependence of X-ray luminosity on combined functions of optical and radio luminosity show that the dependence on both luminosities is important. However, statistically significant differences are found between subsamples of flat radio spectra quasars and steep radio spectra quasars with regard to dependence of X-ray luminosity on only radio luminosity. The data are consistent with radio-loud quasars having a physical component, not directly related to the optical luminosity, which produces the core radio luminosity plus extra X-ray emission. 65 references.

Worrall, D.M.; Tananbaum, H.; Giommi, P.; Zamorani, G.

1987-02-01

85

Hard X-Ray Emission from Low-Mass X-Ray Binaries  

Microsoft Academic Search

We report on Rossi X-Ray Timing Explorer observations of four type I X-ray bursters, namely, 1E 1724-3045, GS 1826-238, SLX 1735-269, and KS 1731-260. The first three were in a low state, with 1-200 keV X-ray luminosities in the range ~0.05-0.1LEdd (LEdd: Eddington luminosity for a neutron star, LEdd=2.5×1038 ergs s-1), whereas KS 1731-260 was in a high state, with

D. Barret; J. F. Olive; L. Boirin; C. Done; G. K. Skinner; J. E. Grindlay

2000-01-01

86

X-ray optics for emission line X-ray source diffraction enhanced systems  

Microsoft Academic Search

Diffraction-enhanced X-ray imaging (DEI) is one of a class of imaging techniques developed at a synchrotron that is based on contrast mechanisms other than absorption. This method uses perfect crystal optics to prepare and analyze beams that traverse the object imaged. The combination of a highly collimated beam along with an analyzer gives such system sensitivity to X-ray refraction and

D. Chapman; I. Nesch; M. O. Hasnah; T. I. Morrison

2006-01-01

87

Low Energy Ga Ion Beams Bombardment onside Insulating Materials and X-ray Emission  

Microsoft Academic Search

X-ray spectra from the surface of insulating samples were measured using a 30 kV Ga+ focused ion beam instrument equipped with an energy dispersive X-ray spectrometer, showing an intense emission of low energy X-rays from insulating materials such as Al-K and O-K of Al2O3. This low energy ion induced X-ray emissions (LIIXE) from insulating materials is expected as a new

Masaki Takeguchi; Renchao Che; Minghui Song; Kazuo Furuya

2007-01-01

88

X-ray Emission From Planets Venus and Mars: Theoretical Model and Numerical Simulations  

Microsoft Academic Search

Recently X-ray emission from non-magnetic planets Venus and Mars have been discovered by Chandra X-ray telescopes [1,2]. Analysis of observational data shows that either charge exchange model or fluorescent scattering of solar x-rays cannot explain the whole set of observational data. The premise of this paper is that x-ray emission of both planets is a combination of line k-shell radiation

P. Bryans; V. D. Shapiro; R. Bingham; M. Tourner

2003-01-01

89

X-ray Emission from Planets Venus and Mars. Theoretical Model and Numerical Simulations  

Microsoft Academic Search

Recently X-ray emission from non-magnetic planets Venus and Mars have been discovered by Chandra X-ray telescopes [1,2]. Analysis of observational data shows that either charge exchange model or fluorescent scattering of solar x-rays cannot explain the whole set of observational data. The premise of this paper is that x-ray emission of both planets is a combination of line k-shell radiation

Paul Bryans; Kevin Quest; Vitali Shapiro; Robert Bingham; Martin Torney

2003-01-01

90

Solar X-ray physics  

SciTech Connect

Research on solar X-ray phenomena performed by American scientists during 1987-1990 is reviewed. Major topics discussed include solar images observed during quiescent times, the processes observed during solar flares, and the coronal, interplanetary, and terrestrial phenomena associated with solar X-ray flares. Particular attention is given to the hard X-ray emission observed at the start of the flare, the energy transfer to the soft X-ray emitting plasma, the late resolution of the flare as observed in soft X-ray, and the rate of occurrence of solar flares as a function of time and latitude. Pertinent aspects of nonflaring, coronal X-ray emission and stellar flares are also discussed. 175 refs.

Bornmann, P.L. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

91

Hard X-Ray Emission from Elliptical Galaxies and Its Contribution to the X-Ray Background.  

PubMed

We explore the implications of the discovery of hard, power-law X-ray sources in the spectra of nearby elliptical galaxies for the origin of the X-ray background (XRB). The spectra of these sources are consistent with models of thermal bremsstrahlung emission from low radiative efficiency accretion flows around central supermassive black holes and are unique in that they approximately match the spectrum of the hard XRB. If such sources, with luminosities consistent with those observed in nearby elliptical galaxies, are present in most early-type galaxies, then their integrated emission may contribute significantly to the XRB. These sources may also contribute to the hard source counts detected in deep X-ray surveys. PMID:10566990

Di Matteo T; Allen

1999-12-10

92

Hard x-ray emission from galactic black hole candidates  

SciTech Connect

This dissertation describes observations of high-energy (10 keV-1 MeV) X-rays emitted by three objects in our Galaxy which may be black holes in binary star systems. The X-rays are believed to be produced by viscous heating of matter flowing into the hole. All of the observations were made with an array of inorganic scintillation counters on the HEAO-1 satellite in 1977 and 1978. The best-known of these sources, Cygnus X-1, is very intense (> 3 x 10/sup 37/ erg/sec) and fairly close (2.5 kpc), and thus easy to study in detail. The energy spectrum shape in the 10-300 keV band did not differ in three observations six months apart, although the intensity did. The average spectrum shows weak evidence for a broad emission line produced by positron annihilation. There is also evidence for a periodic 5.6 day intensity variation, which was previously unknown for photon energy greater than 10 keV. This means that if the modulation is produced by absorbing matter, it must be ionized. No spectral variation was observed on time scales from minutes to months, but it is present on scales of a few seconds. A power spectrum analysis of the rapid X-ray variability shows that a broad range of time scales is in operation, with the longest a few seconds. This can be interpreted as the effect of large-scale instabilities in the accretion disk which modulate the flow of mass into the central, hot region. The X-ray emission of Circinus X-1 was weaker in 1977-78 than it was in other measurements in 1971-75. The spectrum also became a more steeply falling function of energy. The good correlation between the 10-200 keV and 3-6 keV intensitites rules out intensity modulation caused by intervening matter. Two very intense one-minute flares with very different energy spectra were observed about three minutes apart.

Nolan, P.L.

1982-01-01

93

X-ray luminosities of optically selected cataclysmic variables and application to the Galactic ridge X-ray emission  

NASA Astrophysics Data System (ADS)

By studying Swift X-ray spectra of an optically selected, non-magnetic sample of nearby cataclysmic variables (CVs), we show that there is a population with X-ray luminosity much lower than accounted for in existing studies. We find an average 0.5-10.0 keV luminosity of 8× 10^{29}{ {erg s^{-1}}} which is an order of magnitude lower than observed in previous samples. Looking at the co-added X-ray spectrum of 20 CVs, we show that the spectral properties of this optically selected, low X-ray luminosity sample - likely characteristic of the dominant population of CVs - resemble that of their brighter counterpart, as well as the X-ray emission originating in the Galactic ridge. It is argued that if the space density of CVs is greater than the current estimates, as it is indeed predicted by population synthesis models, then CVs can significantly contribute to the Galactic ridge emission.

Reis, R. C.; Wheatley, P. J.; Gänsicke, B. T.; Osborne, J. P.

2013-04-01

94

Response of the low ionosphere to X-ray and Lyman-? solar flare emissions  

NASA Astrophysics Data System (ADS)

Using soft X-ray measurements from detectors onboard the Geostationary Operational Environmental Satellite (GOES) and simultaneous high-cadence Lyman-? observations from the Large Yield Radiometer (LYRA) onboard the Project for On-Board Autonomy 2 (PROBA2) ESA spacecraft, we study the response of the lower part of the ionosphere, the D region, to seven moderate to medium-size solar flares that occurred in February and March of 2010. The ionospheric disturbances are analyzed by monitoring the resulting sub-ionospheric wave propagation anomalies detected by the South America Very Low Frequency (VLF) Network (SAVNET). We find that the ionospheric disturbances, which are characterized by changes of the VLF wave phase, do not depend on the presence of Lyman-? radiation excesses during the flares. Indeed, Lyman-? excesses associated with flares do not produce measurable phase changes. Our results are in agreement with what is expected in terms of forcing of the lower ionosphere by quiescent Lyman-? emission along the solar activity cycle. Therefore, while phase changes using the VLF technique may be a good indicator of quiescent Lyman-? variations along the solar cycle, they cannot be used to scale explosive Lyman-? emission during flares.

Raulin, Jean-Pierre; Trottet, GéRard; Kretzschmar, Matthieu; Macotela, Edith L.; Pacini, Alessandra; Bertoni, Fernando C. P.; Dammasch, Ingolf E.

2013-01-01

95

Soft X-ray emissions from planets, moons, and comets  

Microsoft Academic Search

A wide variety of solar system bodies are now known to radiate in the soft X-ray energy (10 keV) X-rays mainly result from the electron bremsstrahlung process. In this paper we present a brief review of the X-ray observations on each of the planetary bodies and discuss their characteristics and proposed source mechanisms.

A. Bhardwaj; G. R. Gladstone; R. F. Elsner; J. H. Waite Jr.; D. Grodent; T. E. Cravens; R. R. Howell; A. E. Metzger; N. Ostgaard; A. N. Maurellis; R. E. Johnson; M. C. Weisskopf; T. Majeed; P. G. Ford; A. F. Tennant; J. T. Clarke; W. S. Lewis; K. C. Hurley; F. J. Crary; E. D. Feigelson; G. P. Garmire; D. T. Young; M. K. Dougherty; S. A. Espinosa; J.-M. Jahn

2002-01-01

96

Intra-cluster ionization and X-ray emission  

NASA Astrophysics Data System (ADS)

The interaction of high-intensity short-pulse laser radiation with atoms, bound in a cluster, releases electrons by field ionization. These electrons are accelerated inside the cluster to give rise to a collisional inner-shell ionization. The excited ions can produce prompt and possibly amplified X-ray s. This model, developed on the basis of experimental results by Rhodes and coworkers [9,10] is analysed in detail. The calculations predict that the generation of excited states inside the cluster is in principle possible, but the effectivity is relatively small. However, taking into account the multiple pass of the (oscillating) electron in the cluster and - in extension to [9,10] - the production of excited ion states in a recombining scheme, an attractive prompt and, in addition, short-time amplified X-ray emission is to be expected. In a first approximation the time behaviour will be discussed specifically for the rare-gas (Ar, Kr, Xe) clusters and C60.

Brunner, W.

1996-03-01

97

Search for X-ray emission from the radio lobes of Scorpius X-1  

Microsoft Academic Search

Images obtained with the low-energy imaging telescope on board the European X-Ray Astronomy Satellite have been searched for X-ray emission from the radio lobes of Sco X-1. After the scattered photons from the image of the central X-ray source in Sco X-1 are taken into account, no significant additional X-ray flux from the radio lobes can be detected above the

Barry Geldzahler; Paul Hertz

1987-01-01

98

X-ray emission in relativistic ion-atom collisions  

SciTech Connect

X-ray line-emission produced during collisions of relativistic multi-charged ions with atoms is discussed. A direct calculation for radiative electron capture (REC) rates is presented within the distorted-wave impulse approximation (DWIA). Simple formulae are obtained for the angular distribution of radiation, and closed analytic formula are derived for small {alpha}Z. Reasonable agreement with recent experiments is found for photoemission rates and angular distributions. Our results indicate that the photon spectrum is rather insensitive to target structure, but dependent on multiple-scattering corrections, and this contradicts other theoretical predictions. However, in asymmetric collisions our results are in broad agreement with experiment and Relativistic Impulse Approximation (RIA) calculations. Magnetic transitions are also analysed in terms of the electron and photon polarization correlation parameters.

McCann, J. F.; Glass, J. T.; Crothers, D. S. F. [Physics Department, The University, Durham DH1 3LE (United Kingdom); Institut fuer Theoretische Physik der Justus-Liebig-Universitaet, 39392 Giessen (Germany); Theoretical and Computational Physics Research Division, Queen's University of Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom); Theoretical and Computational Physics Research Division, Queen's University of Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

1996-02-25

99

Valence Band X-Ray Emission Spectra of Compressed Germanium  

SciTech Connect

We report measurements of the valence band width in compressed Ge determined from x-ray emission spectra below the Ge K edge. The width of the valence band does not show any pressure dependence in the semiconducting diamond-type structure of Ge below 10 GPa. On the other hand, in the metallic {beta}-Sn phase above 10 GPa the valence band width increases under compression. Density-functional calculations show an increasing valence band width under compression both in the semiconducting phase (contrary to experiment) and in the metallic {beta}-Sn phase of Ge (in agreement with observed pressure-induced broadening). The pressure-independent valence band width in the semiconducting phase of Ge appears to require theoretical advances beyond the density-functional theory or the GW approximation.

Struzhkin, Viktor V.; Mao Hokwang; Lin Jungfu; Hemley, Russell J. [Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015 (United States); Tse, John S.; Ma Yanming [Steacie Institute for Molecular Science, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6 (Canada); Hu, Michael Y.; Chow, Paul [HPCAT, Carnegie Institution of Washington, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kao Chichang [NSLS, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2006-04-07

100

Influence of laser focal position on X-ray and ion emission of copper plasma  

NASA Astrophysics Data System (ADS)

X-ray emission from copper plasma produced by a sub-nanosecond Nd:glass laser was studied as a function of distance of the target from the focus position. Optimization of soft (0.7-1.56 keV) and hard (3.2-5 keV) X-ray emissions as a function of the laser focal position was studied. In addition, a thallium acid phthalate (TAP) crystal spectrometer with spectral resolution of 30 mÅ was also developed to study variation in X-ray line emission in the spectral range of 1.291-1.610 keV (7.7-9.6 Å) as a function of laser focal position. It is observed that the maximum soft X-ray emission is on either sides of the focus, indicating a dependence on plasma volume, whereas hard X-ray emission shows a single peak close to the ‘best focus’ position. The line X-ray emission intensity with respect to laser focal position also shows a double hump structure as in the case of soft X-ray emission. This indicates that the line emission is also a function of plasma volume. Scaling of X-ray yield with laser intensity has also been determined. Ion emission was also studied as a function of focal position variation. It is observed to match well with the trend shown by X-ray emission.

Chaurasia, S.; Tripathi, S.; Ryc, L.; Dhareshwar, L. J.

2011-05-01

101

The Optical Emission from Ultraluminous X-ray Sources  

NASA Astrophysics Data System (ADS)

Ultraluminous X-ray sources (ULXs) are point-like, non-nuclear sources which exceed the Eddington luminosity for a stellar mass black hole (BH). The emission from these sources might be beamed or super-Eddington, but it has also been proposed that the compact object in these sources are intermediate mass BHs (IMBHs), which fit in the mass range between the two known populations of BH in the galaxy. The existence of IMBHs is under intense debate, and study of the X-ray data has been unable to resolve this issue. This thesis describes a model I have constructed in order to examine the optical/IR emission from these sources; an alternative channel by which their nature may be understood. I assume a binary model with a black hole accreting matter from a Roche lobe filling companion star. I consider the effects of radiative transport and radiative equilibrium in the irradiated surfaces of both the star and a thin accretion disc. I use current stellar evolutionary models as an input component in this model, and hence determine the mass, radius and age of the donor stars in a range of ULX systems, and in some cases provide limits on the BH mass. In addition I determine the mass transfer rate in these systems from the X-ray luminosity and compare this to transfer rate calculations based on the stellar evolutionary models. Since this method is independent of the optical data it is a powerful additional constraint on the parameter space. For systems where optical observations are available at multiple epochs, I make further determinations of the binary parameters based on the optical variability. Where it is possible to constrain the masses of the BHs, I find them to be consistent with BHs of up to ~100 Msun. I find that in general the donor stars are older and less massive than previously thought, and are consistent with being of spectral type B. I discuss how these results affect our understanding of the evolution and history of ULXs. I discuss how future studies of ULX optical counterparts will be even more revealing, and I make predictions for these optical campaigns, estimating binary periods, variability and the results of IR observational campaigns, which my results suggest will be a important tool in future studies of the nature of this class of sources.

Copperwheat, C. M.

2007-11-01

102

On the X-Ray Emission from Massive Star Clusters and Their Evolving Superbubbles  

Microsoft Academic Search

Here we discuss the X-ray emission properties from the hot thermalized plasma that results from the collisions of individual stellar winds and supernovae ejecta within rich and compact star clusters. We propose a simple analytical way of estimating the X-ray emission generated by super star clusters and derive an expression that indicates how this X-ray emission depends on the main

Sergiy Silich; Guillermo Tenorio-Tagle; Gabriel Alejandro Añorve-Zeferino

2005-01-01

103

Hard X-ray and Gamma-Ray Emission from Shell Supernova Remnants  

Microsoft Academic Search

Strong shock waves in shell supernova remnants have been shown to be capable of accelerating particles to energies in excess of 100 TeV. Electrons of these energies produce hard X-ray synchrotron emission and TeV inverse-Compton emission by upscattering cosmic microwave background photons. However, bremsstrahlung from suprathermal, nonrelativistic electrons can also produce hard X-ray emission. I calculate model X-ray and gamma-ray

S. P. Reynolds

1998-01-01

104

On X-ray Emission from Highly Loaded Hydrides  

NASA Astrophysics Data System (ADS)

X-ray emission (1-2 keV) has been observed in various experiments using electrolytic or plasma methods for loading of hydride targets such as Pd-D to atom ratios > 0.8. Intensities vary from very low-level emission up to laser-like focused beams, depending on experimental conditions(A.G. Lipson et al, JETP Letters, (submitted)). Bremsstralung during thermalization of energetic alphas/protons created by nuclear reactions in the loaded hydride (A.G. Lipson et al, Bull APS,derline 47), no. 1,Pt. II, p. 1219 (2002). contributes low level "background" emission. However, the laser-like emission from a Pd cathode bombarded by a high current deuterium glow discharge is attributed to local islands of a super-cell state formed by a cluster of several thousand Pd-D atoms created by combined D loading/flow conditions. D desorption/flow from the plasma heated cathode surface generates non-equilibrium lattice phonons, which pump the "metastable" super-cell state.

Miley, George H.; Hora, Heinrich; Luo, Nie; Lipson, Andrei

2004-03-01

105

Angle-resolved soft X-ray emission and absorption spectroscopy of hexagonal boron nitride.  

PubMed

Angle-resolved soft X-ray emission and absorption spectra in the BK and NK regions of hexagonal BN were measured using polarized synchrotron radiation. The take-off/incident-angle-dependence on the spectral features in both X-ray emission and absorption is clearly observed. The configuration of the sigma and pi orbitals, which were calculated using discrete variational (DV)-Xalpha molecular orbital calculations, explains the angle-resolved soft X-ray emission and absorption spectra. The relative peak intensity of the 394-eV peak in the NK X-ray emission provides useful information about the BN layer ordering. PMID:12788449

Muramatsu, Yasuji; Kaneyoshi, Takahiro; Gullikson, Eric M; Perera, Rupert C C

2003-07-01

106

Effect of insulator sleeve material on the x-ray emission from a plasma focus device  

SciTech Connect

The effect of insulator sleeve material on x-ray emission from a 2.3 kJ Mather type plasma focus device operated in argon-hydrogen mixture is investigated. The time and space resolved x-ray emission characteristics are studied by using a three channel p-i-n diode x-ray spectrometer and a multipinhole camera. The x-ray emission depends on the volumetric ratio of argon-hydrogen mixture as well as the filling pressure and the highest x-ray emission is observed for a volumetric ratio 40% Ar to 60%H{sub 2} at 2.5 mbar filling pressure. The fused silica insulator sleeve produces the highest x-ray emission whereas nonceramic insulator sleeves such as nylon, Perspex, or Teflon does not produce focus or x-rays. The pinhole images of the x-ray emitting zones reveal that the contribution of the Cu K{alpha} line is weak and plasma x-rays are intense. The highest plasma electron temperature is estimated to be 3.3 and 3.6 keV for Pyrex glass and fused silica insulator sleeves, respectively. It is speculated that the higher surface resistivity of fused silica is responsible for enhanced x-ray emission and plasma electron temperature.

Hussain, S.; Badar, M. A. [Department of Physics, University of Sargodha, Sargodha 40100 (Pakistan); Shafiq, M.; Zakaullah, M. [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

2010-09-15

107

New Chandra observations of the jet in 3C273. 1. Softer X-ray than radio spectra and the X-ray emission mechanism  

Microsoft Academic Search

The jet in 3C273 is a high-power quasar jet with radio, optical and X-ray emission whose size and brightness allow a detailed study of the emission processes acting in it. We present deep Chandra observations of this jet and analyze the spectral properties of the jet emission from radio through X-rays. We find that the X-ray spectra are significantly softer

Sebastian Jester; D. E. Harris; H. L. Marshall; K. Meisenheimer

2006-01-01

108

Search for X-ray emission from Nova Cygni 1975  

Microsoft Academic Search

A search for X-rays from Nova Cygni 1975 was carried out before, during, and after the time of optical maximum. No X-rays were detected over the spectral range 0.1-50 keV. On the basis of these results a strong upper limit of .0001 has been placed on the ratio of X-ray to optical luminosity for this nova, consistent with effective temperatures

J. A. Hoffman; W. H. G. Lewin; K. Brecher; J. Buff; G. W. Clark; P. C. Joss; T. Matilsky

1976-01-01

109

Stationary digital breast tomosynthesis with distributed field emission X-ray tube.  

PubMed

Tomosynthesis requires projection images from different viewing angles. Using a distributed x-ray source this can be achieved without mechanical motion of the source with the potential for faster image acquisition speed. A distributed x-ray tube has been designed and manufactured specifically for breast tomosynthesis. The x-ray tube consists of 31 field emission x-ray sources with an angular range of 30°. The total dose is up to 100mAs with an energy range between 27 and 45 kVp. We discuss the source geometry and results from the characterization of the first prototype. The x-ray tube uses field emission cathodes based on carbon nanotubes (CNT) as electron source. Prior to the manufacturing of the sealed x-ray tube extensive testing on the field emission cathodes has been performed to verify the requirements for commercial tomosynthesis systems in terms of emission current, focal spot size and tube lifetime. PMID:21617760

Sprenger, F; Calderon, X; Gidcumb, E; Lu, J; Qian, X; Spronk, D; Tucker, A; Yang, G; Zhou, O

2011-03-01

110

Stationary digital breast tomosynthesis with distributed field emission X-ray tube  

PubMed Central

Tomosynthesis requires projection images from different viewing angles. Using a distributed x-ray source this can be achieved without mechanical motion of the source with the potential for faster image acquisition speed. A distributed x-ray tube has been designed and manufactured specifically for breast tomosynthesis. The x-ray tube consists of 31 field emission x-ray sources with an angular range of 30°. The total dose is up to 100mAs with an energy range between 27 and 45 kVp. We discuss the source geometry and results from the characterization of the first prototype. The x-ray tube uses field emission cathodes based on carbon nanotubes (CNT) as electron source. Prior to the manufacturing of the sealed x-ray tube extensive testing on the field emission cathodes has been performed to verify the requirements for commercial tomosynthesis systems in terms of emission current, focal spot size and tube lifetime.

Sprenger, F.; Calderon, X.; Gidcumb, E.; Lu, J.; Qian, X.; Spronk, D.; Tucker, A.; Yang, G.; Zhou, O.

2011-01-01

111

Update on modeling and data analysis of heliospheric solar wind charge exchange X-ray emission  

NASA Astrophysics Data System (ADS)

About 15 years ago, charge exchange (CX) X-ray emission was discovered in comet observations, and was identified as the radiative decay of excited states of highly-charge solar wind ions populated in collisions with neutral cometary material. This non-thermal X-ray emission mechanism is now generally acknowledged in planetary environments (e.g. Mars, Earth), as well as interstellar atoms sweeping through the heliosphere. In this paper I present the most recent improvements made in simulations of the heliospheric CX X-ray emission. The model results are compared to X-ray data from Suzaku, XMM-Newton and Chandra spanning over a 10-year period, and some conclusions are drawn on the heliospheric contribution to the diffuse soft X-ray background. The solar system CX X-ray sources can serve as prototypes in terms of modeling and diagnostics to more distant astrophysical objects where CX emission signatures are being discovered.

Koutroumpa, D.

2012-04-01

112

X-ray Emission from Megamaser Galaxy IC 2560  

SciTech Connect

Observation of the H{sub 2}O megamaser galaxy IC 2560 with the Chandra Observatory reveals a complex spectrum composed of soft X-ray emission due to multi-temperature thermal plasma, and a hard continuum with strong emission lines. The continuum is most likely a Compton reflection (reprocessing) of primary emission that is completely absorbed at least up to 7 keV. The lines can be identified with fluorescence from Si, S and Fe in the lowest ionization stages. The equivalent widths of the Si and S lines are broadly compatible with those anticipated for reprocessing by optically thick cold plasma of Solar abundances, while the large equivalent width of the Fe line requires some overabundance of iron. A contribution to the line from a transmitted component cannot be ruled out, but the limits on the strength of the Compton shoulder make it less likely. From the bolometric luminosity of the nuclear region, we infer that the source radiates at 1-10% of its Eddington luminosity, for an adopted central mass of 3 x 10{sup 6} M{sub {circle_dot}}. The overall spectrum is consistent with the hypotheses that the central engines powering the detected megamsers in accretion disks are obscured from direct view by the associated accretion disk material itself, and that there is a correlation between the occurrence of megamaser emission and Compton-thick absorption columns. For the 11 known galaxies with both column density measurements and maser emission believed to arise from accretion disks, eight AGN are Compton thick.

Madejski, Greg; /SLAC /KIPAC, Menlo Park; Done, Chris; /Durham U.; Zycki, Piotr; /Warsaw, Copernicus Astron. Ctr.; Greenhill, Lincoln; /KIPAC, Menlo Park /Harvard-Smithsonian Ctr. Astrophys.

2005-09-12

113

X-Ray Emission from Magnetic Cataclysmic Variables and White Dwarf Mass Estimates  

Microsoft Academic Search

We have calculated the temperature and density structures of the postshock regions in accreting magnetic white dwarfs and deduced the related X-ray emission. Our calculations show that the X-rays from structured postshock regions with strong magnetic fields are significantly softer than the X-rays from model emission regions, which are assumed to be homogeneous. Inclusion of these effects, and an improved

Kinwah Wu; G. Chanmugam; G. Shaviv

1995-01-01

114

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

115

Beamed and Unbeamed X-Ray Emission in FR1 Radio Galaxies.  

National Technical Information Service (NTIS)

The research exploited ROSAT's sensitivity, together with its spatial and spectral resolution, to separate X-ray emission components in the sources. Prior to ROSAT, the dominant X-ray emission mechanism in radio galaxies as a class was unclear, with corre...

D. M. Worrall

2000-01-01

116

Beamed and Unbeamed X-ray Emission in FR1 Radio Galaxies.  

National Technical Information Service (NTIS)

There is good evidence for X-ray emission associated with AGN jets which are relativeistically boosted towards the observer. But to what jet radius does such X-ray emission persist. To attempt to answer this question one can look at radio galaxies: their ...

D. M. Worrall

1997-01-01

117

Eclipse and collapse of the colliding wind X-ray emission from Eta Carinae  

NASA Astrophysics Data System (ADS)

X-ray emission from the massive stellar binary system, ? Carinae, drops strongly around periastron passage; the event is called the X-ray minimum. We launched a focused observing campaign in early 2009 to understand the mechanism of causing the X-ray minimum. During the campaign, hard X-ray emission (<10 keV) from ? Carinae declined as in the previous minimum, though it recovered a month earlier. Extremely hard X-ray emission between 15-25 keV, closely monitored for the first time with the Suzaku HXD/PIN, decreased similarly to the hard X-rays, but it reached minimum only after hard X-ray emission from the star had already began to recover. This indicates that the X-ray minimum is produced by two composite mechanisms: the thick primary wind first obscured the hard, 2-10 keV thermal X-ray emission from the wind-wind collision (WWC) plasma; the WWC activity then decays as the two stars reach periastron.

Hamaguchi, Kenji; Corcoran, Michael F.

2012-03-01

118

X-Ray Emission From SN Ia 1885A & 1986G  

NASA Astrophysics Data System (ADS)

X-ray emission is expected from the explosion and subsequent evolution of a Type Ia supernova. The outgoing shock will run into circumstellar material from early phases of the progenitor's evolution and generate X-ray emission from the interaction. To date, Type Ia supernovae have not been convincingly detected as X-ray sources. A number of remnants in the Milky Way are X-ray sources (eg, SN1006, Tycho). The question of when Type Ia supernovae become X-ray-emitting remnants remains open. We analyze and discuss the available Chandra X-ray Observatory data on two old Type Ia supernovae, SN1885A in M31 and SN1986G in NGC 5128 (= Cen A).

Packard, Melody; Schlegel, E. M.; Patnaude, D.; Katsuda, S.; Petre, R.

2012-03-01

119

Cascade L-shell soft-x-ray emission as incident x-ray photons are tuned across the 1s ionization threshold  

SciTech Connect

The cascade L-shell x-ray emission as an incident polarized and unpolarized monochromatic radiation overpass the 1s ionization threshold is investigated for the metallic Fe by means of moderate resolution, quantitative x-ray spectrometry. A full ab initio theoretical investigation of the L-shell x-ray emission processes is performed based on a detailed straightforward construction of the cascade decay trees within the Pauli-Fock approximation. The agreement obtained between experiments and the presented theory is indicated and discussed with respect to the accuracy of advanced atomic models as well as its significance for the characterization capabilities of x-ray fluorescence (XRF) analysis.

Sokaras, D.; Andrianis, M.; Lagoyannis, A. [Institute of Nuclear Physics, N.C.S.R. 'Demokritos', Aghia Paraskevi, GR-15310, Athens (Greece); Kochur, A. G. [Rostov State University of Transport Communication, 344038, Rostov-na-Donu (Russian Federation); Mueller, M.; Kolbe, M.; Beckhoff, B. [Physikalisch-Technische Bundesanstalt, Abbestrasse 2-12, D-10587, Berlin (Germany); Mantler, M. [Technische Universitaet Wien, A-1040, Vienna (Austria); Zarkadas, Ch. [Institute of Nuclear Physics, N.C.S.R. 'Demokritos', Aghia Paraskevi, GR-15310, Athens (Greece); PANalytical B.V., 7600 AA Almelo (Netherlands); Karydas, A. G. [Institute of Nuclear Physics, N.C.S.R. 'Demokritos', Aghia Paraskevi, GR-15310, Athens (Greece); Nuclear Spectrometry and Applications Laboratory, International Atomic Energy Agency (IAEA), A-2444, Seibersdorf (Austria)

2011-05-15

120

X-ray observations with the Einstein Observatory of emission-line galaxies  

Microsoft Academic Search

X-ray observations of narrow-emission-line galaxies are presented and discussed. One source, NGC 1365, is found to be extended in the soft X-ray band; three others, NGC 2992, NGC 5506, and NGC 7582, have been observed to vary in intensity. The best fit spectral index and cutoff energy Ea are derived for NGC 2992, NGC 5506, and NGC 7582. The X-ray

T. Maccacaro; G. C. Perola; M. Elvis

1982-01-01

121

Dynamic radiography using a carbon-nanotube-based field-emission x-ray source  

SciTech Connect

We report a dynamic radiography system with a carbon nanotube based field-emission microfocus x-ray source. The system can readily generate x-ray radiation with continuous variation of temporal resolution as short as nanoseconds. Its potential applications for dynamic x-ray imaging are demonstrated. The performance characteristics of this compact and versatile system are promising for noninvasive imaging in biomedical research and industrial inspection.

Cheng, Y.; Zhang, J.; Lee, Y.Z.; Gao, B.; Dike, S.; Lin, W.; Lu, J.P.; Zhou, O. [Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Department of Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Xintek, Inc., 308 W Rosemary St., Chapel Hill, North Carolina 27516 (United States); Curriculum in Applied and Materials Sciences, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Department of Radiology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 and Curriculum in Applied and Materials Sciences, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)

2004-10-01

122

Electron optics simulation for designing carbon nanotube based field emission x-ray source  

Microsoft Academic Search

In this dissertation, electron optics simulation for designing carbon nanotube (CNT) based field emission x-ray source for medical imaging applications will be presented. However, for design optimization of x-ray tubes accurate electron beam optics simulation is essential. To facilitate design of CNT x-ray sources a commercial 3D finite element software has been chosen for extensive simulation. The results show that

Shabana Sultana

2010-01-01

123

Polarization of X-ray emission from the Sgr B2 cloud  

NASA Astrophysics Data System (ADS)

The Sgr B2 giant molecular cloud is claimed to be an `X-ray reflection nebula'- the reprocessing site of a powerful flare of the Sgr A* source, which occurred a few hundred years ago. The shape of the X-ray spectrum and the strength of the iron fluorescent line support this hypothesis. We argue that the cleanest test of the origin of X-rays from Sgr B2 would be a detection of polarized emission from this source.

Churazov, E.; Sunyaev, R.; Sazonov, S.

2002-03-01

124

Femtosecond X-ray line emission from multilayer targets irradiated by short laser pulses  

Microsoft Academic Search

The invention of high-power, ultra-short-pulse lasers has opened the way to investigations aimed at the creation of a new type of bright X-ray source for various uses including material science applications and time-resolved X-ray diffraction for biology. The efficiency with which laser energy incident on a solid target is converted into an X-ray emission depends on many factors, including the

H. Nakano; A. A. Andreev; J. Limpouch

2004-01-01

125

Femtosecond x-ray line emission from specially designed targets irradiated by short laser pulses  

Microsoft Academic Search

The invention of high-power ultra short pulse lasers has opened way to investigations aimed at creation of a new type of bright x-ray source for different applications including material science and time resolved x-ray diffraction for biology. The conversion efficiency of the laser energy incident onto a solid target into the x-ray emission depends on many factors, including the temporal

Alexander A. Andreev; Hidetoshi Nakano; Jiri Limpouch

2004-01-01

126

Mapping the x-ray emission region in a laser-plasma accelerator.  

PubMed

The x-ray emission in laser-plasma accelerators can be a powerful tool to understand the physics of relativistic laser-plasma interaction. It is shown here that the mapping of betatron x-ray radiation can be obtained from the x-ray beam profile when an aperture mask is positioned just beyond the end of the emission region. The influence of the plasma density on the position and the longitudinal profile of the x-ray emission is investigated and compared to particle-in-cell simulations. The measurement of the x-ray emission position and length provides insight on the dynamics of the interaction, including the electron self-injection region, possible multiple injection, and the role of the electron beam driven wakefield. PMID:22181891

Corde, S; Thaury, C; Phuoc, K Ta; Lifschitz, A; Lambert, G; Faure, J; Lundh, O; Benveniste, E; Ben-Ismail, A; Arantchuk, L; Marciniak, A; Stordeur, A; Brijesh, P; Rousse, A; Specka, A; Malka, V

2011-11-18

127

Eclipse and Collapse of the Colliding Wind X-ray Emission from Eta Carinae  

NASA Astrophysics Data System (ADS)

X-ray emission from the massive stellar binary system, ? Carinae, drops strongly around periastron passage. We launched a focused observing campaign in early 2009 to understand the mechanism, which causes the X-ray minimum. During the campaign, hard X-ray emission (< 10 keV) from ? Carinae declined as in the previous minimum, though it recovered a month earlier. Extremely hard X-ray emission between 15-25 keV, closely monitored for the first time with the Suzaku HXD/PIN, decreased similarly to the hard X-rays, but it reached minimum only after hard X-ray emission from the star had already began to recover. This indicates that the X-ray minimum is produced by two composite mechanisms: the thick primary wind first obscured the hard, 2-10 keV thermal X-ray emission from the wind-wind collision (WWC) plasma; the WWC activity then decays as the two stars reach periastron.

Hamaguchi, K.; Corcoran, M. F.; Eta Carinae Team

2012-12-01

128

Evidence of Non-thermal X-Ray Emission from HH 80  

NASA Astrophysics Data System (ADS)

Protostellar jets appear at all stages of star formation when the accretion process is still at work. Jets travel at velocities of hundreds of km s-1, creating strong shocks when interacting with the interstellar medium. Several cases of jets have been detected in X-rays, typically showing soft emission. For the first time, we report evidence of hard X-ray emission possibly related to non-thermal processes not explained by previous models of the post-shock emission predicted in the jet/ambient interaction scenario. HH 80 is located at the south head of the jet associated with the massive protostar IRAS 18162-2048. It shows soft and hard X-ray emission in regions that are spatially separated, with the soft X-ray emission region situated behind the region of hard X-ray emission. We propose a scenario for HH 80 where soft X-ray emission is associated with thermal processes from the interaction of the jet with denser ambient matter and hard X-ray emission is produced by synchrotron radiation at the front shock.

López-Santiago, J.; Peri, C. S.; Bonito, R.; Miceli, M.; Albacete-Colombo, J. F.; Benaglia, P.; de Castro, E.

2013-10-01

129

Chandra X-Ray Grating Spectrometry of eta Carinae near X-Ray Minimum. I. Variability of the Sulfur and Silicon Emission Lines  

Microsoft Academic Search

We report on variations in important X-ray emission lines in a series of Chandra grating spectra of the supermassive colliding wind binary star eta Car, including key phases around the X-ray minimum\\/periastron passage in 2003.5. The X-rays arise from the collision of the slow, dense wind of eta Car with the fast, low-density wind of an otherwise hidden companion star.

D. B. Henley; M. F. Corcoran; J. M. Pittard; I. R. Stevens; K. Hamaguchi; T. R. Gull

2008-01-01

130

The 300 Kpc Long X-Ray Jet in PKS 1127-145, Z=1.18 Quasar: Constraining X-Ray Emission Models  

SciTech Connect

We present a {approx} 100 ksec Chandra X-ray observation and new VLA radio data of the large scale, 300 kpc long X-ray jet in PKS 1127-145, a radio loud quasar at redshift z=1.18. With this deep X-ray observation we now clearly discern the complex X-ray jet morphology and see substructure within the knots. The X-ray and radio jet intensity profiles are seen to be strikingly different with the radio emission peaking strongly at the two outer knots while the X-ray emission is strongest in the inner jet region. The jet X-ray surface brightness gradually decreases by an order of magnitude going out from the core. The new X-ray data contain sufficient counts to do spectral analysis of the key jet features. The X-ray energy index of the inner jet is relatively flat with {alpha}{sub x} = 0.66 {+-} 0.15 and steep in the outer jet with {alpha}{sub x} = 1.0 {+-} 0.2. We discuss the constraints implied by the new data on the X-ray emission models and conclude that ''one-zone'' models fail and at least a two component model is needed to explain the jet's broad-band emission. We propose that the X-ray emission originates in the jet proper while the bulk of the radio emission comes from a surrounding jet sheath. We also consider intermittent jet activity as a possible cause of the observed jet morphology.

Siemiginowska, Aneta; /Harvard-Smithsonian Ctr. Astrophys.; Stawarz, Lukasz; /Heidelberg Observ. /Jagiellonian U., Astron. Observ. /KIPAC, Menlo Park; Cheung, C.C.; /KIPAC, Menlo Park; Harris, D.E.; /Harvard-Smithsonian Ctr. Astrophys.; Sikora, Marek; /Warsaw, Copernicus Astron. Ctr.; Aldcroft, Thomas L.; /Harvard-Smithsonian Ctr. Astrophys.; Bechtold, Jill; /Arizona U., Astron. Dept. - Steward Observ.

2006-11-20

131

Search for X-ray emission from the radio lobes of Scorpius X-1  

SciTech Connect

Images obtained with the low-energy imaging telescope on board the European X-Ray Astronomy Satellite have been searched for X-ray emission from the radio lobes of Sco X-1. After the scattered photons from the image of the central X-ray source in Sco X-1 are taken into account, no significant additional X-ray flux from the radio lobes can be detected above the background. The 3 sigma upper limit is less than 0.7 micro-Jy for the northeast radio lobe and less than 1.0 micro-J for the southwest radio lobe. This eliminates the embedded source model of Kundt and Gopal-Krishna as a viable model of the radio emission. These limits are three orders of magnitude too high to constrain models of synchrotron or inverse Compton X-ray emission. 22 references.

Geldzahler, B.; Hertz, P.

1987-11-01

132

Variable Geocoronal X-ray Emission from Solar Wind Charge Exchange  

NASA Astrophysics Data System (ADS)

Solar wind charge exchange (SWCX) X-rays are emitted when highly charged solar wind ions such as O7+ collide with neutral gas. The best known examples of this occur around comets, but SWCX emission also arises in the Earth's tenuous outer atmosphere (exosphere, or geocorona) and throughout the heliosphere as neutral H and He from the interstellar medium flows into the solar system. This geocoronal and heliospheric emission comprises much of the soft X-ray background and is seen in every X-ray observation. Geocoronal emission, although usually weaker than heliospheric emission, arises within a few Earth radii and therefore responds much more quickly (on time scales of less than an hour) to changes in solar wind intensity than the widely distributed heliospheric emission. We are studying roughly a dozen time periods since the launch of the Chandra X-ray Observatory in 1999 when the flux of O7+ in the solar wind (measured by the Advanced Composition Explorer (ACE) satellite) was at its highest. These gusts of wind usually last only a short time and quickly fade, leading to corresponding abrupt changes in geocoronal SWCX X-ray emission. These changes may or may not be seen by X-ray observatories depending on their line of sight through the magnetosphere. We present here preliminary results of our study of the temporal correlation between solar wind flux and the X-ray background emission measured by Chandra.

Martin, Poppy; Wargelin, B. J.

2012-01-01

133

Models of X-ray and gamma-ray emission from Seyfert galaxies  

Microsoft Academic Search

X-ray and gamma-ray observations of Seyfert 1 galaxies are briefly reviewed. Both thermal and non-thermal models for X-ray and gamma-ray emission are discussed. Particular attention is given to various disc-corona models including both homogeneous and inhomogeneous (patchy) corona models. Recent work on exact radiative transfer in such geometries are reviewed.

Roland Svensson

1996-01-01

134

Continuum x-ray emission from the Alcator A tokamak  

NASA Astrophysics Data System (ADS)

X rays from 1 to 25 keV emitted by the Alcator A device have been collected with a Si(Li) detector and pulse-height-analysis system. Under normal operating conditions, spectra are thermal, indicating clean (Zeff~1), Maxwellian distributions. Temperature profiles are provided. When vdvth>~0.03, the x-ray spectra become nonthermal, reflective of non-Maxwellian distributions. The observed nonthermal behavior increases with minor radius and poloidal symmetry, is correlated with poor energy confinement, and cannot be accounted for by classical electric-field-driven perturbation theory. Radial electron diffusion is discussed.

Rice, John E.; Molvig, Kim; Helava, Heikki I.

1982-03-01

135

A New Correlation between GRB X-Ray Flares and the Prompt Emission  

NASA Astrophysics Data System (ADS)

From a sample of gamma-ray bursts (GRBs) detected by the Fermi and Swift missions, we have extracted the minimum variability timescales for temporal structures in the light curves associated with the prompt emission and X-ray flares. A comparison of this variability timescale with pulse parameters such as rise times, determined via pulse-fitting procedures, and spectral lags, extracted via the cross-correlation function, indicates a tight correlation between these temporal features for both the X-ray flares and the prompt emission. These correlations suggest a common origin for the production of X-ray flares and the prompt emission in GRBs.

Sonbas, E.; MacLachlan, G. A.; Shenoy, A.; Dhuga, K. S.; Parke, W. C.

2013-04-01

136

The extended X-ray emission around RRAT J1819-1458  

NASA Astrophysics Data System (ADS)

We present new imaging and spectral analysis of the recently discovered extended X-ray emission around the high-magnetic-field rotating radio transient RRAT J1819-1458. We used two Chandra observations, taken on 2008 May 31 and 2011 May 28. The diffuse X-ray emission was detected with a significance of ~19? in the image obtained by combining the two observations. Long-term spectral variability has not been observed. Possible scenarios for the origin of this diffuse X-ray emission, further detailed in Camero-Arranz et al. (2012), are here discussed.

Camero-Arranz, A.; Rea, N.; McLaughlin, M. A.; Bucciantini, N.; Slane, P.; Gaensler, B.; Torres, D.; Stella, L.; de Oña, E.; Israel, G.; Camilo, F.; Possenti, A.

2013-03-01

137

Electronic structure of LaSrMnO4: X-ray photoelectron spectroscopy and x-ray emission spectroscopy studies  

NASA Astrophysics Data System (ADS)

We present a comprehensive investigation of the valence band of the single-layered manganite LaSrMnO4. X-ray photoelectron spectroscopy and x-ray emission spectroscopy were used to reveal a detailed picture of the total and partial densities of states in this compound. The results are discussed in the light of available theory.

Kuepper, K.; Klingeler, R.; Reutler, P.; Büchner, B.; Neumann, M.

2006-04-01

138

Hard X-ray Emission and Efficient Particle Acceleration by Supernova Remnants  

NASA Astrophysics Data System (ADS)

I discuss the non-thermal X-ray emission from young supernova remnants. Over the last decade it has become clear from both X-ray and ?-ray observations that young supernovae accelerate particles up to 100 TeV. In soft X-rays the accelerated >10 TeV electrons produce synchrotron radiation, coming from narrow filaments located at the shock fronts. The width of these filaments shows that the magnetic fields are relatively high, thus providing evidence for magnetic field amplification. The synchrotron radiation of several remnants is known to extend into the hard X-ray regime. In particular Cas A, has a spectrum that appears as a power law up to almost 100 TeV. This is very surprising, as a steepening is expected going from the soft to the hard X-ray band. The spectrum is likely a result of many superimposed individual spectra, each steepening at different energies. This implies considerable spatial variation in hard X-rays, an obvious target for Simbol-X. The variations will be important to infer local shock acceleration properties, but also magnetic field fluctuations may cause spatial and temporal variations. Finally, I draw the attention to super bubbles and supernovae as sources of cosmic rays. As such they may be sources of hard X-ray emission. In particular, supernovae exploding inside the dense red supergiants winds of their progenitors ares promising candidates for hard X-ray emission.

Vink, Jacco

2009-05-01

139

Study of Hard X-ray Emission in HSX  

NASA Astrophysics Data System (ADS)

A hard x-ray system employing a CdZnTe detector has been implemented on HSX. The magnetic configuration has been altered between QHS and Mirror mode in order to determine the effect of magnetic ripple on the spectrum and densities of fast electrons. Pulse height analysis of the hard x-ray signals (HX) show the presence of x-ray photons with energy up to 1 MeV. In the QHS mode, the hard x-ray intensity decreases monotonically over two orders of magnitude as the central line averaged density increases from 0.2 to 1.0 x 10^12 cm-3. In contrast, in the mirror configuration the intensity level is small at the lowest density, peaks at a density of 0.5 x 10^12 cm-3 and then falls at higher density. In QHS the tail of the spectrum extends to higher energies than for the mirror mode. Increased intensities correlate with the highest stored energies as measured by the diamagnetic loop.

Abdou, A. E.; Almagri, A. F.; Anderson, D. T.; Radder, J.; Talmadge, J. N.

2003-10-01

140

Supernova remnants and their X-ray emission  

SciTech Connect

This book contains the proceedings from the International Astronomical Union Symposium No. 101 on supernova remnants. The proceedings contain a complete report on the effects of X-ray information on the ideas about supernova remnants. Also included are reviews of radio, optical, and theoretical results. The volume contains transcriptions of some of the discussions that followed the papers given at the symposium.

Danziger, J.; Gorenstein, P. (eds.)

1983-01-01

141

Influence of the voltage-time derivative in X-ray emission from laboratory sparks  

NASA Astrophysics Data System (ADS)

X-rays produced by laboratory sparks in air at atmospheric pressure for rod-rod and rod-plane configurations were observed. A total of 510 sparks were applied for both polarities. The paper shows the effects of the voltage rise time and the peak voltage in the generation of X-rays. It is found here that shorter rise times and high peak voltages tend to produce more X-rays emissions with higher energies than longer front waveforms or lower peak voltages. In a similar way, higher voltage variations produce more energetic emissions. This finding suggests that the variation of the electric field before the breakdown can play a fundamental role in the X-ray production. The results are similar with the observations of X-rays produced in natural lightning where detections have been associated to leader steps before the return stroke.

March, Víctor; Montanyà, Joan

2010-10-01

142

Measurements of Peak X-ray Emission of imploding DT capsules using X-ray Diagnostics at the National Ignition Facility  

NASA Astrophysics Data System (ADS)

The absolute time (bang time) and burn width of the x-ray emission from the imploding cores of deuterium-tritium capsules near peak compression are measured by several different but complimentary diagnostic instruments. These instruments report independent measurements for the bang time (BT) and burn width (BW). A summary of the results from recent DT experiments is presented contrasting the BT and BW reported by: SPIDER, an x-ray streak camera; Gamma Ray History, a gamma ray detector; and Hardened X-ray Gated Imager (HGXI), a gated micro-channel plate coupled to film camera. An evaluation of the shielding and design of the instruments is presented in order to compare the spectral sensitivity of the instruments. Simulations of the x-ray emission spectrum are examined with the results reported by these x-ray diagnostics.

Khan, Shahab; Macphee, Andrew; Izumi, Nobuhiko; Glenn, Steve; Kimbrough, Joe; Herrmann, Hans; Church, Jennifer; Bell, Perry; Bradley, David

2012-10-01

143

Crustal Emission and the Quiescent Spectrum of the Neutron Star in KS 1731-260  

NASA Astrophysics Data System (ADS)

The type I X-ray-bursting low-mass X-ray binary KS 1731-260 was recently detected for the first time in quiescence by Wijnands et al. following a ?ob~13 yr outburst, which ended in 2001 February. We show that the emission area radius for a H atmosphere spectrum (possibly with a hard power-law component that dominates the emission above 3.5 keV) is consistent with that observed from other quiescent neutron star transients, R?=23+30-15(d/8kpc) km and examine possible IR counterparts for KS 1731-260. Unlike all other known transient neutron stars, the duration of this recent (and the only observed) outburst is as long as the thermal diffusion time of the crust. The large amount of heat deposited by reactions in the crust will have heated the crust to temperatures much higher than the equilibrium core temperature. As a result, the thermal luminosity currently observed from the neutron star is dominated not by the core but by the crust. This scenario implies that the mean outburst recurrence timescale found by Wijnands et al. (~200 yr) is a lower limit. Moreover, because the thermal emission is dominated by the hot crust, the level and the time evolution of quiescent luminosity is determined mostly by the amount of heat deposited in the crust during the most recent outburst (for which reasonable constraints on the mass accretion rate exist) and is only weakly sensitive to the core temperature. Using estimates of the outburst mass accretion rate, our calculations of the quiescent flux immediately following the end of the outburst agree with the observed quiescent flux to within a factor of a few. In this paper, we present simulations of the evolution of the quiescent light curve for different scenarios of the crust microphysics and demonstrate that monitoring observations (with currently flying instruments) spanning from 1 to 30 yr can measure the crust cooling timescale and the total amount of heat stored in the crust. These quantities have not been directly measured for any neutron star. This makes KS 1731-260 a unique laboratory for studying the thermal properties of the crust by monitoring the luminosity over the next few years to decades.

Rutledge, Robert E.; Bildsten, Lars; Brown, Edward F.; Pavlov, George G.; Zavlin, Vyacheslav E.; Ushomirsky, Greg

2002-11-01

144

Spectra of the Heliospheric X-ray and EUV Emission Induced by Charge Transfer Collisions  

NASA Astrophysics Data System (ADS)

Spectra of the heliospheric X-ray and extreme ultraviolet (EUV) emission induced by highly charged solar wind ions are investigated. Intensities of various ion emission lines are calculated taking into account selective populations of the excited states of heavy solar wind ions in charge transfer collisions with hydrogen and helium atoms of the neutral interstellar gas. Photon cascading spectra of excited solar wind ions are computed for different compositions of the solar wind. The brightest spectral lines of the X-ray and EUV heliospheric emission are predicted for the fast and slow components of the solar wind. Polarization of these lines is analyzed. The contribution of the solar wind ion emission to the observed soft X-ray background is discussed. The time variability and the anisotropy of the heliospheric X-ray and EUV radiation are investigated.

Kharchenko, V.; Rigazio, M.; Dalgarno, A.

2001-12-01

145

Soft X-ray, microwave, and hard X-ray emission from a solar flare - Implications for electron heating and acceleration in current channels  

NASA Astrophysics Data System (ADS)

The soft X-ray, microwave, and hard X-ray emissions from the solar flare of May 14, 1980 are studied. The flare consists of a gradual component in soft X-rays and microwaves and a superposed impulsive burst accompanied by hard X-ray emission. The impulsive phase of the flare appears in the soft X-ray emission as a temperature spike and as an increased rate of energy dissipation into the plasma. A new, spatially and spectrally distinct, microwave component appears during the impulsive burst. The data are interpreted in terms of Joule heating and the electric field acceleration of electrons in one or more current sheets. It is found that all three emissions can be generated with sub-Dreicer electric fields. The soft X-ray emitting plasma can be heated by a single current sheet only if the resistivity in the sheet is well above the classical, collisional resistivity. Conditions are also given for the hard X-ray emission to be from nonthermal electrons with classical resistivity.

Holman, Gordon D.; Kundu, Mukul R.; Kane, Sharad R.

1989-10-01

146

A search for periodicities in the X-ray emission from cataclysmic variables  

SciTech Connect

Results are reported from a search for periodicities in the X-ray emission from cataclysmic variables observed with the Einstein Observatory's IPC at 0.16-3.5 keV and 0.01-2.5 Hz. Power spectra are shown for 51 observations of 31 systems, and upper limits are derived to the pulse fractions of signals that are not detected. The majority of systems show no coherent periodicities in their X-ray emission, which is consistent with a model in which the X-rays are produced in a disk/white-dwarf boundary layer. 27 refs.

Eracleous, M.; Patterson, J.; Halpern, J. (Columbia Univ., NY (USA))

1991-03-01

147

Attacking the X-ray emission properties of young stars with the sword of Orion  

NASA Astrophysics Data System (ADS)

We present a survey of X-ray emission from young stars in the Sword of Orion star-formation region using XMM-Newton's EPIC detectors. We find over 850 X-ray sources, of which more than 700 have near-infrared counterparts consistent with being young stars. The survey enables statistical investigation of the dependence of X-ray emission properties of young stars on fundamental stellar parameters (mass, rotation, age) and environmental features (circumstellar disk, active accretion, circumstellar absorption), and study of structure size in individual coronae through analysis of large flares.

Briggs, K. R.; Güdel, M.

2005-03-01

148

Laboratory simulation of charge exchange-produced X-ray emission from comets.  

PubMed

In laboratory experiments using the engineering spare microcalorimeter detector from the ASTRO-E satellite mission, we recorded the x-ray emission of highly charged ions of carbon, nitrogen, and oxygen, which simulates charge exchange reactions between heavy ions in the solar wind and neutral gases in cometary comae. The spectra are complex and do not readily match predictions. We developed a charge exchange emission model that successfully reproduces the soft x-ray spectrum of comet Linear C/1999 S4, observed with the Chandra X-ray Observatory. PMID:12791989

Beiersdorfer, P; Boyce, K R; Brown, G V; Chen, H; Kahn, S M; Kelley, R L; May, M; Olson, R E; Porter, F S; Stahle, C K; Tillotson, W A

2003-06-01

149

Theory of autoionization emission for X-ray excited Auger spectra  

NASA Astrophysics Data System (ADS)

Variation with X-ray excitation energies of spectral shapes and intensities of autoionization electron emission coexisting with the M2,3-VV Auger line is discussed theoretically. Autoionization spectra are obtained as a one-step process of X-ray scattering, while M2,3-VV spectra are obtained as a two-step process of a resonant electron emission following the X-ray absorption. The present theoretical result agrees qualitatively with the experimental result of Brener et al. [Phys. Rev. B37, 1387 (1987)].

Ohmura, Yoshihiro; Sato, Toshihiro

1990-01-01

150

X-ray emission from high-Z spherical laser plasmas: Implications for plasma dynamics  

SciTech Connect

Conversion of 351-nm laser light to soft x-rays has been studied using spherical gold targets irradiated at 5 x 10/sup 12/ - 4 x 10/sup 15/ W/cm/sup 2/. Spectra and time histories of sub-keV and M-band emission are presented. Results have been compared to detailed models (LASNEX) to better determine the dynamics of the plasma processes which lead to x-ray emission. 10 refs.

Goldstone, P.D.; Cobble, J.A.; Hauer, A.; Stradling, G.; Mead, W.C.; Goldman, S.R.; Coggeshall, S.; Richardson, M.C.; Jaanimagi, P.A.; Barnouin, O.

1987-01-01

151

X-ray-based attenuation correction for positron emission tomography\\/computed tomography scanners  

Microsoft Academic Search

A synergy of positron emission tomography (PET)\\/computed tomography (CT) scanners is the use of the CT data for x-ray-based attenuation correction of the PET emission data. Current methods of measuring transmission use positron sources, gamma-ray sources, or x-ray sources. Each of the types of transmission scans involves different trade-offs of noise versus bias, with positron transmission scans having the highest

Paul E. Kinahan; Bruce H. Hasegawa; Thomas Beyer

2003-01-01

152

Effects of Anisotropic Thermal Conduction on X-Ray Emission from SNRs  

Microsoft Academic Search

Several physical mechanisms have been studied in order to explain why composite supernova remnants (SNRs) have shell-like morphologies in radio continuum while their X-ray emission is centrally peaked. One of the proposed mechanisms has been the presence of thermal conduction, which can raise the density at the center of SNRs, increasing the X-ray emission from these regions. In this work,

P. F. Velázquez; J. J. Martinell; A. C. Raga

2003-01-01

153

Correlated Radio:X-Ray Emission in the Hard States of Galactic Microquasars  

NASA Astrophysics Data System (ADS)

We present results of our study of correlated radio and X-ray emission in two black hole candidates and Galactic microquasars GRS 1915+105 and Cyg X-1 in their steady long-term hard states, along with Cyg X-3 (using data obtained from the Rossi X-Ray Timing Explorer all-sky monitor [RXTE-ASM], Compton Gamma Ray Observatory Burst and Transient Source Experiment [CGRO-BATSE], and Green Bank Interferometer [GBI]). We detect a pivotal behavior in the X-ray spectrum of GRS 1915+105, correlated to the radio emission. Similar to the results obtained for Cyg X-3, the flux of X-rays softer than the pivoting point correlates with the radio emission, while the corresponding harder X-ray flux anticorrelates with both the radio and the softer X-ray emission, in this state. We examine all the previously reported correlations of X-ray properties with the radio emission in Galactic microquasars and argue that these are consistent with a general picture where a spectral pivoting is a common feature in these sources with the shape of the spectrum determining the flux of radio emission, during the hard states. We also detect a general monotonic increase in the radio emission of these sources with the soft X-ray emission spanning about 5 orders of magnitude. We qualitatively explain these findings with a two-component advective flow model where the location of a boundary layer between the thin disk and the Comptonizing region determines the spectral shape and also the amount of outflow.

Choudhury, M.; Rao, A. R.; Vadawale, S. V.; Jain, A. K.

2003-08-01

154

Discovery of Soft X-Ray Emission from Io, Europa, and the Io Plasma Torus  

Microsoft Academic Search

We report the discovery of soft (0.25-2 keV) X-ray emission from the Galilean satellites Io and Europa, probably Ganymede, and from the Io Plasma Torus (IPT). Bombardment by energetic (greater than 10 keV) H, O, and S ions from the region of the IPT seems to be the likely source of the X-ray emission from the Galilean satellites. According to

Ronald F. Elsner; G. Randall Gladstone; J. Hunter Waite; Frank J. Crary; Robert R. Howell; Robert E. Johnson; Peter G. Ford; Albert E. Metzger; Kevin C. Hurley; Eric D. Feigelson; Gordon P. Garmire; Anil Bhardwaj; Denis C. Grodent; Tariq Majeed; Allyn F. Tennant; Martin C. Weisskopf

2002-01-01

155

Very high energy gamma-ray emission from X-ray transients during major outbursts  

Microsoft Academic Search

Context: Some high mass X-ray binaries (HMXB) have been recently confirmed as gamma-ray sources by ground based Cherenkov telescopes. In this work, we discuss the gamma-ray emission from X-ray transient sources formed by a Be star and a highly magnetized neutron star. This kind of systems can produce variable hadronic gamma-ray emission through the mechanism proposed by Cheng and Ruderman,

M. Orellana; G. E. Romero; L. J. Pellizza; S. Vidrih

2007-01-01

156

Crushing of interstellar gas clouds in supernova remnants. II. X-ray emission  

Microsoft Academic Search

Context: .X-ray observations of evolved supernova remnants (e.g. the Cygnus loop and the Vela SNRs) reveal emission originating from the interaction of shock waves with small interstellar gas clouds. Aims: .We study and discuss the time-dependent X-ray emission predicted by hydrodynamic modeling of the interaction of a SNR shock wave with an interstellar gas cloud. The scope includes: 1) to

S. Orlando; F. Bocchino; G. Peres; F. Reale; T. Plewa; R. Rosner

2006-01-01

157

Nonthermal Hard X-Ray Emission in Galaxy Clusters Observed with the BeppoSAX PDS  

Microsoft Academic Search

We study the X-ray emission in a sample of galaxy clusters using the BeppoSAX PDS instrument in the 20-80 keV energy band. We estimate the nonthermal hard X-ray (HXR) cluster emission by modeling the thermal contribution from the cluster gas and the nonthermal contamination from the unobscured active galactic nuclei (AGNs) in the clusters. We also evaluate the systematic uncertainties

J. Nevalainen; T. Oosterbroek; M. Bonamente; S. Colafrancesco

2004-01-01

158

X-Ray Emission from Protostellar Jet HH 154: The First Evidence of a Diamond Shock?  

NASA Astrophysics Data System (ADS)

X-ray emission from about 10 protostellar jets has been discovered and it appears as a feature common to the most energetic jets. Although X-ray emission seems to originate from shocks internal to jets, the mechanism forming these shocks remains controversial. One of the best-studied X-ray jets is HH 154, which has been observed by Chandra over a time base of about 10 years. We analyze the Chandra observations of HH 154 by investigating the evolution of its X-ray source. We show that the X-ray emission consists of a bright stationary component and a faint elongated component. We interpret the observations by developing a hydrodynamic model describing a protostellar jet originating from a nozzle and compare the X-ray emission synthesized from the model with the X-ray observations. The model takes into account the thermal conduction and radiative losses and shows that the jet/nozzle leads to the formation of a diamond shock at the nozzle exit. The shock is stationary over the period covered by our simulations and generates an X-ray source with luminosity and spectral characteristics in excellent agreement with the observations. We conclude that the X-ray emission from HH 154 is consistent with a diamond shock originating from a nozzle through which the jet is launched into the ambient medium. We suggest that the physical origin of the nozzle could be related to the dense gas in which the HH 154 driving source is embedded and/or to the magnetic field at the jet launching/collimation region.

Bonito, R.; Orlando, S.; Miceli, M.; Peres, G.; Micela, G.; Favata, F.

2011-08-01

159

EUV and Soft X-Ray Emissions From Comets  

Microsoft Academic Search

We analyzed 8 observations of comets with the Extreme Ultraviolet Explorer (EUVE). A soft X-ray camera in the range of 97-165 eV FWHM with a peak effective area of 28 cm2 and three spectrometers at 80-180, 170-360, and 300-720 Å with peak effective areas of 2.1, 0.5, and 0.8 cm2, respectively, were used for those observations. The detection limit of

V. A. Krasnopolsky

2001-01-01

160

HI Emission in Nearby X-ray Detected Active Galaxies  

NASA Astrophysics Data System (ADS)

We have measured HI profiles in 96 nearby, active galaxies using the 100-meter Green Bank Telescope (GBT). Our sources contain active galactic nuclei (AGN) detected in the hard X-ray (14-195 keV) from Swift Gamma-ray Burst satellite’s Burst Alert Telescope (BAT) 22-month survey. This survey is unique because the sources were detected in the hard X-ray, allowing us to include galaxies that are otherwise obscured in other bands. The HI profiles we gathered are combined with the published optical, infrared, and X-ray data. We present the systemic velocities, outflow velocities, and cold gas mass in the sources. The mass of the cold gas is compared to the luminous mass in stars in order to find clues to unlock the nature of the host galaxies. A comparison of HI with the bolometric luminosity of the AGN is made. Our observations examine how the reservoir of cold gas is correlated with luminosity, as well. Through these data, we look for evolutionary differences in host galaxy types in order to understand how super massive black holes are fueled.

George, Erin; Winter, L. M.; Zauderer, B.; Darling, J.; Koss, M.

2013-01-01

161

X-RAY POLARIZATION FROM ACCRETING BLACK HOLES: CORONAL EMISSION  

SciTech Connect

We present new calculations of X-ray polarization from accreting black holes (BHs), using a Monte Carlo ray-tracing code in full general relativity. In our model, an optically thick disk in the BH equatorial plane produces thermal seed photons with polarization oriented parallel to the disk surface. These seed photons are then inverse-Compton scattered through a hot (but thermal) corona, producing a hard X-ray power-law spectrum. We consider three different models for the corona geometry: a wedge 'sandwich' with aspect ratio H/R and vertically integrated optical depth tau{sub 0} constant throughout the disk; an inhomogeneous 'clumpy' corona with a finite number of hot clouds distributed randomly above the disk within a wedge geometry; and a spherical corona of uniform density, centered on the BH and surrounded by a truncated thermal disk with inner radius R{sub edge}. In all cases, we find a characteristic transition from horizontal polarization at low energies to vertical polarization above the thermal peak; the vertical direction is defined as the projection of the BH spin axis on the plane of the sky. We show how the details of the spectropolarization signal can be used to distinguish between these models and infer various properties of the corona and BH. Although the bulk of this paper focuses on stellar-mass BHs, we also consider the effects of coronal scattering on the X-ray polarization signal from supermassive BHs in active galactic nuclei.

Schnittman, Jeremy D.; Krolik, Julian H., E-mail: schnittm@pha.jhu.ed, E-mail: jhk@pha.jhu.ed [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

2010-04-01

162

CHANDRA OBSERVATION OF QUIESCENT LOW-MASS X-RAY BINARIES IN THE GLOBULAR CLUSTER NGC 6304  

SciTech Connect

This paper presents the analysis of candidate low-mass X-ray binaries in quiescence (qLMXBs) observed during a short Chandra/ACIS observation of the globular cluster (GC) NGC 6304. Two out of the three candidate qLMXBs of this cluster, XMMU 171433-292747 and XMMU 171421-292917, lie within the field of view. This permits comparison with the discovery observation of these sources. The one in the GC core-XMMU 171433-292747-is spatially resolved into two separate X-ray sources, one of which is consistent with a pure H-atmosphere qLMXB, and the other is an X-ray power-law spectrum source. These two spectral components separately account for those observed from XMMU 171433-292747 in its discovery observation. We find that the observed flux and spectral parameters of the H-atmosphere spectral components are consistent with the previous observation, as expected from a qLMXB powered by deep crustal heating. XMMU 171421-292917 also has neutron star atmosphere spectral parameters consistent with those in the XMM-Newton observation and the observed flux has decreased by a factor 0.54{sup +0.30}{sub -0.24}.

Guillot, Sebastien; Rutledge, Robert E. [Department of Physics, McGill University, 3600 rue University, Montreal, QC H2X-3R4 (Canada); Brown, Edward F. [Department of Physics and Astronomy, Michigan State University, 3250 Biomedical Physical Science Building, East Lansing, MI 48824-2320 (United States); Pavlov, George G. [Pennsylvania State University, 512 Davey Lab, University Park, PA 16802 (United States); Zavlin, Vyacheslav E. [Space Science Laboratory, Universities Space Research Association, NASA MSFC VP62, Huntsville, AL 35805 (United States)], E-mail: guillots@physics.mcgill.ca, E-mail: rutledge@physics.mcgill.ca

2009-07-10

163

10 micron detection of the hard X-ray transient GRO J0422+32: Free-free emission from an X-ray-driven accretion disk wind?  

Microsoft Academic Search

We report the detection of 10 micrometer emission from the transient low-mass X-ray binary (LMXB) and optical nova GRO J0422+32 near the maximum of its outburst. We discuss this result in terms of (1) a 'standard' model according to which low-energy radiation of LMXB is caused by reprocessing of X-rays in an accretion disk; (2) emission from a cool secondary

J. van Paradijs; C. M. Telesco; C. Kouveliotou; G. J. Fishman

1994-01-01

164

Faint X-Ray Sources Resolved in the ASCA Galactic Plane Survey and Their Contribution to the Galactic Ridge X-Ray Emission  

Microsoft Academic Search

The X-ray emission from the central region of the Galactic plane, |l|<~45° and |b|<~0.4d, was studied in the 0.7-10 keV energy band with a spatial resolution of ~3' with the Advanced Satellite for Cosmology and Astrophysics (ASCA) observatory. We developed a new analysis method for the ASCA data to resolve discrete sources from the extended Galactic ridge X-ray emission (GRXE).

Mutsumi Sugizaki; Kazuhisa Mitsuda; Hidehiro Kaneda; Keiichi Matsuzaki; Shigeo Yamauchi; Katsuji Koyama

2001-01-01

165

Control parameters for ion heating and X-ray emission from laser induced cluster explosion  

NASA Astrophysics Data System (ADS)

The highest energies of the ions obtained from the explosion of an atomic cluster in an intense femtosecond laser field can vary greatly depending on the cluster size, atomic species and the peak intensity, duration and shape of the laser pulse. By careful choice of these parameters the ion energies, electron energies or X-ray emission can be optimised. A relationship is described that allows for rapid determination of the optimum experimental parameters. We present experimental data of keV X-ray emission from Argon clusters, which investigate intensity and pulse duration effects. In addition we present the first results from closed-loop optimal control, pulse-shaping experiments that optimise X-ray emission and show a significant enhancement in the X-ray yield.

Moore, A. S.; Mendham, K. J.; Symes, D. R.; Robinson, J. S.; Springate, E.; Mason, M. B.; Smith, R. A.; Tisch, J. W. G.; Marangos, J. P.

2005-01-01

166

SphinX MEASUREMENTS OF THE 2009 SOLAR MINIMUM X-RAY EMISSION  

SciTech Connect

The SphinX X-ray spectrophotometer on the CORONAS-PHOTON spacecraft measured soft X-ray emission in the 1-15 keV energy range during the deep solar minimum of 2009 with a sensitivity much greater than GOES. Several intervals are identified when the X-ray flux was exceptionally low, and the flux and solar X-ray luminosity are estimated. Spectral fits to the emission at these times give temperatures of 1.7-1.9 MK and emission measures between 4 Multiplication-Sign 10{sup 47} cm{sup -3} and 1.1 Multiplication-Sign 10{sup 48} cm{sup -3}. Comparing SphinX emission with that from the Hinode X-ray Telescope, we deduce that most of the emission is from general coronal structures rather than confined features like bright points. For one of 27 intervals of exceptionally low activity identified in the SphinX data, the Sun's X-ray luminosity in an energy range roughly extrapolated to that of ROSAT (0.1-2.4 keV) was less than most nearby K and M dwarfs.

Sylwester, J.; Kowalinski, M.; Gburek, S.; Siarkowski, M.; Bakala, J.; Gryciuk, M.; Podgorski, P.; Sylwester, B. [Space Research Centre, Polish Academy of Sciences, 51-622, Kopernika 11, Wroclaw (Poland); Kuzin, S. [P. N. Lebedev Physical Institute (FIAN), Russian Academy of Sciences, Leninsky Prospect 53, Moscow 119991 (Russian Federation); Farnik, F. [Astronomical Institute, Ondrejov Observatory (Czech Republic); Reale, F. [Dipartimento di Fisica, Universita di Palermo, Palermo, Italy, and INAF, Osservatorio Astronomico di Palermo, Palermo (Italy); Phillips, K. J. H., E-mail: js@cbk.pan.wroc.pl [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)

2012-06-01

167

Femtosecond x-ray line emission from specially designed targets irradiated by short laser pulses  

NASA Astrophysics Data System (ADS)

The invention of high-power ultra short pulse lasers has opened way to investigations aimed at creation of a new type of bright x-ray source for different applications including material science and time resolved x-ray diffraction for biology. The conversion efficiency of the laser energy incident onto a solid target into the x-ray emission depends on many factors, including the temporal profile of laser pulse. We report here the results of our theoretical and experimental investigations of the line x-ray emission from layer solid targets irradiated by ultra short laser pulses. The parameters of laser pre-pulse and target thickness are optimized in order to get the maximum laser energy conversion into the emission in the selected x-ray line. Multi-layer foils are proposed in order to increase the energy of K-? line emission from laser plasma simultaneously with shortening of x-ray pulse up to hundred femtoseconds. The emission is studied, both experimentally, and by means of analytical model and numerical simulations.

Andreev, Alexander A.; Nakano, Hidetoshi; Limpouch, Jiri

2004-01-01

168

SphinX Measurements of the 2009 Solar Minimum X-Ray Emission  

NASA Astrophysics Data System (ADS)

The SphinX X-ray spectrophotometer on the CORONAS-PHOTON spacecraft measured soft X-ray emission in the 1-15 keV energy range during the deep solar minimum of 2009 with a sensitivity much greater than GOES. Several intervals are identified when the X-ray flux was exceptionally low, and the flux and solar X-ray luminosity are estimated. Spectral fits to the emission at these times give temperatures of 1.7-1.9 MK and emission measures between 4 × 1047 cm-3 and 1.1 × 1048 cm-3. Comparing SphinX emission with that from the Hinode X-ray Telescope, we deduce that most of the emission is from general coronal structures rather than confined features like bright points. For one of 27 intervals of exceptionally low activity identified in the SphinX data, the Sun's X-ray luminosity in an energy range roughly extrapolated to that of ROSAT (0.1-2.4 keV) was less than most nearby K and M dwarfs.

Sylwester, J.; Kowalinski, M.; Gburek, S.; Siarkowski, M.; Kuzin, S.; Farnik, F.; Reale, F.; Phillips, K. J. H.; Baka?a, J.; Gryciuk, M.; Podgorski, P.; Sylwester, B.

2012-06-01

169

On the Autoionization Emission for X-Ray Excited Auger Spectra  

NASA Astrophysics Data System (ADS)

Autoionization electron emission spectra coexisting with the M2,3-VV Auger line by X-ray excitation are discussed theoretically. The present study is motivated by an experiment of Brener et al. (Phys. Rev. B37 (1987) 1387) on metallic Ti, V and Cr by the use of X-rays of TiK?(4.511 keV) and AlK?(1.487 keV), where autoionization electron emission spectra coexisting with the M2,3-VV line are possible only when the X-rays are TiK?. By a model in which autoionization electron emission spectra are generated by the scattering of X-rays, while M2,3-VV spectra are generated by a resonant electron emission following the X-ray absorption, the increase of autoionization emission relative to M2,3-VV spectra with increasing energies of the incident X-rays is obtained for metallic Ti, in agreement qualitatively with the corresponding experimental result of Brener et al.

Ohmura, Yoshihiro; Sato, Toshihiro

1990-02-01

170

X-ray emission in collisions of highly charged I, Pr, Ho, and Bi ions with a W surface  

NASA Astrophysics Data System (ADS)

X-ray emission yields, which are defined as the total number of emitted x-ray photons per incident ion, and dissipated fractions of potential energies through x-ray emission have been measured for slow highly charged ions of I, Pr, Ho, and Bi colliding with a W surface. A larger amount of potential energy was consumed for the x-ray emission with increasing the atomic number and the charge state. The present measurements show that x-ray emission is one of the main decay channels of hollow atoms produced in collisions of very highly charged ions of heavy elements.

Watanabe, H.; Sun, J.; Tona, M.; Nakamura, N.; Sakurai, M.; Yamada, C.; Yoshiyasu, N.; Ohtani, S.

2007-06-01

171

X-ray emission in collisions of highly charged I, Pr, Ho, and Bi ions with a W surface  

SciTech Connect

X-ray emission yields, which are defined as the total number of emitted x-ray photons per incident ion, and dissipated fractions of potential energies through x-ray emission have been measured for slow highly charged ions of I, Pr, Ho, and Bi colliding with a W surface. A larger amount of potential energy was consumed for the x-ray emission with increasing the atomic number and the charge state. The present measurements show that x-ray emission is one of the main decay channels of hollow atoms produced in collisions of very highly charged ions of heavy elements.

Watanabe, H.; Tona, M.; Ohtani, S. [Institute for Laser Science and Department of Applied Physics and Chemistry, University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); CREST, Japan Science and Technology Agency, Chofu, Tokyo 182-8585 (Japan); Sun, J.; Nakamura, N.; Yamada, C.; Yoshiyasu, N. [Institute for Laser Science and Department of Applied Physics and Chemistry, University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan); Sakurai, M. [Department of Physics, Kobe University, Kobe, Hyogo, 657-8501 (Japan)

2007-06-15

172

Contour shape analysis of hollow ion x-ray emission  

SciTech Connect

Hollow ion x-ray transitions originating from the configurations K{sup 0}L{sup N} have been studied via relativistic atomic structure and Stark broadening calculations. The broadening of the total contour is largely influenced by the oscillator strengths distribution over wavelengths rather than by Stark broadening alone. Interference effects between the upper and lower levels are shown to result in a considerable contour narrowing as well as in a shift of the total contour which could be either red or blue.

Rosmej, F. B.; Angelo, P. [Universite Pierre et Marie Curie, LULI-PAPD, UMR 7605, case 128, 4 Place Jussieu, 75252 Paris Cedex 05 (France); Ecole Polytechnique, Laboratoire pour Utilisation des Lasers Intenses, Physique Atomique dans les Plasmas Denses, 91128 Palaiseau Cedex (France); Aouad, Y. [Universite Pierre et Marie Curie, LULI-PAPD, UMR 7605, case 128, 4 Place Jussieu, 75252 Paris Cedex 05 (France)

2008-10-22

173

Models for X-Ray Emission from Isolated Pulsars  

Microsoft Academic Search

A model is proposed for the observed combination of power-law and thermal\\u000aemission of keV X-rays from rotationally powered pulsars. For gamma-ray pulsars\\u000awith accelerators very many stellar radii above the neutron star surface, 100\\u000aMeV curvature gamma-rays from $e^{-}$ or $e^{+}$ flowing starward out of such\\u000aaccelerators are converted to electron-positron pairs on closed field lines all\\u000aaround the

M. Ruderman; J. P. Halpern; T. Zhu

1997-01-01

174

Solar control on Jupiter's equatorial X-ray emissions: 26–29 November 2003 XMM-Newton observation  

Microsoft Academic Search

During Nov. 26–29, 2003 XMM-Newton observed soft (0.2–2 keV) X-ray emission from Jupiter for 69 hours. The low-latitude X-ray disk emission of Jupiter is observed to be almost uniform in intensity with brightness that is consistent with a solar-photon driven process. The simultaneous light curves of Jovian equatorial X rays and solar X rays (measured by the TIMED\\/SEE and GOES

Anil Bhardwaj; G. Branduardi-Raymont; R. F. Elsner; G. R. Gladstone; G. Ramsay; P. Rodriguez; R. Soria; J. H. Waite Jr; T. E. Cravens

2005-01-01

175

BROADBAND SPECTRAL ANALYSIS OF THE GALACTIC RIDGE X-RAY EMISSION  

SciTech Connect

Detailed spectral analysis of the Galactic X-ray background emission, or the Galactic Ridge X-ray Emission (GRXE), is presented. To study the origin of the emission, broadband and high-quality GRXE spectra were produced from 18 pointing observations with Suzaku in the Galactic bulge region, with a total exposure of 1 Ms. The spectra were successfully fitted by a sum of two major spectral components: a spectral model of magnetic accreting white dwarfs with a mass of 0.66{sup +0.09}{sub -0.07} M{sub Sun} and a softer optically thin thermal emission with a plasma temperature of 1.2-1.5 keV that is attributable to coronal X-ray sources. When combined with previous studies that employed high spatial resolution of the Chandra satellite, the present spectroscopic result gives stronger support to the scenario that the GRXE is essentially an assembly of numerous discrete faint X-ray stars. The detected GRXE flux in the hard X-ray band was used to estimate the number density of the unresolved hard X-ray sources. When integrated over a luminosity range of {approx}10{sup 30}-10{sup 34} erg s{sup -1}, the result is consistent with a value that was reported previously by directly resolving faint point sources.

Yuasa, Takayuki; Makishima, Kazuo; Nakazawa, Kazuhiro, E-mail: yuasa@astro.isas.jaxa.jp [Department of Physics, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan)

2012-07-10

176

Development and Trial Measurements of Hard X-ray Photoelectron Emission Microscope  

SciTech Connect

Photoelectron emission microscope (PEEM) study is performed using hard x-ray illumination. We have successfully obtained images with high spatial resolution of 40 nm with hard x-rays. Spectro-microscopy of Co micro-patterns on Si substrates, which can be applied to XAFS measurements on a minute scale by PEEM. Magnetic imaging has been demonstrated at the Pt L-edges on perpendicular magnetic recording pattern of CoCrPt alloy. These results are the first step toward a new spectroscopic microscopy and magnetic imaging in a hard x-ray region.

Taniuchi, T.; Oshima, M. [Department of Applied Chemistry, University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan); Wakita, T.; Takagaki, M.; Kawamura, N.; Suzuki, M.; Nakamura, T.; Kobayashi, K. [JASRI/SPring-8, Koto, Hyogo, 679-5189 (Japan); Kotsugi, M. [Hiroshima Synchrotron Radiation Center (HiSOR), Higashi-hiroshima, Hiroshima 739-8526 (Japan); Akinaga, H. [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562 (Japan); Muraoka, H. [Research Institute of Electrical Communications (RIEC), Tohoku University, Sendai 980 (Japan); Ono, K. [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 (Japan)

2007-01-19

177

Framed, 16-Image, Kirkpatrick-Baez Microscope for Laser-Plasma X-Ray Emission  

SciTech Connect

A framed, 16-image Kirkpatrick-Baez (KB) type x-ray microscope has been designed for use in imaging laser-plasma x-ray emission. The reflecting elements are 16 pairs of concave mirrors arranged to reflect and focus x rays emanating from a laser-produced plasma. The resolution of the elements is 3 mm at best focus and is better than 5 mm within a 500-mm diam region. A framing camera will be used in combination with the KB optic to produce 16 gated images over a typical interval of 1.5 ns. The system is designed for use on the University of Rochester's OMEGA laser facility.

Marshall, F.J.; Oertel, J.A.; Walsh, P.J.

2004-10-19

178

A carbon nanotube field emission multipixel x-ray array source for microradiotherapy application  

PubMed Central

The authors report a carbon nanotube (CNT) field emission multipixel x-ray array source for microradiotherapy for cancer research. The developed multipixel x-ray array source has 50 individually controllable pixels and it has several distinct advantages over other irradiation source including high-temporal resolution (millisecond level), the ability to electronically shape the form, and intensity distribution of the radiation fields. The x-ray array was generated by a CNT cathode array (5×10) chip with electron field emission. A dose rate on the order of >1.2 Gy?min per x-ray pixel beam is achieved at the center of the irradiated volume. The measured dose rate is in good agreement with the Monte Carlo simulation result.

Wang, Sigen; Calderon, Xiomara; Peng, Rui; Schreiber, Eric C.; Zhou, Otto; Chang, Sha

2011-01-01

179

X-ray Emission from YSOs, Protostellar Jets, and Accretion Eruptive Variables  

NASA Astrophysics Data System (ADS)

Imaging in X-rays has become an extremely useful tool to identify YSOs residing in star forming regions. X-ray emission is also being measured in eruptive young stars, the FUOr-EXOr type stars, and in protostellar jets. Recent deep near-IR imaging of the North American and Pelican nebulae in JHKs and narrowband emission lines of H2 and [FeII] have revealed one of the most active, richest star forming regions in the Galaxy. Within a single EPIC FOV lies dozens of resolved outflows, jets, clusters of YSOs, and even eruptive FUOR-EXOr stars currently undergoing outbursts. I propose to obtain XMM-Newton imaging of three regions rich in all three types of objects to render x-ray detections to assist with confirming the YSOs, and to measure the x-ray flux of the eruptive stars and shocked outflows.

Stringfellow, Guy

2010-10-01

180

Soft X-Ray Emission and Charged Particles Beams from a Plasma Focus of Hundreds Joules  

SciTech Connect

In a new stage of characterization of our plasma focus devices of hundred and tens of joules (PF-400J and PF-50J), preliminary series of measurements on soft X-ray and ion beams have been performed in the device PF-400J (176-539 J, 880 nF, T/4 {approx}300 ns). The device was operated in hydrogen to 7 mbar of pressure . The temporal and spatial X-ray characteristics are investigated by means filtered PIN diodes and a multipinhole camera. Graphite collectors, operating in the bias ion collector mode, are used to estimate the characteristic ion energy using the time flight across the probe array. The time of the ion beam emission to be correlated with plasma emission events associated with the soft X-ray pulses detected by the probes. Temporal correlations between soft X-ray signals and ion beams are performed.

Silva, Patricio; Moreno, Jose; Soto, Leopoldo [Comision Chilena de Energia Nuclear, Casilla 188-D, Santiago (Chile); Pavez, Cristian [Comision Chilena de Energia Nuclear, Casilla 188-D, Santiago (Chile); Universidad de Concepcion, Facultad de Ciencias, Departamento de Fisica, Concepcion (Chile); Arancibia, Jaime [Universidad de Chile, Facultad de Ciencias, Departamento de Fisica, Santiago (Chile)

2006-12-04

181

K-x-ray emission in MeV/u O^5+ on Ar collisions  

NASA Astrophysics Data System (ADS)

K-X-ray emission has been investigated for 1.5 and 2 MeV/u O^5+ on Ar collisions. Emission lines resulting from O-K?, Ar-K? and Ar-K? transitions have been observed. This work was done at Western Michigan University using the tandem Van de Graaff. For oxygen, the observed x rays may be attributed to K-shell excitation and in the case of Ar to excitation or ionization. The K-x-ray production cross sections have been determined taking into account the detector solid angle and detection efficiency, and are compared with related measurements from other investigators. Coincidence measurements are planned to investigate in detail the K-x-ray production mechanisms.

Elkafrawy, T.; Tanis, J. A.

2009-05-01

182

THERMAL X-RAY EMISSION FROM THE SHOCKED STELLAR WIND OF PULSAR GAMMA-RAY BINARIES  

SciTech Connect

Gamma-ray-loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal X-ray emission is expected from the shocked stellar wind, but until now it has neither been detected nor studied in the context of gamma-ray binaries. We present a semi-analytic model of the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries, and find that the thermal X-ray emission increases monotonically with the pulsar spin-down luminosity, reaching luminosities of the order of 10{sup 33} erg s{sup -1}. The lack of thermal features in the X-ray spectrum of gamma-ray binaries can then be used to constrain the properties of the pulsar and stellar winds. By fitting the observed X-ray spectra of gamma-ray binaries with a source model composed of an absorbed non-thermal power law and the computed thermal X-ray emission, we are able to derive upper limits on the spin-down luminosity of the putative pulsar. We applied this method to LS 5039, the only gamma-ray binary with a radial, powerful wind, and obtain an upper limit on the pulsar spin-down luminosity of {approx}6 Multiplication-Sign 10{sup 36} erg s{sup -1}. Given the energetic constraints from its high-energy gamma-ray emission, a non-thermal to spin-down luminosity ratio very close to unity may be required.

Zabalza, V.; Paredes, J. M. [Departament d'Astronomia i Meteorologia, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Marti i Franques 1, E08028 Barcelona (Spain); Bosch-Ramon, V., E-mail: vzabalza@am.ub.es [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)

2011-12-10

183

Soft x-ray emission studies of the electronic structure in silicon nanoclusters  

SciTech Connect

Density of states changes in the valence and conduction band of silicon nanoclusters were monitored using soft x-ray emission and absorption spectroscopy as a function of cluster size. a progressive increase in the valence band edge toward lower energy is found fro clusters with decreasing diameters. A similar but smaller shift is observed in the near-edge x-ray absorption data of the silicon nanoclusters.

Van Buuren, T.; Dinh, L.N.; Chase, L.L.; Siekhaus, W.J.; Jumenez, I.; Terminello, L.J.; Grush, M.; Callcott, T.A.; Carlisle, J.A.

1997-02-01

184

A study of X-ray emission from laboratory sparks in air at atmospheric pressure  

Microsoft Academic Search

We present a detailed investigation of X-ray emission from long laboratory sparks in air at atmospheric pressure. We studied 231 sparks of both polarities using a 1-MV Marx generator with gap lengths ranging from 10 to 140 cm. The X rays generated by the discharges were measured using five NaI\\/PMT detectors plus one plastic scintillator\\/PMT detector, all enclosed in 0.32-cm-thick

J. R. Dwyer; Z. Saleh; H. K. Rassoul; D. Concha; M. Rahman; V. Cooray; J. Jerauld; M. A. Uman; V. A. Rakov

2008-01-01

185

X-Ray Emission from Active Galactic Nuclei with Intermediate-Mass Black Holes  

NASA Astrophysics Data System (ADS)

We present a systematic X-ray study of eight active galactic nuclei (AGNs) with intermediate-mass black holes (MBH~8-95×104 Msolar) based on 12 XMM-Newton observations. The sample includes the two prototype AGNs in this class-NGC 4395 and POX 52 and six other AGNs discovered with the Sloan Digitized Sky Survey. These AGNs show some of the strongest X-ray variability, with the normalized excess variances being the largest and the power density break timescales being the shortest observed among radio-quiet AGNs. The excess-variance-luminosity correlation appears to depend on both the BH mass and the Eddington luminosity ratio. The break timescale-black hole mass relations for AGN with IMBHs are consistent with that observed for massive AGNs. We find that the FWHM of the H?/H? line is uncorrelated with the BH mass, but shows strong anticorrelation with the Eddington luminosity ratio. Four AGNs show clear evidence for soft X-ray excess emission (kTin~150-200 eV). X-ray spectra of three other AGNs are consistent with the presence of the soft excess emission. NGC 4395 with lowest L/LEdd lacks the soft excess emission. Evidently small black mass is not the primary driver of strong soft X-ray excess emission from AGNs. The X-ray spectral properties and optical-to-X-ray spectral energy distributions of these AGNs are similar to those of Seyfert 1 galaxies. The observed X-ray/UV properties of AGNs with IMBHs are consistent with these AGNs being low-mass extensions of more massive AGNs, those with high Eddington luminosity ratio looking more like narrow-line Seyfert 1 s and those with low L/LEdd looking more like broad-line Seyfert 1 galaxies.

Dewangan, G. C.; Mathur, S.; Griffiths, R. E.; Rao, A. R.

2008-12-01

186

Electron optics simulation for designing carbon nanotube based field emission x-ray source  

NASA Astrophysics Data System (ADS)

In this dissertation, electron optics simulation for designing carbon nanotube (CNT) based field emission x-ray source for medical imaging applications will be presented. However, for design optimization of x-ray tubes accurate electron beam optics simulation is essential. To facilitate design of CNT x-ray sources a commercial 3D finite element software has been chosen for extensive simulation. The results show that a simplified model of uniform electron field emission from the cathode surface is not sufficient when compared to experimental measurements. This necessitated the development of a refined model to describe a macroscopic field emission CNT cathode for electron beam optics simulations. The model emulates the random distribution of CNTs and the associated variation of local field enhancement factor. The main parameter of the model has been derived empirically from the experimentally measured I-V characteristics of the CNT cathode. Simulation results based on this model agree well with experiments which include measurements of the transmission rate and focus spot size. The model provides a consistent simulation platform for optimization of electron beam optics in CNT x-ray source design. A systematic study of electron beam optics in CNT x-ray tubes led to the development of a new generation of compact x-ray source with multiple pixels. A micro focus field emission x-ray source with a variable focal spot size has been fully characterized and evaluated. It has been built and successfully integrated into micro-CT scanners which are capable of dynamic cardiac imaging of free-breathing small animals with high spatial and temporal resolutions. In addition a spatially distributed high power multi-beam x-ray source has also been designed and integrated into a stationary digital breast tomosynthesis (s-DBT) configuration. This system has the potential to reduce the total scan time to 4 seconds and yield superior image quality in breast imaging.

Sultana, Shabana

187

The Discontinuous Drop in B Giant X-ray Emission at Spectra Type B1  

Microsoft Academic Search

B supergiants display a discontinuous drop in X-ray emission along a dividing line in the H-R diagram (analogous to the one for K giants) which is clearly related to the bi-stability jump (BSJ) at spectral type B1. Our study revealed several interesting and unexpected results, but some uncertainties have arisen since B supergiant winds are thick to soft X-rays. We

Wayne Waldron

2008-01-01

188

A Study of the Discontinuous Drop in X-ray Emission at Spectral Type B1  

Microsoft Academic Search

B supergiants display a discontinuous drop in X-ray emission along a dividing line in the H-R diagram (analogous to the one for K giants) which is referred to as the bistability jump at spectral type B1. Our XMM study of the X-ray properties on both sides of the jump have revealed several interesting results, but some uncertainties have arisen since

Wayne Waldron

2006-01-01

189

Supernova Remnants in the Sedov Expansion Phase: Thermal X-Ray Emission  

Microsoft Academic Search

Improved calculations of X-ray spectra for supernova remnants (SNRs) in the\\u000aSedov-Taylor phase are reported, which for the first time include reliable\\u000aatomic data for Fe L-shell lines. This new set of Sedov models also allows for\\u000aa partial collisionless heating of electrons at the blast wave and for energy\\u000atransfer from ions to electrons through Coulomb collisions. X-ray emission

Kazimierz J. Borkowski; William J. Lyerly; Stephen P. Reynolds

2000-01-01

190

Femtosecond laser induced X-ray emission from metal alloys, polymers and color filters  

Microsoft Academic Search

Various material surfaces were irradiated on a moving stage with focused laser pulses from a conventional 1kHz femtosecond laser system, and X-ray emission spectra were measured during the laser ablation of the materials. Sharp K or L characteristic X-ray lines from the elements contained in the materials were clearly observed in a range of 2–15keV. Signals due to copper and

Koji Hatanaka; Ken-Ichiro Yomogihata; Hiroshi Ono; Hiroshi Fukumura

2005-01-01

191

Angular distribution of X-ray emission from resonant coherently excited highly-charged heavy ions  

Microsoft Academic Search

X-rays emitted from resonant coherently excited (RCE) n=2 states of 390 MeV\\/amu hydrogen-like Ar17+ ions were observed under planar channeling in a Si crystal. The resonance profiles for X-ray emission consisting of two peaks for j=1\\/2 and j=3\\/2 are characterized by suppression of the j=1\\/2 peak. The degeneracy of the n=2 states are removed by Stark effect due to the

T. Azuma; T. Muranaka; Y. Takabayashi; T. Ito; C. Kondo; K. Komaki; Y. Yamazaki; S. Datz; E. Takada; T. Murakami

2003-01-01

192

Charge Transfer Excitation in Resonant X-ray Emission Spectroscopy of NiO  

Microsoft Academic Search

We analyze Ni 2 p \\\\to 3d \\\\to 2 p resonant X-ray emission spectroscopy (RXES) of NiO with the impurity Anderson model. We pay attention to the inelastic X-ray scattering structures arising from the interatomic charge transfer (CT) from ligand state to 3d state. We take into account a finite width of the O 2 p valence band in order

Masahiko Matsubara; Takayuki Uozumi; Akio Kotani; Jean Claude Parlebas

2005-01-01

193

X-Ray Emission-Line Imaging and Spectroscopy of Tycho's Supernova Remnant  

Microsoft Academic Search

We present X-ray images of Tycho's supernova remnant in emission-line features of Mg, Si, S, Ar, Ca, and Fe, plus the continuum, using data obtained by the imaging spectrometers on board the Advanced Satellite for Cosmology and Astrophysics (ASCA). All the images show the shell-like morphology characteristic of previously obtained broadband X-ray images, but they are clearly distinct from each

Una Hwang; Eric V. Gotthelf

1997-01-01

194

Observation of x-ray emission differences heating by high power laser and x-ray pulses  

Microsoft Academic Search

Au x-ray transmission grating and an x-ray streak camera are combined to provide a time-resolved diagnostic of a subkilovolt x-ray spectrum, which gives time resolution of about 30 ps and moderate spectral resolution of 0.4-0.5 nm. Two types of cavity targets representing laser heating area and radiation heating are designed for experiment on LF-12 laser facility, and the laser pulses

Wenyong Miao; Haien He; Zhongli Liu; Yaonan Ding; Hu Xin; Zhijian Zheng; Daoyuan Tang; Hansheng Peng

1997-01-01

195

An X-Ray Detected Group of Quiescent Early-Type Galaxies at z = 1.6 in the Chandra Deep Field South  

NASA Astrophysics Data System (ADS)

We report the discovery of an X-ray group of galaxies located at a high redshift of z = 1.61 in the Chandra Deep Field South. Based on 4 Ms Chandra data, the group is first identified as an extended X-ray source. We have used a wealth of deep multi-wavelength data to identify the optical counterpart - our red sequence finder detects a significant over-density of galaxies at z ˜1.6. The brightest group galaxy is spectroscopically confirmed at z = 1.61, based on published spectroscopic redshifts. Using this as a central redshift of the group, we measure an X-ray luminosity of L0.1-2.4keV = (1.8±0.6) × 1043 erg s-1, which then translates into a group mass of (3.2±0.8) × 1013 M?. This is the lowest-mass group ever confirmed at z > 1.5. Deep optical-nearIR images from CANDELS reveal that the group exhibits a surprisingly prominent red sequence, and most of the galaxies are consistent with a formation redshift of zf = 3. A detailed analysis of the spectral energy distributions of the group member candidates confirms that most of them are indeed passive galaxies. Furthermore, their structural parameters measured from near-IR CANDELS images show that they are morphologically early-type. The newly identified group at z = 1.61 is dominated by quiescent early-type galaxies, and the group appears to be similar to those in the local Universe. One possible difference is the high fraction of AGN - 38+23-20% of the bright group member candidates are AGN, which might indicate a role for AGN in the quenching of star formation. However, a statistical sample of high-z groups is needed to draw a general picture of groups at this redshift. Such a sample will hopefully be available in near-future surveys.

Tanaka, Masayuki; Finoguenov, Alexis; Mirkazemi, Mohammad; Wilman, David J.; Mulchaey, John S.; Ueda, Yoshihiro; Xue, Yongquan; Brandt, William N.; Cappelluti, Nico

2013-02-01

196

Chandra X-ray Grating Spectrometry of Eta Carinae near X-ray Minimum: I. Variability of the Sulfur and Silicon Emission Lines  

Microsoft Academic Search

We report on variations in important X-ray emission lines in a series of\\u000aChandra grating spectra of the supermassive colliding wind binary star Eta\\u000aCarinae, including key phases around the X-ray minimum\\/periastron passage in\\u000a2003.5. The X-rays arise from the collision of the slow, dense wind of Eta Car\\u000awith the fast, low-density wind of an otherwise hidden companion star.

D. B. Henley; M. F. Corcoran; J. M. Pittard; I. R. Stevens; K. Hamaguchi; T. R. Gull

2008-01-01

197

Jet-linked X-ray emission in radio-loud broad absorption line (BAL) quasars  

NASA Astrophysics Data System (ADS)

We have applied theoretical models to explain spectral energy distribution (SED) of three radio-loud broad absorption line (BAL) quasars: an extended hybrid object PG 1004+130 and two compact sources 1045+352 and 3C270.1. We calculate the emission from the very inner part of the sources which accounts for more than 90% of the observed X-ray radiation. In our analysis we consider a scenario in which the observed X-ray emission comes from the inverse-Compton (IC) scattering inside a jet and from the accretion disk corona. The compact objects 1045+352 and 3C270.1 are high-redshift quasars (z = 1.604 and 1.532 respectively), with strong radio cores. We argue that in the case of these two sources a non-thermal, inverse-Compton emission from the innermost parts of the jet can explain a large fraction of the observed X-ray emission. The large scale object PG 1004+130 with a peculiar radio morphology is a low-redshift (z = 0.24), lobe-dominated BAL quasar with a weak radio core. In this case simulated inverse-Compton X-ray emission of the jet is relatively low. However, the corona emission appears strong enough to explain the observed X-ray spectrum of this object.

Kunert-Bajraszewska, M.; Katarzy?ski, K.; Janiuk, A.; Ceg?owski, M.

2013-02-01

198

X-ray emission from the winds of hot stars  

SciTech Connect

A phenomenological theory is proposed for the structure of the unstable line-driven winds of early-type stars. These winds are conjectured to break up into a population of blobs that are being radiatively driven through, and confined by ram pressure of, an ambient gas that, because of shadowing by the blobs, is not itself being radiatively driven. With plausible choices for the theory's two free parameters, radiation from the bow shocks preceding the blobs can account for the X-ray luminosity of zeta Puppis. The theory breaks down, however, when used to model the much lower density wind of tau Scorpii, for then the blobs are destroyed by heat conduction from shocked gas. This effect appears to explain why the profiles of this star's UV resonance lines depart from classical P Cygni form.

Lucy, L.B.; White, R.L.

1980-10-01

199

Swift Observations Of Cometary X-ray And Uv Emission  

NASA Astrophysics Data System (ADS)

The abundance of native ices in comet nuclei is a fundamental observational constraint in cosmogony. An important unresolved question is the extent to which the composition of pre-cometary ices varied with distance from the young sun. Our fundamental objective is to build a taxonomy based on cometary volatile composition instead of orbital dynamics. Secondly, the interaction of the solar wind with the planets, moons and the interstellar medium is of key importance for understanding the evolution of our solar system. Solar wind-atmosphere interactions can be studied particularly well in comets, because in that case the solar wind flow is not attenuated by a planetary magnetic field and interacts directly with its atmosphere, the coma. When solar wind ions fly through an atmosphere they are neutralized via charge exchange reactions with the neutral gaseous species. These reactions depend strongly on target species and collision velocity and the resulting X-rays are a strong diagnostic of local solar wind conditions and of bulk properties of the cometary gas. The Swift space telescope is unique in combining UV and X-ray instruments. Its grisms (175-520 nm) encompass known cometary fluorescence bands (e.g., CO2+, OH, CO, NH, CS, CN, etc.) that can quantify and track the water and organic ice chemistry in the coma. Swift's multi-wavelength approach allows linking the behavior of comets and the solar wind. Here, we present Swift observations of comets 8P/Tuttle and 73P/Schwassmann-Wachmann, and discuss our findings in terms local space weather and comet composition.

Bodewits, Dennis; Villanueva, G. L.; Mumma, M. J.; Brown, G. V.; Porter, S.; Landsman, W.

2008-03-01

200

Electronic Excitations in Vanadium Oxide Phthalocyanine Studied via Resonant Soft X-ray Emission and Resonant Inelastic X-ray Scattering  

SciTech Connect

The electronic structure of the organic semiconductor vanadium oxide phthalocyanine has been studied using resonant inelastic X-ray scattering and X-ray emission spectroscopy. The vanadyl species in the films is shown to be highly localized, and good agreement between the measurements and a density functional calculation is obtained. Both dipole forbidden V 3d to V 3d*, and O 2p to V 3d* charge transfer transitions are observed, and explained in a local molecular orbital model.

Zhang,Y.; Wang, S.; Learmonth, T.; Plucinski, L.; Matsuura, A.; Bernardis, S.; ODonnell, C.; Downes, J.; Smith, K.

2005-01-01

201

Electronic structure and optical properties of silicon nanowires: A study using x-ray excited optical luminescence and x-ray emission spectroscopy  

Microsoft Academic Search

We report a soft x-ray excited optical luminescence (XEOL) and x-ray emission spectroscopy (XES) study of silicon nanowires (SiNW) with excitations at the silicon K and L3,2 edge, respectively. It is found that the XEOL of SiNW exhibits several luminescence bands at ˜460 , ˜530 , and ˜630nm . These luminescence bands are broad and are sensitive to the Si1s

T. K. Sham; S. J. Naftel; P.-S. G. Kim; R. Sammynaiken; Y. H. Tang; I. Coulthard; A. Moewes; J. W. Freeland; Y.-F. Hu; S. T. Lee

2004-01-01

202

The extended X-ray emission around RRAT J1819-1458  

NASA Astrophysics Data System (ADS)

We present new imaging and spectral analysis of the recently discovered extended X-ray emission around the high magnetic field rotating radio transient RRAT J1819-1458. We used two Chandra observations performed for this object in 2008 May 31 and 2011 May 28, respectively. The diffuse X-ray emission was detected with a significance of ˜19? in the image obtained by combining the two observations. Neither long-term spectral nor timing variability has been observed from the source or the nebula. RRAT J1819-1458 shows an unusual high X-ray efficiency of ? X equiv L_{X(0.3-5 keV)}/skew4dot{E}_rot ˜ 0.15 at converting spin-down power into X-ray luminosity. The most favourable scenario for the origin of this extended X-ray emission is either a pulsar wind nebula or a scattering halo. A magnetically powered scenario for the extended emission is viable only in the case of a Compton nebula, while it can be tentatively disfavoured in the case of synchrotron emission.

Camero-Arranz, A.; Rea, N.; Bucciantini, N.; McLaughlin, M. A.; Slane, P.; Gaensler, B. M.; Torres, D. F.; Stella, L.; de Oña, E.; Israel, G. L.; Camilo, F.; Possenti, A.

2013-03-01

203

A HARD AND VARIABLE X-RAY EMISSION FROM THE MASSIVE EMISSION-LINE STAR HD 157832  

SciTech Connect

We report the discovery with XMM-Newton of a hard-thermal (T {approx} 130 MK) and variable X-ray emission from the Be star HD 157832, a new member of the puzzling class of {gamma}-Cas-like Be/X-ray systems. Recent optical spectroscopy reveals the presence of a large/dense circumstellar disk seen at intermediate/high inclination. With a B1.5V spectral type, HD 157832 is the coolest {gamma}-Cas analog known. In addition, its non-detection in the ROSAT all-sky survey shows that its average soft X-ray luminosity varied by a factor larger than {approx}3 over a time interval of 14 yr. These two remarkable features, 'low' effective temperature, and likely high X-ray variability turn HD 157832 into a promising object for understanding the origin of the unusually high-temperature X-ray emission in these systems.

Lopes de Oliveira, R. [Universidade de Sao Paulo, Instituto de Fisica de Sao Carlos, Caixa Postal 369, 13560-970, Sao Carlos, SP (Brazil); Motch, C. [Universite de Strasbourg, CNRS UMR 7550, Observatoire Astronomique, 11 rue de l'Universite, F67000 Strasbourg (France)

2011-04-10

204

Quiescent Diffusive and Fumarolic Volcanic Bromocarbon Emissions  

NASA Astrophysics Data System (ADS)

Future scenarios of declining atmospheric burdens of Ozone Depleting Substances (ODS) such as halocarbons after phase-out following international regulation (Montreal Protocol) vary strongly depending on what contribution from natural sources is taken into account. In addition, current and pre-industrial global atmospheric budgets of ODS are poorly balanced by known natural and anthropogenic sources of halocarbons (Butler, 2000). Brominated halocarbons have a high Ozone Depletion Potential, Br is at least 40x as efficient as Cl in polar stratospheric ozone destruction (Solomon et al., 1992). CH3Br is the dominant Br carrier to the stratosphere with sources being ca.: 32% anthropogenic, 39% natural, but ca. 29% unaccounted for (WMO, 1998). Natural sources have been reviewed recently (Gribble, 2000, Butler, 2000), including magmatic inorganic (Bureau, 2000) and volcanic organic sources (Rassmussen et al., 1980; Schwandner et al., 2002). CH3Br and other bromocarbons have been reported in non-eruptive volcanic gases previously (Jordan et al., 2000; Schwandner et al., 2000). Due to its capability to extremely rapidly hydrolyse (Gan et al., 1995), CH3Br should not be sampled by the caustic soda bottle technique as used by Jordan et al. (2000) whose samples also show signs of air contamination, but by cryogenic separation of steam with subsequent sorbent trapping, as used by Isidorov (1990), Wahrenberger (1996) and Schwandner et al. (2000, 2001). To contribute significantly to the natural Br budget, volcanic gases would have to at least contain 2 ppmv (dry gas) CH3Br, scaled to a global CO2 emission of 66 Tgy-1 (Stoiber, 1995) based on CO2 flux to halocarbon concentration correlations (e.g. CFC-11: R2=0.91, Schwandner et al., 2002). However, CH3Br is not the only volcanogenic bromocarbon. Analysis of diffusive flank and crater degassing on Vulcano island (Italy) showed a strong diffusive component of CH3Br and C2H5Br emissions in 60-100°C hot pristine unvegetated volcanic "soil" close to high-temperature fumaroles. Other ODS found significantly above air, field and analytical system blanks include CH3Cl, CH3I, chlorophenols and chlorobenzenes. Abundances range from upper pptv to ppmv (e.g. CFC-11: max. 1200 pptv diffusive, 3700 pptv fumarolic/dry gas, dry air: 268 pptv). References\\ Bureau H. et al. (2000), EPSL 183 (1-2):51-60.\\Butler J.H. (2000), Nature 403:560-261.\\Gan J. Y. et al. (1995), J. Agric. Food Chem. 43:1361-1367.\\Gribble G. W. (2000), Environ. Sci. Pollut. Res. 7(1), 37-49.\\Isidorov V. A. et al. (1990), J. Atmos. Chem. 10(3):329-340.\\Jordan A. et al.(2000), ES&T 34:1122-1124.\\Rasmussen R. A. et al. (1980), EOS Transact. 61(6):67.\\Schwandner F. M. et al. (2000), J. Conf. Abs. 5(2):898.\\Schwandner F. M. et al. (2001), Chimia 55(7-8):590.\\Schwandner F.M. et al. (2002), Geoch. Soc. Spec. Publ. 8 (subm.).\\Solomon S. et al. (1992), JGR-A. 97:825-842.\\Stoiber R. E. (1995), In: A handbook of physical constants, AGU Reference Shelf 1:308-319.\\Wahrenberger C. et al. (1996), EOS Trans. 77(46):804.\\WMO (1998) Scientific assessment of ozone depletion. WMO Rep. No. 44, World Meteorological Organisation (WMO), Geneva.

Schwandner, F. M.; Gi?e, A. P.; Seward, T. M.; Hall, P. A.; Dietrich, V. J.

2002-12-01

205

Linking jet emission and X-ray properties in the peculiar neutron star X-ray binary Circinus X-1  

NASA Astrophysics Data System (ADS)

We present the results of simultaneous X-ray and radio observations of the peculiar Z-type neutron star X-ray binary Cir X-1, observed with the Rossi X-ray Timing Explorer satellite and the Australia Telescope Compact Array in 2000 October and 2002 December. We identify typical Z-source behaviour in the power density spectra as well as characteristic Z patterns drawn in an X-ray hardness-intensity diagram. Power spectra typical of bright atoll sources have also been identified at orbital phases after the periastron passage, while orbital phases before the periastron passage are characterized by power spectra that are typical neither of Z nor of atoll sources. We investigate the coupling between the X-ray and the radio properties, focusing on three orbital phases when an enhancement of the radio flux density has been detected, to test the link between the inflow (X-ray) and the outflow (radio jet) to/from the compact object. In two out of three cases, we associate the presence of the radio jet to a spectral transition in the X-rays, although the transition does not precede the radio flare, as detected in other Z sources. An analogous behaviour has recently been found in the black hole candidate GX 339-4. In the third case, the radio light curve shows a similar shape to the X-ray light curve. We discuss our results in the context of jet models, considering also black hole candidates.

Soleri, Paolo; Tudose, Valeriu; Fender, Rob; van der Klis, Michiel; Jonker, Peter G.

2009-10-01

206

X-ray emission of a representative sample of local Luminous Infrared Galaxies  

NASA Astrophysics Data System (ADS)

We propose to observe with XMM-Newton 8 Luminous Infrared Galaxies (LIRGs, L_IR=10^11-10^12L_sun) and analyze existing X-ray data for another 7 LIRGs. Previous X-ray studies of local LIRGs are biased towards the most IR-luminous objects as well as those systems hosting a bright AGN. These 15 local LIRGs are representative of the LIRG class in terms of IR luminosity and nuclear activity. The proposed XMM observations together with existing multi-wavelength (UV to IR) data will allow to characterize the star formation history of these galaxies and relate it to their X-ray emission. A comprehensive multi-wavelength understanding of the extreme processes (star formation and AGN) taking place in local LIRGs is needed to improve the linkage of X-ray, UV and IR observations of deep cosmological fields.

Alonso-Herrero, Almudena

2007-10-01

207

Specific features of thermocouple calorimeter application for measurements of pulsed X-ray emission from plasma  

NASA Astrophysics Data System (ADS)

It is shown that the accuracy of time-integrated measurements of pulsed X-ray emission from hot plasma with calibrated thermocouple calorimeters is mainly determined by two factors. The first and the most important factor is heating of the filter by the absorbed X-rays; as a result, the calorimeter measures the thermal radiation of the filter, which causes appreciable distortion of the temporal profile and amplitude of the recorded signal. The second factor is the dependence of the effective depth of X-ray absorption in the dielectric that covers the entrance window of the calorimeter on the energy of X-ray photons, i.e., on the recorded radiation spectrum. The results of model calculations of the calorimeter signal are compared with the experimental data.

Gavrilov, V. V.; Fasakhov, I. K.

2012-01-01

208

Framed, 16-image, Kirkpatrick-Baez microscope for laser-plasma x-ray emission  

SciTech Connect

A framed, 16-image, Kirkpatrick-Baez (KB)-type x-ray microscope has been designed for use in imaging laser-plasma x-ray emission. The reflecting elements are 16 pairs of concave mirrors arranged to reflect and focus x rays emanating from a laser-produced plasma. The resolution of the elements is 3 {mu}m at best focus and is better than 5 {mu}m within a 400-{mu}m-diam region. A framing camera will be used in combination with the KB optic to produce 16 gated x-ray images in the energy range from 1.5 to 7 keV over a typical interval of 1.5 ns. This system is designed for use on the University of Rochester's OMEGA laser facility [T. R. Boehly et al., Opt Commun. 133, 495 (1997)].

Marshall, F.J.; Oertel, J.A.; Walsh, P.J. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2004-10-01

209

Study of X-ray emission from plasma focus device using vacuum photodiode  

NASA Astrophysics Data System (ADS)

A newly fabricated vacuum photodiode (VPD) is used to measure time resolved X-ray emission and electron temperature from plasma focus device operated in hydrogen medium. The VPD signals are compared with the PIN diode signal and observed to be of similar in nature. The acquired signals from VPD are deduced to measure electron temperature and X-ray radiated power for four different anode tips (cylindrical, diverging, oval and converging). The electron temperatures are found to be 0.64, 1.5, 0.60 and 0.55 keV for cylindrical, diverging, oval and converging anode tips respectively in hydrogen plasma. The X-ray radiated powers are observed to be varying with respect to the shape of the anode tips and it is found highest in case of converging tip and lowest for the diverging one. Results indicate that VPD could efficiently be employed as an X-ray diagnostics in plasma focus device.

Talukdar, N.; Borthakur, T. K.; Neog, N. K.

2013-10-01

210

Investigating the reflection contribution to the X-ray emission of Ton S180  

NASA Astrophysics Data System (ADS)

There is now growing evidence that the soft X-ray excess is almost ubiquitous among unobscured active galaxies. In spite of the various interpretations that have been considered in the past few years, the nature of this foremost spectral feature is not firmly established yet. In this context, we review from a reflection perspective the three highest quality X-ray observations of the narrow-line type 1 Seyfert galaxy Tonantzintla (Ton) S180, obtained by XMM-Newton and Suzaku. The X-ray spectrum of Ton S180 shows only moderate variations over a time span of several years, suggesting that the same physical process accounts for the bulk of the broad-band X-ray emission at the different epochs, and that the properties of the X-ray source are fairly stable. We have successfully applied in our spectral analysis a dual-reflector model, consisting of two separate components: one arises from the surface of the accretion disc, is highly ionized and blurred by relativistic effects; the other is cold, quite faint and can be associated with a distant reprocessor. Due to the strength and the nearly power-law shape of its soft excess emission, Ton S180 is one of the most challenging sources to test the X-ray reflection scenario. In this work we provide a clear illustration of the great potential and spectral flexibility of blurred reflection models, while discussing some of their current limitations and possible shortcomings.

Nardini, E.; Fabian, A. C.; Walton, D. J.

2012-07-01

211

The evolution of the X-ray emission of HH 2. Investigating heating and cooling processes  

NASA Astrophysics Data System (ADS)

Young stellar objects often drive powerful bipolar outflows, which evolve on timescales of a few years. An increasing number of these outflows has been detected in X-rays implying the existence of million degree plasma almost co-spatial with the lower temperature gas observed in the optical and near-infrared. The details of the heating and cooling processes of the X-ray emitting part of these so-called Herbig-Haro objects are still ambiguous, e.g., whether the cooling is dominated by expansion, radiation, or thermal conduction. We present a second epoch Chandra observation of the first X-ray detected Herbig-Haro object (HH 2) and derive the proper-motion of the X-ray emitting plasma and its cooling history. We argue that the most likely explanation for the constancy of the X-ray luminosity, the alignment with the optical emission and the proper-motion is that the cooling is dominated by radiative losses leading to cooling times exceeding a decade. We explain that a strong shock caused by fast material ramming into slower gas in front of it about ten years ago can explain the X-ray emission while being compatible with the available multi-wavelength data of HH 2.

Schneider, P. C.; Günther, H. M.; Schmitt, J. H. M. M.

2012-06-01

212

Attenuation correction of SPECT using X-ray CT on an emission-transmission CT system: myocardial perfusion assessment  

Microsoft Academic Search

The authors present experimental results for attenuation correction of emission tomography through use of an attenuation map derived from X-ray CT data. The X-ray and gamma-ray data were obtained from a third-generation X-ray CT scanner and a single-headed SPECT Scanner juxtaposed to enable systematic registration of SPECT and X-ray CT Images. CT measurements were obtained from known materials at a

S. C. Blankespoor; X. Xu; K. Kaiki; J. K. Brown; H. R. Tang; C. E. Cann; B. H. Hasegawa

1996-01-01

213

X-ray emission from galaxies - The X-ray emission in a sample of close pairs of galaxies  

NASA Astrophysics Data System (ADS)

We analyse XMM-Newton and Chandra observations of close interacting pairs of galaxies of similar size (major mergers). The pairs analysed are nearby (z < 0.1), with a range of projected separations between about 5 and 100 kpc. X-rays can unveil hidden active nuclei, providing a way to discover dual AGN, and to characterize the galaxies activity as function of the galaxies morphologies, the galaxies mass, and the merger stage as indicated by the pair separation, and the presence of tails and bridges in different wavelengths. The characterization of the nuclear activity in pairs of interacting galaxies is relevant to the understanding of the role of the interactions in the triggering of AGN activity in one or both of the galaxies.

Loiseau, Nora; Jiménez-Bailón, E.; Tomás, L.; Piconcelli, E.; Guainazzi, M.; Santos Lleó M.

2012-09-01

214

X-ray Emission of OVII and OVIII Ions Induced in Heliosphere by the Solar Wind  

NASA Astrophysics Data System (ADS)

The spectroscopy of excited O*6+ and O*7+ SW ions is investigated as a diagnostic of astrophysical plasmas. The emission spectra of highly charged oxygen ions, induced by the Solar Wind (SW) interacting with the heliospheric H and He gas and cometary and planetary atmospheres, are calculated. Absolute and relative intensities of the X-ray emission lines induced in the charge-exchange collisions of bare O8+ and hydrogenic O7+ oxygen ions with neutral atoms are computed and compared with the results of observations with the Chandra and XMM-Newton X-ray telescopes. Charge- exchange X-ray and EUV emissions produced by the slow and fast solar winds are predicted. An analysis of X-ray photon spectra detected from the interstellar gas and cometary and planetary atmospheres is carried out to determine the parameters of the interacting SW plasma and neutral gas. The contribution of charge- exchange mechanism of O*6+ and O*7+ emissions to the soft X-ray background is discussed.

Kharchenko, V.; Dalgarno, A.

2006-05-01

215

X-RAY EMISSION FROM SN 2004dj: A TALE OF TWO SHOCKS  

SciTech Connect

Type IIP (Plateau) supernovae are the most commonly observed variety of core-collapse events. They have been detected in a wide range of wavelengths from radio, through optical to X-rays. The standard picture of a Type IIP supernova has the blastwave interacting with the progenitor's circumstellar matter to produce a hot region bounded by a forward and a reverse shock. This region is thought to be responsible for most of the X-ray and radio emission from these objects. Yet the origin of X-rays from these supernovae is not well understood quantitatively. The relative contributions of particle acceleration and magnetic field amplification in generating the X-ray and radio emission need to be determined. In this work, we analyze archival Chandra observations of SN 2004dj, one of the nearest supernovae since SN 1987A, along with published radio and optical information. We determine the pre-explosion mass-loss rate, blastwave velocity, electron acceleration, and magnetic field amplification efficiencies. We find that a greater fraction of the thermal energy goes into accelerating electrons than into amplifying magnetic fields. We conclude that the X-ray emission arises out of a combination of inverse Compton scattering by non-thermal electrons accelerated in the forward shock and thermal emission from supernova ejecta heated by the reverse shock.

Chakraborti, Sayan; Yadav, Naveen; Ray, Alak [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Colaba, Mumbai 400 005 (India); Smith, Randall [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Chandra, Poonam [Department of Physics, Royal Military College of Canada, Kingston, ON K7K 7B4 (Canada); Pooley, David, E-mail: schakraborti@fas.harvard.edu [Department of Physics, Sam Houston State University, Huntsville, TX (United States)

2012-12-20

216

X-ray emission from relativistically moving electron density cusps  

NASA Astrophysics Data System (ADS)

We report on novel methods to generate ultra-short, coherent, X-rays using a laserplasma interaction. Nonlinear interaction of intense laser pulses with plasma creates stable, specific structures such as electron cusps. For example, wake waves excited in an underdense plasma by an intense, short-pulse laser become dense and propagate along with the laser pulse. This is called a relativistic flying mirror. The flying mirror can reflect a counter-propagating laser pulse and directly convert it into high-frequency radiation, with a frequency multiplication factor of ~ 4?2 and pulse shortening with the same factor. After the proof-of-principle experiments, we observed that the photon number generated in the flying mirror is close to the theoretical estimate. We present the details of the experiment in which a 9 TW laser pulse focused into a He gas jet generated the Flying Mirror, which partly reflected a 1 TW pulse, giving up to ~ 1010 photons, 60 nJ (1.4×1012 photons/sr) in the XUV spectral region (12.8-22 nm).

Kando, M.; Pirozhkov, A. S.; Nakamura, T.; Hayashi, Y.; Kotaki, H.; Kawase, K.; Esirkepov, T. Zh.; Fukuda, Y.; Kiriyama, H.; Okada, H.; Daito, I.; Kameshima, T.; Mori, M.; Koga, J. K.; Daido, H.; Faenov, A. Ya.; Pikuz, T.; Ma, J.; Chen, L.-M.; Ragozin, E. N.; Kawachi, T.; Kato, Y.; Tajima, T.; Bulanov, S. V.

2012-07-01

217

High-energy neutrino emission from x-ray binaries  

SciTech Connect

We show that high-energy neutrinos can be efficiently produced in X-ray binaries with relativistic jets and high-mass primary stars. We consider a system where the star presents a dense equatorial wind and the jet has a small content of relativistic protons. In this scenario, neutrinos and correlated gamma-rays result from pp interactions and the subsequent pion decays. As a particular example we consider the microquasar LS I +61 303. Above 1 TeV, we obtain a mean-orbital {nu}{sub {mu}}-luminosity of {approx}5 10{sup 34} erg/s which can be related to an event rate of 4-5 muon-type neutrinos per kilometer-squared per year after considering the signal attenuation due to maximal neutrino oscillations. The maximal neutrino energies here considered will range between 20 and 85 TeV along the orbit. The local infrared photon field is responsible for opacity effects on the associated gamma radiation at high energies, but below 50 GeV the source could be detected by MAGIC telescope. GLAST observations at E{sub {gamma}}>100 MeV should also reveal a strong source.

Christiansen, Hugo R. [State Univesity of Ceara, Physics Dept., Av. Paranjana 1700, 60740-000, Fortaleza - CE (Brazil); Orellana, Mariana; Romero, Gustavo E. [Instituto Argentino de Radioastronomia (IAR), C.C. 5, 1894, Villa Elisa - Bs.As. (Argentina)

2006-03-15

218

X-ray emission from relativistically moving electron density cusps  

SciTech Connect

We report on novel methods to generate ultra-short, coherent, X-rays using a laserplasma interaction. Nonlinear interaction of intense laser pulses with plasma creates stable, specific structures such as electron cusps. For example, wake waves excited in an underdense plasma by an intense, short-pulse laser become dense and propagate along with the laser pulse. This is called a relativistic flying mirror. The flying mirror can reflect a counter-propagating laser pulse and directly convert it into high-frequency radiation, with a frequency multiplication factor of {approx} 4{gamma}{sup 2} and pulse shortening with the same factor. After the proof-of-principle experiments, we observed that the photon number generated in the flying mirror is close to the theoretical estimate. We present the details of the experiment in which a 9 TW laser pulse focused into a He gas jet generated the Flying Mirror, which partly reflected a 1 TW pulse, giving up to {approx} 10{sup 10} photons, 60 nJ (1.4 Multiplication-Sign 10{sup 12} photons/sr) in the XUV spectral region (12.8-22 nm).

Kando, M.; Pirozhkov, A. S.; Nakamura, T.; Hayashi, Y.; Kotaki, H.; Kawase, K.; Esirkepov, T. Zh.; Fukuda, Y.; Kiriyama, H.; Okada, H.; Daito, I.; Kameshima, T.; Mori, M.; Koga, J. K.; Daido, H.; Faenov, A. Ya.; Pikuz, T.; Ma, J.; Chen, L.-M.; Ragozin, E. N. [Japan Atomic Energy Agency (Japan); Osaka University (Japan); Joint Institute for High Temperature of the Russian Academy of Science, Moscow (Russian Federation); Institute of Physics, Chinese Academy of Sciences, Beijing (China); P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Leninsky prospekt 53, 119991 Moscow (Russian Federation); Japan Atomic Energy Agency and Graduate School for the Creation of New Photonics Industries (Japan); Ludwig-Maximilians-University (Germany); and others

2012-07-11

219

High resolution krypton M/sub 4,5/ x-ray emission spectra  

SciTech Connect

High resolution M/sub 4,5/ (3d ..-->.. 4p) x-ray emission spectra from a krypton plasma were measured using a recently developed grazing-incidence reflection-grating monochromator/spectrometer with very high flux rates at extreme ultraviolet and soft x-ray wave lengths. The nominal resolving power of the instrument, E/..delta..E, is about 300 in this energy range (approx.80 eV). Three dipole-allowed 3d ..-->.. 4p emission lines were observed at 80.98 eV, 80.35 eV and 79.73 eV. A broad peak at about 82.3 eV is tentatively assigned to transitions resulting from Kr/sup 2 +/, and effects of excitation energy on M/sub 4,5/ x-ray emission were observed. 9 refs., 3 figs., 1 tab.

Perera, R.C.C.; Hettrick, M.C.; Lindle, D.W.

1987-10-01

220

X-ray emission from the magnetic star alpha ^2 Canum Venaticorum ?  

NASA Astrophysics Data System (ADS)

We propose a 15 ksec pilot study with Chandra ACIS-S of the visual binary system alpha^2 CVn (= HR~4915 and HR~4914). With an angular separation of ˜ 21.3 arcsec this system can be easily resolved with Chandra. X-ray emission from alpha^2 CVn has been detected with the Einstein Observatory IPC and in the ROSAT RASS data, however, the angular resolution of these data is insufficient to attribute the detected X-ray emission to the F0 component HR~4914 or the A0spe component HR~4915. Since HR~4915 has a measured magnetic field of a few kG, the correct attribution of the detected X-ray emission has far reaching consequences. With the proposed 15 ksec ACIS-S pilot study at the binary HR~4914/4915 we can provide the feasibility of a possible grating observation.

Rgen Schmitt, J.

2008-09-01

221

X-ray Spontaneous Emission Control By 1D-PBG Structure  

SciTech Connect

The control of the decay rate of an excited atom through the photonic mode density (PMD) was pointed out at radiofrequency by Purcell in 1946. Nowadays the development of sophisticated photonic band structures makes it possible to monitor the PMD at shorter radiation wavelengths and then to manipulate the spontaneous emission of atoms in the hard region of the electromagnetic spectrum especially in the visible domain. In this communication we study the possibility of monitoring the x-ray emission by means of one-dimensional photonic band structures such as periodic multilayer systems. Enhancement or inhibition of soft x-ray emissions seems now to be feasible by means of the state-of-the art in x-ray optics.

Andre, Jean-Michel; Jonnard, Philippe [Laboratoire de Chimie Physique-Matiere et Rayonnement, CNRS, Universite Paris 6, UMR 7614, 11 rue Pierre et Marie Curie, F-75231 Paris CEDEX 05 (France)

2010-04-06

222

Two-photon-induced x-ray emission in neon atoms  

SciTech Connect

We investigated the resonant x-ray emission from a neon atom induced by the two-photon population of a double-core-hole excited state. Two qualitatively different schemes of this process are studied: The first one involves an off-resonant intermediate single-core-hole state; the second scheme passes through a resonant core-ionized intermediate state. The numerical simulations of the resonant x-ray emission performed for different peak intensities and pulse durations show significant population of the double-core-hole final states. Therefore, rather strong two-photon absorption-induced x-ray emission is predicted for both studied schemes. Thus, high counting rates in experimental measurements are expected.

Sun Yuping; Wang Chuankui [College of Physics and Electronics, Shandong Normal University, 250014 Jinan (China); Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, S-10691 Stockholm (Sweden); Rinkevicius, Zilvinas; Gel'mukhanov, Faris [Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, S-10691 Stockholm (Sweden); Carniato, Stephane; Simon, Marc; Taieeb, Richard [Laboratoire de Chimie Physique Matiere et Rayonnement, Universite Pierre et Marie Curie Universite Paris 06, Unite de Mixte de Recherche (UMR) 7614, F-75005 Paris (France); Laboratoire de Chimie Physique Matiere et Rayonnement, Centre National de la Recherche Scientifique, UMR 7614, F-75005 Paris (France)

2010-10-15

223

Soft X-ray emission as diagnostics for Maunder minimum stars  

NASA Astrophysics Data System (ADS)

The identification of stars in a Maunder minimum state purely from their chromospheric emission (for example in Ca II lines) has proven to be difficult. Photospheric contributions, metallicities and possible deviations from the main sequence stage may lead to very low values of the traditional chromospheric activity indicators, while no Maunder minimum state may be present. X-ray observations can be a key tool for identifying possible Maunder minimum stars: We have detected very soft X-ray emission from low-temperature coronal plasma, similar to emission from solar coronal holes, in several stars with very low chromospheric activity indicators. The coronal properties inferred from X-ray observations can therefore yield a crucial piece of information to verify Maunder minimum states in stars.

Poppenhaeger, Katja; Schmitt, Jürgen H. M. M.

2012-07-01

224

Spectra of the X-ray Emission from the Heliospheric Gas  

NASA Astrophysics Data System (ADS)

Spectra of the heliospheric EUV and X-ray emission induced in the charge-transfer collisions of the highly charged solar wind ions with the interstellar gas have been calculated. Cascading photon spectra of individual Oq+, Cq+, Nq+, and Neq+ ions have been constructed using recent data on ion radiative transition probabilities and the state selective population cross sections for charge-transfer collisions of the most abundant heavy solar wind ions with H and He atoms. Emission spectra have been calculated for slow and fast solar winds interacting with the heliospheric H and He gas. Relative intensities of the brightest lines have been predicted. The volume power distribution of the charge-transfer EUV and X-ray emission has been computed for simplified models of the solar winds and the interstellar gas. X-ray images of the heliosphere have been composed for the region of the heliosphere inside 10 AU from the Sun.

Kharchenko, V.; Dalgarno, A.; Repino, R.; Lallement, R.

2004-12-01

225

X-ray Spontaneous Emission Control By 1D-PBG Structure  

NASA Astrophysics Data System (ADS)

The control of the decay rate of an excited atom through the photonic mode density (PMD) was pointed out at radiofrequency by Purcell in 1946. Nowadays the development of sophisticated photonic band structures makes it possible to monitor the PMD at shorter radiation wavelengths and then to manipulate the spontaneous emission of atoms in the hard region of the electromagnetic spectrum especially in the visible domain. In this communication we study the possibility of monitoring the x-ray emission by means of one-dimensional photonic band structures such as periodic multilayer systems. Enhancement or inhibition of soft x-ray emissions seems now to be feasible by means of the state-of-the art in x-ray optics.

André, Jean-Michel; Jonnard, Philippe

2010-04-01

226

Hard X-Ray and Ultraviolet Emission during the 2011 June 7 Solar Flare  

NASA Astrophysics Data System (ADS)

The relationship between X-ray and UV emission during flares, particularly in the context of quasi-periodic pulsations, remains unclear. To address this, we study the impulsive X-ray and UV emission during an eruptive flare on 2011 June 7 utilizing X-ray imaging from RHESSI and UV 1700 Å imaging from SDO/AIA. This event is associated with quasi-periodic pulsations in X-ray and possibly UV emission, as well as substantial parallel and perpendicular motion in the hard X-ray footpoints. The motion of the footpoints parallel to the flare ribbons is unusual; it reverses direction on at least two occasions. However, there is no associated short timescale motion of the UV bright regions. Over the same time interval, the footpoints also gradually move apart at v ? 12 km s–1, consistent with the gradual outward expansion of the UV ribbons and the standard flare model. Additionally, we find that the locations of the brightest X-ray and UV regions are different, particularly during the early portion of the flare impulsive phase, despite their integrated emission being strongly correlated in time. Correlation analysis of measured flare properties, such as the footpoint separation, flare shear, photospheric magnetic field, and coronal reconnection rate, reveals that—in the impulsive phase—the 25-50 keV hard X-ray flux is only weakly correlated with these properties, in contrast with previous studies. We characterize this event in terms of long-term behavior, where the X-ray non-thermal, thermal, and UV emission sources appear temporally and spatially consistent, and short-term behavior, where the emission sources are inconsistent and quasi-periodic pulsations are a dominant feature requiring explanation. We suggest that the short timescale behavior of hard X-ray footpoints and the nature of the observed quasi-periodic pulsations are determined by fundamental, as yet unobserved properties of the reconnection region and particle acceleration sites. This presents a challenge for current three-dimensional flare reconnection models.

Inglis, A. R.; Gilbert, H. R.

2013-11-01

227

Characteristics of Diffuse X-Ray Line Emission within 20 Parsecs of the Galactic Center  

NASA Astrophysics Data System (ADS)

Over the last three years, the Galactic center region has been monitored with the Chandra X-Ray Observatory. Besides the X-ray emission from the target object, Sgr A*, diffuse X-ray emission was detected throughout most of the 17'×17' field of view. With 11 Chandra observations through 2002 June, the total effective exposure reaches ~590 ks, providing significant photon statistics on much of the detailed structure within the faint, often filamentary, diffuse X-ray emission. The true-color X-ray image and the equivalent-width images for the detected elemental species of the Galactic center region demonstrate that the diffuse X-ray features have a broad range of spatiospectral properties. Enhancements of the low ionization state Fe line emission (E~6.4 keV) to the northeast of Sgr A* can be interpreted as fluorescence within the dense interstellar medium resulting from irradiation by hard, external X-ray sources. They may also be explained by emission induced by the bombardments by high-energy particles on the ambient medium, such as may accompany unresolved supernova ejecta intruding into dense interstellar medium. The detection of molecular cloud counterparts to the 6.4 keV Fe line-emitting features indicates that these Fe line features are associated with dense Galactic center clouds and/or active star-forming regions, which strongly supports the proposed origins of the X-ray reflection and/or supernova ejecta for the Fe line emission. We detect highly ionized S and Si lines that are generally coincident with the low ionization state Fe line emission and the dense molecular clouds in the northeast of Sgr A*. These hot plasmas are then most likely produced by massive star-forming activities and/or supernova remnants in the Galactic center. In contrast, we find that highly ionized He-like Fe line emission (E~6.7 keV) is primarily distributed along the plane instead of being concentrated in the northeast of Sgr A*. The implied high temperature and the relatively uniform, but strong, alignment along the plane are consistent with the magnetic-confinement model, suggesting that this hot gas component has been reheated by the strong interstellar magnetic fields in the Galactic center to produce the observed He-like Fe line emission.

Park, Sangwook; Muno, Michael P.; Baganoff, Frederick K.; Maeda, Yoshitomo; Morris, Mark; Howard, Christian; Bautz, Mark W.; Garmire, Gordon P.

2004-03-01

228

Rebirth of X-Ray Emission from the Born-again Planetary Nebula A30  

NASA Astrophysics Data System (ADS)

The planetary nebula A30 is believed to have undergone a very late thermal pulse resulting in the ejection of knots of hydrogen-poor material. Using multi-epoch Hubble Space Telescope images, we have detected the angular expansion of these knots and derived an age of 850+280 - 150 yr. To investigate the spectral and spatial properties of the soft X-ray emission detected by ROSAT, we have obtained Chandra and XMM-Newton deep observations of A30. The X-ray emission from A30 can be separated into two components: a point source at the central star and diffuse emission associated with the hydrogen-poor knots and the cloverleaf structure inside the nebular shell. To help us assess the role of the current stellar wind in powering this X-ray emission, we have determined the stellar parameters and wind properties of the central star of A30 using a non-LTE model fit to its optical and UV spectra. The spatial distribution and spectral properties of the diffuse X-ray emission are highly suggestive that it is generated by the post-born-again and present fast stellar winds interacting with the hydrogen-poor ejecta of the born-again event. This emission can be attributed to shock-heated plasma, as the hydrogen-poor knots are ablated by the stellar winds, under which circumstances the efficient mass loading of the present fast stellar wind raises its density and damps its velocity to produce the observed diffuse soft X-rays. Charge transfer reactions between the ions of the stellar winds and material of the born-again ejecta have also been considered as a possible mechanism for the production of diffuse X-ray emission, and upper limits on the expected X-ray production by this mechanism have been derived. The origin of the X-ray emission from the central star of A30 is puzzling: shocks in the present fast stellar wind and photospheric emission can be ruled out, while the development of a new, compact hot bubble confining the fast stellar wind seems implausible.

Guerrero, M. A.; Ruiz, N.; Hamann, W.-R.; Chu, Y.-H.; Todt, H.; Schönberner, D.; Oskinova, L.; Gruendl, R. A.; Steffen, M.; Blair, W. P.; Toalá, J. A.

2012-08-01

229

REBIRTH OF X-RAY EMISSION FROM THE BORN-AGAIN PLANETARY NEBULA A30  

SciTech Connect

The planetary nebula A30 is believed to have undergone a very late thermal pulse resulting in the ejection of knots of hydrogen-poor material. Using multi-epoch Hubble Space Telescope images, we have detected the angular expansion of these knots and derived an age of 850{sup +280}{sub -150} yr. To investigate the spectral and spatial properties of the soft X-ray emission detected by ROSAT, we have obtained Chandra and XMM-Newton deep observations of A30. The X-ray emission from A30 can be separated into two components: a point source at the central star and diffuse emission associated with the hydrogen-poor knots and the cloverleaf structure inside the nebular shell. To help us assess the role of the current stellar wind in powering this X-ray emission, we have determined the stellar parameters and wind properties of the central star of A30 using a non-LTE model fit to its optical and UV spectra. The spatial distribution and spectral properties of the diffuse X-ray emission are highly suggestive that it is generated by the post-born-again and present fast stellar winds interacting with the hydrogen-poor ejecta of the born-again event. This emission can be attributed to shock-heated plasma, as the hydrogen-poor knots are ablated by the stellar winds, under which circumstances the efficient mass loading of the present fast stellar wind raises its density and damps its velocity to produce the observed diffuse soft X-rays. Charge transfer reactions between the ions of the stellar winds and material of the born-again ejecta have also been considered as a possible mechanism for the production of diffuse X-ray emission, and upper limits on the expected X-ray production by this mechanism have been derived. The origin of the X-ray emission from the central star of A30 is puzzling: shocks in the present fast stellar wind and photospheric emission can be ruled out, while the development of a new, compact hot bubble confining the fast stellar wind seems implausible.

Guerrero, M. A.; Ruiz, N.; Toala, J. A. [Instituto de Astrofisica de Andalucia, IAA-CSIC, c/Glorieta de la Astronomia s/n, 18008 Granada (Spain); Hamann, W.-R.; Todt, H.; Oskinova, L. [Institute for Physics and Astronomy, Universitaet Potsdam, 14476 Potsdam (Germany); Chu, Y.-H.; Gruendl, R. A. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Schoenberner, D.; Steffen, M. [Leibniz-Institut Fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam (Germany); Blair, W. P., E-mail: mar@iaa.es [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

2012-08-20

230

DISCOVERY OF EXTENDED X-RAY EMISSION AROUND THE HIGHLY MAGNETIC RRAT J1819-1458  

SciTech Connect

We report on the discovery of extended X-ray emission around the high magnetic field rotating radio transient J1819-1458. Using a 30 ks Chandra ACIS-S observation, we found significant evidence for extended X-ray emission with a peculiar shape: a compact region out to {approx}5.''5, and more diffuse emission extending out to {approx}13'' from the source. The most plausible interpretation is a nebula somehow powered by the pulsar, although the small number of counts prevents a conclusive answer on the nature of this emission. RRAT J1819-1458's spin-down energy loss rate (E-dot{sub rot}{approx}3 x 10{sup 32} erg s{sup -1}) is much lower than that of other pulsars with observed spin-down-powered pulsar wind nebulae (PWNe), and implies a rather high X-ray efficiency of eta{sub X}ident toL{sub pwn:0.5-8keV}/E-dot{sub rot}{approx}0.2 at converting spin-down power into the PWN X-ray emission. This suggests the need of an additional source of energy rather than the spin-down power alone, such as the high magnetic energy of this source. Furthermore, this Chandra observation allowed us to refine the positional accuracy of RRAT J1819-1458 to a radius of {approx}0.''3, and confirms the presence of X-ray pulsations and the {approx}1 keV absorption line, previously observed in the X-ray emission of this source.

Rea, N. [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Science Park 904, Postbus 94249, 1090 GE, Amsterdam (Netherlands); McLaughlin, M. A. [Department of Physics, West Virginia University, Morgantown, WV 26501 (United States); Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Slane, P. O. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Stella, L.; Israel, G. L. [INAF-Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone (Italy); Reynolds, S. P. [Department of Physics, North Carolina State University, P.O. Box 8202, Raleigh, NC 27695 (United States); Burgay, M.; Possenti, A. [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (Italy); Chatterjee, S., E-mail: n.rea@uva.n [Department of Astronomy and National Astronomy and Ionosphere Center, Cornell University, Ithaca, NY 14853-6801 (United States)

2009-09-20

231

The variable X-ray emission of PSR B0943+10  

NASA Astrophysics Data System (ADS)

The old pulsar PSR B0943+10 (P = 1.1 s, characteristic age ? = 5 Myr) is the best example of mode-switching radio pulsar. Its radio emission alternates between a highly organized state with regular drifting subpulses (B mode) and a chaotic emission pattern (Q mode). We present the results of XMM-Newton observations showing that the X-ray properties of PSR B0943+10 depend on its radio state. During the radio fainter state (Q mode), the X-ray flux is more than a factor of 2 larger than during the B mode and X-ray pulsations with ˜50 per cent pulsed fraction are detected. The X-ray emission of PSR B0943+10 in the B mode is well described by thermal emission with blackbody temperature kT = 0.26 keV coming from a small hotspot with luminosity of 7 × 1028 erg s-1, in good agreement with the prediction of the partially screened gap model, which also explains the properties of the radio emission in this mode. We derived an upper limit of 46 per cent on the X-ray pulsed fraction in the B mode, consistent with the geometry and viewing angle of PSR B0943+10 inferred from the radio data. The higher flux observed during the Q mode is consistent with the appearance of an additional component with a power-law spectrum with photon index 2.2. We interpret it as pulsed non-thermal X-rays produced in the star magnetosphere. A small change in the beaming pattern or in the efficiency of acceleration of the particles responsible for the non-thermal emission can explain the reduced flux of this component during the radio B mode.

Mereghetti, S.; Tiengo, A.; Esposito, P.; Turolla, R.

2013-11-01

232

X-Ray Emission and Absorption Features during an Energetic Thermonuclear X-Ray Burst from IGR J17062-6143  

NASA Astrophysics Data System (ADS)

Type-I X-ray bursts are thermonuclear explosions occurring in the surface layers of accreting neutron stars. These events are powerful probes of the physics of neutron stars and their surrounding accretion flow. We analyze a very energetic type-I X-ray burst from the neutron star low-mass X-ray binary IGR J17062-6143 that was detected with Swift on 2012 June 25. The light curve of the sime18 minute long X-ray burst tail shows an episode of sime10 minutes during which the intensity is strongly fluctuating by a factor of sime3 above and below the underlying decay trend on a timescale of seconds. The X-ray spectrum reveals a highly significant emission line around sime1 keV, which can be interpreted as an Fe-L shell line caused by the irradiation of cold gas. We also detect significant absorption lines and edges in the Fe-K band, which are strongly suggestive of the presence of hot, highly ionized gas along the line of sight. None of these features are present in the persistent X-ray spectrum of the source. The timescale of the strong intensity variations, the velocity width of the Fe-L emission line (assuming Keplerian motion), and photoionization modeling of the Fe-K absorption features each independently point to gas at a radius of ~= 103 km as the source of these features. The unusual X-ray light curve and spectral properties could have plausibly been caused by a disruption of the accretion disk due to the super-Eddington fluxes reached during the X-ray burst.

Degenaar, N.; Miller, J. M.; Wijnands, R.; Altamirano, D.; Fabian, A. C.

2013-04-01

233

New Chandra observations of the jet in 3C273. 1. Softer X-ray than radio spectra and the X-ray emission mechanism  

SciTech Connect

The jet in 3C273 is a high-power quasar jet with radio, optical and X-ray emission whose size and brightness allow a detailed study of the emission processes acting in it. We present deep Chandra observations of this jet and analyze the spectral properties of the jet emission from radio through X-rays. We find that the X-ray spectra are significantly softer than the radio spectra in all regions of the bright part of the jet except for the first bright ''knot A'', ruling out a model in which the X-ray emission from the entire jet arises from beamed inverse-Compton scattering of cosmic microwave background photons in a single-zone jet flow. Within two-zone jet models, we find that a synchrotron origin for the jet's X-rays requires fewer additional assumptions than an inverse-Compton model, especially if velocity shear leads to efficient particle acceleration in jet flows.

Jester, Sebastian; /Fermilab; Harris, D.E.; /Smithsonian Astrophys. Observ.; Marshall, H.L.; /MIT, MKI; Meisenheimer, K.; /Heidelberg, Max Planck Inst. Astron.

2006-05-01

234

X-RAY INSIGHTS INTO THE NATURE OF WEAK EMISSION-LINE QUASARS AT HIGH REDSHIFT  

SciTech Connect

We present Chandra observations of nine high-redshift quasars (z = 2.7-5.9) discovered by the Sloan Digital Sky Survey with weak or undetectable high-ionization emission lines in their UV spectra (WLQs). Adding archival X-ray observations of six additional sources of this class has enabled us to place the strongest constraints yet on the X-ray properties of this remarkable class of active galactic nuclei (AGNs). Although our data cannot rule out the possibility that the emission lines are overwhelmed by a relativistically boosted continuum, as manifested by BL Lac objects, we find that WLQs are considerably weaker in the X-ray and radio bands than the majority of BL Lacs found at much lower redshifts. If WLQs are high-redshift BL Lacs, then it is difficult to explain the lack of a large parent population of X-ray and radio bright weak-lined sources at high redshift. We also consider the possibility that WLQs are quasars with extreme properties, and in particular that the emission lines are suppressed by high accretion rates. Using joint spectral fitting of the X-ray spectra of 11 WLQs, we find that the mean photon index in the hard X-ray band is consistent with those observed in typical radio-quiet AGNs with no hint of an unusually steep hard-X-ray spectrum. This result poses a challenge to the hypothesis that WLQs have extremely high accretion rates, and we discuss additional observations required to test this idea.

Shemmer, Ohad; Brandt, W. N.; Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Anderson, Scott F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Diamond-Stanic, Aleksandar M.; Fan Xiaohui [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Richards, Gordon T. [Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Strauss, Michael A. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States)], E-mail: ohad@unt.edu

2009-05-01

235

X-ray emission from 30 J Blumlein operated compact diode  

NASA Astrophysics Data System (ADS)

An x-ray emitting diode of impedance 2.3 ? with a knife-edge cathode energized by a 90 kV, 30 J, solid dielectric Blumlein driver of pulse length 10 ns is studied. X-ray emission from titanium, copper, molybdenum, tin, tantalum, and lead anodes was investigated. The radiation yield from titanium and copper is low. Molybdenum and tin emit a significant part as K? line radiation, whereas the emission with tantalum and lead anode is essentially continuum radiation. The ratio of line to continuum with molybdenum target is estimated 17%+/-10%.

Zakaullah, M.; Worley, J.

2000-08-01

236

Very high energy gamma-ray emission from X-ray transients during major outbursts  

Microsoft Academic Search

Context: Some high mass X-ray binaries (HMXB) have been recently confirmed as\\u000agamma-ray sources by ground based Cherenkov telescopes. In this work, we\\u000adiscuss the gamma-ray emission from X-ray transient sources formed by a Be star\\u000aand a highly magnetized neutron star. This kind of systems can produce variable\\u000ahadronic gamma-ray emission through the mechanism proposed by Cheng and\\u000aRuderman,

M. Orellana; G. E. Romero; L. J. Pellizza; S. Vidrih

2007-01-01

237

Field-emission-type x-ray source using carbon-nanofibers  

SciTech Connect

An x-ray irradiation system of field-emission type has been constructed using carbon-nanofibers (CNFs) grown on a palladium wire that is 50 {mu}m in diameter. The electron current emitted from the CNFs was approximately 1 mA and was stable within 10% for a long time t>5000 h. The electrons passing through a slit in the gate electrode were accelerated to the desired energy, and were made to impinge on the metal target (Ti, Cu, Mo, and W) for generating x rays. The x-rays transmitted through Be-window were characterized using energy analyzers and a dosimeter. At an acceleration voltage of V{sub a}=50 kV, the energy spectra of the x-rays were exclusively composed of characteristic signals except for the Mo-target, and the dose rates of x-rays were D=2.5-14 Gy/min, depending on the target metals. This system also provides sharp x-ray images of both biological and nonbiological materials.

Kita, S.; Watanabe, Y.; Ogawa, A.; Ogura, K.; Sakai, Y.; Matsumoto, Y.; Isokane, Y.; Okuyama, F. [Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Nakazato, T.; Otsuka, T. [Department of Musculoskeletal Medicine, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601 (Japan)

2008-03-15

238

Femtosecond laser induced X-ray emission from metal alloys, polymers and color filters  

NASA Astrophysics Data System (ADS)

Various material surfaces were irradiated on a moving stage with focused laser pulses from a conventional 1 kHz femtosecond laser system, and X-ray emission spectra were measured during the laser ablation of the materials. Sharp K or L characteristic X-ray lines from the elements contained in the materials were clearly observed in a range of 2-15 keV. Signals due to copper and zinc were recognizable within a few minutes when a brass surface was irradiated. Poly(vinyl chloride) gave a marked emission originating from chlorine. When a color glass filter was irradiated, the detection of cobalt and arsenic was possible even though the amounts of these components were estimated to be less than 1 wt.% by using an electron probe microanalyzer. Time-integrated emission spectra in the visible region were also monitored during the femtosecond laser ablation of these materials. The emission spectra in the visible region were complicated owing to peaks originating from air components and white continuum emissions. Thus, the elemental analysis by femtoseond laser induced X-ray is considered to be useful for some samples. The etched trenches left at the surfaces after the laser ablation were examined with an optical microscope. The trench width varied with the materials, which may be attributed to changes in the irradiation area giving maximum counts of X-ray emission.

Hatanaka, Koji; Yomogihata, Ken-ichiro; Ono, Hiroshi; Fukumura, Hiroshi

2005-07-01

239

A search for diffuse X-ray emission from GeV-detected Galactic globular clusters  

NASA Astrophysics Data System (ADS)

Context. Recently, diffuse and extended sources in TeV ?-rays as well as in X-rays have been detected in the direction of the Galactic globular cluster (GC) Terzan 5. Remarkably, this is among the brightest GCs detected in the GeV regime. The nature of either the TeV or the diffuse X-ray signal from Terzan 5 is not yet settled. These emissions most likely indicate the presence of several non-thermal radiation processes in addition to those that give rise to the GeV signal. Aims: The aim of this work is to search for diffuse X-ray emission from all GeV-detected GCs where appropriate X-ray observations are available, and to compare the obtained results with the signal detected from Terzan 5. This study will help to determine whether Terzan 5 stands out among other GC or whether a whole population of globular clusters feature similar properties. Methods: After assessing all archival X-ray observations of GeV detected GCs, we analyzed the data of six Chandra observations pointed toward M 62, NGC 6388, NGC 6541, M 28, M 80, and NGC 6139. For each GC we characterized the diffuse X-ray emission using the same analysis techniques as for Terzan 5. To study the emission on the same relative scales we used the half-mass radius as a scale parameter to determine the extent of the potential emission region. Results: None of the six GCs show significant diffuse X-ray emission above the particle and diffuse Galactic X-ray background components. The derived upper limits allow to assess the validity of different models that were discussed in the interpretation of the multi-wavelength data of Terzan 5. A scenario based on synchrotron emission from relativistic leptons provided by the millisecond pulsar population cannot be securely rejected if a comparable magnetic field strength as in Terzan 5 is assumed for every GC. However, such a scenario seems to be unlikely for NGC 6388, and M 62. An inverse-Compton scenario relying on the presence of a putative GRB remnant with the same properties as proposed for Terzan 5 can be ruled out for all six GCs. Finally, the assumption that each GC hosts a source with the same luminosity as in Terzan 5 is ruled out for all GCs but NGC 6139.

Eger, P.; Domainko, W.

2012-04-01

240

X-ray emission of young solar type stars  

Microsoft Academic Search

T Tauri Stars (TTS) are young (<= 107 yrs) low mass (<= 2 Modot) stars. They have been originally characterized by strong emission lines (CTTS), and by IR excesses interpreted in terms of circumstellar disks. Ten years ago, the ``Einstein\\

Sophie Casanova

1994-01-01

241

Observing soft X-ray line emission from the interstellar medium with X-ray calorimeter on a sounding rocket  

Microsoft Academic Search

For an X-ray calorimeter working at 0.1 K, the energy resolution ideally can be as good as one eV for a practical detector. A detector with a resolution of 17 eV FWHM at 6 keV has been constructed. It is expected that this can be improved by a factor of two or more. With X-ray calorimeters flown on a sounding

J. Zhang; B. Edwards; M. Juda; D. McCammon; M. Skinner; R. Kelley; H. Moseley; R. Schoelkopf; A. Szymkowiak

1990-01-01

242

Constraints on Thermal X-Ray Radiation from SAX J1808.4-3658 and Implications for Neutron Star Neutrino Emission  

NASA Astrophysics Data System (ADS)

Thermal X-ray radiation from neutron star soft X-ray transients in quiescence provides the strongest constraints on the cooling rates of neutron stars and thus on the interior composition and properties of matter in the cores of neutron stars. We analyze new (2006) and archival (2001) XMM-Newton observations of the accreting millisecond pulsar SAX J1808.4-3658 in quiescence, which provide the most stringent constraints to date. The X-ray spectrum of SAX J1808.4-3658 in the 2006 observation is consistent with a power law of photon index 1.83+/-0.17, without requiring the presence of a blackbody-like component from a neutron star atmosphere. Our 2006 observation shows a slightly lower 0.5-10 keV X-ray luminosity, at a level of 68+15-13% of that inferred from the 2001 observation. Simultaneous fitting of all available XMM-Newton data allows a constraint on the quiescent neutron star (0.01-10 keV) luminosity of LNS<1.1×1031 ergs s-1. This limit excludes some current models of neutrino emission mediated by pion condensates and provides further evidence of additional cooling processes, such as neutrino emission via direct Urca processes involving nucleons and/or hyperons, in the cores of massive neutron stars. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Heinke, C. O.; Jonker, P. G.; Wijnands, R.; Taam, R. E.

2007-05-01

243

Obtaining attosecond X-ray pulses using a self-amplifiedspontaneous emission free electron laser  

SciTech Connect

We describe a technique for the generation of a solitary attosecond X-ray pulse in a free electron laser (FEL), via a process of self-amplified spontaneous emission. In this method, electrons experience an energy modulation upon interacting with laser pulses having a duration of a few cycles within single-period wiggler magnets. Two consecutive modulation sections, followed by compression in a dispersive section, are used to obtain a single, sub-femtosecond spike in the electron peak current. This region of the electron beam experiences an enhanced growth rate for FEL amplification. After propagation through a long undulator,this current spike emits a {approx}250 attosecond X-ray pulse whose intensity dominates the X-ray emission from the rest of the electron bunch.

Zholents, A.A.; Penn, G.

2005-01-07

244

Weak Hard X-Ray Emission from Two Broad Absorption Line Quasars Observed with NuSTAR: Compton-thick Absorption or Intrinsic X-Ray Weakness?  

NASA Astrophysics Data System (ADS)

We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain ?400-600 hard X-ray (gsim 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed (N H <~ 1024 cm-2). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N H ? 7 × 1024 cm-2 if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe K? line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%.

Luo, B.; Brandt, W. N.; Alexander, D. M.; Harrison, F. A.; Stern, D.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W.; Fabian, A. C.; Farrah, D.; Fiore, F.; Fuerst, F.; Grefenstette, B. W.; Hailey, C. J.; Hickox, R.; Madsen, K. K.; Matt, G.; Ogle, P.; Risaliti, G.; Saez, C.; Teng, S. H.; Walton, D. J.; Zhang, W. W.

2013-08-01

245

CHANDRA DETECTION OF EXTENDED X-RAY EMISSION FROM THE RECURRENT NOVA RS OPHIUCHI  

SciTech Connect

Radio, infrared, and optical observations of the 2006 eruption of the symbiotic recurrent nova RS Ophiuchi showed that the explosion produced non-spherical ejecta. Some of this ejected material was in the form of bipolar jets to the east and west of the central source. Here we describe X-ray observations taken with the Chandra X-ray Observatory one and a half years after the beginning of the outburst that reveal narrow, extended structure with a position angle of approximately 300 deg. (east of north). Although the orientation of the extended feature in the X-ray image is consistent with the readout direction of the CCD detector, extensive testing suggests that the feature is not an artifact. Assuming it is not an instrumental effect, the extended X-ray structure shows hot plasma stretching more than 1900 AU from the central binary (taking a distance of 1.6 kpc). The X-ray emission is elongated in the northwest direction-in line with the extended infrared emission and some minor features in the published radio image. It is less consistent with the orientation of the radio jets and the main bipolar optical structure. Most of the photons in the extended X-ray structure have energies of less than 0.8 keV. If the extended X-ray feature was produced when the nova explosion occurred, then its 1.''2 length as of 2007 August implies that it expanded at an average rate of more than 2 mas day{sup -1}, which corresponds to a flow speed of greater than 6000 km s{sup -1} (days/1.6 kpc) in the plane of the sky. This expansion rate is similar to the earliest measured expansion rates for the radio jets.

Luna, G. J. M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St. MS 15, Cambridge, MA 02138 (United States); Montez, R.; Kastner, J. H. [2100 Carlson Center for Imaging Science Rochester Institute of Technology Rochester, NY 14623 (United States); Sokoloski, J. L. [Columbia Astrophysics Laboratory, 550 W. 220th Street, 1027 Pupin Hall, Columbia University, New York, NY 10027 (United States); Mukai, K., E-mail: gluna@cfa.harvard.ed [CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771 (United States)

2009-12-20

246

X-RAY EMISSION FROM NITROGEN-TYPE WOLF-RAYET STARS  

SciTech Connect

We summarize new X-ray detections of four nitrogen-type Wolf-Rayet (WR) stars obtained in a limited survey aimed at establishing the X-ray properties of WN stars across their full range of spectral subtypes. None of the detected stars is so far known to be a close binary. We report Chandra detections of WR 2 (WN2), WR 18 (WN4), and WR 134 (WN6), and an XMM-Newton detection of WR79a (WN9ha). These observations clearly demonstrate that both WNE and WNL stars are X-ray sources. We also discuss Chandra archive detections of the WN6h stars WR 20b, WR 24, and WR 136 and ROSAT non-detections of WR 16 (WN8h) and WR 78 (WN7h). The X-ray spectra of all WN detections show prominent emission lines and an admixture of cool (kT < 1 keV) and hot (kT > 2 keV) plasma. The hotter plasma is not predicted by radiative wind shock models and other as yet unidentified mechanisms are at work. Most stars show X-ray absorption in excess of that expected from visual extinction (A {sub V}), likely due to their strong winds or cold circumstellar gas. Existing data suggest a falloff in X-ray luminosity toward later WN7-9 subtypes, which have higher L {sub bol} but slower, denser winds than WN2-6 stars. This provides a clue that wind properties may be a more crucial factor in determining emergent X-ray emission levels than bolometric luminosity.

Skinner, Stephen L.; Sokal, Kimberly R. [Center for Astrophysics and Space Astronomy (CASA), University of Colorado, Boulder, CO 80309-0389 (United States); Zhekov, Svetozar A. [JILA, University of Colorado, Boulder, CO 80309-0440 (United States); Guedel, Manuel [Institute of Astronomy, ETH Zuerich, Wolfgang-Pauli-Str. 27, 8093 Zuerich (Switzerland); Schmutz, Werner [Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center (PMOD/WRC), Dorfstrasse 33, CH-7260 Davos Dorf (Switzerland)], E-mail: Stephen.Skinner@colorado.edu

2010-03-15

247

Intragroup and Galaxy-Linked Diffuse X-ray Emission in Compact Groups of Galaxies  

NASA Astrophysics Data System (ADS)

Isolated compact groups of galaxies present a range of dynamical states, group velocity dispersions, and galaxy morphologies with which to study galaxy evolution, particularly the properties of gas both within the galaxies and in the intragroup medium. As part of a large, multi-wavelength examination of compact groups, we present an archival study of diffuse X-ray emission in a sample of compact groups of galaxies observed with the Chandra X-ray Observatory. We find that several of the groups in our sample exhibit detectable diffuse emission. However, unlike large-scale emission in galaxy clusters, the diffuse features in the majority of the detected groups are linked to the individual galaxies, in the form of both plumes and halos likely as a result of star formation or AGN activity, as well as in emission from tidal features. Several groups appear to be consistent with the cluster scaling relations between X-ray luminosity, plasma temperature, and velocity dispersion due to vigorous star formation within the galaxies, however the majority of groups fall systematically below these relationships. We find that X-ray luminosity increases with decreasing group HI to dynamical-mass ratio with tentative evidence for a dependence in X-ray luminosity on HI morphology whereby systems with intragroup HI indicative of strong interactions are considerably more X-ray luminous than passively evolving groups. Finally, our findings suggest that the hot gas in these groups is not in hydrostatic equilibrium and these systems are not low-mass analogs of rich groups or clusters.

Desjardins, Tyler D.; Gallagher, S.; Tzanavaris, P.; Mulchaey, J. S.; Brandt, W. N.; Charlton, J. C.; Garmire, G.; Gronwall, C.; Hornschemeier, A. E.; Johnson, K. E.; Konstantopoulos, I.; Zabludoff, A. I.

2013-04-01

248

Determination of the texture of arrays of aligned carbon nanotubes from the angular dependence of the X-ray emission and X-ray absorption spectra  

SciTech Connect

The properties of materials containing carbon nanotubes depend on the degree of alignment and the internal structure of nanotubes. It is shown that the degree of misorientation of carbon nanotubes in samples can be evaluated from the measurements of the angular dependences of the carbon X-ray emission and carbon X-ray absorption spectra. The CK{sub {alpha}} emission and CK X-ray absorption spectra of the array of multiwalled carbon nanotubes synthesized by catalytic thermolysis of a mixture of fullerene and ferrocene are measured. A comparison of the calculated model dependences of the relative intensities of the {pi} and {sigma} bands in the spectra with the experimental results makes it possible to evaluate the degree of misorientation of nanotubes in the sample and their internal texture.

Okotrub, A. V., E-mail: spectrum@che.nsk.su; Belavin, V. V.; Bulusheva, L. G.; Gusel'nikov, A. V.; Kudashov, A. G. [Russian Academy of Sciences, Nikolaev Institute of Inorganic Chemistry, Siberian Branch (Russian Federation); Vyalikh, D. V.; Molodtsov, S. L. [Dresden University of Technology, Institute of Solid State Physics (Germany)

2008-09-15

249

Experiment investigation of La(1-x)SrxMnO3 by high-resolution X-ray emission and spin-polarized X-ray absorption spectroscopy.  

PubMed

Big changes in resistivity along with the changing of local structure in some oxide systems, such as high-temperature superconductors and colossal magnetoresistance system, strongly suggest the need of a systematic investigation of their local electronic and atomic structures. In this work we present the high-resolution X-ray emission spectra and the spin-polarized X-ray absorption near-edge spectroscopy (SPXANES) data at the Mn K-edge in the La(1-x)Sr(x)MnO(3). This experiment is based on a high-resolution large-acceptance crystal analyzer based on Si (111) and optimized for X-ray fluorescence spectroscopy. With a spherical bent crystal monochromator, a Mn Kbeta emission spectra with high resolution was obtained with a short collection time and SPXANES spectra of La(1-x)Sr(x)MnO(3) at room temperature were also measured at high temperature. PMID:18319193

Hua, Wei; Zhou, Kejin; Huang, Yuying; Qian, Q; He, Wei; Ma, Sixuan; Chu, Wangsheng; Hu, Tiandou; Wu, Ziyu

2008-01-17

250

On the X-ray emission from massive star clusters and their evolving superbubbles - II. Detailed analytics and observational effects  

Microsoft Academic Search

In this work, we present a comprehensive X-ray picture of the interaction between a super star cluster and the interstellar medium. In order to do that, we compare and combine the X-ray emission from the superwind driven by the cluster with the emission from the wind-blown bubble. Detailed analytical models for the hydrodynamics and X-ray luminosity of fast polytropic superwinds

G. A. Añorve-Zeferino; G. Tenorio-Tagle; S. Silich

2009-01-01

251

The Relationship of Hard X-Ray and Optical Line Emission in Low-Redshift Active Galactic Nuclei  

Microsoft Academic Search

In this paper we assess the relationship of the population of active galactic nuclei (AGNs) selected by hard X-rays to the traditional population of AGNs with strong optical emission lines. First, we study the emission-line properties of a new hard-X-ray-selected sample of 47 local AGNs (classified optically as Type 1 and 2 AGNs). We find that the hard X-ray (3-20

T. M. Heckman; A. Ptak; A. Hornschemeier; G. Kauffmann

2005-01-01

252

Hard X-ray Emission From A Flare-related Jet  

NASA Astrophysics Data System (ADS)

Solar X-ray jets were first observed by Yohkoh (Shibata 1992, Strong 1992). During these events, collimated flows of plasma are accelerated in the corona. Previous observations have detected jet-related electrons directly in space as well as via radio signatures (type III bursts). However the major diagnostic of fast electrons is bremsstrahlung X-ray emission, but until now we have never seen any evidence of hard X-ray emission directly from the jet in the corona. This could be because it is rare to find a coronal jet dense enough to provide a bremsstrahlung target for the electrons, or hot enough to generate high energy thermal emission. We report what we believe to be the first observation of hard X-ray emission formed in a coronal jet. The event occurred on the 22nd of August 2002 and its evolution was observed by a number of instruments. In particular we study the pre-impulsive and impulsive phase of the flare using data from RHESSI, TRACE and the Nobeyama Radioheliograph. During this period RHESSI observed significant hard X-ray emission to energies as high as 50 keV in the jet. Radio observations from the Nobeyama Radioheliograph show a positive spectral index for the ejected material, which may be explained by optically-thick gyrosynchrotron emission from non-thermal electrons in the jet. HMB gratefully acknowledges the support of an SPD and STFC studentship. LF gratefully acknowledges the support of an STFC Rolling Grant, and financial support by the European Commission through the SOLAIRE Network (MTRN-CT_2006-035484)

Bain, Hazel; Fletcher, L.

2009-05-01

253

X-ray emission from RS CVn systems - A progress report  

Microsoft Academic Search

A report is given on progress made in a search for soft X-ray emission from RS CVn systems, using the low-energy detectors aboard HEAO 1. To date, nine systems have been seen. The properties of these systems are discussed. The failure to detect certain systems is considered. The possibility is discussed of discovering hitherto unknown RS CVn systems with soft

F. Walter; P. Charles; S. Bowyer

1978-01-01

254

X-Ray Emission from the Metastable Components of Slow Ar16+ Beam on Metallic Surfaces  

NASA Astrophysics Data System (ADS)

K-shell X-ray emission was observed in the neutralization process of Ar16+ interacting with beryllium and molybdenum at slow speed (less than Bohr velocity). The K-shell X-ray emission came from the metastable component of Ar16+ beam with the configuration (1s2s) produced from electron cyclotron resonance ion source. The intensity ratio of K? X-ray emission to K? X-ray emission (IK?/IK?) in the neutralization process decreased when the kinetic energy of the projectile increased. This is closely related to the flight time the projectiles spend above the surface, which is dominated by both the work function of the metal and the normal velocity component of the incident ions to the surface according to the classical over-barrier model. As the relation between IK?/IK? and the above-flight time shows, the longer time above the surface the larger ratio due to the above-surface contribution. Furthermore, the smaller work function leads to the smaller contribution from the above surface.

Zhang, H. Q.; Chen, X. M.; Liu, Z. Y.; Yang, Z. H.; Xu, J. Z.; Cui, Y.; Xu, X.; Shao, J. X.; Zhang, X. A.; Zhao, Y. T.; Zhang, Y. P.; Xiao, G. Q.

255

THE MULTIELEMENTAL ANALYSIS OF DRINKING WATER USING PROTON-INDUCED X-RAY EMISSION (PIXE)  

EPA Science Inventory

A new, rapid, and economical method for the multielemental analysis of drinking water samples is described. The concentrations of 76 elements heavier than aluminum are determined using proton-induced x-ray emission (PIXE) technology. The concentration of sodium is evaluated using...

256

Chemical bonding on surfaces probed by X-ray emission spectroscopy and density functional theory  

Microsoft Academic Search

X-ray emission spectroscopy applied to surface adsorbates is an experimental technique that provides an atom-specific projection of the electronic structure. In combination with theoretical density functional spectrum simulations, it becomes an extremely powerful tool to analyze in detail the surface chemical bond. The present review discusses both the experimental and computational techniques related to the spectroscopy and summarizes all applications

Anders Nilsson; Lars Gunnar Moody Pettersson

2004-01-01

257

Probing chemical bonding in adsorbates using X-ray emission spectroscopy  

Microsoft Academic Search

When a molecule is adsorbed on a metal surface by chemical bonding new electronic states are formed. The direct observation and identification of these states has been an experimental challenge. Their signature is often obscured by bulk substrate states. In the following contribution we will show how X-ray emission spectroscopy (XES), in spite of its inherent bulk sensitivity, can be

A. Nilsson; J. Hasselström; A. Föhlisch; O. Karis; L. G. M. Pettersson; M. Nyberg; L. Triguero

2000-01-01

258

X-ray emission of multiple T Tauri stars in Taurus  

NASA Astrophysics Data System (ADS)

We present a study of X-ray emission of known multiple T Tauri stars (TTS) in Taurus based on ROSAT observations. We used the ROSAT All-Sky Survey (RASS) detection rates of single classical (cTTS) and weak-line TTS (wTTS) to investigate statistically the TTS nature (classical or weak-line) of the components in multiple TTS, which are too close for spatially resolved spectroscopy so far. Because single wTTS show a higher RASS detection rate than single cTTS, the different binary TTS (cTTS-cTTS, cTTS-wTTS, wTTS-wTTS) should also have different detection rates. We find that the observed RASS detection rates of binary wTTS, where the nature of the secondary is unknown, are in agreement with the secondaries being wTTS rather than cTTS, and mixed pairs are very rare. Furthermore we analyse the X-ray emission of TTS systems resolvable by the ROSAT HRI. Among those systems we find statistical evidence that primaries show larger X-ray luminosity than secondaries, and that the samples of primary and secondary TTS are similar concerning the X-ray over bolometric luminosity ratios. Furthermore, primaries always emit harder X-rays than secondaries. In all cases where rotational velocities and/or periods are known for both companions, it is always the primary that rotates faster. Hence, the stronger X-ray emission of the primaries may be due to higher bolometric luminosity and/or faster rotation.

König, B.; Neuhäuser, R.; Stelzer, B.

2001-04-01

259

EFFECT OF METALLICITY ON X-RAY EMISSION FROM THE WARM-HOT INTERGALACTIC MEDIUM  

SciTech Connect

Hydrodynamic simulations predict that a significant fraction of the gas in the current universe is in the form of high temperature, highly ionized plasma emitting and absorbing primarily in the soft X-ray and UV bands, dubbed the warm-hot intergalactic medium (WHIM). Its signature should be observable in redshifted emission and absorption lines from highly ionized elements. To determine the expected WHIM emission in the soft X-ray band we used the output of a large scale smoothed particle hydrodynamic simulation to generate images and spectra with angular resolution of 14'' and energy resolution of 1 eV. The current biggest limit of any hydrodynamic simulation in predicting the X-ray emission comes from metal diffusion. In our investigation, by using four different models for the WHIM metallicity we have found a strong dependence of the emission on the model used, with differences up to almost an order of magnitude. For each model, we have investigated the redshift distribution and angular scale of the emission, confirming that most photons come from redshift z < 1.2 and that the emission has a typical angular scale of less than a few arcminutes. We also compared our simulations with the few currently available observations and found that, within the variation of the metallicity models, our predictions are in good agreement with current constraints on the WHIM emission, and at this time the weak experimental constraints on the WHIM emission are not sufficient to exclude any of the models used.

Ursino, E.; Galeazzi, M. [Physics Department, University of Miami, Coral Gables, FL 33155 (United States); Roncarelli, M., E-mail: galeazzi@physics.miami.ed [Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, I-40127 Bologna (Italy)

2010-09-20

260

Soft X-ray emission from the radio pulsar PSR 0656 + 14  

SciTech Connect

A radio source with a flux density of a few mJy was found in the error region of the soft X-ray source E0656 + 14, and identified as the radio pulsar PSR 0656 + 14. The radio source has a steep, nonthermal spectrum and a high degree of linear (62%) and circular (19%) polarization. The X-ray spectrum of the pulsar is among the softest sources observed with the Einstein Observatory. The X-ray data taken with the Einstein imaging proportional counter (IPC) permit a range of blackbody temperatures of 3-6 x 10 to the 5th K, and an equivalent column density of hydrogen smaller than 4 x 10 to the 20th/sq cm. If the assumption is made that the X-ray flux is thermal radiation from surface of the neutron star, then the pulsar must be at a distance smaller than 550 pc, consistent with the low dispersion measure of PSR 0656 + 14. The X-ray timing data suggest that the X-ray emission is modulated at the pulsar's 0.385-s spin period with an amplitude of 18% + or - 6%, and that there is a 0.0002 probability that this is spurious. It was noted that PSR 0656 + 14 is close to the geometric center of a 20-deg diameter soft X-ray emitting ring called the Gemini-Monoceros enhancement. The close distance of the pulsar, together with its relatively young age of 1.1 x 10 to the 5th yr, makes it possible that the ring is a supernova remnant from the explosion of the pulsar's progenitor. A radio source extending over a region 1.2 to 3.3 arcmin south of the pulsar is a candidate for association with the pulsar. 46 refs.

Cordova, F.A.; Middleditch, J.; Hjellming, R.M.; Mason, K.O. (Los Alamos National Lab., NM (USA) National Radio Astronomy Observatory, Socorro, NM (USA) London Univ. College, Dorking (England))

1989-10-01

261

Pressure-dependent electronic structures and orbital hybridization of Mn 3d states in multiferroic BiMnO3 : A combined x-ray absorption, x-ray emission, and resonant x-ray emission study  

NASA Astrophysics Data System (ADS)

We investigated both the dependence of electronic structures and spin states on pressure up to 25 GPa and the hybridization of Mn 3d states in BiMnO3 by combining measurements of x-ray absorption, x-ray emission, and 1s3p-resonant x-ray emission spectroscopy (RXES). The Mn K-edge x-ray absorption spectra of BiMnO3 show a great change for pressure ˜1 GPa, corresponding to the occurrence of a structural transition. The gradually diminished shoulder of the white line and subsequently increased intensity of the white line of Mn K-edge spectra on increasing the external pressure from 2 to ˜15 GPa are attributed to a diminished Jahn-Teller distortion of MnO6 octahedra in BiMnO3 with increasing pressure. For pressure >˜15 GPa, the intensity of the white line in Mn K-edge spectra of BiMnO3 became progressively decreased. Preedge peaks in Mn K-edge spectra of BiMnO3 at P = 25 GPa shifted to smaller energy ˜0.3 eV relative to P = 0.7 GPa. The spin magnetic moments deduced from the K? emission line show a significant decrease for pressures between 0 and 2 GPa, then a monotonic decrease for pressures between 2 and 7 GPa, and a slight decrease after 7 GPa. The 1s3p-RXES spectra obtained at the Mn-K preedge for BiMnO3 reveal that the empty Mn 3d(eg0) states exhibit a delocalized character, suggested to originate from the hybridization of the unoccupied Mn 3d states with the Mn 4p orbitals. These findings provide insight into the evolution of electronic structures related to the structural transformation of multiferroic BiMnO3 under pressure.

Chen, J. M.; Haw, S. C.; Lee, J. M.; Chen, S. A.; Lu, K. T.; Chen, S. W.; Deng, M. J.; Liao, Y.-F.; Lin, J. M.; Chen, B. H.; Chou, F. C.; Hiraoka, N.; Ishii, H.; Tsuei, K. D.; Huang, Eugene

2012-07-01

262

X-ray Emission from Plasma Focus: Envisioned by Various Competitive Detectors  

Microsoft Academic Search

A study of X-ray emission from a Mather-type plasma focus device by\\u000a simultaneously employing various X-ray detectors like silicon pin diode,\\u000a photoconducting detectors (PCDs)-CVD-diamond and gallium arsenide\\u000a (GaAs), plastic scintillator coupled with photomultiplier tube with and\\u000a with out optical fiber is presented. The pin diode and PCDs are masked\\u000a with 10 mu m thick cobalt filter. The device is energized

S. Hussain; S. Ahmad; Mehboob Sadiq; P. Lee; M. Zakaullah; A. Waheed

2009-01-01

263

Linac-based, intense, coherent x-ray source using self-amplified spontaneous emission  

SciTech Connect

In this article, the author discusses the principles of self-amplified spontaneous emission (SASE), how the SASE could be the basis of next generation light sources exceeding the current performance -- by many orders of magnitude in spectral brightness, and by a factor of a hundred in time resolution. He also discusses how the SLAC linac, due to its high energy and its precision control, is ideally suited for the x-ray SASE. Therefore, using the SLAC linac for generation of x-ray SASE for the frontier of the photon sciences will ensure that the SLAC linac remain scientifically vigorous for a long time.

Kim, K.J.

1997-09-01

264

Observations of X-rays and Thermal Dust Emission from the Supernova Remnant Kes 75  

Microsoft Academic Search

We present Spitzer Space Telescope and Chandra X-ray Observatory observations\\u000aof the composite Galactic supernova remnant Kes 75 (G29.7-0.3). We use the\\u000adetected flux at 24 microns and hot gas parameters from fitting spectra from\\u000anew, deep X-ray observations to constrain models of dust emission, obtaining a\\u000adust-to-gas mass ratio M_dust\\/M_gas ~0.001. We find that a two-component\\u000athermal model, nominally

Timothy D. Morton; Patrick Slane; Kazimierz J. Borkowski; Stephen P. Reynolds; David J. Helfand; B. M. Gaensler; John P. Hughes

2007-01-01

265

X-ray diode using a silicon field-emission photocathode  

NASA Astrophysics Data System (ADS)

We have produced arrays of 10,000 sharp p-type silicon points using an etch plus oxidation method. These points were used as electron emitters. No high vacuum caseation or high temperature cleaning was needed to observe the electron emission. These are seen to be photosensitive sources of electrons at 200 K and 300 K. They were also used to produce AlK(alpha ) x rays. This constitutes the first use of etched, point arrays for generating electrons for x-ray sources.

Karain, Wael I.; Knight, Larry V.; Reyes-Mena, Arturo; Allred, David D.

1993-01-01

266

Optical emission from cooling flows in distant X ray clusters of galaxies  

NASA Astrophysics Data System (ADS)

Although the Einstein satellite detected cooling flows in the x ray emission from clusters of galaxies 10 years ago, the understanding of these flows remains incomplete. The x ray emitting gas in the centers of these clusters is so dense that its cooling time is shorter than a Hubble time. Thus gas may cool and flow into the center of the cluster. This cooling gas is thermally unstable and should quickly become inhomogeneous. Optical filamentation (1-100 kpc scales) often appears near the centers of nearby clusters containing cooling flows, usually within the central galaxies accreting the gas. Indeed, only clusters with well-developed cooling flows seem to possess highly luminous, emission-line nebulae. Researchers present here some results of preliminary observational and theoretical studies of this class of emission-line objects. Researchers observed a complete, x ray selected sample of 25 distant clusters of galaxies extracted from the Einstein Extended Medium Sensitivity Survey. They discovered luminous extended H alpha emission in 10 of these clusters. Thus at least 40 percent of the clusters in the sample contain cool gas. If we crudely compare the sample to that of Arnaud (1988), in which approx. 40 percent of his 104 x ray clusters have cooling flows, the result implies that cooling flows may actually be a more common phenomenon in the past than in the present. The connection between the cooling flow and the H alpha emission is a mystery. The straightforward calculation of 1 (photoionization) to 3 (shocks) recombinations per H atom in the cooling flow gives mass infall rates 3 to 100 times greater than M derived from x ray observations. Researchers have made some preliminary theoretical calculations in an attempt to resolve this problem.

Donahue, Megan; Stocke, John T.; Voit, G. Mark; Gioia, Isabella

1990-07-01

267

Soft X-ray synchrotron radiation investigations of actinidematerials systems utilizing X-ray emission spectroscopy and resonantinelastic X-ray scattering  

Microsoft Academic Search

Synchrotron radiation (SR) methods have been utilized with increasing frequency over the past several years to study topics in actinide science, ranging from those of a fundamental nature to those that address a specifically-targeted technical need. In particular, the emergence of microspectroscopic and fluorescence-based techniques have permitted investigations of actinide materials at sources of soft x-ray SR. Spectroscopic techniques with

D. K. Shuh; S. M. Butorin; J.-H. Guo; J. Nordgren

2004-01-01

268

X-ray Emission of Seyfert 2 Galaxies: Contribution of Star-Forming Processes  

NASA Astrophysics Data System (ADS)

We propose to study the SB-AGN connection in a representative sample of Seyfert 2 galaxies in which the stellar population have been analysed using state-of-the-art population synthesis models in the optical-UV. By extending the results of the optical modeling to X-rays, we can infer the amount of energy in the X band produced by the SB and compare it with the energy from the central engine. Interestingly, this will allow us to elucidate the nature of the soft X-ray emission in Seyfert 2s, which is still largely unknown. The lack of well studied samples of Seyfert 2s which explore the complementary information provided by optical-UV and X-ray observations in a consistent and well defined manner justifies further analysis using high quality data such as those proposed here.

Jimenez-Bailon, Elena

2005-10-01

269

X-ray And Far-ultraviolet Line Emission Of The Intermediate Polar Ex Hya  

NASA Astrophysics Data System (ADS)

This paper presents simultaneous X-ray and far ultraviolet (FUV) observations of the Intermediate Polar EX Hya. The exposure times were 59.9 and 27.5 ks, respectively. The phase-resolved spectra show orbital variations in the X-ray and FUV emission lines of C, N, O, Mg, Si, and Fe. In X-rays, the O VIII, Mg XII, and Si XIV fluences have a maximum at phase 0.3, while the triplet G ratios of O, Mg, and Si remain relatively constant. The Fe XVII 15.26/15.01 ratio shows a drop at phase 0.7. This phase coincides with the UV dip at orbital phase 0.8. The dip is likely caused by a large increase in the optical depth where the accretion stream impacts the disk. The ISM column densities of atomic and molecular H are 5E-16 and 1E-13 cm-2, respectively.

Barrett, Paul Everett; Schlegel, E. M.; Rana, V. R.; Rann, J. D.; Singh, K. P.

2008-03-01

270

The behavior of X-ray emission lines from an accretion disk in flare model  

NASA Astrophysics Data System (ADS)

We investigate the model of an accretion disk illuminated locally by hard X-rays. The X-ray source is in the form of the hot flares most probably produced via magnetic field reconnection. Flares are accompanied by hot spots created at the accretion disk surface by illumination. We compute the local reflected (spot) spectrum using the codes TITAN/NOAR. In our computations we are able to model the change of intensities of X-ray emission lines from 0.1 keV up to the most prominent iron K? line due to appearance of flares. The global spectrum is obtained assuming a distribution of flares, where each flare has assumed effective life time. In such a case we follow the line profile modified due to relativistic smearing in Kerr metric.

Ró?a?ska, A.; Czerny, B.; Karas, V.; Dumont, A.-M.; Collin, S.

2004-07-01

271

X-ray emission from galaxies - The distribution of low-luminosity X-ray sources in the Galactic Centre region  

NASA Astrophysics Data System (ADS)

We report a study of the extended X-ray emission observed in the Galactic Centre (GC) region based on archival XMM-Newton data. The GC diffuse emission can be decomposed into three distinct components: the emission from low-luminosity point sources; the fluorescence of (and reflection from) dense molecular material; and soft (kT ~1 keV), diffuse thermal plasma emission most likely energised by supernova explosions. Here, we examine the emission due to unresolved point sources. We show that this source component accounts for the bulk of the 6.7-keV and 6.9-keV line emission. We fit the surface brightness distribution evident in these lines with an empirical 2-d model, which we then compare with a prediction derived from a 3-d mass model for the old stellar population in the GC region. We find that the X-ray surface brightness declines more rapidly with angular offset from Sgr A* than the mass-model prediction. One interpretation is that the X-ray luminosity per solar mass characterising the GC source population is increasing towards the GC. Alternatively, some refinement of the mass-distribution within the nuclear stellar disc may be required. The unresolved X-ray source population is most likely dominated by magnetic CVs. We use the X-ray observations to set constraints on the number density of such sources in the GC region. Our analysis does not support the premise that the GC is pervaded by very hot (~ 7.5 keV) thermal plasma, which is truly diffuse in nature.

Heard, Victoria; Warwick, Robert

2012-09-01

272

X-ray emission processes in stars and their immediate environment  

NASA Astrophysics Data System (ADS)

A decade of X-ray stellar observations with Chandra and XMM-Newton has led to significant advances in our understanding of the physical processes at work in hot (magnetized) plasmas in stars and their immediate environment, providing new perspectives and challenges, and in turn the need for improved models. The wealth of high-quality stellar spectra has allowed us to investigate, in detail, the characteristics of the X-ray emission across the Hertzsprung-Russell (HR) diagram. Progress has been made in addressing issues ranging from classical stellar activity in stars with solar-like dynamos (such as flares, activity cycles, spatial and thermal structuring of the X-ray emitting plasma, and evolution of X-ray activity with age), to X-ray generating processes (e.g., accretion, jets, magnetically confined winds) that were poorly understood in the preChandra/XMM-Newton era. I will discuss the progress made in the study of high energy stellar physics and its impact in a wider astrophysical context, focusing on the role of spectral diagnostics now accessible.

Testa, Paola

2010-04-01

273

X-ray emission processes in stars and their immediate environment  

NASA Astrophysics Data System (ADS)

A decade of X-ray stellar observations with Chandra and XMM-Newton has led to significant advances in our understanding of the physical processes at work in hot (magnetized) plasmas in stars and their immediate environment, providing new perspectives and challenges, and in turn the need for improved models. The wealth of high-quality stellar spectra has allowed us to investigate, in detail, the characteristics of the X-ray emission across the HR diagram. Progress has been made in addressing issues ranging from classical stellar activity in stars with solar-like dynamos (such as, flares, activity cycles, spatial and thermal structuring of the X-ray emitting plasma, evolution of X-ray activity with age,...), to X-ray generating processes (e.g. accretion, jets, magnetically confined winds,..) that were poorly understood in the pre-Chandra/XMM-Newton era. I will discuss the progress made in the study of high energy stellar physics and its impact in a wider astrophysics context, focusing on the role of spectral diagnostics now accessible.

Testa, Paola

2009-09-01

274

Hard X-ray emission from Starburst Galaxies with the NuSTAR Mission  

NASA Astrophysics Data System (ADS)

Launched in mid-2012, NuSTAR is the first focusing hard X-ray (E10 keV) astronomical observatory. Hard X-ray emission from star-forming galaxies arises from a population of neutron stars and stellar-mass black holes, however few starburst galaxies have been detected above 10 keV. Here we present an overview of a program to survey six normal/starburst galaxies at hard X-ray energies. As of early 2013, only the NuSTAR-Chandra-VLBA multiwavelength campaign on NGC 253 has been performed, consisting of three observational periods. The monitoring was designed to (1) sensitively isolate the locations of X-ray binaries, (2) determine the nature of the accreting compact objects via their 0.5-30 keV spectral properties, and (3) identify interesting flaring X-ray/radio sources as they make spectral state transitions due to variability in their accretion. We will also discuss upcoming observations of the rest of the sample.

Hornschemeier, Ann; Argo, Megan; Bechtol, Keith; Boggs, Steve; Christensen, Finn; Craig, William; Hailey, Charles; Harrison, Fiona; Lehmer, Bret; Leyder, J.-C.; Maccarone, Thomas; Ptak, Andrew; Stern, Daniel; Venters, Tonia; Wik, Daniel; Zezas, Andreas; Zhang, William

2013-04-01

275

X-ray emission processes in stars and their immediate environment  

PubMed Central

A decade of X-ray stellar observations with Chandra and XMM-Newton has led to significant advances in our understanding of the physical processes at work in hot (magnetized) plasmas in stars and their immediate environment, providing new perspectives and challenges, and in turn the need for improved models. The wealth of high-quality stellar spectra has allowed us to investigate, in detail, the characteristics of the X-ray emission across the Hertzsprung-Russell (HR) diagram. Progress has been made in addressing issues ranging from classical stellar activity in stars with solar-like dynamos (such as flares, activity cycles, spatial and thermal structuring of the X-ray emitting plasma, and evolution of X-ray activity with age), to X-ray generating processes (e.g., accretion, jets, magnetically confined winds) that were poorly understood in the preChandra/XMM-Newton era. I will discuss the progress made in the study of high energy stellar physics and its impact in a wider astrophysical context, focusing on the role of spectral diagnostics now accessible.

Testa, Paola

2010-01-01

276

X-ray emission processes in stars and their immediate environment.  

PubMed

A decade of X-ray stellar observations with Chandra and XMM-Newton has led to significant advances in our understanding of the physical processes at work in hot (magnetized) plasmas in stars and their immediate environment, providing new perspectives and challenges, and in turn the need for improved models. The wealth of high-quality stellar spectra has allowed us to investigate, in detail, the characteristics of the X-ray emission across the Hertzsprung-Russell (HR) diagram. Progress has been made in addressing issues ranging from classical stellar activity in stars with solar-like dynamos (such as flares, activity cycles, spatial and thermal structuring of the X-ray emitting plasma, and evolution of X-ray activity with age), to X-ray generating processes (e.g., accretion, jets, magnetically confined winds) that were poorly understood in the preChandra/XMM-Newton era. I will discuss the progress made in the study of high energy stellar physics and its impact in a wider astrophysical context, focusing on the role of spectral diagnostics now accessible. PMID:20360562

Testa, Paola

2010-04-01

277

X-RAY AND TeV EMISSIONS FROM HIGH-FREQUENCY-PEAKED BL LAC OBJECTS  

SciTech Connect

The majority of the extragalactic sources yet detected at TeV photon energies belong to the class of 'high-frequency-peaked BL Lac objects' (HBLs) that exhibit a spectral energy distribution with a lower peak in the X-ray band. Such spectra are well described in terms of a log-parabolic shape with considerable curvature, and widely interpreted as synchrotron emission from ultrarelativistic electrons outflowing in a relativistic jet; these are expected to radiate also in {gamma}-rays through the inverse Compton process. Recently, we have compared the X-ray spectral parameter distributions of TeV detected HBLs (TBLs) with those undetected (UBLs), and found that the distributions of the peak energies E{sub p} are similarly symmetric around a value of a few keVs for both subclasses, while the X-ray spectra are broader for TBLs than for UBLs. Here we propose an acceleration scenario to interpret both the E{sub p} and the spectral curvature distributions in terms of a coherent and a stochastic acceleration mechanisms, respectively. We show how the curvature parameter b {approx_equal} 0.3-0.7 of the synchrotron X-rays, which depends only on the latter acceleration component, can be related to the inverse Compton luminosity in {gamma}-rays, thus introducing a link between the X-ray and the TeV observations of HBLs.

Massaro, F.; Paggi, A. [Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Cavaliere, A. [Dipartimento di Fisica, Universita di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (Italy)

2011-12-15

278

Discovery of X-Ray Emission in the Old Classical Nova DK Lacertae  

NASA Astrophysics Data System (ADS)

We report the discovery of X-ray emission at the position of the old classical nova DK Lacertae using the Swift satellite. Three observations were conducted using the X-Ray Telescope 62 years after the discovery of the nova, yielding 46 source signals in an exposure time of 4.8 ks. A background-subtracted count rate was 9 ± 2 × 10-3 counts s-1, corresponding to a detection significance level of 5?. The X-ray spectrum was characterized by a continuum extending up to about 7 keV, which can be modeled by a power-law component with a photon index of 1.4-5.6, or by a thermal bremsstrahlung component with a temperature of 0.7-13.3 keV, convolved with interstellar absorption with an equivalent hydrogen column density of 0.3-2.4 × 1022 cm-2. Assuming a distance of 3900 pc to the source, the luminosity was 1032-1034 erg s-1 in the 0.3-10 keV energy band. The origin of X-rays is considered to be either mass accretion on the white dwarf or adiabatic shocks in nova ejecta, with the former appearing much more likely. In either case, DK Lacertae represents a rare addition to the exclusive club of X-ray emitting old novae.

Takei, D.; Sakamoto, T.; Drake, J. J.

2013-01-01

279

Charge exchange x-ray emission: Astrophysical observations and potential diagnostics  

NASA Astrophysics Data System (ADS)

Interest in astrophysical sources of charge exchange X-rays has been growing steadily since the discovery of X-ray emission from the comet Hyakutake with ROSAT in 1996. Since then, charge exchange has been observed between solar wind ions and neutrals in the geocorona and in the atmospheres of Mars and Jupiter. Charge exchange with interstellar neutrals within the heliosphere between solar wind ions and neutral hydrogen and helium from the interstellar medium is now acknowledged as contributing a considerable (although currently unknown) fraction of the soft X-ray background. We make a brief survey of the heliospheric, Galactic, and extragalactic systems in which charge exchange has been observed or is predicted to take place. Experiments measuring velocity dependent cross-section and line ratios for Lyman-series lines and He-like triplets are needed to check current theoretical models of charge exchange emission and aid interpretation of observations. We point out a number of systems that are of astrophysical interest that could be the subject of future laboratory investigations, particularly velocity dependent line ratios of the X-ray emission produced by charge exchange between highly ionized common elements (such as O, C, Ne, and Fe) and atomic hydrogen and helium. To begin to address the need for laboratory data we have measured velocity dependent Ly-series line ratios for C6+ ions interacting with H2, He, and Kr gas targets at Oak Ridge National Laboratory's Ion-Atom Merged-Beams Apparatus.

Morgan, K.; Andrianarijaona, V.; Draganic, I. N.; Defay, X.; Fogle, M.; Galindo-Uribarri, A.; Guillen, C. I.; Havener, C. C.; Hokin, M.; McCammon, D.; Nader, D. J.; Romano, S. L.; Carcoba, F. Salces; Sauter, P.; Seely, D.; Stancil, P. C.; Vane, C. R.; Vassantachart, A. K.; Wulf, D.

2013-04-01

280

Hard X-ray Emission by Resonant Compton Upscattering in Magnetars  

NASA Astrophysics Data System (ADS)

For inner magnetospheric models of hard X-ray and gamma-ray emission in high-field pulsars and magnetars, resonant Compton upscattering is anticipated to be the most efficient process for generating continuum radiation. For magnetars, this is due in part to the proximity of a hot soft photon bath from the stellar surface. Moreover, the scattering cross section becomes resonant at the cyclotron frequency, exceeding the classical Thomson value by over two orders of magnitude and thereby enhancing the efficiency of continuum production and the cooling of relativistic electrons. We present angle-dependent hard X-ray upscattering model spectra for uncooled monoenergetic relativistic electrons injected in inner regions of pulsar magnetospheres. These spectra are integrated over closed field lines and obtained for different observing perspectives. Electron cooling rates for resonant Compton interactions are also presented, in preparation for future radiation-reaction limited acceleration and emission models of non-thermal magnetar X-rays. Our research employs a new Sokolov and Ternov (ST) formulation of the QED Compton scattering cross section in strong magnetic fields. Such an ST formalism is formally correct for treating spin-dependent effects that are important in the cyclotron resonance, and has not been addressed before in the context of Compton upscattering models of magnetar hard X-ray tail emission.

Wadiasingh, Zorawar; Baring, M. G.; Gonthier, P. L.; Harding, A. K.

2012-01-01

281

RECONNECTION ELECTRIC FIELD AND HARDNESS OF X-RAY EMISSION OF SOLAR FLARES  

SciTech Connect

Magnetic reconnection is believed to be the prime mechanism that triggers solar flares and accelerates electrons up to energies of MeV. In the classical two-dimensional reconnection model, the separation motion of chromospheric ribbons, manifests the successive reconnection that takes place higher up in the corona. Meanwhile, downward traveling energetic electrons bombard the dense chromosphere and create hard X-ray (HXR) emissions, which provide a valuable diagnostic of electron acceleration. Analyses of ribbon dynamics and the HXR spectrum have been carried out separately. In this Letter, we report a study of the comparison of reconnection electric field measured from ribbon motion and hardness (spectral index) of X-ray emission derived from X-ray spectrum. Our survey of the maximum average reconnection electric field and the minimum overall spectral index for 13 two-ribbon flares shows that they are strongly anticorrelated. The former is also strongly correlated with flare magnitude measured using the peak flux of soft X-ray emissions. These provide strong support for electron acceleration models based on the electric field generated at reconnecting current sheet during flares.

Liu Chang; Wang Haimin [Space Weather Research Laboratory, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, University Heights, Newark, NJ 07102 (United States)], E-mail: chang.liu@njit.edu, E-mail: haimin@flare.njit.edu

2009-05-01

282

A Comparison of X-Ray and Radio Emission from the Supernova Remnant Cassiopeia A  

NASA Astrophysics Data System (ADS)

We compare the radio and soft X-ray brightnesses as a function of position within the young supernova remnant Cassiopeia A. A moderately strong correlation (r = 0.7) was found between the X-ray emission (corrected for interstellar absorption) and radio emission, showing that the thermal and relativistic plasmas occupy the same volumes and are regulated by common underlying parameters. The logarithmic slope of the relationship, ln Sx = 1.2lnSradio + ln k, implies that the variations in brightness are primarily due to path length differences. The X-ray and radio emissivities are both high in the same general locations, but their more detailed relationship is poorly constrained and probably shows significant scatter. The strongest radio and X-ray absorption is found at the western boundary of Cas A. Based on the properties of Cas A and the absorbing molecular cloud, we argue that they are physically interacting. We also compare column densities derived from the Advanced Satellite for Cosmology and Astrophysics with 21 cm H I and 18 cm OH optical depths in the direction of Cas A, in order to provide an independent estimate of interstellar medium properties. We derive an average value for the H I spin temperature of ?40 K and measure the ratio OH/H2, which is nominally larger than previous estimates.

Keohane, Jonathan W.; Rudnick, Lawrence; Anderson, Martha C.

1996-07-01

283

Detection of Diffuse X-Ray Emission from Planetary Nebulae with Nebular O VI  

NASA Astrophysics Data System (ADS)

The presence of O VI ions can be indicative of plasma temperatures of a few ×105 K that are expected in heat conduction layers between the hot shocked stellar wind gas at several 106 K and the cooler (104 K) nebular gas of planetary nebulae (PNe). We have used FUSE observations of PNe to search for nebular O VI emission or absorption as a diagnostic of the conduction layer to ensure the presence of hot interior gas. Three PNe showing nebular O VI, namely IC 418, NGC 2392, and NGC 6826, have been selected for Chandra observations and diffuse X-ray emission is indeed detected in each of these PNe. Among the three, NGC 2392 has peculiarly high diffuse X-ray luminosity and plasma temperature compared with those expected from its stellar wind's mechanical luminosity and terminal velocity. The limited effects of heat conduction on the plasma temperature of a hot bubble at the low terminal velocity of the stellar wind of NGC 2392 may partially account for its high plasma temperature, but the high X-ray luminosity needs to be powered by processes other than the observed stellar wind, probably the presence of an unseen binary companion of the central star of the PN (CSPN) of NGC 2392. We have compiled relevant information on the X-ray, stellar, and nebular properties of PNe with a bubble morphology and found that the expectations of bubble models including heat conduction compare favorably with the present X-ray observations of hot bubbles around H-rich CSPNe, but have notable discrepancies for those around H-poor [WR] CSPNe. We note that PNe with more massive central stars can produce hotter plasma and higher X-ray surface brightness inside central hot bubbles.

Ruiz, N.; Chu, Y.-H.; Gruendl, R. A.; Guerrero, M. A.; Jacob, R.; Schönberner, D.; Steffen, M.

2013-04-01

284

Experiments Characterizing the X-Ray Emission from a Solid-State Cathode Using a High-Current Glow Discharge  

NASA Astrophysics Data System (ADS)

X-ray emission (with intensity up to 0.01 Gy/s) was recorded in research on a possible mechanism of initiating nuclear transmutation reactions in a solid-state cathode medium in glow discharge experiments. The experiments were carried using a glow discharge1 with deuterium and hydrogen (at pressures up to 10 Torr), and using various cathode metals (Al, Sc, Ti, Ni, Nb, Zr, Mo, Pd, Ta, W, Pt and Pb). The x-rays were recorded using thermoluminescent detectors, x-ray film, and scintillation detectors with photomultipliers. Two different modes of the emission were observed during these experiments: (1) Diffusion x-rays were observed as separate x-ray bursts (up to 105 bursts a second and up to 106 x-ray quanta in a burst) with an average x-rays energy (from measurements using thermoluminescent detectors) in the range of 1.3-1.8 keV. (2) X-rays as laser microbeams (up to 104 beams a second and up to 109 x-ray quanta in a burst). The emission of the x-ray laser beams occurred during the discharge, and within 100ms after turning off the discharge current. The results obtained constitute a direct experimental proof for the existence of excited metastable energy levels with energies in the range 1.2-5.0 keV, within the solid-state cathode sample.

Karabut, A. B.; Kolomeychenko, S. A.

2005-12-01

285

JUXTA: A Probe of X-ray Emission from Jupiter's Magnetosphere  

NASA Astrophysics Data System (ADS)

We introduce an unique instrument for the future Japanese exploration mission of Jupiter's magnetosphere (JMO: Jupiter Magnetospheric Orbiter). The proposed launch year of JMO is around 2022. Our instrument named JUXTA (Jupiter X-ray Telescope Array) aims at the first in-situ measurement of X-ray emission associated with acceleration processes in Jupiter's magnetosphere. Recent observations with Earth-orbiting satellites have revealed the existence of various X-ray emissions from the Jupiter system. For instance, Jupiter's aurorae emit X-rays by bremsstrahlung of keV electrons (Gladstone et al. 2002 Nature) and also charge exchange interaction of MeV ions from the solar wind and magnetospheric ions (Branduardi-Raymont et al. 2007 A&A). Inner radiation belts could emit diffuse X-ray emission by inverse-Compton scattering of solar photons by tens MeV electrons (Ezoe et al. 2009 ApJL). Thus, the X-ray imaging spectroscopy is a direct probe of dynamic accelerated particles, their coupling to the plasma waves and their solar wind interaction in Jupiter's magnetosphere. However, the limited photon statistics and image/time resolution hinder us from fully utilizing these phenomena. Therefore, we have proposed and been developing an in-situ X-ray imaging spectroscopy instrument, JUXTA. It is composed of an ultra-light weight X-ray telescope based on micromachining technology and a radiation-hard semiconductor pixel detector. JUXTA is a Latin word meaning proximity. JUXTA covers 0.3--2 keV with the energy resolution of <100 eV at 0.6 keV. Because of its proximity to Jupiter (˜30 Rj at periapsis), the image resolution of <5 arcmin corresponds to <˜10000 km on the surface of Jupiter and the effective area of >3 cm^2 at 0.6 keV allows high quality light curves from auroral hot spots with the time resolution of <˜60 s. In this presentation, science target and instrument design of JUXTA are presented.

Ezoe, Yuichiro; Kasahara, Satoshi; Miyoshi, Yoshizumi; Yamazaki, Atsushi; Mitsuda, Kazuhisa; Kimura, Tomoki; Ohashi, Takaya; Ishikawa, Kumi; Fujimoto, Masaki

2012-07-01

286

Electronic Structure in Thin Film Organic Semiconductors Studied using Soft X-ray Emission and Resonant Inelastic X-ray Scattering  

SciTech Connect

The electronic structure of thin films of the organic semiconductors copper and vanadyl (VO) phthalocyanine (Pc) has been measured using resonant soft X-ray emission spectroscopy and resonant inelastic X-ray scattering. For Cu-Pc we report the observation of two discrete states near E{sub F}. This differs from published photoemission results, but is in excellent agreement with density functional calculations. For VO-Pc, the vanadyl species is shown to be highly localized. Both dipole forbidden V 3d to V 3d*, and O 2p to V 3d* charge transfer transitions are observed, and explained in a local molecular orbital model.

Zhang,Y.; Downes, J.; Wang, S.; Learmonth, T.; Plucinski, L.; Matsuura, A.; McGuinness, C.; Glans, P.; Bernardis, S.; et al.

2006-01-01

287

Exploring the Diffuse X-ray Emission of Supernova Remnant Kesteven 69 with XMM-Newton  

NASA Astrophysics Data System (ADS)

We have investigated the X-ray emission from the shock-heated plasma of the Galactic supernova remnant Kesteven 69 with XMM-Newton. Assuming the plasma is at collisional ionization equilibrium, a plasma temperature and a column absorption are found to be kT ~ 0.62 keV and NH ~ 2.85 ×10^22 cm-2 respectively by imaging spectroscopy. Together with the deduced emission measure, we place constraints on its Sedov parameters.

Seo, Kyoung-Ae; Hui, Chung Yue

2013-06-01

288

Magnetism in FeO at Megabar Pressures from X-Ray Emission Spectroscopy  

Microsoft Academic Search

We report evidence for a preserved magnetic state in FeO up to 143 GPa at room temperature using high-resolution x-ray emission spectroscopy. This observation is based on the spectral line shape of the Fe Kbeta emission line. Up to the highest pressure, FeO remains a magnetic insulator. Combining our results with previous Mössbauer data, we present a new magnetic phase

James Badro; Viktor V. Struzhkin; Jinfu Shu; Russell J. Hemley; Ho-Kwang Mao; Chi-Chang Kao; Jean-Pascal Rueff; Guoyin Shen

1999-01-01

289

Particle-Induced X-Ray Emission Analysis of Atmospheric Aerosols  

Microsoft Academic Search

We are developing a research program in ion-beam analysis (IBA) of atmospheric aerosols at the Union College Ion-Beam Analysis Laboratory to study the transport, transformation, and effects of airborne pollution in Upstate New York. The simultaneous applications of the IBA techniques of particle-induced X-ray emission (PIXE), Rutherford back-scattering spectrometry (RBS), particle-induced gamma-ray emission (PIGE), and proton elastic scattering analysis (PESA)

Colin Gleason; Charles Harrington; Katie Schuff; Maria Battaglia; Robert Moore; Colin Turley; Michael Vineyard; Scott Labrake

2010-01-01

290

Proton-induced X-ray and gamma ray emission analysis of biological samples  

Microsoft Academic Search

A 4.1 MeV external proton beam was employed to simultaneously induce X-ray emission (PIXE) and gamma ray emission (PIGE) in biological samples that included human colostrum, spermatozoa, teeth, tree-rings, and follicular fluids. The analytical method was developed to simultaneously determine the elements lithium (Z = 3) through uranium (Z = 92) in the samples. PIXE-PIGE experimental design is described as

Gene S. Hall; Eliahu Navon

1986-01-01

291

Intragroup and Galaxy-linked Diffuse X-Ray Emission in Hickson Compact Groups  

NASA Astrophysics Data System (ADS)

Isolated compact groups (CGs) of galaxies present a range of dynamical states, group velocity dispersions, and galaxy morphologies with which to study galaxy evolution, particularly the properties of gas both within the galaxies and in the intragroup medium. As part of a large, multiwavelength examination of CGs, we present an archival study of diffuse X-ray emission in a subset of nine Hickson compact groups (HCGs) observed with the Chandra X-Ray Observatory. We find that seven of the groups in our sample exhibit detectable diffuse emission. However, unlike large-scale emission in galaxy clusters, the diffuse features in the majority of the detected groups are linked to the individual galaxies, in the form of both plumes and halos likely as a result of vigourous star formation or activity in the galaxy nucleus, as well as in emission from tidal features. Unlike previous studies from earlier X-ray missions, HCGs 31, 42, 59, and 92 are found to be consistent with the LX -T relationship from clusters within the errors, while HCGs 16 and 31 are consistent with the cluster LX -? relation, though this is likely coincidental given that the hot gas in these two systems is largely due to star formation. We find that LX increases with decreasing group H I to dynamical-mass ratio with tentative evidence for a dependence in X-ray luminosity on H I morphology whereby systems with intragroup H I indicative of strong interactions are considerably more X-ray luminous than passively evolving groups. We also find a gap in the LX of groups as a function of the total group specific star formation rate. Our findings suggest that the hot gas in these groups is not in hydrostatic equilibrium and these systems are not low-mass analogs of rich groups or clusters, with the possible exception of HCG 62.

Desjardins, Tyler D.; Gallagher, Sarah C.; Tzanavaris, Panayiotis; Mulchaey, John S.; Brandt, William N.; Charlton, Jane C.; Garmire, Gordon P.; Gronwall, Caryl; Hornschemeier, Ann E.; Johnson, Kelsey E.; Konstantopoulos, Iraklis S.; Zabludoff, Ann I.

2013-02-01

292

Making use of x-ray optical effects in photoelectron-, Auger electron-, and x-ray emission spectroscopies: Total reflection, standing-wave excitation, and resonant effects  

NASA Astrophysics Data System (ADS)

We present a general theoretical methodology and related open-access computer program for carrying out the calculation of photoelectron, Auger electron, and x-ray emission intensities in the presence of several x-ray optical effects, including total reflection at grazing incidence, excitation with standing-waves produced by reflection from synthetic multilayers and at core-level resonance conditions, and the use of variable polarization to produce magnetic circular dichroism. Calculations illustrating all of these effects are presented, including in some cases comparisons to experimental results. Sample types include both semi-infinite flat surfaces and arbitrary multilayer configurations, with interdiffusion/roughness at their interfaces. These x-ray optical effects can significantly alter observed photoelectron, Auger, and x-ray intensities, and in fact lead to several generally useful techniques for enhancing surface and buried-layer sensitivity, including layer-resolved densities of states and depth profiles of element-specific magnetization. The computer program used in this study should thus be useful for a broad range of studies in which x-ray optical effects are involved or are to be exploited in next-generation surface and interface studies of nanoscale systems.

Yang, S.-H.; Gray, A. X.; Kaiser, A. M.; Mun, B. S.; Sell, B. C.; Kortright, J. B.; Fadley, C. S.

2013-02-01

293

Synchrotron radiation based micro X-ray fluorescence analysis of the calibration samples used in surface sensitive total reflection and grazing emission X-ray fluorescence techniques  

NASA Astrophysics Data System (ADS)

Total reflection X-ray fluorescence (TXRF) and grazing emission X-ray fluorescence (GEXRF) are surface sensitive techniques and can be used for detailed surface studies of different materials, including ultra-low concentration contamination or the lateral and depth distributions of elements. The calibration procedure typically used involves placing a micro-droplet (˜?l) of the standard solution onto a silicon wafer (or quartz backing). After evaporation of the solvent, the residual amount of elements is used as a reference standard. Knowledge of the distribution of residue material on the substrate surface is crucial for precise quantification. In the present work the investigation of the lateral distribution of elements in the multielemental calibrating samples, containing the 23 most commonly studied elements, by using the synchrotron radiation based micro X-ray fluorescence is presented. The goal of this project was the study of a uniformity of the elemental distributions and determination of the residual elements morphology depending on the temperature of the drying process. The X-ray images were compared with optical and SEM images. Paper presents in details the experimental setup, sample preparation procedures, measurements and results. In the analysis of the X-ray images of the sample dried in high temperature the censoring approach was applied improving the quality of statistical analysis. The information on the elements distribution in the calibrating samples can be useful for developing more accurate calibration procedures applied in quantitative analysis of surface sensitive TXRF and GEXRF techniques.

Kubala-Kuku?, A.; Bana?, D.; Pajek, M.; Szlachetko, J.; Jagodzi?ski, P.; Susini, J.; Salomé, M.

2013-12-01

294

Interpretation of perturbed temperature based on X-ray emissivity in fusion plasma experiments  

NASA Astrophysics Data System (ADS)

The relationship between the dynamical response to perturbations of the soft X-ray emissivity (?E), the electron temperature (?Te), the electron density (?ne) and the impurity concentration (?ni) for a Maxwellian plasma is analysed in detail. In particular, the so-called 'impurity function' F(Zeff) is also strongly dependent on Te via the direct radiative recombination (DRR) contribution to the X-ray emission, which significantly affects the relation between the perturbed quantities as derived from the popular expression E propto F(Zeff)ne2Tealpha even if the impurity content (or Zeff) remains constant. In order to overcome this difficulty, a simple analytical approximation is derived for F(Zeff,Te) that can be used as a formula to relate the perturbed quantities ?E, ?Te, ?ne and ?F with ease and accuracy. This simple approximation is illustrated by studying saw-toothing discharges on the Tokamak de Varennes (TdeV) with Te, ne and E measured by the Thomson scattering, the FIR interferometer and the X-ray camera diagnostics, and its accuracy is tested against the predictions of a full X-ray modelling code

Janicki, C.; Cote, A.; Dichaud, D.

1995-05-01

295

X-ray emission from the winds of hot stars. II  

SciTech Connect

The kinematic model adopted in Paper I for the limiting amplitude state attained by the unstable line-driven winds of early-type stars is modified, a crucial but neglected physical effect is crudely taken into account, and the resulting x-ray spectra compared with observation. In this revised phenomenonlogical theory, radiatively driven shocks are conjectured to result from the amplification of unstable waves and to survive until shadowing by following shocks compels their decay. In consequence of this shock destruction mechanism, the revised theory predicts that x-ray emission continues far out into the nearly terminal flow; the effects of self-absorption-in particular, discontinuities at K-shell edges: are therefore not now expected to be prominent, a result qualitatively consistent with recent analyses of Einstein data. Nevertheless, with the preferred choice for the theory's single free parameter the x-ray luminosities calculated for several O stars are too low and the spectra too soft. These failures are interpreted as implying a broad spectrum of shock strengths, with the bulk of the x-ray emission coming from the strongest shocks.

Lucy, L.B.

1982-04-01

296

Thermal and Nonthermal X-Ray Emission from the Forward Shock in Tycho's Supernova Remnant  

NASA Astrophysics Data System (ADS)

We present Chandra X-ray images of Tycho's supernova remnant that delineate its outer shock as a thin, smooth rim along the straight northeastern edge and most of the circular western half. The images also show that the Si and S ejecta are highly clumpy and have reached near the forward shock at numerous locations. Most of the X-ray spectra that we examine along the rim show evidence of line emission from Si and S ejecta, while the continuum is well represented by either a thermal or a nonthermal model. If the continuum is assumed to be thermal, the electron temperatures at the rim are all similar at about 2 keV, while the ionization ages are very low because of the overall weakness of the line emission. These electron temperatures are substantially below those expected for equilibration of the electron and ion temperatures, assuming shock velocities inferred from radio and X-ray expansion measurements; the electron-to-mean temperature ratios are <~0.1-0.2, indicating that collisionless heating of the electrons at the shock is modest. The nonthermal contribution to these spectra might be important, but cannot be strongly constrained by these data. It could account for as much as half of the flux in the 4-6 keV energy range, based on an extrapolation of the hard X-ray spectrum above 10 keV.

Hwang, Una; Decourchelle, Anne; Holt, Stephen S.; Petre, Robert

2002-12-01

297

Thermal disc emission from a rotating black hole: X-ray polarization signatures  

NASA Astrophysics Data System (ADS)

Thermal emission from the accretion disc around a black hole can be polarized, due to Thomson scattering in a disc atmosphere. In Newtonian space, the polarization angle must be either parallel or perpendicular to the projection of the disc axis on the sky. As first pointed out by Stark and Connors in 1977, General Relativity effects strongly modify the polarization properties of the thermal radiation as observed at infinity. Among these effects, the rotation of the polarization angle with energy is particularly useful as a diagnostic tool. In this paper, we extend the Stark and Connors calculations by including the spectral hardening factor, several values of the optical depth of the scattering atmosphere and rendering the results to the expected performances of planned X-ray polarimeters. In particular, to assess the perspectives for the next generation of X-ray polarimeters, we consider the expected sensitivity of the detectors on board the planned POLARIX and International X-ray Observatory missions. We assume the two cases of a Schwarzschild and an extreme Kerr black hole with a standard thin disc and a scattering atmosphere. We compute the expected polarization degree and the angle as functions of the energy as they could be measured for different inclinations of the observer, optical thickness of the atmosphere and different values of the black hole spin. We assume the thermal emission dominates the X-ray band. Using the flux level of the microquasar GRS 1915+105 in the thermal state, we calculate the observed polarization.

Dov?iak, M.; Muleri, F.; Goosmann, R. W.; Karas, V.; Matt, G.

2008-11-01

298

Study of the soft X-ray emission from carbon ions in a capillary discharge  

NASA Astrophysics Data System (ADS)

The soft X-ray emission from plasmas produced in polyacetal and polyethylene capillary discharges excited by current pulses 100 ns full-width half-maximum (FWHM), 50-ns risetime, and peak currents up to 60 kA has been studied. Time-resolved spectra show that intense CVI line emission dominates in the polyethylene discharges, peaking shortly after the maximum of the current and vanishing before the end of the current pulse. Polyacetal capillary spectra are dominated by OVI lines and show weak CVI emission. Plasma density and temperature for the polyethylene discharge were derived from the Stark broadening of CVI Balmer lines and the relative intensities of CVI and CV lines. A short (5-ns FWHM) pulse of energetic beam electrons was detected in coincidence with the onset of the discharge. The results are discussed in relation to the possibility of obtaining soft X-ray amplification by plasma recombination in a capillary discharge plasma column.

Rocca, Jorge J.; Marconi, Mario C.; Tomasel, F. G.

1993-01-01

299

Charge Transfer Data Needs for Cometary X-ray Emission Modeling  

NASA Astrophysics Data System (ADS)

The emission of x-rays has been observed from nearly twenty comets and evidence exists that it is the result of radiative decays from highly-excited, highly-charged solar wind ions following charge exchange with neutral species, mostly water, in the cometary atmosphere. We review the progress to date in constructing models of the x-ray emission. However, the construction of accurate models is impeded by the near lack of reliable state-selective charge exchange cross section data for the relevant neutral species (H2O, CO, CO2, etc.). The progress, and difficulties, of theoretical studies for the relevant collision processes is discussed with a particular focus on the breakdown of approximations made in the emission models.

Stancil, P. C.; Wang, J. G.; Rakovic, M. J.; Schultz, D. R.; Ali, R.

2002-10-01

300

Soft x-ray emission from solar wind charge exchange in the laboratory  

NASA Astrophysics Data System (ADS)

We have observed the emission spectra in collisions of bare oxygen ions with a helium gas target in the soft x-ray region with a window-less silicon drift detector at the collision energy range of 48-80 keV. The dominant soft x-ray emission corresponds to the 1s-2p transition of hydrogen-like oxygen O7+ produced by the single-electron charge exchange reaction. Other emission lines are the 1s-3p, 1s-4p and 1s-5p transitions of O7+, and also the 1s2-1s2p transition of O6+ produced by the true double-electron capture. The cascades from the upper states result in a large population of the 2p state, even though the direct capture into the 2p state is extremely scarcer than those into the 3p, 4p and 5p states.

Shimaya, H.; Ishida, T.; Ishikawa, S.; Suda, S.; Tanuma, H.; Akamatsu, H.; Ohashi, H.; Ijima, N.; Inoue, M.; Ezoe, Y.; Ishisaki, Y.; Ohashi, T.; Shinozaki, K.; Mitsuda, K.; Liu, L.; Wang, J.

2013-09-01

301

Search for x-ray driven gamma emission from 178Hf using the YSU miniball array  

NASA Astrophysics Data System (ADS)

At present, studies of x-ray driven gamma emission are constrained by the extremely small size of available targets. In order to apply a more sensitive experimental approach to the search for driven gamma emission, the YSU miniball detector array has been constructed. This array utilizes similar principles to those employed at large many-detector arrays to capture multiple gamma-ray cascades emitted in spontaneous and driven events. A monochromatic beam from the National Synchrotron Light Source has been employed in conjunction with the YSU miniball array to search for evidence for x-ray driven gamma emission from the 31-yr isomer of 178Hf. This poster will illustrate miniball development and the experimental setup and results.

Propri, Ron; Burnett, Jason; Drummond, Tom; Lepak, Joel; Smith, David; Carroll, James; Helba, Mike; Roberts, Hill; Karamian, Sarkis; Adam, Jindrich; Stedile, Frank; Zhong, Zhong; Agee, F. J.

2002-10-01

302

Spectral Properties of Post-Quiescent Emission of Gamma-Ray Bursts  

Microsoft Academic Search

We examine the spectral properties of quiescent Gamma-Ray Bursts (GRB) in the BATSE catalog. Quiescent GRBs are bursts whose emission drops below the background level for some period of time that is comparable to the duration of the emission episode, followed by a resurgence of emission. A careful inspection of late times in GRB light curves, after the GRB has

T. M. Freismuth; T. Giblin; J. Hakkila

2003-01-01

303

COMPARISON OF MILLIMETER-WAVE AND X-RAY EMISSION IN SEYFERT GALAXIES  

SciTech Connect

We compare the emission at multiple wavelengths of an extended Seyfert galaxy sample, including both types of Seyfert nuclei. We use the Caltech Submillimeter Observatory to observe the CO J = 2-1 transition line in a sample of 45 Seyfert galaxies and detect 35 of them. The galaxies are selected by their joint soft X-ray (0.1-2.4 keV) and far-infrared ({lambda} = 60-100 {mu}m) emission from the ROSAT/IRAS sample. Since the CO line widths (W{sub CO}) reflect the orbital motion in the gravitational potential of the host galaxy, we study how the kinematics are affected by the central massive black hole (BH), using the X-ray luminosity. A significant correlation is found between the CO line width and hard (0.3-8 keV from Chandra and XMM-Newton) X-ray luminosity for both types of Seyfert nuclei. Assuming an Eddington accretion to estimate the BH mass (M{sub BH}) from the X-ray luminosity, the W{sub CO}-L{sub X} relation establishes a direct connection between the kinematics of the molecular gas of the host galaxy and the nuclear activity, and corroborates the previous studies that show that the CO is a good surrogate for the bulge mass. We also find a tight correlation between the (soft and hard) X-ray and the CO luminosities for both Seyfert types. These results indicate a direct relation between the molecular gas (i.e., star formation activity) of the host galaxy and the nuclear activity. To establish a clear causal connection between molecular gas and the fueling of nuclear activity, high-resolution maps (<100 pc) of the CO emission of our sample will be required and provided in a forthcoming Atacama Large Millimeter Array observation.

Monje, R. R.; Blain, A. W.; Phillips, T. G. [Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125-4700 (United States)

2011-08-01

304

Multibeam field emission x-ray system with half-scan reconstruction algorithm  

SciTech Connect

Purpose: In this article, the authors propose a multibeam field emission x-ray (MBFEX) system along with a half-scan fan-beam reconstruction algorithm. Methods: The proposed system consists of a linear CNT-based MBFEX source array, a single large area detector that is divided into same number of segments as the number of x-ray beams, a multihole collimator that aligns each beam with a corresponding detector segment, and a sample rotation stage. The collimator is placed between the source and the object to restrict the x-ray radiations through the target object only. In this design, all the x-ray beams are activated simultaneously to provide multiple projection views of the object. The detector is virtually segmented and synchronized with the x-ray exposure and the physiological signals when gating is involved. The transmitted x-ray intensity from each beam is collected by the corresponding segment on the detector. After each exposure, the object is rotated by a step angle until sufficient data set is collected. The half-scan reconstruction formula for MBFEX system is derived from the conventional filtered backprojection algorithm. To demonstrate the advantages of the system and method in reducing motion artifacts, the authors performed simulations with both standard and dynamic Shepp-Logan phantoms. Results: The numerical results indicate that the proposed multibeam system and the associated half-scan algorithm can effectively reduce the scanning time and improve the image quality for a time-varying object. Conclusions: The MBFEX technique offers an opportunity for the innovation of multisource imaging system.

Lu Yang; Yu Hengyong; Cao Guohua; Zhao Jun; Wang Ge; Zhou, Otto [Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); SBES Division and ICTAS Center for Biomedical Imaging, Virginia Tech, Blacksburg, Virginia 24061 (United States); Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); SBES Division and ICTAS Center for Biomedical Imaging, Virginia Tech, Blacksburg, Virginia 24061 (United States); Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)

2010-07-15

305

Study of ?-ray and X-ray emission from BL LAC objects  

NASA Astrophysics Data System (ADS)

This paper collects 18 ?-ray-loud BL Lacertae (BL Lac) objects with the observed X-ray and ?-ray flux densities (maximum, minimum, average) as well as the X-ray (1keV) and ?-ray (above 100MeV) average spectral indices.These flux densities and average spectral indices data came from 33 literatures. To analysis the character between X-ray and ?-ray flux densities in the maximum(, ) , minimum (, ) and average(, ) value and those average spectral indices( , ) , we employed the correlation analysis. We studied their correlations in detail, and our results show that:1) there is a strong correlation between and in the high, average and low state.This result affirmed Stickel et al. [53]model which supposed express a few dust around the black hole.2) there is a strong correlations between and in the average state.3) there is not a significant correlation between the average spectral indices and the flux densities in high and average state.4) there is a strong anti-correlation between the average ?-ray spectral indices and the X-ray flux densities in the low state, and also there is a weak correlation between the average X-ray spectral indices and the ?-ray flux densities in the low state.Our results are in agreement with the scenario that the X-ray and ?-ray emission from BL Lac objects are likely produced by the same population of relativistic electrons through synchrotron and synchrotron Self-Compton model (SSC) process, respectively.

Zhang, H. J.; Zhang, X.

2008-07-01

306

X-ray emission cross sections following charge exchange by multiply charged ions of astrophysical interest  

NASA Astrophysics Data System (ADS)

State selective nl -electron capture cross sections are presented for highly charged ions with Z=6-10 colliding with atoms and molecules. The energy range investigated was from 1eV/amu(v=0.006a.u.)to100keV/amu(v=2.0a.u.) . The energy dependence of the l -level populations is investigated. The K shell x-ray emission cross sections are determined by using the calculated state-selective electron capture results as input and then applying hydrogenic branching and cascading values for the photon emission. A major shift in the line emission from being almost solely Lyman- ? transitions at the highest collisions energies to strong high- n to 1s transitions at the lowest energies is observed. The calculated cross sections are in reasonable accord with measurements made by Greenwood [Phys. Rev. A 63, 062707 (2001)], using O8+ and Ne10+ on various targets at 3keV/amu . The calculations are also in accord with x-ray emission cross section data obtained on the EBIT machine at Lawrence Livermore National Laboratory (LLNL) where O8+ and Ne10+ high resolution measurements were made at a temperature of 10eV/amu for a series of targets with varying ionization potentials. The Ne10+ data clearly shows the contribution from multiple capture followed by Auger autoionization in the line emission spectra. Our calculated line emission cross sections are used to provide an ab initio determination of the soft x-ray spectrum of comet C/Linear 1999 S4 that was observed on the Chandra X-ray Observatory. The calculations show that the spectrum is due to the charge exchange of the neutral gases in the comet’s coma with the ions of the slow solar wind.

Otranto, S.; Olson, R. E.; Beiersdorfer, P.

2006-02-01

307

Continuous Emission of X-rays by Thermal Excitation of Six LiTaO3 Single Crystals  

NASA Astrophysics Data System (ADS)

The X-ray emission method using a pyroelectric crystal has intermittent emission and intensity is low. In order to achieve the continuous emission of X-rays, six LiTaO3 single crystals are used. Furthermore, in order to investigate the emission of electrons by the interaction between the case material of an X-ray source and emitted X-rays, the case material with different work function or fluorescence yield, such as oxygen-free copper, stainless steel or aluminium, is used. It was found that the intensity of X-rays was depended on case material and it became high with decreasing the fluorescence yield of the case material. It was suggested that a part of emitted electrons were by the Auger process.

Honda, Hiroyuki; Fukao, Shinji; Guan, Yang; Nakanishi, Yoshikazu; Sato, Yuuki; Ito, Yoshiaki; Yoshikado, Shinzo

2011-10-01

308

A von Hamos x-ray spectrometer based on a segmented-type diffraction crystal for single-shot x-ray emission spectroscopy and time-resolved resonant inelastic x-ray scattering studies  

SciTech Connect

We report on the design and performance of a wavelength-dispersive type spectrometer based on the von Hamos geometry. The spectrometer is equipped with a segmented-type crystal for x-ray diffraction and provides an energy resolution in the order of 0.25 eV and 1 eV over an energy range of 8000 eV-9600 eV. The use of a segmented crystal results in a simple and straightforward crystal preparation that allows to preserve the spectrometer resolution and spectrometer efficiency. Application of the spectrometer for time-resolved resonant inelastic x-ray scattering and single-shot x-ray emission spectroscopy is demonstrated.

Szlachetko, J. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Institute of Physics, Jan Kochanowski University, 25-406 Kielce (Poland); Nachtegaal, M.; Boni, E. de; Willimann, M.; Safonova, O.; Sa, J.; Smolentsev, G.; Szlachetko, M.; Bergamaschi, A.; Schmitt, B.; David, C.; Luecke, A. [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Bokhoven, J. A. van [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Institute for Chemical and Bioengineering, ETH Zurich, 8093 Zuerich (Switzerland); Dousse, J.-Cl.; Hoszowska, J.; Kayser, Y. [Department of Physics, University of Fribourg, 1700 Fribourg (Switzerland); Jagodzinski, P. [University of Technology, Kielce (Poland)

2012-10-15

309

Diffuse Hard X-Ray Emission in Starburst Galaxies as Synchrotron from Very High Energy Electrons  

NASA Astrophysics Data System (ADS)

The origin of the diffuse hard X-ray (2-10 keV) emission from starburst galaxies is a long-standing problem. We suggest that synchrotron emission of 10-100 TeV electrons and positrons (e ±) can contribute to this emission, because starbursts have strong magnetic fields. We consider three sources of e ± at these energies: (1) primary electrons directly accelerated by supernova remnants, (2) pionic secondary e ± created by inelastic collisions between cosmic ray (CR) protons and gas nuclei in the dense interstellar medium of starbursts, and (3) pair e ± produced between the interactions between 10 and 100 TeV ?-rays and the intense far-infrared (FIR) radiation fields of starbursts. We create one-zone steady-state models of the CR population in the Galactic center (R <= 112 pc), NGC 253, M82, and Arp 220's nuclei, assuming a power-law injection spectrum for electrons and protons. We consider different injection spectral slopes, magnetic field strengths, CR acceleration efficiencies, and diffusive escape times, and include advective escape, radiative cooling processes, and secondary and pair e ±. We compare these models to extant radio and GeV and TeV ?-ray data for these starbursts, and calculate the diffuse synchrotron X-ray and inverse Compton (IC) luminosities of these starbursts in the models which satisfy multiwavelength constraints. If the primary electron spectrum extends to ~PeV energies and has a proton/electron injection ratio similar to the Galactic value, we find that synchrotron emission contributes 2%-20% of their unresolved, diffuse hard X-ray emission. However, there is great uncertainty in this conclusion because of the limited information on the CR electron spectrum at these high energies. IC emission is likewise a minority of the unresolved X-ray emission in these starbursts, from 0.1% in the Galactic center to 10% in Arp 220's nuclei, with the main uncertainty being the starbursts' magnetic field. We also model generic starbursts, including submillimeter galaxies, in the context of the FIR-X-ray relation, finding that anywhere between 0% and 16% of the total hard X-ray emission is synchrotron for different parameters, and up to 2% in the densest starbursts assuming an E -2.2 injection spectrum and a diffusive escape time of 10 Myr (E/3 GeV)-1/2 (h/100 pc). Neutrino observations by IceCube and TeV ?-ray data from HESS, VERITAS, and CTA can further constrain the synchrotron X-ray emission of starbursts. Our models do not constrain the possibility of hard, second components of primary e ± from sources like pulsars in starbursts, which could enhance the synchrotron X-ray emission further.

Lacki, Brian C.; Thompson, Todd A.

2013-01-01

310

Wavelength dispersive soft X-ray emission spectroscopy attached to TEM using multi-capirary X-ray lens  

Microsoft Academic Search

There is now growing interest in localized chemical bonding states in complex metals and insulators such as those containing\\u000a light elements, rare earths or transition metals because their key spectral features appear in the soft X-ray or vacuum UV\\u000a regions, which is not easily accessible to by SOR light sources and often includes crucial information to understand their\\u000a electronic, optical,

S. Muto; K. Tatsumi; H. Takahashi

311

Chandra X-Ray Grating Spectrometry of ? Carinae near X-Ray Minimum. I. Variability of the Sulfur and Silicon Emission Lines  

NASA Astrophysics Data System (ADS)

We report on variations in important X-ray emission lines in a series of Chandra grating spectra of the supermassive colliding wind binary star ? Car, including key phases around the X-ray minimum/periastron passage in 2003.5. The X-rays arise from the collision of the slow, dense wind of ? Car with the fast, low-density wind of an otherwise hidden companion star. The X-ray emission lines provide the only direct measure of the flow dynamics of the companion's wind along the wind-wind collision zone. We concentrate here on the silicon and sulfur lines, which are the strongest and best-resolved lines in the X-ray spectra. Most of the line profiles can be adequately fit with symmetric Gaussians with little significant skewness. Both the silicon and sulfur lines show significant velocity shifts and correlated increases in line widths through the observations. The R = forbidden-to-intercombination ratio from the Si XIII and S XV triplets is near or above the low-density limit in all observations, suggesting that the line-forming region is >1.6 stellar radii from the companion star. We show that simple geometrical models cannot simultaneously fit both the observed centroid variations and changes in line width as a function of phase. We show that the observed profiles can be fitted with synthetic profiles with a reasonable model of the emissivity along the wind-wind collision boundary. We use this analysis to help constrain the line formation region as a function of orbital phase, and the orbital geometry.

Henley, D. B.; Corcoran, M. F.; Pittard, J. M.; Stevens, I. R.; Hamaguchi, K.; Gull, T. R.

2008-06-01

312

A Multiwavelength Exploration of the Grand Design Spiral M83: Diffuse X-ray Emission  

NASA Astrophysics Data System (ADS)

We have obtained a series of deep X-ray images of the nearby galaxy M83, with a total exposure 729 ksec with the Chandra ACIS-S array. Since the bulk of the X-ray emitting disk falls within the BI chip, these observations allow a detailed study of the soft diffuse emission in the disk. Most of the diffuse emission is related to star-formation regions and must be powered by supernovae and stellar winds, though the amount of emission due to identifiable SNR is only a few percent. The relation between the spectral shape and surface brightness that was seen in M101 suggests that the properties of the X-ray emission in spiral disks are shaped by the local hot gas production rate (traced by the local star-formation rate) or the disk mid-plane pressure, but it is unclear which physical mechanism dominates. To illuminate this problem, we will compare M83 with the previous Chandra studies of M101 and M33.

Kuntz, K. D.; Long, K. S.; Blair, W. P.; Plucinsky, P. P.; Soria, R.; Winkler, P. F.

2013-01-01

313

Loop-Top Hard X-Ray Emission from Impulsive Solar Flares  

NASA Astrophysics Data System (ADS)

One of the most curious discoveries to come from the Yohkoh mission is the observation of hard X-ray emission from the top of some impulsive flare coronal loops. Typically, hard X-ray emission is seen from the loop footpoints, where the ambient density is relatively high; how such emission can emanate from the top of a loop, where the plasma density is low, is a fundamental question in impulsive flare acceleration theory. We will present an improvement of an electron acceleration model that employs transit-time damping of fast mode MHD waves, and which naturally yields enhanced electron acceleration (and thus hard X-ray emission) away from the loop footpoints. Furthermore, this enhancement is exacerbated by partial magnetic mirroring, which would result from any compression of the coronal magnetic field. The time- and spatially-dependent electron distribution is determined by a quasilinear diffusion equation, which we solve using a Monte Carlo simulation and the novel technique of stochastic differential equations. BEM and MEO are supported by an NSF REU Grant ATM 9820339; JAM supported by NASA SEC Solar Physics grant NAG5-9598.

Marsteller, B. E.; Orr, E.; Miller, J. A.

2001-05-01

314

The X-Ray Line Emission from the Supernova Remnant W49B  

NASA Astrophysics Data System (ADS)

The Galactic supernova remnant W49B has one of the most impressive X-ray emission-line spectra obtained with ASCA. We use both plasma line diagnostics and broadband model fits to show that the Si and S emission lines require multiple spectral components. The spectral data do not necessarily require individual elements to be spatially stratified, as suggested by earlier work, although when ASCA line images are considered, it is possible that Fe is stratified with respect to Si and S. Most of the X-ray-emitting gas is from ejecta, based on the element abundances required, but is surprisingly close to being in collisional ionization equilibrium. A high ionization age implies a high internal density in a young remnant. The fitted emission measure for W49B indicates a minimum density of 2 cm-3, with the true density likely to be significantly higher. W49B probably had a Type Ia progenitor, based on the relative element abundances, although a low-mass Type II progenitor is still possible. We find persuasive evidence for Cr and possibly Mn emission in the ASCA spectrum-the first detection of these elements in X-rays from a cosmic source.

Hwang, Una; Petre, Robert; Hughes, John P.

2000-04-01

315

Angular Distribution of Argon Ions and X-Ray Emissions in the Apf Plasma Focus Device  

NASA Astrophysics Data System (ADS)

Angular distribution of ion beam emission from an argon gas-filled plasma focus devices has been investigated using an array of five Faraday cups. The argon ion beam emission is found to be highly pressure-dependent and reaches its maximum at the pressure of 1 torr. The ions flux decreased as the working pressure increased; the maximum ion density at 1 torr was estimated to be around 9.24 × 1024 ions/steradian. Also, the study on the angular distribution of X-rays has been carried out using TLD-100 dosimeters. The intensity of ions reduced significantly at angles higher than ±11° but the X-ray distribution was bimodal, peaked approximately at ±15°.

Etaati, G. R.; Amrollahi, R.; Habibi, M.; Baghdadi, R.

2011-04-01

316

Search for X-ray emission from subdwarf B stars with compact companion candidates  

NASA Astrophysics Data System (ADS)

Stellar evolutionary models predict that most early-type subdwarf stars in close binary systems have white dwarf companions. More massive companions, such as neutron stars or black holes, are also expected in some cases. Compact stars in these systems can be detected by means of X-rays powered by either accretion of the subdwarf stellar wind or surface thermal emission. Using the Swift satellite, we carried out a systematic search for X-ray emission from twelve subdwarf B stars that, based on optical studies, appear to have degenerate companions. None of our targets were detected, but the derived upper limits provide one of the few observational constraints on the stellar winds of early-type subdwarfs. Our results constrain the mass loss rates of some of these subdwarf B stars to values ?W < 10-13-10-12 M? yr-1, if indeed they have neutron star companions.

Mereghetti, S.; Campana, S.; Esposito, P.; La Palombara, N.; Tiengo, A.

2011-12-01

317

SUPERORBITAL MODULATION OF X-RAY EMISSION FROM GAMMA-RAY BINARY LSI +61 303  

SciTech Connect

We report the discovery of a systematic constant time lag between the X-ray and radio flares of the gamma-ray binary LSI +61 303, persistent over a long, multi-year timescale. Using the data from the monitoring of the system by RXTE we show that the orbital phase of X-ray flares from the source varies from {phi}{sub X} {approx_equal} 0.35 to {phi}{sub X} {approx_equal} 0.75 on the superorbital 4.6 yr timescale. Simultaneous radio observations show that periodic radio flares always lag the X-ray flare by {Delta}{phi}{sub X-R} {approx_equal} 0.2. We propose that the constant phase lag corresponds to the time of flight of the high-energy particle-filled plasma blobs from inside the binary to the radio emission region at the distance of {approx}10 times the binary separation distance. We put forward a hypothesis that the X-ray bursts correspond to the moments of formation of plasma blobs inside the binary system.

Chernyakova, M. [School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9 (Ireland); Neronov, A. [ISDC Data Center for Astrophysics, Chemin d'Ecogia 16, 1290 Versoix (Switzerland); Molkov, S.; Lutovinov, A. [Space Research Institute (IKI), 84/32 Profsoyuznaya Str., Moscow 117997 (Russian Federation); Malyshev, D. [Bogolyubov Institute for Theoretical Physics, 14-b Metrolohichna Street, Kiev 03680 (Ukraine); Pooley, G. [Astrophysics, Cavendish Laboratory, Cambridge CB3 0HE (United Kingdom)

2012-03-10

318

Modeling the Role of Charge Exchange in X-ray Emission Spectra  

NASA Astrophysics Data System (ADS)

Most of the gas in the Universe is not in thermal equilibrium requiring some type of collisional non-equilibrium model for accurate interpretation of observations. When ions and neutrals are present, charge exchange (CX) is one process that can occur which plays a role in the ionization balance and may dominate the ion emission spectra, such as in the solar wind charge exchange (SWCX) mechanism. In the SWCX mechanism, a SW ion captures an electron from a heliospheric or atmospheric neutral atom creating a highly excited ion which subsequently emits one or more x-rays in a cascade to the ground state. To improve SWCX x-ray models, CX computations of the dominant SW ions colliding with neutral targets have been performed. Using the CX cross sections, x-ray spectra and hardness ratios have been calculated for collisions of a range of ions with H and He. The relevance of the spectra models to heliospheric and astrophysical environments will be discussed. This work was partially supported by NASA grants NNX09AC46G and NNG09WF24I. Synopsis: Charge exchange cross sections are used to produce x-ray spectra and hardness ratios for collisions including H and He as target ions.

Cumbee, Renata; Lyons, D.; Stancil, P. C.; Rakovic, M. J.; Schultz, D. R.

2013-01-01

319

The dust emission SED of X-ray emitting regions in Stephan's Quintet  

NASA Astrophysics Data System (ADS)

We analysed the Spitzer maps of Stephan's Quintet in order to investigate the nature of the dust emission associated with the X-ray emitting regions of the large scale intergalactic shock and of the group halo. This emission can in principle be powered by dust-gas particle collisions, thus providing efficient cooling of the hot gas. However the results of our analysis suggest that the dust emission from those regions is mostly powered by photons. Nonetheless dust collisional heating could be important in determining the cooling of the IGM gas and the large scale star formation morphology observed in SQ.

Natale, G.; Tuffs, R. J.; Xu, C. K.; Popescu, C. C.; Fischera, J.; Lisenfeld, U.; Lu, N.; Appleton, P.; Dopita, M.; Duc, P.-A.; Gao, Y.; Reach, W.; Sulentic, J.; Yun, M.

2012-08-01

320

Depth-resolved soft x-ray photoelectron emission microscopy in nanostructures via standing-wave excited photoemission  

SciTech Connect

We present an extension of conventional laterally resolved soft x-ray photoelectron emission microscopy. A depth resolution along the surface normal down to a few {angstrom} can be achieved by setting up standing x-ray wave fields in a multilayer substrate. The sample is an Ag/Co/Au trilayer, whose first layer has a wedge profile, grown on a Si/MoSi2 multilayer mirror. Tuning the incident x-ray to the mirror Bragg angle we set up standing x-ray wave fields. We demonstrate the resulting depth resolution by imaging the standing wave fields as they move through the trilayer wedge structure.

Kronast, F.; Ovsyannikov, R.; Kaiser, A.; Wiemann, C.; Yang, S.-H.; Locatelli, A.; Burgler, D.E.; Schreiber, R.; Salmassi, F.; Fischer, P.; Durr, H.A.; Schneider, C.M.; Eberhardt, W.; Fadley, C.S.

2008-11-24

321

Solar Control on Jupiter's Equatorial X-ray Emissions: 26-29 November 2003 XMM-Newton Observation  

Microsoft Academic Search

During November 26-29, 2003 XMM-Newton observed soft (0.2-2 keV) X-ray\\u000aemission from Jupiter for 69 hours. The low-latitude X-ray disk emission of\\u000aJupiter is observed to be almost uniform in intensity with brightness that is\\u000aconsistent with a solar-photon driven process. The simultaneous lightcurves of\\u000aJovian equatorial X-rays and solar X-rays (measured by the TIMED\\/SEE and GOES\\u000asatellites) show similar

Anil Bhardwaj; Graziella Branduardi-Raymont; Ronald F. Elsner; G. Randall Gladstone; Gavin Ramsay; Pedro Rodriguez; Roberto Soria; J. Hunter Waite Jr.; Thomas E. Cravens

2005-01-01

322

Dissipation of potential energy through x-ray emission in slow highly charged ion-surface collisions  

NASA Astrophysics Data System (ADS)

X-ray emission yields from highly charged iodine ions incident on a hydrogen terminated silicon surface were measured. It was found that the K shell vacancies were filled through x-ray transitions with the probability of approximately 100%, while only about 20% of L shell vacancies were filled through x-ray transitions and almost all the M shell vacancies were filled nonradiatively. Dissipation of the potential energy Ep of an incident ion through x-ray emissions increases gradually with the number of L shell vacancies and amounts to 10% of Ep for the He-like I51+ ion. 30 to 40 % of Ep for I52+ and I53+ with K shell vacancies was measured to be dissipated mainly by K x-ray emissions.

Watanabe, H.; Takahashi, S.; Tona, M.; Yoshiyasu, N.; Nakamura, N.; Sakurai, M.; Yamada, C.; Ohtani, S.

2006-10-01

323

X-ray emission from plasmas created by smoothed KrF laser irradiation  

Microsoft Academic Search

The x-ray emission from plasmas created by the Naval Research Laboratory Nike KrF laser [Phys. Plasmas 3, 2098 (1996) ] was characterized using imaging and spectroscopic instruments. The laser wavelength was 1\\/4 ?m, and the beams were smoothed by induced spatial incoherence (ISI). The targets were thin foils of CH, aluminum, titanium, and cobalt and were irradiated by laser energies

Y. Aglitskiy; T. Lehecka; A. Deniz; J. Hardgrove; J. Seely; C. Brown; U. Feldman; C. Pawley; K. Gerber; S. Bodner; S. Obenschain; R. Lehmberg; E. McLean; M. Pronko; J. Sethian; A. Schmitt; C. Sullivan; G. Holland; M. Laming

1996-01-01

324

Hydrostatic Modelling of Active Region EUV and X-ray Emission  

Microsoft Academic Search

The hydrostatic modeling of active region NOAA 10963 coronal EUV and X-ray emission is presented. The model considers three-dimensional magnetic field structure obtained by the extraplation of the longitudinal magnetogram in potential or linear force-free approximation. We derived new scaling laws for loop apex temperature and footpoint pressure as functions of loop length, volumetric heating rate and heating scale height.

J. Dudik; E. Dzifcakova; A. Kulinova; M. Karlicky

2008-01-01

325

X-ray emission study of the electronic structure of nanocrystalline Al 2 O 3  

Microsoft Academic Search

Valence states of metal ions and the phase composition of nanocrystalline Al2O3 (of the original oxide and the oxide irradiated by high-energy Fe+ ions) are studied by using x-ray emission Al L\\u000a 2, 3 and O K? spectra. It is established that the shape of the Al L\\u000a 2, 3 spectra strongly changes as one goes from the original (bulk)

D. A. Zatsepin; V. M. Cherkashenko; É. Z. Kurmaev; S. N. Shamin; V. V. Fedorenko; N. A. Skorikov; S. V. Plastinin; N. V. Gavrilov; A. I. Medvedev; S. O. Cholakh

2004-01-01

326

Performance of soft X-ray emission spectrometer employing charge-coupled device detector  

Microsoft Academic Search

The performance of a soft X-ray emission spectrometer employing a charge-coupled device camera was examined in the energy range of 80–1250eV. The spectra observed by low-energy electron irradiation for metal L, oxygen K and silicon L lines were in good agreement with the previous observations by conventional MCP detectors. The results suggest that the energy resolution is good enough for

T. A. Sasaki; N. Chugan; Y. Muramatsu

2001-01-01

327

X-ray emission from the magnetic star alpha ^2 Canum Venaticorum ?  

Microsoft Academic Search

We propose a 15 ksec pilot study with Chandra ACIS-S of the visual binary system alpha^2 CVn (= HR~4915 and HR~4914). With an angular separation of ˜ 21.3 arcsec this system can be easily resolved with Chandra. X-ray emission from alpha^2 CVn has been detected with the Einstein Observatory IPC and in the ROSAT RASS data, however, the angular resolution

J. Rgen Schmitt

2008-01-01

328

Structure of the sulfur K x-ray emission spectrum: influence of the oxidation state  

Microsoft Academic Search

The sulfur K x-ray emission was studied in pure sulfur, anhydrite (CaSO4) and sphalerite (ZnS) samples. The ionizations were induced by electron impact and the spectra were recorded with a wavelength dispersive spectrometer. The spectral processing was performed through a methodology based on the optimization of atomic and experimental parameters. Energies and intensities of diagram and satellite lines were determined

P D Pérez; A C Carreras; J C Trincavelli

2012-01-01

329

Discovery of Radio Emission From Transient Anomalous X-Ray Pulsar XTE J1810-197  

Microsoft Academic Search

We report the first detection of radio emission from any anomalous X-ray pulsar (AXP). Data from the Very Large Array (VLA) MAGPIS survey with angular resolution 6'' reveals a point-source of flux density 4.5 {+-} 0.5 mJy at 1.4 GHz at the precise location of the 5.54 s pulsar XTE J1810-197. This is greater than upper limits from all other

J. P. Halpern; E. V. Gotthelf; R. H. Becker; D. J. Helfand; R. L. White

2005-01-01

330

Demonstration of whole blood analysis using proton-induced x-ray emission.  

PubMed

The elemental variations in whole blood following gamma-radiation injury of mice have been studied. the trace-element analyses were performed using the proton-induced x-ray emission technique, and the results were compared with the red blood-cell count. It is shown that, by using this method, the variation of the six elements, K, Ca, Fe, Cu, Zn, and Rb, can be studied simultaneously. PMID:1264045

Malanify, J J; Burns, C E; Close, D A; Bearse, R C

331

First-principles Calculation of Resonant X-ray Emission Spectra Applied to ZnO  

SciTech Connect

A framework for calculating the k-conserving component of K edge resonant x-ray emission spectroscopy measurements of anisotropic solids is presented. The crystalline band structure is calculated using a quasiparticle self-consistent GW implementation. Coherent spectra are calculated in the Kramers-Heisenberg formalism, and the effect of the experimental geometry in the dipole approximation is fully considered. Coherent spectra are calculated for ZnO and successfully compared to previously measured data.

A Preston; A DeMasi; L Piper; K Smith; W Lambrecht; A Boonchun; T Cheiwchanchamnangij; J Arnemann; V van Schlifgaarde; B Ruck

2011-12-31

332

Triple-path collector optics for grazing incident x-ray emission spectrometer  

NASA Astrophysics Data System (ADS)

A new type of collector optics was developed for grazing incident x-ray emission spectrometer. The collector optics used two cylindrical mirrors to add two extra light paths while keeping the center light path that directly illuminates the grating. The design and properties of the spectrometer using the triple-path collector optics were evaluated using ray-tracing simulations, and validity of this design in terms of throughput and energy resolution was confirmed by the experimentally obtained spectra.

Tokushima, T.; Horikawa, Y.; Shin, S.

2011-07-01

333

Bulk band gaps in divalent hexaborides: A soft x-ray emission study  

SciTech Connect

Boron K-edge soft x-ray emission and absorption are used to address the fundamental question of whether divalent hexaborides are intrinsic semimetals or defect-doped bandgap insulators. These bulk sensitive measurements, complementary and consistent with surface-sensitive angle-resolved photoemission experiments, confirm the existence of a bulk band gap and the location of the chemical potential at the bottom of the conduction band.

Denlinger, Jonathan D.; Gweon, Gey-Hong; Allen, James W.; Bianchi, Andrea D.; Fisk, Zachary

2001-10-03

334

Soft-x-ray-emission spectra of solid Kr and Xe  

Microsoft Academic Search

We present the first soft x-ray-emission spectra for solid Kr (4{ital p}-3{ital d}) and Xe (5{ital p}-4{ital d}) that are free of complicating satellite spectra. Monochromatic synchrotron-radiation excitation is used to suppress the satellites. The data are analyzed to determine the {ital P}ââ bandwidth for both elements; these results are compared with both photoemission data and available theoretical calculations. Bandwidths

J. J. Jia; W. L. OBrien; T. A. Callcott; Q. Y. Dong; J. E. Rubensson; D. R. Mueller; D. L. Ederer

1991-01-01

335

Soft-x-ray-emission spectra of solid Kr and Xe  

Microsoft Academic Search

We present the first soft x-ray-emission spectra for solid Kr (4p-3d) and Xe (5p-4d) that are free of complicating satellite spectra. Monochromatic synchrotron-radiation excitation is used to suppress the satellites. The data are analyzed to determine the P3\\/2 bandwidth for both elements; these results are compared with both photoemission data and available theoretical calculations. Bandwidths are found to be larger

J. J. Jia; W. L. O'brien; T. A. Callcott; Q. Y. Dong; J.-E. Rubensson; D. R. Mueller; D. L. Ederer

1991-01-01

336

Suzaku observations of X-ray excess emission in the cluster of galaxies A 3112  

NASA Astrophysics Data System (ADS)

Aims: We analysed the Suzaku XIS1 data of the A 3112 cluster of galaxies in order to examine the X-ray excess emission in this cluster reported earlier with the XMM-Newton and Chandra satellites. Methods: We performed X-ray spectroscopy on the data of a single large region. We carried out simulations to estimate the systematic uncertainties affecting the X-ray excess signal. Results: The best-fit temperature of the intracluster gas depends strongly on the choice of the energy band used for the spectral analysis. This proves the existence of excess emission component in addition to the single-temperature MEKAL in A 3112. We showed that this effect is not an artifact due to uncertainties of the background modeling, instrument calibration or the amount of Galactic absorption. Neither does the PSF scatter of the emission from the cool core nor the projection of the cool gas in the cluster outskirts produce the effect. Finally we modeled the excess emission either by using an additional MEKAL or powerlaw component. Due to the small differencies between thermal and non-thermal model we can not rule out the non-thermal origin of the excess emission based on the goodness of the fit. Assuming that it has a thermal origin, we further examined the differential emission measure (DEM) models. We utilised two different DEM models, a Gaussian differential emission measure distribution (GDEM) and WDEM model, where the emission measure of a number of thermal components is distributed as a truncated power law. The best-fit XIS1 MEKAL temperature for the 0.4-7.0 keV band is 4.7 ± 0.1 keV, consistent with that obtained using GDEM and WDEM models.

Lehto, T.; Nevalainen, J.; Bonamente, M.; Ota, N.; Kaastra, J.

2010-12-01

337

Studying the relationship between X-ray emission and accretion in AGN using the XMM-Newton Bright Serendipitous Survey  

NASA Astrophysics Data System (ADS)

We study the link between the X-ray emission in radio-quiet active galactic nuclei (AGN) and the accretion rate on the central supermassive black hole using a statistically well-defined and representative sample of 71 type 1 AGN extracted from the XMM-Newton Bright Serendipitous Survey. We search and quantify the statistical correlations between some fundamental parameters that characterize the X-ray emission, i.e. the X-ray spectral slope, ?, and the X-ray `loudness', and the accretion rate, both absolute (?) and normalized to the Eddington luminosity (Eddington ratio, ?). We parametrize the X-ray loudness using three different quantities: the bolometric correction Kbol, the two-point spectral index ?OX and the disc/corona luminosity ratio. We find that the X-ray spectral index depends on the normalized accretion rate while the `X-ray loudness' depends on both the normalized and the absolute accretion rate. The dependence on the Eddington ratio, in particular, is probably induced by the ? - ? correlation. The two proxies usually adopted in the literature to quantify the X-ray loudness of an AGN, i.e. Kbol and ?OX, behave differently, with Kbol being more sensitive to the Eddington ratio and ?OX having a stronger dependence with the absolute accretion. The explanation of this result is likely related to the different sensitivity of the two parameters to the X-ray spectral index.

Fanali, R.; Caccianiga, A.; Severgnini, P.; Della Ceca, R.; Marchese, E.; Carrera, F. J.; Corral, A.; Mateos, S.

2013-07-01

338

X-ray photo-emission and energy dispersive spectroscopy of HA coated titanium  

SciTech Connect

The purpose of this study was to determine the chemical composition changes of hydroxyapatite (HA) coated titanium using surface analysis (x-ray photo-emission) and bulk analysis (energy dispersive spectroscopy). The specimens examined were controls, 30 minutes and 3 hours aged specimens in distilled water or 0.2M sodium phosphate buffer (pH 7.2) at room temperature. Each x-ray photo-emission cycle consisted of 3 scans followed by argon sputtering for 10 minutes for a total of usually 20 cycles, corresponding to a sampling depth of {approximately} 1500 {angstrom}. The energy dispersive spectroscopy analysis was on a 110 by 90 {mu}m area for 500 sec. Scanning electron microscopy examination showed crystal formation (3P{sub 2}O{sub 5}*2CAO*?H{sub 2}O by energy dispersive spectroscopy analysis) on the HA coating for the specimens aged in sodium phosphate buffer. The x-ray photo-emission results indicated the oxidation effect of water on the titanium (as TiO{sub 2}) and the effect of the buffer to increase the surface concentration of phosphorous. No differences in the chemical composition were observed by energy dispersive spectroscopy analysis. The crystal growth was only observed for the sodium phosphate buffer specimens and only on the HA surface.

Drummond, J.L.; Steinberg, A.D. [Univ. of Illinois, Chicago, IL (United States); Krauss, A.R. [Argonne National Lab., IL (United States)] [and others

1997-08-01

339

Theoretically predicted soft X-ray emission and absorption spectra of fullerene-like carbon nitride (C 24N 36)  

Microsoft Academic Search

Theoretical C K and N K X-ray emission\\/absorption spectra of fullerene-like-structured carbon nitride (C24N36) clusters were obtained using discrete-variational (DV)-X? molecular orbital calculations. These calculations predicted that the energy widths of the C K and N K X-ray emission peaks would be about 8 and 6 eV, respectively; three low-energy satellites would appear in each emission spectrum; and there would

Yasuji Muramatsu; Takayoshi Hayashi; Rupert C. C. Perera

1999-01-01

340

INVERSE COMPTON X-RAY EMISSION FROM SUPERNOVAE WITH COMPACT PROGENITORS: APPLICATION TO SN2011fe  

SciTech Connect

We present a generalized analytic formalism for the inverse Compton X-ray emission from hydrogen-poor supernovae and apply this framework to SN 2011fe using Swift X-Ray Telescope (XRT), UVOT, and Chandra observations. We characterize the optical properties of SN 2011fe in the Swift bands and find them to be broadly consistent with a 'normal' SN Ia, however, no X-ray source is detected by either XRT or Chandra. We constrain the progenitor system mass-loss rate M-dot < 2 x 10{sup -9} M{sub Sun }yr{sup -1} (3{sigma} c.l.) for wind velocity v{sub w} = 100 km s{sup -1}. Our result rules out symbiotic binary progenitors for SN 2011fe and argues against Roche lobe overflowing subgiants and main-sequence secondary stars if {approx}> 1% of the transferred mass is lost at the Lagrangian points. Regardless of the density profile, the X-ray non-detections are suggestive of a clean environment (n{sub CSM} < 150 cm{sup -3}) for 2 Multiplication-Sign 10{sup 15} {approx}< R {approx}< 5 Multiplication-Sign 10{sup 16} cm around the progenitor site. This is either consistent with the bulk of material being confined within the binary system or with a significant delay between mass loss and supernova explosion. We furthermore combine X-ray and radio limits from Chomiuk et al. to constrain the post-shock energy density in magnetic fields. Finally, we searched for the shock breakout pulse using gamma-ray observations from the Interplanetary Network and find no compelling evidence for a supernova-associated burst. Based on the compact radius of the progenitor star we estimate that the shock breakout pulse was likely not detectable by current satellites.

Margutti, R.; Soderberg, A. M.; Chomiuk, L.; Milisavljevic, D.; Foley, R. J.; Slane, P.; Moe, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Chevalier, R. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Hurley, K. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Hughes, J. P. [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854-8019 (United States); Fransson, C. [Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); Barthelmy, S.; Cummings, J. [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Boynton, W.; Enos, H.; Fellows, C. [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States); Briggs, M.; Connaughton, V. [Physics Department, The University of Alabama in Huntsville, Huntsville, AL 35809 (United States); Costa, E.; Del Monte, E. [INAF/IASF-Roma, via Fosso del Cavaliere 100, 00133 Roma (Italy); and others

2012-06-01

341

Inverse Compton X-Ray Emission from Supernovae with Compact Progenitors: Application to SN2011fe  

NASA Astrophysics Data System (ADS)

We present a generalized analytic formalism for the inverse Compton X-ray emission from hydrogen-poor supernovae and apply this framework to SN 2011fe using Swift X-Ray Telescope (XRT), UVOT, and Chandra observations. We characterize the optical properties of SN 2011fe in the Swift bands and find them to be broadly consistent with a "normal" SN Ia, however, no X-ray source is detected by either XRT or Chandra. We constrain the progenitor system mass-loss rate \\dot{M}< 2\\times 10^{-9}\\ {M_{\\odot }}\\ yr^{-1} (3? c.l.) for wind velocity vw = 100 km s-1. Our result rules out symbiotic binary progenitors for SN 2011fe and argues against Roche lobe overflowing subgiants and main-sequence secondary stars if >~ 1% of the transferred mass is lost at the Lagrangian points. Regardless of the density profile, the X-ray non-detections are suggestive of a clean environment (n CSM < 150 cm-3) for 2 × 1015 <~ R <~ 5 × 1016 cm around the progenitor site. This is either consistent with the bulk of material being confined within the binary system or with a significant delay between mass loss and supernova explosion. We furthermore combine X-ray and radio limits from Chomiuk et al. to constrain the post-shock energy density in magnetic fields. Finally, we searched for the shock breakout pulse using gamma-ray observations from the Interplanetary Network and find no compelling evidence for a supernova-associated burst. Based on the compact radius of the progenitor star we estimate that the shock breakout pulse was likely not detectable by current satellites.

Margutti, R.; Soderberg, A. M.; Chomiuk, L.; Chevalier, R.; Hurley, K.; Milisavljevic, D.; Foley, R. J.; Hughes, J. P.; Slane, P.; Fransson, C.; Moe, M.; Barthelmy, S.; Boynton, W.; Briggs, M.; Connaughton, V.; Costa, E.; Cummings, J.; Del Monte, E.; Enos, H.; Fellows, C.; Feroci, M.; Fukazawa, Y.; Gehrels, N.; Goldsten, J.; Golovin, D.; Hanabata, Y.; Harshman, K.; Krimm, H.; Litvak, M. L.; Makishima, K.; Marisaldi, M.; Mitrofanov, I. G.; Murakami, T.; Ohno, M.; Palmer, D. M.; Sanin, A. B.; Starr, R.; Svinkin, D.; Takahashi, T.; Tashiro, M.; Terada, Y.; Yamaoka, K.

2012-06-01

342

X-RAY EMISSION LINE PROFILES FROM WIND CLUMP BOW SHOCKS IN MASSIVE STARS  

SciTech Connect

The consequences of structured flows continue to be a pressing topic in relating spectral data to physical processes occurring in massive star winds. In a preceding paper, our group reported on hydrodynamic simulations of hypersonic flow past a rigid spherical clump to explore the structure of bow shocks that can form around wind clumps. Here we report on profiles of emission lines that arise from such bow shock morphologies. To compute emission line profiles, we adopt a two-component flow structure of wind and clumps using two 'beta' velocity laws. While individual bow shocks tend to generate double-horned emission line profiles, a group of bow shocks can lead to line profiles with a range of shapes with blueshifted peak emission that depends on the degree of X-ray photoabsorption by the interclump wind medium, the number of clump structures in the flow, and the radial distribution of the clumps. Using the two beta law prescription, the theoretical emission measure and temperature distribution throughout the wind can be derived. The emission measure tends to be power law, and the temperature distribution is broad in terms of wind velocity. Although restricted to the case of adiabatic cooling, our models highlight the influence of bow shock effects for hot plasma temperature and emission measure distributions in stellar winds and their impact on X-ray line profile shapes. Previous models have focused on geometrical considerations of the clumps and their distribution in the wind. Our results represent the first time that the temperature distribution of wind clump structures are explicitly and self-consistently accounted for in modeling X-ray line profile shapes for massive stars.

Ignace, R. [Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37614 (United States); Waldron, W. L. [Eureka Scientific Inc., 2452 Delmer Street, Oakland, CA 94602 (United States); Cassinelli, J. P. [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53711 (United States); Burke, A. E., E-mail: ignace@etsu.edu, E-mail: wwaldron@satx.rr.com, E-mail: cassinelli@astro.wisc.edu, E-mail: burke.alexander@gmail.com [990 Washington Street 317, Dedham, MA 02026 (United States)

2012-05-01

343

Analysis of the X-ray emission of nine Swift afterglows  

NASA Astrophysics Data System (ADS)

The X-ray light curves of nine Swift XRT afterglows (050126, 050128, 050219A, 050315, 050318, 050319, 050401, 050408 and 050505) display a complex behaviour: a steep t-3.0+/-0.3 decay until ~400 s, followed by a significantly slower t-0.65+/-0.20 fall-off, which at 0.2-2 day after the burst evolves into a t-1.7+/-0.5 decay. We consider three possible models for the geometry of relativistic blast-waves (spherical outflows, non-spreading jets and spreading jets), two possible dynamical regimes for the forward shock (adiabatic and fully radiative), and we take into account a possible angular structure of the outflow and delayed energy injection in the blast-wave to identify the models which reconcile the X-ray light-curve decay with the slope of the X-ray continuum for each of the above three afterglow phases. By piecing together the various models for each phase in a way that makes physical sense, we identify possible models for the entire X-ray afterglow. The major conclusion of this work is that a long-lived episode of energy injection in the blast-wave, during which the shock energy increases at t1.0+/-0.5, is required for five afterglows and could be at work in the other four as well. For some afterglows, there may be other mechanisms that can explain the t < 400 s fast falling-off X-ray light curve (e.g. the large-angle gamma-ray burst emission), the 400 s to 5 h slow decay (e.g. a structured outflow), or the steepening at 0.2-2 day (e.g. a jet-break, a collimated outflow transiting from a wind with a r-3 radial density profile to a homogeneous or outward-increasing density region). Optical observations in conjunction with the X-ray can distinguish among these various models. Our simple tests allow the determination of the location of the cooling frequency relative to the X-ray domain and, thus, of the index of the electron power-law distribution with energy in the blast-wave. The resulting indices are clearly inconsistent with a universal value.

Panaitescu, A.; Mészáros, P.; Gehrels, N.; Burrows, D.; Nousek, J.

2006-03-01

344

The Galactic Central Diffuse X-Ray Enhancement: A Differential Absorption/Emission Analysis  

NASA Astrophysics Data System (ADS)

The soft X-ray background shows a general enhancement toward the inner region of the Galaxy. But whether this enhancement is a local feature (e.g., a superbubble within a distance of <~200 pc) and/or a phenomenon related to energetic outflows from the Galactic center/bulge remains unclear. Here we report a comparative X-ray emission and absorption study of diffuse hot gas along the sight lines toward 3C 273 and Mrk 421, on and off the enhancement, but at similar Galactic latitudes. The diffuse 3/4 keV emission intensity, as estimated from the ROSAT All Sky Survey, is about 3 times higher toward 3C 273 than toward Mrk 421. Based on archival Chandra grating observations of these two AGNs, we detect X-ray absorption lines (e.g., O VII K?, K?, and O VIII K? transitions at z~0) and find that the mean hot gas thermal and kinematic properties along the two sight lines are significantly different. By subtracting the foreground and background contribution, as determined along the Mrk 421 sight line, we isolate the net X-ray absorption and emission produced by the hot gas associated with the enhancement in the direction of 3C 273. From a joint analysis of these differential data sets, we obtain the temperature, dispersion velocity, and hydrogen column density as 2.0(1.6,2.3)×106 K, 216(104, 480) km s-1, and 2.2(1.4,4.1)×1019 cm-2, respectively (90% confidence intervals), assuming that the gas is approximately isothermal, solar in metal abundances, and equilibrium in collisional ionization. We also constrain the effective line-of-sight extent of the gas to be 3.4(1.0, 10.1) kpc, strongly suggesting that the enhancement most likely represents a Galactic central phenomenon.

Yao, Yangsen; Wang, Q. Daniel

2007-09-01

345

A Differential Absorption/Emission Analysis of the Galactic Central Diffuse X-ray Enhancement  

NASA Astrophysics Data System (ADS)

The soft X-ray background shows a general enhancement toward the inner region of the Galaxy. But whether this enhancement is a local feature (e.g., a superbubble within a distance of 200 pc or a phenomenon related to energetic outflows from the Galactic center/bulge remains unclear. Here we report a comparative X-ray emission and absorption study of diffuse hot gas along the sight lines toward 3C 273 and Mrk 421, on and off the enhancement, but at similar Galactic latitudes. The diffuse 3/4-keV emission intensity, as estimated from the ROSAT All Sky Survey, is about three times higher toward 3C 273 than toward Mrk 421. Based on archival Chandra grating observations of these two AGNs, we detect z 0 X-ray absorption lines (e.g., OVII Kalpha, Kbeta, and OVIII Kalpha transitions) and find that the mean hot gas thermal and kinematic properties along the two sight lines are significantly different. By subtracting the background contribution, as determined along the Mrk 421 sight line, we isolate the net X-ray absorption and emission produced by the hot gas associated with the enhancement in the direction of 3C 273. From a joint analysis of these differential data sets, we obtain the temperature, dispersion velocity, and hydrogen column density as 2.0E6 K, 200 km/s, and 2E19 cm^{-2}, respectively, assuming that the gas is approximately isothermal, solar in metal abundances, and in collisional ionization equilibrium. We also constrain the effective extent of the gas to be 3.4 kpc, strongly suggesting that the enhancement most likely represents a Galactic central phenomenon.

Yao, Yangsen; Wang, Q.

2007-05-01

346

The Bursty Nature of Solar Flare X-Ray Emission. II. The Neupert Effect  

NASA Astrophysics Data System (ADS)

We carry out a novel statistical test of the Neupert effect based on multifractal spectra. The multifractal spectrum is the number distribution of the strengths (i.e., the Hölder exponents) of bursts in a signal. This is tested on simulations and carried out on RHESSI X-ray data from a well observed GOES X4.8 magnitude flare. The multifractal spectra is ideally suited to quantifying the relative smooth and bursty signals typically found in (thermal) soft X-ray and (non-thermal) hard X-ray data of solar flares. We show that light curves from all energies between 3 keV and 25 keV are statistically similar, suggesting that all these signals are dominated by the same (presumably thermal) emission. Emission lying between 25 keV and 100 keV probably contains some contribution from both thermal and non-thermal sources. The multifractal spectrum of a signal and that of its (cumulative) temporal integration are statistically similar (i.e., low residuals upon subtraction), but shifted by one in the peak Hölder exponent. We find the pairs of 3-6 keV and 100-300 keV emissions, the 6-12 keV and 100-300 keV emissions and the 12-25 keV and 100-300 keV emissions are all consistent with the Neupert effect. The best agreement with the Neupert effect is between the 12-25 keV and 100-300 keV pair, although possibly with some secondary source of thermal emission present.

McAteer, R. T. James; Bloomfield, D. Shaun

2013-10-01

347

X-ray Line Emission from Optically-Thick Astrophysical Media  

NASA Astrophysics Data System (ADS)

Radiative transfer effects are capable of producing line spectra that differ markedly from those emitted from an optically-thin medium. Line photons that travel through an optically-thick medium may suffer multiple non-coherent scatterings, which can alter substantially the profiles of the emergent spectrum. Line transfer can also affect the emergent line intensities through destructive processes in which the energy is either re-radiated through other discrete transitions or is used in heating the ambient plasma. There are numerous astrophysical scenarios where transfer of X-ray lines may be relevant, including ionized surface layers of accretion disks, stellar winds in X-ray binaries, outflowing regions in active galactic nuclei, circumstellar environment of cosmic gamma-ray bursts, and even in the intergalactic medium of clusters of galaxies. Here, we focus on three specific transfer problems that are important for modeling and interpreting astrophysical X-ray spectra acquired with the grating spectrometers on board the Chandra and XMM-Newton observatories: (1) Compton scattering of emission lines, (2) fluorescent line emission from L-shell ions, and (3) overlap of two or more lines. We describe the relevant atomic processes, spectroscopic issues, and useful computational methods for solving these types of problems.

Sako, Masao; Watanabe, Shin

2004-10-01

348

Accelerated electrons and hard X-ray emission from X-pinches  

SciTech Connect

The generation of accelerated electrons in the X-pinch minidiode is studied experimentally. It is well known that the explosion of an X-pinch consisting of two or more wires is accompanied by the formation of a minidiode, in which electrons are accelerated. The subsequent slowing down of electrons in the products of wire explosion causes the generation of hard X-ray (HXR) emission with photon energies higher than 10 keV. In this work, the spatial and temporal characteristics of X-pinch HXR emission are studied, the specific features of HXR generation are discussed, and the capability of applying this radiation to point-projection X-ray imaging of various plasma and biological objects is considered. The parameters of the electron beam produced in the X-pinch are measured using a Faraday cup and X-ray diagnostics. The experiments were performed with the XP generator (550 kA, 100 ns) at Cornell University (United States) and the BIN generator (270 kA, 150 ns) at the Lebedev Physical Institute (Russia).

Shelkovenko, T. A.; Pikuz, S. A.; Mingaleev, A. R.; Agafonov, A. V.; Romanova, V. M.; Ter-Oganes'yan, A. E.; Tkachenko, S. I. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Blesener, I. C.; Mitchell, M. D.; Chandler, K. M.; Kusse, B. R.; Hammer, D. A. [Cornell University (United States)

2008-09-15

349

Determination of the X-ray reflection emissivity profile of 1H 0707-495  

NASA Astrophysics Data System (ADS)

When considering the X-ray spectrum resulting from the reflection off the surface of accretion discs of AGN, it is necessary to account for the variation in reflected flux over the disc, i.e. the emissivity profile. This will depend on factors including the location and geometry of the X-ray source and the disc characteristics. We directly obtain the emissivity profile of the disc from the observed spectrum by considering the reflection component as the sum of contributions from successive radii in the disc and fitting to find the relative weightings of these components in a relativistically broadened emission line. This method has successfully recovered known emissivity profiles from synthetic spectra and is applied to XMM-Newton spectra of the Narrow Line Seyfert 1 galaxy 1H 0707-495. The data imply a twice-broken power-law form of the emissivity law with a steep profile in the inner regions of the disc (index 7.8) and then a flat region between 5.6 and 34.8rg before tending to a constant index of 3.3 over the outer regions of the disc. The form of the observed emissivity profile is consistent with theoretical predictions, thus reinforcing the reflection interpretation.

Wilkins, D. R.; Fabian, A. C.

2011-06-01

350

X-ray and gamma-ray emissions from galactic black hole candidates: Observations and analysis  

NASA Astrophysics Data System (ADS)

Though it has been more than 30 years since the first discovery of the classic Galactic black hole candidate (GBHC) Cygnus X-1, the X-ray emission mechanisms of GBHCs are still not well understood. It is generally agreed that black holes accrete materials from nearby objects or media to form accretion disks around them. The accretion disks can be heated up to a temperature above 1 keV. Such a hot disk emits X- and Gamma-rays, observations of which are essential for understanding the accreting and heating processes. Our multi-wavelength observations of GRS 1758-258 (a GBHC) in August 1997 revealed several properties that are important for constraining the emission model and the geometry of the accretion disk. (1)Its spectrum does not have a significant soft component. This implies that the cold optically thick disk must be small or be mostly covered by a optically thin hot corona. (2)The spectrum has an exponential cutoff around 200 keV, which means that the hot corona is largely thermal. (3)No significant iron lines are detected. This suggests that the reprocessing of the X-ray by the cold disk is negligible. We systematically analyzed RXTE archival data to study the energy dependency of the variability of X-ray flux from four hard X-ray sources: Cygnus X-1, GX 339-4, GRS 1758-258 and 1E 1740.7-2942. Cygnus X-1 was found to have flatter power density spectrum (PDS) shapes at higher energies, while the other three have energy independent PDS shapes. No current models can fully explain these results. A general trend was found among the four sources that the variability anti-correlates with the X-ray flux. We found that the 0.5-10 Hz quasi-periodic oscillations (QPOs) observed in GRS 1915+105 (a GBHC) has peculiar phase lag behaviors. When the QPO fundamental frequency is low (0.5-2.0 Hz), positive phase lags, which mean that hard photons arrive later than soft photons, were observed in both fundamental and first harmonic frequencies. The phase lags have opposite signs at the two frequencies when the fundamental frequency is high (2.0-4.5 Hz). Such strange behaviors can not be explained by current models. We found the flat radio spectrum observed in most GBHCs can be explained by a hybrid thermal/non-thermal plasma, which can also reproduce the power-law tail that have been observed in many GBHCs beyond the thermal X-ray spectrum.

Lin, Dechun

2000-10-01

351

X-ray Emission from Plasma Focus: Envisioned by Various Competitive Detectors  

NASA Astrophysics Data System (ADS)

A study of X-ray emission from a Mather-type plasma focus device by simultaneously employing various X-ray detectors like silicon pin diode, photoconducting detectors (PCDs)—CVD-diamond and gallium arsenide (GaAs), plastic scintillator coupled with photomultiplier tube with and with out optical fiber is presented. The pin diode and PCDs are masked with 10 ?m thick cobalt filter. The device is energized by 9 ?F capacitor bank charged at 18 kV (1.45 kJ), giving a peak discharge current of about 175 kA, with hydrogen as the filling gas. The optical fiber coupling is found to be beneficial in minimizing the electromagnetic noise generated during the system operation.

Hussain, S.; Ahmad, S.; Sadiq, Mehboob; Lee, P.; Zakaullah, M.; Waheed, A.

2009-03-01

352

A versatile medium-resolution x-ray emission spectrometer for diamond anvil cell applications  

NASA Astrophysics Data System (ADS)

We present design and performance details for a polycapillary-coupled x-ray spectrometer that provides very high collection efficiency at a moderate energy resolution suitable for many studies of nonresonant x-ray emission spectroscopy, especially for samples of heavy elements under high pressures. Using a single Bragg analyzer operating close to backscattering geometry so as to minimize the effect of the weak divergence of the quasicollimated exit beam from the polycapillary optic, this instrument can maintain a typical energy resolution of 5 eV over photon energies from 5 keV to 10 keV. We find dramatically improved count rates as compared to a traditional higher-resolution instrument based on a single spherically bent crystal analyzer.

Mortensen, D. R.; Seidler, G. T.; Bradley, J. A.; Lipp, M. J.; Evans, W. J.; Chow, P.; Xiao, Y.-M.; Boman, G.; Bowden, M. E.

2013-08-01

353

Chemical Analysis of Impurity Boron Atoms in Diamond Using Soft X-ray Emission Spectroscopy  

SciTech Connect

To analyze the local structure and/or chemical states of boron atoms in boron-doped diamond, which can be synthesized by the microwave plasma-assisted chemical vapor deposition method (CVD-B-diamond) and the temperature gradient method at high pressure and high temperature (HPT-B-diamond), we measured the soft X-ray emission spectra in the CK and BK regions of B-diamonds using synchrotron radiation at the Advanced Light Source (ALS). X-ray spectral analyses using the fingerprint method and molecular orbital calculations confirm that boron atoms in CVD-B-diamond substitute for carbon atoms in the diamond lattice to form covalent B-C bonds, while boron atoms in HPT-B-diamond react with the impurity nitrogen atoms to form hexagonal boron nitride. This suggests that the high purity diamond without nitrogen impurities is necessary to synthesize p-type B-diamond semiconductors.

Muramatsu, Yasuji; Iihara, Junji; Takebe, Toshihiko; Denlinger, Jonathan D.

2008-03-29

354

Chemical analysis of impurity boron atoms in diamond using soft X-ray emission spectroscopy.  

PubMed

To analyze the local structure and/or chemical states of boron atoms in boron-doped diamond, which can be synthesized by the microwave plasma-assisted chemical vapor deposition method (CVD-B-diamond) and the temperature gradient method at high pressure and high temperature (HPT-B-diamond), we measured the soft X-ray emission spectra in the CK and BK regions of B-diamonds using synchrotron radiation at the Advanced Light Source (ALS). X-ray spectral analyses using the fingerprint method and molecular orbital calculations confirm that boron atoms in CVD-B-diamond substitute for carbon atoms in the diamond lattice to form covalent B-C bonds, while boron atoms in HPT-B-diamond react with the impurity nitrogen atoms to form hexagonal boron nitride. This suggests that the high purity diamond without nitrogen impurities is necessary to synthesize p-type B-diamond semiconductors. PMID:18614820

Muramatsu, Yasuji; Iihara, Junji; Takebe, Toshihiko; Denlinger, Jonathan D

2008-07-01

355

Modeling of coronal X-ray emission from active cool stars. I. Hyades cluster  

SciTech Connect

X-ray pulse height spectra of the most active cool stars in the Hyades cluster obtained with the Einstein IPC cannot be satisfactorily fitted using isothermal thin plasma emission models. Addition of a second isothermal component provides acceptable fits. However, a more physically meaningful set of coronal parameters is provided by models which consist of an ensemble of loops wih a single maximum temperature, but with the temperature distribution within the loop determined by loop physics. Such models have been successfully fitted to the IPC pulse height spectra. Constraints on loop parameters are discussed for the F-G dwarfs BD + 14 deg 693, BD + 14 deg 690, BD + 15 deg 640, and 71 Tau. Models with a large variation of loop cross section from base to top do not fit the data. A consistent physical description is an ensemble of small high-pressure loops of similar maximum temperature which dominate the coronal X-ray spectrum. 56 references.

Stern, R.A.; Antiochos, S.K.; Harnden, F.R. Jr.

1986-06-01

356

Cometary X-Rays: Line Emission Cross Sections for Multiply Charged Solar Wind Ion Charge Exchange  

SciTech Connect

Absolute line emission cross sections are presented for 1 keV/amu charge exchange collisions of multiply charged solar wind ions with H{sub 2}O, H, O, CO{sub 2}, and CO cometary targets. The present calculations are contrasted with available laboratory data. A parameter-free model is used to successfully predict the recently observed x-ray spectra of comet C/LINEAR 1999 S4. We show that the resulting spectrum is extremely sensitive to the time variations of the solar wind composition. Our results suggest that orbiting x-ray satellites may be a viable way to predict the solar wind intensities and composition on the Earth many hours before the ions reach the earth.

Otranto, S; Olson, R E; Beiersdorfer, P

2006-12-22

357

Modelling The Coupling Of Variability And Spectral Emission In Black Hole X-ray Binaries  

NASA Astrophysics Data System (ADS)

The emission properties of Black Hole X-ray Binaries (BHXRBs) are commonly studied either in terms of their energy spectrum (counts per energy channel) or in terms of their variability properties by means of power spectral density. Each of these can be modelled separately using X-ray analysis packages, however energy spectra and frequency power spectra have not been modelled simultaneously so far to produce a self-consistent picture of the origin and transfer of variability in these systems. We discuss new techniques that use frequency and energy-dependent cross-spectra in different energy channels to model variability and spectral information simultaneously. The powerful combination of spectral and timing information will allow us to 'reverberation map' the emitting regions close to the black hole and measure the propagation of signals through the accretion flow.

Cassatella, Pablo; Uttley, P.; Houck, J.; Davis, J. E.

2012-01-01

358

Detecting X-ray Diffuse Emission with XMM-EPIC:The Compact Galaxy Group HCG16  

NASA Astrophysics Data System (ADS)

The Hickson Compact Group 16 is the coldest detected by ROSAT PSPC (Ponman et al. 1996; Dos Santos & Mamon, 1999) and it is a system containing only spiral and active galaxies. With the imaging and spectroscopy data analysis of the EPIC/MOS cameras we detect the diffuse X-ray emission and, thanks to the XMM PSF, we can safely exclude the contribution of galaxies from the spectrum. The MOS spectra of the diffuse gas are in a perfect agreement between each others and lead to a temperature of kT = 0.28 keV constrained in the range [0.26-0.31] keV and an X-ray luminosity of 7 1040 ergs s-1 in agreement with previous works.

Belsole, E.; Sauvageot, J.-L.; Ponman, T. J.; Arnaud, M.

359

Modeling the radio and hard X-ray emission of pulsar wind nebulae  

NASA Astrophysics Data System (ADS)

The study of pulsar wind nebulae (PWNe) offer important insight into the properties of the central neutron star, the content of its pulsar wind, and progenitor supernova. Recent work has demonstrated that by modeling the broadband spectrum of a PWN it is possible to determine the magnetization and energy spectrum of particles in the pulsar wind. Of particular importance are the PWN's radio and hard X-ray spectrum, since they provide crucial information on the strength of the PWN's magnetic field and the lowest- and highest-energy particles in the PWN. In this talk, I will discuss the implications of improved measured of a PWN's radio and hard X-ray emission on our understanding of the physics in PWNe, in particular the spectral shape of particles accelerated at the pulsar wind termination shock.

Gelfand, Joseph; Slane, Patrick

2012-07-01

360

A versatile medium-resolution x-ray emission spectrometer for diamond anvil cell applications.  

PubMed

We present design and performance details for a polycapillary-coupled x-ray spectrometer that provides very high collection efficiency at a moderate energy resolution suitable for many studies of nonresonant x-ray emission spectroscopy, especially for samples of heavy elements under high pressures. Using a single Bragg analyzer operating close to backscattering geometry so as to minimize the effect of the weak divergence of the quasicollimated exit beam from the polycapillary optic, this instrument can maintain a typical energy resolution of 5 eV over photon energies from 5 keV to 10 keV. We find dramatically improved count rates as compared to a traditional higher-resolution instrument based on a single spherically bent crystal analyzer. PMID:24007080

Mortensen, D R; Seidler, G T; Bradley, J A; Lipp, M J; Evans, W J; Chow, P; Xiao, Y-M; Boman, G; Bowden, M E

2013-08-01

361

Long-term X-ray emission from Swift J1644+57  

NASA Astrophysics Data System (ADS)

The X-ray emission from Swift J1644+57 is not steadily decreasing; instead, it shows multiple pulses with declining amplitudes. We model the pulses as reverse shocks from collisions between the late ejected shells and the externally shocked material, which is decelerated while sweeping the ambient medium. The peak of each pulse is taken as the maximum emission of each reverse shock. With a proper set of parameters, the envelope of peaks in the light curve as well as the spectrum can be modelled well.

Zou, Y. C.; Wang, F. Y.; Cheng, K. S.

2013-10-01

362

Magnetism in FeO at Megabar Pressures from X-Ray Emission Spectroscopy  

SciTech Connect

We report evidence for a preserved magnetic state in FeO up to 143 GPa at room temperature using high-resolution x-ray emission spectroscopy. This observation is based on the spectral line shape of the Fe K{beta} emission line. Up to the highest pressure, FeO remains a magnetic insulator. Combining our results with previous Moessbauer data, we present a new magnetic phase diagram of FeO. Features like a closed-loop P-T antiferromagnetic domain confirm that high-pressure investigations can reveal new physical properties and unexpected phenomena. (c) 1999 The American Physical Society.

Badro, James; Struzhkin, Viktor V.; Shu, Jinfu; Hemley, Russell J.; Mao, Ho-kwang; Kao, Chi-chang; Rueff, Jean-Pascal; Shen, Guoyin

1999-11-15

363

Electronic State Interferences in Resonant X-Ray Emission after K-Shell Excitation in HCl  

NASA Astrophysics Data System (ADS)

We have measured a series of high-resolution x-ray spectra emitted upon resonant photoexcitation of HCl. The photon energy was tuned across the dissociative 1s?6?* resonance and the Rydberg states converging to the Cl 1s-1 threshold, and inelastic photon scattering was observed in the region of KL emission lines. Excellent agreement is found between fully ab initio calculated and measured spectra if interferences between different excitation-emission paths are taken into account. The effect of electronic state interferences is enhanced due to dynamical broadening of the 6?* resonance in HCl.

Kav?i?, M.; Žitnik, M.; Bu?ar, K.; Miheli?, A.; Carniato, S.; Journel, L.; Guillemin, R.; Simon, M.

2010-09-01

364

X-ray emission from plasmas created by smoothed KrF laser irradiation  

SciTech Connect

The x-ray emission from plasmas created by the Naval Research Laboratory Nike KrF laser [Phys. Plasmas {bold 3}, 2098 (1996) ] was characterized using imaging and spectroscopic instruments. The laser wavelength was 1/4 {mu}m, and the beams were smoothed by induced spatial incoherence (ISI). The targets were thin foils of CH, aluminum, titanium, and cobalt and were irradiated by laser energies in the range 100{endash}1500 J. A multilayer mirror microscope operating at an energy of 95 eV recorded images of the plasma with a spatial resolution of 2 {mu}m. The variation of the 95 eV emission across the 800 {mu}m focal spot was 1.3{percent} rms. Using a curved crystal imager operating in the 1{endash}2 keV x-ray region, the density, temperature, and opacity of aluminum plasmas were determined with a spatial resolution of 10 {mu}m perpendicular to the target surface. The spectral line ratios indicated that the aluminum plasmas were relatively dense, cool, and optically thick near the target surface. The absolute radiation flux was determined at 95 eV and in x-ray bandpasses covering the 1{endash}8 keV region. The electron temperature inferred from the slope of the x-ray flux versus energy data in the 5{endash}8 keV region was 900 eV for an incident laser energy of 200 J and an intensity of {approx_equal}10{sup 13} W/cm{sup 2}.

Aglitskiy, Y.; Lehecka, T.; Deniz, A.; Hardgrove, J. [Science Applications International Corporation, McLean, Virginia 22102 (United States); Seely, J.; Brown, C.; Feldman, U. [Space Science Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Pawley, C.; Gerber, K.; Bodner, S.; Obenschain, S.; Lehmberg, R.; McLean, E.; Pronko, M.; Sethian, J.; Stamper, J.; Schmitt, A.; Sullivan, C. [Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); Holland, G.; Laming, M. [SFA Inc., 1401 McCormick Drive, Landover, Maryland 20785 (United States)

1996-09-01

365

Radio and X-ray emission from disc winds in radio-quiet quasars  

NASA Astrophysics Data System (ADS)

It has been proposed that the radio spectra of radio-quiet quasars are produced by free-free emission in the optically thin part of an accretion disc wind. An important observational constraint on this model is the observed X-ray luminosity. We investigate this constraint using a sample of Palomar-Green (PG) radio-quiet quasars for which XMM-Newton European Photon Imaging Camera (EPIC) spectra are available. Comparing the predicted and measured luminosities for 0.5, 2 and 5 keV, we conclude that all of the studied PG quasars require a large hydrogen column density absorber, requiring these quasars to be close to or Compton thick. Such a large column density can be directly excluded for PG 0050+124, for which a high-resolution reflection grating spectrometer spectrum exists. Further constraint on the column density for a further 19 out of the 21 studied PG quasars comes from the EPIC spectrum characteristics such as hard X-ray power-law photon index and the equivalent width of the Fe K? line; and the small equivalent width of the C IV absorber present in ultraviolet spectra. For two sources, PG 1001+054 and PG 1411+442, we cannot exclude that they are indeed Compton thick, and the radio and X-ray luminosity are due to a wind originating close to the supermassive black hole. We conclude that for 20 out of 22 PG quasars studied, free-free emission from a wind emanating from the accretion disc cannot mutually explain the observed radio and X-ray luminosity.

Steenbrugge, K. C.; Jolley, E. J. D.; Kuncic, Z.; Blundell, K. M.

2011-05-01

366

Late-time Radio Emission from X-Ray-selected Tidal Disruption Events  

NASA Astrophysics Data System (ADS)

We present new observations with the Karl G. Jansky Very Large Array of seven X-ray-selected tidal disruption events (TDEs). The radio observations were carried out between 9 and 22 years after the initial X-ray discovery, and thus probe the late-time formation of relativistic jets and jet interactions with the interstellar medium in these systems. We detect a compact radio source in the nucleus of the galaxy IC 3599 and a compact radio source that is a possible counterpart to RX J1420.4+5334. We find no radio counterparts for five other sources with flux density upper limits between 51 and 200 ?Jy (3?). If the detections truly represent late radio emission associated with a TDE, then our results suggest that a fraction, >~ 10%, of X-ray-detected TDEs are accompanied by relativistic jets. We explore several models for producing late radio emission, including interaction of the jet with gas in the circumnuclear environment (blast wave model), and emission from the core of the jet itself. Upper limits on the radio flux density from archival observations suggest that the jet formation may have been delayed for years after the TDE, possibly triggered by the accretion rate dropping below a critical threshold of ~10-2-10^{-3} \\dot{M}_{Edd}. The non-detections are also consistent with this scenario; deeper radio observations can determine whether relativistic jets are present in these systems. The emission from RX J1420.4+5334 is also consistent with the predictions of the blast wave model; however, the radio emission from IC 3599 is substantially underluminous, and its spectral slope is too flat, relative to the blast wave model expectations. Future radio monitoring of IC 3599 and RX J1420.4+5334 will help to better constrain the nature of the jets in these systems.

Bower, Geoffrey C.; Metzger, Brian D.; Cenko, S. Bradley; Silverman, Jeffrey M.; Bloom, Joshua S.

2013-02-01

367

Unique Properties of Thermally Tailored Copper: Magnetically Active Regions and Anomalous X-ray Fluorescence Emissions.  

PubMed

When high-purity copper (>/=99.98%(wt)) is melted, held in its liquid state for a few hours with iterative thermal cycling, then allowed to resolidify, the ingot surface is found to have many small regions that are magnetically active. X-ray fluorescence analysis of these regions exhibit remarkably intense lines from "sensitized elements" (SE), including in part or fully the contiguous series V, Cr, Mn, Fe, and Co. The XRF emissions from SE are far more intense than expected from known impurity levels. Comparison with blanks and standards show that the thermal "tailoring" also introduces strongly enhanced SE emissions in samples taken from the interior of the copper ingots. For some magnetic regions, the location as well as the SE emissions, although persistent, vary irregularly with time. Also, for some regions extraordinarily intense "sensitized iron" (SFe) emissions occur, accompanied by drastic attenuation of Cu emissions. PMID:20037657

Nagel, Christopher J; Herschbach, Dudley R

2009-11-19

368

Local structural distortions in manganites probed by comparative x-ray-emission and x-ray-absorption near-edge measurements  

SciTech Connect

Comparison studies of the perovskite compounds system R{sub 1-x}Ca{sub x}MnO{sub 3} (R=La, Bi) by both Mn K{sub {beta}}-emission spectroscopy and x-ray-absorption near-edge spectroscopy (XANES) are presented. The insensitivity of x-ray-emission measurements to structural distortions coupled with the sensitivity of x-ray-absorption near-edge measurements to changes in both structure and valence enable one to detect the presence of structural distortions, such as local Jahn-Teller (JT) distortions. Theoretical XANES computations for pure cubic perovskite and locally distorted endmembers are used to show the effect of distortions on XANES spectra as well as to comment on the nature of the pre-edge features in the spectra. We show by explicit computations that the near-edge spectra are determined by dipole transitions while pure 1s to 3d electric quadrupole transitions determine a very limited section of the pre-edge region. Simulations of the pre-edge features reveal a direct connection between local distortions and the a1 feature amplitude. The Bi-containing system is found to have significantly higher levels of distortions than the La system. XANES studies of the AMnO{sub 3} (A=La, Pr, and Nd) system reveal a direct relationship between the main line width and the magnitude of the JT distortions.

Qian, Q.; Tyson, T. A.; Kao, C.-C.; Croft, M.; Cheong, S.-W.; Popov, G.; Greenblatt, M.

2001-07-01

369

Emission Lines between 1 and 2 keV in Cometary X-Ray Spectra  

NASA Astrophysics Data System (ADS)

We present the detection of new cometary X-ray emission lines in the 1.0-2.0 keV range using a sample of comets observed with the Chandra X-Ray Observatory and ACIS spectrometer. We have selected five comets from the Chandra sample with good signal-to-noise spectra. The surveyed comets are C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), and C/2008 8P (Tuttle). We modeled the spectra with an extended version of our solar wind charge exchange (SWCX) emission model. Above 1 keV, we find Ikeya-Zhang to have strong emission lines at 1340 and 1850 eV which we identify as being created by SWCX lines of Mg XI and Si XIII, respectively, and weaker emission lines at 1470, 1600, and 1950 eV formed by SWCX of Mg XII, Mg XI, and Si XIV, respectively. The Mg XI and XII and Si XIII and XIV lines are detected at a significant level for the other comets in our sample (LS4, MH, Encke, 8P), and these lines promise additional diagnostics to be included in SWCX models. The silicon lines in the 1700-2000 eV range are detected for all comets, but with the rising background and decreasing cometary emission, we caution that these detections need further confirmation with higher resolution instruments.

Ewing, Ian; Christian, Damian J.; Bodewits, Dennis; Dennerl, Konrad; Lisse, Carey M.; Wolk, Scott J.

2013-01-01

370

Modeling mm- to X-ray flare emission from Sagittarius A*  

NASA Astrophysics Data System (ADS)

Context: We report on new modeling results based on the mm- to X-ray emission of the SgrA* counterpart associated with the massive ~4×106 M? black hole at the Galactic Center. Aims: We investigate the physical processes responsible for the variable emission from SgrA*. Methods: Our modeling is based on simultaneous observations carried out on 07 July, 2004, using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope and the ACIS-I instrument aboard the Chandra X-ray Observatory as well as the Submillimeter Array SMA on Mauna Kea, Hawaii, and the Very Large Array in New Mexico. Results: The observations revealed several flare events in all wavelength domains. Here we show that the flare emission can be described with a combination of a synchrotron self-Compton (SSC) model followed by an adiabatic expansion of the source components. The SSC emission at NIR and X-ray wavelengths involves up-scattered sub-millimeter photons from a compact source component. At the start of the flare, spectra of these components peak at frequencies between several 100 GHz and 2 THz. The adiabatic expansion then accounts for the variable emission observed at sub-mm/mm wavelengths. The derived physical quantities that describe the flare emission give a blob expansion speed of v_exp ~ 0.005 c, magnetic field of B around 60 G or less and spectral indices of ? = 0.8 to 1.4, corresponding to a particle spectral index p ~ 2.6 to 3.8. Conclusions: A combined SSC and adiabatic expansion model can fully account for the observed flare flux densities and delay times covering the spectral range from the X-ray to the mm-radio domain. The derived model parameters suggest that the adiabatic expansion takes place in source components that have a bulk motion larger than v_exp or the expanding material contributes to a corona or disk, confined to the immediate surroundings of SgrA*.

Eckart, A.; Baganoff, F. K.; Morris, M. R.; Kunneriath, D.; Zamaninasab, M.; Witzel, G.; Schödel, R.; García-Marín, M.; Meyer, L.; Bower, G. C.; Marrone, D.; Bautz, M. W.; Brandt, W. N.; Garmire, G. P.; Ricker, G. R.; Straubmeier, C.; Roberts, D. A.; Muzic, K.; Mauerhan, J.; Zensus, A.

2009-06-01

371

Charge transfer and x-ray emission in collisions between slow, highly charged ions and neutral atoms  

Microsoft Academic Search

The Classical Trajectory Monte Carlo method was used to study Charge transfer between slow (<50 eV\\/amu) highly charged ions (Ne^10+, Ar^18+) and their respective neutral atoms. State specific electron capture cross sections were calculated and used to estimate cross sections for the resulting x-ray emissions. The calculated x-ray line emissions are compared with measurements made at Lawrence Livermore National Laboratory

J. A. Perez; B. P. Thomas; R. E. Olson; P. Beiersdorfer

2002-01-01

372

3D models of radiatively driven colliding winds in massive O + O star binaries - III. Thermal X-ray emission  

Microsoft Academic Search

The X-ray emission from the wind-wind collision in short-period massive O + O star binaries is investigated. The emission is calculated from 3D hydrodynamical models which incorporate gravity, the driving of the winds, orbital motion of the stars and radiative cooling of the shocked plasma. Changes in the amount of stellar occultation and circumstellar attenuation introduce phase-dependent X-ray variability in

J. M. Pittard; E. R. Parkin

2010-01-01

373

Dominance of magnetic cataclysmic variables in the resolved Galactic ridge X-ray emission of the limiting window  

NASA Astrophysics Data System (ADS)

The diffuse appearance of the Galactic ridge X-ray emission has been puzzling since its discovery due to the lack of compelling theories for sustainable hot diffuse X-ray emission in the Galactic plane. Recently, Revnivtsev et al. claimed that ˜90 per cent of the 6.5-7.1 keV X-ray flux from a small section of a low-extinction region at 1°.4 south of the Galactic Centre has been resolved to discrete sources with LX, 2-10 keV ?4×10-16 erg s-1 cm-2, using ultradeep (1 Ms) observations made by the Chandra X-ray Observatory. They also concluded that coronally active stars such as active binaries (ABs) contribute ˜60 per cent of the resolved flux. However, our recent discovery of a large population of magnetic cataclysmic variables (MCVs) in the same region suggests their significant role in the resolved hard X-ray flux. In addition, deep X-ray surveys of other several Galactic bulge fields over the past decade have indicated that MCVs are likely the major contributor in the hard X-ray emission above 2-3 keV. To solve this mystery, we have conducted an independent in-depth analysis of discrete X-ray sources in the low-extinction region. The total fraction of the 6.5-7.1 keV flux we can confidently claim as resolved is ˜70-80 per cent, which largely agrees with Revnivtsev et al., but leaves some room for diffuse components. However, despite the various attempts, we consistently find that the resolved hard X-ray flux above 3 keV is dominated by relatively bright, hard X-ray sources such as MCVs, whereas the contribution from relatively faint, soft sources such as ABs is below 20 per cent. We describe in detail our analysis procedure in order to elucidate possible origins of the discrepancy.

Hong, JaeSub

2012-12-01

374

Application of CVD diamonds as dosimeters of soft X-ray emission from plasma sources  

NASA Astrophysics Data System (ADS)

The thermoluminescent properties of polycrystalline chemical vapour deposition (CVD) diamond, as free-standing CVD cutting tool material, type CVDITE-CDM (De Beers Company), were studied with respect to its use in the dosimetry of soft X-ray emission from laser-produced plasma. The range of linearity for 5.9-keV radiation was measured to be only two orders of magnitude, ranging from a sensitivity threshold of ~0.01 to ~2Gy. In this linearity range, the sensitivity of CVD diamonds is about 65 times lower than the sensitivity of TLD-100 dosimeters. The unpolished (grained) face of CVD diamonds shows ~1.5-times higher thermoluminescence (TL) response after irradiation than the polished face, in the high-temperature range, but the polished face shows slightly higher TL response in the low-temperature range. A strong TL sensitivity to the blue portion of the visible light spectrum was measured. Simultaneous irradiation of TLD-100 dosimeters and CVD diamonds by soft X-rays emitted from a laser-produced plasma showed that CVDITE-CDM diamonds can be applied as detectors of intense soft X-ray radiation.

Krása, J.; Juha, L.; Vorlí?ek, V.; Cejnarová, A.

2004-05-01

375

Delayed X-ray emission from fallback in compact-object mergers  

NASA Astrophysics Data System (ADS)

When double neutron star or neutron star-black hole binaries merge, the final remnant may comprise a central solar-mass black hole surrounded by a ~0.01-0.1Msolar torus. The subsequent evolution of this disc may be responsible for short ?-ray bursts (SGRBs). A comparable amount of mass is ejected into eccentric orbits and will eventually fallback to the merger site after ~0.01 s. In this paper, we investigate analytically the fate of the fallback matter, which may provide a luminous signal long after the disc is exhausted. We find that matter in the eccentric tail returns at a super-Eddington rate and eventually (>~0.1 s) is unable to cool via neutrino emission and accrete all the way to the black hole. Therefore, contrary to previous claims, our analysis suggests that fallback matter is not an efficient source of late-time accretion power and unlikely to cause the late-flaring activity observed in SGRB afterglows. The fallback matter rather forms a radiation-driven wind or a bound atmosphere. In both the cases, the emitting plasma is very opaque and photons are released with a degraded energy in the X-ray band. We therefore suggest that compact binary mergers could be followed by an `X-ray renaissance', as late as several days to weeks after the merger. This might be observed by the next generation of X-ray detectors.

Rossi, Elena M.; Begelman, Mitchell C.

2009-02-01

376

Intrinsic disc emission and the soft X-ray excess in active galactic nuclei  

NASA Astrophysics Data System (ADS)

Narrow-line Seyfert 1 (NLS1) galaxies have low-mass black holes and mass accretion rates close to (or exceeding) Eddington, so a standard blackbody accretion disc should peak in the extreme ultraviolet. However, the lack of true absorption opacity in the disc means that the emission is better approximated by a colour temperature corrected blackbody, and this colour temperature correction is large enough (˜2.4) that the bare disc emission from a zero spin black hole can extend into the soft X-ray bandpass. Part of the soft X-ray excess seen in these objects must be intrinsic emission from the disc unless the vertical structure is very different to that predicted. None the less, this is not the whole story even for the extreme NLS1 as the shape of the soft excess is much broader than predicted by a bare disc spectrum, indicating some Compton upscattering by warm, optically thick material. We associate this with the disc itself, so it must ultimately be powered by mass accretion. We build an energetically self-consistent model assuming that the emission thermalizes to a (colour temperature corrected) blackbody only at large radii. At smaller radii the gravitational energy is split between powering optically thick Comptonized disc emission (forming the soft X-ray excess) and an optically thin corona above the disc (forming the tail to higher energies). We show examples of this model fit to the extreme NLS1 RE J1034+396, and to the much lower Eddington fraction broad-line Seyfert 1 PG 1048+231. We use these to guide our fits and interpretations of three template spectra made from co-adding multiple sources to track out a sequence of active galactic nucleus (AGN) spectra as a function of L/LEdd. Both the individual objects and template spectra show the surprising result that the Compton upscattered soft X-ray excess decreases in importance with increasing L/LEdd. The strongest soft excesses are associated with low mass accretion rate AGN rather than being tied to some change in disc structure around Eddington. We argue that this suggests a true break in accretion flow properties between stellar and supermassive black holes. The new model is publicly available within the XSPEC spectral fitting package.

Done, Chris; Davis, S. W.; Jin, C.; Blaes, O.; Ward, M.

2012-03-01

377

Einstein Observatory survey of X-ray emission from solar-type stars - the late F and G dwarf stars  

SciTech Connect

Results of a volume-limited X-ray survey of stars of luminosity classes IV and V in the spectral range F7-G9 observed with the Einstein Observatory are presented. Using survival analysis techniques, the stellar X-ray luminosity function in the 0.15-4.0 keV energy band for both single and multiple sources. It is shown that the difference in X-ray luminosity between these two classes of sources is consistent with the superposition of individual components in multiple-component systems, whose X-ray properties are similar to those of the single-component sources. The X-ray emission of the stars in our sample is well correlated with their chromospheric CA II H-K line emission and with their projected equatorial rotational velocity. Comparison of the X-ray luminosity function constructed for the sample of the dG stars of the local population with the corresponding functions derived elsewhere for the Hyades, the Pleiades, and the Orion Ic open cluster confirms that the level of X-ray emission decreases with stellar age. 62 references.

Maggio, A.; Sciortino, S.; Vaiana, G.S.; Majer, P.; Bookbinder, J.

1987-04-01

378

AN INVERSE COMPTON SCATTERING ORIGIN OF X-RAY FLARES FROM Sgr A*  

SciTech Connect

The X-ray and near-IR emission from Sgr A* is dominated by flaring, while a quiescent component dominates the emission at radio and submillimeter (sub-mm) wavelengths. The spectral energy distribution of the quiescent emission from Sgr A* peaks at sub-mm wavelengths and is modeled as synchrotron radiation from a thermal population of electrons in the accretion flow, with electron temperatures ranging up to {approx}5-20 MeV. Here, we investigate the mechanism by which X-ray flare emission is produced through the interaction of the quiescent and flaring components of Sgr A*. The X-ray flare emission has been interpreted as inverse Compton, self-synchrotron Compton, or synchrotron emission. We present results of simultaneous X-ray and near-IR observations and show evidence that X-ray peak flare emission lags behind near-IR flare emission with a time delay ranging from a few to tens of minutes. Our inverse Compton scattering modeling places constraints on the electron density and temperature distributions of the accretion flow and on the locations where flares are produced. In the context of this model, the strong X-ray counterparts to near-IR flares arising from the inner disk should show no significant time delay, whereas near-IR flares in the outer disk should show a broadened and delayed X-ray flare.

Yusef-Zadeh, F. [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Wardle, M. [Department of Physics and Astronomy, Macquarie University, Sydney NSW 2109 (Australia); Dodds-Eden, K.; Gillessen, S.; Genzel, R. [Max Planck Institut fuer Extraterrestrische Physik, Postfach 1312, D-85741 Garching (Germany); Heinke, C. O. [Department of Physics, University of Alberta, 4-183 CCIS, Edmonton, AB T6G 2E1 (Canada); Bushouse, H. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Grosso, N.; Porquet, D. [Observatoire astronomique de Strasbourg, Universite de Strasbourg, CNRS, INSU, 11 rue de l'Universite, 67000 Strasbourg (France)

2012-07-15

379

Height structure of X-ray, EUV, and white-light emission in a solar flare  

NASA Astrophysics Data System (ADS)

Context. The bulk of solar flare emission originates from very compact sources located in the lower solar atmosphere and observable at a broad range of wavelengths such as near optical, UV, EUV, soft and hard X-rays, and gamma-rays. Nevertheless, very few spatially resolved imaging observations have been performed to determine the structure of these compact regions. Aims: We investigate the above-the-photosphere heights of hard X-ray (HXR), EUV, and white-light (6173 Å) continuum sources in the low atmosphere and the corresponding densities at these heights. By considering the collisional transport of solar energetic electrons, we also determine where and how much energy is deposited and compare these values with the emissions observed in HXR, EUV, and the continuum. Methods: Simultaneous EUV/continuum images from AIA/HMI on-board SDO and HXR RHESSI images are compared to study a well-observed gamma-ray limb flare. Using RHESSI X-ray visibilities, we determine the height of the HXR sources as a function of energy above the photosphere. Co-aligning AIA/SDO and HMI/SDO images with RHESSI, we infer, for the first time, the heights and characteristic densities of HXR, EUV, and continuum (white-light) sources in the flaring footpoint of the magnetic loop. Results: We find 35-100 keV HXR sources at heights of between 1.7 and 0.8 Mm above the photosphere, below the 6173 Å continuum emission that appears at heights 1.5-3 Mm and the peak of EUV emission originating near 3 Mm. Conclusions: The EUV emission locations are consistent with energy deposition from low energy electrons of ~12 keV occurring in the top layers of the fully ionized chromosphere/low corona and not by ? 20 keV electrons that produce HXR footpoints in the lower neutral chromosphere. The maximum of white-light continuum emission appears between the HXR and EUV emission, presumably in the transition between ionized and neutral atmospheres, implying that it consists of free-bound and free-free continuum emission. We note that the energy deposited by low energy electrons is sufficient to explain the energetics of both the optical and UV emissions. Two movies are available in electronic form at http://www.aanda.org

Battaglia, M.; Kontar, E. P.

2011-09-01

380

HARD X-RAY AND MICROWAVE EMISSIONS FROM SOLAR FLARES WITH HARD SPECTRAL INDICES  

SciTech Connect

We analyze 10 flare events that radiate intense hard X-ray (HXR) emission with significant photons over 300 keV to verify that the electrons that have a common origin of acceleration mechanism and energy power-law distribution with solar flares emit HXRs and microwaves. Most of these events have the following characteristics. HXRs emanate from the footpoints of flare loops, while microwaves emanate from the tops of flare loops. The time profiles of the microwave emission show delays of peak with respect to those of the corresponding HXR emission. The spectral indices of microwave emissions show gradual hardening in all events, while the spectral indices of the corresponding HXR emissions are roughly constant in most of the events, though rather rapid hardening is simultaneously observed in some for both indices during the onset time and the peak time. These characteristics suggest that the microwave emission emanates from the trapped electrons. Then, taking into account the role of the trapping of electrons for the microwave emission, we compare the observed microwave spectra with the model spectra calculated by a gyrosynchrotron code. As a result, we successfully reproduce the eight microwave spectra. From this result, we conclude that the electrons that have a common acceleration and a common energy distribution with solar flares emit both HXR and microwave emissions in the eight events, though microwave emission is contributed to by electrons with much higher energy than HXR emission.

Kawate, T. [Kwasan and Hida Observatory, Kitashirakawa-oiwakecho, Sakyo, Kyoto 606-8502 (Japan); Nishizuka, N. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 229-8510 (Japan); Oi, A. [College of Science, Ibaraki University, Mito, Ibaraki 310-8512 (Japan); Ohyama, M. [Faculty of Education, Shiga University, 2-5-1 Hiratsu, Otsu, Shiga 1-1, Baba Hikone city, Siga 522-8522 (Japan); Nakajima, H., E-mail: kawate@kusastro.kyoto-u.ac.jp [Nobeyama Solar Radio Observatory, NAOJ, Nobeyama, Minamisaku, Nagano 384-1305 (Japan)

2012-03-10

381

A miniature X-ray emission spectrometer (miniXES) for high-pressure studies in a diamond anvil cell.  

PubMed

Core-shell X-ray emission spectroscopy (XES) is a valuable complement to X-ray absorption spectroscopy (XAS) techniques. However, XES in the hard X-ray regime is much less frequently employed than XAS, often as a consequence of the relative scarcity of XES instrumentation having energy resolutions comparable with the relevant core-hole lifetimes. To address this, a family of inexpensive and easily operated short-working-distance X-ray emission spectrometers has been developed. The use of computer-aided design and rapid prototype machining of plastics allows customization for various emission lines having energies from ?3 keV to ?10 keV. The specific instrument described here, based on a coarsely diced approximant of the Johansson optic, is intended to study volume collapse in Pr metal and compounds by observing the pressure dependence of the Pr L? emission spectrum. The collection solid angle is ?50 msr, roughly equivalent to that of six traditional spherically bent crystal analyzers. The miniature X-ray emission spectrometer (miniXES) methodology will help encourage the adoption and broad application of high-resolution XES capabilities at hard X-ray synchrotron facilities. PMID:22338686

Pacold, J I; Bradley, J A; Mattern, B A; Lipp, M J; Seidler, G T; Chow, P; Xiao, Y; Rod, Eric; Rusthoven, B; Quintana, J

2012-01-19

382

X-ray and EUV Emission Studies of Copper Vacuum Spark Plasma  

SciTech Connect

A vacuum spark system with a copper anode and electrode of gap 1.5 mm is investigated for the purpose of developing it as a possible radiation source for Next Generation Lithography (NGL). At discharge voltage in the range of 10 to 15 kV and an ambient pressure of about 10{sup -3} mbar, both X-ray (measured by PIN diode) and extreme ultraviolet, EUV (measured by SXUV5A with integrated filter) can be measured simultaneously when good pinching discharge as indicated by sharp dip in the waveform of the rate of current is achieved. For discharge with mild pinching, only EUV emission is observed.

Chan, L. S.; Ghomeishi, M.; Yap, S. L.; Wong, C. S. [Plasma Research Laboratory, Physics Department, Faculty of Science, University of Malaya, 50603 KualaLumpur (Malaysia)

2010-07-07

383

Analytical Applications Of Particle-Induced X-Ray Emission (PIXE)  

SciTech Connect

In this paper a complex study of the capabilities of Particle-Induced X-ray Emission (PIXE) technique for the determination of major, minor and trace constituents of metallurgical, biological and environmental samples has been done. The elements identified in the metallurgical samples (steels) using PIXE were: K, Ca, V, Cr, Mn, Fe, Co, Cu, Ni, Zn, W, Ga, As, Pb, Mo, Rb, In, Rh, Zr, Pd, Nb, Sn and Sb. In the investigated biological and environmental samples (vegetals leaves, soil and mosses) PIXE analysis allowed determination of: S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, As, Hg and Pb.

Popescu, I. V.; Stihi, C.; Bancuta, A.; Dima, G. ['Valahia' University of Targoviste, Targoviste (Romania); Ene, A. ['Dunarea de Jos' University of Galati, Galati (Romania); Badica, T. ['Horia Hulubei' NIPNE, Bucharest (Romania); Ghisa, V. ['Ovidius' University of Constanta, Constanta (Romania)

2007-04-23

384

Applications of simultaneous ion backscattering and ion-induced x-ray emission  

SciTech Connect

Simultaneous ion backscattering and ion-induced x-ray emission (E/sub x/greater than or equal to 300 eV) analyses have been performed using helium ions as probes of the first few hundred nanometers of various materials. These studies serve as a demonstration of the complementary nature of the two types of information obtained. Uncertainties associated with each of the individual techniques were reduced by performing both analyses. The principal advantages of simultaneous analyses over sequential analyses have been delineated.

Musket, R.G.

1983-05-01

385

Detection of hard X-ray emission from Nova Sgr 2012 with Swift  

NASA Astrophysics Data System (ADS)

We observed Nova Sgr 2012 (PNV J17452791-2305213) with the Swift satellite on 2012 May 10, 40 days after the discovery of this nova. The total exposure time with the XRT instrument was 6280 s. In contrast to the non-detections reported in ATels #4061 and #4088, Swift/XRT clearly detected X-ray emission from the nova on 2012 May 10. A total of 249 source counts were detected within a circular region with a radius of 20 pixels centered on the position of the nova, resulting in a 0.3-10 keV count rate of 0.039 c/s.

Nelson, Thomas; Mukai, Koji; Sokoloski, Jennifer; Chomiuk, Laura; Rupen, Michael; Mioduszewski, Amy

2012-05-01

386

A magnetizing system for dichroism measurements in soft x-ray emission excited by synchrotron radiation  

SciTech Connect

We present the design and performance of a magnetic circuit suitable for magnetizing solid samples in the measurements of soft x-ray emission dichroism excited by synchrotron radiation. The system allows a variety of samples to be magnetized and satisfies the rather stringent geometrical constraints due to the need for minimizing the effect of photon self-absorption by the sample. The magnetic circuit is ultrahigh vacuum compatible, can reach about 2800 G, and allows fine adjustment of sample position. {copyright} {ital 1996 American Institute of Physics.}

Dallera, C.; Ghiringhelli, G.; Braicovich, L. [INFM and Dipartimento di Fisica del Politecnico Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

1996-02-01

387

Coincident emission of a characteristic and a continuum x ray in electron-atom collisions  

SciTech Connect

An observation of the simultaneous emission of a characteristic {ital K} x ray and a continuum photon has been made for 70-keV electrons bombarding target atoms of Fe, Cu, Y, and Ag. The absolute cross section for Y and Ag agree well with a model that considers a contribution from both double-bremsstrahlung and electron-electron bremsstrahlung processes. The data for Fe and Cu, on the other hand, are about an order of magnitude higher than the model, suggesting the possibility of a resonant polarization bremsstrahlung contribution to the double-bremsstrahlung process.

Kahler, D.L.; Liu, J.; Quarles, C.A. (Texas Christian University, Fort Worth, Texas 76129 (United States))

1992-06-01

388

Soft-x-ray-emission spectra of solid Kr and Xe  

SciTech Connect

We present the first soft x-ray-emission spectra for solid Kr (4{ital p}-3{ital d}) and Xe (5{ital p}-4{ital d}) that are free of complicating satellite spectra. Monochromatic synchrotron-radiation excitation is used to suppress the satellites. The data are analyzed to determine the {ital P}{sub 3/2} bandwidth for both elements; these results are compared with both photoemission data and available theoretical calculations. Bandwidths are found to be larger than those predicted by most electronic structure calculations.

Jia, J.J.; O'Brien, W.L.; Callcott, T.A.; Dong, Q.Y. (University of Tennessee, Knoxville, TN (USA)); Rubensson, J.; Mueller, D.R.; Ederer, D.L. (National Institute of Standards and Technology, Gaithersburg, MD (USA))

1991-08-05

389

X-ray emission from the remnant of a carbon deflagration supernova - SN 1572 (Tycho)  

SciTech Connect

A spherically symmetric hydrodynamic code is used to study the evolution of a young supernova remnant on the basis of a carbon deflagration model for type Ia supernovae. The nonequilibrium X-ray emission has been determined for the elemental composition of the model. The discrepancy between the derived intensity of the Fe D-alpha line blend and the observed value is eliminated by assuming that the stratification of the elemental composition in the supernova ejecta is partially removed by mixing. 59 references.

Itoh, H.; Masai, K.; Nomoto, K.

1988-11-01

390

Observation of ? backbonding features appearing in Fe 2p X-ray absorption spectra and Fe 1s-4p-1s resonant X-ray emission spectra of RbMn[Fe(CN)6  

NASA Astrophysics Data System (ADS)

Satellite features by p backbonding (metal-to-ligand charge transfer) were observed in both Fe 2p (L3,2-edge) X-ray absorption spectra and 1s-4p-1s resonant X-ray emission spectra for RbMn[Fe(CN)6], which can be theoretically explained using common parameters. Fe L3,2-edge and Mn L3,2-edge X-ray absorption spectra for low temperature phase are also presented.

Kitajima, Yoshinori; Nanba, Y?suke; Tanaka, Masayuki; Koga, Yuji; Ueno, Akihiro; Nakagawa, Kosuke; Tokoro, Hiroko; Ohkoshi, Shin-ichi; Iwazumi, Toshiaki; Okada, Kozo; Isozumi, Yasuhito

2013-04-01

391

Super-Hard X-Ray Emission from ? Carinae Observed with Suzaku  

NASA Astrophysics Data System (ADS)

We present the Suzaku results of ? Carinae in the 5-50keV range conducted twice around the apastron in 2005 August for 50ks and in 2006 February for 20ks. The X-ray Imaging Spectrometer (XIS) produced hard (5-12keV) band spectra, resolving K shell lines from highly ionized Fe and Ni. The Hard X-ray Detector yielded a significant detection in the super-hard (15-50keV) band, which was uncontaminated by near-by sources. We constrained the temperature of the optically thin thermal plasma emission dominant in the hard band to be 3-4keV using the K-shell line features with the XIS. We found significant excess emission above the thermal emission in the super-hard band with the PIN, confirming the previous INTEGRAL ISGRI report. The entire 5-50keV spectra were fitted by a combination of a thermal plasma model plus a flat power-law, or a very hot thermal bremsstrahlung model for the excess emission. No significant change of the excess emission was found at different epochs within the systematic and statistical uncertainties, and no flare-like flux amplification was seen in the hard band, indicating that the excess emission is a steady phenomenon. We argue that the super-hard emission is attributable to the inverse Compton of stellar UV photons by non-thermal electrons or to the thermal bremsstrahlung of very hot plasma, and not to the bremsstrahlung by non-thermal electrons colliding with cold ambient matter.

Sekiguchi, Akiko; Tsujimoto, Masahiro; Kitamoto, Shunji; Ishida, Manabu; Hamaguchi, Kenji; Mori, Hideyuki; Tsuboi, Yohko

2009-08-01

392

Aborted jets and the X-ray emission of radio-quiet AGNs  

NASA Astrophysics Data System (ADS)

We propose that radio-quiet quasars and Seyfert galaxies have central black holes powering outflows and jets which propagate only for a short distance, because the velocity of the ejected material is smaller than the escape velocity. We call them ``aborted" jets. If the central engine works intermittently, blobs of material may be produced, which can reach a maximum radial distance and then fall back, colliding with the blobs produced later and still moving outwards. These collisions dissipate the bulk kinetic energy of the blobs by heating the plasma, and can be responsible (entirely or at least in part) for the generation of the high energy emission in radio-quiet objects. This is alternative to the more conventional scenario in which the X-ray spectrum of radio-quiet sources originates in a hot (and possibly patchy) corona above the accretion disk. In the latter case the ultimate source of energy of the emission of both the disk and the corona is accretion. Here we instead propose that the high energy emission is powered also by the extraction of the rotational energy of the black hole (and possibly of the disk). By means of Montecarlo simulations we calculate the time dependent spectra and light curves, and discuss their relevance to the X-ray spectra in radio-quiet AGNs and galactic black hole sources. In particular, we show that time variability and spectra are similar to those observed in Narrow Line Seyfert 1 galaxies.

Ghisellini, G.; Haardt, F.; Matt, G.

2004-01-01

393

X-RAY EMISSIONS FROM COLLISIONS OF O{sup 6+} IONS WITH CO  

SciTech Connect

Laboratory measurements of soft X-ray emissions from collisions between 36 keV O{sup 6+} ions and CO have been carried out with the aim of simulating emissions from comets interacting with the solar wind. Spectra in the range 62-155 eV are recorded and compared to results of the over-barrier model (OBM) and multichannel Landau-Zener (MLZ) calculations. Emissions from n = 3, 4 states of O{sup 5+} are observed. This is in good agreement with the OBM predictions of highest n-state for the electron capture. Line intensities for the n = 4 capture in simulated spectra using the semi-empirical MLZ approach, taking into account multielectron captures, are in very good agreement with experimental measurements. However, the OBM does not correctly account for direct feeding of the n = 3 levels for the CO target, though it does explain predominance of the n = 3 levels for an He target.

Miller, K. A.; Smith, W. W.; Ehrenreich, T.; Kessel, Q. C.; Pollack, E.; Verzani, C.; Kharchenko, V. A. [Physics Department, University of Connecticut, Storrs, CT 06269 (United States); Chutjian, A.; Lozano, J. A.; Djuric, N.; Smith, S. J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

2011-12-01

394

Global X-ray emission and central properties of early type galaxies  

NASA Astrophysics Data System (ADS)

Hubble Space Telescope observations have revealed that the central surface brightness profiles of early type galaxies can be divided into two types: ``core" profiles and featureless power law profiles, without cores. On the basis of this and previous results, early type galaxies have been grouped into two families. One consists of coreless galaxies, which are also rapidly rotating, nearly isotropic spheroids, and with disky isophotes. The other is made of core galaxies, which are slowly rotating and boxy-distorted. Here I investigate the relationship between global X-ray emission and shape of the inner surface brightness profile, for a sample of 59 early type galaxies. I find a clear dichotomy also in the X-ray properties, in the sense that core galaxies span the whole observed range of L_X values (roughly two orders of magnitude in L_X ), while power law galaxies are confined to log L_X (erg s-1)<41. Moreover, the relation between L_X and the shape of the central profile seems to be the strongest among the relations of L_X with the basic properties characterizing the two families of early type galaxies. As an example, L_X is more deeply connected with the shape of the central profile than with the isophotal shape distortion, or the importance of galactic rotation. So, a global property such as L_X , that measures the hot gas content on a galactic scale, turns out to be surprisingly well linked to a nuclear property. Various possible reasons are explored for the origin of the different L_X behavior of core and power law galaxies. While a few explanations can be imagined for the large spread in the X-ray luminosities of core galaxies, an open problem is why power law ones never become very X-ray bright. It is likely that the presence of a central massive black hole, and possibly also the environment, play an important role in determining L_X (i.e., the hot gas content). Therefore the problem of interpreting the X-ray properties of early type galaxies turns out to be more complex than thought so far.

Pellegrini, S.

1999-11-01

395

X-RAY EMISSION FROM THE SOMBRERO GALAXY: A GALACTIC-SCALE OUTFLOW  

SciTech Connect

Based on new and archival Chandra observations of the Sombrero galaxy (M 104 = NGC 4594), we study the X-ray emission from its nucleus and the extended X-ray emission in and around its massive stellar bulge. We find that the 0.3-8 keV luminosity of the nucleus appears constant at {approx}2.4 x 10{sup 40} erg s{sup -1}, or {approx}10{sup -7} of its Eddington luminosity, on three epochs between 1999 December and 2008 April, but drops by a factor of two in the 2008 November observation. The 2-6 keV unresolved emission from the bulge region closely follows the K-band starlight and most likely arises from unresolved stellar sources. At lower energies, however, the unresolved emission reaches a galactocentric radius of at least 23 kpc, significantly beyond the extent of the starlight, clearly indicating the presence of diffuse hot gas. We isolate the emission of the gas by properly accounting for the emission from unresolved stellar sources, predominantly cataclysmic variables and coronally active binaries, whose quasi-universal X-ray emissivity was recently established. We find a gas temperature of {approx}0.6 keV with little variation across the field of view, except for a lower temperature of {approx}0.3 keV along the stellar disk. The metal abundance is not well constrained due to the limited counting statistics, but is consistent with metal enrichment by Type Ia supernovae (SNe Ia). We measure a total intrinsic 0.3-2 keV luminosity of {approx}2 x 10{sup 39} erg s{sup -1}, which corresponds to only 1% of the available energy input by SNe Ia in the bulge, but is comparable to the prediction by the latest galaxy formation models for disk galaxies as massive as Sombrero. However, such numerical models do not fully account for internal feedback processes, such as nuclear feedback and stellar feedback, against accretion from the intergalactic medium. On the other hand, we find no evidence for either the nucleus or the very modest star-forming activities in the disk to be a dominant heating source for the diffuse gas. We also show that neither the expected energy released by SNe Ia nor the expected mass returned by evolved stars is recovered by observations. We argue that in Sombrero a galactic-scale subsonic outflow of hot gas continuously removes much of the 'missing' energy and mass input from the bulge region. The observed density and temperature distributions of such an outflow, however, continue to pose challenges to theoretical studies.

Li Zhiyuan; Jones, Christine; Forman, William R.; Kraft, Ralph P.; Lal, Dharam V.; Di Stefano, Rosanne [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Spitler, Lee R. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Tang, Shikui; Wang, Q. Daniel [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Gilfanov, Marat [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str 1, 85741 Garching bei Muenchen (Germany); Revnivtsev, Mikhail, E-mail: zyli@cfa.harvard.edu [Excellence Cluster Universe, Technische Universitaet Muenchen, Boltzmannstr.2, 85748 Garching (Germany)

2011-04-01

396

An X-ray emission-line spectrum of Nova V382Velorum 1999  

NASA Astrophysics Data System (ADS)

We report on the analysis of an X-ray grating spectrum of the Classical Nova V382Vel (1999), obtained with the Low Energy Transmission Grating (LETG)+HRC-S instrument onboard Chandra, which shows emission lines dominating over any continuum. Lines of Si, Mg, Ne, O, N and C are identified, but no Fe lines are detected. The total luminosity in the lines is ~4 × 1027ergs-1 (corrected for NH= 1.2 × 1021cm-2). The lines have broad profiles with full width at half-maximum corresponding to a velocity ~2900 +/-200kms-1. Some structure is identified in the profiles, but for different elements we find different profile structures. While lines of O show a broadened Gaussian profile, those of Ne are double-peaked, suggesting a fragmented emitting plasma. Using the emission measure distribution, we derive relative element abundances and find abundances of Ne and N that are significantly enhanced relative to that of O, while Fe is not overabundant. The lack of any source emission longwards of 50Åand the OVIII Ly?/Ly? line ratio supports previous values of the hydrogen column density. We find weak continuum emission from the white dwarf, consistent with a blackbody spectrum with an upper limit to the temperature of T= 3 × 105K, assuming a source radius of 6000km. The upper limit for the integrated blackbody luminosity is 2 × 1036ergs-1. The BeppoSAX and Chandra ACIS observations of V382Vel show that the nova was bright and in the Super-Soft phase as late as 1999 December 30. Our LETG observation obtained 6 weeks later, as well as all subsequent X-ray observations, showed a remarkable fading to a nearly pure emission line phase which suggests that nuclear burning on the white dwarf had turned off by February. In the absence of a photoionizing source, the emission lines were formed in a collisionally ionized and excited expanding shell.

Ness, J.-U.; Starrfield, S.; Jordan, C.; Krautter, J.; Schmitt, J. H. M. M.

2005-12-01

397

X-ray pulse emission from cesium chloride aqueous solutions when irradiated by double-pulsed femtosecond laser pulses  

SciTech Connect

The intensity of x-ray emission from the aqueous solutions irradiated with focused femtosecond laser pulses (main pulses and relatively low-intensity prepulses) was measured as a function of the delay time between the main pulses and prepulses. Four different x-ray intensity peaks were observed in the picosecond and nanosecond ranges. The prepulse irradiation caused an increase in the x-ray intensity by a factor of 10{sup 3}-10{sup 4}, as confirmed by x-ray emission spectroscopy. Time-resolved reflectance measurements and imaging revealed that the increase was caused by the solution surface dynamics such as the picosecond plasma formation and decay and the transient (nanoseconds) surface roughness.

Hatanaka, Koji [Center for Ultrafast Intense Laser Science, Graduate School of Science, University of Tokyo, Tokyo 113-0033 (Japan); Ono, Hiroshi; Fukumura, Hiroshi [Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan)

2008-08-11

398

The Nature of the UV/Optical Emission of the Ultraluminous X-Ray Source in Holmberg II  

NASA Astrophysics Data System (ADS)

We report on UV and X-ray spectroscopy and broadband optical observations of the ultraluminous X-ray source in Holmberg II. Fitting various stellar spectral models to the combined, non-simultaneous data set, we find that normal metallicity stellar spectra are ruled out by the data, while low-metallicity, Z = 0.1 Z ?, late O-star spectra provide marginally acceptable fits, if we allow for the fact that X-ray ionization from the compact object may reduce or eliminate UV absorption/emission lines from the stellar wind. By contrast, an irradiated disk model fits both UV and optical data with ?2/dof = 175.9/178, and matches the nebular extinction with a reddening of E(B - V) = 0.05+0.05 - 0.04. These results suggest that the UV/optical flux of Holmberg II X-1 may be dominated by X-ray irradiated disk emission.

Tao, Lian; Kaaret, Philip; Feng, Hua; Grisé, Fabien

2012-05-01

399

Chandra Observations of the Pleiades Open Cluster: X-Ray Emission from Late B- to Early F-Type Binaries  

NASA Astrophysics Data System (ADS)

We present the analysis of a 38.4 and 23.6 ks observation of the core of the Pleiades open cluster. The Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory detected 99 X-ray sources in a 17'×17' region, including 18 of 23 Pleiades members. Five candidate Pleiades members have also been detected, confirming their cluster membership. Fifty-seven sources have no optical or near-infrared counterparts to limiting magnitudes V=22.5 and J=14.5. The unidentified X-ray sources are probably background active galactic nuclei and not stars. The Chandra field of view contains seven intermediate-mass cluster members. Five of these, HII 980 (B6+G), HII 956 (A7+F6), HII 1284 (A9+K), HII 1338 (F3+F6), and HII 1122 (F4+K), are detected in this study. All but HII 1284 have high X-ray luminosity and soft X-ray spectra. HII 1284 has X-ray properties comparable to nonflaring K-type stars. Since all five stars are visual or spectroscopic binaries with X-ray properties similar to F-G stars, the late-type binary companions are probably producing the observed coronal X-ray emission. Strengthening this conclusion is the nondetection by Chandra of two A stars, HII 1362 (A7, no known companion) and HII 1375 (A0+A SB) with X-ray luminosity upper limits 27-54 times smaller than HII 980 and HII 956, the B6-A7 stars with cooler companions. Despite the low number statistics, the Chandra data appear to confirm the expectation that late B and A stars are not strong intrinsic X-ray sources. The ACIS spectra and hardness ratios suggest a gradual increase in coronal temperature with decreasing mass from F4 to K. M stars appear to have somewhat cooler coronae than active K stars.

Daniel, Kathryne J.; Linsky, Jeffrey L.; Gagné, Marc

2002-10-01

400

Non-local-thermodynamical-equilibrium effects in the x-ray emission of radiatively heated materials of different atomic numbers.  

PubMed

X-ray self-emission of radiatively heated materials with different values of Z has been investigated. Thin foils were uniformly heated by a 120-eV Hohlraum radiation of 400-ps duration in order to study the self-emission of a homogeneous, optically thin material. The x-ray emission spectra were followed for more than 2 ns. The spectrally integrated emission shows not only a strong Z dependence, but different temporal behaviors for different values of Z. The lower is the value of Z of the x-ray heated matter, the longer is the duration of self-emission. Theoretical comparison with a hydrocode and FLY post-processing shows a non-local-thermal equilibrium behavior caused by direct photoionization due to the thermal pumping radiation, which has a higher brightness temperature than the matter temperature of the heated material. PMID:11461413

Földes, I B; Eidmann, K; Veres, G; Bakos, J S; Witte, K

2001-06-26