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1

The Quiescent Emission Spectrum of Centaurus X-4 and Other X-Ray Transients Containing Neutron Stars  

Microsoft Academic Search

We use the observed optical-UV and X-ray emission spectrum of Cen X-4 during quiescence to constrain models for the accretion flow in this system. We argue that the optical-UV emission is not due to an optically thick quiescent accretion disk, nor due to synchrotron emission from an advection-dominated accretion flow (ADAF). Emission from the bright spot could account for the

Kristen Menou; Jeffrey E. McClintock

2001-01-01

2

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

NASA Astrophysics Data System (ADS)

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 strongly absorbed with an \

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

2002-10-01

3

THE VARIABLE QUIESCENT X-RAY EMISSION OF THE TRANSIENT NEUTRON STAR XTE J1701-462  

SciTech Connect

We present the results of continued monitoring of the quiescent neutron star low-mass X-ray binary XTE J1701-462 with Chandra and Swift. A new Chandra observation from 2010 October extends our tracking of the neutron star surface temperature from {approx_equal}800 days to {approx_equal}1160 days since the end of an exceptionally luminous 19 month outburst. This observation indicates that the neutron star crust may still be slowly cooling toward thermal equilibrium with the core; another observation further into quiescence is needed to verify this. The shape of the overall cooling curve is consistent with that of a broken power law, although an exponential decay to a constant level cannot be excluded with the present data. To investigate possible low-level activity, we conducted a monitoring campaign of XTE J1701-462 with Swift during 2010 April-October. Short-term flares-presumably arising from episodic low-level accretion-were observed up to a luminosity of {approx}1 x 10{sup 35} erg s{sup -1}, {approx}20 times higher than the normal quiescent level. We conclude that flares of this magnitude are not likely to have significantly affected the equilibrium temperature of the neutron star and are probably not able to have a measurable impact on the cooling curve. However, it is possible that brighter and longer periods of low-level activity have had an appreciable effect on the equilibrium temperature.

Fridriksson, Joel K. [Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Homan, Jeroen [MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Wijnands, Rudy; Altamirano, Diego; Degenaar, Nathalie [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Cackett, Edward M. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Brown, Edward F. [Department of Physics and Astronomy, Michigan State University, 3250 Biomedical and Physical Sciences Building, East Lansing, MI 48824 (United States); Mendez, Mariano [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands); Belloni, Tomaso M., E-mail: joelkf@mit.edu [INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (Italy)

2011-08-01

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

The long-term evolution of the X-ray pulsar XTE J1814-338: A receding jet contribution to the quiescent optical emission?  

NASA Astrophysics Data System (ADS)

Aims: We present a study of the quiescent optical counterpart of the accreting millisecond X-ray pulsar XTE J1814-338 that is aimed at unveiling the different components, which contribute to the quiescent optical emission of the system. Methods: We carried out multiband (BVR) orbital phase-resolved photometry of the system using the ESO Very Large Telescope (VLT) that is equipped with the FORS2 camera, covering about 70% of the 4.3 hour orbital period. Results: The optical light curves are consistent with a sinusoidal variability that are modulated with an orbital period with a semi-amplitude of 0.5-0.7 mag. They show evidence of a strongly irradiated companion star, which agrees with previous findings for this system. However, the observed colours cannot be accounted for by the companion star alone, suggesting the presence of an accretion disc during quiescence. The system seems to be fainter in all analysed bands compared to previous observations. The R band light curve displays a possible phase offset with respect to the B and V band. Through a combined fit of the multi-band light curve performed with a Markov chain Monte Carlo technique, we derive constraints on the companion star, disc fluxes, system distance, and companion star mass. Conclusions: The irradiation luminosity required to account for the observed day-side temperature of the companion star is consistent with the spin-down luminosity of a millisecond radio pulsar. Compared to our data with previous observations, which were collected over 5 years, the flux decrease and spectral evolution of the observed quiescent optical emission cannot be satisfactorily explained with the combined contribution of an irradiated companion star and of an accretion disc alone. The observed progressive flux decrease as the system gets bluer could be due to a continuum component that evolves towards a lower, bluer spectrum. While most of the continuum component is likely due to the disc, we do not expect it to become bluer in quiescence. Hence, we hypothesize that an additional component, such as synchrotron emission from a jet was significantly contributing in the data obtained earlier during quiescence and then progressively fading or moving its break frequency towards longer wavelengths. Based on observations made with ESO Telescopes at the Paranal Observatory under programme ID 383.D-0730(A).

Baglio, M. C.; D'Avanzo, P.; Muñoz-Darias, T.; Breton, R. P.; Campana, S.

2013-11-01

6

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

7

A Deep Radio Survey of Hard State and Quiescent Black Hole X-Ray Binaries  

NASA Astrophysics Data System (ADS)

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-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 ?Jy beam-1. None of the three sources were detected to 3? upper limits of 8.3, 7.8, and 14.2 ?Jy beam-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.; Jonker, P. G.; Maccarone, T. J.; Nelemans, G.; Calvelo, D. E.

2011-09-01

8

a Search for X-Ray Jets in Quiescent Microquasars  

NASA Astrophysics Data System (ADS)

Although relativistic jets are present in AGN, Galactic compact objects (called microquasars) and probably gamma-ray bursts, their production and basic properties are not well-understood. Using Chandra, we have discovered extended X-ray jet emission from the black hole X-ray transient and microquasar XTE J1550-564. Based on the behavior of XTE J1550-564, we believe it is likely that X-ray jets are present for other transient microquasars in quiescence, and we propose to observe V4641 Sgr, XTE J1859+226 and CI Cam for 25 ks each with the goal of detecting X-ray jets.

Tomsick, John

2002-09-01

9

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

10

The quiescent X-ray spectrum of accreting black holes  

NASA Astrophysics Data System (ADS)

The quiescent state is the dominant accretion mode for black holes on all mass scales. Our knowledge of the X-ray spectrum is limited due to the characteristic low luminosity in this state. Herein, we present an analysis of the sample of dynamically confirmed stellar-mass black holes observed in quiescence in the Chandra/XMM-Newton/Suzaku era resulting in a sample of eight black holes with ˜570 ks of observations. In contrast to the majority of active galactic nuclei where observations are limited by contamination from diffuse gas, the stellar-mass systems allow for a clean study of the X-ray spectrum resulting from the accretion flow alone. The data are characterized using simple models. We find a model consisting of a power law or thermal bremsstrahlung to both provide excellent descriptions of the data, where we measure ? = 2.06 ± 0.03 and kT = 5.03^{+0.33}_{-0.31} keV, respectively, in the 0.3-10 keV bandpass, at a median luminosity of Lx ˜ 5.5 × 10-7LEdd. This result in discussed in the context of our understanding of the accretion flow on to stellar and supermassive black holes at low luminosities.

Reynolds, Mark T.; Reis, Rubens C.; Miller, Jon M.; Cackett, Edward M.; Degenaar, Nathalie

2014-07-01

11

The Quiescent Counterpart of the Peculiar X-Ray Burster SAX J2224.9+5421  

NASA Astrophysics Data System (ADS)

SAX J2224.9+5421 is an extraordinary neutron star low-mass X-ray binary. It was discovered when it was exhibiting a ~= 10 s long thermonuclear X-ray burst, but it had faded to a 0.5-10 keV luminosity of L X <~ 8 × 1032(D/7.1 kpc)2 erg s-1 only ~= 8 hr later. It is generally assumed that neutron stars are quiescent (i.e., not accreting) at such intensity, raising questions about the trigger conditions of the X-ray burst and the origin of the faint persistent emission. We report on a sime51 ks XMM-Newton observation aimed at finding clues explaining the unusual behavior of SAX J2224.9+5421. We identify a likely counterpart that is detected at L X ~= 5 × 1031(D/7.1 kpc)2 erg s-1 (0.5-10 keV) and has a soft X-ray spectrum that can be described by a neutron star atmosphere model with a temperature of kT ? ~= 50 eV. This would suggest that SAX J2224.9+5421 is a transient source that was in quiescence during our XMM-Newton observation and experienced a very faint (ceasing) accretion outburst at the time of the X-ray burst detection. We consider one other potential counterpart that is detected at L X ~= 5 × 1032(D/7.1 kpc)2 erg s-1 and displays an X-ray spectrum that is best described by a power law with a photon index of ? ~= 1.7. Similarly hard X-ray spectra are seen for a few quiescent neutron stars and may be indicative of a relatively strong magnetic field or the occurrence of low-level accretion.

Degenaar, N.; Wijnands, R.; Miller, J. M.

2014-05-01

12

Hard X-Ray Emission of X-Ray Bursters  

NASA Technical Reports Server (NTRS)

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

Kaaret, P.

1999-01-01

13

Hard X-Ray Emission of X-Ray Bursters.  

National Technical Information Service (NTIS)

The main results from this investigation were serendipitous. The long observation approved for the study of the hard X-ray emission of X-ray bursters lead, instead, to one of the largest early samples of the behavior of fast quasi-periodic oscillations (Q...

P. Kaaret

1997-01-01

14

Emission lines from X ray binaries  

NASA Technical Reports Server (NTRS)

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

Kallman, T. R.

1989-01-01

15

Elemental abundances and temperatures of quiescent solar active region cores from X-ray observations  

NASA Astrophysics Data System (ADS)

A brief review of studies of elemental abundances and emission measures in quiescent solar active region cores is presented. Hinode EUV Imaging Spectrometer (EIS) observations of strong iron spectral lines have shown sharply peaked distributions around 3 MK. EIS observations of lines emitted by a range of elements have allowed good estimates of abundances relative to iron. However, X-ray observations are required to measure the plasma emission above 3 MK and the abundances of oxygen and neon. We revisit, using up-to-date atomic data, older X-ray observations obtained by a sounding rocket and by the Solar Maximum Mission (SMM) Flat Crystal Spectrometer (FCS). We find that the Fe/O and Fe/Ne ratios are normally increased by a factor of 3.2, compared to the photospheric values. Similar results are obtained from FCS observations of six quiescent active region cores. The FCS observations also indicate that the emission measure above 3 MK has a very steep negative slope, with very little plasma observed at 5 MK or above. Appendix A is available in electronic form at http://www.aanda.org

Del Zanna, G.; Mason, H. E.

2014-05-01

16

The Hard Quiescent Spectrum of the Neutron Star X-Ray Transient EXO 1745-248 in the Globular Cluster Terzan 5  

NASA Astrophysics Data System (ADS)

We present a Chandra observation of the globular cluster Terzan 5 during times when the neutron star X-ray transient EXO 1745-248 located in this cluster was in its quiescent state. We detected the quiescent system with a (0.5-10 keV) luminosity of ~2×1033 ergs s-1. This is similar to several other neutron-star transients observed in their quiescent states. However, the quiescent X-ray spectrum of EXO 1745-248 was dominated by a hard power-law component instead of the soft component that usually dominates the quiescent emission of other neutron star X-ray transients. This soft component could not conclusively be detected in EXO 1745-248, and we conclude that it contributed at most 10% of the quiescent flux in the energy range 0.5-10 keV. EXO 1745-248 is only the second known neutron-star transient whose quiescent spectrum is dominated by the hard component (SAX J1808.4-3658 is the other one). We discuss possible explanations for this unusual behavior of EXO 1745-248, its relationship to other quiescent neutron-star systems, and the impact of our results on understanding quiescent X-ray binaries. We also discuss the implications of our results on the way that the low-luminosity X-ray sources in globular clusters are classified.

Wijnands, Rudy; Heinke, Craig O.; Pooley, David; Edmonds, Peter D.; Lewin, Walter H. G.; Grindlay, Jonathan E.; Jonker, Peter G.; Miller, Jon M.

2005-01-01

17

Charge-Exchange X-Ray Emission  

Microsoft Academic Search

Soft X-ray emission due to charge exchange (CX) between solar wind highly charged ions and atoms and molecules has recently been recognized to occur in a number of solar system objects. Here I present measurements and modelling of CX X-ray emission around comets, planets, and within the heliosphere (the cavity carved by the solar wind in the interstellar medium). This

Rosine Lallement

2007-01-01

18

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

19

THE X-RAY POLARIZATION SIGNATURE OF QUIESCENT MAGNETARS: EFFECT OF MAGNETOSPHERIC SCATTERING AND VACUUM POLARIZATION  

SciTech Connect

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 {approx}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.

Fernandez, Rodrigo; Davis, Shane W. [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)

2011-04-01

20

X-ray line emission from Capella  

NASA Technical Reports Server (NTRS)

X-ray emission-line components from Mg, Si, S, and Fe are unambiguously detected from Capella with the solid-state spectrometer onboard the Einstein Observatory. The X-ray spectrum is inconsistent with an isothermal corona, and requires components between 6-million K and at least 24-million K for an adequate fit. An inhomogeneous corona in which the X-ray emitting plasma is confined to magnetically contained loops appears to be reconcilable with all of the experimental evidence.

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

1979-01-01

21

A Deep Radio Survey of Hard State and Quiescent Black Hole X-Ray Binaries  

Microsoft Academic Search

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-1. All 11 quiescent systems were not

J. C. A. Miller-Jones; P. G. Jonker; T. J. Maccarone; G. A. Nelemans; D. E. Calvelo

2011-01-01

22

X-ray emission from superbubbles  

NASA Technical Reports Server (NTRS)

The results of Rosat observations of superbubbles in the Large Magellanic Cloud provided X-ray spectra for bright objects and data on upper limits of faint objects. The X-ray emission from superbubbles can be used to determine the physical condition of the superbubble interior, place constraints on the ambient interstellar medium, and diagnose the existence of supernova remnant shocks.

Chu, You-Hua; MacLow, Mordecai-Mark

1996-01-01

23

X-Ray Emission from Centaurus A.  

National Technical Information Service (NTIS)

Observations of 3 to 12 keV x-ray emission from NGC 5128 (Cen A) were made by Vela spacecraft over the period 1969 to 1979. These data are in good agreement with previously reported data, but are much more complete. Numerous peaks of x-ray intensity occur...

N. J. Terrell

1981-01-01

24

Properties of X ray emission from X ray novae  

NASA Astrophysics Data System (ADS)

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

Kitamoto, Shunji

1993-05-01

25

Quiescent accretion disks in black hole X-ray novae  

NASA Technical Reports Server (NTRS)

We present detailed time-resolved spectroscopy of the Balmer emission lines from two black hole binary systems in quiescence, A0620-00 and Nova Muscae 1991. We find extraordinary similarities between the two systems. There are 30-40 km/s velocity variations of the emission lines over the orbital period, the phases of which are not aligned with the expected phase of the motion of the compact primary. Detailed modeling of both systems is complicated by variable hot spot components, regions of optical thickness, and intermittent excess emission in the blue line wings of the H-alpha lines. Both sources also display low velocities at the outer edge of the accretion disk, implying a large primary Roche lobe and extreme mass ratios. These complications suggest that although simple optically thin, Keplerian alpha-disk models provide a useful parameterization of emission lines from these systems, the straightforward physical models they imply should be treated with great caution.

Orosz, Jerome A.; Bailyn, Charles D.; Remillard, Ronald A.; Mcclintock, Jeffrey E.; Foltz, Craig B.

1994-01-01

26

X-ray emission from Centaurus A  

SciTech Connect

Observations of 3 to 12 keV x-ray emission from NGC 5128 (Cen A) were made by Vela spacecraft over the period 1969 to 1979. These data are in good agreement with previously reported data, but are much more complete. Numerous peaks of x-ray intensity occurred during the period 1973 to 1975, characterized by rapid increases and equally rapid decreases (in less than 10 days). Thus it seems probable that most of the x-ray flux from the nucleus of Cen A came from a single source of small size.

Terrell, N.J.

1981-01-01

27

The X-ray emission of galaxies  

NASA Technical Reports Server (NTRS)

Results from several satellite observations are used to discuss the discrete emission component of galaxies, including bright binary sources, supernova and supernova remnants. Through X-ray observations, direct evidence of the chemical and dynamical interactions between galaxies and the surrounding medium can be obtained. Although the X-ray emission represents only a small fraction of the bolometric emission of a normal galaxy, it allows the study of the system's component to be performed. The results on low luminosity active galactic nuclei are also discussed.

Fabbiano, G.

1996-01-01

28

X-ray driven gamma emission  

NASA Astrophysics Data System (ADS)

X-ray driven gamma emission describes processes that may release nuclear energy in a 'clean' way, as bursts of incoherent or coherent gamma rays without the production of radioactive by-products. Over the past decade, studies in this area have gained tremendous momentum. X-ray triggered gamma emission from long-lived metastable nuclear excited states has been established since 1987 for one nuclide and it appears likely that triggering in other isotopes will be demonstrated conclusively in the near future. With these experimental results have come new proposals for the creation of collective and avalanche-like incoherent gamma-ray bursts and even for the ultimate light source, a gamma-ray laser. Obviously, many applications would benefit from controlled bursts of gamma radiation, whether coherent or not. This talk reviews the experimental results and concepts for the production of gamma rays, driven by externally produced x rays.

Carroll, James

2002-04-01

29

X-Ray Emission From Hybrid Stars  

NASA Astrophysics Data System (ADS)

Hybrid stars are giant stars that exhibit both chromospheric emission features and signatures of mass outflow, and hence provide a link between stars on either side of the ``Coronal Dividing Line". We have obtained long duration ROSAT PSPC exposures of two nearby hybrid stars (alpha TrA and iota Aur), and here, we compare these observations with models of X-ray emission on giant stars.

Kashyap, V.; Rosner, R.; Harnden, F. R., Jr.; Maggio, A.

1993-05-01

30

X-ray induced electron emission  

Microsoft Academic Search

The development and use of a magnetic spectrograph for the measurement of X-ray induced electron emission is described. Results are presented for metal and dielectric targets ranging in atomic number from Z=6 to Z-82. Materials studied were lead, tantalum, copper, aluminum, magnesium, solar cell cover glass, silica cloth, thermal control paint, Kevlar, Mylar, and conducting\\/nonconducting epoxy. Direct measurement was made

C. A. Aeby

1982-01-01

31

X-ray induced electron emission  

NASA Astrophysics Data System (ADS)

The development and use of a magnetic spectrograph for the measurement of X-ray induced electron emission is described. Results are presented for metal and dielectric targets ranging in atomic number from Z=6 to Z-82. Materials studied were lead, tantalum, copper, aluminum, magnesium, solar cell cover glass, silica cloth, thermal control paint, Kevlar, Mylar, and conducting/nonconducting epoxy. Direct measurement was made of the quantum yield and energy distribution of electrons emitted at angles of 0 deg, 30 deg, 45 deg and 60 deg with respect to the surface normal of targets exposed to normal incidence filtered and unfiltered 50 kV bremsstrah lung X-rays. Experimental results are compared with previous measurements where possible, and with computer code predictions where predictive capability matches the measurement range. The experimental results corroborates the cos theta angular dependence predicted by simple theoretical models, particularly for medium and high Z materials. A trend toward isotropic emission distribution is noted for the lower Z materials. Compared to the measured results, the emission yields predicted by a commonly used analytical model are low by approximately a factor of 2 for the unfiltered X-ray spectrum.

Aeby, C. A.

1982-04-01

32

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

33

A Test for the Anisotropy of X-ray Emission from Ultraluminous X-ray Sources  

NASA Astrophysics Data System (ADS)

If the emission from ultraluminous X-ray sources (ULX) is anisotropic, the luminosities can be less than the Eddington Luminosity for a 15 Msun black hole (2x1039 erg/s), obviating the need for intermediate mass black holes. We can test the isotropy condition because a fraction of the X-ray emission is absorbed by cold material, and much of this absorbed power will be reemitted isotropically by dust grains at infrared wavelengths. The ratio of the infrared luminosity to the absorbed X-ray luminosity is a measure of the anisotropy of the X-ray emission. We failed to detect infrared emission from the ULX in NGC 1313 using observations obtained with the IRAC and MIPS instruments on the Spitzer Observatory. The upper limit to the infrared power is well below the value expected if the X-ray emission is isotropic. If our model for the conversion of absorbed X-ray photons to dust reemission is correct, the inferred opening angle of the X-ray emission is less than 30 degrees, implying that the intrinsic X-ray luminosity is less than 2x1039 erg/s.

Bregman, Joel Norman; Miller, J. M.; Irwin, J. A.

2007-12-01

34

Hard X-ray emission from neutron star X-ray binaries  

Microsoft Academic Search

In this paper we review our current knowledge of the hard X–ray emission properties of accreting X–ray Binary Pulsars and old accreting neutron stars in Low Mass X–ray Binaries in light of 7 years of BeppoSAX and RXTE observations. The paper is divided in two parts. In the first part we review the more recent findings on the phase-dependent broad

T. Di Salvo; A. Santangelo; A. Segreto

2004-01-01

35

X-Ray Emission from "Uranium" Stars  

NASA Technical Reports Server (NTRS)

The project aims to secure XMM observations of two targets with extremely low abundances of the majority of heavy elements (e.g., log[Fe/H] $\\sim$-4), but that show absorption lines of uranium. The presence of an r-process element such as uranium requires a binary star system in which the companion underwent a supernova explosion. A binary star system raises the distinct possibility of the existence of a compact object, most likely a neutron star, in the binary, assuming it survived the supernova blast. The presence of a compact object then suggests X-ray emission if sufficient matter accretes to the compact object. The observations were completed less than one year ago following a series of reobservations to correct for significant flaring that occurred during the original observations. The ROSAT all-sky survey was used to report on the initial assessment of X-ray emission from these objects; only upper limits were reported. These upper limits were used to justify the XMM observing time, but with the expectation that upper limits would merely be pushed lower. The data analysis hinges critically on the quality and degree of precision with which the background is handled. During the past year, I have spent some time learning the ins and outs of XMM data analysis. In the coming year, I can apply that learning to the analysis of the 'uranium' stars.

Schlegel, Eric; Mushotzky, Richard (Technical Monitor)

2005-01-01

36

X-Ray-Driven Gamma Emission  

NASA Astrophysics Data System (ADS)

X-ray-driven gamma emission describes processes that may release nuclear energy in a ‘clean’ way, as bursts of incoherent or coherent gamma rays without the production of radioactive by-products. Over the past decade, studies in this area, as a part of the larger field of quantum nucleonics, have gained tremendous momentum. Since 1987 it has been established that photons could trigger gamma emission from a long-lived metastable nuclear excited state of one nuclide and it appears likely that triggering in other isotopes will be demonstrated conclusively in the near future. With these experimental results have come new proposals for the creation of collective and avalanche-like incoherent gamma-ray bursts and even for the ultimate light source, a gamma-ray laser. Obviously, many applications would benefit from controlled bursts of gamma radiation, whether coherent or not. This paper reviews the experimental results and concepts for the production of gamma rays, driven by externally produced X-rays.

Carroll, J. J.; Karamian, S. A.; Rivlin, L. A.; Zadernovsky, A. A.

2001-07-01

37

Jet-dominated quiescent states in black hole X-ray binaries: the case of V404 Cyg  

NASA Astrophysics Data System (ADS)

The dynamical structure and radiative properties of the quiescent state (X-ray luminosity ?1034 erg s-1) of black hole X-ray transients (BHXTs) remain unclear, mainly because of low luminosity and poor data quantity. We demonstrate that the simultaneous multi-wavelength (including radio, optical, ultraviolet and X-ray bands) spectrum of V404 Cyg in its bright quiescent state can be well described by the radiation from the companion star and more importantly, the compact jet. Neither the outer thin disc nor the inner hot accretion flow is important in the total spectrum. Together with recent findings, i.e. the power-law X-ray spectrum and the non-variable X-ray spectral shape (or constant photon index) in contrast to the dramatic change in the X-ray luminosity, we argue the quiescent state spectrum of BHXTs is actually jet-dominated. Additional observational properties consistent with this jet model are also discussed as supporting evidence.

Xie, Fu-Guo; Yang, Qi-Xiang; Ma, Renyi

2014-07-01

38

Hard X-Ray Emission Associated with White Dwarfs  

NASA Astrophysics Data System (ADS)

Inspired by the hard X-ray emission from WD 2226-210, the central star of the Helix Nebula, we have made a systematic search for similar sources by correlating the white dwarf catalog of McCook & Sion and the ROSAT Position Senstive Proportional Counter (PSPC) point-source catalog of White, Giommi, & Angelini. We find 76 white dwarfs coincident with X-ray sources at a high level of confidence. Among these sources, 17 show significant hard X-ray emission at energies greater than 0.5 keV. Twelve of these white dwarfs with hard X-ray emission are in known binary systems, in two of which the accretion of the close companion's material onto the white dwarf produces hard X-ray emission, and in the other 10 the late-type companions' coronal activity emits hard X-rays. One apparently single white dwarf is projected near an active galactic nucleus that is responsible for the hard X-ray emission. The remaining four white dwarfs and two additional white dwarfs with hard X-ray emission appear single. The lack of near-IR excess from the apparently single white dwarfs suggests that either X-ray observations are more effective than near-IR photometry in diagnosing faint companions, or a different emission mechanism is needed. It is intriguing that 50% of the six apparently single white dwarfs with hard X-ray emission are among the hottest white dwarfs. We have compared X-ray properties of 11 hot white dwarfs with different spectral types and conclude that stellar pulsation and fast stellar winds are not likely the origin of the hard X-ray emission, but a leakage of the high-energy Wien tail of emission from deep in the stellar atmosphere remains a tantalizing source of hard X-ray emission from hot DO and DQZO white dwarfs. A complete survey using the entire ROSAT PSPC archive is needed to enlarge the sample of white dwarfs with hard X-ray emission. Follow-up near-IR photometric observations are needed to verify the existence of late-type companions, and high-resolution deep X-ray observations are needed to verify the positional coincidence and to study the X-ray spectral properties in order to determine the origin and nature of the hard X-ray emission.

O'Dwyer, Ian J.; Chu, You-Hua; Gruendl, Robert A.; Guerrero, Martín A.; Webbink, Ronald F.

2003-04-01

39

X-Ray Emission from Young Brown Dwarfs in the Orion Nebula Cluster  

NASA Astrophysics Data System (ADS)

We use the sensitive X-ray data from the Chandra Orion Ultradeep Project (COUP) to study the X-ray properties of 34 spectroscopically identified brown dwarfs with near-infrared spectral types between M6 and M9 in the core of the Orion Nebula Cluster. Nine of the 34 objects are clearly detected as X-ray sources. The apparently low detection rate is in many cases related to the substantial extinction of these brown dwarfs; considering only the brown dwarfs with AV<=5 mag, nearly half of the objects (7 out of 16) are detected in X-rays. Our 10 day long X-ray light curves of these objects exhibit strong variability, including numerous flares. While one of the objects was only detected during a short flare, a statistical analysis of the light curves provides evidence for continuous (``quiescent'') emission in addition to flares for all other objects. Of these, the ~M9 brown dwarf COUP 1255 (=HC 212) is one of the coolest known objects with a clear detection of quiescent X-ray emission. The X-ray properties (spectra, fractional X-ray luminosities, flare rates) of these young brown dwarfs are similar to those of the low-mass stars in the Orion Nebula Cluster, and thus there is no evidence for changes in the magnetic activity around the stellar/substellar boundary, which lies at ~M6 for Orion Nebula Cluster sources. Since the X-ray properties of the young brown dwarfs are also similar to those of M6-M9 field stars, the key to the magnetic activity in very cool objects seems to be the effective temperature, which determines the degree of ionization in the atmosphere.

Preibisch, Thomas; McCaughrean, Mark J.; Grosso, Nicolas; Feigelson, Eric D.; Flaccomio, Ettore; Getman, Konstantin; Hillenbrand, Lynne A.; Meeus, Gwendolyn; Micela, Giusi; Sciortino, Salvatore; Stelzer, Beate

2005-10-01

40

Neutron Star Masses and Radii from Quiescent Low-mass X-Ray Binaries  

NASA Astrophysics Data System (ADS)

We perform a systematic analysis of neutron star radius constraints from five quiescent low-mass X-ray binaries and examine how they depend on measurements of their distances and amounts of intervening absorbing material, as well as their assumed atmospheric compositions. We construct and calibrate to published results a semi-analytic model of the neutron star atmosphere which approximates these effects for the predicted masses and radii. Starting from mass and radius probability distributions established from hydrogen-atmosphere spectral fits of quiescent sources, we apply this model to compute alternate sets of probability distributions. We perform Bayesian analyses to estimate neutron star mass-radius curves and equation of state (EOS) parameters that best-fit each set of distributions, assuming the existence of a known low-density neutron star crustal EOS, a simple model for the high-density EOS, causality, and the observation that the neutron star maximum mass exceeds 2 M ?. We compute the posterior probabilities for each set of distance measurements and assumptions about absorption and composition. We find that, within the context of our assumptions and our parameterized EOS models, some absorption models are disfavored. We find that neutron stars composed of hadrons are favored relative to those with exotic matter with strong phase transitions. In addition, models in which all five stars have hydrogen atmospheres are found to be weakly disfavored. Our most likely models predict neutron star radii that are consistent with current experimental results concerning the nature of the nucleon-nucleon interaction near the nuclear saturation density.

Lattimer, James M.; Steiner, Andrew W.

2014-04-01

41

Looking for Periodicity in X-Ray Emission Data  

NASA Astrophysics Data System (ADS)

X-Ray Binaries are systems in which matter falling from one component of the system to the other releases energy in the form of X-Rays. We created an algorithm which uses Pearson’s Chi-Squared test to look for periodicity in X-Ray emission data from NASA’s Swift Burst Alert Telescope (BAT) 58-Month Hard X-Ray Survey. We use the known High Mass X-Ray Binary J1647.9-4511B to test our program over a range of periods, bins and energy bands and verify the true period. Results are discussed.

Cuellar, Andres; Cohen, S.; Benacquista, M.

2014-01-01

42

Small GOES flares with intense hard X-ray emission  

NASA Astrophysics Data System (ADS)

Large solar flares with intense soft X-ray emission (i.e., high GOES class) generally tend to show a strong hard X-ray emission. However, there are examples of low GOES class events with unusually strong hard X-ray emission. In this paper, we analyse the morphology and physical parameters of such small GOES intensity flares with strong hard X-ray emission, using Yohkoh SXT images and photometric data obtained from INTERBALL-TAIL RF15-I X-ray Photometer. We observe a great variety in the soft X-ray morphology of such flares (a large diversity of loop configurations). Some of these flares do not differ greatly in their morphology from large intense flares, but most flares are generally compact. In spite of their low intensities in soft X-rays, the significant hard X-ray emission is observed by INTERBALL up to 30 60 keV. We briefly discuss some of the possible causes of the soft and hard X-ray emission ratio of these events.

Siarkowski, M.; Falewicz, R.; Berlicki, A.

2006-01-01

43

Confirmation of IGR J01363 plus 6610 as a Be X-Ray Binary with Very Low Quiescent X-Ray Luminosity  

NASA Technical Reports Server (NTRS)

The field containing the candidate High Mass X-ray Binary IGR J01 363+6610 was observed by XMM-Newton on 2009 July 31 for 28 ks. A Be star was previously suggested as the possible counterpart of the INTEGRAL source, and although Chandra, during a 2007 observation, did not detect an X-ray source at the position of the Be star, we find a variable source (XMMU 101 3549.5+661243) with an average X-ray flux of 2 x 10(exp -13)ergs/sq cm/s (0.2-12 keV, unabsorbed) at this position with XMM-Newton. The spectrum of this source is consistent with a hard power law with a photon index of r = 1.4+/-0.3 and a column density of N(sub H) = (15(+0.7/-0.5)) x 10(exp 22)/sq cm (90% confidence errors). These results, along with our optical investigation of other X-ray sources in the field, make the association with the Be star very likely, and the 2 kpc distance estimate for the Be star indicates an X-ray luminosity of 9.1 x 10(exp 31) ergs/s. This is lower than typical for a Be X-ray binary, and the upper limit on the luminosity was even lower ( < 1.4 x 10(exp 3)ergs/s assuming the same spectral model) during the Chandra observation. We discuss possible implications of the very low quiescent luminosity for the physical properties of IGR 101363+6610.

Tomsick, John A.; Heinke, Craig; Halpern, Jules; Kaaret, Philip; Chaty, Sylvain; Rodriguez, Jerome; Bodaghee, Arash

2011-01-01

44

EXTENDED X-RAY EMISSION FINE STRUCTURE (EXEFS) AND X-RAY ABSORPTION NEAR EDGE STRUCTURE (XANES) OF SOIL SAMPLES  

Microsoft Academic Search

Silicon K X-ray fluorescence spectra of soil samples in a volcano island are measured using a commercially available wavelength dispersive X-ray fluorescence spectrometer for elemental analysis. EXEFS (extended X-ray emission fine structure) are found at the low energy side of the K X-ray fluorescence diagram lines. Synchrotron radiation XANES (X-ray absorption near edge structure) spectra are measured for the same

Jun Kawai; Susumu Tohno

2001-01-01

45

X-ray emission from magnetic cataclysmic variables  

NASA Astrophysics Data System (ADS)

I present a brief review of the present status of X-ray emission from Magnetic Cataclysmic Variables (MCVs). A short introduction to the types of Cataclysmic Variables (CVs) is followed by a presentation of some of the properties of the two types of MCVs - Polars and Intermediate Polars (IPs) as seen in X-rays. Finally X-ray spectra of MCVs and future prospects of their studies are discussed.

Singh, K. P.

46

X-ray emission from high temperature plasmas  

NASA Technical Reports Server (NTRS)

The physical processes occurring in plasma focus devices were investigated with particular emphasis on X-ray emission. Topics discussed include: trajectories of high energy electrons; detection of ion trajectories; spatial distribution of neutron emission; space and time resolved emission of hard X-rays from a plasma focus; the staged plasma focus as a variation of the hypocloidal pinch; formation of current sheets in a staged plasma focus; and X-ray and neutron emission from a staged plasma focus. The possibility of operating dense plasma-focus type devices in multiple arrays beyond the scaling law for a single gun is discussed.

Harries, W. L.

1977-01-01

47

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

48

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

49

Characterizing the quiescent X-ray variability of the black hole low-mass X-ray binary V404 Cyg  

NASA Astrophysics Data System (ADS)

We conducted the first long-term (75 d) X-ray monitoring of the black hole low-mass X-ray binary V404 Cyg, with the goal of understanding and characterizing its variability during quiescence. The X-ray light curve of V404 Cyg shows several flares on time-scales of hours with a count rate change of a factor of about 5-8. The root-mean-square variability is Fvar = 57.0 ± 3.2 per cent. The first-order structure function is consistent with both a power spectrum of index -1 (flicker noise), or with a power spectrum of index 0 (white noise), implying that the light curve is variable on time-scales from days to months. The X-ray spectrum is well fitted by a power law with spectral index ? = 2.10-2.35, and we found that the spectral shape remains roughly constant as the flux changes. A constant spectral shape with respect to a change in the X-ray flux may favour a scenario in which the X-ray emission is dominated by synchrotron radiation produced in a jet.

Bernardini, F.; Cackett, E. M.

2014-04-01

50

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

51

X-Ray Emission from Centaurus A.  

National Technical Information Service (NTIS)

The X-ray strength of Cen A (NGC 5128) was monitored for 10 years by Vela 5B, beginning in 1979. The 1973 to 1975 period of exceptional activity and strength was especially well covered, and was characterized by numerous rapid changes in intensity, in agr...

J. Terrell

1984-01-01

52

Understanding X-ray reflection emissivity profiles in AGN: locating the X-ray source  

NASA Astrophysics Data System (ADS)

The illumination pattern (or emissivity profile) of the accretion disc due to the reflection of X-rays in active galactic nucleus can be understood in terms of relativistic effects on the rays propagating from a source in a corona surrounding the central black hole, both on their trajectories and on the accretion disc itself. Theoretical emissivity profiles due to isotropic point sources as well as simple extended geometries are computed in general relativistic ray-tracing simulations performed on graphics processing units (GPUs). Such simulations assuming only general relativity naturally explain the accretion disc emissivity profiles determined from relativistically broadened emission lines which fall off steeply (with power-law indices of between 6 and 8) over the inner regions of the disc, then flattening off to almost a constant before tending to a constant power law of index 3 over the outer disc. Simulations for a variety of source locations, extents and geometries show how the emissivity profiles depend on these properties, and when combined with reverberation time lags allow the location and extent of the primary X-ray source to be constrained. Comparing the emissivity profile determined from the broadened iron K emission line in spectra of 1H 0707-495 obtained in 2008 January to theoretical emissivity profiles and applying constraints from reverberation lags suggest that there exists an extended region of primary X-ray emission located as low as 2rg above the accretion disc, extending outwards to a radius of around 30rg.

Wilkins, D. R.; Fabian, A. C.

2012-08-01

53

X-ray emission from Centaurus A  

SciTech Connect

The X-ray strength of Cen A (NGC 5128) was monitored for 10 years by Vela 5B, beginning in 1979. The 1973 to 1975 period of exceptional activity and strength was especially well covered, and was characterized by numerous rapid changes in intensity, in agreement with other data, indicating that the nucleus of Cen A is small but massive. 16 references, 3 figures.

Terrell, J.

1984-01-01

54

X-ray studies of coeval star samples. III. X-ray emission in the Ursa Major stream  

SciTech Connect

Results are reported from a comprehensive survey of X-ray emission from stars known or suspected to be members of the UMa cluster and/or stream. Of the 42 UMa member stars surveyed, 18 were detected as X-ray sources, and spectral analysis was performed for 10 stars with sufficient X-ray counts. Consideration is given to relations between X-ray luminosity, color, and kinematics of the sample stars, and the X-ray spectra of the UMa stars are discussed in the context of the general problem of stellar X-ray temperatures. Also confirmed is the lack of X-ray-emitting A dwarfs among UMa members; among stars of later spectra type there is a rather large dispersion in X-ray luminosity. This dispersion cannot readily be explained by contamination with field star interlopers and appears rather to be a property of the UMa X-ray luminosity distribution function. 43 refs.

Schmitt, J.H.M.M.; Micela, G.; Sciortino, S.; Vaiana, G.S.; Harnden, F.R., Jr. (Max-Planck-Institut fuer Extraterrestrische Physik, Garching (Germany, F.R.) Osservatorio Astronomico, Palermo (Italy) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (USA))

1990-03-01

55

X-ray studies of coeval star samples. III - X-ray emission in the Ursa Major stream  

NASA Technical Reports Server (NTRS)

Results are reported from a comprehensive survey of X-ray emission from stars known or suspected to be members of the UMa cluster and/or stream. Of the 42 UMa member stars surveyed, 18 were detected as X-ray sources, and spectral analysis was performed for 10 stars with sufficient X-ray counts. Consideration is given to relations between X-ray luminosity, color, and kinematics of the sample stars, and the X-ray spectra of the UMa stars are discussed in the context of the general problem of stellar X-ray temperatures. Also confirmed is the lack of X-ray-emitting A dwarfs among UMa members; among stars of later spectra type there is a rather large dispersion in X-ray luminosity. This dispersion cannot readily be explained by contamination with field star interlopers and appears rather to be a property of the UMa X-ray luminosity distribution function.

Schmitt, J. H. M. M.; Micela, G.; Sciortino, S.; Vaiana, G. S.; Harnden, F. R., Jr.

1990-01-01

56

X-Ray Emission from the Guitar Nebula  

NASA Technical Reports Server (NTRS)

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 properties of the postshock flow. The X-ray emission is most easily understood if the shocked pulsar wind is partly confined in the nebula and if magnetic fields in this zone can grow to near-equipartition values.

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

1997-01-01

57

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

58

Hard X-ray emission from eta Carinae  

Microsoft Academic Search

Context: If relativistic particle acceleration takes place in colliding-wind binaries, hard X-rays and gamma-rays are expected through inverse Compton emission, but to date these have never been unambiguously detected. Aims: To detect this emission, observations of eta Carinae were performed with INTEGRAL, leveraging its high spatial resolution. Methods: Deep hard X-ray images of the region of eta Car were constructed

J.-C. Leyder; Roland Walter; Gregor Rauw

2008-01-01

59

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

2013-09-12

60

Be/X-ray binaries emission models probed by LOFT  

NASA Astrophysics Data System (ADS)

LOFT, the Large Observatory For X-ray Timing, is a new space mission concept selected by ESA to compete for a lunch opportunity in the early 2020s. The LOFT payload comprises a Large Area Detector (LAD) and a Wide Field Monitor (WFM), designed to study timing and spectral features in the X-ray emission of bright accreting X-ray sources with an unprecedented large effective area (10 m^{2}) and good spectral resolution (200-300 eV). We show here the results that LOFT will be able to achieve in the study of the Be/X-ray binaries sources, by carrying out detailed spectral and timing simulations with the WFM and the LAD. We will review the most recent observational and theoretical advancements in the field with particular emphasis on the observational constraints on the emission models from the accretion columns that will be accessible by exploiting the LOFT capabilities.

Ferrigno, Carlo; Pottschmidt, Katja; Wilson-Hodge, Colleen; Bozzo, Enrico; Doroshenko, Victor; Santangelo, Andrea; Wilms, Joern

2012-07-01

61

ANS hard X-ray experiment development program. [emission from X-ray sources  

NASA Technical Reports Server (NTRS)

The hard X-ray (HXX) experiment is one of three experiments included in the Dutch Astronomical Netherlands Satellite, which was launched into orbit on 30 August 1974. The overall objective of the HXX experiment is the detailed study of the emission from known X-ray sources over the energy range 1.5-30keV. The instrument is capable of the following measurements: (1) spectral content over the full energy range with an energy resolution of approximately 20% and time resolution down to 4 seconds; (2) source time variability down to 4 milliseconds; (3) silicon emission lines at 1.86 and 2.00keV; (4) source location to a limit of one arc minute in ecliptic latitude; and (5) spatial structure with angular resolution of the arc minutes. Scientific aspects of experiment, engineering design and implementation of the experiment, and program history are included.

Parsignault, D.; Gursky, H.; Frank, R.; Kubierschky, K.; Austin, G.; Paganetti, R.; Bawdekar, V.

1974-01-01

62

Extended X-Ray Emission around Quasars at Intermediate Redshift  

NASA Technical Reports Server (NTRS)

We compare the optical to soft X-ray spectral energy distribution (SED) of a sample of bright low-redshift (0.048 less than z less than 0.155), radio-quiet quasars, with a range of thermal models which have been proposed to explain the optical/UV/soft X-ray quasar emission: (a) optically thin emission from an ionized plasma, (b) optically thick emission from the innermost regions of an accretion disk in Schwarzschild and Kerr geometries. We presented ROSAT PSPC observations of these quasars in an earlier paper. Here our goals are to search for the signature of thermal emission in the quasar SED, and to investigate whether a single component is dominating at different frequencies. We find that isothermal optically thin plasma models can explain the observed soft X-ray color and the mean OUV color. However, they predict an ultraviolet (1325 Angstrom) luminosity a factor of 3 to 10 times lower than observed. Pure disk models, even in a Kerr geometry, do not have the necessary flexibility to account for the observed OUV and soft X-ray luminosities. Additional components are needed both in the optical and in the soft X-rays (e.g. a hot corona can explain the soft X-ray color). The most constrained modification of pure disk models, is the assumption of an underlying power law component extending from the infrared (3 micrometers) to the X-ray. This can explain both the OUV and soft X-ray colors and luminosities and does not exceed the 3 micrometers luminosity, where a contribution from hot dust is likely to be important. We also discuss the possibility that the observed soft X-ray color and luminosity are dominated by reflection from the ionized surface of the accretion disk. While modifications of both optically thin plasma models and pure disk models might account for the observed SED, we do not find any strong evidence that the OUV bump and soft X-ray emission are one and the same component. Likewise, we do not find any strong argument which definitely argues in favor of thermal models.

Fiore, Fabrizio

1998-01-01

63

X-ray emission from colliding laser plasmas  

SciTech Connect

Colliding Au, CD and Ti-Cr plasmas have been generated by illuminating two opposing foils each with a {approximately} 100J, 0.5 nsec, 2{omega} Nd-glass laser beam from the Trident laser facility at Los Alamos. The plasmas are being used to study plasma interactions which span the parameter regime from interpenetrating to collisional stagnation. X-ray emission during the laser target interaction and the subsequent collision is used to diagnose the initial plasma conditions and the colliding plasma properties. X-ray instrumentation consists of a 100 ps gated x-ray pinhole imager, a time-integratcd bremsstrahlung x-ray spectrograph and a gated x-ray spectrograph used to record isoelectronic spectra from the Ti-Cr plasmas. The imager has obtained multi-frame images of the collision and therefore, a measure of the stagnation length which is a function of the ion charge state and density and a strong function of the electron temperature. Other instrumentation includes a Thomson scattering spectrometer with probe beam, neutron detectors used to monitor the CD coated foil collisions and an ion spectrometer. We will describe the current status of the experiments and current results with emphasis on the x-ray emission diagnostics. We will also briefly describe the modeling using Lasnex and ISIS, a particle-in-cell code with massless fluid electrons and inter particle (classical) collisions.

Wilke, M.; Obst, A.W.; Winske, D. [and others

1995-09-01

64

X-ray emission from chemically peculiar stars  

NASA Technical Reports Server (NTRS)

We have searched the Roentgen Satellite (ROSAT) All-Sky Survey (RASS) database at the positions of about 100 magnetic Bp-Ap stars of the helium-strong, helium-weak, silicon, and strontium-chromium subclasses. We detect X-ray sources at the positions of 10 of these stars; in four cases the X-ray emission presumably arises from an early-type companion with a radiatively driven wind, while we believe that the magnetic chemically peculiar (CP) star is the most likely X-ray source (as opposed to a binary companion) in at least three and at most five of the six remaining cases. The helium-strong stars have X-ray emission levels that are characteristic of the luminous OB stars with massive winds (log L(sub x)/L(sub bol) is about -7), whereas the He-weak and Si stars (which generally show no evidence for significant mass loss) have log L(sub x)/L(sub bol) values that can reach as high as about -6. In contrast, we find no convincing evidence that the cooler SrCrEu-type CP stars are intrinsic X-ray sources. We discuss the X-ray and radio emission properties of our sample of CP stars, and argue that both types of emission may be magnetospheric in origin; however, there is clearly not a simple one-to-one correspondence between them, since many of the magnetic stars that are detected radio sources were not detected as X-ray sources in the present survey.

Drake, S. A.; Linsky, J. L.; Schmitt, J. H. M. M.; Rosso, C.

1994-01-01

65

Synchrotron-Radiation Induced X-Ray Emission (SRIXE)  

SciTech Connect

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 x-ray source that has taken place during the past 40 years has had a major impact on the general field of x-ray analysis. Even tier 40 years, science of x-ray analysis with synchrotron x-ray beams is by no means mature. Improvements being made to existing synchrotron facilities and the design and construction of new facilities promise to accelerate the development of the general scientific use of synchrotron x-ray sources for at least the next ten years. The effective use of the synchrotron source technology depends heavily on the use of high-performance computers for analysis and theoretical interpretation of the experimental data. Fortunately, computer technology has advanced at least as rapidly as the x-ray technology during the past 40 years and should continue to do so during the next decade. The combination of these technologies should bring about dramatic advances in many fields where synchrotron x-ray science is applied. It is interesting also to compare the growth and rate of acceptance of this particular research endeavor to the rates for other technological endeavors. Griibler [1997] cataloged the time required for introduction, diffusion,and acceptance of technological, economic, and social change and found mean values of 40 to 50 years. The introduction of the synchrotron source depends on both technical and non-technical factors, and the time scale at which this seems to be occurring is quite compatible with what is seen for other major innovations such as the railroad or the telegraph. It will be interesting to see how long the present rate of technological change and increase in scientific use can be maintained for the synchrotron x-ray source. A short summary of the present state of the synchrotron radiation-induced x-ray emission (SRIXE) method is presented here. Basically, SRIXE experiments can include any that depend on the detection. of characteristic x-rays produced by the incident x-ray beam born the synchrotron source as they interact with a sample. Thus, experiments done to measure elemental composition, chemical state, crystal, structure, and other sample parameters can be considered in a discussion of SRIXE. It is also clear that the experimentalist may well wish to use a variety of complementary techniques for study of a given sample. For this reason, discussion of computed microtomography (CMT) and x-ray diffraction is included here. It is hoped that this present discussion will serve as a succinct introduction to the basic ideas of SRIXE for those not working in the field and possibly help to stimulate new types of work by those starting in the field as well as by experienced practitioners of the art. The topics covered include short descriptions of (1) the properties of synchrotron radiation, (2) a description of facilities used for its production, (3) collimated microprobe, (4) focused microprobes, (5) continuum and monoenergetic excitation, (6) detection limits, (7) quantitation, (8) applications of SRIXE, (9) computed microtomography (CMT), and (10)chemical speciation using x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS). An effort has been made to cite a wide variety of work from different laboratories to show the vital nature of the field.

Jones, Keith W.

1999-09-01

66

X-ray emission from 4U 2129+47 (= V1727 Cygni) in quiescence  

NASA Technical Reports Server (NTRS)

Observations with the ROSAT HRI allow detection of weak X-ray flux from the low-mass X-ray binary (LMXB) 4U 2129+47 during its current quiescent state. The quiescent luminosity is similar to that seen in several other quiescent LMXBs containing neutron stars. The quiescent X-ray light curve may not show the eclipse seen when the source was in its high state, which would indicate that the enhanced vertical structure present in the disk during the high state has collapsed. This in turn provides support for the idea that the vertical structure in LMXB accretion disks is a consequence of high X-ray luminosity. A comparison of the absorption of low-energy X-rays due to the interstellar medium (determined from Einstein IPC observations) and the optical extinction does not rule out the triple system hypothesis.

Garcia, Michael R.

1994-01-01

67

Evidence for X-ray emission from Capella  

NASA Technical Reports Server (NTRS)

X-ray emission in the range from 0.2 to 1.6 keV has been detected from an area of the sky which contains the binary star system Capella. The X-ray source is at most a few arc minutes in extent and shows no spectral turnover at low energy, consistent with a nearby source. We suggest Capella as the source of this emission and that this object belongs to a new class of galactic X-ray sources with a luminosity of 10 to the 31st to 10 to the 34th ergs per sec. Emission from this class of objects is variable, predominantly below 2 keV, and originates from nearby stellar objects.

Catura, R. C.; Acton, L. W.; Johnson, H. M.

1975-01-01

68

X-ray emission mechanism in magnetars  

NASA Astrophysics Data System (ADS)

In the magnetar model, the observed persistent luminosity and outbursts are both powered by dissipation of magnetic energy. The emission mechanisms of persistent and burst emission will be discussed and compared. Observations suggest the presence of hot spots on magnetars. They may result from internal (subsurface) or external (magnetospheric) heating. Both mechanisms appear to be needed to explain the data.

Hascoet, Romain; Beloborodov, Andrei M

2014-08-01

69

The X-Ray Emission of the Centaurus A Jet.  

PubMed

The extended nonthermal X-ray emission of extragalactic jets like Centaurus A can only be explained by in situ particle acceleration. The only energy source in the entire jet region is the magnetic field. Magnetic reconnection can convert the free energy stored in the helical configuration to particle kinetic energy. In the collisionless magnetized jet plasma, the inertia-driven reconnection is operating in a highly filamentary magnetic flux rope, and this results in a continuously charged particle acceleration. The synchrotron radiation of these particles can cause the observed X-ray emission in Centaurus A. PMID:10655169

Birk; Lesch

2000-02-20

70

Modeling X-ray Emission due to Charge Exchange  

NASA Astrophysics Data System (ADS)

Since the advent of Cravens' [1] proposal that the observed X-ray emission from comet Hyakutake was due to charge exchange (CX) of highly-charged solar wind ions with cometary neutrals, the CX-mechanism has been identified as a possible dominant contributor to the X-ray emission observed in the heliosphere, planetary exospheres, the geocorona, supernova remnants, starburst galaxies, and molecular cooling flows in galaxy clusters. To provide reliable CX-induced X-ray spectra models to simulate these and other astrophysical environments, we have undertaken a project to compute quantum-state-resolved CX cross sections of highly-charged ions colliding with H and He. Here we summarize current results for C^(5-6)+, N^6+, and O^(6-8)+ obtained with the molecular-orbital close-coupling (CC), atomic-orbital CC, and classical trajectory Monte Carlo methods. Utilizing the theoretical CX cross sections, cascade models are computed to generate X-ray spectra and compared to available measurements and observations. Comparison is also made to models assuming excitation by thermal electrons to identify diagnostics to distinguish CX-induced and electron-impact-induced X-ray emission.[4pt] [1] T. E. Cravens, Geophys. Res. Lett. 25, 105 (1997).

Stancil, P. C.; Nolte, J. L.; Porter, R. L.; Shelton, R. L.; Wu, Y.; Schultz, D. R.; Hui, Y.; Rakovic, M. J.; Ferland, G. J.; Liebermann, H. P.; Buenker, R. J.

2012-06-01

71

A CHANGE IN THE QUIESCENT X-RAY SPECTRUM OF THE NEUTRON STAR LOW-MASS X-RAY BINARY MXB 1659-29  

SciTech Connect

The quasi-persistent neutron star low-mass X-ray binary MXB 1659-29 went into quiescence in 2001, and we have followed its quiescent X-ray evolution since. Observations over the first 4 yr showed a rapid drop in flux and temperature of the neutron star atmosphere, interpreted as cooling of the neutron star crust which had been heated during the 2.5 yr outburst. However, observations taken approximately 1400 and 2400 days into quiescence were consistent with each other, suggesting the crust had reached thermal equilibrium with the core. Here we present a new Chandra observation of MXB 1659-29 taken 11 yr into quiescence and 4 yr since the last Chandra observation. This new observation shows an unexpected factor of {approx}3 drop in count rate and change in spectral shape since the last observation, which cannot be explained simply by continued cooling. Two possible scenarios are that either the neutron star temperature has remained unchanged and there has been an increase in the column density, or, alternatively the neutron star temperature has dropped precipitously and the spectrum is now dominated by a power-law component. The first scenario may be possible given that MXB 1659-29 is a near edge-on system, and an increase in column density could be due to build-up of material in, and a thickening of, a truncated accretion disk during quiescence. But, a large change in disk height may not be plausible if standard accretion disk theory holds during quiescence. Alternatively, the disk may be precessing, leading to a higher column density during this latest observation.

Cackett, E. M. [Department of Physics and Astronomy, Wayne State University, 666 W. Hancock Street, Detroit, MI 48201 (United States); Brown, E. F. [Department of Physics and Astronomy, National Superconducting Cyclotron Laboratory, and the Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Cumming, A. [Department of Physics, McGill University, 3600 rue University, Montreal, QC H3A 2T8 (Canada); Degenaar, N.; Miller, J. M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042 (United States); Fridriksson, J. K.; Wijnands, R. [Astronomical Institute ''Anton Pannekoek'', University of Amsterdam, Science Park 904, 1098-XH Amsterdam (Netherlands); Homan, J., E-mail: ecackett@wayne.edu [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139 (United States)

2013-09-10

72

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

73

Study of Diffuse X-ray Emission in Globular Clusters  

NASA Technical Reports Server (NTRS)

This grant supported our analysis of ROSAT x-ray data on globular clusters. Although the grant title referred to our original ROSAT proposal (cycle 1) to study diffuse soft x-ray emission in three globulars (for which time was only granted in that original observing cycle for one cluster, 47 Tuc), the grant has also been maintained through several renewals and funding supplements to support our later ROSAT observations of point sources in globulars. The primary emphasis has been on the study of the dim sources, or low liuminosity globular cluster x-ray sources, which we had originally discovered with the Einstein Observatory and for which ROSAT provided the logical followup. In this Final Report, we summarize the Scientific Objectives of this investigation of both diffuse emission and dim sources in globular clusters and the Results Achieved; and finally the Papers Published.

Grindlay, Jonathan E.

1997-01-01

74

Upper limit to x-ray emission from Saturn  

SciTech Connect

X-rays are produced in auroral discharges and their measurement can serve to characterize the interaction processes responsible for the aurora itself. The existence of auroral activity on Saturn was suggested by the observation of a magnetosphere by Pioneer 11 and confirmed by UV measurements during the Voyager encounters. The detection of x rays from Jupiter with the Einstein Observatory (HEAO 2) satellite provided the impetus for a subsequent observation of Saturn. No emission was detected. This article presents the upper limit established by the observation and derives an expected emission level assuming x ray production to be the result of bremsstrahlung from keV electrons precipitating into Saturn's atmosphere. The difference is a factor of 100. 20 references.

Gilman, D.A.; Hurley, K.C.; Seward, F.D.; Schnopper, H.W.; Sullivan, J.D.; Metzger, A.E.

1986-01-01

75

X-Ray, UV, and Optical Observations of Supernova 2006bp with Swift: Detection of Early X-Ray Emission  

Microsoft Academic Search

We present results on the X-ray and optical\\/UV emission from the Type II-P supernova (SN) 2006bp and the interaction of the SN shock with its environment, obtained with the X-Ray Telescope (XRT) and UV\\/Optical Telescope (UVOT) on board Swift. SN 2006bp is detected in X-rays at a 4.5 sigma level of significance in the merged XRT data from days 1

S. Immler; P. J. Brown; P. Milne; L. Dessart; P. A. Mazzali; W. Landsman; N. Gehrels; R. Petre; D. N. Burrows; J. A. Nousek; R. A. Chevalier; C. L. Williams; M. Koss; C. J. Stockdale; M. T. Kelley; K. W. Weiler; S. T. Holland; E. Pian; P. W. A. Roming; D. Pooley; K. Nomoto; J. Greiner; S. Campana; A. M. Soderberg

2007-01-01

76

Diffuse X-Ray Emission in the Milky Way  

NASA Technical Reports Server (NTRS)

Our understanding of the diffuse X-ray emission from the Milky Way has evolved. extensively with time from when it was first observed in the 1960's, and its origin is still the subject of debate as much now as ever. This presentation will provide an overview of that evolution, the various emission components, emission mechanisms, an assessment of the current state of the field, and implications for eROSITA.

Snowden, Steve

2011-01-01

77

Large Scale Diffuse X-ray Emission from Abell 3571  

NASA Technical Reports Server (NTRS)

Observations of the Luman alpha forest suggest that there are many more baryons at high redshift than we can find in the Universe nearby. The largest known concentration of baryons in the nearby Universe is the Shapley supercluster. We scanned the Shapley supercluster to search for large scale diffuse emission with the Rossi X-ray Timing Explorer (RXTE), and found some evidence for such emission. Large scale diffuse emission may be associated to the supercluster, or the clusters of galaxies within the supercluster. In this paper we present results of scans near Abell 3571. We found that the sum of a cooling flow and an isothermal beta model adequately describes the X-ray emission from the cluster. Our results suggest that diffuse emission from A3571 extends out to about two virial radii. We briefly discuss the importance of the determination of the cut off radius of the beta model.

Molnar, Sandor M.; White, Nicholas E. (Technical Monitor)

2001-01-01

78

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

79

New field-emission x-ray radiography system  

NASA Astrophysics Data System (ADS)

A new field-emission x-ray radiography system based on our design is described. The key component of the system is a triode-type x-ray source with a built-in nanostructured electron source. The electron source is comprised of palladium-induced carbon nanofibers, which continue to field-emit electrons for more than 10 h at 2×10-7 Torr with a fluctuation of +/-8%. Feedback control of the potential of the electron-extracting electrode, or the gate, reduces the current fluctuation to +/-0.5%, but this current regulation does little to improve the image resolution. Our system provides sharp x-ray images of both biological and nonbiological samples.

Senda, S.; Tanemura, M.; Sakai, Y.; Ichikawa, Y.; Kita, S.; Otsuka, T.; Haga, A.; Okuyama, F.

2004-05-01

80

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

81

X-ray emission from hybrid-chromosphere stars  

NASA Technical Reports Server (NTRS)

The observations of hybrid stars made by the Exosat X-ray satellite are considered, and emphasis is placed on the hybrid star alpha TrA. Attention is focused on the determination of the column density of IS hydrogen toward the stars in order to interpret X-ray observations of stellar coronal emission. The coronal properties of alpha TrA are discussed as well as implications of the general coronal properties of hybrid stars. An analysis of the X-ray data, in conjunction with transition region properties of the star, shows that the X-ray emitting plasma is likely to have a temperature of at least 10 to the 6th K. The X-ray luminosity of the star is calculated to be about 5 x 10 to the 29th ergs/s over the 1-300 A spectral region and 7 x 10 to the 28th ergs/s in the 0.2-4 keV energy range for N(H) = 5 x 10 to the 19th /sq cm and a temperature of 10 to the 6th K.

Brown, Alexander; Linsky, Jeffrey L.; Drake, Stephen A.; Van Steenberg, Michael E.

1991-01-01

82

X-ray emission from the Pleiades cluster  

NASA Technical Reports Server (NTRS)

The detection and identification of H0344+24, a new X-ray source located in the Pleiades cluster, is reported, based on observations made with HEAO A-2 low-energy detector 1 in the 0.15-3.0-keV energy band in August, 1977. The 90-percent-confidence error box for the new source is centered at 03 h 44.1 min right ascension (1950), near the center star of the 500-star Pleiades cluster, 25-eta-Tau. Since no likely galactic or extragalactic source of X-rays was found in a catalog search of the error-box region, identification of the source with the Pleiades cluster is considered secure. X-ray luminosity of the source is calculated to be about 10 to the 32nd ergs/sec, based on a distance of 125 pc. The X-ray characteristics of the Pleiades stars are discussed, and it is concluded that H0344+24 can best be explained as the integrated X-ray emission of all the B and F stars in the cluster.

Agrawal, P. C.; Singh, K. P.; Riegler, G. R.

1983-01-01

83

X-ray Emission from Thunderstorms and Lightning  

SciTech Connect

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.

Dwyer, Joseph (Florida Institute of Technology) [Florida Institute of Technology

2009-08-08

84

X-ray Emission from Thunderstorms and Lightning  

SciTech Connect

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. 

Joseph Dwyer

2009-07-08

85

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. 

Joseph Dwyer

2010-01-08

86

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.

87

Hard X-ray emission from imploding wire arrays  

SciTech Connect

Results are presented from experimental studies of the generation of hard X-ray (HXR) emission with photon energies above 20 keV during the implosion of wire arrays in the Angara-5-1 facility. An analysis of X-ray images of the Z-pinch shows that the dimensions and spatial structures of the emitting regions are different for hard and soft X rays. It is found that the HXR emission peak is delayed with respect to the soft X-ray (SXR) one. The dependence of the HXR power on the material, initial diameter, and mass (implosion time) of the wire array is determined. It is shown that the HXR intensity in the spectral range >50 keV is several orders higher than the emission intensity in the high-energy tail of the SXR spectrum (assuming that this spectrum is thermal). A comparison of the time evolution and spatial localization of the HXR and SXR sources during the implosion of wire arrays indicates the presence of a new superthermal phenomenon that differs qualitatively from the processes determining the peak power of the SXR pulse. Possible mechanisms that can be responsible for the generation of HXR pulses are considered.

Aleksandrov, V. V.; Grabovski, E. V.; Gribov, A. N.; Gritsuk, A. N.; Medovshchikov, S. F.; Oleinik, G. M. [Troitsk Institute for Innovation and Fusion Research (Russian Federation); Sasorov, P. V. [Institute of Theoretical and Experimental Physics (Russian Federation)

2008-04-15

88

Hard X-ray emission from imploding wire arrays  

NASA Astrophysics Data System (ADS)

Results are presented from experimental studies of the generation of hard X-ray (HXR) emission with photon energies above 20 keV during the implosion of wire arrays in the Angara-5-1 facility. An analysis of X-ray images of the Z-pinch shows that the dimensions and spatial structures of the emitting regions are different for hard and soft X rays. It is found that the HXR emission peak is delayed with respect to the soft X-ray (SXR) one. The dependence of the HXR power on the material, initial diameter, and mass (implosion time) of the wire array is determined. It is shown that the HXR intensity in the spectral range >50 keV is several orders higher than the emission intensity in the high-energy tail of the SXR spectrum (assuming that this spectrum is thermal). A comparison of the time evolution and spatial localization of the HXR and SXR sources during the implosion of wire arrays indicates the presence of a new superthermal phenomenon that differs qualitatively from the processes determining the peak power of the SXR pulse. Possible mechanisms that can be responsible for the generation of HXR pulses are considered.

Aleksandrov, V. V.; Grabovski, E. V.; Gribov, A. N.; Gritsuk, A. N.; Medovshchikov, S. F.; Oleinik, G. M.; Sasorov, P. V.

2008-04-01

89

Field emission x-ray tube for mammography  

NASA Astrophysics Data System (ADS)

We propose to develop a time-gated x-ray imaging technique for screening mamography. If successful, it will greatly improve the accuracy of current mammography with about 50% reduction of current patient radiation. The technique can be applied to other x-ray imaging procedures also. We are now working to determine the feasibility of the key technologies- an x-ray source that can be pulsed on and off at a subnanosecond rate and a detector that can be gated at the same rate- that represent potential roadblocks to achieving this goal. A field emission x-ray tube will be used as the source. The field emission cathode consists of a substrate with sharp points and a metallic grid. A voltage on the grid creates an electric field that produces tunnel emission from the array of tips. The geometry of such a tube make electron optics easier, high currents are possible and the tube can be turned on and off rapidly. It also appears that synchronous electronic gating of the detector is possible.

Knight, Larry V.; Pew, Hans K.; Reyes, Arturo; Liu, Hong

2000-10-01

90

On the Bolometric Quiescent Luminosity and Luminosity Swing of Black Hole Candidate and Neutron Star Low-Mass X-Ray Transients  

Microsoft Academic Search

Low-mass X-ray transients hosting black hole candidates display on average a factor of ~100 larger swing in the minimum (quiescent) to maximum (outburst) X-ray luminosity than neutron star systems do, despite the fact that the swing in the mass inflow rate is likely in the same range. Advection-dominated accretion flows, ADAFs, were proposed to interpret such a difference, because the

Sergio Campana; Luigi Stella

2000-01-01

91

On the characteristics of line emissions from binary X-ray sources and supernova remnants  

Microsoft Academic Search

The paper considers the characteristics of line emissions from binary X-ray sources and supernova remnants. X-ray spectroscopy of celestial X-ray sources can yield useful data on physical conditions and processes responsible for emission from binary X-ray sources; iron line emission at about 6.8 keV from many supernova remnants and X-ray binaries has been observed and the available data on iron

T. M. K. Marar; V. S. Iyengar; K. Kasturirangan; U. R. Rao

1979-01-01

92

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

NASA Technical Reports Server (NTRS)

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

1999-01-01

93

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

Microsoft Academic Search

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

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

1989-01-01

94

High resolution spectroscopy of X-ray emission from high mass X-ray binaries  

NASA Astrophysics Data System (ADS)

This article briefly reviews first the progress of spectroscopy in X-ray astronomy from proportional counters, a major instrument in early phase of X-ray astronomy, to gas scintillation proportional counters, X-ray CCD cameras, transmission and reflection gratings, and finally to X-ray micro-calorimeters. As a typical example of spectral features observed from high mass X-ray binaries (HMXBs), the spectra observed from Vela X-1 with Chandra grating spectrometers are then presented and compared with computer simulations for high mass binary systems.

Nagase, F.; Watanabe, S.

2006-01-01

95

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

96

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; A. N. Maurellis; G. R. Gladstone; G. Branduardi-Raymont

2006-01-01

97

Photoionized X-Ray Emission in CYG X-2  

NASA Astrophysics Data System (ADS)

This highly luminous X-ray binary was observed with the Chandra HETGS during the verification and checkout. The source showed an X-ray flux of nearly 0.5 Crab causing severe depletion of photons in the MEG and HEG 1st order spectra due to pile up effects. Nevertheless the spectrum showed various remarkable features at high energies and in the higher orders, which can be identified as photoionized emission from Mg-, Si-, S-, Ca-, and Fe. However the detections remained spurious and at higher wavelengths very much affected by pile up. We want to re-observe Cyg X-2 for 15 ks, in order to obtain pile up free 1st order spectra, enhance and confirm the findings in the higher order spectra as well as study variability in the line emission.

Canizares, Claude

2000-09-01

98

Quantifying the Exospheric Component of Soft X-ray Emission  

NASA Technical Reports Server (NTRS)

High charge state heavy ions in the solar wind exchange charge with ambient neutral gas. This process creates a product ion in an excited state. During the radiative cascade process, EUV and X-ray photons are emitted with energies in the range of about 100 eV to 1 keV. Because the terrestrial exospheric density at the nominal magnetopause location is relatively high, approx. 10 cu cm, solar wind charge exchange, or SWCX, can be observed by Earth-orbiting soft X-ray instruments such as the ROSAT Position Sensitive Proportional Counters (PSPC). In this presentation, we will compare simulated and observed soft Xray emission during an event on August 18-19, 1991 and discuss the role of exospheric SWCX emission for this and other events.

Kuntz, Kip; Collier, Michael R.; Snowden, Steven L.; Robertson, Ina; Hansen, Kenneth; Cravens, Thomas

2007-01-01

99

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

100

Implications of x-ray emission from lightning  

NASA Astrophysics Data System (ADS)

Dwyer et al. [2003, 2004a] recently reported measurements of bursts of x-rays, with energies up to ~250 keV, originating from dart leaders and possibly the return strokes of rocket-triggered lightning. In this paper, these x-ray observations are compared with the relativistic runaway electron avalanche (RREA) model. It is found that for dart leaders the standard RREA model is inconsistent with the observed spectrum and flux of the x-ray emission. This result implies that the cold runaway electron model may be applicable to dart leaders. In this model, runaway electrons are directly accelerated out of the bulk electron population, produced by the ionization of the neutral atoms. However, this mechanism requires an electric field an order-of-magnitude larger than the conventional breakdown field. Because the flux of runaway electrons is very sensitive to the electric field strength, x-ray observations of lightning provide a novel tool for determining the fields associated with the leaders.

Dwyer, J. R.

2004-06-01

101

X-ray emission from clusters of galaxies  

NASA Technical Reports Server (NTRS)

Some X-ray spectral observations of approximately 30 clusters of galaxies from HEAO-1 are summarized. There exists strong correlation betwen X-ray luminosity, L(x), and temperature kT in the form L(x)alphaT to the 2.3 power. This result combined with the L(x) central galaxy density relation and the virial theorem indicates that the core dadius of the gas should be roughly independent of L(x) or Kt and that more luminous clusters have a greater fraction of their virial mass in gas. The poor correlation of KT and optical velocity dispersion seems to indicate that clusters have a variety of equations of state. There is poor agreement between X-ray imaging observations and optical and X-ray spectral measures of the polytropic index. Most clusters show Fe emission lines with a strong indication that they all have roughly 1/2 solar abundance. The evidence for cooling in the cores several clusters is discussed based on spectral observations with the Einstein solid state spectrometer.

Mushotzky, R. F.

1984-01-01

102

X-ray emission from clusters of galaxies  

NASA Technical Reports Server (NTRS)

Some X-ray spectral observations of approximately 30 clusters of galaxies from HEAO-1 are summarized. There exists strong correlations between X-ray luminosity, L(x), and temperature kT in the form L(x)alphaT to the 2.3 power. This result combined with the L(x) central galaxy density relation and the virial theorem indicates that the core dadius of the gas should be roughly independent of L(x) or KT and that more luminous clusters have a greater fraction of their virial mass in gas. The poor correlation of KT and optical velocity dispersion seems to indicate that clusters have a variety of equations of state. There is poor agreement between X-ray imaging observations and optical and X-ray spectral measures of the polytropic index. Most clusters show Fe emission lines with a strong indication that they all have roughly 1/2 solar abundance. The evidence for cooling in the cores of several clusters is discussed based on spectral observations with the Einstein solid state spectrometer.

Mushotzky, R. F.

1983-01-01

103

X-ray induced electron emission. Final report  

SciTech Connect

The development and use of a magnetic spectrograph for the measurement of X-ray induced electron emission is described. Results are presented for metal and dielectric targets ranging in atomic number from Z=6 to Z-82. Materials studied were lead, tantalum, copper, aluminum, magnesium, solar cell cover glass, silica cloth, thermal control paint, Kevlar, Mylar, and conducting/nonconducting epoxy. Direct measurement was made of the quantum yield and energy distribution of electrons emitted at angles of 0 deg, 30 deg, 45 deg and 60 deg with respect to the surface normal of targets exposed to normal incidence filtered and unfiltered 50kV bremsstrah lung X-rays. Experimental results are compared with previous measurements where possible, and with computer code predictions where predictive capability matches the measurement range. The experimental results corroborates the cos theta angular dependence predicted by simple theoretical models, particularly for medium and high Z materials. A trend toward isotropic emission distribution is noted for the lower Z materials. Compared to the measured results, the emission yields predicted by a commonly used analytical model are low by approximately a factor of 2 for the unfiltered X-ray spectrum.

Aeby, C.A.

1982-04-01

104

Einstein Observations of X-ray emission from A stars  

NASA Technical Reports Server (NTRS)

Results are reported from the combined CfA Stellar Survey of selected bright A stars and an Einstein Guest Observer program for Ap and Am stars. In an initial report of results from the CfA Stellar Surveys by Vaiana et al. (1981) it was noted that the spread in observed X-ray luminosities among the few A stars observed was quite large. The reasons for this large spread was studied by Pallavicini et al. (1981). It was found that the X-ray emission from normal stars is related very strongly to bolometric luminosity for early-type stars and to rotation rate for late-type stars. However, an exception to this rule has been the apparently anomalous behavior of A star X-ray emission, for which the large spread in luminosity showed no apparent correlation with either bolometric luminosity or stellar rotation rate. In the present study, it is shown that the level of emission from normal A stars agrees with the correlation observed for O and B stars.

Golub, L.; Harnden, F. R., Jr.; Maxson, C. W.; Vaiana, G. S.; Snow, T. P., Jr.; Rosner, R.; Cash, W. C., Jr.

1983-01-01

105

Gamma-ray Emission from X-ray Binaries  

NASA Astrophysics Data System (ADS)

The detection of PSR B1259-63, HESS J0632+057, LS 5039, LS I +61 303 at the TeV energies has established X-ray binaries (XRBs) as a new class of very-high-energy (VHE, >100 GeV) gamma-ray emitters. Among them, PSR B1259-63 is a Be/pulsar system, detected at TeV energies by HESS and Fermi LAT, while HESS J0632+057 is a recently discovered VHE emitter composed of a Be star and a compact object of unknown nature. LS 5039 and LS I +61 303 are possibly microquasars, a sub-class of XRBs that contain a black hole with collimated, relativistic jets. Powered by accretion from the companion stars, microquasars radiate strongly at X-ray and soft gamma-ray energies. Cygnus X-1 and Cygnus X-3 are two famous microquasars as well. Cygnus X-1 has been observed once at TeV energies while Cygnus X-3 is a known GeV emitter. Many theoretical models envision VHE emission when these sources manifest relativistic persistent jets or transient ejections. In light of these considerations, VERITAS has been employed to study two XRBs for possible TeV emission. The first Be/XRB is 1A 0535+262. No GeV or TeV emission was detected over the outburst and orbital period. The gamma-ray and X-ray observations suggest the absence of a significant population of non-thermal particles in the system, which distinguishes 1A 0535+262 from other Be/XRBs such as PSR B1259-63 and LS I +61 303. VERITAS has also been involved in the study of Cygnus X-3 as part of the multi-wavelength study effort in the radio, infra-red, soft x-ray, hard x-ray and gamma-ray (<100 GeV) bands, which has proven very useful in the understanding of the physics of the system, even in the lack of TeV emission. With the aid of VERITAS, it can be possible to cast light on the particular conditions which could trigger VHE emission. This can help us understand the mechanisms that may trigger VHE gamma-ray emission, thus improving our knowledge of particle acceleration and radiative processes in the jets. The implications have far reaching consequences on the understanding of other XRBs and microquasars and also of active galactic nuclei, which are in many ways similar to microquasars and are prominent VHE gamma-ray sources themselves.

Varlotta, Angelo; VERITAS; AGILE

2013-01-01

106

THE CHANDRA CARINA COMPLEX PROJECT: DECIPHERING THE ENIGMA OF CARINA'S DIFFUSE X-RAY EMISSION  

SciTech Connect

We present a 1.42 deg{sup 2} mosaic of diffuse X-ray emission in the Great Nebula in Carina from the Chandra X-ray Observatory Advanced CCD Imaging Spectrometer camera. After removing >14,000 X-ray point sources from the field, we smooth the remaining unresolved emission, tessellate it into segments of similar apparent surface brightness, and perform X-ray spectral fitting on those tessellates to infer the intrinsic properties of the X-ray-emitting plasma. By modeling faint resolved point sources, we estimate the contribution to the extended X-ray emission from unresolved point sources and show that the vast majority of Carina's unresolved X-ray emission is truly diffuse. Line-like correlated residuals in the X-ray spectral fits suggest that substantial X-ray emission is generated by charge exchange at the interfaces between Carina's hot, rarefied plasma and its many cold neutral pillars, ridges, and clumps.

Townsley, Leisa K.; Broos, Patrick S.; Garmire, Gordon P. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Chu, You-Hua; Gruendl, Robert A. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801 (United States); Gagne, Marc [Department of Geology and Astronomy, West Chester University, West Chester, PA 19383 (United States); Hamaguchi, Kenji [CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771 (United States); Mac Low, Mordecai-Mark [Department of Astrophysics, American Museum of Natural History, New York, NY 10024-5192 (United States); Montmerle, Thierry [Institut d'Astrophysique de Paris, 98bis, Bd Arago, 75014 Paris (France); Naze, Yael [GAPHE, Departement AGO, Universite de Liege, Allee du 6 Aout 17, Bat. B5C, B4000-Liege (Belgium); Oey, M. S. [Department of Astronomy, University of Michigan, 830 Dennison Building, Ann Arbor, MI 48109-1042 (United States); Park, Sangwook [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Petre, Robert [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Pittard, Julian M., E-mail: townsley@astro.psu.edu [School of Physics and Astronomy, University of Leeds, Leeds (United Kingdom)

2011-05-01

107

Diffuse X-ray Emission from M101  

NASA Technical Reports Server (NTRS)

The total 0.45-2.0 keV luminosity of M101 is 3.1 x 10(exp 39) ergs/s, of which 2.2 x 10(exp 39) ergs/s is due to diffuse emission. Of the diffuse emission, no more than 6% can be due to unresolved point sources such as X-ray binaries, and approx. 11% is due to dwarf stars. The diffuse emission traces the spiral arms and is roughly correlated with the H alpha and FUV (far ultraviolet) 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 = 0.20,0.75 keV, and the ratios 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 extra-planar. 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.; White, Nicholas E. (Technical Monitor)

2002-01-01

108

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

109

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

110

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

111

Backscatter of hard X-rays in the solar atmosphere. [Calculating the reflectance of solar x ray emission  

NASA Technical Reports Server (NTRS)

The solar photosphere backscatters a substantial fraction of the hard X rays from solar flares incident upon it. This reflection was studied using a Monte Carlo simulation which takes into account Compton scattering and photo-electric absorption. Both isotropic and anisotropic X ray sources are considered. The bremsstrahlung from an anisotropic distribution of electrons are evaluated. By taking the reflection into account, the inconsistency is removed between recent observational data regarding the center-to-limb variation of solar X ray emission and the predictions of models in which accelerated electrons are moving down toward the photosphere.

Bai, T.; Ramaty, R.

1977-01-01

112

The Soft X-Ray Emission Component of Spiral Galaxies  

NASA Technical Reports Server (NTRS)

Work included the analysis of the HRJ observations of the Sombrero galaxy (Fabbiano and Juda) published in Ap.J. This paper discussed the discovery of a point-like x-ray source at the nucleus of the galaxy, which is suspected to host a massive black hole. More work was done on the analysis of the Observation of M94 in support of an AXAF proposal. We have also analyzed the M81 data by adding to our observation the entire set of the archival ROSAT data. We plan to write up the results for publication. Both galaxies have nuclei optically similar to that of the Sombrero galaxy. The nucleus of M81 is a known x-ray source. The M94 data has revealed a point-like nuclear source superposed on more diffuse emission.

Fabbiano, Giuseppina

1998-01-01

113

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

114

Measurement of coronal X-ray emission lines from Capella  

NASA Technical Reports Server (NTRS)

The Einstein Observatory's Focal Plane Crystal Spectrometer has detected X-ray emission lines due to O VIII, Fe XVII, and Fe XX, from the binary star system Capella. Line luminosities are well fitted by an emitting plasma at a single temperature of 6.29 + or - 0.01 - 0.03 million K, and a volume emission measure of about 8.6 x 10 to the 52nd/cu cm, corresponding to the low temperature component previously observed. A high temperature component is undetectable, since the observed lines are not produced in plasma at temperatures above about 20 million K. Nearly isothermal plasma would be expected if many of the magnetically confined coronal loops have similar sizes and pressures, and a second population of longer loops would be required to account for the hotter component. An alternative interpretation of the observed X-ray line emission and upper limit is that the plasma contains a continuous distribution of emission measure versus temperature that rises sharply to 3 million K and then falls by nearly a decade to 16 million. An extrapolation of the loop sizes suggested by this alternative to hotter, longer loops may also account for the higher temperature emission.

Vedder, P. W.; Canizares, C. R.

1983-01-01

115

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

116

Proton-Induced X-Ray Emission Analysis.  

NASA Astrophysics Data System (ADS)

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. It was shown that it is possible to use these X-rays to measure very low concentrations of trace elements in samples. Early work concentrated on the development of the method as a means of analysing thin films such as are encountered in monitoring air pollution. Work at Lucas Heights had concentrated on the use of ion beams for the analysis of archaeological artefacts using the technique of Particle induced Gamma ray emission (PIGME). Because of the necessity to use analysis methods that did not require destruction of the sample, our work had involved the use of targets that were thick (in terms of the incident particle). When it was decided to introduce PIXE at our laboratory, the filed of thick target PIXE analysis was little explored. In comparison with thin samples, as had normally been studied, the mathematical foundation for analysis had not been well established. My thesis is concerned with the study of that foundation. After a PIXE spectrum has been measured, there are essentially three steps in its interpretation. The first is to analyse the spectrum to extract the areas of the peaks which constitute that spectrum. For thick samples that analysis is complicated further by the effect of self absorption within the sample. This changes the ratios of the characteristic peak areas and must be modelled in the analysis program. After peak areas have been estimated, they are utilised to determine the concentration of the element emitting those X-rays. This involves modelling the processes that result in the emission of X-rays and their attenuation in the sample and detector system. Finally, as PIXE is a multielemental technique, producing information on possibly 15 to 20 elements in a single measurement, multivariate statistical methods may be necessary for the interpretation of the database produced by a series of PIXE measurements.

Clayton, Eric John

117

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

118

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

Microsoft Academic Search

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

S. Hussain; M. Shafiq; M. A. Badar; M. Zakaullah

2010-01-01

119

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

120

X-ray emission from National Ignition Facility indirect drive targets.  

National Technical Information Service (NTIS)

We have performed a series of 1-D numerical simulations of the x-ray emission from National Ignition Facility (NIF) targets. Results are presented in terms of total x-ray energy, pulse length, and spectrum. Scaling of x-ray emissions is presented for vari...

A. T. Anderson R. A. Managan M. T. Tobin P. F. Peterson

1996-01-01

121

Nonthermal X-ray emission in clusters of galaxies  

NASA Astrophysics Data System (ADS)

Significant new insight on physical conditions in clusters of galaxies will be gained from observations of high energy (>20 keV) X-ray emission. In clusters, this emission is likely to be largely nonthermal radiation, probably resulting from Compton scattering of relativistic electrons by the cosmic microwave background radiation. The presence of relativistic electrons in some ~30 clusters is directly deduced from measurements of extended radio emission. I review previous results from RXTE and BeppoSAX measurements of a small sample of clusters, and report the results of our recent analysis of RXTE measurements of A2319. These measurements directly yield the mean strength of the intracluster magnetic fields and energy density of relativistic electrons. Implications of these results on the origin of the fields and electrons are briefly considered. Observations with the INTEGRAL satellite may prove pivotal in clearly establishing the significance of nonthermal phenomena in clusters.

Rephaeli, Y.

2001-09-01

122

X-ray Emission from Eta Carinae near Periastron in 2009: Origin of the X-ray Minimum  

NASA Astrophysics Data System (ADS)

X-ray emission from the supermassive binary system, Eta Carinae, declines sharply around periastron. This X-ray minimum has two distinct phases --- the lowest flux phase in the first ~3 weeks and a slightly brighter phase thereafter. In 2009, the Chandra X-ray Observatory monitored the first phase five times and found the lowest observed flux at ~1.9e-12 ergs cm-2 s-1 (3-8 keV). The spectral shape changed such that the hard band above ~4 keV dropped quickly at the beginning and the soft band flux gradually decreased to its lowest observed value in ~2 weeks. The hard band spectrum had begun to recover by that time. This spectral variation suggests that the shocked gas producing the hottest X-ray gas near the apex of the wind-wind collision (WWC) is blocked behind the dense inner wind of the primary star, which later occults slightly cooler gas downstream. Shocked gas previously produced by the system at earlier orbital phases is suggested to produce the faint residual X-ray emission seen when the emission near the apex is completely blocked by the primary wind. The brighter phase is probably caused by the re-appearance of the WWC plasma, whose emissivity significantly declined during the occultation. We interpret this to mean that the X-ray minimum is produced by a hybrid mechanism of an occultation and a decline in emissivity of the WWC shock. We constrain timings of superior conjunction and periastron based on these results.

Hamaguchi, Kenji; Corcoran, M. F.; Russell, C. M.; Pollock, A. M.; Gull, T. R.; Teodoro, M.; Madura, T.; Damineli, A.; Pittard, J. M.

2014-01-01

123

X-ray emission on hybird stars: ROSAT observations of alpha Trianguli Australis and iota Aurigae  

NASA Technical Reports Server (NTRS)

We report on deep ROSAT observations of two Hybrid atmosphere stars, alpha TrA and iota Aur, and our analysis of these observations. We detect high-energy transient phenomena on alpha TrA and consider the implications of this discovery to the atmospheres of Hybrid stars. We detect iota Aur in the high-energy passband of ROSAT, implying the existence of multimillion degree plasma on the star. Our major results include the following: discovery of two large flare events, detected during pointed observations of alpha TrA; the demonstration that the flare emission most likely comes from the giant itself, rather than from a previously unseen low-mass companion star; the demonstration that the plasma characteristics associated with the flares and with the 'quiescent' component are essentially indistinguishable; and that the geometric dimensions of the emitting plasma are considerably smaller than the critical dimension characterizing stable 'hot' coronal loop structures. Our results suggest that alpha TrA does not have any steady X-ray emission consistent with theoretical expectations, and support the argument that Hybrid stars constitute a transitional type of object in which large-scale magnetic dynamo activity ceases, and the dominant spatial scales characterizing coronal structure rapidly decline as such stars evolve across the X-ray 'Dividing Line' in the H-R diagram.

Kashyap, V.; Rosner, R.; Harnden, F. R., Jr.; Maggio, A.; Micela, G.; Sciortino, S.

1994-01-01

124

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

125

X-ray emission from the galactic disk.  

NASA Technical Reports Server (NTRS)

A search was made for a diffuse component of greater than 1.5 keV X rays associated with an interarm region of the Galaxy at galactic longitudes in the vicinity of 60 degrees. A statistically significant excess associated with a narrow disk component was detected. The angular extent of this component has a most probable value of 2 degrees. The best-fit spectrum yields an intensity of 2.9 photons/sq cm per sec per sterad over the 2-10 keV range. The 3-sigma upper limit to any emission in a 1.5 keV band centered at 7 keV from galactic latitudes not greater than 3.5 deg is 0.3 photons/sq cm per sec per sterad. Several possible emission models are evaluated, with the most likely choice being a population of unresolvable low-luminosity sources.

Bleach, R. D.; Boldt, E. A.; Holt, S. S.; Schwartz, D. A.; Serlemitsos, P. J.

1972-01-01

126

An X-Ray and Near-Infrared Study of the Galactic Ridge X-Ray Emission  

NASA Astrophysics Data System (ADS)

Abstract:The Galactic Ridge X-ray Emission (GRXE) is an extended X-ray emission along the Galactic Plane, which has a thermal spectrum with Fe K line. The origin had been a mystery for a long time. Recently, it is elucidated that the GRXE is a sum of dim point sources by the deepest observation of Chandra. There are some candidates of the sources, but it is difficult to know the nature from X-rays alone due to a limited number of X-ray photons. Thus, we combined near-infrared with X-ray. As a result, the point sources are background AGNs, white dwarf binaries (WD), and late-type stars (flare/quiescence). We obtained fraction to the Fe K line as follows: AGNs (˜ 33%), WD (˜ 38%), and late-type stars on flare (˜ 29%). Moreover, NIR observation indicates that WD are Cataclysmic Variables and Pre-Cataclysmic Variables. The latter has not been considered as the origin of the GRXE, but it is considered to contribute to the Fe K line of the GRXE.

Morihana, Kumiko

2012-07-01

127

X-Ray, UV, and Optical Observations of Supernova 2006bp with Swift: Detection of Early X-Ray Emission  

NASA Technical Reports Server (NTRS)

We present results on the X-ray and optical/UV emission from the Type IIP supernova (SN) 2006bp and the interaction of the SW shock with its environment, obtained with the X-Ray Telescope (XRT) and UV/Optical Telescope (UVOT) on-board the Swift observatory. SN 2006bp is detected in X-rays at a 4.5 sigmalevel of significance in the merged XRT data from days 1 to 12 after the explosion. If the (0.2-10 keV band) X-ray luminosity of L(sub 0.2-10) = (1.8 plus or minus 0.4) x l0(exp 39 ergs s(exp -1) is caused by interaction of the SN shock with circumstellar material (CSM), deposited by a stellar wind from the progenitor's companion star, a mass-loss rate of M is approximately 2x10(exp -6) solar mass yr(exp -1) (v(sub w)/10 km s(exp -l) is inferred. The mass-loss rate is one of the lowest ever recorded for a core-collapse SN and consistent with the non-detection in the radio with the VLA on days 2, 9, and 11 after the explosion. The Swift data further show a fading of the X-ray emission starting around day 12 after the explosion. In combination with a follow-up XMM-Newton observation obtained on day 21 after the explosion, an X-ray rate of decline Lx, varies as t(exp -n) with index n = 1.2 plus or minus 0.6 is inferred. Since no other SN has been detected in X-rays prior to the optical peak and since Type IIP SNe have an extended 'plateau' phase in the optical, we discuss the scenario that the X-rays might be due to inverse Compton scattering of photospheric optical photons off relativistic electrons produced in circumstellar shocks. However, due to the high required value of the Lorentz factor (approximately 10-100), inconsistent with the ejecta velocity inferred from optical line widths, we conclude that Inverse Compton scattering is an unlikely explanation for the observed X-ray emission. The fast evolution of the optical/ultraviolet (1900-5500A) spectral energy distribution and the spectral changes observed with Swift reveal the onset of metal line-blanketing and cooling of the expanding photosphere during the first few weeks after the outburst.

Immler, S.; Brown, P. J.; Milne, P.; Dessart, L.; Mazzali, P. A.; Landsman, W.; Gehrels, N.; Petre, R.; Burrows, D. N.; Nousek, J. A.; Chevalier, R. A.; Williams, C. L.; Koss, M.; Stockdale, C. J.; Kelley, M. T.; Weiler, K. W.; Holland, S. T.; Pian, E.; Roming, P. W. A.; Pooley, D.; Nomoto, K.; Greiner, J.; Campana, S.; Soderberg, A. M.

2007-01-01

128

Uhuru observations of short-time-scale variations of the Crab. [X ray emission from pulsar  

NASA Technical Reports Server (NTRS)

We have analyzed Uhuru X-ray observations of the Crab and found statistically significant variability in the intensity on time scales of several tenths of a second. Our results imply either that the X-ray emission from the pulsar NP 0532 is highly variable or that we have observed a previously undetected compact source of X-rays.

Forman, W.; Giacconi, R.; Jones, C.; Schreier, E.; Tananbaum, H.

1974-01-01

129

X-ray emission and X-ray photoelectron spectroscopic studies of fullerene fluoride C60F24  

NASA Astrophysics Data System (ADS)

The structure of the fullerence fluoride C60F24 of the T h symmetry contains two types of chemically different carbon atoms, namely, atoms of isolated double bonds and atoms of CF groups. X-ray photoelectron and x-ray emission spectroscopic studies of C60F24 revealed a difference in the widths of the x-ray bands corresponding to these types of atoms. Nonempirical quantum-chemical calculations performed for C59NF 24 + ions with a hole in the C 1s core level of the fullerence fluoride showed that the difference in the bandwidths may be due to the fact that the vibrational states of the system are different when 1s electrons are removed from chemically nonequivalent atoms.

Lavskaya, Yu. V.; Okotrub, A. V.; Bulusheva, L. G.; Pazhetnov, E. M.; Boronin, A. I.; Denisenko, N. I.; Boltalina, O. V.

2007-06-01

130

X-ray emission from young supernova remnants - Nonionization equilibrium abundances and emissivities  

NASA Technical Reports Server (NTRS)

X-ray line emission from hot, low-density plasma in young supernova remnants is strongly enhanced by departures from ionization equilibrium. The X-ray emission from a Sedov blast wave has been calculated using a nonequilibrium evolutionary treatment of the ionization structure, and the resulting spectrum has been fitted to HEAO 2 SSS data for Tycho's remnant. These models yield dramatically different elemental abundances for heavy elements (Ne, Mg, Si, S, Ar, Ca, and Fe), compared with two-temperature component equilibrium models of Becker et al. (1979, 1980). Nonequilibrium broad-band X-ray emissivities result in lower mass determinations for the supernova ejecta. Areas of further improvement of remnant X-ray modeling are suggested.

Shull, J. M.

1982-01-01

131

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

132

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

NASA Astrophysics Data System (ADS)

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% H2 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? 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.; Shafiq, M.; Badar, M. A.; Zakaullah, M.

2010-09-01

133

Nonquasineutral relativistic current filaments and their X-ray emission  

SciTech Connect

Nonquasineutral electron current filaments with the azimuthal magnetic field are considered that arise due to the generation of electron vorticity in the initial (dissipative) stage of evolution of a current-carrying plasma, when the Hall number is small ({sigma}B/en{sub e}c << 1) because of the low values of the plasma conductivity and magnetic field strength. Equilibrium filamentary structures with both zero and nonzero net currents are considered. Structures with a zero net current type form on time scales of t < t{sub sk} = (r{sub 0{omega}pe}/c){sup 2}t{sub st}, where t{sub sk} is the skin time, t{sub st} is the typical time of electron-ion collisions, and r{sub 0} is the radius of the filament. It is shown that, in nonquasineutral filaments in which the current is carried by electrons drifting in the crossed electric (E{sub r}) and magnetic (B{sub {theta}}) fields, ultrarelativistic electron beams on the typical charge-separation scale r{sub B} = B/(4{pi}en{sub e}) (the so-called magnetic Debye radius) can be generated. It is found that, for comparable electron currents, the characteristic electron energy in filaments with a nonzero net current is significantly lower than that in zero-net-current filaments that form on typical time scales of t < t{sub sk}. This is because, in the latter type of filaments, the oppositely directed electron currents repel one another; as a result, both the density and velocity of electrons increase near the filament axis, where the velocities of relativistic electrons are maximum. Filaments with a zero net current can emit X rays with photon energies h {omega} up to 10 MeV. The electron velocity distributions in filaments, the X-ray emission spectra, and the total X-ray yield per unit filament length are calculated as functions of the current and the electron number density in the filament. Analytical estimates of the characteristic lifetime of a radiating filament and the typical size of the radiating region as functions of the plasma density are obtained. The results of calculations are compared with the available experimental data.

Gordeev, A. V. [Russian Research Centre Kurchatov Institute (Russian Federation); Losseva, T. V. [Russian Academy of Sciences, Institute of Geosphere Dynamics (Russian Federation)

2009-02-15

134

Field emission x-ray tube for mammography  

Microsoft Academic Search

We propose to develop a time-gated x-ray imaging technique for screening mamography. If successful, it will greatly improve the accuracy of current mammography with about 50% reduction of current patient radiation. The technique can be applied to other x-ray imaging procedures also. We are now working to determine the feasibility of the key technologies- an x-ray source that can be

Larry V. Knight; Hans K. Pew; Arturo Reyes; Hong Liu

2000-01-01

135

X-ray emission from PSR 0355+54  

NASA Technical Reports Server (NTRS)

We have obtained a 20 ks observation of PSR 0355+54 using the ROSAT position sensitive proportional counter (PSPC). The pulsar is detected with a count rate of 4.2(+/- 1.3) x 10(exp -3)/s above the background. While the approximately 70 source counts are insufficient for spectral fitting, we have derived source parameters for specific cases of power law as well as blackbody spectra. For a Crab-like spectrum (photon index alpha = 2) we find L(sub x)(0.1-2.4 keV) = 1.0 x 10(exp 32) ergs/s, somewhat higher than upper limits reported from Einstein observations but consistent with typical L(sub x) versus E-dot values for other pulsars. For blackbody emission, we derive a temperature upper limit of approximately 9.5 x 10(exp 5) K for emission from the entire neutron star surface, which is consistent with standard models for cooling of the neutron star interior given a characteristic age 10(exp 5.75) yr. No evidence is present for modulation at the 156 ms pulsar period, setting a weak upper limit of approximately 75% for the pulsed fraction of the X-ray signal.

Slane, Patrick

1994-01-01

136

X-ray emission from the galactic disk  

NASA Technical Reports Server (NTRS)

A search was made of a diffuse component of X-rays 1.5 keV associated with an interarm region of the galaxy at galactic longitudes in the vicinity of 60 deg. A statistically significant excess associated with a narrow disk component was detected. The angular extent of this component has a most probable value of 2 deg and may be as large as 7 deg at 90% confidence. The best fit spectrum yields an intensity of 2.9 photons 1/(cm2-sec-ster) over the 2 to 10 keV range. The 3 sigma upper limit to any emission (e.g. iron line) in a 1.5 keV band centered at 7 keV from galactic latitudes h or = 3.5 deg is .3 photons 1/(cm2-sec-ster). Several possible emission models are discussed, with the most likely candidate being a population of unresolvable low luminosity discrete sources.

Bleach, R. D.; Boldt, E. A.; Holt, S. S.; Schwartz, D. A.; Serlemitsos, P. J.

1972-01-01

137

On the peak radio and X-ray emission from neutron star and black hole candidate X-ray transients  

NASA Astrophysics Data System (ADS)

We have compiled and analysed reports from the literature of (quasi-)simultaneous observations of X-ray transients at radio and X-ray wavelengths and compared them with each other and with more unusual radio-bright sources such as Cygnus X-3, GRS 1915+105 and Circinus X-1. There exists a significant (>97 per cent likelihood) positive (rank) correlation between the peak X-ray flux PX and radio flux density PR for the black hole candidate (BHC) systems, and a marginally significant positive (rank) correlation for the neutron star (NS) systems. This is further evidence for a coupling between accretion and outflows in X-ray binary systems, in this case implying a relation between peak disc-accretion rate and the number of synchrotron-emitting electrons ejected. However, we also show that the distribution of `radio loudness', PR/PX, is significantly different for the two samples, in the sense that the BHCs generally have a higher PR/PX ratio. The origin of this discrepancy is uncertain, but probably reflects differences in the energetics and/or radiative efficiency of flows around the neutron stars and black holes; we briefly discuss some of these possibilities. Furthermore, the data for the two recently discovered `fast transients' (FTs), XTE J0421+560/CI Cam and SAX J1819.3-2525/V4641 Sgr are entirely compatible with the distribution of BHCs. As at least three of the BHCs and both FTs have been directly resolved into mildly relativistic jets, it seems likely that such outflows are the origin of the radio emission in all BHC and FT transients, and probably also for the NS transients. We further note that the range of X-ray and radio fluxes observed from the unusual superluminal source GRS 1915+105 is also entirely compatible with the distribution for transients, implying that there is nothing special about the physics of jet formation in that system. We conclude that these data point to the formation of a mildly relativistic jet whose luminosity is a function of the accretion rate in the majority, if not all, X-ray transient outbursts, but whose relation to the observed X-ray emission is dependent on the nature of the accreting compact object.

Fender, R. P.; Kuulkers, E.

2001-07-01

138

Soft x-ray emission from millimeter-wave electron cyclotron resonance discharge.  

PubMed

This work is devoted to the experimental investigation of incoherent soft x-ray radiation from an electron cyclotron resonance discharge with pumping by a millimeter-wave beam from a gyrotron. The basic contribution to the x-ray spectrum was shown to be produced by a plasma emission in the wavelength region 4.5-12 nm. The power of the x-ray emission from the ECR discharge was about 35 kW, and the efficiency of conversion of the gyrotron radiation into an x-ray emission exceeded 25%. PMID:21307525

Golubev, S V; Platonov, Y Y; Razin, S V; Zorin, V G

1996-01-01

139

Analysis and interpretation of diffuse x-ray emission using data from the Einstein satellite  

NASA Technical Reports Server (NTRS)

An ambitious program to create a powerful and accessible archive of the HEAO-2 Imaging Proportional Counter (IPC) database was outlined. The scientific utility of that database for studies of diffuse x ray emissions was explored. Technical and scientific accomplishments are reviewed. Three papers were presented which have major new scientific findings relevant to the global structure of the interstellar medium and the origin of the cosmic x ray background. An all-sky map of diffuse x ray emission was constructed.

Helfand, David J.

1991-01-01

140

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

141

Hard X-ray emission from IC443: evidence for a shocked molecular clump?  

NASA Astrophysics Data System (ADS)

We report BeppoSAX observations of spatially resolved hard X-ray emission from IC 443, a supernova remnant interacting with a molecular cloud. The emission is shown to come from two localized features spatially correlated with bright molecular emission regions. Both hard X-ray features have soft X-ray counterparts, in one case shifted by ~ 2' arcmin toward the remnant interior. The spectra of X-ray emission from both isolated features have photon index <~ 2.0 in the MECS regime. The emission detected from the remnant with PDS detector extends up to 100 keV. We discuss the observed properties of the hard X-ray features in relation to non-thermal emission from shocked molecular clumps and pulsar wind nebula.

Bocchino, F.; Bykov, A. M.

2000-10-01

142

The X-ray corona of Procyon  

NASA Technical Reports Server (NTRS)

X-ray emission from the nearby system Procyon A/B (F5 IV + DF) was detected, using the IPC (Imaging Proportional Counter) on board the Einstein Observatory. Analysis of the X-ray pulse height spectrum suggests that the observed X-ray emission originates in Procyon A rather than in the white dwarf companion Procyon B, since the derived X-ray temperature, log T = 6.2, agrees well with temperatures found for quiescent solar X-ray emission. Modeling Procyon's corona with loops characterized by some apex temperature Tmax and emission length scale L, it is found that Tmax is well constrained, but L, and consequently the filling factor of the X-ray emitting gas, are essentially unconstrained even when EUV emission from the transition region is included in the analysis.

Schmitt, J. H. M. M.; Harnden, F. R., Jr.; Rosner, R.; Peres, G.; Serio, S.

1985-01-01

143

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

144

Internal Energy Dissipation of Gamma-Ray Bursts Observed with Swift: Precursors, Prompt Gamma-Rays, Extended Emission, and Late X-Ray Flares  

NASA Astrophysics Data System (ADS)

We jointly analyze the gamma-ray burst (GRB) data observed with Burst Alert Telescope (BAT) and X-ray Telescope on board the Swift mission to present a global view on the internal energy dissipation processes in GRBs, including precursors, prompt gamma-ray emission, extended soft gamma-ray emission, and late X-ray flares. The Bayesian block method is utilized to analyze the BAT light curves to identify various emission episodes. Our results suggest that these emission components likely share the same physical origin, which is the repeated activation of the GRB central engine. What we observe in the gamma-ray band may be a small part of more extended underlying activities. The precursor emission, which is detected in about 10% of Swift GRBs, is preferably detected in those GRBs that have a massive star core-collapse origin. The soft extended emission tail, on the other hand, is preferably detected in those GRBs that have a compact star merger origin. Bright X-ray emission is detected during the BAT quiescent phases prior to subsequent gamma-ray peaks, implying that X-ray emission may be detectable prior the BAT trigger time. Future GRB alert instruments with soft X-ray capability are essential for revealing the early stages of GRB central engine activities, and shedding light on jet composition and the jet launching mechanism in GRBs.

Hu, You-Dong; Liang, En-Wei; Xi, Shao-Qiang; Peng, Fang-Kun; Lu, Rui-Jing; Lü, Lian-Zhong; Zhang, Bing

2014-07-01

145

X-ray emission from charge exchange of highly-charged ions in atoms and molecules  

NASA Technical Reports Server (NTRS)

Charge exchange followed by radiative stabilization are the main processes responsible for the recent observations of X-ray emission from comets in their approach to the Sun. A new apparatus was constructed to measure, in collisions of HCIs with atoms and molecules, (a) absolute cross sections for single and multiple charge exchange, and (b) normalized X-ray emission cross sections.

Greenwood, J. B.; Williams, I. D.; Smith, S. J.; Chutjian, A.

2000-01-01

146

Ultrahigh-Resolution Studies of Heavy-Ion-Induced X-Ray Satellite Emission.  

National Technical Information Service (NTIS)

We studied K/sub alpha / X-ray emission from sulfur compounds and L X-ray emission from molybdenum metal induced by 34 MeV Cl/sup q exp + / ion bombardment. The measurements were made with an energy resolution high enough to observe the principal multiple...

C. R. Vane E. Kaellne Kaellne G. Morford S. Raman

1984-01-01

147

Young Binary DQ Tau: The hunt for X-ray emission from colliding magnetospheres (GO part)  

NASA Astrophysics Data System (ADS)

The young high eccentricity binary DQ Tau exhibits powerful periodic mm flaring attributed to magnetosphere collisions of binary components. Simultaneous with mm CARMA, we propose combined GTO+GO Chandra ACIS-I3 observation of the periastron passage to search for X-ray emission from colliding magnetospheres. Properties of the discovered X-rays will be compared to those of the known X-rays at the orbital phase away from periastron. To give insights into the mechanism of X-ray production, morphology, energetics, magnetic field strengths, sizes of X-ray emitting coronal structures will be inferred and compared to those of the big COUP X-ray flares (Getman et al. 2008). This project has potential to offer us a different window to the origin of X-rays from young stars.

Getman, Konstantin

2009-09-01

148

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

NASA Technical Reports Server (NTRS)

X-ray emission from the massive stellar binary system, Eta 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 Eta 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.

2012-01-01

149

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

150

Production of Loop-Top Hard X-Ray Emission  

NASA Technical Reports Server (NTRS)

The main goal of this work has been to understand the particle acceleration mechanism (or mechanisms) in impulsive solar flares, using hard X-ray observations of high spatial and spectral resolution. Several new observations, including the observations by YOHKOH that reveal emission from both footpoints and loop tops, have suggested to us that a model employing stochastic acceleration is the most likely candidate for explaining energetic particles in a majority (if not all) of impulsive flares. In this model, most of the flare energy is initially converted into plasma waves and turbulence, which in turn can accelerate particles from thermal to relativistic energies on sub-second timescales. This research has provided important tools for the interpretation of the high spectral and spatial resolution observations obtained from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) . In the course of our research, we have focused on two different (but possibly related) stochastic acceleration models: (1) a model that employs high-frequency whistler turbulence and concentrates on the energetic electrons, and (2) a model that employs low frequency MHD waves, and is able to accelerate both the ambient electrons and ions.

Miller, James A.; Seaquist, Valerie

2003-01-01

151

X-ray emission from high temperature plasmas  

NASA Technical Reports Server (NTRS)

The physical processes occurring in plasma focus devices were studied. These devices produce dense high temperature plasmas, which emit X rays of hundreds of KeV energy and one to ten billion neutrons per pulse. The processes in the devices seem related to solar flare phenomena, and would also be of interest for controlled thermonuclear fusion applications. The high intensity, short duration bursts of X rays and neutrons could also possibly be used for pumping nuclear lasers.

Harries, W. L.

1976-01-01

152

X-ray emission lines from cooling flows  

NASA Technical Reports Server (NTRS)

Techniques employing individual X-ray line strengths to estimate the rate at which gas cools in the intracluster medium are discussed. It is demonstrated that departures from ionization equilibrium in the cooling plasma are not important at X-ray temperatures. Nonrestrictive upper limits are obtained for four cooling flow clusters. The results favor the existence of substantial cooling flows and argue against the dominance of conduction or other heat sources.

Canizares, Claude R.; Markert, Thomas H.; Donahue, Megan E.

1988-01-01

153

X-ray Emission From Sn Ia 1885a & 1985g?  

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

2012-01-01

154

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

155

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

156

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

157

EVIDENCE OF NON-THERMAL X-RAY EMISSION FROM HH 80  

SciTech Connect

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{sup –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. [Instituto de Matemática Interdisciplinar, S. D. Astronomía y Geodesia, Facultad de Ciencias Matemáticas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)] [Instituto de Matemática Interdisciplinar, S. D. Astronomía y Geodesia, Facultad de Ciencias Matemáticas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Peri, C. S.; Benaglia, P. [Instituto Argentino de Radioastronomía (IAR), CCT La Plata (CONICET), C.C.5, 1894 Villa Elisa, Buenos Aires (Argentina)] [Instituto Argentino de Radioastronomía (IAR), CCT La Plata (CONICET), C.C.5, 1894 Villa Elisa, Buenos Aires (Argentina); Bonito, R. [Dipartimento di Fisica e Chimica, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy)] [Dipartimento di Fisica e Chimica, Università di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy); Miceli, M. [INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy)] [INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo (Italy); Albacete-Colombo, J. F. [Universidad Nacional del COMAHUE, Monseñor Esandi y Ayacucho, 8500 Viedma, Río Negro (Argentina)] [Universidad Nacional del COMAHUE, Monseñor Esandi y Ayacucho, 8500 Viedma, Río Negro (Argentina); De Castro, E. [Dpto. de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid (Spain)] [Dpto. de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

2013-10-20

158

X-Ray Emission from the Halo of M31  

NASA Technical Reports Server (NTRS)

Our goal was to use short (10 ksec) observations of selected fields in the halo of M31, to determine the size and characteristics of its X-ray population and to study the connection between globular clusters and X-ray sources. The program of observations has yet to be successfully completed. We received acceptable data from just 2 of the 5 approved fields. Nevertheless, the results were intriguing and we have submitted a paper based on this data to Nature. We find that the X-ray source density is significantly enhanced in the vicinity of one GC, providing the first observational evidence supporting the ejection hypothesis. We also find additional X-ray sources, including some which are very soft, in large enough numbers to suggest that not all could have been formed in GCs. That is, some must be descended from the same primordial halo population that produced any compact stars comprising part of the halo's dark matter. Extrapolating fiom the X-ray source population, we estimate that stellar remnants and dim old stars in the halo could comprise as much as 25% of the estimated mass (approx. 10(exp 12) Solar Mass) of the halo. These results suggest that the other approved fields should be observed soon and also provide strong motivation for the future XMM-Newton programs.

Mushotzky, Richard (Technical Monitor); DiStefano, Rosanne

2004-01-01

159

The structure of X-ray emissions from triggered lightning leaders measured by a pinhole-type X-ray camera  

NASA Astrophysics Data System (ADS)

We investigate the structure of X-ray emissions from downward triggered lightning leaders using a pinhole-type X-ray camera (XCAM) located at the International Center for Lightning Research and Testing. This study builds on the work of Dwyer et al. (2011), which reported results from XCAM data from the 2010 summer lightning season. Additional details regarding the 2010 data are reported here. During the 2011 summer lightning season, the XCAM recorded 12 out of 17 leaders, 5 of which show downward leader propagation. Of those five leaders, one dart-stepped leader and two chaotic dart leaders are the focus of this paper. These three leaders displayed unique X-ray emission patterns: a chaotic dart leader displayed a diffuse structure (i.e., a wide lateral "spraying" distribution of X-rays), and a dart-stepped leader and a chaotic dart leader exhibited compact emission (i.e., a narrow lateral distribution of strong X-ray emission). These two distinct X-ray emission patterns (compact and diffuse) illustrate the variability of lightning leaders. Using Monte Carlo simulations, we show that the diffuse X-ray source must originate from a diffuse source of energetic electrons or possibly emission from several sources. The compact X-ray sources originate from compact electron sources, and the X-ray source region radius and electric charge contained within the X-ray source region were between 2 and 3 m and on the order of 10-4 C, respectively. For the leaders under investigation, the X-ray source region average currents were determined to be on the order of 102 A.

Schaal, M. M.; Dwyer, J. R.; Arabshahi, S.; Cramer, E. S.; Lucia, R. J.; Liu, N. Y.; Rassoul, H. K.; Smith, D. M.; Matten, J. W.; Reid, A. G.; Hill, J. D.; Jordan, D. M.; Uman, M. A.

2014-01-01

160

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

161

DISCOVERY OF X-RAY EMISSION FROM YOUNG SUNS IN THE SMALL MAGELLANIC CLOUD  

SciTech Connect

We report the discovery of extended X-ray emission within the young star cluster NGC 602a in the Wing of the Small Magellanic Cloud (SMC) based on observations obtained with the Chandra X-Ray Observatory. X-ray emission is detected from the cluster core area with the highest stellar density and from a dusty ridge surrounding the H II region. We use a census of massive stars in the cluster to demonstrate that a cluster wind or wind-blown bubble is unlikely to provide a significant contribution to the X-ray emission detected from the central area of the cluster. We therefore suggest that X-ray emission at the cluster core originates from an ensemble of low- and solar-mass pre-main-sequence (PMS) stars, each of which would be too weak in X-rays to be detected individually. We attribute the X-ray emission from the dusty ridge to the embedded tight cluster of the newborn stars known in this area from infrared studies. Assuming that the levels of X-ray activity in young stars in the low-metallicity environment of NGC 602a are comparable to their Galactic counterparts, then the detected spatial distribution, spectral properties, and level of X-ray emission are largely consistent with those expected from low- and solar-mass PMS stars and young stellar objects (YSOs). This is the first discovery of X-ray emission attributable to PMS stars and YSOs in the SMC, which suggests that the accretion and dynamo processes in young, low-mass objects in the SMC resemble those in the Galaxy.

Oskinova, L. M.; Hainich, R. [Institute for Physics and Astronomy, University Potsdam, D-14476 Potsdam (Germany)] [Institute for Physics and Astronomy, University Potsdam, D-14476 Potsdam (Germany); Sun, W.; Chen, Y. [Department of Astronomy, Nanjing University, Nanjing, 210093 Jiangsu (China)] [Department of Astronomy, Nanjing University, Nanjing, 210093 Jiangsu (China); Evans, C. J. [UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)] [UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Henault-Brunet, V. [Scottish Universities Physics Alliance (SUPA), Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)] [Scottish Universities Physics Alliance (SUPA), Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Chu, Y.-H.; Gruendl, R. A. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States)] [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Gallagher, J. S. III [Department of Astronomy, University of Wisconsin-Madison, 5534 Sterling, 475 North Charter Street, Madison, WI 53706 (United States)] [Department of Astronomy, University of Wisconsin-Madison, 5534 Sterling, 475 North Charter Street, Madison, WI 53706 (United States); Guerrero, M. A. [Instituto de Astrofisica de Andalucia, IAA-CSIC, Glorieta de la Astronomia s/n, E-18008 Granada (Spain)] [Instituto de Astrofisica de Andalucia, IAA-CSIC, Glorieta de la Astronomia s/n, E-18008 Granada (Spain); Guedel, M. [Department of Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, A-1180 Vienna (Austria)] [Department of Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, A-1180 Vienna (Austria); Silich, S. [Instituto Nacional de Astrofisica Optica y Electronica, AP 51, 72000 Puebla (Mexico)] [Instituto Nacional de Astrofisica Optica y Electronica, AP 51, 72000 Puebla (Mexico); Naze, Y. [GAPHE, Departement AGO, Universite de Liege, Allee du 6 Aout 17, Bat. B5C, B-4000 Liege (Belgium)] [GAPHE, Departement AGO, Universite de Liege, Allee du 6 Aout 17, Bat. B5C, B-4000 Liege (Belgium); Reyes-Iturbide, J. [LATO-DCET/Universidade Estadual de Santa Cruz, Rodovia Jorge Amado, km 16, 45662-000 Ilheus, BA (Brazil)] [LATO-DCET/Universidade Estadual de Santa Cruz, Rodovia Jorge Amado, km 16, 45662-000 Ilheus, BA (Brazil)

2013-03-01

162

High energy X-ray emission driven by high voltage circuit system  

NASA Astrophysics Data System (ADS)

The x-rays are produced by high voltage discharge applied inside plasma source interaction chamber; the control circuit system of high voltage is composed of a power supply and a LC-inverter. The goal of the project is based on the production of x-rays by a plasma to increase the efficiency of a classic x-ray tube with hot filament. Preliminary results of high energy x-rays emission, the layout and simulation with p-spice of the high voltage system are presented.

Emilio, M. Di Paolo; Palladino, L.

2014-04-01

163

Observation of soft X-ray emission from the supernova remnant HB9  

NASA Technical Reports Server (NTRS)

The number of known X-ray emitting supernova remnants in our galaxy has significantly grown as a result of the soft X-ray survey by the HEAO-1 spacecraft. The HEAO-1 A-2 experiment has observed soft X-ray emission from the old supernova remnant HB9 which lies close to the previously identified X-ray source, Capella. Spectral data and the low optical obscuration in the direction of the remnant suggest that HB9 is a good candidate for detecting Fe XIV coronal forbidden-line emission. Mapping of the coronal line emission in association with the imaging X-ray data expected from HEAO-2 would allow the temperature profile of the emitting shell to be determined in a manner similar to that used by Tuohy, Nousek, and Garmire (1979) for the Cygnus Loop, which is in a similar evolutionary phase to HB9.

Tuohy, I. R.; Clark, D. H.; Garmire, G. P.

1979-01-01

164

Particle induced x-ray emission (PIXE) measurement of the Cd content in animal tissues.  

National Technical Information Service (NTIS)

Particle induced x-ray emission (PIXE) measurements were performed on thin samples prepared from different rabbit tissues, using 3 MeV proton beam for inducing x-rays from the animal tissues. This method is very sensitive and very small amounts of trace e...

Le Huong Quynh I. Demeter K. Hollos-Nagy Z. Szoekefalvi-Nagy

1989-01-01

165

Optical Emission from Cooling Flows in Distant X ray Clusters of Galaxies.  

National Technical Information Service (NTIS)

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 ...

M. Donahue J. T. Stocke G. M. Voit I. Gioia

1990-01-01

166

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

Microsoft Academic Search

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

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

1990-01-01

167

A Study of Nonthermal X-Ray and Radio Emission from the O Star 9 Sgr  

NASA Technical Reports Server (NTRS)

The observed X-ray and highly variable nonthermal radio emission from OB stars has eluded explanation for more than 18 years. The most favorable model of X-ray production in these stars (shocks) predicts both nonthermal radio and X-ray emission. The nonthermal X-ray emission should occur above 2 keV and the variability of this X-ray component should also be comparable to the observed radio variability. To test this scenario, we proposed an ASC/VLA monitoring program to observe the OB star, 9 Sgr, a well known nonthermal, variable radio source and a strong X-ray source. We requested 625 ks ASCA observations with a temporal spacing of approximately 4 days which corresponds to the time required for a density disturbance to propagate to the 6 cm radio free-free photosphere. The X-ray observations were coordinated with 5 multi-wavelength VLA observations. These observations represent the first systematic attempt to investigate the relationship between the X-ray and radio emission in OB stars.

Waldron, Wayne L.; Corcoran, Michael F.; Drake, Stephen A.

1999-01-01

168

Soft X-ray Emission from Alexandrite Laser-Matter-Interaction.  

National Technical Information Service (NTIS)

X-ray spectroscopy was used to quantify the plasma generated by a focused, Alexandrite laser as a potential alternative source in proximity lithography. An x-ray emission efficiency of 2 - 11% was determined by analysis of spectral data (10 - 14A) from tr...

P. G. Burkhalter D. J. Harter E. F. Gabl P. Bado D. A. Newman

1993-01-01

169

Magnetic fields in A-type stars associated with X-ray emission  

NASA Astrophysics Data System (ADS)

A common explanation for the observed X-ray emission of A-type stars is the presence of a hidden late-type companion. While this assumption can be shown to be correct in some cases, a number of lines of evidence suggests that low-mass companions cannot be the correct cause for the observed activity in all cases. A model explains the X-ray emission for magnetic Ap/Bp stars, focusing on the A0p star IQ Aur. In this paper we test whether this theoretical model is able to explain the observed X-ray emission. We present the observations of 13 A-type stars that have been associated with X-ray emission detected by ROSAT. To determine the mean longitudinal magnetic field strength we measured the circular polarization in the wings of the Balmer lines using FORS1. Although the emission of those objects that possess magnetic fields fits the prediction of the Babel and Montmerle model, not all X-ray detections are connected to the presence of a magnetic field. Additionally, the measured magnetic fields do not correlate with the X-ray luminosity. Accordingly, the magnetically confined wind shock model cannot explain the X-ray emission from all the presented stars.

Schröder, C.; Hubrig, S.; Schmitt, J. H. M. M.

2008-06-01

170

Heavy ion induced Auger electron, x-ray, and optical emission from a solid state surface  

SciTech Connect

The experiments examine the relaxation phenomena of Auger electron, x-ray, and optical emission during the medium-keV heavy-ion bombardment of a solid state surface. Auger electron energy spectra, x-ray, and optical spectra induced by Ar/sup +/ and Ne/sup +/ ions with energies within the 100-350 keV range were recorded at the same time. The spectral structure observed for each of the emissions has provided information on electronic transitions, selected thin-foil sputtering yields and particle-induced x-ray emission cross sections.

Trbojevic, D.

1984-01-01

171

A NEW CORRELATION BETWEEN GRB X-RAY FLARES AND THE PROMPT EMISSION  

SciTech Connect

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. [Department of Physics, University of Adiyaman, 02040 Adiyaman (Turkey); MacLachlan, G. A.; Shenoy, A.; Dhuga, K. S.; Parke, W. C., E-mail: edasonbas@yahoo.com [Department of Physics, George Washington University, Washington, DC 20052 (United States)

2013-04-20

172

X-Ray Emission from Clusters of Galaxies: Latest Developments  

Microsoft Academic Search

Significant progress has been made a) in the use of clusters as cosmological probes and b) in demonstrating the roles of heating and cooling of dense intracluster gas. a) The baryon fraction in clusters, which is well-measured directly with X-ray observations, should be constant with cosmic epoch and so can be used to measure cluster distance. This gives a determination

Andrew Fabian

2004-01-01

173

High Resolution X-Ray Astronomy with the Chandra Observatory Stellar Point Sources and Extended Gaseous Emission of Cen Chandra X-Ray Observations of Clusters of Galaxies  

NASA Technical Reports Server (NTRS)

I will introduce the Chandra Observatory and new results obtained during the Chandra OAC phase. These include the newly discovered X-ray jet in PKS 0637-752; X-ray jet, characteristics of point sources and extended emission in Cen A; and contact discontinuities and merger evidence of A2142.

Kim, Dong-Woo

2000-01-01

174

Detection of x-ray emission in a nanosecond discharge in air at atmospheric pressure  

SciTech Connect

Measurement of x-ray emission is an important parameter to investigate runaway behavior of fast electrons produced in nanosecond-pulse gas discharge. An online detection system of x rays is described in this paper, and the system consists of an x-ray detector with NaI (Tl) scintillator and photomultiplier tube, and an integrated multichannel analyzer. The system is responsible for detecting x-ray emission signal, processing the detected signals, and scaling the energy distribution. The calibration results show that every channel of the detection system represents a given x-ray energy and various x rays can be divided into different energy ranges between 10 and 130 keV. For a repetitive nanosecond-pulse breakdown between highly nonuniform gaps in open air, an energy distribution is obtained using the online detection system. It shows that the x-ray emission is a continuous spectrum and the x rays of above 60 keV dominate in the detected energy distribution.

Zhang Cheng; Yu Yang; Niu Zheng; Yan Ping [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Shao Tao [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China); State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments, Electrical Engineering Department, Tsinghua University, Beijing 100084 (China); Zhou Yuanxiang [State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments, Electrical Engineering Department, Tsinghua University, Beijing 100084 (China)

2010-11-15

175

Polarized infrared emission from X-ray binary jets  

NASA Astrophysics Data System (ADS)

Near-infrared (NIR) and optical polarimetric observations of a selection of X-ray binaries are presented. The targets were observed using the Very Large Telescope and the United Kingdom Infrared Telescope. We detect a significant level (3?) of linear polarization in four sources. The polarization is found to be intrinsic (at the >3? level) in two sources; GRO J1655-40 (~4-7 per cent in the H and Ks bands during an outburst) and Sco X-1 (~0.1-0.9 per cent in the H and K bands), which is stronger at lower frequencies. This is likely to be the signature of optically thin synchrotron emission from the collimated jets in these systems, whose presence indicates that a partially ordered magnetic field is present at the inner regions of the jets. In Sco X-1, the intrinsic polarization is variable (and sometimes absent) in the H and K bands. In the J band (i.e. at higher frequencies), the polarization is not significantly variable and is consistent with an interstellar origin. The optical light from GX 339-4 is also polarized, but at a level and position angle consistent with scattering by interstellar dust. The other polarized source is SS 433, which has a low level (0.5-0.8 per cent) of J-band polarization, likely due to local scattering. The NIR counterparts of GRO J0422+32, XTE J1118+480, 4U 0614+09 and Aql X-1 (which were all in or near quiescence) have a linear polarization level of <16 per cent (3? upper limit, some are <6 per cent). We discuss how such observations may be used to constrain the ordering of the magnetic field close to the base of the jet in such systems. Based on observations collected at the European Southern Observatory, Chile, under ESO Programme IDs 076.D-0497 and 275.D-5062. E-mail: davidr@science.uva.nl (DMR); rpf@phys.soton.ac.uk (RPF)

Russell, David M.; Fender, Rob P.

2008-06-01

176

A Comparison of X-Ray and Optical Emission in Cassiopeia A  

NASA Astrophysics Data System (ADS)

Broadband optical and narrowband Si XIII X-ray images of the young Galactic supernova remnant Cassiopeia A (Cas A) obtained over several decades are used to investigate spatial and temporal emission correlations on both large and small angular scales. The data examined consist of optical and near-infrared ground-based and Hubble Space Telescope images taken between 1951 and 2011, and of X-ray images from Einstein, ROSAT, and Chandra taken between 1979 and 2013. We find weak spatial correlations between the remnant's X-ray and optical emission features on large scales, but several cases of good optical/X-ray correlations on small scales for features which have brightened due to recent interactions with the reverse shock. We also find instances (1) where a time delay is observed between the appearance of a feature's optical and X-ray emissions, (2) of displacements of several arcseconds between a feature's X-ray and optical emission peaks, and (3) of regions showing no corresponding X-ray or optical emissions. To explain this behavior, we propose a highly inhomogeneous density model for Cas A's ejecta consisting of small, dense optically emitting knots (n ~102-3 cm–3) and a much lower density (n ~0.1-1 cm–3) diffuse X-ray emitting component often spatially associated with optical emission knots. The X-ray emitting component is sometimes linked to optical clumps through shock-induced mass ablation generating trailing material leading to spatially offset X-ray/optical emissions. A range of ejecta densities can also explain the observed X-ray/optical time delays since the remnant's ?5000 km s–1 reverse shock heats dense ejecta clumps to temperatures around 3 × 104 K relatively quickly, which then become optically bright while more diffuse ejecta become X-ray bright on longer timescales. Highly inhomogeneous ejecta as proposed here for Cas A may help explain some of the X-ray/optical emission features seen in other young core-collapse supernova remnants.

Patnaude, Daniel J.; Fesen, Robert A.

2014-07-01

177

Carbon nanotube based microfocus field emission x-ray source for microcomputed tomography  

SciTech Connect

Microcomputed tomography is now widely used for in vivo small animal imaging for cancer studies. Achieving high imaging quality of live objects requires the x-ray source to have both high spatial and temporal resolutions. Preliminary studies have shown that carbon nanotube (CNT) based field emission x-ray source has significant intrinsic advantages over the conventional thermionic x-ray tube including better temporal resolution and programmability. Here we report the design and characterization of a CNT based field emission x-ray source that also affords a high spatial resolution. The device uses modified asymmetric Einzel lenses for electron focusing and an elliptical shaped CNT cathode patterned by photolithography. Stable and small isotropic x-ray focal spot sizes were obtained.

Liu Zejian; Yang Guang; Lee, Yueh Z.; Bordelon, David; Lu Jianping; Zhou, Otto [Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Curriculum in Applied and Materials Sciences, 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)

2006-09-04

178

Suzaku Detection of Diffuse Hard X-Ray Emission Outside Vela X  

NASA Technical Reports Server (NTRS)

Vela X is a large, 3 deg x 2 deg, radio-emitting pulsar wind nebula (PWN) powered by the Vela pulsar in the Vela supernova remnant. Using four Suzaku/XIS observations pointed just outside Vela X, we find hard X-ray emission extending throughout the fields of view. The hard X-ray spectra are well represented by a power-law. The photon index is measured to be constant at Gamma approximates 2.4, similar to that of the southern outer part of Vela X. The power-law flux decreases with increasing distance from the pulsar. These properties lead us to propose that the hard X-ray emission is associated with the Vela PWN. The larger X-ray extension found in this work strongly suggests that distinct populations relativistic electrons form the X-ray PWN and Vela X, as was recently inferred from multiwavelength spectral modeling of Vela X.

Katsuda, Satoru; Mori, Koji; Petre, Robert; Yamaguchi, Hiroya; Tsunemi, Hiroshi; Bocchino, Fabrizio; Bamba, Aya; Miceli, Marco; Hewitt, John W.; Temim, Tea; Uchida, Hiroyuki; Yoshii, Rie

2011-01-01

179

X-Ray Emission from Ultraviolet Luminous Galaxies and Lyman Break Galaxies  

NASA Technical Reports Server (NTRS)

We present results from an XMM mini-survey of GALEX-selected Ultraviolet-Luminous Galaxies (UVLGs) that appear to include an interesting subset that are analogs to the distant (3X-ray emission of LBGs appear to be broadly similar to that of galaxies in the local Universe, possibly indicating similarity in the production of accreting binaries over large evolutionary timescales in the Universe. We have detected luminous X-ray emission from one UVLG that permits basic X-ray spectroscopic analysis, and have direct X-ray constraints on a total of 6 UVLGs. We find evidence for likely large scatter in the assumed X-ray/star-formation rate relation for LBGs.

Hornschemeier, Ann; Ptak, A. F.; Salim, S.; Heckman, T. P.; Overzier, R.; Mallery, R.; Rich, M.; Strickland, D.; Grimes, J.

2009-01-01

180

U. radio emission from quiescent filaments  

NASA Technical Reports Server (NTRS)

Full-disk Very Large Array (VLA) synthesis maps of the quiet Sun indicate that filaments can be seen in emission at 91.6 cm wavelength; they are detected in absorption at shorter microwave wavelengths. The 91.6 cm emission has a brightness temperature of T sub B = 3 x 10(exp 5) K. It is hotter, wider and longer than the underlying filament detected at H alpha wavelengths, but the similarity between the shape, position, elongation and orientation of the radio and optical features suggests their close association. The 91.6 cm emission is attributed to the thermal-bremsstrahlung of a hot transition sheath that envelopes the H alpha filament and acts as an interface between the cool, dense H alpha filament and the hotter, rarefied corona. The transition sheath is seen in emission because of the lower optical depth of the corona at 90 cm wavelength, and the width of this sheet is 10(exp 9) cm. A power law gradient in pressure provides a better match to the observations than a constant pressure model; definitive tests of theoretical models await simultaneous multi-wavelength studies of filaments at different observing angles. When the thermal bremsstrahlung is optically thin, the magnetic field strength in the transition sheath can be inferred from the observed circular polarization. Variable physical parameters of the sheath, such as width, electron density, and electron temperature, can explain controversial reports of the detection of, or the failure to detect, the meter-wavelength counterpart of H alpha filaments.

Lang, Kenneth R.

1989-01-01

181

Theory of the azimuthal distribution of molecular orbital x-ray emission  

NASA Astrophysics Data System (ADS)

Full dynamical calculations, including electron slip, of molecular-orbital X-ray emission in heavy-ion-atom collisions give very small azimuthal anisotropies, in qualitative agreement with experiments.

Anholt, R.

1981-07-01

182

Extended X-Ray Emission from a Quasar-driven Superbubble  

NASA Astrophysics Data System (ADS)

We present observations of extended, 20 kpc scale soft X-ray gas around a luminous obscured quasar hosted by an ultraluminous infrared galaxy caught in the midst of a major merger. The extended X-ray emission is well fit as a thermal gas with a temperature of kT ?280 eV and a luminosity of L X ? 1042 erg s-1 and is spatially coincident with a known ionized gas outflow. Based on the X-ray luminosity, a factor of ~10 fainter than the [O III] emission, we conclude that the X-ray emission is either dominated by photoionization, or by shocked emission from cloud surfaces in a hot quasar-driven wind.

Greene, Jenny E.; Pooley, David; Zakamska, Nadia L.; Comerford, Julia M.; Sun, Ai-Lei

2014-06-01

183

Continuum x-ray emission from the Alcator A tokamak  

SciTech Connect

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 (Z/sub eff/approx.1), Maxwellian distributions. Temperature profiles are provided. When v/sub d//v/sub th/> or approx. =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, J.E.; Molvig, K.; Helava, H.I.

1982-03-01

184

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

185

Suzaku Detection of Extended/Diffuse Hard X-Ray Emission from the Galactic Center  

NASA Astrophysics Data System (ADS)

Five on-plane regions within ±0°.8 of the galactic center were observed with the Hard X-ray Detector (HXD) and the X-ray Imaging Spectrometer (XIS) aboard Suzaku. From all regions, significant hard X-ray emission was detected with HXD-PIN up to 40keV, in addition to the extended plasma emission which is dominant in the XIS band. The hard X-ray signals are inferred to come primarily from a spatially extended source, rather than from a small number of bright discrete objects. Contributions to the HXD data from catalogued X-ray sources, typically brighter than 1mCrab, were estimated and removed using information from Suzaku and other satellites. Even after this removal, the hard X-ray signals remained significant, exhibiting a typical 12-40keV surface brightness of 4×10-10 erg cm-2 s-1 deg-2 and power-law-like spectra with a photon index of 1.8. Combined fittings to the XIS and HXD-PIN spectra confirm that a separate hard tail component is superposed onto the hot thermal emission, confirming a previous report based on the XIS data. Over the 5--40keV band, the hard tail is spectrally approximated by a power law of photon index ˜2, but better by those with somewhat convex shapes. Possible origins of the extended hard X-ray emission are discussed.

Yuasa, Takayuki; Tamura, Ken-Ichi; Nakazawa, Kazuhiro; Kokubun, Motohide; Makishima, Kazuo; Bamba, Aya; Maeda, Yoshitomo; Takahashi, Tadayuki; Ebisawa, Ken; Senda, Atsushi; Hyodo, Yoshiaki; Tsuru, Takeshi Go; Koyama, Katsuji; Yamauchi, Shigeo; Takahashi, Hiromitsu

2008-01-01

186

Molybdenum and chlorine x-ray emission from Alcator A  

SciTech Connect

High-resolution (..delta..lambda/lambda approx. = 0.015) x-ray spectra in the wavelength region 3.7 ..-->.. 6.2 A (3.4 ..-->.. 2.0 keV) have been collected from the Alcator tokamak using a flat crystal Bragg monochromator. Molybdenum L lines and chlorine K lines have been observed and charge-state identifications have been made by comparison with calculations.

Rice, J.E.; Marmar, E.S.; Coan, T.; Allen, S.L.; Cowan, R.D.

1980-07-01

187

X-ray emission from clusters and groups of galaxies  

PubMed Central

Recent major advances in x-ray imaging and spectroscopy of clusters have allowed the determination of their mass and mass profile out to ?1/2 the virial radius. In rich clusters, most of the baryonic mass is in the gas phase, and the ratio of mass in gas/stars varies by a factor of 2–4. The baryonic fractions vary by a factor of ?3 from cluster to cluster and almost always exceed 0.09 h50?[3/2] and thus are in fundamental conflict with the assumption of ? = 1 and the results of big bang nucleosynthesis. The derived Fe abundances are 0.2–0.45 solar, and the abundances of O and Si for low redshift systems are 0.6–1.0 solar. This distribution is consistent with an origin in pure type II supernova. The amount of light and energy produced by these supernovae is very large, indicating their importance in influencing the formation of clusters and galaxies. The lack of evolution of Fe to a redshift of z ? 0.4 argues for very early enrichment of the cluster gas. Groups show a wide range of abundances, 0.1–0.5 solar. The results of an x-ray survey indicate that the contribution of groups to the mass density of the universe is likely to be larger than 0.1 h50?2. Many of the very poor groups have large x-ray halos and are filled with small galaxies whose velocity dispersion is a good match to the x-ray temperatures.

Mushotzky, Richard

1998-01-01

188

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

NASA Technical Reports Server (NTRS)

The proposed research uses the electron beam ion trap at the Lawrence Livermore National Laboratory (LLNL) to study X-ray emission from charge-exchange recombination of highly charged ions with neutral gases. The resulting data fill a void in existing experimental and theoretical understanding of this atomic physics process, and are needed to explain all or part of the observed X-ray emission from the soft X-ray background, stellar winds, the Galactic Center, supernova ejecta, and photoionized nebulae. Progress made during the first year of the grant is described, as is work planned for the second year.

Wargelin, B.

2002-01-01

189

Catalytic action of beta source on x-ray emission from plasma focus  

Microsoft Academic Search

The influence of preionization around the insulator sleeve by a mesh-type beta source (28Ni63) for the x-ray emission from a (2.3-3.9 kJ) plasma focus device is investigated. Quantrad Si p-i-n diodes along with suitable filters are employed as time-resolved x-ray detectors and a multipinhole camera with absorption filters is used for time-integrated analysis. X-ray emission in 4pi geometry is measured

S. Ahmad; Mehboob Sadiq; S. Hussain; M. Shafiq; M. Zakaullah; A. Waheed

2006-01-01

190

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

191

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

192

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

193

Alpha Particle Induced X-ray Emission in the Classroom  

SciTech Connect

We report on an experimental demonstration in an introductory modern physics course to elucidate the X-ray line spectra, and how they arise from transitions of electrons to inner shells. We seek to determine the effect of limited use of an interactive component as a supplement to a traditional lecture, and how it would improve the student achievement. In this preliminary study the students were exposed to traditional lectures on X-ray production and Bohr's model, they then were given a homework on the abc of X-ray spectra, after which they were given a pre-test on the materials, followed by an in-class demonstration, and a final post-exam. The gain, as measured from pre- to post-exams appears to remark the differences in how students approached the subject before and after the use of the demonstration. This initial study shows the validity of in-class demonstrations as teaching tools and opens a wide new area of research in modern physics teaching.

Lopez, Jorge A.; Borunda, Mario F.; Morales, Jaime [Department of Physics, University of Texas at El Paso, El Paso, Texas 79968 (United States)

2003-08-26

194

Resonant emission in the X-ray spectra. I. transition 3d metal dioxides  

Microsoft Academic Search

The calculations of the electronic structure and X-ray spectra of the MO68- (M = Ti, V, Cr, Mn) clusters, which were used as models for respective solid state dioxides, have been performed by the Xalpha-DV method. The one-electron model for resonant emission (reemission) was used. The calculations show, that X-ray resonant emission significantly affects the shape of the ML2,3 and

N. V. Dobrodey; A. V. Kondratenko; G. L. Gutsev; V. P. Krivitsky; Yu A. Nosatschov

1993-01-01

195

Resonant emission in the X-ray spectra. I. transition 3d metal dioxides  

Microsoft Academic Search

The calculations of the electronic structure and X-ray spectra of the MO68? (M = Ti, V, Cr, Mn) clusters, which were used as models for respective solid state dioxides, have been performed by the X?-DV method. The one-electron model for resonant emission (reemission) was used. The calculations show, that X-ray resonant emission significantly affects the shape of the ML2,3 and

N V Dobrodey; A V Kondratenko; G L Gutsev; V P Krivitsky; Yu A Nosatschov

1993-01-01

196

Soft X-ray emission from gamma-ray bursts observed with GINGA  

Microsoft Academic Search

The soft X-ray emission of gamma-ray bursts below 10 keV provides information about size, location, and emission mechanism. The gamma-ray burst detector on Ginga, which consists of a proportional counter and a scintillation detector, covers an energy range down to 1.5 keV with 63-sq cm effective area. In several of the observed gamma-ray bursts, the intensity of the soft X-ray

A. Yoshida; T. Murakami; M. Itoh; J. Nishimura; T. Tsuchiya; E. E. Fenimore; R. W. Klebesadel; W. D. Evans; I. Kondo; N. Kawai

1989-01-01

197

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

NASA Technical Reports Server (NTRS)

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

Wargelin, B.

2003-01-01

198

Autoionization emission for x-ray-excited Auger spectra in the Compton-scattering process  

SciTech Connect

Autoionization emission in the 3d transition-metal series is observed for the x-ray-excited Auger electrons in the Compton-scattering process. Kinematical analysis of Compton scattering shows that such emission becomes possible only when the x rays have sufficiently high energy to lift the bound 3p electrons into the conduction band. With the tuning capabilities of synchrotron sources, this should open a new channel in autoionization experiments.

Brener, R.; Felsteiner, J.; Tyk, R.; Zak, J.

1988-01-15

199

Design of a novel transmission-grating spectrometer for soft X-ray emission studies  

Microsoft Academic Search

The design of a transmission-grating spectrometer for high-resolution soft X-ray emission studies has been proposed. It is different from conventional types of soft X-ray emission spectrometers; that is, the spectrometer has a Wolter type I mirror, a free-standing transmission grating, and a back-illuminated CCD. A high collection angle up to 1.5×10?3sr is achieved by utilizing the Wolter mirror as a

Takaki Hatsui; Hiroyuki Setoyama; Eiji Shigemasa; Nobuhiro Kosugi

2005-01-01

200

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

201

X-ray absorption and emission spectroscopic investigation of Mn doped ZnO films  

Microsoft Academic Search

The electronic structure of (Zn,Mn)O films with different Mn concentrations has been investigated by element-selective soft X-ray absorption and emission spectroscopy. The band gap narrowing of (Zn,Mn)O with increase of Mn concentration (<20% Mn) is attributed to the Mn doping and sp–d exchange interactions. According to analysis of the O K? and resonant Mn L2,3 X-ray emission spectra, the splitting

J. Jin; G. S. Chang; Y. X. Zhou; X. Y. Zhang; D. W. Boukhvalov; E. Z. Kurmaev; A. Moewes

2011-01-01

202

Modeling The Multiwavelength Correlation Of Blazar Emission: X-ray Hard-lags And X-ray/gamma-ray Correlation.  

NASA Astrophysics Data System (ADS)

We investigate with time-dependent multi-zone simulations two features features of TeV blazars multiwavelength variability that are of particular theoretical interests: X-ray hard lags and gamma-ray/X-ray quadratic relationship. We use a Monte Carlo/ Fokker-Planck radiative transfer code which enables us to take on the challenge of fully accounting the light crossing time effects, properly modeling them for what concerns both their effect on the observations and on the radiative processes within the source. We studied a class of scenarios in which the outburst is caused by a shock crossing the emission region. We will illustrate some factors that contribute to making these features difficult to reproduce. Our simulations show what kind of combination of stochastic particle acceleration, shock injection, and achromatic energy loss (e.g. particle escape) can reproduce the observed features in a shock-in-jet model framework. Both hard-lag and soft lag will be explained in the same model. The implication and justification of these particle processes will also be discussed. This research has been supported by NASA grants NNX10AO42G (Fermi GI). We acknowledge support from Smithsonian AO AR9-0016X (Chandra GO). This work is done in collaboration with E. Liang and M. Boettcher.

Chen, Xuhui; Fossati, G.

2011-09-01

203

A unified model of accretion flows and X ray emission in low mass X ray binary systems  

NASA Technical Reports Server (NTRS)

Recent work on a unified model of accretion flows and X-ray emission in low mass X-ray binaries is summarized. In this model, a weakly magnetic neutron star accretes gas simultaneously from a Keplerian disk and a corona above the inner part of the disk. Photons are produced and escape through an approximately radial inflow of gas captured from the inner disk corona. Changes in the optical depths of the central corona and the radial flow may explain the Z-shaped hardness-intensity and color-color tracks observed in the most luminous sources. Numerical simulations show that the radial flow oscillates when the luminosity rises to within a few percent of the Eddington critical luminosity L sub E, and that the oscillation frequency is approximately 5 to 10 Hz if the radial flow develops approximately 300 km from the neutron star. The 10 to 20 Hz oscillations observed in Sco X-1 when it is on the flaring branch are discussed.

Lamb, F. K.

1989-01-01

204

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

NASA Astrophysics Data System (ADS)

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

Massaro, F.; Grindlay, J. E.

2011-08-01

205

Recurrent X-ray Emission Variations of Eta Carinae and the Binary Hypothesis  

NASA Technical Reports Server (NTRS)

Recent studies suggest that, the super-massive star eta Carinae may have a massive stellar companion (Damineli, Conti, and Lopes 1997), although the dense ejecta surrounding the star make this claim hard to test using conventional methods. Settling this question is critical for determining the current evolutionary state and future evolution of the star. We address this problem by an unconventional method: If eta Carinae is a binary, X-ray emission should be produced in shock waves generated by wind-wind collisions in the region between eta Carinae and its companion. Detailed X-ray monitoring of eta Carinae for more that) 2 years shows that the observed emission generally resembles colliding-wind X-ray emission, but with some significant discrepancies. Furthermore, periodic X-ray "flaring" may provide an additional clue to determine the presence of a companion star and for atmospheric pulsation in eta Carinae.

Ishibashi, K.; Corcoran, M. F.; Davidson, K.; Swank, J. H.; Petre, R.; Drake, S. A.; Damineki, A.; White, S.

1998-01-01

206

Waiting in the Wings: Reflected X-ray Emission from the Homunculus Nebula  

NASA Technical Reports Server (NTRS)

We report the first detection of X-ray emission associated with the Homunculus Nebula which surrounds the supermassive star eta Carinae. The emission is characterized by a temperature in excess of 100 MK, and is consistent with scattering of the time-delayed X-ray flux associated with the star. The nebular emission is bright in the northwestern lobe and near the central regions of the Homunculus, and fainter in the southeastern lobe. We also report the detection of an unusually broad Fe K fluorescent line, which may indicate fluorescent scattering off the wind of a companion star or some other high velocity outflow. The X-ray Homunculus is the nearest member of the small class of Galactic X-ray reflection nebulae, and the only one in which both the emitting and reflecting sources are distinguishable.

Corcoran, M. F.; Hamaguchi, K.; Gull, T.; Davidson, K.; Petre, R.; Hillier, D. J.; Smith, N.; Damineli, A.; Morse, J. A.; Walborn, N. R.

2004-01-01

207

A Survey of X-ray Emission from Wolf-Rayet Stars  

NASA Astrophysics Data System (ADS)

It is well-known that massive WR + OB binaries are bright X-ray sources with typical luminosities log Lx 33 ergs/s. Some of their high-temperature X-ray emission likely originates in colliding wind shocks between the binary components, but intrinsic emission from the stars themselves may also contribute. However, much less is known about the X-ray emission of single WR stars. We present results of a pilot X-ray survey of single WR stars with Chandra and XMM-Newton aimed at defining their X-ray properties. None of our targets is so far known to be a binary system. We have detected X-rays from nitrogen-rich WN stars spanning all subtypes (WN2 - WN9). Typical luminosities are log Lx = 32.5 (+-1.0) ergs/s and their spectra invariably show high-temperature plasma (kT > 2 keV). Such hot plasma is not predicted by radiative wind shock models, implying that other as yet unidentified X-ray production mechanisms are at work. We also report a recent Chandra detection of the rare oxygen-type WO star WR 142 in the young stellar cluster Berkeley 87. Its ACIS spectrum is faint and very hard and can be fitted by either a nonthermal (power-law) model or an ultra-hot thermal plasma. Carbon-rich WC stars have so far not been detected in X-rays, but the observed sample is small. Their dense metal-enriched winds likely act as strong absorbers of any X-ray emission produced near the star.

Skinner, Steve L.

2010-02-01

208

Catalytic action of {beta} source on x-ray emission from plasma focus  

SciTech Connect

The influence of preionization around the insulator sleeve by a mesh-type {beta} source ({sub 28}Ni{sup 63}) for the x-ray emission from a (2.3-3.9 kJ) plasma focus device is investigated. Quantrad Si p-i-n diodes along with suitable filters are employed as time-resolved x-ray detectors and a multipinhole camera with absorption filters is used for time-integrated analysis. X-ray emission in 4{pi} geometry is measured as a function of argon and hydrogen gas filling pressures with and without {beta} source at different charging voltages. It is found that the pressure range for the x-ray emission is broadened, x-ray emission is enhanced, and shot to shot reproducibility is improved with the {beta} source. With argon, the Cu K{alpha} emission is estimated to be 27.14 J with an efficiency of 0.7% for {beta} source and 21.5 J with an efficiency of 0.55% without {beta} source. The maximum x-ray yield in 4{pi} geometry is found to be about 68.90 J with an efficiency of 1.8% for {beta} source and 54.58 J with an efficiency of 1.4% without {beta} source. With hydrogen, Cu K{alpha} emission is 11.82 J with an efficiency of 0.32% for {beta} source and 10.07 J with an efficiency of 0.27% without {beta} source. The maximum x-ray yield in 4{pi} geometry is found to be 30.20 J with an efficiency of 0.77% for {beta} source and 25.58 J with an efficiency of 0.6% without {beta} source. The x-ray emission with Pb insert at the anode tip without {beta} source is also investigated and found to be reproducible and significantly high. The maximum x-ray yield is estimated to be 46.6 J in 4{pi} geometry with an efficiency of 1.4% at 23 kV charging voltage. However, degradation of x-ray yield is observed when charging voltage exceeds 23 kV for Pb insert. From pinhole images it is observed that the x-ray emission due to the bombardment of electrons at the anode tip is dominant in both with and without {beta} source.

Ahmad, S.; Sadiq, Mehboob; Hussain, S.; Shafiq, M.; Zakaullah, M.; Waheed, A. [Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Department of Physics, University of Sargodha, Sargodha (Pakistan); Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan); PINSTECH, P.O. Box 1331, 44000 Islamabad (Pakistan)

2006-01-15

209

Catalytic action of ? source on x-ray emission from plasma focus  

NASA Astrophysics Data System (ADS)

The influence of preionization around the insulator sleeve by a mesh-type ? source (28Ni63) for the x-ray emission from a (2.3-3.9 kJ) plasma focus device is investigated. Quantrad Si p-i-n diodes along with suitable filters are employed as time-resolved x-ray detectors and a multipinhole camera with absorption filters is used for time-integrated analysis. X-ray emission in 4? geometry is measured as a function of argon and hydrogen gas filling pressures with and without ? source at different charging voltages. It is found that the pressure range for the x-ray emission is broadened, x-ray emission is enhanced, and shot to shot reproducibility is improved with the ? source. With argon, the Cu K? emission is estimated to be 27.14 J with an efficiency of 0.7% for ? source and 21.5 J with an efficiency of 0.55% without ? source. The maximum x-ray yield in 4? geometry is found to be about 68.90 J with an efficiency of 1.8% for ? source and 54.58 J with an efficiency of 1.4% without ? source. With hydrogen, Cu K? emission is 11.82 J with an efficiency of 0.32% for ? source and 10.07 J with an efficiency of 0.27% without ? source. The maximum x-ray yield in 4? geometry is found to be 30.20 J with an efficiency of 0.77% for ? source and 25.58 J with an efficiency of 0.6% without ? source. The x-ray emission with Pb insert at the anode tip without ? source is also investigated and found to be reproducible and significantly high. The maximum x-ray yield is estimated to be 46.6 J in 4? geometry with an efficiency of 1.4% at 23 kV charging voltage. However, degradation of x-ray yield is observed when charging voltage exceeds 23 kV for Pb insert. From pinhole images it is observed that the x-ray emission due to the bombardment of electrons at the anode tip is dominant in both with and without ? source.

Ahmad, S.; Sadiq, Mehboob; Hussain, S.; Shafiq, M.; Zakaullah, M.; Waheed, A.

2006-01-01

210

A Study of the X-Ray Emission from Three Radio Pulsars  

NASA Technical Reports Server (NTRS)

The subject grant is for work on a study of x-ray emission from isolated pulsars. The purpose of the study was to: determine whether the pulsars were x-ray sources; and, if so, search for evidence of pulsations at the known radio period; and study the nature of the x-ray emission. Observation of the pulsar PSR 0355+54 were obtained, and the analysis of these data is complete. These results were reported at the 183rd AAS Meeting, and in a paper entitled 'X-Ray Emission from PSR 0355+54' which as published in the The Astrophysical Journal. Also obtained an approx. 3 ks PSPC observations of PSR 1642-03. A summary of the results from these data were reported in a Conference Proceedings for the 'New Horizon of X-ray Astronomy' symposium. In addition, as part of a study with a student from the SAO Summer Intern Program, I incorporated ROSAT archival data in an extended study of pulsar emission. These results were reported at the 185th AAS Meeting, and in a paper entitled 'Soft X-ray Emission from Selected Isolated Pulsars' which was published in The Astrophysical Journal (Letters).

Slane, Patrick O. (Principal Investigator)

1996-01-01

211

Superluminal radio sources - What does X-ray emission tell us?  

NASA Technical Reports Server (NTRS)

In a study on superluminal radio sources, statistical relationships between X-ray, optical, and radio luminosities among different categories of active galactic nuclei are compared to search for common energy mechanisms. The X-ray versus optical and X-ray versus radio correlations of radio-loud QSOs and superluminal radio sources are found to be similar, arguing against a model in which the emission in only one or two of the three wave bands is relativistically boosted. A regression analysis shows that highly polarized QSOs and optically violently variable QSOs are more similar to other flat-spectrum, radio-loud QSOs than to BL Lac objects, and it is reasonable to assume that self-Compton emission dominates the X-ray emission from at least half of the sources in this class. The X-ray versus radio correlation for BL Lac objects is poor, and there is support for the hypothesis that their X-ray emission is dominated by an isotropic component which is not directly related to relativistically boosted radio emission.

Worrall, Diana M.

1987-01-01

212

Experimental studies of X-pinch dynamics and X-ray emission point parameters.  

NASA Astrophysics Data System (ADS)

New x-ray and spectroscopic diagnostics on the XP Pulser at Cornell (450 kA, 100 ns) have allowed quantitative measurements important for understanding the behavior of X-pinches. X-pinches produce intense x-ray radiation bursts from spots close to 1 ?m in diameter lasting about 0.5 ns. Using two parallel X-pinches, the radiation burst from each X-pinch was used to generate a magnified X-ray backlighter image of the other [1]. These images allow previously unobserved structure close to the time of x-ray burst emission to be seen. An intial stage is revealed in which a 300 ?m length z-pinch forms between the virtual electrodes of a "mini-diode" located at the crossing-point of the X-pinch. This z-pinch collapses rapidly into a series of narrow necks until an x-ray burst occurs from a spot inside the narrowest neck. After the x-ray burst, the z-pinch disappears quickly leaving only the mini-diode visible. Using a simple technique involving a reference mesh superimposed on the x-ray images, the x-ray emission point is located to within 10 ?m. Calibrated density measurements of Al x-pinches have been made using an Al step wedge in the film pack. K-spectra of H- and He-like Al, Ti, and Ni, as well as Ne-like Mo ions have been registered using FSSR spectrography with spherically bent mica crystals. These spectra yield estimates of Ne > 10^21 cm-3 and Te > 1 keV for the x-ray emission point. 1. T.A.Shelkovenko, S.A.Pikuz, A.R.Mingaleev and D.A.Hammer, Rev. Sci. Instrum., 70, 667 (1999).

Shelkovenko, T. A.; Pikuz, S. A.; Sinars, D. B.; Skobelev, I. Yu.; Hammer, D. A.; Greenly, J. B.; Dimant, Y. S.

1999-11-01

213

Chandra Observations and Modeling of Geocoronal Charge Exchange X-Ray Emission During Solar Wind Gusts  

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 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 tens of 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 have studied a dozen Chandra observations when the flux of solar wind protons and O7+ ions was at its highest. These gusts of wind cause correspondingly abrupt changes in geocoronal SWCX X-ray emission,which may or may not be apparent in Chandra data depending on a given observation's line of sight through the magnetosphere. We compare observed changes in the X-ray background with predictions from a fully 3D analysis of SWCX emission based on magnetospheric simulations using the BATS-R-US model.

Kornbleuth, Marc; Wargelin, Bradford J.; Juda, Michael

2014-06-01

214

Relative L-shell X-ray emission rates in PIXE  

NASA Astrophysics Data System (ADS)

L shell X-ray emission rates usually used as a part of a data base for analysis of PIXE spectra are theoretical values based on Dirac-Hartree-Slater (DHS) [J.H. Scofield, At. Data Nucl. Data Tables 14 (1974) 121] or Dirac-Hartree-Fock (DHF) [J.H. Scofield, Phys. Rev. A 10 (1974) 1507] calculations, or semiempirical data of Salem et al. [At. Data Nucl. Data Tables 14 (1974) 91], obtained from pre-1974 experiments with radioactive sources or sources ionized by photon or electron bombardment. Recently published L-subshell X-ray production cross sections by proton impact have been used to extract relative L-shell X-ray emission rates for some groups of L-shell X-ray lines, in order to compare them with the values from the three data bases mentioned before.

Fazini?, S.

1996-04-01

215

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

SciTech Connect

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 (5x10) 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 [Department of Radiation Oncology, University of North Carolina at Chapel Hill, North Carolina 27599 (United States); Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina 27599 (United States); Calderon, Xiomara; Peng Rui [Curriculum of Applied and Materials Sciences, University of North Carolina at Chapel Hill, North Carolina 27599 (United States); Schreiber, Eric C. [Department of Radiation Oncology, University of North Carolina at Chapel Hill, North Carolina 27599 (United States); Zhou, Otto [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina 27599 (United States); Curriculum of Applied and Materials Sciences, University of North Carolina at Chapel Hill, North Carolina 27599 (United States); Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina 27599 (United States); Chang, Sha [Department of Radiation Oncology, University of North Carolina at Chapel Hill, North Carolina 27599 (United States); Department of Physics and Astronomy, University of North Carolina at Chapel Hill, North Carolina 27599 (United States); Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina 27599 (United States)

2011-05-23

216

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

217

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

218

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

NASA Astrophysics Data System (ADS)

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

2011-05-01

219

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

220

Can Charge Exchange Explain Anomalous Soft X-Ray Emission in the Cygnus Loop?  

NASA Astrophysics Data System (ADS)

Recent X-ray studies have shown that supernova shock models are unable to satisfactorily explain X-ray emission in the rim of the Cygnus Loop. In an attempt to account for this "anomalously" enhanced X-ray flux, we fit the region with a model including theoretical charge exchange (CX) data along with shock and background X-ray models. The model includes the CX collisions of O8 +, O7 +, N7 +, N6 +, C6 +, and C5 + with H with an energy of 1 keV u-1 (438 km s-1). The observations reveal a strong emission feature near 0.7 keV that cannot fully be accounted for by a shock model, nor the current CX data. Inclusion of CX, specifically O7 + + H, does provide for a statistically significant improvement over a pure shock model.

Cumbee, R. S.; Henley, D. B.; Stancil, P. C.; Shelton, R. L.; Nolte, J. L.; Wu, Y.; Schultz, D. R.

2014-06-01

221

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

222

The Morphology of the X-ray Emission above 2 keV from Jupiter's Aurorae  

NASA Technical Reports Server (NTRS)

The discovery in XMM-Newton X-ray data of X-ray emission above 2 keY from Jupiter's aurorae has led us to reexamine the Chandra ACIS-S observations taken in Feb 2003. Chandra's superior spatial resolution has revealed that the auroral X-rays with E > 2 keV are emitted from the periphery of the region emitting those with E < 1 keV. We are presently exploring the relationship of this morphology to that of the FUV emission from the main auroral oval and the polar cap. The low energy emission has previously been established as due to charge exchange between energetic precipitating ions of oxygen and either sulfur or carbon. It seems likely to us that the higher energy emission is due to precipitation of energetic electrons, possibly the same population of electrons responsible for the FUV emission. We discuss our analysis and interpretation.

Elsner, R.; Branduardi-Raymont, G.; Galand, M.; Grodent, D.; Gladstone, G. R.; Waite, J. H.; Cravens, T.; Ford, P.

2007-01-01

223

The Morphology of the X-ray Emission above 2 keV from Jupiter's Aurorae  

NASA Technical Reports Server (NTRS)

The discovery in XMM-Newton X-ray data of X-ray emission above 2 keV from Jupiter's aurorae has led us to reexamine the Chandra ACIS-S observations taken in Feb 2003. Chandra's superior spatial resolution has revealed that the auroral X-rays with E > 2 keV are emitted from the periphery of the region emitting those with E < 1 keV. We are presently exploring the relationship of this morphology to that of the FUV emission from the main auroral oval and the polar cap. The low energy emission has previously been established as due to charge exchange between energetic precipitating ions of oxygen and either sulfur or carbon. It seems likely to us that the higher energy emission is due to precipitation of energetic electrons, possibly the same population of electrons responsible for the FUV emission. We discuss our analysis and interpretation.

Elsner, R.; Branduardi-Raymont, G.; Galand, M.; Grodent, D.; Waite, J. H.; Cravens, T.; Ford, P.

2007-01-01

224

Weak Hard X-ray Emission from Broad Absorption Line Quasars Observed with NuSTAR: Evidence for Intrinsic X-ray Weakness  

NASA Astrophysics Data System (ADS)

We report NuSTAR observations of a sample of six X-ray weak broad absorption line (BAL) quasars. These targets, at z=0.148-1.223, are among the optically brightest and most luminous BAL quasars known at z<1.3. However, their rest-frame 2 keV luminosities are 14 to >330 times weaker than expected for typical quasars. Our results from a pilot NuSTAR study of two low-redshift BAL quasars, a Chandra stacking analysis of a sample of high-redshift BAL quasars, and a NuSTAR spectral analysis of the local BAL quasar Mrk 231 have already suggested the existence of intrinsically X-ray weak BAL quasars, i.e., quasars not emitting X-rays at the level expected from their optical/UV emission. The aim of the current program is to extend the search for such extraordinary objects. Three of the six new targets are weakly detected by NuSTAR with <45 counts in the 3-24 keV band, and the other three are not detected. The hard X-ray (8-24 keV) weakness observed by NuSTAR requires Compton-thick absorption if these objects have nominal underlying X-ray emission. However, a soft stacked effective photon index (Γ 1.8) for this sample disfavors Compton-thick absorption in general. The uniform hard X-ray weakness observed by NuSTAR for this and the pilot samples selected with <10 keV weakness also suggests that the X-ray weakness is intrinsic in at least some of the targets. We conclude that the NuSTAR observations have likely discovered a significant population (>33%) of intrinsically X-ray weak objects among the BAL quasars with significantly weak <10 keV emission. We suggest that intrinsically X-ray weak quasars might be preferentially observed as BAL quasars.

Luo, Bin; Brandt, W. Niel; Alexander, David M; Stern, Daniel; Teng, Stacy H.; Arevalo, Patricia; Bauer, Franz E.; Boggs, Steven E.; Christensen, Finn; Comastri, Andrea; Craig, William W.; Farrah, Duncan; Gandhi, Poshak; Hailey, Charles James; Harrison, Fiona; Koss, Michael; Ogle, Patrick M.; Puccetti, Simonetta; Saez, Cristian; Scott, Amy; Walton, Dom; Zhang, William

2014-08-01

225

Relativistic component of chemical shift of Uranium X-ray emission lines  

Microsoft Academic Search

Twelve most intensive hard X-ray emission lines belonging to two multiplets (2p-3d and 2p-4d) and three doublets (2s-3p, 2s-4p, and 2p-3s) of the uranium L-series were studied by using a precise crystal-diffraction X-ray spectrometer. Chemical shift (CS) values were obtained for the first time for uranium (VI) oxide and uranium fluoride with respect to uranium (IV) oxide. The first attempt

Yuri F Batrakov; Andrey G Krivitsky; Elena V Puchkova

2004-01-01

226

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

227

The Sun's X-ray Emission During the Recent Solar Minimum  

Microsoft Academic Search

The Sun recently underwent a period of a remarkable lack of major activity such as large flares and sunspots, without equal since the advent of the space age a half century ago. A widely used measure of solar activity is the amount of solar soft X-ray emission, but until recently this has been below the threshold of the X-ray-monitoring Geostationary

Janusz Sylwester; Mirek Kowalinski; Szymon Gburek; Marek Siarkowski; Sergey Kuzin; Frantisek Farnik; Fabio Reale; Kenneth J. H. Phillips

2010-01-01

228

Effects of multiple ionization on total L X-ray emission by proton impact  

NASA Astrophysics Data System (ADS)

The effects of multiple ionization on L X-ray emission by proton with energy from 100 keV to 250 keV on iron target was studied. The total L X-ray production cross sections were measured. A multiple ioniza-tion model and an average fluorescence yield were used together. The theoretical predictions with the correction of atomic parameter were obtained.

Wang, Xing; Zhao, Yongtao; Zhou, Xianming; Cheng, Rui; Lei, Yu; Sun, Yuanbo; Xiao, Guoqing

2014-04-01

229

A model of hard X-rays emission from free expanding Plasma-Focus discharges  

NASA Astrophysics Data System (ADS)

A planar-piston model of the hard x-ray production in Plasma-Focus devices is presented. The model applies Von Karman approximations to represent the inner structure of the pinch. The hard x-ray emission is calculated assuming Bremsstrahlung from the collision on the anode base of an electron current running away from the pinch. The model was applied to analyse the experimental data of a small Plasma Focus without surrounding cathode, founding good agreement.

Fogliatto, E.; González, J.; Barbaglia, M.; Clausse, A.

2014-05-01

230

Characterization of titanium nitride layers by grazing-emission X-ray fluorescence spectrometry  

Microsoft Academic Search

Grazing-emission X-ray fluorescence spectrometry is a new development in X-ray metrology instrumentation. The combination of wavelength-dispersive detection with a total-reflection geometry in the detection path allows thin layer characterization also for light elements. The technique was applied to analyze a series of titanium nitride layers, reactively sputtered using different ArN2 flow ratios of the working gas. Composition, thickness and density

G. Wiener; S. J. Kidd; C. A. H. Mutsaers; R. A. M. Wolters; P. K. de Bokx

1998-01-01

231

Thermal X-Ray Emission and Cosmic-Ray Production in Young Supernova Remnants  

Microsoft Academic Search

We have developed a simple model to investigate the modifications of the hydrodynamics and nonequilibrium ionization X-ray emission in young supernova remnants due to nonlinear particle acceleration. In nonlinear, diffusive shock acceleration, the heating of the gas to X-ray-emitting temperatures is strongly coupled to the acceleration of cosmic-ray ions. If the acceleration is efficient and a significant fraction of the

Anne Decourchelle; Donald C. Ellison; Jean Ballet

2000-01-01

232

Extended hard X-ray emission from Vela X  

NASA Astrophysics Data System (ADS)

Vela X powered by the Vela pulsar is the best example of an evolved pulsar wind nebula, allowing to access the particle injection history and the interaction with the supernova ejecta. We present the spectrum of Vela X in the 20-300 keV energy range as measured by IBIS/ISGRI and SPI, the main instruments onboard the INTEGRAL satellite. The apparent discrepancy between IBIS/ISGRI, SPI, and previousmeasurements is understood in terms of point spread function, pointing out a nebula more diffuse than previously thought. The presence of cooled electrons is also revealed by the spectral break measured including Suzaku data in the 1-10 keV range. This picture is supported by the identification of a new structure in the 20-60 keV energy band extended along the NE/SW axis and partially coincident with the cocoon, the soft X-ray filament extending towards the centre of the remnant.

Mattana, Fabio; Terrier, Régis; Götz, Diego; Ponti, Gabriele; Bouchet, Laurent; Falanga, Maurizio; Renaud, Matthieu; Schanne, Stephane

233

XMM Observations of X-Ray Emission from Supernovae  

NASA Technical Reports Server (NTRS)

Of the six proposed targets, only one observation was performed. The observation resulted in a 28ks observation of SN 1998S. At the time of writing the proposal, our target list only contained previously unknown X-ray supernovae. Between submission of the proposal and the actual observation, a Chandra DDT observation resulted in the detection of SN 1998S. Since SN 1998S was observed with Chandra five times before the XMM-Newton observation was made, the data did not yield enough new information to warrant a separate SN 1998S publication. The key science results of that observation were presented in a review article (by Immler and Lewin); the results were also presented at two conferences.

Immler, Stefan; Lewin, Walter

2003-01-01

234

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

235

X-Ray Emission from a Simulated Cluster of Galaxies  

NASA Technical Reports Server (NTRS)

Using the 1993 cluster simulation of Katz & White, we analyze the intracluster medium and investigate the accuracy of the standard hydrostatic method for determining cluster masses. We show that the simulated cluster gas is in hydrostatic equilibrium with a subsonic flow toward the center. Inside a radius of (approx.) 100 kpc, this flow is in a steady state. The cooling time is shorter than a Hubble time within the central 50 kpc. The flow rate is regulated by the gas sink in the middle of the cluster and the PdV work done as the gas flows in, verifying the standard cooling flow scenario. We simulate observations of the cluster using the instrument parameters of the EXOSAT ME detector and the Einstein IPC detector. Even though the intracluster gas is not isothermal, isothermal models of the cluster, excluding regions within 100 kpc of galaxies, fit the EXOSAT X-ray spectra as well as they fit real clusters. The X- ray surface brightness distribution is similar to that of real clusters, again excluding the galaxies. We simulate the procedure used to determine the masses of real clusters. We use the equation of hydrostatic equilibrium together with the temperature derived from an isothermal fit to the simulated EXOSAT spectrum and the density profile derived from a fit to the simulated IPC surface brightness profile to determine the mass. A comparison of the derived mass profile to the actual mass profile shows that errors of a factor of 2 are possible. If the actual temperature profile is used, the cluster mass is found to an accuracy of better than 25% within the virial radius.

Tsai, John C.; Katz, Neal; Bertschinger, Edmund

1994-01-01

236

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

237

Discovery of Diffuse Hard X-ray Emission in the Galactic Center  

NASA Astrophysics Data System (ADS)

The inner arcminutes of the Galaxy contain one of the highest concentration of high-energy sources in the Milky Way. The supermassive black hole, pulsar wind nebulae, supernova remnants, X-ray binaries, and hot interstellar gas are copious emitters of X-rays and gamma-rays. NuSTAR provides a view of the hard X-ray (3-79 keV) band, a critical bridge between the soft X-ray and gamma-ray emission, with unprecedented sub-arcminute angular resolution. I will present analysis of NuSTAR’s view of the Galactic Center above 20 keV, which reveals entirely new contributions to the emission from this region. The hard X-ray emission from the Galactic Center is dominated by a strong point-like source, spatially consistent with the ultra-high energy gamma-ray emission detected by HESS, and a previously undetected diffuse emission extending along the Galactic plane, consistent with unresolved emission from a large population of millisecond pulsars, unusually hot intermediate polars, or black hole binaries.

Perez, Kerstin

2014-08-01

238

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

239

Hard X-Ray Emission and the Ionizing Source in LINERs  

NASA Technical Reports Server (NTRS)

We report X-ray luminosities of 21 LINERs (low-ionization nuclear emission-line regions) and 17 low-luminosity Seyferts obtained with ASCA and discuss the ionizing source in LINERs. Most LINERs with broad H-alpha emission in their optical spectra (LINER 1s) have a compact hard X-ray source and their 2-10 keV X-ray luminosities (LX) are proportional to their H alpha luminosities (L-H-alpha). This correlation strongly supports the hypothesis that the dominant ionizing source in LINER 1s is photoionization by hard photons from low-luminosity AGNs. Although some LINERs without broad H-alpha emission (LINER 2s) have X-ray properties similar to LINER 1s, the X-ray luminosities of many LINER 2s in our sample are lower than LINER 1s at a given H-alpha luminosity. The observed X-ray luminosities in these objects are insufficient to power their H-alpha luminosities, suggesting that their primary ionizing source is something other than an AGN, or that an AGN, if present, is obscured even at energies above 2 keV. LINER 2s having small LX/LH-alpha occupy a localized region with small [OI]/H-alpha on the excitation diagram. Such LINER spectra can be reproduced by photoionization by very hot stars.

Terashima, Y.; Ho, L. C.; Ptak, A. F.

2004-01-01

240

Measurements of x-ray emission from rocket-triggered lightning  

NASA Astrophysics Data System (ADS)

We report measurements of the x-ray emission from rocket-triggered lightning, made during the summer of 2003, using four instruments placed between 15 and 40 m from the lightning channels. X-rays were measured 0-80 ?s just prior to and at the beginning of 73% of the 26 return strokes observed. The emission was composed of multiple, very brief bursts of x-rays in the 30-250 keV range, with each burst typically lasting less than 1 ?s. The x-rays were primarily observed to be spatially and temporally associated with the dart leaders with a possible contribution from the beginning of the return strokes, with the most intense x-ray bursts coming from the part of the lightning channel within ~50 m of the ground. Because triggered lightning strokes are similar to subsequent strokes in natural lightning, it is likely that x-ray emission is a common property of natural lightning.

Dwyer, J. R.; Rassoul, H. K.; Al-Dayeh, M.; Caraway, L.; Wright, B.; Chrest, A.; Uman, M. A.; Rakov, V. A.; Rambo, K. J.; Jordan, D. M.; Jerauld, J.; Smyth, C.

2004-03-01

241

Hard X-ray component in Sco X-1 spectrum: Synchrotron emission from a nano quasar  

NASA Astrophysics Data System (ADS)

Sco X-1 is a low mass X-ray binary system and with the recent observations of a resolved radio jet, the source has been included in the list of galactic microquasars. The observed spectral data in the 2-20 keV energy band fits a thermal emission. Above 20 keV, a hard tail has been reported on occasions. During our continuing balloon borne X-ray survey in the 20-200 keV region using high sensitivity Large Area Scintillation counter Experiment, Sco X-1 was observed on two different occasions. Even though the total X-ray luminosity of the source was different, the spectral nature of the source did not show any variation. The presence of hard X-ray flux is unmistakable. We present the spectral and temporal data in the hard X-ray band and discuss the results in terms of geometrical characteristics of X-ray source and its observed temporal properties. We note that the jet activity is similar to the microquasars, however, the absence of the large magnitude abrupt changes in X-ray light curve compared to GRS1915 + 105 suggest that the quasar-like behaviour is at a nano scale.

Manchanda, R. K.

242

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

243

Prior Emission Model for X-ray Plateau Phase of Gamma-Ray Burst Afterglows  

NASA Astrophysics Data System (ADS)

The two-component emission model to explain the plateau phase of the X-ray afterglows of gamma-ray bursts (GRBs) is proposed. One component, which is responsible for the plateau and subsequent normal decay phase of the X-ray afterglow, is the prior emission via outflow ejected from the central engine before the main burst. The other is the main outflow, which causes the prompt GRB emission and the initial steep decay phase of the X-ray afterglow. In this model, the transition from the plateau to the subsequent normal decay phase is an artifact of the choice of the zero of time. For events with distinct plateau phase, the central engine is active 103-104 s before the launch of the main outflow. According to this model, a prior emission in the X-ray and/or optical bands 103-104 s before the prompt GRB emission is possibly seen, which will be tested by near-future instruments such as Monitor of All-sky X-ray Image (MAXI), WIDe-field telescope for GRB Early Timing (WIDGET), and so on.

Yamazaki, Ryo

2009-01-01

244

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

245

The soft X-ray spectrum of Capella - Discovery of intense line emission  

NASA Technical Reports Server (NTRS)

A soft X-ray spectrum of Capella has been obtained with the HEAO 1 satellite. Only models which include intense line emission at 0.85 keV can adequately explain the data. The spectrum is consistent with emission from an isothermal solar-abundance plasma with a temperature of 10.5 million (+ or - 2.8 million) K. It is also consistent with a blend of temperatures between 4 and 20 million K. The intensity of the X-ray emission is constant over 2 days and similar to the intensity observed by ANS.

Cash, W.; Bowyer, S.; Charles, P. A.; Lampton, M.; Garmire, G.; Riegler, G.

1978-01-01

246

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

247

On the nature of the X-ray emission from 1E 1024.0-5732/Wack 2134: The first X-ray-selected Wolf-Rayet star  

NASA Astrophysics Data System (ADS)

We report on a ROSAT Position-Sensitive Proportional Counter (PSPC) observation of the X-ray source 1E 1024.0-5732. The optical identification with the emission-line star Wackerling 2134 is confirmed, but we do not find any evidence of the periodic pulsations at 61 ms which were previously reported in its X-ray flux. On the basis of the new timing and spectral results, a reexamination of the old X-ray and optical data, and a new optical spectrum, we propose that this source is a new Wolf-Rayet star of type WN6. The high level of X-ray emission hints at the presence of a binary companion to Wack 2134. This could be either an accreting compact object or a massive OB star, in which case the X-rays would be produced in the colliding winds of the two stars. The small equivalent widths of the Wolf-Rayet star emission lines strongly support the O-star companion hypothesis. If this scenario is confirmed, Wack 2134 would be the first case of an X-ray-selected Wolf-Rayet star.

Mereghetti, Sandro; Belloni, Tomaso; Shara, Michael; Drissen, Laurent

1994-04-01

248

Depleted uranium (92U238) induced preionization for enhanced and reproducible x-ray emission from plasma focus  

NASA Astrophysics Data System (ADS)

The effect of preionization induced by depleted uranium (92U238) around the insulator sleeve on the x-ray emission of (2.3-3.9 kJ) plasma focus device is investigated by employing Quantrad Si p-i-n diodes and a multipinhole camera. X-ray emission in 4? geometry is measured as a function of charging voltage with and without preionization. It is found that the preionization enhances Cu K? and total x-ray yield about 100%, broadens the x-ray emission pressure range and x-ray pulse width, and improves shot to shot reproducibility of plasma focus operation. The pinhole images of x-ray emitting zones indicate that dominant x-ray emission is from the anode tip.

Ahmad, S.; Shafiq, M.; Zakaullah, M.; Waheed, A.

2006-08-01

249

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

250

Rotational modulation of X-ray emission in Orion Nebula young stars.  

NASA Astrophysics Data System (ADS)

We present the detection of rotational modulation of X-ray emission from the Orion Nebula Cluster (ONC) young stars. This result is obtained with the Chandra Orion Ultradeep Project (COUP) thanks to the exceptional length of the observation: 10 days of ACIS integration during a time span of 13 days. We apply the Lomb Periodogram method to the X-ray light curves; comparing the X-ray modulation periods with published rotation periods, we find that the two are statistically related. X-ray rotational modulation is often observed in stars with saturated activity levels, indicating a substantial inhomogeneity in the spatial distribution of active regions. Saturation is thus not due to the filling of the stellar surface with active regions.

Flaccomio, E.; Micela, G.; Sciortino, S.; Feigelson, E. D.; Herbst, W.; Favata, F.; Harnden, F. R., Jr.; Vrtilek, S. D.

251

Numerical Simulations of a Prompt Hard X-ray Emission During its Bright Outburst  

NASA Astrophysics Data System (ADS)

We present a simple numerical model of the X-ray emission of the system XTE J0421+560/CI Cam during its bright outburst on 31 March 1998. Basing on the spectral and timing behavior of the object we argue that this outburst is a prompt X-ray/hard X-ray emission of a classical nova-type explosion (thermonuclear runaway on the surface of the white dwarf) unlike many other outbursts of X-ray binary systems. The thermonuclear runaway on the surface of the white dwarf leads to the formation of fast ejecta which moves through the dense stellar wind of the optical companion (B giant). Shock waves, which are formed in the material of the wind and that of the ejecta heats the matter up to X-ray temperatures. We use the spherically symmetric Lagrangian hydro- simulation to follow the evolution of the explosion. Up to now we have extensively simulated early phases of the outburst and showed that using of physically motivated simulations one can put constrains on the velocity of the ejecta and the stellar companion mass loss rate. In order to follow X-ray evolution throughout the whole outburst we develop a fully adaptive code.

Filippova, Ekaterina V.; Revnivtsev, M.; Lutovinov, A.

2007-08-01

252

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

253

A deep search for radio emission from three X-ray pulsars : are radio emission and X-ray pulsations anticorrelated ?  

Microsoft Academic Search

We present results from a deep search for radio emission from the X-ray\\u000apulsar systems GX 1+4, GS 0834-430 and 4U 0115+63 which have variously been\\u000asuggested to possess radio jets and to be good candidates for propellor\\u000aejection mechanisms. None of these sources is detected at their optical\\u000apositions, to 3 sigma limits of a few hundred micro-Jy. This

R. P. Fender; P. Roche; G. G. Pooley; D. Chakrabarty; A. K. Tzioumis; M. A. Hendry; R. E. Spencer

1996-01-01

254

A Deep Search for Radio Emission from three X-Ray Pulsars: Are Radio Emission and X-Ray Pulsations Anti-Correlated?  

Microsoft Academic Search

We present results from a deep search for radio emission from the X-ray pulsar systems GX 1+4, GS 0834-430 and 4U 0115+63 which have variously been suggested to possess radio jets and to be good candidates for propellor ejection mechanisms. None of these sources is detected at their optical positions, to 3 sigma limits of a few hundred micro-Jy. This

R. P. Fender; P. Roche; G. G. Pooley; D. Chackrabarty; A. K. Tzioumis; M. A. Hendry; R. E. Spencer

1997-01-01

255

Early magnetic B-type stars: X-ray emission and wind properties  

NASA Astrophysics Data System (ADS)

We present a comprehensive study of X-ray emission by, and wind properties of, massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three early-type B-type stars, ?1 CMa, V2052 Oph and ? Cas, with recently discovered magnetic fields. We report the first detection of X-ray emission from V2052 Oph and ? Cas. The latter is one the softest X-ray sources among the early-type stars, while the former is one of the X-ray faintest. The observations show that the X-ray spectra of our programme stars are quite soft with the bulk of X-ray emitting material having a temperature of about 1 MK. We compile the complete sample of early B-type stars with detected magnetic fields to date and existing X-ray measurements, in order to study whether the X-ray emission can be used as a general proxy for stellar magnetism. We find that the X-ray properties of early massive B-type magnetic stars are diverse, and that hard and strong X-ray emission does not necessarily correlate with the presence of a magnetic field, corroborating similar conclusions reached earlier for the classical chemically peculiar magnetic Bp-Ap stars. We analyse the ultraviolet (UV) spectra of five non-supergiant B stars with magnetic fields (? Sco, ? Cep, ?1 CMa, V2052 Oph and ? Cas) by means of non-local thermodynamic equilibrium (non-LTE) iron-blanketed model atmospheres. The latter are calculated with the Potsdam Wolf-Rayet (PoWR) code, which treats the photosphere as well as the wind, and also accounts for X-rays. With the exception of ? Sco, this is the first analysis of these stars by means of stellar wind models. Our models accurately fit the stellar photospheric spectra in the optical and the UV. The parameters of X-ray emission, temperature and flux are included in the model in accordance with observations. We confirm the earlier findings that the filling factors of X-ray emitting material are very high. Our analysis reveals that the magnetic early-type B stars studied here have weak winds with velocities not significantly exceeding vesc. The mass-loss rates inferred from the analysis of UV lines are significantly lower than predicted by hydrodynamically consistent models. We find that, although the X-rays strongly affect the ionization structure of the wind, this effect is not sufficient in reducing the total radiative acceleration. When the X-rays are accounted for at the intensity and temperatures observed, there is still sufficient radiative acceleration to drive a stronger mass-loss than we empirically infer from the UV spectral lines.

Oskinova, L. M.; Todt, H.; Ignace, R.; Brown, J. C.; Cassinelli, J. P.; Hamann, W.-R.

2011-09-01

256

Time resolved studies on X-rays and charged particles emission from a low energy plasma focus device  

Microsoft Academic Search

The time resolved studies on soft X-ray, hard X-ray, electron beam and ion beam emissions from a low energy plasma focus device are carried out simultaneously by employing a photodiode X-ray spectrometer, a scintillator photomultiplier tube, a combination of Faraday cup and Rogowski coil assembly and a biased Faraday cup, respectively. The soft X-ray is seen to be emitted in

N. K. Neog; S. R. Mohanty; T. K. Borthakur

2008-01-01

257

Low- to Middle-Latitude X-Ray Emission from Jupiter  

NASA Technical Reports Server (NTRS)

The Chandra X-ray Observatory (CXO) observed Jupiter during the period 24-26 February 2003 for approx. 40 hours (4 Jupiter rotations), using both the spectroscopy array of the Advanced CCD Imaging Spectrometer (ACIS-S) and the imaging array of the High-Resolution Camera (HRC-I). Two ACIS-S exposures, each -8.5 hours long, were separated by an HRC-I exposure of approx. 20 hours. The low- to middle-latitude nonauroral disk X-ray emission is much more spatially uniform than the auroral emission. However, the low- to middle-latitude X-ray count rate shows a small but statistically significant hour angle dependence and depends on surface magnetic field strength. In addition, the X-ray spectra from regions corresponding to 3-5 gauss and 5-7 gauss surface fields show significant differences in the energy band 1.26-1.38 keV, perhaps partly due to line emission occurring in the 3-5 gauss region but not the 5-7 gauss region. A similar correlation of surface magnetic field strength with count rate is found for the 18 December 2000 HRC-I data, at a time when solar activity was high. The low- to middle-latitude disk X-ray count rate observed by the HRC-I in the February 2003 observation is about 50% of that observed in December 2000, roughly consistent with a decrease in the solar activity index (F10.7 cm flux) by a similar amount over the same time period. The low- to middle-latitude X-ray emission does not show any oscillations similar to the approx. 45 min oscillations sometimes seen from the northern auroral zone. The temporal variation in Jupiter's nonauroral X-ray emission exhibits similarities to variations in solar X-ray flux observed by GOES and TIMED/SEE. The two ACIS-S 0.3-2.0 keV low- to middle-latitude X-ray spectra are harder than the auroral spectrum and are different from each other at energies above 0.7 keV, showing variability in Jupiter's nonauroral X-ray emission on a timescale of a day. The 0.3-2.0 keV X-ray power emitted at low to middle latitudes is 0.21 GW and 0.39 GW for the first and second ACIS-S exposures, respectively. We suggest that X-ray emission from Jupiter's disk may be largely generated by the scattering and fluorescence of solar X rays in its upper atmosphere, especially at times of high incident solar X-ray flux. However, the dependence of count rate on surface magnetic-field strength may indicate the presence of some secondary component, possibly ion precipitation from radiation belts close to the planet.

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

2006-01-01

258

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

259

Measurement of the Radius of Neutron Stars with High Signal-to-noise Quiescent Low-mass X-Ray Binaries in Globular Clusters  

NASA Astrophysics Data System (ADS)

This paper presents the measurement of the neutron star (NS) radius using the thermal spectra from quiescent low-mass X-ray binaries (qLMXBs) inside globular clusters (GCs). Recent observations of NSs have presented evidence that cold ultra dense matter—present in the core of NSs—is best described by "normal matter" equations of state (EoSs). Such EoSs predict that the radii of NSs, R NS, are quasi-constant (within measurement errors, of ~10%) for astrophysically relevant masses (M NS>0.5 M ?). The present work adopts this theoretical prediction as an assumption, and uses it to constrain a single R NS value from five qLMXB targets with available high signal-to-noise X-ray spectroscopic data. Employing a Markov chain Monte-Carlo approach, we produce the marginalized posterior distribution for R NS, constrained to be the same value for all five NSs in the sample. An effort was made to include all quantifiable sources of uncertainty into the uncertainty of the quoted radius measurement. These include the uncertainties in the distances to the GCs, the uncertainties due to the Galactic absorption in the direction of the GCs, and the possibility of a hard power-law spectral component for count excesses at high photon energy, which are observed in some qLMXBs in the Galactic plane. Using conservative assumptions, we found that the radius, common to the five qLMXBs and constant for a wide range of masses, lies in the low range of possible NS radii, R_NS =9.1^{+ 1.3}_{- 1.5} \\,km (90%-confidence). Such a value is consistent with low-R NS equations of state. We compare this result with previous radius measurements of NSs from various analyses of different types of systems. In addition, we compare the spectral analyses of individual qLMXBs to previous works.

Guillot, Sebastien; Servillat, Mathieu; Webb, Natalie A.; Rutledge, Robert E.

2013-07-01

260

Search of X-ray emission from roAp stars: the case of ? Equulei  

NASA Astrophysics Data System (ADS)

Context. Rapidly oscillating Ap (roAp) stars represent a subclass of magnetic, chemically peculiar stars. The explanation for their pulsations includes suppressed convection due to the strong magnetic field. These stars rotate slowly such that a solar-like dynamo and ensuing magnetic activity is unlikely to be present. On the other hand, magnetic activity could provide the particle acceleration suspected to be responsible for the presence of short-lived radionuclides on some roAp stars. Aims: The detection of X-ray emission from Ap stars can be an indicator for the presence of magnetic activity and dynamo action, provided different origins for the emission, such as wind shocks and close late-type companions, can be excluded. Here we report on results for ? Equ, the only roAp star for which an X-ray detection is reported in ROSAT catalogs. Methods: We use high resolution imaging in X-rays with Chandra and in the near-infrared with NACO/VLT that allow us to spatially resolve companions down to ? 1'' and ~0.06'' separations, respectively. Results: The bulk of the X-ray emission is associated with a companion of ? Equ identified in our NACO image. Assuming coevality with the primary roAp star (~900 Myr), the available photometry for the companion points at a K-type star with ~0.6 M?. Its X-ray properties are in agreement with the predictions for its age and mass. An excess of photons with respect to the expected background and contribution from the nearby companion is observed near the optical position of ? Equ. We estimate an X-ray luminosity of log Lx [erg/s] = 26.6 and log (Lx/Lbol) = -7.9 for this emission. A small offset between the optical and the X-ray image leaves some doubt on its association with the roAp star. Conclusions: The faint X-ray emission that we tentatively ascribe to the roAp star is difficult to explain as a solar-like stellar corona due to its very low Lx/Lbol level and the very long rotation period of ? Equ. It could be produced in magnetically confined wind shocks implying a mass loss rate of ~10-14 M?/yr or from an additional unknown late-type companion at separation ? 0.4''. If confirmed by future deeper X-ray observations this emission could point at the origin for the presence of radioactive elements on some roAp stars.

Stelzer, B.; Hummel, C. A.; Schöller, M.; Hubrig, S.; Cowley, C.

2011-05-01

261

Inverse Compton X-ray emission from the superluminal quasar 3C 345  

NASA Technical Reports Server (NTRS)

In quasars with strong radio cores, the inverse-Compton process is believed to be the dominant source X-ray emission. For objects with parsec-scale radio jets, simple models have predicted that components in the jet emerging from the quasar nucleus generate the observed X-ray emission. We have tested this hypothesis in detail for the quasar 3C 345 using a ROSAT X-ray observation in 1990 July, together with quasi-simultaneous very long base interferometry (VLBI) imaging of the parsec-scale jet at five frequencies. The ROSAT spectrum is well fitted by a power law with index alpha = -0.96 +/- -0.13, consistent with models in which the X-ray emission results from inverse-Compton scattering of radio radiation from high-energy electrons in compact components. We show that the radio properties of brightest `knot' in the jet (`C5') can be fitted with a homogeneous sphere model whose parameters require bulk relativistic motion of the emitting material; otherwise the predicted model whose parameters require bulk relativistic motion of the emitting material; otherwise the predicted inverse-Compton X-ray emission exceeds the observed flux. If C5 is the origin of the X-ray emission, then it has a Doppler factor delta = 7.5((sup +3 sub -2)). If the nucleus or other components contribute to the X-ray emission, then this becomes a firm lower limit to delta. The inhomogeneous jet model of Koenigl is a good fit both to the barely resolved (less than 1 pc) flat-spectrum nucleus in the radio, and also to the ROSAT X-ray spectrum. The synchrotron and inverse-Compton emitting fluid moves down a narrow cone (opening angle 2 phi approximately 5 deg) nucleus relativistically, with delta approximately 4.6. Doppler factors for the nucleus and C5, derived from our ROSAT observation, provide evidence for bulk relativistic motion in the jet. By combining these constraints with well-known superluminal motion of jet components, we can deduce geometry. For epoch 1990.5 we infer the Lorentz factor gamma = 7.5 ((sup +1.0 sub -1.5)) and angle to the line of sight theta = 8((sup +2 deg sub -3 deg)) for H(sub 0) = 100 km/s/Mpc. These values are the most reliable yet derived using this method, because of the near-simultaneity of our X-ray and VLBI observations and the quality of the multifrequency of VLBI images and component radio spectra.

Unwin, S. C.; Wehrle, A. E.; Urry, C. M.; Gilmore, D. M.; Barton, E. J.; Kjerulf, B. C.; Zensus, J. A.; Rabaca, C. R.

1994-01-01

262

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

263

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

264

X-ray Emission from the Born-Again Planetary Nebula Abell 30  

NASA Astrophysics Data System (ADS)

The planetary nebula (PN) Abell 30 underwent a very late thermal pulse that resulted in the ejection of knots of hydrogen-poor material. ROSAT detected soft X-ray emission from these knots. We present deep Chandra and XMM-Newton observations that show this X-ray emission to consist of 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. The spatial distribution and spectral properties of the diffuse X-ray emission suggest that it is generated by the shock-heated plasma produced by the interaction of the present stellar wind with the hydrogen-poor ejecta of the born-again event. Charge-exchange reactions between the ions of the stellar winds and the born-again ejecta may also contribute to this emission. The origin of the X-ray emission from the central star of A 30 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.

2013-05-01

265

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

266

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

267

The angular distribution of energetic electron and X-ray emissions from triggered lightning leaders  

NASA Astrophysics Data System (ADS)

We investigate individual X-ray bursts from lightning leaders to determine if energetic electrons at the source (and hence X-rays) are emitted isotropically or with some degree of anisotropy. This study was motivated by the work of Saleh et al. (2009), which found the falloff of X-rays in concentric radial annuli, covering all azimuthal directions in each annulus, from the lightning channel to be most consistent with an isotropic electron source. Here we perform a statistical analysis of angular and spatial distributions of X-rays measured by up to 21 NaI/PMT detectors at the International Center for Lightning Research and Testing site for 21 leader X-ray bursts from five leaders (including four dart-stepped leaders and one dart leader). Two procedures were used to complete this analysis. Procedure 1 found the first-order anisotropy, and procedure 2 tested whether or not the angular distribution was consistent with an isotropic distribution. Because higher-order anisotropies could be present in the data, a distribution that is not isotropic does not necessarily have a significant first-order anisotropy. Using these procedures, we find that at least 11 out of 21 X-ray bursts have a statistically significant first-order anisotropy, and hence those 11 are inconsistent with an isotropic emission. The remaining 10 bursts do not have significant first-order anisotropy. However, of those 10 bursts, 9 are inconsistent with isotropic emission, since they exhibit significant higher-order anisotropies. Since Saleh et al. (2009) did not consider anisotropies in the azimuthal direction, these new measurements of anisotropy do not necessarily contradict that work. Indeed, our analysis supports the finding that the X-ray emissions from lightning are inconsistent with a vertically downward beam. The level of anisotropy of the runaway electrons is important because it provides, in principle, information on the streamer zone in front of the leader and the electric field near the lightning leader tip.

Schaal, M. M.; Dwyer, J. R.; Rassoul, H. K.; Hill, J. D.; Jordan, D. M.; Uman, M. A.

2013-10-01

268

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

269

X-ray emission mechanism for the gamma-ray binary LS 5039  

NASA Astrophysics Data System (ADS)

We address an unsolved issue in the model of the gamma-ray binary LS 5039, which consists of an O star and a compact object not yet identified. In previous studies, the X-ray emission observed with Suzaku has been assumed to be due to the synchrotron emission from high energy electrons, and the inverse Compton (IC) emission from low energy electrons has been neglected. However, this IC emission can affect the X-ray emission. In this study, we calculate the IC emission from low energy electrons (? < 10^4) accelerated near the compact object, including those created by the radiative cooling. We find that the IC emission of the low energy electrons can be responsible for the Suzaku band if the minimum Lorentz factor of injected electrons ?_{min} is around 10^3. In addition, we show that the Suzaku light curve is well reproduced if ?_{min} varies in proportion to the Fermi flux.

Yamaguchi, Masaki

2012-07-01

270

Formation and X-ray emission from hot bubbles in planetary nebulae  

NASA Astrophysics Data System (ADS)

We present 2D radiative-hydrodynamic simulations of the X-ray emission from hot bubbles in planetary nebulae (PNe). We particularly explore the effects of hydrodynamical mixing at the interface between the hot bubble and the cold nebular envelope, and its interplay with thermal conduction in the production of soft X-ray emission. The additional physical processes incorporated in our simulations add fine details to the inner nebular envelope in contact with the hot bubble, having implications on the PN optical morphology which are dependent on the initial stellar mass of the model.

Toala, J.; Arthur, S. J.

2014-04-01

271

Soft x-ray emission spectra and ferromagnetism in wide-gap doped semiconductors  

Microsoft Academic Search

A study is made of the resonant and nonresonant L x-ray emission spectra of impurities in the semiconducting compounds ZnS:Mn, ZnO:Mn, ZnO:Co, and Co2O:Mn. An analysis of the Mn L2,3 x-ray emission spectra of Zn1-xMnxS (x=0.1-0.3) reveals that the Mn impurities do not form clusters in the ZnS lattice. Studies of the Mn L2,3 spectra and electronic structure of epitaxial

T. P. Surkova; V. R. Galakhov; É. Z. Kurmaev

2009-01-01

272

Soft x-ray emission spectra and ferromagnetism in wide-gap doped semiconductors  

Microsoft Academic Search

A study is made of the resonant and nonresonant L x-ray emission spectra of impurities in the semiconducting compounds ZnS:Mn, ZnO:Mn, ZnO:Co, and Co2O:Mn. An analysis of the Mn L2,3 x-ray emission spectra of Zn1?xMnxS(x=0.1–0.3) reveals that the Mn impurities do not form clusters in the ZnS lattice. Studies of the Mn L2,3 spectra and electronic structure of epitaxial films

T. P. Surkova; V. R. Galakhov; E´. Z. Kurmaev

2009-01-01

273

The detection of X-ray emission from the OB associations of the Large Magellanic Cloud  

NASA Technical Reports Server (NTRS)

A systematic study of the X-ray properties of OB associations in the Large Magellanic Cloud has been carried out using data from the Einstein Observatory. An excess of young, X-ray-bright supernova remnants is found in the vicinity of the associations. In addition, diffuse X-ray emission is detected from over two dozen other associations; luminosities in the 0.16-3.5 keV band range from 2 x 10 to the 34th (the detection threshold) to 10 to the 36th ergs/s. For several of the more luminous examples, it is shown that emission from interstellar bubbles created by the OB stellar winds alone is insufficient to explain the emission. It is concluded that transient heating of the bubble cavities by recent supernovae may be required to explain the observed X-rays and that such a scenario is consistent with the number of X-ray-bright associations and the expected supernova rate from the young stars they contain.

Wang, Q.; Helfand, D. J.

1991-01-01

274

MODELING THE THERMAL DIFFUSE SOFT AND HARD X-RAY EMISSION IN M17  

SciTech Connect

We present numerical models of very young wind driven superbubbles. The parameters chosen for the simulations correspond to the particular case of the M17 nebula, but are appropriate for any young superbubble in which the wind sources have not completely dispersed their parental cloud. From the simulations, we computed the diffuse emission in the soft ([0.5-1.5] keV) and hard ([1.5-5] keV) X-ray bands. The total luminosity in our simulations agrees with the observations of Hyodo et al., about two orders of magnitude below the prediction of the standard model of Weaver et al.. The difference with respect to the standard (adiabatic) model is the inclusion of radiative cooling, which is still important in such young bubbles. We show that for this type of object the diffuse hard X-ray luminosity is significant compared to that of soft X-rays, contributing as much as 10% of the total luminosity, in contrast with more evolved bubbles where the hard X-ray emission is indeed negligible, being at least four orders of magnitude lower than the soft X-ray emission.

Velazquez, P. F.; Rodriguez-Gonzalez, A.; Esquivel, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Ap. 70-543, 04510 D.F. (Mexico)] [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Ap. 70-543, 04510 D.F. (Mexico); Rosado, M. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ap. 70-248, 04510 D.F. (Mexico)] [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ap. 70-248, 04510 D.F. (Mexico); Reyes-Iturbide, J., E-mail: pablo@nucleares.unam.mx, E-mail: ary@nucleares.unam.mx, E-mail: esquivel@nucleares.unam.mx, E-mail: margarit@astro.unam.mx [LATO-DCET/Universidade Estadual de Santa Cruz, Rodovia Jorge Amado, km 16, 45662-000 Ilheus, BA (Brazil)

2013-04-10

275

X-ray emission from T Tauri stars in the Lupus 3 star-forming region  

NASA Astrophysics Data System (ADS)

Aims.In this paper, I present analysis results of an {XMM-Newton} observation of the Lupus 3 region that contains a high proportion of young low mass (M < 0.3 M?) T Tauri stars in the Lupus star-forming complex. Methods: .The detection of X-ray sources in 0.5 to 4.5 keV images of the Lupus 3 core was performed using the standard source detection method of the {XMM-Newton} Science Analysis Software. The detected sources were correlated with a list of Herbig-Haro objects and H? emission stars that contains mainly classical T Tauri stars, with a catalogue of weak-line T Tauri Stars and with a recent list of new low-mass members of the Lupus 3 dark cloud found in a visible-light spectroscopic survey at the center of the Lupus 3 star-forming core. The light curves and spectra of the brightest X-ray sources with known T Tauri star counterparts were analysed. Results: .One hundred and two X-ray sources were detected in the 30´ diameter field-of-view of the EPIC cameras, of which 25 have visible or near-IR counterparts that are known as pre-main sequence stars. Their X-ray luminosity ranges from 3 × 1028 to 3 × 1030 erg s-1. Two of these objects with mass estimates lower than 0.075 M? have an X-ray luminosity of about 4-7 × 1028 erg s-1, comparable with that of flaring young brown dwarfs. A linear correlation is found between the X-ray luminosity and the mass or volume of the stars that is qualitatively expected from some models of distributed turbulent dynamos. The EPIC spectra of the X-ray brightest sources can be fitted using optically thin plasma emission models with two components at temperatures in the ranges 3-9 × 106 K and 1-50 × 107 K, respectively. The large emission measure of hot plasma may be caused by disruptions of magnetic fields associated with an intense flaring activity, while the X-ray emission from the "cool" plasma components may result from solar-type active regions. The emission measures of the plasma components are of the order of 1052 cm-3, typical of the values expected from coronal plasmas in T Tauri stars, post-T Tauri stars, and active late-type dwarfs in close binary systems. One property of the X-ray brightest stars in Lupus 3 that seems common among pre-main sequence stars is the low abundance of Fe.

Gondoin, P.

2006-08-01

276

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

277

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

278

An X-Ray Reprocessing Model of Disk Thermal Emission in Type 1 Seyfert Galaxies  

NASA Technical Reports Server (NTRS)

Using a geometry consisting of a hot central Comptonizing plasma surrounded by a thin accretion disk, we model the optical through hard X-ray spectral energy distributions of the type 1 Seyfert. galaxies NGC 3516 and NGC 7469. As in the model proposed by Poutanen, Krolik, and Ryde for the X-ray binary Cygnus X-1 and later applied to Seyfert galaxies by Zdziarski, Lubifiski, and Smith, feedback between the radiation reprocessed by the disk and the thermal Comptonization emission from the hot central plasma plays a pivotal role in determining the X-ray spectrum, and as we show, the optical and ultraviolet spectra as well. Seemingly uncorrelated optical/UV and X-ray light curves, similar to those which have been observed from these objects can, in principle, be explained by variations in the size, shape, and temperature of the Comptonizing plasma. Furthermore, by positing a disk mass accretion rate which satisfies a condition for global energy balance between the thermal Comptonization luminosity and the power available from accretion, one can predict the spectral properties of the heretofore poorly measured hard X-ray continuum above approximately 50 keV in type 1 Seyfert galaxies. Conversely, forthcoming measurements of the hard X-ray continuum by more sensitive hard X-ray and soft gamma-ray telescopes, such as those aboard the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) in conjunction with simultaneous optical, UV, and soft X-ray monitoring, will allow the mass accretion rates to be directly constrained for these sources in the context of this model.

Chiang, James; White, Nicholas E. (Technical Monitor)

2002-01-01

279

Einstein X-ray survey of the Pleiades - The dependence of X-ray emission on stellar age  

Microsoft Academic Search

The data obtained with two pointed observations of 1 deg by 1 deg fields of the Pleiades region have been analyzed, and the results are presented. The maximum-likelihood X-ray luminosity functions for the Pleiades G and K stars in the cluster are derived, and it is shown that, for the G stars, the Pleiades X-ray luminosity function is significantly brighter

G. Micela; S. Sciortino; S. Serio; G. S. Vaiana; J. Bookbinder; L. Golub; F. R. Harnden Jr.; R. Rosner

1985-01-01

280

X-Ray Emission from Early-Type Stars in the Orion Nebula Cluster  

NASA Astrophysics Data System (ADS)

The X-ray properties of twenty ~1 Myr old O, B, and A stars of the Orion Trapezium are examined with data from the Chandra Orion Ultradeep Project (COUP). On the basis of simple theories for X-ray emission, we define two classes separated at spectral type B4: hotter stars have strong winds that may give rise to X-ray emission in small- or large-scale wind shocks, and cooler stars that should be X-ray dark due to their weaker winds and absence of outer convection zones where dynamos can generate magnetic fields. Emission by late-type magnetically active companions may be present in either class. Sixteen of the 20 stars are detected with a wide range of X-ray luminosities, logLX (ergs s-1)~29-33, and X-ray efficiencies, log(LX/Lbol)~-4 to -8. Only two stars, ?1 Ori D (B0.5) and NU Ori (B1), show exclusively the constant soft-spectrum emission at log(LX/Lbol)~-7 expected from the standard model involving many small shocks in an unmagnetized radiatively accelerated wind. Most of the other massive O7-B3 stars exhibit some combination of soft-spectrum wind emission, hard-spectrum flaring, and/or rotational modulation indicating large-scale inhomogeneity. Magnetic confinement of winds with large-scale shocks can be invoked to explain these phenomena. This is supported in some cases by nonthermal radio emission and/or chemical peculiarities, or direct detection of the magnetic field (?1 Ori C). Most of the stars in the weak-wind class exhibit X-ray flares and logLX<31 ergs s-1, consistent with magnetic activity from known or unseen low-mass companions. In most cases, the X-ray spectra can be interpreted in terms of a two-temperature plasma model with a soft component of 3-10 MK and a hard component up to 40 MK. All nondetections belong to the weak-wind class. A group of stars exhibit hybrid properties-flarelike behavior superimposed on a constant component with logLX~32 ergs s-1-which suggest both magnetic activity and wind emission.

Stelzer, B.; Flaccomio, E.; Montmerle, T.; Micela, G.; Sciortino, S.; Favata, F.; Preibisch, T.; Feigelson, E. D.

2005-10-01

281

Feedback from winds and supernovae in massive stellar clusters - II. X-ray emission  

NASA Astrophysics Data System (ADS)

The X-ray emission from a simulated massive stellar cluster is investigated. The emission is calculated from a 3D hydrodynamical model which incorporates the mechanical feedback from the stellar winds of three O stars embedded in a giant molecular cloud (GMC) clump containing 3240 M? of molecular material within a 4 pc radius. A simple prescription for the evolution of the stars is used, with the first supernova (SN) explosion at t = 4.4 Myr. We find that the presence of the GMC clump causes short-lived attenuation effects on the X-ray emission of the cluster. However, once most of the material has been ablated away by the winds, the remaining dense clumps do not have a noticeable effect on the attenuation compared with the assumed interstellar medium (ISM) column. We determine the evolution of the cluster X-ray luminosity, LX, and spectra, and generate synthetic images. The intrinsic X-ray luminosity drops from nearly 1034 erg s-1 while the winds are `bottled up', to a near-constant value of 1.7 × 1032 erg s-1 between t = 1 and 4 Myr. LX reduces slightly during each star's red supergiant stage due to the depressurization of the hot gas. However, LX increases to ?1034 erg s-1 during each star's Wolf-Rayet stage. The X-ray luminosity is enhanced by two to three orders of magnitude to ˜1037 erg s-1 for at least 4600 yr after each SN explosion, at which time the blast wave leaves the grid and the X-ray luminosity drops. The X-ray luminosity of our simulation is generally considerably fainter than predicted from spherically symmetric bubble models, due to the leakage of hot gas material through gaps in the outer shell. This process reduces the pressure within our simulation and thus the X-ray emission. However, the X-ray luminosities and temperatures which we obtain are comparable to similarly powerful massive young clusters.

Rogers, H.; Pittard, J. M.

2014-06-01

282

Expressions to determine temperatures and emission measures for solar X-ray events from GOES measurements  

NASA Technical Reports Server (NTRS)

Expressions which give the effective color temperatures and corresponding emission measures for solar X-ray events observed with instruments onboard any of the GOES satellites are developed. Theoretical spectra were used to simulate the solar X-ray input at a variety of plasma temperatures. These spectra were folded through the wavelength dependent transfer functions for the two GOES detectors. The resulting detector responses and their ratio as a function of plasma temperature were then fit with simple analytic curves. Over the entire range between 5 and 30 million degrees, these fits reproduce the calculated color temperatures within 2% and the calculated emission measures within 5%. With the theoretical spectra, similar expressions for any pair of broadband X-ray detectors whose sensitivities are limited to wavelengths between 0.2 and 100 A are calculable.

Thomas, R. J.; Starr, R.; Crannell, C. J.

1984-01-01

283

HEAO 1 observations of X-ray emission from flares on dMe stars  

NASA Technical Reports Server (NTRS)

The paper reports the detection of two X-ray flares from each of the nearby dMe stars, AT Mic and AD Leo, with the A-2 experiment on board HEAO 1. A spectrum obtained during the brighter AT Mic flare, the first X-ray spectrum of a stellar flare, is well matched by a thermal model with a temperature 3 x 10 to the 7 K and an iron K-alpha emission line. The X-ray luminosities derived are in the range 1.3-16 x 10 to the 30th ergs/s, while emission measures are in the range 1.1-14 x 10 to the 53rd/cu cm. The estimated Lx/Lopt ratios exceed unity and are inconsistent with Mullan's flare model. Several scenarios to explain this discrepancy are proposed.

Kahn, S. M.; Mason, K. O.; Bowyer, C. S.; Linsky, J. L.; Haisch, B. M.; White, N. E.; Pravdo, S. H.

1979-01-01

284

X-ray and molecular emission from the nearest region of recent star formation.  

PubMed

The isolated, young, sunlike star TW Hya and four other young stars in its vicinity are strong x-ray sources. Their similar x-ray and optical properties indicate that the stars make up a physical association that is on the order of 20 million years old and that lies between about 40 and 60 parsecs (between about 130 and 200 light years) from Earth. TW Hya itself displays circumstellar CO, HCN, CN, and HCO+ emission. These molecules probably orbit the star in a solar-system-sized disk viewed more or less face-on, whereas the star is likely viewed pole-on. Being at least three times closer to Earth than any well-studied region of star formation, the TW Hya Association serves as a test-bed for the study of x-ray emission from young stars and the formation of planetary systems around sunlike stars. PMID:9204898

Kastner, J H; Zuckerman, B; Weintraub, D A; Forveille, T

1997-07-01

285

Chemical effects in the K? X-ray emission spectra of sulfur  

NASA Astrophysics Data System (ADS)

In this work our previous study about chemical effects in the K? spectra of S compounds employing high-resolution X-ray spectroscopy has been extended to the K? emission spectra. The measurements were performed with a wavelength dispersive single crystal spectrometer operated in the von Hamos geometry having an energy resolution comparable to the natural linewidth of the measured K? X-ray lines. The target fluorescence was produced by irradiating the samples with the bremsstrahlung from an X-ray tube. The energies and widths of the main components in the K? emission spectrum are given for different sulfur compounds (sulfide, sulfite, sulfate). The measured energy shifts between the K? lines of the compounds and elemental sulfur are presented as a function of the sulfur oxidation state and compared with the results obtained from the former K? measurements.

Kav?i?, M.; Dousse, J.-Cl.; Szlachetko, J.; Cao, W.

2007-07-01

286

Water maser emission from X-ray-heated circumnuclear gas in active galaxies  

NASA Technical Reports Server (NTRS)

We have modeled the physical and chemical conditions present within dense circumnuclear gas that is irradiated by X-rays from an active galactic nucleus. Over a wide range of X-ray fluxes and gas pressures, the effects of X-ray heating give rise to a molecular layer at temperatures of 400-1000 K within which the water abundance is large. The physical conditions within this molecular layer naturally give rise to collisionally pumped maser emission in the 6(sub 16) - 5(sub 23) 22 GHz transition of ortho-water, with predicted maser luminosities of 10(exp 2 +/- 0.5) solar luminosity per sq. pc of illuminated area. Given plausible assumptions about the geometry of the source and about the degree to which the maser emission is anisotropic, such surface luminosities are sufficient to explain the large apparent luminosities observed in water maser sources that are associated with active galactic nuclei.

Neufeld, David A.; Maloney, Philip R.; Conger, Sarah

1994-01-01

287

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

NASA Astrophysics Data System (ADS)

X-rays emitted from resonant coherently excited (RCE) n=2 states of 390 MeV/amu hydrogen-like Ar 17+ 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 static crystal field. The RCE probability of these Stark splitted substates differs, reflecting the polarization of the oscillating crystal field. However, the associated alignment was not clearly observed. It is explained by the fact that both polarization of the oscillating crystal field and the wave functions of Stark-mixed n=2 states depend on the distance from the channel center, and the X-ray emission is preferred in a channel center in a crystal.

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

2003-05-01

288

An unexpectedly rapid decline in the X-ray afterglow emission of long ?-ray bursts  

NASA Astrophysics Data System (ADS)

`Long' ?-ray bursts (GRBs) are commonly accepted to originate in the explosion of particularly massive stars, which give rise to highly relativistic jets. Inhomogeneities in the expanding flow result in internal shock waves that are believed to produce the ?-rays we see. As the jet travels further outward into the surrounding circumstellar medium, `external' shocks create the afterglow emission seen in the X-ray, optical and radio bands. Here we report observations of the early phases of the X-ray emission of five GRBs. Their X-ray light curves are characterised by a surprisingly rapid fall-off for the first few hundred seconds, followed by a less rapid decline lasting several hours. This steep decline, together with detailed spectral properties of two particular bursts, shows that violent shock interactions take place in the early jet outflows.

Tagliaferri, G.; Goad, M.; Chincarini, G.; Moretti, A.; Campana, S.; Burrows, D. N.; Perri, M.; Barthelmy, S. D.; Gehrels, N.; Krimm, H.; Sakamoto, T.; Kumar, P.; Mészáros, P. I.; Kobayashi, S.; Zhang, B.; Angelini, L.; Banat, P.; Beardmore, A. P.; Capalbi, M.; Covino, S.; Cusumano, G.; Giommi, P.; Godet, O.; Hill, J. E.; Kennea, J. A.; Mangano, V.; Morris, D. C.; Nousek, J. A.; O'Brien, P. T.; Osborne, J. P.; Pagani, C.; Page, K. L.; Romano, P.; Stella, L.; Wells, A.

2005-08-01

289

Relation between x-ray emission mechanism and crystal structure in LiNbO3  

NASA Astrophysics Data System (ADS)

x-ray emission in LiNbO3 is confirmed by thermal treatments in a vacuum system by a new cleaning method of the crystal. Detailed single-crystal high-temperature x-ray structure refinements were carried out at 297, 323, 373, 423 and 473 K, far below the phase transition (~1473 K). The unit cell dimensions a and V show a linear increase with temperature; however, the lattice parameter, c shows only a slight linear increase. The length of Nb O bonds in adjacent octahedra is almost constant below 423 K. It is suggested that the valence electron in Nb changes in the compound. Therefore, x-ray emission induced by charged particles including electrons can be considered to have a close relation to the electric charge of Nb in LiNbO3.

Nakanishi, Y.; Mizota, H.; Ito, Y.; Takano, M.; Fukao, S.; Yoshikado, S.; Ohyama, K.; Yamada, K.; Fukushima, S.

2006-05-01

290

X-Ray Emission from Orion Nebula Cluster Stars with Circumstellar Disks and Jets  

NASA Astrophysics Data System (ADS)

We investigate the X-ray and near-infrared emission properties of a sample of pre-main-sequence (PMS) stellar systems in the Orion Nebula Cluster (ONC) that display evidence for circumstellar disks (``proplyds'') and optical jets in Hubble Space Telescope (HST) imaging. Our study uses X-ray data acquired during Chandra Orion Ultradeep Program (COUP) observations, as well as complementary optical and near-infrared data recently acquired with HST and the Very Large Telescope (VLT), respectively. Approximately 70% of ~140 proplyds were detected as X-ray sources in the 838 ks COUP observation of the ONC, including ~25% of proplyds that do not display central stars in HST imaging. In near-infrared imaging, the detection rate of proplyd central stars is >90%. Many proplyds display near-infrared excesses, suggesting disk accretion is ongoing onto the central, PMS stars. About 50% of circumstellar disks that are detected in absorption in HST imaging contain X-ray sources. For these sources, we find that X-ray absorbing column and apparent disk inclination are well correlated, providing insight into the disk scale heights and metal abundances of UV- and X-ray-irradiated protoplanetary disks. Approximately 2/3 of the ~30 proplyds and PMS stars exhibiting jets in Hubble images have COUP X-ray counterparts. These jet sources display some of the largest near-infrared excesses among the proplyds, suggesting that the origin of the jets is closely related to ongoing, PMS stellar accretion. One morphologically complex jet source, d181-825, displays a double-peaked X-ray spectral energy distribution with a prominent soft component that is indicative of strong shocks in the jet collimation region. A handful of similar objects also display X-ray spectra that are suggestive of shocks near the jet source. These results support models in which circumstellar disks collimate and/or launch jets from young stellar objects and, furthermore, demonstrate that star-disk-jet interactions may contribute to PMS X-ray emission.

Kastner, Joel H.; Franz, Geoffrey; Grosso, Nicolas; Bally, John; McCaughrean, Mark J.; Getman, Konstantin; Feigelson, Eric D.; Schulz, Norbert S.

2005-10-01

291

WEAK HARD X-RAY EMISSION FROM TWO BROAD ABSORPTION LINE QUASARS OBSERVED WITH NuSTAR: COMPTON-THICK ABSORPTION OR INTRINSIC X-RAY WEAKNESS?  

SciTech Connect

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 Almost-Equal-To 400-600 hard X-ray ({approx}> 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed (N{sub H} {approx}< 10{sup 24} cm{sup -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{sub H} Almost-Equal-To 7 Multiplication-Sign 10{sup 24} cm{sup -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{alpha} 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. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Alexander, D. M.; Hickox, R. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Harrison, F. A.; Fuerst, F.; Grefenstette, B. W.; Madsen, K. K. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Bauer, F. E. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, F. E. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Comastri, A. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Farrah, D. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Fiore, F. [Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone (Italy); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Matt, G. [Dipartimento di Matematica e Fisica, Universita degli Studi Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Ogle, P. [IPAC, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125 (United States); and others

2013-08-01

292

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

293

Study of x-ray emission from a table top plasma focus and its application as an x-ray backlighter  

NASA Astrophysics Data System (ADS)

A study of a 2 kJ, 200 kA, table top plasma focus device as an intense x-ray source is reported. The x-ray yield from a number of gases, (deuterium, nitrogen, neon, argon, and xenon) is measured as a function of filling pressure and in neon as a function of anode length. In gases with Z<18, the plasma implodes to form a uniform cylindrical column, whereas for Z>=18, the plasma consists of a number of hot spots. A maximum x-ray yield of 16.6 J and pulse length of 10-15 ns was obtained in neon. The x-ray emission was established to be due to H- and He-like line radiation. The temperature estimated from spectroscopic observations was about 300-400 eV at an electron density of (3-5)×1020 cm-3 in neon. At low pressures in neon, hard x-ray radiation, presumably due to electron beams was dominant. Mesh images of different wire materials were recorded at the optimum pressure in neon as a proof of principle for x-ray backlighting.

Beg, F. N.; Ross, I.; Lorenz, A.; Worley, J. F.; Dangor, A. E.; Haines, M. G.

2000-09-01

294

The Sun's X-ray Emission During the Recent Solar Minimum  

NASA Astrophysics Data System (ADS)

The Sun recently underwent a period of a remarkable lack of major activity such as large flares and sunspots, without equal since the advent of the space age a half century ago. A widely used measure of solar activity is the amount of solar soft X-ray emission, but until recently this has been below the threshold of the X-ray-monitoring Geostationary Operational Environmental Satellites (GOES). There is thus an urgent need for more sensitive instrumentation to record solar X-ray emission in this range. Anticipating this need, a highly sensitive spectrophotometer called Solar Photometer in X-rays (SphinX) was included in the solar telescope/spectrometer TESIS instrument package on the third spacecraft in Russia's Complex Orbital Observations Near-Earth of Activity of the Sun (CORONAS-PHOTON) program, launched 30 January 2009 into a near-polar orbit. SphinX measures X-rays in a band similar to the GOES longer-wavelength channel.

Sylwester, Janusz; Kowalinski, Mirek; Gburek, Szymon; Siarkowski, Marek; Kuzin, Sergey; Farnik, Frantisek; Reale, Fabio; Phillips, Kenneth J. H.

2010-02-01

295

Soft x-ray emission excited resonantly and nonresonantly by synchrotron radiation  

NASA Astrophysics Data System (ADS)

This paper is a summary of some of the recent activities of our soft x-ray spectroscopy group. We are using soft x-ray emission spectroscopy to probe the electronic properties of matter, emphasizing atoms in the bulk and at interfaces. In particular we have used incoherent photon excitation to obtain a basic understanding of the electronic properties of a wide variety of materials such as yttrium oxide and titanium diboride, we have used the penetrating power of x-rays to study multilayers of silicon and iron and have shown that iron silicide is present in the silicon layer and provides evidence that in the antiferromagnetic Fe/Si multilayer system the FeSi2 layer is conducting rather than insulating. The ubiquitous presence of Raman scattering has been used to elucidate the electronic band structure of materials including graphite and hexagonal boron nitride. Such scattering can produce dramatic changes in the emission spectrum that can further the basic understanding of the electronic band structure. We have made a systematic study of Raman scattering in several transition metal compounds, including their borides, oxides, and sulfides. Photon-in photon-out soft x-ray spectroscopy has many applications, and is adding a new dimension to soft x-ray spectroscopy by providing many opportunities for exciting research, especially at third generation synchrotron light sources.

Ederer, D. L.; Carlisle, J. A.; Jimenez, J.; Jia, J. J.; Zhou, Ling; Callcott, T. A.; Perera, R. C. C.; Moewes, A.; Terminello, L. J.; Shirley, E.; Asfaw, A.; van Ek, J.; Morikawa, E.; Himpsel, F. J.

1997-01-01

296

Non-destructive Analysis of Buried Interfaces and Surface Layers: X-Ray Emission Spectroscopic Study  

NASA Astrophysics Data System (ADS)

Soft X-ray emission spectroscopy (SXES) and extended X-ray emission fine structure (EXEFS) studies have been carried out on a heat-treated thin-film(Ni)/substrate(Si, SiC) contact system using a conventional X-ray micro-analysis (XMA) apparatus. We have successfully deduced information either the chemical bonding or atomic configuration by the former and the latter, respectively. Also, we have succeeded in analyzing an interface buried rather deep below an overlayer, e.g., more than a hundred nm. This is due to the fact that both an X-ray production depth of an energetic electron is much larger than the mean free path of an energetic electron and the mean free path of an X-ray photon in a solid is large. Namely, in the surface, or interface layer, Ni2Si and NiSi2 formation have been clarified for heat-treated Ni/SiC and Ni/Si systems, respectively.

Iwami, Motohiro; Hirai, Masaaki; Kusaka, Masahiko; Morii, Takashi

2003-07-01

297

X-ray emission from near-main-sequence B stars  

NASA Technical Reports Server (NTRS)

Results of a Roengten Satellite (ROSAT) X-ray survey of 12 nearby near-main-sequence B stars are presented. Objects with very low interstellar hydrogen column density were chosen to study the soft X-ray emission properties of the stars. All of the stars were detected at the 3 sigma level. Spectral fits to seven of the stars are presented, and temperatures and source emission measures are derived. The spectra and characterized by emission from gas at a temperature of about 2 x 10(exp 6) K, which is lower than that typically observed for O stars. The ratio L(sub x)/L(sub Bol) decreases sharply with spectral types later than B1, reaching values of about 10(exp -9) at B3 V; much less than the value of 10(exp -7) that holds for O stars and early-B stars. The survey includes four beta Cephei stars and two Be stars. Our observations are consistent with the finding that beta Cephei variables have softer spectra than other stars of the same spectral type. The X-ray emission measures for the stars are compared with upper and lower limits derived using mass loss rates and terminal velocities from line-driven wind theory. It is concluded that if shocks embedded in the winds are the source of the X-ray emission then a significant fraction of the winds in B stars must be hot. One to a few shocks can account for the observed emission measures. As a function of spectral type, there appears to be a transition in X-ray emission properties at about B1 to B1.5, with later type stars having a smaller L(sub x)/L(sub Bol) ratio. Coronal and shock models are discussed in regards to the BO V star tau Sco which has an anomalously high source temperature.

Cassinelli, J. P.; Cohen, D. H.; Macfarlane, J. J.; Sanders, W. T.; Welsh, B. Y.

1994-01-01

298

X-ray emission in heavy-ion collisions. Progress report, April 1, 1979-March 31, 1980  

SciTech Connect

Recent research in the cyclotron institute and department of chemistry at Texas A and M University on the x-ray emission in heavy-ion collisions is described. Areas covered include: spectra of Ka x-rays from 64 MeV sulfur ions traveling in solids; foil-excited Ka x-ray transitions in few-electron sulfur ions; high-resolution study of the target thickness dependence of x-ray emission from 65 MeV sulfur ions; dynamic screening of highly stripped sulfur ions in solids; Mg Ka x-ray satellites excited by ion bombardment, multiplet structure and dependence on projectile and chemical environment; angular distributions of beam and target Ka x-rays; chemical effects on K x-ray satellites of fluorine compounds; and a non-linear least-squares peak-fitting program employing Voight functions. (GHT)

Watson, R.L.

1980-04-01

299

RX J1301.9+2747: A Highly Variable Seyfert Galaxy with Extremely Soft X-Ray Emission  

NASA Astrophysics Data System (ADS)

In this paper we present a temporal and spectral analysis of X-ray data from XMM-Newton and Chandra observations of the ultrasoft and variable Seyfert galaxy RX J1301.9+2747. In both observations the source clearly displays two distinct states in the X-ray band: a long quiescent state and a short flare (or eruptive) state which differs in count rates by a factor of 5-7. The transition from the quiescent to the flare state occurs in 1-2 ks. We have observed that the quiescent state spectrum is unprecedentedly steep with a photon index ? ~ 7.1, and the spectrum of the flare state is flatter with ? ~ 4.4. X-rays above 2 keV were not significantly detected in either state. In the quiescent state, the spectrum appears to be dominated by a blackbody component of temperature about ~30-40 eV, which is comparable to the expected maximum effective temperature from the inner accretion disk. The quiescent state, however, requires an additional steep power law, presumably arising from Comptonization by transient heated electrons. The optical spectrum from the Sloan Digital Sky Survey shows Seyfert-like narrow lines for RX J1301.9+2747, while Hubble Space Telescope imaging reveals a central point source for the object. In order to precisely determine the hard X-ray component, future longer X-ray observations are required. This will help constrain the accretion disk model for RX J1301.9+2747, and shed new light on the characteristics of the corona and accretion flows around black holes.

Sun, Luming; Shu, Xinwen; Wang, Tinggui

2013-05-01

300

RX J1301.9+2747: A HIGHLY VARIABLE SEYFERT GALAXY WITH EXTREMELY SOFT X-RAY EMISSION  

SciTech Connect

In this paper we present a temporal and spectral analysis of X-ray data from XMM-Newton and Chandra observations of the ultrasoft and variable Seyfert galaxy RX J1301.9+2747. In both observations the source clearly displays two distinct states in the X-ray band: a long quiescent state and a short flare (or eruptive) state which differs in count rates by a factor of 5-7. The transition from the quiescent to the flare state occurs in 1-2 ks. We have observed that the quiescent state spectrum is unprecedentedly steep with a photon index {Gamma} {approx} 7.1, and the spectrum of the flare state is flatter with {Gamma} {approx} 4.4. X-rays above 2 keV were not significantly detected in either state. In the quiescent state, the spectrum appears to be dominated by a blackbody component of temperature about {approx}30-40 eV, which is comparable to the expected maximum effective temperature from the inner accretion disk. The quiescent state, however, requires an additional steep power law, presumably arising from Comptonization by transient heated electrons. The optical spectrum from the Sloan Digital Sky Survey shows Seyfert-like narrow lines for RX J1301.9+2747, while Hubble Space Telescope imaging reveals a central point source for the object. In order to precisely determine the hard X-ray component, future longer X-ray observations are required. This will help constrain the accretion disk model for RX J1301.9+2747, and shed new light on the characteristics of the corona and accretion flows around black holes.

Sun Luming; Shu Xinwen; Wang Tinggui, E-mail: lmsun@mail.ustc.edu.cn, E-mail: xwshu@mail.ustc.edu.cn, E-mail: twang@ustc.edu.cn [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2013-05-10

301

The Detection of Circumnuclear X-Ray Emission from the Seyfert Galaxy NGC 3516  

NASA Technical Reports Server (NTRS)

We present the first high-resolution, X-ray image of the circumnuclear regions of the Seyfert 1 galaxy NGC 3516, using the Chandra X-ray Observatory (CXO). All three of the CXO observations reported were performed with one of the two grating assemblies in place, and here we restrict our analysis to undispersed photons (i.e. those detected in the zeroth-order). A previously-unknown X-ray source is detected approximately 6 arcsec (1.1h(sub 75)(exp -1) kpc) NNE of the nucleus (position angle approximately 29 degrees) which we designate CXOU 110648.1 + 723412. Its spectrum can be characterized as a power law with a photon index (Gamma) approximately 1.8 - 2.6, or as thermal emission with a temperature kT approximately 0.7 - 3 keV. Assuming a location within NGC 3516, isotropic emission implies a luminosity L approximately 2 - 8 x 10(exp 39)h(sub 75)(exp-2) erg s(exp -1) in the 0.4 - 2 keV band. If due to a single point source, the object is super-Eddington for a 1.4 solar mass neutron star. However, multiple sources or a small, extended source cannot be excluded using the current data. Large-scale extended S-ray emission is also detected out to approximately 10 arcsec (approximately 2h(sub 75)(exp -1) kpc) from the nucleus to the NE and SW, and is approximately aligned with the morphologies of the radio emission and extended narrow emission line region (ENLR). The mean luminosity of this emission is 1 - 5 x 10(exp 37)h(sub 75)(exp -2) erg s(exp -1) arcsec(exp -2), in the 0.4 - 2 keV band. Unfortunately the current data cannot usefully constrain its spectrum. These results are consistent with earlier suggestions of circumnuclear X-ray emissi in NGC 3516 based on ROSAT observations, and thus provide the first clear detection of extended X-ray emission in a Seyfert 1.0 galaxy. If the extended emission is due to scattering of the nuclear X-ray continuum, then the pressure in the X-ray emitting gas is at least two orders of magnitude too small to provide the confining medium for the ENLR clouds.

George, I. M.; Turner, T. J.; Netzer, H.; Kraemer, S. B.; Ruiz, J.; Chelouche, D.; Crenshaw, D. M.; Yaqoob, T.; Nandra, K.; Mushotzky, R. F.; White, Nicholas E. (Technical Monitor)

2001-01-01

302

X-ray emission from supernova remnants near gamma-ray sources  

NASA Technical Reports Server (NTRS)

It is noted that the imaging proportional of the Einstein Observatory has been used to search for X-ray emission from eight radio supernova remnants which are near three of the Cos-B unidentified gamma-ray sources: 2CG 311-01, CG 327-0, and CG 333+0. Emissions are observed from three of the remnants and upper limits on the remainder which are consistent with the luminosity expected from a simple blast-wave heated plasma model of the process. Thus none of the remnants are superluminous as might be expected if the pattern of the Crab Nebula were followed. It is thought that the remnant RCW 103 may be Vela-like. It is noted that another of the remnants, Kes 27, has centrally peaked X-ray emission which is unlike the shell-like emission seen for many remnants and which does not correlate well with its asymmetric radio emission.

Lamb, R. C.; Markert, T. H.

1981-01-01

303

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

304

Disentangling X-Ray Emission Processes in Vela-Like Pulsars  

NASA Technical Reports Server (NTRS)

We present a deep observation with the X-Ray Multimirror Mission of PSR B1823-13, a young pulsar with similar properties to the Vela pulsar. We detect two components to the X-ray emission associated with PSR B1823-13: an elongated core of extent 30 min immediately surrounding the pulsar embedded in a fainter, diffuse component of emission 5 sec in extent, seen only on the southern side of the pulsar. The pulsar itself is not detected, either as a point source or through its pulsations. Both components of the X-ray emission are well fitted by a power-law spectrum, with photon index Gamma approx. 1.6 and X-ray luminosity (0.5-10 keV) L(sub X) approx. 9 x 10(exp 32) ergs/s for the core and Gamma approx. 2.3 and L(sub X) approx. 3 x 10(exp 33) ergs/s for the diffuse emission, for a distance of 4 kpc. We interpret both components of emission as corresponding to a pulsar wind nebula, which we designate G18.0-0.7. We argue that the core region represents the wind termination shock of this nebula, while the diffuse component indicates the shocked downstream wind. We propose that the asymmetric morphology of the diffuse emission with respect to the pulsar is the result of a reverse shock from an associated supernova remnant, which has compressed and distorted the pulsar-powered nebula. Such an interaction might be typical for pulsars at this stage in their evolution. The associated supernova remnant is not detected directly, most likely being too faint to be seen in existing X-ray and radio observations.

Gaensler, Bryan; Mushotzky, Richard (Technical Monitor)

2003-01-01

305

X-ray emission from reverse-shocked ejecta in supernova remnants  

NASA Technical Reports Server (NTRS)

A simple physical model of the dynamics of a young supernova remnant is used to derive a straightforward kinematical description of the reverse shock. With suitable approximations, formulae can then be developed to give the X-ray emission of the reverse-shocked ejecta. The results are found to agree favorably with observations of SN1006.

Cioffi, Denis F.; Mckee, Christopher F.

1990-01-01

306

The X-ray emission of Compton-thick Seyfert 2 galaxies.  

NASA Astrophysics Data System (ADS)

The author briefly summarizes some theoretical and observational results on the X-ray emission of Compton-thick Seyfert 2 galaxies, i.e. sources in which the obscuring torus is optically thick to Compton scattering (NH ? 1024cm-2).

Matt, G.

1996-02-01

307

Particle Induced X-Ray Emission for Quantitative Trace-Element Analysis Using the Eindhoven Cyclotron.  

National Technical Information Service (NTIS)

Development of a multi-elemental trace analysis technique using PIXE (Particle Induced X-ray Emission), was started almost five years ago at the Eindhoven University of Technology, in the Cyclotron Applications Group of the Physics Department. The aim of ...

H. Kivits

1980-01-01

308

The merits of particle induced X-ray emission in revealing painting techniques  

Microsoft Academic Search

Particle induced X-ray emission (PIXE) at the external proton beam has proved ideal to study individual techniques of creating art objects. In particular, PIXE is suitable for examining paintings because of the low level of background produced by organic components like binders and paper backings. Thus, traces of pigments as deposited from pens on cardboard can be identified by this

C. Neelmeijer; M. Mäder

2002-01-01

309

Ultrasoft x-ray emission from a linear ECR plasma source  

NASA Astrophysics Data System (ADS)

Ultrasoft x-ray emission in the energy range 10-100 eV is observed from a linear electron cyclotron resonance (ECR) plasma system. ECR plasma is produced in a short cylindrical stainless steel (SS) chamber with a central axial magnetic field of 875 G, generated by two coils placed axially to have the first two ECR surfaces inside the experimental chamber. Plasma is produced in a pressure range of 2 × 10-5 mbar with hydrogen. Also, plasma is produced with net microwave power varying from 160 to 800 W at 2.45 GHz frequency from a magnetron. The waveguide from the magnetron to the vacuum vessel supports rectangular TE10 mode and the electromagnetic wave propagation in plasma is in extraordinary (X) mode. The ultrasoft x-ray emission is observed with a vacuum photodiode. The results clearly indicate a decrease in x-ray emission on increasing the working pressure and an increase in emission with an increase in the input microwave power. The experiments also ensure that the presence of a metal target enhances the intensity of soft x-rays generated in the ECR plasma system.

Yadav, Vipin K.; Bora, D.

2004-05-01

310

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...

311

X-ray emission from the giant molecular clouds in the Galactic Center region and the discovery of new X-ray sources  

NASA Astrophysics Data System (ADS)

We report the results of X-ray (2-10 keV) observations of the giant molecular clouds Sgr B, Sgr C and Sgr D in the Galactic Center region, together with the discovery of the point-like source SAX J1748.2-2808. The data have been obtained with the MECS instrument on the BeppoSAX satellite. The core of Sgr B2 has an X-ray luminosity of ~ 6*E34 erg s-1 and its spectrum is characterized by a strong Fe emission line at ~ 6.5 keV with an equivalent width of 2 keV. Faint diffuse X-ray emission is detected from Sgr C and from the SNR G1.05-0.15 (Sgr D). A new, unresolved source with a strong Fe line has been discovered in the Sgr D region. This source, SAX J1748.2-2808, is probably associated with a SiO and OH maser source at the Galactic Center distance. If so, its luminosity is 1034 erg s-1. We propose that the X-ray emission from SAX J1748.2-2808 is produced either by protostars or by a giant molecular cloud core. Emission from sources similar to SAX J1748.2-2808 could have an impact on the expected contribution on the observed Fe line emission from the Galactic ridge.

Sidoli, L.; Mereghetti, S.; Treves, A.; Parmar, A. N.; Turolla, R.; Favata, F.

2001-06-01

312

X-ray emission associated with radio galaxies in the Perseus cluster  

NASA Technical Reports Server (NTRS)

In this paper, we report on new x-ray observations of the Perseus cluster made using four separate pointings of the Roentgen Satellite (ROSAT) Positron Sensitive Proportional Counter (PSPC). We searched for x-ray emission associated with 16 radio galaxies and detected six above 3 sigma. We made use of the PSPC spectra to determine if the x-ray emission associated with radio galaxies in Perseus is thermal or nonthermal in origin (i.e., hot gas or an active galactic nuclei (AGN)). For the head-tail radio galaxy IC 310, we find that the data are best fit by a power law model with an unusually large spectral index alpha = 2.7. This is consistent with its unresolved spatial structure. On the other hand, a second resolved x-ray source associated with another radio galaxy 2.3 Mpc from the Perseus center (V Zw 331) is best fit by a thermal model. For three sources with insufficient flux for a full spectral analysis, we calculated hardness ratios. On this basis, the x-ray emission associated with the well known head-tail source NGC 1265 is consistent with thermal radiation. The x-ray spectra of UGC 2608 and UGC 2654 probably arise from hot gas, although very steep power-law spectra (alpha greater than 3.2) are also possible. The spectrum of NGC 1275 is quite complex due to the presence of an AGN and the galaxy's location at the center of a cluster cooling flow.

Rhee, George; Burns, Jack O.; Kowalski, Michael P.

1994-01-01

313

X-ray emission scaling law from a plasma focus with different anode tip materials (Cu, Mo, and W)  

Microsoft Academic Search

X-ray emission from a 2.3-5.3 kJ Mather-type plasma focus [Phys. Fluids 7, 5 (1964)] employing copper, molybdenum, and tungsten anode tip is studied. Argon is used as a working gas. Characteristic Cu Kalpha and Mo K-series emission and their ratio to the continuous x-rays are determined. From the variation of the x-ray yield data with filling pressure at different charging

M. Sharif; S. Ahmad; M. Zakaullah; S. Hussain; A. Waheed

2006-01-01

314

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

NASA Technical Reports Server (NTRS)

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 percent) and circular (19 percent) 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 percent + or - 6 percent, 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.

Cordova, F. A.; Middleditch, J.; Hjellming, R. M.; Mason, K. O.

1989-01-01

315

What's important at z>5? X-ray Emission from Starbursts!  

NASA Astrophysics Data System (ADS)

There has recently been quite a bit of excitement on the role of X-ray emission from galaxies in reionization. It turns out that the X-ray output from X-ray binaries and hot gas are both likely important and may rival the ionizing output of AGN at z>5, particularly for Hydrogen reionization. Here we present our research on constraining the X-ray SED of high-redshift galaxies using an important local universe analog population, the Lyman Break Galaxy Analogs. We have established a relationship between the 2-10 keV X-ray luminosity, assumed to originate from X-ray binaries (XRBs), and star formation rate (SFR) in rest-frame UV-selected galaxies across cosmic time -- ranging from Lyman break galaxies (LBGs) in the early Universe (z=1.5-4) to Lyman break analogs (LBAs) in the present-day Universe ( 0.1). We present results from the 4Ms Chandra Deep Field South (CDF-S) observations of ~4000 z=1.5-4 LBGs as well as in-depth studies of a sample of six nearby GALEX-selected 0.1 LBAs, which are individually X-ray detected. Both populations may yield a larger output in collective HMXB luminosity per unit SFR than that observed in local (z=0) star-forming galaxies. We also discuss the properties of the hot gas in these galaxies, particularly what we hope to learn with next generation facilities such as the Athena calorimeter.

Hornschemeier, Ann E.; Basu-Zych, Antara; Yukita, Mihoko; Mineo, Stefano; Lehmer, Bret; Ptak, Andrew; Fragos, Tassos; Zezas, Andreas

2014-08-01

316

Emission statistics of X-ray induced photoelectrons and its comparison with electron- and ion-induced electron emissions  

Microsoft Academic Search

The emission statistics of secondary electrons from a gold metal surface induced by monochromatic X-rays is studied by Monte Carlo simulations. The number distributions of emitted electrons n and their mean values ? are calculated systematically for incident photon energies from 1 to 100keV. The results are compared with recent experimental results measured at the SPring-8 X-ray beam facility (BL15XU).

K. Ohya; K. Inai; A. Nisawa; A. Itoh

2008-01-01

317

Current sheath curvature correlation with the neon soft x-ray emission from plasma focus device  

Microsoft Academic Search

The insulator sleeve length is one of the major parameters that can\\u000a severely affect the neon soft x-ray yield from a plasma focus. The\\u000a effect of the insulation sleeve length on various characteristic timings\\u000a of plasma focus discharges and hence the soft x-ray emission\\u000a characteristics has been investigated using a resistive divider. The\\u000a pinhole images and laser shadowgraphy are used

T. Zhang; X. Lin; K. A. Chandra; T. L. Tan; S. V. Springham; A. Patran; P. Lee; S. Lee; R. S. Rawat

2005-01-01

318

X-ray emission in slow highly charged ion-surface collisions  

NASA Astrophysics Data System (ADS)

X-rays emitted in the collisions of highly charged ions with a surface have been measured to investigate dissipation schemes of their potential energies. While 8.1% of the potential energy was dissipated in the collisions of He-like I ions with a W surface, 29.1% has been dissipated in the case of He-like Bi ions. The x-ray emissions play significant roles in the dissipation of the potential energies in the interaction of highly charged heavy ions with the surface.

Watanabe, H.; Abe, T.; Fujita, Y.; Sun, J.; Takahashi, S.; Tona, M.; Yoshiyasu, N.; Nakamura, N.; Sakurai, M.; Yamada, C.; Ohtani, S.

2007-03-01

319

The hard X-ray emission spectra from accretion columns in intermediate polars  

NASA Technical Reports Server (NTRS)

We consider the hard (greater than 2 keV) X-ray emission from accretion columns in an intermediate polar system, GK Per, using a simple settling solution. The rate of photon emission per logarithmic energy interval can be fitted with a power law, E(exp -gamma), with gamma approximately 2.0, in agreement with observations. This index is only weakly dependent on the mass accretion rate, dot-M, for dot-M in the range of a few times 10(exp 16-18) g/s. The peak energy of the photon spectra (after photoelectric absorption) is expected to be E(sub p) approximately (5 keV) gamma(exp -1/3) (N(sub H)/10(exp 23)/sq cm)(exp 1/3) where N(sub H) is the hydrogen column density along the line of sight. The observed spectra of GK Per and possibly of V1223 Sgr suggest N(sub H) approximately 10(exp 23)/sq cm. This large N(sub H) may be due to partially ionized preshock column material. Alternatively, we also consider absorption by the cool outer parts of an accretion disk. In this case the photoelectric absorption depth in the disk is a sensitive function of inclination. For GK Per the required inclination is approximately 83 deg. For mass accretion rates larger than a critical rate of approximately 10(exp 18) g/s, X-ray emission from the column accretion is significantly affected by radiation drag. Although the mass accretion rate increases dramatically during outbursts, the observed hard (greater than 2 keV) X-ray luminosity will not rise proportionately. The slope and peak energy of the outburst spectra are only weakly affected. We conclude that the observed X-ray spectra can be explained by this simple analytic solution and that the production of hard X-rays from the accretion shock at the magnetic poles in the intermediate polars is in general agreement with the observations. However, since the X-ray emission and absorption depend on the mass accretion rate in a complicated manner, observed hard X-ray luminosities (greater than 2 keV) are not a good indicator of the mass accretion rate in the X-ray emitting regions.

Yi, Insu; Vishniac, Ethan T.

1994-01-01

320

Radio/X-Ray Luminosity Relation for Advection Dominated Accretion: Implications for Emission-Line Galaxies and the X-Ray Background  

NASA Technical Reports Server (NTRS)

Recent studies of the cosmic X-ray background (XRB) have suggested the possible existence of a population of relatively faint sources with hard X-ray spectra; however, the emission mechanism remains unclear. If the hard X-ray emission is from the radiatively inefficient, advection-dominated accretion flows (ADAFs) around massive black holes in galactic nuclei, X-ray luminosity and radio luminosity satisfy the approximate relation L(sub R) approx. 7 x 10(exp 35)(upsilon/15 GHz)(sup 7/5(M/10(exp 7)solar mass)(L(sub X) ergs/s)(sup 1/10 ergs/s, where L(sub R) = (upsilon)L(sub upsilon) is the radio luminosity at frequency upsilon, M is the mass of the accreting black hole, and 10(exp 40) less than or equal to L(sub X) less than or equal to 10(exp 42) ergs/s is the 2-10 keV X-ray luminosity. These sources are characterized by inverted radio spectra I(sub upsilon) varies as upsilon(exp 2/5). For example, an ADAF X-ray source with luminosity L(sub X) approx. 10(exp 41) ergs/s has a nuclear radio luminosity of approx. 4 x 10(M/3 x 10(exp 7) solar mass) ergs/s at approx. 20 GHz, and if it is at a distance of approx. 10(M/3 x 10(exp 7) solar mass) Mpc, it would be detected as a approx. 1 mJy point radio source. High-frequency (approx. 20 GHz), high angular resolution radio observations provide an important test of the ADAF emission mechanism. Since L,, depends strongly on black hole mass and only weakly on X-ray luminosity, the successful measurement of nuclear radio emission could provide an estimate of black hole mass. Because the X-ray spectra produced by ADAFs are relatively hard, sources of this emission are natural candidates for contributing to the hard (greater than 2 keV) background.

Yi, Insu; Boughn, Stephen P.

1998-01-01

321

Modeling of the EUV and X-Ray Emission Spectra Induced by the Solar Winds Ions in the Heliosphere  

NASA Technical Reports Server (NTRS)

We have carried out investigation of the EUV and X-ray emission spectra induced in interaction between the Solar Wind (SW) and interstellar neutral gas. The spectra of most important SW ions have been computed for the charge-exchange mechanism of X-ray emission using new accurate spectroscopic data from recent laboratory measurements and theoretical calculations. Total spectra have been constructed as a sum of spectra induced in the charge-exchange collisions by individual O(exp q+), C(exp q+), N(exp q+), Ne(exp q+), Mg (exp q+) and Fe(exp q+) ions. Calculations have been performed for X-ray emission from the heliospheric hydrogen and helium gas. X-ray maps of the heliosphere have been computed. The power density of X-ray sources in the heliospheric ecliptic plane is shown for the H gas and for the He gas. Distances from the Sun (0,0) are given in AU. The helium cone is clear seen in the X-ray map of the charge-exchange emission induced by the solar wind. X-ray emission spectra detected by the Chandra X-ray telescope from the "dark" side of Moon has been identified as a X-ray background emission induced by the solar wind from the geocorona. Spectra and intensities of this charge-exchange X-rays have been compared with the heliospheric component of the X-ray background. Observations and modeling of the SW spectra induced from the geocorona indicate a strong presence of emission lines of highly charged oxygen ions. Anisotropy in distribution of heliospheric X-rays has been predicted and calculated for the regions of the fast and slow solar winds.

Kharchenko, Vasili

2005-01-01

322

Modeling the diffuse X-ray emission of planetary nebulae with different chemical composition  

NASA Astrophysics Data System (ADS)

Based on time-dependent radiation-hydrodynamics simulations of the evolution of Planetary Nebulae (PNe), we have carried out a systematic parameter study to address the non-trivial question of how the diffuse X-ray emission of PNe with closed central cavities is expected to depend on the evolutionary state of the nebula, the mass of the central star, and the metallicity of stellar wind and circumstellar matter. We have also investigated how the model predictions depend on the treatment of thermal conduction at the interface between the central `hot bubble' and the `cool' inner nebula, and compare the results with recent X-ray observations. Our study includes models whose properties resemble the extreme case of PNe with Wolf-Rayet type central stars. Indeed, such models are found to produce the highest X-ray luminosities.

Steffen, Matthias; Sandin, Christer; Jacob, Ralf; Schönberner, Detlef

2012-08-01

323

X-RAY EMISSION FROM SUPERNOVAE IN DENSE CIRCUMSTELLAR MATTER ENVIRONMENTS: A SEARCH FOR COLLISIONLESS SHOCKS  

SciTech Connect

The optical light curve of some supernovae (SNe) may be powered by the outward diffusion of the energy deposited by the explosion shock (the so-called shock breakout) in optically thick ({tau} {approx}> 30) circumstellar matter (CSM). Recently, it was shown that the radiation-mediated and radiation-dominated shock in an optically thick wind must transform into a collisionless shock and can produce hard X-rays. The X-rays are expected to peak at late times, relative to maximum visible light. Here we report on a search, using Swift/XRT and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense CSM. Our sample includes 19 Type IIn SNe, one Type Ibn SN, and eight hydrogen-poor superluminous SNe (SLSN-I such as SN 2005ap). Two SNe (SN 2006jc and SN 2010jl) have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSM. However, the X-ray emission from SN 2006jc can also be explained as originating in an optically thin region. Thus, we propose that the optical light curve of SN 2010jl is powered by shock breakout in CSM. We suggest that two other events (SN 2010al and SN 2011ht) were too X-ray bright during the SN maximum optical light to be explained by the shock-breakout model. We conclude that the light curves of some, but not all, SNe IIn/Ibn are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all of the SLSN-I events, our X-ray limits are not deep enough and were typically obtained too early (i.e., near the SN maximum light) for definitive conclusions about their nature. Late-time X-ray observations are required in order to further test whether these SNe are indeed embedded in dense CSM. We review the conditions required for a shock breakout in a wind profile. We argue that the timescale, relative to maximum light, for the SN to peak in X-rays is a probe of the column density and the density profile above the shock region. In SNe whose X-ray emission slowly rises, and peaks at late times, the optical light curve is likely powered by the diffusion of shock energy in a dense CSM. We note that if the CSM density profile falls faster than a constant-rate wind-density profile, then X-rays may escape at earlier times than estimated for the wind-profile case. Furthermore, if the CSM has a region in which the density profile is very steep relative to a steady wind-density profile, or if the CSM is neutral, then the radio free-free absorption may be sufficiently low for radio emission to be detected.

Ofek, E. O.; Gal-Yam, A.; Yaron, O.; Arcavi, I. [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel)] [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel); Fox, D. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)] [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Cenko, S. B.; Filippenko, A. V.; Bloom, J. S. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)] [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Sullivan, M. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom)] [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Gnat, O. [Racah Institute of Physics, The Hebrew University of Jerusalem, 91904 Jerusalem (Israel)] [Racah Institute of Physics, The Hebrew University of Jerusalem, 91904 Jerusalem (Israel); Frail, D. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)] [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Horesh, A.; Kulkarni, S. R. [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)] [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Corsi, A. [LIGO Laboratory, Division of Physics, California Institute of Technology, MS 100-36, Pasadena, CA 91125 (United States)] [LIGO Laboratory, Division of Physics, California Institute of Technology, MS 100-36, Pasadena, CA 91125 (United States); Quimby, R. M. [Kavli IPMU, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan)] [Kavli IPMU, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan); Gehrels, N. [NASA-Goddard Space Flight Center, Greenbelt, MD 20771 (United States)] [NASA-Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Nugent, P. E. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)] [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Kasliwal, M. M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)] [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Bildsten, L. [Kavli Institute for Theoretical Physics, Kohn Hall, University of California, Santa Barbara, CA 93106 (United States)] [Kavli Institute for Theoretical Physics, Kohn Hall, University of California, Santa Barbara, CA 93106 (United States); Poznanski, D. [School of Physics and Astronomy, Tel Aviv University, Tel Aviv (Israel)] [School of Physics and Astronomy, Tel Aviv University, Tel Aviv (Israel); and others

2013-01-20

324

X-Ray Emission from Supernovae in Dense Circumstellar Matter Environments: A Search for Collisionless Shocks  

NASA Astrophysics Data System (ADS)

The optical light curve of some supernovae (SNe) may be powered by the outward diffusion of the energy deposited by the explosion shock (the so-called shock breakout) in optically thick (? >~ 30) circumstellar matter (CSM). Recently, it was shown that the radiation-mediated and radiation-dominated shock in an optically thick wind must transform into a collisionless shock and can produce hard X-rays. The X-rays are expected to peak at late times, relative to maximum visible light. Here we report on a search, using Swift/XRT and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense CSM. Our sample includes 19 Type IIn SNe, one Type Ibn SN, and eight hydrogen-poor superluminous SNe (SLSN-I such as SN 2005ap). Two SNe (SN 2006jc and SN 2010jl) have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSM. However, the X-ray emission from SN 2006jc can also be explained as originating in an optically thin region. Thus, we propose that the optical light curve of SN 2010jl is powered by shock breakout in CSM. We suggest that two other events (SN 2010al and SN 2011ht) were too X-ray bright during the SN maximum optical light to be explained by the shock-breakout model. We conclude that the light curves of some, but not all, SNe IIn/Ibn are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all of the SLSN-I events, our X-ray limits are not deep enough and were typically obtained too early (i.e., near the SN maximum light) for definitive conclusions about their nature. Late-time X-ray observations are required in order to further test whether these SNe are indeed embedded in dense CSM. We review the conditions required for a shock breakout in a wind profile. We argue that the timescale, relative to maximum light, for the SN to peak in X-rays is a probe of the column density and the density profile above the shock region. In SNe whose X-ray emission slowly rises, and peaks at late times, the optical light curve is likely powered by the diffusion of shock energy in a dense CSM. We note that if the CSM density profile falls faster than a constant-rate wind-density profile, then X-rays may escape at earlier times than estimated for the wind-profile case. Furthermore, if the CSM has a region in which the density profile is very steep relative to a steady wind-density profile, or if the CSM is neutral, then the radio free-free absorption may be sufficiently low for radio emission to be detected.

Ofek, E. O.; Fox, D.; Cenko, S. B.; Sullivan, M.; Gnat, O.; Frail, D. A.; Horesh, A.; Corsi, A.; Quimby, R. M.; Gehrels, N.; Kulkarni, S. R.; Gal-Yam, A.; Nugent, P. E.; Yaron, O.; Filippenko, A. V.; Kasliwal, M. M.; Bildsten, L.; Bloom, J. S.; Poznanski, D.; Arcavi, I.; Laher, R. R.; Levitan, D.; Sesar, B.; Surace, J.

2013-01-01

325

Charge localization on a polymer surface measured by triboelectrically induced x-ray emission  

NASA Astrophysics Data System (ADS)

The means by which charge is exchanged between two surfaces that have been brought into contact is perhaps the longest standing unsolved problem in physics. To this day, it is debated as to whether charging is due to electrons or ions. Contact electrification is such a singular process that it lies beyond the scope of density functional theory and other ab initio theories of material structure. We present a new method for studying the fundamental processes that underlie triboelectrification, based upon the structure of x-ray emission from the interface of separating surfaces. Our measurement of the x-ray spectrum emitted from lead rolling against various thicknesses of unplasticized polyvinyl chloride (uPVC) on top of a grounded conductor indicate that triboelectrification, like turbulence, extends over a broad range of length scales. We observe millimeter-scale charge-patching, which indicates the feasibility of building MEMS x-ray sources.

Collins, Adam L.; Camara, Carlos G.; Naranjo, Brian B.; Putterman, Seth J.; Hird, Jonathan R.

2013-08-01

326

The origin of X-ray emission from T Tauri stars.  

NASA Astrophysics Data System (ADS)

Several aspects concerning the origin of the very strong X-ray activity of T Tauri Stars (TTS) are still not well understood. Important new insight came recently from the Chandra Orion Ultradeep Project (COUP), a unique 10-day long Chandra observation of the Orion Nebula Cluster, and the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST). Based mainly on the results of these two large projects, I will discuss our current knowledge about the location of the X-ray emitting structures in TTS, the nature of their coronal magnetic fields, inferences for pre-main-sequence magnetic dynamos, and the relation between accretion processes and X-ray emission.

Preibisch, Thomas

327

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

NASA Technical Reports Server (NTRS)

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 E sub a are derived for NGC 2992, NGC 5506, and NGC 7582. The X-ray spectra of these galaxies are similar to those of type 1 Seyfert galaxies. In the case of NGC 5506 and NGC 7582, the absorbing column N sub H derived is about one order of magnitude greater than predicted from the reddening of thy optical continuum and of the Balmer lines. Possible explanations for the discrepancy are discussed.

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

1982-01-01

328

Current sheath curvature correlation with the neon soft x-ray emission from plasma focus device  

NASA Astrophysics Data System (ADS)

The insulator sleeve length is one of the major parameters that can severely affect the neon soft x-ray yield from a plasma focus. The effect of the insulation sleeve length on various characteristic timings of plasma focus discharges and hence the soft x-ray emission characteristics has been investigated using a resistive divider. The pinhole images and laser shadowgraphy are used to explain the observed variation in the average soft x-ray yield (measured using a diode x-ray spectrometer) with variation of the insulator sleeve length. We have found that for a neon filled plasma focus device the change in insulator sleeve length changes the current sheath curvature angle and thus the length of the focused plasma column. The optimized current sheath curvature angle is found to be between 39° and 41°, at the specific axial position of 6.2-9.3 cm from the cathode support plate, for our 3.3 kJ plasma focus device. A strong dependence of the neon soft x-ray yield on the current sheath curvature angle has thus been reported.

Zhang, T.; Lin, X.; Chandra, K. A.; Tan, T. L.; Springham, S. V.; Patran, A.; Lee, P.; Lee, S.; Rawat, R. S.

2005-05-01

329

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

330

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

331

DISCOVERY OF X-RAY EMISSION IN THE OLD CLASSICAL NOVA DK LACERTAE  

SciTech Connect

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 Multiplication-Sign 10{sup -3} counts s{sup -1}, corresponding to a detection significance level of 5{sigma}. 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 Multiplication-Sign 10{sup 22} cm{sup -2}. Assuming a distance of 3900 pc to the source, the luminosity was 10{sup 32}-10{sup 34} erg s{sup -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.; Drake, J. J. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Sakamoto, T., E-mail: dtakei@head.cfa.harvard.edu [Department of Physics and Mathematics, College of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara-shi, Kanagawa 252-5258 (Japan)

2013-01-01

332

X-Ray Emission from the Unidentified Gamma-Ray Transient GRO J1838-0415  

NASA Technical Reports Server (NTRS)

The gamma-ray transient GRO J1838-04 is one of the most enigmatic sources in the sky. Despite its closeness to the Galactic plane, it showed a strong gamma-ray flare in 1995 typical of blazars. However, no blazar is detected in its approx. 1 deg. error box, and a Galactic source is suspected. Other time variable gamma-ray sources are known in the Galactic disk, and GRO J1838-04 may belong to a new class of sources (isolated young pulsars, the only proven Galactic gamma-ray sources, do not show variability). The Advanced Satellite for Cosmology and Astrophysics (ASCA) observed the centroid of the Energetic Gamma Ray Experiment Telescope (EGRET) error box of GRO J1838-04 in April 1997. Five weak X-ray sources are detected, one of which appears to be diffuse (3 arcmins). No known radio source is coincident with the X-ray sources. A preliminary report of our results appeared and a more systematic report is being written . The fact that no prominent X-ray source appears in the field, excludes an X-ray transient source with strong persistent emission is a possible counterpart of GRO JI838- 04 (such as superluminal transients). To uncover the nature of GRO J1838-04 requires more study of the weak X-ray sources in its error box, and a long-time scale monitoring of their variability.

Tavani, Marco

1998-01-01

333

Multiplexing radiography based on carbon nanotube field emission X-ray technology  

NASA Astrophysics Data System (ADS)

State-of-the-art tomographic imaging technique is based upon of simple serial imaging scheme. The tomographic scanners collect the projection images sequentially in the time domain, by a step-and-shoot process using a single-pixel x-ray source. The inefficient serial data collection scheme severely limits the data collection speed, which is critical for imaging of objects in rapid motion such as for diagnosis of cardiovascular diseases, CT fluoroscopy, and airport luggage inspection. Further improvement of the speed demands an increasingly high x-ray peak workload and gantry rotation speed, both of which have approached the engineering limits. Multiplexing technique, which has been widely adopted in communication devices and in certain analytical instruments, holds the promise to significantly increase the data throughput. It however, has not been applied to x-ray radiography, mainly due to limitations of the current x-ray source technology. Here we report a method for frequency multiplexing radiography (FMR) based on the frequency multiplexing principle and the carbon nanotube field emission x-ray technology. We show the feasibility of multiplexing radiography that enables simultaneous collection of multiple projection images. It has the potential to significantly increase the imaging speed for tomographic imaging without compromising the imaging quality.

Zhang, J.; Yang, G.; Lee, Y.; Chang, S.; Lu, J. P.; Zhou, O.

2007-03-01

334

Transient Extremely Soft X-ray Emission from the Unusually Bright Cataclysmic Variable in the Globular Cluster M3: A New CV X-ray Luminosity Record?  

NASA Astrophysics Data System (ADS)

We observed the accreting white dwarf (WD) 1E1339.8+2837 (1E1339) in the globular cluster M3 in 2003 November, 2004 May, and 2005 January, using the Chandra ACIS-S detector. The source was observed in 1992 to possess traits of a supersoft X-ray source (SSS), with a 0.1-2.4 keV luminosity as large as 2 × 1035 erg s-1, after which time the source's luminosity fell by roughly two orders of magnitude, adopting a hard X-ray spectrum more typical of cataclysmic variables (CVs). Our observations confirm 1E1339's hard CV-like spectrum, with photon index ? = 1.3 ± 0.2. We found 1E1339 to be highly variable, with a 0.5-10 keV luminosity ranging from (1.4 ± 0.3) × 1034 erg s-1 to 8.5+4.9 - 4.6 × 1032 erg s-1, with 1E1339's maximum luminosity being perhaps the highest yet recorded for hard X-ray emission from a WD. In 2005 January, 1E1339 displayed substantial low-energy emission below ~0.3 keV. Although current Chandra responses cannot properly model this emission, its bolometric luminosity appears comparable to or greater than that of the hard spectral component. This raises the possibility that the supersoft X-ray emission seen from 1E1339 in 1992 may have shifted to the far-UV.

Stacey, W. S.; Heinke, C. O.; Elsner, R. F.; Edmonds, P. D.; Weisskopf, M. C.; Grindlay, J. E.

2011-05-01

335

EARLY THERMAL X-RAY EMISSION FROM LONG GAMMA-RAY BURSTS AND THEIR CIRCUMSTELLAR ENVIRONMENTS  

SciTech Connect

We performed a series of hydrodynamical calculations of an ultrarelativistic jet propagating through a massive star and the circumstellar matter (CSM) to investigate the interaction between the ejecta and the CSM. We succeed in distinguishing two qualitatively different cases in which the ejecta are shocked and adiabatically cool. To examine whether the cocoon expanding at subrelativistic speeds emits any observable signal, we calculate the expected photospheric emission from the cocoon. It is found that the emission can explain early thermal X-ray emission recently found in some long gamma-ray bursts (GRBs). The result implies that the difference of the circumstellar environment of long GRBs can be probed by observing their early thermal X-ray emission.

Suzuki, Akihiro [Center for Computational Astrophysics, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Shigeyama, Toshikazu [Research Center for the Early Universe, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2013-02-10

336

X-ray-emission measurements following charge exchange between C6+ and H2  

NASA Astrophysics Data System (ADS)

Lyman x-ray spectra following charge exchange between C6+ and H2 are presented for collision velocities between 400 and 2300 km/s (1-30 keV/amu). Spectra were measured by a microcalorimeter x-ray detector capable of fully resolving the C vi Lyman series emission lines though Lyman-?. The ratios of the measured emission lines are sensitive to the angular momentum l states populated during charge exchange and are used to gauge the effectiveness of different l-distribution models in predicting Lyman emission due to charge exchange. At low velocities, we observe that both single-electron-capture and double-electron-capture autoionization contribute to Lyman emission and that a statistical l distribution best describes the measured line ratios. At higher velocities single-electron capture dominates with the l distribution peaked at the maximum l.

Fogle, M.; Wulf, D.; Morgan, K.; McCammon, D.; Seely, D. G.; Dragani?, I. N.; Havener, C. C.

2014-04-01

337

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

NASA Technical Reports Server (NTRS)

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. 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, and that the emitting plasma may be in a non-equilibrium state. 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. Subject headings: X-rays: stars -stars: early-type-stars: individual (q Car)

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

2008-01-01

338

Structure of the X-Ray Emission from the Jet of 3C 273  

NASA Technical Reports Server (NTRS)

We present images from four Chandra observations of the quasar 3C 273. The zeroth order images from two grating observations using the AXAF CCD Imaging Spectrometer (ACIS-S) detector are used to examine the structure and spectrum of the jet. The jet has at least four distinct features which are not resolved in previous observations. Using jet feature nomenclature based on HST observations, we find that knot Al is very bright in X-rays. We have measured the X-ray spectrum of this X-ray knot for the first time, obtaining a photon index of 1.36 +/- 0.11 and a flux density of 37 +/- 4 nJy at 1 keV. Combining this measurement with lower frequency data shows that a pure synchrotron model can fit the spectrum of knot Al from 4 GHz to 5 keV (over nine decades in energy) without a change of spectral slope. Knot A2 is also detected and is somewhat blended with knot B1 but synchrotron emission is not likely to explain the X-ray emission due to the spectral turnover observed in the optical-UV band. No other knots are clearly detected but there is an indication of weak emission from the eastern portion of knot H3. near the "head," which is radio-bright. There is diffuse flux which extends from 14 arcsec to 20 arcsec which shows curvature that is comparable to the optical flux found by Bahcall, et al.

Marshall, H. L.; Lee, J. C.; Ogle, P. M.; Drake, J. J.; Fruscione, A.; Grimes, J.; Harris, D.; Kraft, R.; Pease, D.; Schwartz, D.; Siemiginowska, A.; Lavoie, Anthony R. (Technical Monitor)

2000-01-01

339

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

340

X-RAY EMISSION FROM THE WOLF-RAYET BUBBLE S 308  

SciTech Connect

The Wolf-Rayet (WR) bubble S 308 around the WR star HD 50896 is one of the only two WR bubbles known to possess X-ray emission. We present XMM-Newton observations of three fields of this WR bubble that, in conjunction with an existing observation of its northwest quadrant, map most of the nebula. The X-ray emission from S 308 displays a limb-brightened morphology, with a central cavity {approx}22' in size and a shell thickness of {approx}8'. This X-ray shell is confined by the optical shell of ionized material. The spectrum is dominated by the He-like triplets of N VI at 0.43 keV and O VII at 0.57 keV, and declines toward high energies, with a faint tail up to 1 keV. This spectrum can be described by a two-temperature optically thin plasma emission model (T{sub 1} {approx} 1.1 Multiplication-Sign 10{sup 6} K, T{sub 2} {approx} 13 Multiplication-Sign 10{sup 6} K), with a total X-ray luminosity {approx}2 Multiplication-Sign 10{sup 33} erg s{sup -1} at the assumed distance of 1.5 kpc.

Toala, J. A.; Guerrero, M. A. [Instituto de Astrofisica de Andalucia, IAA-CSIC, Glorieta de la Astronomia s/n, 18008 Granada (Spain); Chu, Y.-H.; Gruendl, R. A. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Arthur, S. J. [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Campus Morelia, Apartado Postal 3-72, 58090, Morelia, Michoacan (Mexico); Smith, R. C. [NOAO/CTIO, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Snowden, S. L., E-mail: toala@iaa.es [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States)

2012-08-10

341

Periodic X-Ray Emission from the O7 V Star ?1 Orionis C  

NASA Astrophysics Data System (ADS)

We report the discovery of large-amplitude, periodic X-ray emission from the O7 V star ?1 Orionis C, the central star of the Orion Nebula. Ten ROSAT HRI snapshots of the Trapezium cluster taken over the course of 21 days show that the count rate of ?1 Ori C varies from 0.26 to 0.41 counts s-1 with a clear 15 day period. The soft X-ray variations have the same phase and period as H? and He II ?4686 variations reported by Stahl et al. and are in antiphase with the C IV and Si IV ultraviolet absorption features. We consider five mechanisms which might explain the amplitude, phase, and periodicity of the X-ray variations: (1) colliding-wind emission with an unseen binary companion, (2) coronal emission from an unseen late-type pre-main-sequence star, (3) periodic density fluctuations, (4) absorption of magnetospheric X-rays in a corotating wind, and (5) magnetosphere eclipses. The ROSAT data rule out the first three scenarios but cannot rule out either of the latter two which require the presence of an extended magnetosphere, consistent with the suggestion of Stahl et al. that ?1 Ori C is an oblique magnetic rotator. As such, ?1 Ori C may be the best example of a high-mass analog to the chemically peculiar, magnetic Bp stars.

Gagné, Marc; Caillault, Jean-Pierre; Stauffer, John R.; Linsky, Jeffrey L.

1997-04-01

342

Periodic X-ray Emission from the O7 V star theta (1) Orionis C  

NASA Astrophysics Data System (ADS)

Ten ROSAT HRI snapshots of the Trapezium cluster taken over the course of 21 days show that the count rate of the O7 V star theta (1) Orionis C varies from 0.26 to 0.41 counts s(-1) with a clear 15-day period. The soft X-ray variations have the same phase and period as H? and He II lambda 4686 variations reported by Stahl et al., and are in anti-phase with the C IV and Si IV ultraviolet absorption features. We consider five mechanisms which might explain the amplitude, phase, and periodicity of the X-ray variations: (1) colliding-wind emission with the wind of an unseen binary companion, (2) coronal emission from an unseen late-type pre-main--sequence star, (3) periodic density fluctuations, (4) absorption of magnetospheric X-rays in a corotating wind, and (5) magnetosphere eclipses. The ROSAT data rule out the first three scenarios, but cannot rule out either of the latter two which require the presence of an extended magnetosphere, consistent with the suggestion of Stahl et al. that theta (1) Ori C is an oblique magnetic rotator. We present preliminary models of X-ray emission and absorption from the magnetosphere and wind of an O-type oblique magnetic rotator.

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

1996-12-01

343

X-Ray Emission from the Wolf-Rayet Bubble S 308  

NASA Astrophysics Data System (ADS)

The Wolf-Rayet (WR) bubble S 308 around the WR star HD 50896 is one of the only two WR bubbles known to possess X-ray emission. We present XMM-Newton observations of three fields of this WR bubble that, in conjunction with an existing observation of its northwest quadrant, map most of the nebula. The X-ray emission from S 308 displays a limb-brightened morphology, with a central cavity ~22' in size and a shell thickness of ~8'. This X-ray shell is confined by the optical shell of ionized material. The spectrum is dominated by the He-like triplets of N VI at 0.43 keV and O VII at 0.57 keV, and declines toward high energies, with a faint tail up to 1 keV. This spectrum can be described by a two-temperature optically thin plasma emission model (T 1 ~ 1.1 × 106 K, T 2 ~ 13 × 106 K), with a total X-ray luminosity ~2 × 1033 erg s-1 at the assumed distance of 1.5 kpc. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Toalá, J. A.; Guerrero, M. A.; Chu, Y.-H.; Gruendl, R. A.; Arthur, S. J.; Smith, R. C.; Snowden, S. L.

2012-08-01

344

MEASUREMENT OF THE RADIUS OF NEUTRON STARS WITH HIGH SIGNAL-TO-NOISE QUIESCENT LOW-MASS X-RAY BINARIES IN GLOBULAR CLUSTERS  

SciTech Connect

This paper presents the measurement of the neutron star (NS) radius using the thermal spectra from quiescent low-mass X-ray binaries (qLMXBs) inside globular clusters (GCs). Recent observations of NSs have presented evidence that cold ultra dense matter-present in the core of NSs-is best described by ''normal matter'' equations of state (EoSs). Such EoSs predict that the radii of NSs, R{sub NS}, are quasi-constant (within measurement errors, of {approx}10%) for astrophysically relevant masses (M{sub NS}>0.5 M{sub Sun }). The present work adopts this theoretical prediction as an assumption, and uses it to constrain a single R{sub NS} value from five qLMXB targets with available high signal-to-noise X-ray spectroscopic data. Employing a Markov chain Monte-Carlo approach, we produce the marginalized posterior distribution for R{sub NS}, constrained to be the same value for all five NSs in the sample. An effort was made to include all quantifiable sources of uncertainty into the uncertainty of the quoted radius measurement. These include the uncertainties in the distances to the GCs, the uncertainties due to the Galactic absorption in the direction of the GCs, and the possibility of a hard power-law spectral component for count excesses at high photon energy, which are observed in some qLMXBs in the Galactic plane. Using conservative assumptions, we found that the radius, common to the five qLMXBs and constant for a wide range of masses, lies in the low range of possible NS radii, R{sub NS}=9.1{sup +1.3}{sub -1.5} km (90%-confidence). Such a value is consistent with low-R{sub NS} equations of state. We compare this result with previous radius measurements of NSs from various analyses of different types of systems. In addition, we compare the spectral analyses of individual qLMXBs to previous works.

Guillot, Sebastien; Rutledge, Robert E. [Department of Physics, McGill University, 3600 rue University, Montreal, QC, H2X-3R4 (Canada); Servillat, Mathieu [Laboratoire AIM (CEA/DSM/IRFU/SAp, CNRS, Universite Paris Diderot), CEA Saclay, Bat. 709, F-91191 Gif-sur-Yvette (France); Webb, Natalie A., E-mail: guillots@physics.mcgill.ca, E-mail: rutledge@physics.mcgill.ca [Universite de Toulouse, UPS-OMP, IRAP, Toulouse (France)

2013-07-20

345

DETECTION OF DIFFUSE X-RAY EMISSION FROM PLANETARY NEBULAE WITH NEBULAR O VI  

SciTech Connect

The presence of O VI ions can be indicative of plasma temperatures of a few Multiplication-Sign 10{sup 5} K that are expected in heat conduction layers between the hot shocked stellar wind gas at several 10{sup 6} K and the cooler (10{sup 4} 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.; Guerrero, M. A. [Instituto de Astrofisica de Andalucia, IAA-CSIC, c/ Glorieta de la Astronomia s/n, E-18008 Granada (Spain)] [Instituto de Astrofisica de Andalucia, IAA-CSIC, c/ Glorieta de la Astronomia s/n, E-18008 Granada (Spain); Chu, Y.-H.; Gruendl, R. A. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States)] [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Jacob, R.; Schoenberner, D.; Steffen, M., E-mail: nieves@iaa.es [Leibniz-Institut fuer Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

2013-04-10

346

The Discovery of X-ray Emission from Active Galactic Nuclei  

NASA Astrophysics Data System (ADS)

Back in 1974 the UHURU catalog (3U) had been published with many UHGLS - unidentified high galactic latitude sources. Identifications were hampered by the square degree sized error boxes (positional uncertainties). Could these explain the cosmic X-ray background? Could UHGLS be "X-ray galaxies"? Only three active galaxies (AGNs) had been found as X-ray sources: 3C273, Cen A and NGC 4151, while others had upper limits. What was the difference between X-ray and non-X-ray AGNs? It turned out that the slightly better positioning capability and slightly deeper sensitivity of the Ariel V Sky Survey Instrument (SSI), launched in October 1974, were just enough to show that the UHGLS were Seyfert galaxies. And I was lucky enough that I'd joined the Leicester X-ray group and had taken on the UHGLS for my PhD thesis, with Ken Pounds as my supervisor. With the SSI we made a catalog of high latitude sources, the "2A" catalog, including about a dozen known Seyfert galaxies (lowish luminosity nearby AGNs) and, with Mike Penston and Martin Ward, we went on to identify many of them with both newly discovered normal broad emission line AGNs and a few new "narrow emission line galaxies", or NELGs, as we called them. We are now convinced that it is summation of many obscured NELGs that produce the flat spectrum of the X-ray background, and we are still searching for them in Chandra deep surveys and at higher energies with NuSTAR. There was an obvious connection between the X-ray obscuration and the optical reddening, which must lie outside the region emitting the broad optical spectral lines. Andy Lawrence and I, following a clue from Bill Keel, put this together into what we now call the Unified Scheme for AGN structure. This idea of a flattened torus obscuring the inner regions of the AGN was so dramatically confirmed a few years later -- by Ski Antonucci and Joe Miller's discovery of polarized broad emission lines in NGC1068 -- that the precursor papers became irrelevant. But Ariel V had provided the seeds for this advance too. Not bad for 100cm2 and 1/2 degree collimators.

Elvis, Martin

2013-01-01

347

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

348

Energy-dispersive X-ray emission spectroscopy using an X-ray free-electron laser in a shot-by-shot mode.  

PubMed

The ultrabright femtosecond X-ray pulses provided by X-ray free-electron lasers open capabilities for studying the structure and dynamics of a wide variety of systems beyond what is possible with synchrotron sources. Recently, this "probe-before-destroy" approach has been demonstrated for atomic structure determination by serial X-ray diffraction of microcrystals. There has been the question whether a similar approach can be extended to probe the local electronic structure by X-ray spectroscopy. To address this, we have carried out femtosecond X-ray emission spectroscopy (XES) at the Linac Coherent Light Source using redox-active Mn complexes. XES probes the charge and spin states as well as the ligand environment, critical for understanding the functional role of redox-active metal sites. K?(1,3) XES spectra of Mn(II) and Mn(2)(III,IV) complexes at room temperature were collected using a wavelength dispersive spectrometer and femtosecond X-ray pulses with an individual dose of up to >100 MGy. The spectra were found in agreement with undamaged spectra collected at low dose using synchrotron radiation. Our results demonstrate that the intact electronic structure of redox active transition metal compounds in different oxidation states can be characterized with this shot-by-shot method. This opens the door for studying the chemical dynamics of metal catalytic sites by following reactions under functional conditions. The technique can be combined with X-ray diffraction to simultaneously obtain the geometric structure of the overall protein and the local chemistry of active metal sites and is expected to prove valuable for understanding the mechanism of important metalloproteins, such as photosystem II. PMID:23129631

Alonso-Mori, Roberto; Kern, Jan; Gildea, Richard J; Sokaras, Dimosthenis; Weng, Tsu-Chien; Lassalle-Kaiser, Benedikt; Tran, Rosalie; Hattne, Johan; Laksmono, Hartawan; Hellmich, Julia; Glöckner, Carina; Echols, Nathaniel; Sierra, Raymond G; Schafer, Donald W; Sellberg, Jonas; Kenney, Christopher; Herbst, Ryan; Pines, Jack; Hart, Philip; Herrmann, Sven; Grosse-Kunstleve, Ralf W; Latimer, Matthew J; Fry, Alan R; Messerschmidt, Marc M; Miahnahri, Alan; Seibert, M Marvin; Zwart, Petrus H; White, William E; Adams, Paul D; Bogan, Michael J; Boutet, Sébastien; Williams, Garth J; Zouni, Athina; Messinger, Johannes; Glatzel, Pieter; Sauter, Nicholas K; Yachandra, Vittal K; Yano, Junko; Bergmann, Uwe

2012-11-20

349

Energy-dispersive X-ray emission spectroscopy using an X-ray free-electron laser in a shot-by-shot mode  

PubMed Central

The ultrabright femtosecond X-ray pulses provided by X-ray free-electron lasers open capabilities for studying the structure and dynamics of a wide variety of systems beyond what is possible with synchrotron sources. Recently, this “probe-before-destroy” approach has been demonstrated for atomic structure determination by serial X-ray diffraction of microcrystals. There has been the question whether a similar approach can be extended to probe the local electronic structure by X-ray spectroscopy. To address this, we have carried out femtosecond X-ray emission spectroscopy (XES) at the Linac Coherent Light Source using redox-active Mn complexes. XES probes the charge and spin states as well as the ligand environment, critical for understanding the functional role of redox-active metal sites. K?1,3 XES spectra of MnII and Mn2III,IV complexes at room temperature were collected using a wavelength dispersive spectrometer and femtosecond X-ray pulses with an individual dose of up to >100 MGy. The spectra were found in agreement with undamaged spectra collected at low dose using synchrotron radiation. Our results demonstrate that the intact electronic structure of redox active transition metal compounds in different oxidation states can be characterized with this shot-by-shot method. This opens the door for studying the chemical dynamics of metal catalytic sites by following reactions under functional conditions. The technique can be combined with X-ray diffraction to simultaneously obtain the geometric structure of the overall protein and the local chemistry of active metal sites and is expected to prove valuable for understanding the mechanism of important metalloproteins, such as photosystem II.

Alonso-Mori, Roberto; Kern, Jan; Gildea, Richard J.; Sokaras, Dimosthenis; Weng, Tsu-Chien; Lassalle-Kaiser, Benedikt; Tran, Rosalie; Hattne, Johan; Laksmono, Hartawan; Hellmich, Julia; Glockner, Carina; Echols, Nathaniel; Sierra, Raymond G.; Schafer, Donald W.; Sellberg, Jonas; Kenney, Christopher; Herbst, Ryan; Pines, Jack; Hart, Philip; Herrmann, Sven; Grosse-Kunstleve, Ralf W.; Latimer, Matthew J.; Fry, Alan R.; Messerschmidt, Marc M.; Miahnahri, Alan; Seibert, M. Marvin; Zwart, Petrus H.; White, William E.; Adams, Paul D.; Bogan, Michael J.; Boutet, Sebastien; Williams, Garth J.; Zouni, Athina; Messinger, Johannes; Glatzel, Pieter; Sauter, Nicholas K.; Yachandra, Vittal K.; Yano, Junko; Bergmann, Uwe

2012-01-01

350

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

NASA Astrophysics Data System (ADS)

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 well as applications in environmental and medical fields.

Hall, Gene S.; Navon, Eliahu

1986-04-01

351

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

352

Coordination of aluminum atoms in anodic aluminum oxides, based on ultrasoft x-ray emission spectroscopy  

Microsoft Academic Search

Results are given of the investigation of the coordination of aluminum atoms in seven types of porous anodic aluminum oxides by ultrasoft x-ray emission spectroscopy. It is shown that a difference exists between the anodic aluminum oxides obtained in different electrolytes. The change in the relative intensity of the maxima of the Al L\\/sub 2,3\\/ emission band was used to

M. A. Chernykh; V. T. Belov; V. A. Terekhov; N. A. Amirova

1988-01-01

353

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

354

Search for X-ray line emission from A0620-00  

NASA Technical Reports Server (NTRS)

Measurements of the X-ray spectrum (1.85-7 keV) of A0620-00 obtained on 1975 October 17 and 1976 January 1-9 with the graphite crystal spectrometer on OSO-8 show a smooth continuum with an absence of emission lines. Upper limits are given for line emission from Si and S ions and are used to establish that the source is not optically thin. The results support a dense plasma model.

Kestenbaum, H. L.; Cohen, G. G.; Long, K. S.; Novick, R.; Silver, E. H.; Weisskopf, M. C.; Wolff, R. S.

1976-01-01

355

The Origin of T Tauri X-Ray Emission: New Insights from the Chandra Orion Ultradeep Project  

NASA Astrophysics Data System (ADS)

The Chandra Orion Ultradeep Project (COUP) provides the most comprehensive data set ever acquired on the X-ray emission of pre-main-sequence stars. In this paper, we study the nearly 600 X-ray sources that can be reliably identified with optically well-characterized T Tauri stars (TTSs) in the Orion Nebula Cluster. With a detection limit of LX,min~1027.3 ergs s-1 for lightly absorbed sources, we detect X-ray emission from more than 97% of the optically visible late-type (spectral types F-M) cluster stars. This proves that there is no ``X-ray-quiet'' population of late-type stars with suppressed magnetic activity. We use this exceptional optical, infrared, and X-ray data set to study the dependencies of the X-ray properties on other stellar parameters. All TTSs with known rotation periods lie in the saturated or supersaturated regime of the relation between activity and Rossby numbers seen for main-sequence (MS) stars, but the TTSs show a much larger scatter in X-ray activity than that seen for the MS stars. Strong near-linear relations between X-ray luminosities, bolometric luminosities, and mass are present. We also find that the fractional X-ray luminosity LX/Lbol rises slowly with mass over the 0.1-2 Msolar range. The plasma temperatures determined from the X-ray spectra of the TTSs are much hotter than in MS stars but seem to follow a general solar-stellar correlation between plasma temperature and activity level. The scatter about the relations between X-ray activity and stellar parameters is larger than the expected effects of X-ray variability, uncertainties in the variables, and unresolved binaries. This large scatter seems to be related to the influence of accretion on the X-ray emission. While the X-ray activity of the nonaccreting TTSs is consistent with that of rapidly rotating MS stars, the accreting stars are less X-ray active (by a factor of ~2-3 on average) and produce much less well-defined correlations than the nonaccretors. We discuss possible reasons for the suppression of X-ray emission by accretion and the implications of our findings on long-standing questions related to the origin of the X-ray emission from young stars, considering in particular the location of the X-ray-emitting structures and inferences for pre-main-sequence magnetic dynamos.

Preibisch, Thomas; Kim, Yong-Cheol; Favata, Fabio; Feigelson, Eric D.; Flaccomio, Ettore; Getman, Konstantin; Micela, Giusi; Sciortino, Salvatore; Stassun, Keivan; Stelzer, Beate; Zinnecker, Hans

2005-10-01

356

MAXI GSC detection of an enhanced X-ray emission from Anomalous X-ray Pulsar 4U 0142+61  

NASA Astrophysics Data System (ADS)

The MAXI/GSC detected an enhanced X-ray emission from a position consistent with 4U 0142+61 during the scan transit of 53 seconds centered at 2011-07-29 11:23:15 (UT). The scan started 214 seconds later than the Swift/BAT trigger of a short burst from this source (GCN 12209). The GSC light curve during the scan transit showed no significant spiky structure and the averaged X-ray flux was 69 +- 16 mCrab in the 4-10 keV band.

Morii, M.; Tomida, H.; Mihara, T.; Sugizaki, M.; Serino, M.; Nakahira, S.; Yamamoto, T.; Sootome, T.; Matsuoka, M.; Ueno, S.; Kohama, M.; Ishikawa, M.; Kawai, N.; Sugimori, K.; Usui, R.; Toizumi, T.; Yoshida, A.; Yamaoka, K.; Tsunemi, H.; Kimura, M.; Kitayama, H.; Negoro, H.; Nakajima, M.; Suwa, F.; Ueda, Y.; Hiroi, K.; Shidatsu, M.; Tsuboi, Y.; Matsumura, T.; Yamazaki, K.

2011-08-01

357

Implications of heavy-ion-induced satellite X-ray emission V Fine structure of the sulfur K X-ray satellite peaks  

NASA Astrophysics Data System (ADS)

We have studied K ? X-ray emission induced by 34 MeV 35Cl ions from several compounds at the ORNL EN Tandem Van de Graaff with a high-throughput, high-resolution Bragg crystal spectrometer in the Van Hamos geometry. The X-rays are diffracted off a cylindrically curved, highly reflective quartz crystal and detected with a position-sensitive proportional counter. The resolution of the spectrometer was better than one part in 2000. The data show remarkable and distinct fine structure in the individual KL n satellite peaks. Such data should aid in eventual comparisons with structures predicted by theoretical transition energy and intensity calculations.

Raman, S.; Källne, E.; Källne, J.; Nakajima, T.; Nestor, C. W.; Stelson, P. H.; Vane, C. R.; Walkiewicz, T. A.

1984-04-01

358

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

359

0.5 to 6 MeV Ar Ion Induced X-Ray Emission in View to Analytical Application.  

National Technical Information Service (NTIS)

A study of the X-ray emission induced by 0.5 to 6 MeV Ar ions has been realized in view of multielemental analytical applications. The historical development of the use of heavy ion induced X-ray emission in analysis and the theoretical background of inne...

M. D. Tenorio Castilleros

1979-01-01

360

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

361

A thin diffuse component of the Galactic ridge X-ray emission and heating of the interstellar medium contributed by the radiation of Galactic X-ray binaries  

NASA Astrophysics Data System (ADS)

We predict a thin diffuse component of the Galactic ridge X-ray emission (GRXE) arising from the scattering of the radiation of bright X-ray binaries (XBs) by the interstellar medium. This scattered component has the same scale height as that of the gaseous disk (~80 pc) and is therefore thinner than the GRXE of stellar origin (scale height ~130 pc). The morphology of the scattered component is furthermore expected to trace the clumpy molecular and HI clouds. We calculate this contribution to the GRXE from known Galactic XBs assuming that they are all persistent. The known XBs sample is incomplete, however, because it is flux limited and spans the lifetime of X-ray astronomy (~50 years), which is very short compared with the characteristic time of 1000-10 000 years that would have contributed to the diffuse emission observed today due to time delays. We therefore also use a simulated sample of sources, to estimate the diffuse emission we should expect in an optimistic case assuming that the X-ray luminosity of our Galaxy is on average similar to that of other galaxies. In the calculations we also take into account the enhancement of the total scattering cross-section due to coherence effects in the elastic scattering from multi-electron atoms and molecules. This scattered emission can be distinguished from the contribution of low X-ray luminosity stars by the presence of narrow fluorescent K-? lines of Fe, Si, and other abundant elements present in the interstellar medium and by directly resolving the contribution of low X-ray luminosity stars. We find that within 1° latitude of the Galactic plane the scattered emission contributes on average 10 - 30% of the GRXE flux in the case of known sources and over 50% in the case of simulated sources. In the latter case, the scattered component is found to even dominate the stellar emission in certain parts of the Galactic plane. X-rays with energies ?1 keV from XBs should also penetrate deep inside the HI and molecular clouds, where they are absorbed and heat the interstellar medium. We find that this heating rate dominates the heating by cosmic rays (assuming a solar neighborhood energy density) in a considerable part of the Galaxy. Appendices are available in electronic form at http://www.aanda.org

Molaro, Margherita; Khatri, Rishi; Sunyaev, Rashid A.

2014-04-01

362

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

363

A computational study of x-ray emission from high-Z x-ray sources on the National Ignition Facility laser  

NASA Astrophysics Data System (ADS)

We have begun to use 350-500 kJ of 1/3-micron laser light from the National Ignition Facility (NIF) laser to create millimeter-scale, bright multi-keV x-ray sources. In the first set of shots we achieved 15%-18% x-ray conversion efficiency into Xe M-shell (˜1.5-2.5 keV), Ar K-shell (˜3 keV) and Xe L-shell (˜4-5.5 keV) emission (Fournier et al., Phys. Plasmas 17, 082701, 2010), in good agreement with the emission modeled using a 2D radiation-hydrodynamics code incorporating a modern Detailed Configuration Accounting atomic model in non-LTE (Colvin et al., Phys. Plasmas, 17, 073111, 2010). In this paper we first briefly review details of the computational model and comparisons of the simulations with the Ar/Xe NIF data. We then discuss a computational study showing sensitivity of the x-ray emission to various beam illumination details (beam configuration, pointing, peak power, pulse shape, etc.) and target parameters (size, initial density, etc.), and finally make some predictions of how the x-ray conversion efficiency expected from NIF shots scales with atomic number of the emitting plasma.

Colvin, Jeffrey D.; Fournier, Kevin B.; Kane, Jave; Langer, Steven; May, Mark J.; Scott, Howard A.

2011-12-01

364

A Computational Study of X-ray Emissions from High-Z X-ray Sources on the National Ignition Facility Laser  

NASA Astrophysics Data System (ADS)

We have begun to use 350-500 kJ of 1/3-micron laser light from the National Ignition Facility (NIF) laser to create millimeter-scale, bright multi-keV x-ray sources. In the first set of shots we achieved 15% -18% x-ray conversion efficiency into Xe M-shell (˜1.5-2.5 keV), Ar K-shell (˜3 keV) and Xe L-shell (˜4-5.5 keV) emission (Fournier et al., Phys. Plasmas July 2010), in good agreement with the emission modeled using a 2D radiation-hydrodynamics code incorporating a modern Detailed Configuration Accounting atomic model in non-LTE (Colvin et al., Phys. Plasmas, July 2010). In this presentation we first briefly review details of the computational model and comparisons of the simulations with the Ar/Xe NIF data. We then discuss a computational study showing sensitivity of the x-ray emission to various beam illumination details (beam configuration, pointing, peak power, pulse shape, etc.) and target parameters (size, initial density, etc.), and finally make some predictions of how the x-ray conversion efficiency expected from NIF shots scales with atomic number of the emitting plasma.

Colvin, Jeffrey; Fournier, Kevin; Kane, Jave; May, Mark

2010-11-01

365

Evidence for Elevated X-Ray Emission in Local Lyman Break Galaxy Analogs  

NASA Astrophysics Data System (ADS)

Our knowledge of how X-ray emission scales with star formation at the earliest times in the universe relies on studies of very distant Lyman break galaxies (LBGs). In this paper, we study the relationship between the 2-10 keV X-ray luminosity (L X), assumed to originate from X-ray binaries (XRBs), and star formation rate (SFR) in ultraviolet (UV) selected z < 0.1 Lyman break analogs (LBAs). We present Chandra observations for four new Galaxy Evolution Explorer selected LBAs. Including previously studied LBAs, Haro 11 and VV 114, we find that LBAs demonstrate L X/SFR ratios that are elevated by ~1.5? compared to local galaxies, similar to the ratios found for stacked LBGs in the early universe (z > 2). Unlike some of the composite LBAs studied previously, we show that these LBAs are unlikely to harbor active galactic nuclei, based on their optical and X-ray spectra and the spatial distribution of the X-rays in three spatially extended cases. Instead, we expect that high-mass X-ray binaries (HMXBs) dominate the X-ray emission in these galaxies, based on their high specific SFRs (sSFRs ? SFR/M sstarf >= 10-9 yr-1), which suggest the prevalence of young stellar populations. Since both UV-selected populations (LBGs and LBAs) have lower dust attenuations and metallicities compared to similar samples of more typical local galaxies, we investigate the effects of dust extinction and metallicity on the L X/SFR for the broader population of galaxies with high sSFRs (>10-10 yr-1). The estimated dust extinctions (corresponding to column densities of N H < 1022 cm-2) are expected to have insignificant effects on observed L X/SFR ratio for the majority of galaxy samples. We find that the observed relationship between L X/SFR and metallicity appears consistent with theoretical expectations from XRB population synthesis models. Therefore, we conclude that lower metallicities, related to more luminous HMXBs such as ultraluminous X-ray sources, drive the elevated L X/SFR observed in our sample of z < 0.1 LBAs. The relatively metal-poor, active mode of star formation in LBAs and distant z > 2 LBGs may yield higher total HMXB luminosity than found in typical galaxies in the local universe.

Basu-Zych, Antara R.; Lehmer, Bret D.; Hornschemeier, Ann E.; Gonçalves, Thiago S.; Fragos, Tassos; Heckman, Timothy M.; Overzier, Roderik A.; Ptak, Andrew F.; Schiminovich, David

2013-09-01

366

EVIDENCE FOR ELEVATED X-RAY EMISSION IN LOCAL LYMAN BREAK GALAXY ANALOGS  

SciTech Connect

Our knowledge of how X-ray emission scales with star formation at the earliest times in the universe relies on studies of very distant Lyman break galaxies (LBGs). In this paper, we study the relationship between the 2-10 keV X-ray luminosity (L{sub X}), assumed to originate from X-ray binaries (XRBs), and star formation rate (SFR) in ultraviolet (UV) selected z < 0.1 Lyman break analogs (LBAs). We present Chandra observations for four new Galaxy Evolution Explorer selected LBAs. Including previously studied LBAs, Haro 11 and VV 114, we find that LBAs demonstrate L{sub X}/SFR ratios that are elevated by {approx}1.5{sigma} compared to local galaxies, similar to the ratios found for stacked LBGs in the early universe (z > 2). Unlike some of the composite LBAs studied previously, we show that these LBAs are unlikely to harbor active galactic nuclei, based on their optical and X-ray spectra and the spatial distribution of the X-rays in three spatially extended cases. Instead, we expect that high-mass X-ray binaries (HMXBs) dominate the X-ray emission in these galaxies, based on their high specific SFRs (sSFRs {identical_to} SFR/M{sub *} {>=} 10{sup -9} yr{sup -1}), which suggest the prevalence of young stellar populations. Since both UV-selected populations (LBGs and LBAs) have lower dust attenuations and metallicities compared to similar samples of more typical local galaxies, we investigate the effects of dust extinction and metallicity on the L{sub X}/SFR for the broader population of galaxies with high sSFRs (>10{sup -10} yr{sup -1}). The estimated dust extinctions (corresponding to column densities of N{sub H} < 10{sup 22} cm{sup -2}) are expected to have insignificant effects on observed L{sub X}/SFR ratio for the majority of galaxy samples. We find that the observed relationship between L{sub X}/SFR and metallicity appears consistent with theoretical expectations from XRB population synthesis models. Therefore, we conclude that lower metallicities, related to more luminous HMXBs such as ultraluminous X-ray sources, drive the elevated L{sub X}/SFR observed in our sample of z < 0.1 LBAs. The relatively metal-poor, active mode of star formation in LBAs and distant z > 2 LBGs may yield higher total HMXB luminosity than found in typical galaxies in the local universe.

Basu-Zych, Antara R.; Lehmer, Bret D.; Hornschemeier, Ann E.; Ptak, Andrew F. [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States); Goncalves, Thiago S. [Observatorio do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antonio 43, Saude, Rio de Janeiro-RJ, CEP 22240-060 (Brazil); Fragos, Tassos [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Heckman, Timothy M. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Overzier, Roderik A. [Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712 (United States); Schiminovich, David, E-mail: antara.r.basu-zych@nasa.gov [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)

2013-09-10

367

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

368

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

369

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

370

X-ray emission from an adolescent classical T Tauri star  

NASA Astrophysics Data System (ADS)

We propose to perform high-resolution X-ray spectroscopy of MP Muscae, a classical T Tauri star with an age of about 10 Myr, and hence quite old for its class. In fact, MP Mus is the only known star of this age with evidence of an accretion disk, found in a survey of the Lower Centaurus-Crux subgroup in the Scorpius- Centaurus association. Moreover, this star also shows evidence of a cold dusty disk, as indicated by excess emission at IR and mm wavelengths. The proposed observation will allow us to address several issues concerning the evolution of the X-ray emission in pre-main-sequence stars, the mechanism(s) of such emission, the element abundances of the emitting plasma, and the influence of high-energy radiation on the surrounding medium where planetary formation is likely occurring.

Maggio, Antonio

2005-10-01

371

Enhanced x-ray emissions from Au-Gd mixture targets ablated by a high-power nanosecond laser  

NASA Astrophysics Data System (ADS)

As an important x-ray source, enhancement of x-ray emissions from laser-produced plasmas is imperative for various applications. High-Z Au-Gd mixture targets are proposed to enhance the laser to x-ray conversion efficiency compared to pure Au target. In the experiments, a 1 ns frequency-tripled (351 nm wavelength) laser light was used to obtain an intensity of 3×10 W/cm2 on the targets. The x-ray spectra, total absolute x-ray emissions of all space, M-band fraction and backscattering from pure Au and Au-Gd mixture have been measured, respectively. It is shown that the absolute laser to x-ray conversion efficiency for the Au-Gd mixture containing 60% gold by atom is 47.7%, which has a 15% enhancement compared with that of the pure Au target. The experimental results are consistent with the radiation hydrodynamic simulations.

Dong, Yunsong; Shang, Wanli; Yang, Jiamin; Zhang, Lu; Zhang, Wenhai; Li, Zhichao; Guo, Liang; Zhan, Xiayu; Du, Huabing; Deng, Bo; Pu, Yikang

2014-01-01

372

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

NASA Technical Reports Server (NTRS)

During November 26-29,2003 XMM-Newton observed X-ray emissions from Jupiter for 69 hours. The 0.7-2.0 keV X-ray disk of Jupiter is observed to be brightest at the subsolar point, and limb darkening is seen in the 0.2-2.0 keV and 0.7-2.0 keV images. We present simultaneous lightcurves of Jovian equatorial X-rays and solar X-rays measured by the GOES, SOHO/SEM, and TIMED/SEE satellites. The solar X-ray flares occurring on the Jupiter-facing side of the Sun are matched by corresponding features in the Jovian X- rays. These results support the hypothesis that X-ray emissions from Jovian low-latitudes are solar X-rays scattered and fluoresced from the planet's upper atmosphere, and confirm that the Sun directly controls the non-auroral X-rays fiom Jupiter's disk. Our study suggest that Jovian equatorial X-rays; during certain Jupiter phase, can be used to predict the occurrence of solar flare on the hemisphere of the Sun that is invisible to space weather satellites.

Bhardwaj, Anil; Branduardi-Raymont, Graziella; Elsner, Ronald F.; Gladstone, G. Randall; Ramsay, G.; Rodriquez, P.; Soria, R.; Waite, J. Hunter, Jr.; Cravens, Thomas E.

2004-01-01

373

X-Ray Emission from Supernovae in Dense Circumstellar Matter Environments: A Search for Collisionless Shock  

NASA Technical Reports Server (NTRS)

The optical light curve of some supernovae (SNe) may be powered by the outward diffusion of the energy deposited by the explosion shock (so-called shock breakout) in optically thick (tau approx > 30) circumstellar matter (CSM). Recently, it was shown that the radiation-mediated and -dominated shock in an optically thick wind must transform into 8. collisionless shock and can produce hard X-rays. The X-rays are expected to peak at late times, relative to maximum visible light. Here we report on a search, using Swift-XRT and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense CSM. Our sample includes 19 type-IIn SNe, one type-Ibn SN and eiht hydrogen-poor super-luminous SNe (SLSN-I; SN 2005ap like). Two SNe (SN 2006jc and SN 2010jl) have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSl\\l. Therefore, we suggest that their optical light curves are powered by shock breakout in CSM. We show that two other events (SN 2010al and SN 2011ht) were too X-ray bright during the SN maximum optical light to be explained by the shock breakout model. We conclude that the light curves of some, but not all, type-IIn/Ibn SNe are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all the SLSN-I events, our X-ray limits are not deep enough and were typically obtained at too early times (i.e., near the SN maximum light) to conclude about their nature. Late time X-ray observations are required in order to further test if these SNe are indeed embedded in dense CSM. We review the conditions required for a shock breakOut in a wind profile. We argue that the time scale, relative to maximum light, for the SN to peak in X-rays is a probe of the column density and the density profile above the shock region. The optical light curves of SNe, for which the X-ray emission peaks at late times, are likely powered by the diffusion of shock energy from a dense CSM. We note that if the CSM density profile falls faster than a constant-rate wind density profile, then X-rays may escape at earlier times than estimated for the wind profile case. Furthermore, if the CSM have a region in which the density profile is very steep, relative to a steady wind density profile, or the CSM is neutral, then the radio free-free absorption may be low enough, and radio emission may be detected.

Ofek, E.O; Fox, D.; Cenko, B.; Sullivan, M.; Gnat, O.; Frail A.; Horesh, A.; Corsi, A; Quimby, R. M.; Gehrels, N.; Kulkarni, S. R.; Gal-Yam, A.; Nugent, P. E.; Yaron, O.; Filippenko, A. V.; Kasliwal, M. M.; Bildsten, L.; Bloom, J. S.; Poznanski, D; Arcavi, L.; Laher, R. R.; Levitan, D.; Sesar, B.; Surace, J.

2012-01-01

374

Suzaku Observations of the Diffuse X-Ray Emission across the Fermi Bubbles' Edges  

NASA Astrophysics Data System (ADS)

We present Suzaku X-ray observations along two edge regions of the Fermi Bubbles, with eight ~= 20 ks pointings across the northern part of the North Polar Spur (NPS) surrounding the north bubble and six across the southernmost edge of the south bubble. After removing compact X-ray features, diffuse X-ray emission is clearly detected and is well reproduced by a three-component spectral model consisting of unabsorbed thermal emission (temperature kT ~= 0.1 keV) from the Local Bubble, absorbed kT ~= 0.3 keV thermal emission related to the NPS and/or Galactic halo (GH), and a power-law component at a level consistent with the cosmic X-ray background. The emission measure (EM) of the 0.3 keV plasma decreases by ~= 50% toward the inner regions of the northeast bubble, with no accompanying temperature change. However, such a jump in the EM is not clearly seen in the south bubble data. While it is unclear whether the NPS originates from a nearby supernova remnant or is related to previous activity within or around the Galactic center, our Suzaku observations provide evidence that suggests the latter scenario. In the latter framework, the presence of a large amount of neutral matter absorbing the X-ray emission as well as the existence of the kT ~= 0.3 keV gas can be naturally interpreted as a weak shock driven by the bubbles' expansion in the surrounding medium, with velocity v exp ~ 300 km s-1 (corresponding to shock Mach number {M} \\simeq 1.5), compressing the GH gas to form the NPS feature. We also derived an upper limit for any non-thermal X-ray emission component associated with the bubbles and demonstrate that, in agreement with the aforementioned findings, the non-thermal pressure and energy estimated from a one-zone leptonic model of its broadband spectrum, are in rough equilibrium with that of the surrounding thermal plasma.

Kataoka, J.; Tahara, M.; Totani, T.; Sofue, Y.; Stawarz, ?.; Takahashi, Y.; Takeuchi, Y.; Tsunemi, H.; Kimura, M.; Takei, Y.; Cheung, C. C.; Inoue, Y.; Nakamori, T.

2013-12-01

375

Sigma observations of hard X-ray and soft gamma-ray emission from X-ray binaries  

NASA Astrophysics Data System (ADS)

After more than two years of operation, the imaging gamma-ray SIGMA telescope has accumulated several days of observation toward well known X-ray binaries. Four bright sources falling in this category have been detected so far: the pulsar GX 1+4 near the center of our galaxy, the stellar wind accreting system 4U 1700-377, and the black hole candidates Cygnus X-1 and GX 339-4. Moreover, SIGMA has observed three transients sources, which turned out to be also hard X-ray sources: the burster KS 1731-260, Tra X-1, and the Musca Nova. The properties of these systems in the SIGMA domain will be reviewed and a spectral distinction between black holes and neutron stars will be sketched.

Laurent, P.; Claret, A.; Lebrun, F.; Paul, J.; Dennis, M.; Barret, D.; Bouchet, L.; Mandrou, P.; Sunyaev, R.; Churazov, E.

1993-12-01

376

Discovery of X-ray and Extreme Ultraviolet Emission from Comet C\\/Hyakutake 1996 B2  

Microsoft Academic Search

During its close approach to Earth, comet C\\/Hyakutake 1996 B2 was observed at extreme ultraviolet and x-ray wavelengths with the Rontgen X-ray Satellite and Rossi X-ray Timing Explorer. The emission morphology was symmetric with respect to a vector from the comet's nucleus toward the sun, but not symmetric around the direction of motion of the comet with respect to interplanetary

C. M. Lisse; K. Dennerl; J. Englhauser; M. Harden; F. E. Marshall; M. J. Mumma; R. Petre; J. P. Pye; M. J. Ricketts; J. Schmitt; J. Trumper; R. G. West

1996-01-01

377

DIFFUSE HARD X-RAY EMISSION IN STARBURST GALAXIES AS SYNCHROTRON FROM VERY HIGH ENERGY ELECTRONS  

SciTech Connect

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 {sup {+-}}) can contribute to this emission, because starbursts have strong magnetic fields. We consider three sources of e {sup {+-}} at these energies: (1) primary electrons directly accelerated by supernova remnants, (2) pionic secondary e {sup {+-}} created by inelastic collisions between cosmic ray (CR) protons and gas nuclei in the dense interstellar medium of starbursts, and (3) pair e {sup {+-}} produced between the interactions between 10 and 100 TeV {gamma}-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 {sup {+-}}. We compare these models to extant radio and GeV and TeV {gamma}-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 {approx}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 {sup -2.2} injection spectrum and a diffusive escape time of 10 Myr (E/3 GeV){sup -1/2} (h/100 pc). Neutrino observations by IceCube and TeV {gamma}-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 {sup {+-}} from sources like pulsars in starbursts, which could enhance the synchrotron X-ray emission further.

Lacki, Brian C. [Institute for Advanced Study, Princeton, NJ 08540 (United States)] [Institute for Advanced Study, Princeton, NJ 08540 (United States); Thompson, Todd A. [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States)] [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States)

2013-01-01

378

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  

NASA Astrophysics Data System (ADS)

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.; Nachtegaal, M.; de Boni, E.; Willimann, M.; Safonova, O.; Sa, J.; Smolentsev, G.; Szlachetko, M.; van Bokhoven, J. A.; Dousse, J.-Cl.; Hoszowska, J.; Kayser, Y.; Jagodzinski, P.; Bergamaschi, A.; Schmitt, B.; David, C.; Lücke, A.

2012-10-01

379

RS Ophiuchi in Quiescence: Why Is It X-ray Faint?  

NASA Technical Reports Server (NTRS)

The short interval between successive outbursts of RS Oph strongly suggests that it has a high mass white dwarf accreting at a high rate. This, in turn, suggests the possibility of prominent X-ray emission from RS Oph in quiescence. However, archival quiescent X-ray observations of RS Oph show it to be a modest soft X-ray source but not a strong 2-10 keV X-ray source. In this aspect, RS Oph differs markedly from T CrB. We speculate on the possible mechanisms that could significantly suppress the 2-10 keV X-ray emission in RS Oph.

Mukai, Koji

2007-01-01

380

A Suzaku Search for Nonthermal Emission at Hard X-Ray Energies in the Coma Cluster  

NASA Astrophysics Data System (ADS)

The brightest cluster radio halo known resides in the Coma cluster of galaxies. The relativistic electrons producing this diffuse synchrotron emission should also produce inverse Compton emission that becomes competitive with thermal emission from the intracluster medium (ICM) at hard X-ray energies. Thus far, claimed detections of this emission in Coma are controversial. We present a Suzaku HXD-PIN observation of the Coma cluster in order to nail down its nonthermal hard X-ray content. The contribution of thermal emission to the HXD-PIN spectrum is constrained by simultaneously fitting thermal and nonthermal models to it and a spatially equivalent spectrum derived from an XMM-Newton mosaic of the Coma field. We fail to find statistically significant evidence for nonthermal emission in the spectra which are better described by only a single- or multitemperature model for the ICM. Including systematic uncertainties, we derive a 90% upper limit on the flux of nonthermal emission of 6.0 × 10-12 erg s-1 cm-2 (20-80 keV, for ? = 2.0), which implies a lower limit on the cluster-averaged magnetic field of B>0.15 ?G. Our flux upper limit is 2.5 times lower than the detected nonthermal flux from RXTE and BeppoSAX. However, if the nonthermal hard X-ray emission in Coma is more spatially extended than the observed radio halo, the Suzaku HXD-PIN may miss some fraction of the emission. A detailed investigation indicates that ~50%-67% of the emission might go undetected, which could make our limit consistent with that of Rephaeli & Gruber and Fusco-Femiano et al. The thermal interpretation of the hard Coma spectrum is consistent with recent analyses of INTEGRAL and Swift data.

Wik, Daniel R.; Sarazin, Craig L.; Finoguenov, Alexis; Matsushita, Kyoko; Nakazawa, Kazuhiro; Clarke, Tracy E.

2009-05-01

381

Dynamics and X-ray emission of a galactic superwind interacting with disk and halo gas  

NASA Technical Reports Server (NTRS)

There is a general agreement that the conspicuous extranuclear X-ray, optical-line, and radio-contiuum emission of starbursts is associated with powerful galactic superwinds blowing from their centers. However, despite the significant advances in observational studies of superwinds, there is no consensus on the nature of the emitting material and even on the emission mechanisms themselves. This is to a great extent a consequence of a poor understanding of dynamical processes in the starburst superwind regions. To address this issue, we have conducted two-dimensional hydrodynamical simulations of galactic superwinds. While previous similar studies have used a single (disk) component to represent the ISM of the starburst galaxy, we analyze the interaction of the wind with a two-component disk-halo ambient interstellar medium and argue that this two-component representation is crucial for adequate modeling of starbursts. The emphasis of this study is on the geometry and structure of the wind region and the X-ray emission arising in the wind material and the shocked gas in the disk and the halo of the galaxy. The simulation results have shown that a clear-cut bipolar wind can easily develop under a range of very different conditions. On the other hand, a complex 'filamentary' structure associated with the entrained dense disk material is found to arise within the hot bubble blown out by the wind. The flow pattern within the bubble is dominated equally by the central biconic outflow and a system of whirling motions r elated to the origin and development of the 'filaments'. The filament parameters make them a good candidate for optical-emission-line filamentary gas observed in starburst halos. We find that the history of mass and energy deposition in the starburst region of the galaxy is crucial for wind dynamics. A 'mild' early wind, which arises as a result of the cumulative effect of stellar winds from massive stars, produces a bipolar vertical cavity in the disk and halo gas without strongly affecting the gaseous disk, thus creating conditions for virtually free vertical escape of the hot gas at the later, much more violent supernova-dominated phases of the starburst. We calculate the luminosity, mass, and effective temperature of the X-ray emitting gas in the 'soft' (0.1 to 0.7 keV, 0.7 to 2.2 keV, and 0.1 to 2.2 keV) and 'hard' (1.6 to 8.3 keV) energy bands and estimate the contribution of different gaseous components to the X-ray flux in these bands. Analysis of these parameters enables us to make conclusions regarding the nature of the X-ray-emitting material. We have inferred that the bulk of the soft thermal X-ray emission from starbursts arises in the wind-shocked material of the disk and halo gas rather than in the wind material itself. This enables us to predict that the integrated soft X-ray spectra of starbursts need not show an overabundance of heavy elements which are believed to be produced copiously in the centers of starbursts. Unlike soft X-ray emission, the hard component of thermal X-ray emission is found to originate in the wind material ejected from the starburst region. However, the derived ratio of hard-to-soft X-ray luminosities is too small compared to that observed in starbursts. We conclude therefore that the observed hard X-ray emission of starbursts is probably not associated with the thermal emission of hot wind or ambient shocked gas. Typical temperatures of the bulk of the soft X-ray-emitting material in our very different models have been found to agree well with the ones estimated on the basis of the ROSAT data for the soft component of X-ray emission of nearby starbursts. We predict that temperatures of the extranuclear soft X-ray-emitting gas in starburst galaxies with heavy element abundances near solar should be close to T(sub Xs = 2 to 5 x 10(exp 6)K.

Suchkov, Anatoly A.; Balsara, Dinshaw S.; Heckman, Timothy M.; Leitherner, Claus

1994-01-01

382

Dynamics and X-ray emission of a galactic superwind interacting with disk and halo gas  

NASA Astrophysics Data System (ADS)

There is a general agreement that the conspicuous extranuclear X-ray, optical-line, and radio-contiuum emission of starbursts is associated with powerful galactic superwinds blowing from their centers. However, despite the significant advances in observational studies of superwinds, there is no consensus on the nature of the emitting material and even on the emission mechanisms themselves. This is to a great extent a consequence of a poor understanding of dynamical processes in the starburst superwind regions. To address this issue, we have conducted two-dimensional hydrodynamical simulations of galactic superwinds. While previous similar studies have used a single (disk) component to represent the ISM of the starburst galaxy, we analyze the interaction of the wind with a two-component disk-halo ambient interstellar medium and argue that this two-component representation is crucial for adequate modeling of starbursts. The emphasis of this study is on the geometry and structure of the wind region and the X-ray emission arising in the wind material and the shocked gas in the disk and the halo of the galaxy. The simulation results have shown that a clear-cut bipolar wind can easily develop under a range of very different conditions. On the other hand, a complex 'filamentary' structure associated with the entrained dense disk material is found to arise within the hot bubble blown out by the wind. The flow pattern within the bubble is dominated equally by the central biconic outflow and a system of whirling motions r elated to the origin and development of the 'filaments'. The filament parameters make them a good candidate for optical-emission-line filamentary gas observed in starburst halos. We find that the history of mass and energy deposition in the starburst region of the galaxy is crucial for wind dynamics. A 'mild' early wind, which arises as a result of the cumulative effect of stellar winds from massive stars, produces a bipolar vertical cavity in the disk and halo gas without strongly affecting the gaseous disk, thus creating conditions for virtually free vertical escape of the hot gas at the later, much more violent supernova-dominated phases of the starburst. We calculate the luminosity, mass, and effective temperature of the X-ray emitting gas in the 'soft' (0.1 to 0.7 keV, 0.7 to 2.2 keV, and 0.1 to 2.2 keV) and 'hard' (1.6 to 8.3 keV) energy bands and estimate the contribution of different gaseous components to the X-ray flux in these bands. Analysis of these parameters enables us to make conclusions regarding the nature of the X-ray-emitting material. We have inferred that the bulk of the soft thermal X-ray emission from starbursts arises in the wind-shocked material of the disk and halo gas rather than in the wind material itself. This enables us to predict that the integrated soft X-ray spectra of starbursts need not show an overabundance of heavy elements which are believed to be produced copiously in the centers of starbursts. Unlike soft X-ray emission, the hard component of