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Sample records for high-energy emission mechanisms

  1. THE SYNCHROTRON EMISSION MECHANISM IN THE RECENTLY DETECTED VERY HIGH ENERGY RADIATION FROM THE CRAB PULSAR

    SciTech Connect

    George, Machabeli; Zaza, Osmanov E-mail: z.osmanov@astro-ge.org

    2009-08-01

    Interpretation of the recently discovered very high energy (VHE) pulsed emission from the Crab pulsar is presented. By taking into account the fact that Crab pulsar's radiation for the optical and VHE spectrum peak at the same phases, we argue that the source of this broadband emission is spatially localized. It is shown that the only mechanism providing the results of the MAGIC Cherenkov telescope should be synchrotron radiation. We find that in the magnetospheric electron-positron plasma, due to the cyclotron instability, the pitch angle becomes non-vanishing, which leads to an efficient synchrotron mechanism, intensifying on the light cylinder length scales. We also estimate the VHE radiation spectral index to be equal to -1/2.

  2. Studies on High Energy Radiation Mechanisms and Gamma-Ray Burst Prompt Emissions

    NASA Astrophysics Data System (ADS)

    Zhang, B.

    2014-07-01

    Gamma-Ray Bursts (GRBs) are the most violent high-energy explosion in the universe. They are randomly happened, pulse-like phenomena with short durations. Since its discovery in 1960's by Vela satellite, GRBs have become a hot topic for astrophysical research. In 1997 the BeppoSAX satellite discovered afterglows of GRBs, and then helped to measure GRB redshifts. Thus it was found that GRBs are the events occurred at cosmological distances. Now it is widely accepted that the long bursts with durations longer than 2 s are from the collapsing massive stars, while the short bursts with durations less than 2 s are results of the merging compact binaries. By studying GRBs, the physical processes in ultrarelativistic and very high energy conditions can be investigated, and the researches on other fields, including constraining the cosmological models, can also get helped. The goal of this thesis is to present some discussions on possible radiation mechanisms and prompt light curves of GRBs. Since radiation mechanisms and prompt emissions are related to GRB central engines directly, studying these topics can help us to get a better understanding of some properties of the central engine. In Chapter 1, we review the discovery and observations of GRBs, presenting major achievements from major GRB-monitoring satellites including Compton Gamma-ray Observatory, BeppoSAX satellite, Swift satellite, as well as the latest Fermi Gamma-ray Space Telescope. The multi-wavelength properties of prompt emission as well as afterglows of GRBs are also summarized in Chapter 1. In Chapter 2 the current GRB standard model is presented. According to standard model, a fireball is ejected by the central engine. The internal shock is produced by collisions between various shells with different velocities inside the fireball. The directional kinetic energy of the fireball is then converted to internal energy, and finally the non-thermal radiation (the prompt emission) is produced by internal shocks

  3. Studies on High Energy Radiation Mechanisms and Gamma-Ray Burst Prompt Emissions

    NASA Astrophysics Data System (ADS)

    Zhang, B.

    2014-07-01

    Gamma-Ray Bursts (GRBs) are the most violent high-energy explosion in the universe. They are randomly happened, pulse-like phenomena with short durations. Since its discovery in 1960's by Vela satellite, GRBs have become a hot topic for astrophysical research. In 1997 the BeppoSAX satellite discovered afterglows of GRBs, and then helped to measure GRB redshifts. Thus it was found that GRBs are the events occurred at cosmological distances. Now it is widely accepted that the long bursts with durations longer than 2 s are from the collapsing massive stars, while the short bursts with durations less than 2 s are results of the merging compact binaries. By studying GRBs, the physical processes in ultrarelativistic and very high energy conditions can be investigated, and the researches on other fields, including constraining the cosmological models, can also get helped. The goal of this thesis is to present some discussions on possible radiation mechanisms and prompt light curves of GRBs. Since radiation mechanisms and prompt emissions are related to GRB central engines directly, studying these topics can help us to get a better understanding of some properties of the central engine. In Chapter 1, we review the discovery and observations of GRBs, presenting major achievements from major GRB-monitoring satellites including Compton Gamma-ray Observatory, BeppoSAX satellite, Swift satellite, as well as the latest Fermi Gamma-ray Space Telescope. The multi-wavelength properties of prompt emission as well as afterglows of GRBs are also summarized in Chapter 1. In Chapter 2 the current GRB standard model is presented. According to standard model, a fireball is ejected by the central engine. The internal shock is produced by collisions between various shells with different velocities inside the fireball. The directional kinetic energy of the fireball is then converted to internal energy, and finally the non-thermal radiation (the prompt emission) is produced by internal shocks

  4. High energy photon emission from wakefields

    NASA Astrophysics Data System (ADS)

    Farinella, D. M.; Lau, C. K.; Zhang, X. M.; Koga, J. K.; Taimourzadeh, S.; Hwang, Y.; Abazajian, K.; Canac, N.; Ebisuzaki, T.; Taborek, P.; Tajima, T.

    2016-07-01

    Experimental evidence has accumulated to indicate that wakefield acceleration (WFA) accompanies intense and sometimes coherent emission of radiation such as from betatron radiation. The investigation of this issue has additional impetus nowadays because we are learning (1) there is an additional acceleration process of the ponderomotive acceleration; (2) WFA may become relevant in much higher density regimes; (3) WFA has been proposed as the mechanism for extreme high energy cosmic ray acceleration and gamma ray bursts for active galactic nuclei. These require us to closely examine the radiative mechanisms in WFA anew. We report studies of radiation from wakefield (self-injected betatron) and ponderomotive (laser field) mechanisms in scalings of the frequency and intensity of the driver, as well as the plasma density.

  5. High-energy emission from transients.

    PubMed

    Hinton, J A; Starling, R L C

    2013-06-13

    Cosmic explosions dissipate energy into their surroundings on a very wide range of time scales: producing shock waves and associated particle acceleration. The historical culprits for the acceleration of the bulk of Galactic cosmic rays are supernova remnants: explosions on approximately 10(4) year time scales. Increasingly, however, time-variable emission points to rapid and efficient particle acceleration in a range of different astrophysical systems. Gamma-ray bursts have the shortest time scales, with inferred bulk Lorentz factors of approximately 1000 and photons emitted beyond 100 GeV, but active galaxies, pulsar wind nebulae and colliding stellar winds are all now associated with time-variable emission at approximately teraelectron volt energies. Cosmic photons and neutrinos at these energies offer a powerful probe of the underlying physical mechanisms of cosmic explosions, and a tool for exploring fundamental physics with these systems. Here, we discuss the motivations for high-energy observations of transients, the current experimental situation, and the prospects for the next decade, with particular reference to the major next-generation high-energy observatory, the Cherenkov Telescope Array. PMID:23630380

  6. Emission Lines and the High Energy Continuum

    NASA Technical Reports Server (NTRS)

    Green, Paul

    1998-01-01

    Quasars show many striking relationships between line and continuum radiation whose origins remain a mystery. FeII, [OIII], Hbeta, and HeII emission line properties correlate with high energy continuum properties such as the relative strength of X-ray emission, and X-ray continuum slope. At the same time, the shape of the high energy continuum may vary with luminosity. An important tool for studying global properties of Quasi Stellar Objects (QSOs) is the co-addition of data for samples of QSOS. We use this to show that X-ray bright (XB) QSOs show stronger emission lines in general, but particularly from the narrow line region. The difference in the [OIII]/Hbeta ratio is particularly striking, and even more so when blended FeII emission is properly subtracted. Weaker narrow forbidden lines ([OII] and NeV) are enhanced by factors of 2 to 3 in both UV and optical XB composite spectra. The physical origin of these diverse and interrelated correlations has yet to be determined. Unfortunately, many physically informative trends intrinsic to QSOs may be masked by dispersion in the data due to either low signal-to-noise or variability. An important tool for studying global properties of QSOs is the co-addition of data for samples of QSOS. We use this to show that X-ray bright (XB) QSOs show stronger emission lines in general, but particularly from the narrow line region. The difference in the [OIII]/Hbeta ratio is particularly striking, and even more so when blended Fell emission is properly subtracted. Weaker narrow forbidden lines ([OII] and NeV) are enhanced by factors of 2 to 3 in both UV and optical XB composite spectra. We describe a large-scale effort now underway to probe these effects in large samples, using both data and analysis as homogeneous as possible. Using an HST FOS Atlas of QSO spectra, with primary comparison to ROSAT PSPC spectral constraints, we will model the Big Blue Bump, its relationship to luminosity and QSO type, and we will analyze and

  7. Gamma-ray burst high energy emission from internal shocks

    NASA Astrophysics Data System (ADS)

    Galli, A.; Guetta, D.

    2008-03-01

    Aims:In this paper we study synchrotron and synchrotron self Compton (SSC) emission from internal shocks (IS) during the prompt and X-ray flare phases of gamma-ray bursts (GRBs). The aim is to test the IS model for the flare emission and for whether GRBs can be GeV sources. Methods: We determine the parameters for which the IS model can account for the observed prompt and X-ray flares emission, and study the detectability of the high energy SSC emission by the AGILE and GLAST satellites. Results: We find that the detectability of the SSC emission during the prompt phase of GRBs improves for higher values of the fireball Lorentz factor Γ and of the temporal variability t_v. If IS is the mechanism responsible for the flare emission, and the Lorentz factor of the shells producing the flare is Γ 100, the flare light curves are expected to present some substructures with temporal variability tv = 10-100 ms which are much smaller than the average duration of flares, and similar to those observed during the prompt phase of GRBs. If one assumes lower Lorentz factors, such as Γ 10 div 25, then a larger temporal variability tv 40 s can also account for the observed flare properties. However in this case we predict that X-ray flares do not have a counterpart at very high energies (MeV-GeV). Conclusions: An investigation on the substructures of the X-ray flare light curves, and simultaneous X-ray and high energy observations, will allow us to corroborate the hypothesis that late IS are responsible for the X-ray flares.

  8. High-Energy Emission From Millisecond Pulsars

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Usov, Vladimir V.; Muslimov, Alex G.

    2004-01-01

    The X-ray and gamma-ray spectrum of rotation-powered millisecond pulsars is investigated in a model for acceleration and pair cascades on open field lines above the polar caps. Although these pulsars have low surface magnetic fields, their short periods allow them to have large magnetospheric potential drops, but the majority do not produce sufficient pairs to completely screen the accelerating electric field. In these sources, the primary and secondary electrons continue to accelerate to high altitude and their Lorentz factors are limited by curvature and synchrotron radiation reaction. The accelerating particles maintain high Lorentz factors and undergo cyclotron resonant absorption of radio emission, that produces and maintains a large pitch angle, resulting in a strong synchrotron component. The resulting spectra consist of several distinct components: curvature radiation from primary electrons dominating from 1 - 100 GeV, synchrotron radiation from primary and secondary electrons dominating up to about 100 MeV, and much weaker inverse-Compton radiation from primary electrons a t 0.1 - 1 TeV. We find that the relative size of these components depends on pulsar period, period derivative, and neutron star mass and radius with the level of the synchrotron component also depending sensitively on the radio emission properties. This model is successful in describing the observed X-ray and gamma-ray spectrum of PSR J0218+4232 as synchrotron radiation, peaking around 100 MeV and extending up to a turnover around several GeV. The predicted curvature radiation components from a number of millisecond pulsars, as well as the collective emission from the millisecond pulsars in globular clusters, should be detectable with AGILE and GLAST. We also discuss a hidden population of X-ray-quiet and radio-quiet millisecond pulsars which have evolved below the pair death line, some of which may be detectable by telescopes sensitive above 1 GeV. Subject headings: pulsars: general

  9. Theory of High Energy Emission in GRBs

    SciTech Connect

    Meszaros, Peter

    2007-05-01

    Gamma-ray bursts are thought to be capable of accelerating cosmic rays up to GZK energies Ep {approx} 1020 eV, leading to a flux at Earth comparable to that observed by large EAS arrays such as AUGER. Both leptonic, e.g. synchrotron and inverse Compton, as well as photomeson processes can lead to GeV-TeV gamma-rays measurable by GLAST, AGILE, or ACTs, providing useful probes of the burst physics and model parameters. Photomeson interactions also produce neutrinos at energies ranging from sub-TeV to EeV, which will be probed with forthcoming experiments such as IceCube, ANITA and KM3NeT. This would provide information about the fundamental interaction physics, the acceleration mechanism, the nature of the sources and their environment.

  10. High energy mechanism from the knot of OJ 287

    NASA Astrophysics Data System (ADS)

    Kushwaha, Pankaj; Sahayanathan, Sunder; Singh, K. P.

    The detection of gamma-ray flare from the BL Lac object, OJ 287 during October 2009 is associated with the ejection of a superluminal radio knot as suggested by discrete cross-correlation analysis of gamma-ray and 1 mm radio light curve. We study plausible mechanisms responsible for the high energy emission from this knot. We reproduce the quasi-simultaneous broadband spectral energy distribution from the knot considering synchrotron and inverse Compton emission from a broken power-law particle distribution. Explanation of X-ray and gamma-ray by either synchrotron-self Compton (SSC) or external Compton (EC) alone cannot reproduce the broadband spectrum and/or require unphysical set of parameters. Hence we model the high energy emission as an outcome of both SSC and EC models. The temperature of external photon field inferred from this model suggests that the gamma-ray emission must be resulting from the inverse Compton scattering of infra-red photon from the warm region surrounding the super massive black hole in OJ 287.

  11. CONSTRAINTS ON VERY HIGH ENERGY EMISSION FROM GRB 130427A

    SciTech Connect

    Aliu, E.; Errando, M.; Aune, T.; Barnacka, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Benbow, W.; Cerruti, M.; Berger, K.; Biteau, J.; Byrum, K.; Cardenzana, J. V; Dickinson, H. J.; Eisch, J. D.; Chen, X.; Ciupik, L.; Connaughton, V.; Cui, W.; Falcone, A. E-mail: sjzhu@umd.edu; and others

    2014-11-01

    Prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-Ray Space Telescope for ∼70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is also evidence that the high-energy emission may instead be an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations of GRB 130427A ∼71 ks (∼20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB 130427A for E > 100 GeV. The non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission from this burst.

  12. Dynamical Models for High-Energy Emission from Massive Stars

    NASA Astrophysics Data System (ADS)

    Owocki, Stanley %FAA(University of Delaware)

    Massive stars are prominent sources of X-rays and gamma-rays detected by both targeted and survey observations from orbiting telescopes like Chandra, XMM/Newton, RXTE, and Fermi. Such high-energy emissions represent key probes of the dynamics of massive-star mass loss, and their penetration through many magnitudes of visible interstellar extinction makes them effective beacons of massive stars in distant reaches of the Galaxy, and in young, active star-forming regions. The project proposed here will develop a comprehensive theoretical framework for interpreting both surveys and targeted observations of high-energy emission from massive stars. It will build on our team's extensive experience in both theoretical models and observational analyses for three key types of emission mechanisms in the stellar wind outflows of these stars, namely: 1) Embedded Wind Shocks (EWS) arising from internal instabilities in the wind driving; 2) shocks in Colliding Wind Binary (CWB) systems; and 3) High-Mass X-ray Binaries (HMXB) systems with interaction between massive-star wind with a compact companion (neutron star or black hole). Taking advantage of commonalities in the treatment of radiative driving, hydrodynamics, shock heating and cooling, and radiation transport, we will develop radiation hydrodynamical models for the key observational signatures like energy distribution, emission line spectrum, and variability, with an emphasis on how these can be used in affiliated analyses of both surveys like the recent Chandra mapping of the Carina association, and targeted observations of galactic X-ray and gamma-ray sources associated with each of the above specific model types. The promises of new clumping-insensitive diagnostics of mass loss rates, and the connection to mass transfer and binarity, all have broad relevance for understanding the origin, evolution, and fate of massive stars, in concert with elements of NASA's Strategic Subgoal 3D. Building on our team's expertise, the

  13. High-Energy Emission at Shocks in Millisecond Pulsar Binaries

    NASA Astrophysics Data System (ADS)

    Kust Harding, Alice; Wadiasingh, Zorawar; Venter, Christo; Boettcher, Markus

    2016-04-01

    A large number of new Black Widow (BW) and Redback (RB) energetic millisecond pulsars have been discovered through radio searches of unidentified Fermi sources, increasing the known number of these systems from 4 to 28. We model the high-energy emission components from particles accelerated to several TeV in intrabinary shocks in BW and RB systems, and their predicted modulation at the binary orbital period. Synchrotron emission is expected at X-ray energies and such modulated emission has already been detected by Chandra and XMM. Inverse Compton emission from accelerated particles scattering the UV emission from the radiated companion star is expected in the Fermi and TeV bands. Detections or constraints on this emission will probe the unknown physics of pulsar winds.

  14. High Energy Emission from Pulsar Magnetospheres and Winds

    NASA Astrophysics Data System (ADS)

    Spitkovsky, Anatoly

    Recent gamma-ray observations of pulsars and their nebulae suggest an important role played by magnetic reconnection in determining the structure of the magnetosphere and the wind and in the acceleration of particles that lead to the high energy emission. Strong current sheets that are susceptible to magnetic dissipation are found near the light cylinder of the pulsar and persist throughout the wind. This proposal investigates the processes that occur in these current sheets, and determines their structure and particle acceleration properties. A suite of relativistic MHD and particle-in-cell kinetic simulations will be used to obtain the global 3D geometry of the magnetosphere, flow geometry in the current sheet, and calculate the dissipation of the current both near the pulsar and in the termination shock of the pulsar wind. The results will be applied to modeling the beaming in pulsar gamma-ray light curves, and to understanding particle acceleration in broadband and flaring nebular emission.

  15. Spectral diagnostics of high energy emission in lambda Eri

    NASA Technical Reports Server (NTRS)

    Smith, Myron

    1995-01-01

    Multi-line observations of the optical spectrum of lambda Eri demonstrates that rapidly varying, low-velocity emissions occur in several He I lines even when H alpha shows no emission. A peculiar aspect of the He I emissions is that the ratio 5876/6678 is = 1. A theory of helium line formation generally admits two common emission mechanisms. The first is recombination/cascades, which is well known to give a ratio of greater than or equal to 3. The second is a non-LTE effect that occurs in hot (O-type) photospheres when resonance He I 584 radiation becomes transparent and drives single lines along into the emission. To accommodate a ratio of 5876/6678 = 1 may require that both processes sometimes operate at the same time, presumably in separate localities near the surface of this star.

  16. Resolving high energy emission of jets using strong gravitational lensing

    NASA Astrophysics Data System (ADS)

    Barnacka, Anna

    2014-11-01

    Chandra observations of M87 in 2004 uncovered an outburst originating in distant knot along the jet hundreds of parsecs from the core. This discovery challenges our understanding of the origin of high energy flares. Current technology is inadequate to resolve jets at distances greater than M87, or observed at higher energies. We propose to use gravitationally lensed jets to investigate the structure of more distant sources. Photons emitted at different sites cross the lens plane at different distances, thus magnification ratios and time delays differ between the mirage images. Monitoring of flares from lensed jets reveals the origin of the emission. With detectors like Chandra, lensed systems are a tool for resolving the structure of the jets and for investigating their cosmic evolution.

  17. The Slot Gap Model for Pulsar High-Energy Emission

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alexander

    2004-01-01

    A new picture of pulsar high-energy emission is proposed that is different from both the traditional polar cap and outer gap models, but combines elements of each. The slot gap model is based on electron acceleration along the edge of the open field region from the neutron star surface to near the light cylinder. Along the last open field line, the pair formation front rises to very high altitude forming a slot gap, where the accelerating electric field is unscreened by pairs. Electrons continue to accelerate to high altitudes in the slot gap, reaching a radiation reaction-limited energy of several TeV. The resulting radiation pattern features sharp caustics on the trailing edge of the open field region, allowing for the possibility of double-peaked pulse profiles very similar to those observed in gamma-ray pulsars. Since emission from a large range of altitudes arrives in phase, this model very naturally explains the phase alignment of radiation at all wavelengths from the Crab pulsar.

  18. The Prompt and High Energy Emission of Gamma Ray Bursts

    SciTech Connect

    Meszaros, P.

    2009-05-25

    I discuss some recent developments concerning the prompt emission of gamma-ray bursts, in particular the jet properties and radiation mechanisms, as exemplified by the naked-eye burst GRB 080319b, and the prompt X-ray emission of XRB080109/SN2008d, where the progenitor has, for the first time, been shown to contribute to the prompt emission. I discuss then some recent theoretical calculations of the GeV/TeV spectrum of GRB in the context of both leptonic SSC models and hadronic models. The recent observations by the Fermi satellite of GRB 080916C are then reviewed, and their implications for such models are discussed, together with its interesting determination of a bulk Lorentz factor, and the highest lower limit on the quantum gravity energy scale so far.

  19. High Energy Gamma-Ray Emission from Gamma-Ray Bursts - Before GLAST

    SciTech Connect

    Fan, Yi-Zhong; Piran, Tsvi

    2011-11-29

    Gamma-ray bursts (GRBs) are short and intense emission of soft {gamma}-rays, which have fascinated astronomers and astrophysicists since their unexpected discovery in 1960s. The X-ray/optical/radio afterglow observations confirm the cosmological origin of GRBs, support the fireball model, and imply a long-activity of the central engine. The high-energy {gamma}-ray emission (> 20 MeV) from GRBs is particularly important because they shed some lights on the radiation mechanisms and can help us to constrain the physical processes giving rise to the early afterglows. In this work, we review observational and theoretical studies of the high-energy emission from GRBs. Special attention is given to the expected high-energy emission signatures accompanying the canonical early-time X-ray afterglow that was observed by the Swift X-ray Telescope. We also discuss the detection prospect of the upcoming GLAST satellite and the current ground-based Cerenkov detectors.

  20. Evidence for Temporally-Extended, High-Energy Emission from Gamma Ray Burst 990104

    NASA Technical Reports Server (NTRS)

    Wren, D. N.; Bertsch, D. L.; Ritz, S.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    It is well known that high-energy emission (MeV - GeV) has been observed in several gamma ray bursts and temporally-extended emission from lower-energy gamma rays through radio wavelengths is well established. Observations of extended, high-energy emission are, however, scarce. Here we present evidence for a gamma ray burst emission that is both high-energy and extended, coincident with lower energy emissions. For the very bright and long burst, GRB 990104, we show light curves and spectra that confirm emission above 50 MeV, approximately 152 seconds after the BATSE (Burst and Transient Source Experiment) trigger and initial burst emission. Between the initial output and the main peak, seen at both low and high energy, there was a period of approx. 100 s during which the burst was relatively quiet. This burst was found as part of an ongoing search for high-energy emission in gamma ray bursts.

  1. Plasma simulations of emission line regions in high energy environments

    NASA Astrophysics Data System (ADS)

    Richardson, Chris T.

    constrain the spectral energy distribution, excitation mechanism, abundances and physical conditions present in these galaxies, while the large data set allows many weaker emission lines to be used as consistency checks. By integrating over a wide range of densities and radii from the excitation source, the variation in ionization for AGN can be represented as change in the central concentration of clouds in the NLR. Preliminary analysis from modeling star forming galaxies indicates that the same interpretation might apply to galaxies without an AGN in which gas is excited by starlight.

  2. High-energy gamma-ray emission from pion decay in a solar flare magnetic loop

    NASA Technical Reports Server (NTRS)

    Mandzhavidze, Natalie; Ramaty, Reuven

    1992-01-01

    The production of high-energy gamma rays resulting from pion decay in a solar flare magnetic loop is investigated. Magnetic mirroring, MHD pitch-angle scattering, and all of the relevant loss processes and photon production mechanisms are taken into account. The transport of both the primary ions and the secondary positrons resulting from the decay of the positive pions, as well as the transport of the produced gamma-ray emission are considered. The distributions of the gamma rays as a function of atmospheric depth, time, emission angle, and photon energy are calculated and the dependence of these distributions on the model parameters are studied. The obtained angular distributions are not sufficiently anisotropic to account for the observed limb brightening of the greater than 10 MeV flare emission, indicating that the bulk of this emission is bremsstrahlung from primary electrons.

  3. Very high energy emission of Crab-like pulsars driven by the Cherenkov drift radiation

    NASA Astrophysics Data System (ADS)

    Osmanov, Z.

    2016-02-01

    In this paper, we study the generation of very high energy (VHE) emission in Crab-like pulsars driven by means of the feedback of Cherenkov drift waves on distribution of magnetospheric electrons. We have found that the unstable Cherenkov drift modes lead to the quasi-linear diffusion, keeping the pitch angles from vanishing, which in turn, maintains the synchrotron mechanism. Considering the Crab-like pulsars it has been shown that the growth rate of the Cherenkov drift instability is quite high, indicating high efficiency of the process. Analysing the mechanism for the typical parameters we have found that the Cherenkov drift emission from the extreme UV to hard X-rays is strongly correlated with the VHE synchrotron emission in the GeV band.

  4. Hadronization Mechanisms and Spin Effects in High Energy Fragmentation Processes

    NASA Astrophysics Data System (ADS)

    Liang, Zuo-Tang

    2002-03-01

    Spin effects in high energy fragmentation processes can provide us with important information on hadronization mechanisms and spin structure of hadrons. It can in particular give new tests to the hadronization models. In this talk, we make a brief introduction to the different topics studied in this connection and a short summary of the available data. After that, we present a short summary of the main theoretical results we obtained in studying these different topics. The talk was mainly based on the publications [4-8] which have been finished in collaboration with C.Boros, Liu Chun-xiu and Xu Qing-hua.

  5. Accretion, jets and winds: High-energy emission from young stellar objects

    NASA Astrophysics Data System (ADS)

    Günther, H. M.

    2011-06-01

    This article summarizes the processes of high-energy emission in young stellar objects. Stars of spectral type A and B are called Herbig Ae/Be (HAeBe) stars in this stage, all later spectral types are termed classical T Tauri stars (CTTS). Both types are studied by high-resolution X-ray and UV spectroscopy and modeling. Three mechanisms contribute to the high-energy emission from CTTS: 1) CTTS have active coronae similar to main-sequence stars, 2) the accreted material passes through an accretion shock at the stellar surface, which heats it to a few MK, and 3) some CTTS drive powerful outflows. Shocks within these jets can heat the plasma to X-ray emitting temperatures. Coronae are already well characterized in the literature; for the latter two scenarios models are shown. The magnetic field suppresses motion perpendicular to the field lines in the accretion shock, thus justifying a 1D geometry. The radiative loss is calculated as optically thin emission. A mixture of shocked and coronal gas is fitted to X-ray observations of accreting CTTS. Specifically, the model explains the peculiar line-ratios in the He-like triplets of Ne IX and O VII. All stars require only small mass accretion rates to power the X-ray emission. In contrast, the HAeBe HD 163296 has line ratios similar to coronal sources, indicating that neither a high density nor a strong UV-field is present in the region of the X-ray emission. This could be caused by a shock in its jet. Similar emission is found in the deeply absorbed CTTS DG Tau. Shock velocities between 400 and 500 km s-1 are required to explain the observed spectrum. Doctoral Thesis Award Lecture 2010

  6. Fermi γ-ray Pulsars: Towards the Understanding of the Pulsed High-Energy Emission

    NASA Astrophysics Data System (ADS)

    Kalapotharakos, Constantinos; Kust Harding, Alice; Kazanas, Demosthenes; Brambilla, Gabriele

    2016-04-01

    Based on the Fermi observational data we reveal meaningful constraints for the dependence of the macroscopic parameters of dissipative pulsar magnetosphere models on the corresponding spin-down rate. Our models are specifications of the FIDO (Force-Free Inside, Dissipative Outside) model where the dissipative regions are outside the light-cylinder near the equatorial current sheet. These models provide not only the field geometry but also the necessary particle accelerating electric fields. Assuming emission due to curvature radiation, the FIDO models reproduce the observed light-curve phenomenology as depicted in the radio-lag vs peak-separation diagram obtained by Fermi. A direct and detailed comparison of the model spectral properties (cutoff energies and total γ-ray luminosities) with those observed by Fermi reveals the dependence of the macroscopic conductivity parameter on the spin-down rate providing a unique insight for the understanding of the physical mechanisms behind the high-energy emission in pulsar magnetospheres.

  7. High-energy emission processes in M87

    NASA Astrophysics Data System (ADS)

    de Jong, S.; Beckmann, V.; Soldi, S.; Tramacere, A.; Gros, A.

    2015-07-01

    We study the contribution of thermal and non-thermal processes to the inverse Compton emission of the radio galaxy M87 by modelling its broad-band emission. Through this we aim to derive insight into where within the AGN the X-ray, γ-ray and VHE emission is produced. We have analysed all available INTEGRAL IBIS/ISGRI (Imager on Board INTEGRAL Spacecraft/INTEGRAL Soft Gamma-Ray Imager) data on M87, spanning almost 10 years, to set an upper limit to the average hard X-ray flux of f(20-60 keV) ≲ 3 × 10-12 erg cm-2 s-1, using several techniques beyond the standard analysis which are also presented here. We also analysed hard X-ray data from Suzaku/PIN taken late 2006 November, and we report the first hard X-ray detection of M87 with a flux of f(20-60 keV) = 10-11 erg cm-2 s-1. In addition we analyse data from Fermi/Large Area Telescope, INTEGRAL/Joint European Monitor in X-rays, and Suzaku/X-ray Imaging Spectrometer. We collected historical radio/IR/optical and VHE data and combined them with the X-ray and γ-ray data, to create broad-band spectral energy distributions (SEDs) for the average low-flux state and the flaring state. The resulting SEDs are modelled by applying a single-zone SSC model with a jet angle of θ = 15°. We also show that modelling the core emission of M87 using a single-zone synchrotron self-Compton model does represent the SED, suggesting that the core emission is dominated by a BL Lac-type AGN core. Using SED modelling we also show that the hard X-ray emission detected in 2006 is likely due to a flare of the jet knot HST-1, rather than being related to the core.

  8. High Energy Emission in Pulsar Magnetospheres: Modeling in the FERMI Era

    NASA Astrophysics Data System (ADS)

    Kalapotharakos, Constantinos; Kust Harding, Alice; Kazanas, Demosthenes; Brambilla, Gabriele

    2016-01-01

    Our study of pulsar high-energy emission in dissipative pulsar magnetospheres provides meaningful constraints on the macroscopic parameters of the global pulsar magnetosphere solutions through the extensive comparison of model light curves and their spectra with those provided by multi-wavelength observations of real pulsars. These state-of-the-art solutions, by their nature, provide both the field geometry, and the necessary particle accelerating electric fields. Using these solutions, we generate model gamma-ray light curves by calculating the trajectories and the Lorentz factors of the radiating particles, under the influence of both the accelerating electric components and curvature radiation-reaction. I will show how this study leads to the construction of model magnetospheres that successfully reproduce the observed light-curve phenomenology as depicted in the radio-lag vs peak-separation diagram obtained by Fermi. These models allow the calculation of phase-averaged and phase-resolved spectra and the total gamma-ray luminosities as well. I will show that the corresponding photon cut-off energies and total gamma-ray luminosities are within the observed ranges for both standard and millisecond pulsars. A direct and detailed comparison with the Fermi data reveals the dependence of the macroscopic conductivity parameter on the spin down rate, constraining the physical mechanisms underlying the observed pulsar high-energy emission.

  9. High-energy emission of the first millisecond pulsar

    SciTech Connect

    Ng, C.-Y.; Takata, J.; Leung, G. C. K.; Cheng, K. S.; Philippopoulos, P.

    2014-06-01

    We report on X-ray and gamma-ray observations of the millisecond pulsar (MSP) B1937+21 taken with the Chandra X-ray Observatory, XMM-Newton, and the Fermi Large Area Telescope. The pulsar X-ray emission shows a purely non-thermal spectrum with a hard photon index of 0.9 ± 0.1, and is nearly 100% pulsed. We found no evidence of varying pulse profile with energy as previously claimed. We also analyzed 5.5 yr of Fermi survey data and obtained much improved constraints on the pulsar's timing and spectral properties in gamma-rays. The pulsed spectrum is adequately fitted by a simple power-law with a photon index of 2.38 ± 0.07. Both the gamma-ray and X-ray pulse profiles show similar two-peak structure and generally align with the radio peaks. We found that the aligned profiles and the hard spectrum in X-rays seem to be common properties among MSPs with high magnetic fields at the light cylinder. We discuss a possible physical scenario that could give rise to these features.

  10. High-energy Emission of the First Millisecond Pulsar

    NASA Astrophysics Data System (ADS)

    Ng, C.-Y.; Takata, J.; Leung, G. C. K.; Cheng, K. S.; Philippopoulos, P.

    2014-06-01

    We report on X-ray and gamma-ray observations of the millisecond pulsar (MSP) B1937+21 taken with the Chandra X-ray Observatory, XMM-Newton, and the Fermi Large Area Telescope. The pulsar X-ray emission shows a purely non-thermal spectrum with a hard photon index of 0.9 ± 0.1, and is nearly 100% pulsed. We found no evidence of varying pulse profile with energy as previously claimed. We also analyzed 5.5 yr of Fermi survey data and obtained much improved constraints on the pulsar's timing and spectral properties in gamma-rays. The pulsed spectrum is adequately fitted by a simple power-law with a photon index of 2.38 ± 0.07. Both the gamma-ray and X-ray pulse profiles show similar two-peak structure and generally align with the radio peaks. We found that the aligned profiles and the hard spectrum in X-rays seem to be common properties among MSPs with high magnetic fields at the light cylinder. We discuss a possible physical scenario that could give rise to these features.

  11. The Search for High Energy Extended Emission by Fermi-LAT from Swift-Localized Gamma-Ray Bursts

    SciTech Connect

    Chiang, J.; Racusin, J.L.; /NASA, Goddard

    2012-05-01

    The brighter Fermi-LAT bursts have exhibited emission at energies >0.1 GeV that persists as late as {approx}2 ks after the prompt phase has nominally ended. This so-called 'extended emission' could arise from continued activity of the prompt burst mechanism or it could be the start of a high energy afterglow component. The high energy extended emission seen by the LAT has typically followed a t{sup -}{gamma} power-law temporal decay where {gamma} {approx} 1.2-1.7 and has shown no strong indication of spectral evolution. In contrast, the prompt burst emission generally displays strong spectral variability and more complex temporal changes in the LAT band. This differing behavior suggests that the extended emission likely corresponds to an early afterglow phase produced by an external shock. In this study, we look for evidence of high energy extended emission from 145 Swift-localized GRBs that have occurred since the launch of Fermi. A majority of these bursts were either outside of the LAT field-of-view or were otherwise not detected by the LAT during the prompt phase. However, because of the scanning operation of the Fermi satellite, the long-lived extended emission of these bursts may be detectable in the LAT data on the {approx}few ks time scale. We will look for emission from individual bursts and will perform a stacking analysis in order to set bounds on this emission for the sample as a whole. The detection of such emission would have implications for afterglow models and for the overall energy budget of GRBs.

  12. Spatially resolving the very high energy emission from MGRO J2019+37 with VERITAS

    SciTech Connect

    Aliu, E.; Errando, M.; Aune, T.; Behera, B.; Chen, X.; Federici, S.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Benbow, W.; Cerruti, M.; Berger, K.; Bird, R.; Bouvier, A.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dumm, J.; Dwarkadas, V. V.; Falcone, A. E-mail: nahee@uchicago.edu; and others

    2014-06-10

    We present very high energy (VHE) imaging of MGRO J2019+37 obtained with the VERITAS observatory. The bright extended (∼2°) unidentified Milagro source is located toward the rich star formation region Cygnus-X. MGRO J2019+37 is resolved into two VERITAS sources. The faint, point-like source VER J2016+371 overlaps CTB 87, a filled-center remnant (SNR) with no evidence of a supernova remnant shell at the present time. Its spectrum is well fit in the 0.65-10 TeV energy range by a power-law model with photon index 2.3 ± 0.4. VER J2019+378 is a bright extended (∼1°) source that likely accounts for the bulk of the Milagro emission and is notably coincident with PSR J2021+3651 and the star formation region Sh 2–104. Its spectrum in the range 1-30 TeV is well fit with a power-law model of photon index 1.75 ± 0.3, among the hardest values measured in the VHE band, comparable to that observed near Vela-X. We explore the unusual spectrum and morphology in the radio and X-ray bands to constrain possible emission mechanisms for this source.

  13. Maser pulse emission mechanisms

    NASA Astrophysics Data System (ADS)

    Melrose, D. B.

    Polar cap models of coherent radio emission mechanisms in pulsars are reviewed, noting deficiencies present in models with curvature emission due to bunches and the possibilities of descriptions based on maser processes. The lack of a no-velocity dispersion theory of bunching radiation is noted to make assumptions based on uniform particle velocities questionable. Streaming instability-produced bunching is also subject to inaccuracy when the bunching occurs at distances of over one stellar radius, or when the growth velocity is insufficient. Conditions are defined for successful bunching through particle trapping by waves, and it is mentioned that models with this mechanism offer predictions which do not match data from observations. Similar objections are found with self-bunching, plasma emission, and klystron mechanisms. Maser-emission models are concluded to avoid the problems associated with differences between observed and predicted dispersion delays found in other types of models.

  14. Observation of solar high energy gamma and X-ray emission and solar energetic particles

    NASA Astrophysics Data System (ADS)

    Struminsky, A.; Gan, W.

    2015-08-01

    We considered 18 solar flares observed between June 2010 and July 2012, in which high energy >100 MeV γ-emission was registered by the Large Area Telescope (LAT) aboard FermiGRO. We examined for these γ-events soft X-ray observations by GOES, hard X-ray observations by the Anti-Coincidence Shield of the SPectrometer aboard INTEGRAL (ACS SPI) and the Gamma-Ray burst Monitor (GBM) aboard FermiGRO. Hard X-ray and π0-decay γ-ray emissions are used as tracers of electron and proton acceleration, respectively. Bursts of hard X-ray were observed by ACS SPI during impulsive phase of 13 events. Bursts of hard X- ray >100 keV were not found during time intervals, when prolonged hard y-emission was registered by LAT/FermiGRO. Those events showing prolonged high-energy gamma-ray emission not accompanied by >100 keV hard X-ray emission are interpreted as an indication of either different acceleration processes for protons and electrons or as the presence of a proton population accelerated during the impulsive phase of the flare and subsequently trapped by some magnetic structure. In-situ energetic particle measurements by GOES and STEREO (High Energy Telescope, HET) shows that five of these y-events were not accompanied by SEP events at 1 AU, even when multi-point measurements including STEREO are taken into account. Therefore accelerated protons are not always released into the heliosphere. A longer delay between the maximum temperature and the maximum emission measure characterises flares with prolonged high energy γ-emission and solar proton events.

  15. Very high energy emission as a probe of relativistic magnetic reconnection in pulsar winds

    NASA Astrophysics Data System (ADS)

    Mochol, Iwona; Pétri, Jérôme

    2015-04-01

    The population of gamma-ray pulsars, including Crab observed in the TeV range, and Vela detected above 50 GeV, challenges existing models of pulsed high-energy emission. Such models should be universally applicable, yet they should account for spectral differences among the pulsars. We show that the gamma-ray emission of Crab and Vela can be explained by synchrotron radiation from the current sheet of a striped wind, expanding with a modest Lorentz factor Γ ≲ 100 in the Crab case, and Γ ≲ 50 in the Vela case. In the Crab spectrum, a new synchrotron self-Compton component is expected to be detected by the upcoming experiment CTA. We suggest that the gamma-ray spectrum directly probes the physics of relativistic magnetic reconnection in the striped wind. In the most energetic pulsars, like Crab, with dot{E}_{38}^{3/2}/P_{-2}≳ 0.002 (where dot{E} is the spin-down power, P is the pulsar period, and X = Xi × 10i in CGS units), reconnection proceeds in the radiative cooling regime and results in a soft power-law distribution of cooling particles; in less powerful pulsars, like Vela, particle energization is limited by the current sheet size, and a hard particle spectrum reflects the acceleration mechanism. A strict lower limit on the number density of radiating particles corresponds to emission close to the light cylinder, and, in units of the GJ density, it is ≳ 0.5 in the Crab wind, and κ ≳ 0.05 in the Vela wind.

  16. High-energy emission from the eclipsing millisecond pulsar PSR 1957+20

    NASA Technical Reports Server (NTRS)

    Arons, Jonathan; Tavani, Marco

    1993-01-01

    The properties of the high-energy emission expected from the eclipsing millisecond pulsar system PSR 1957+20 are investigated. Emission is considered by both the relativistic shock produced by the pulsar wind in the nebula surrounding the binary and by the shock constraining the mass outflow from the companion star of PSR 1957+20. On the basis of the results of microscopic plasma physical models of relativistic shocks it is suggested that the high-energy radiation is produced in the range from X-rays to MeV gamma rays in the binary and in the range from 0.01 eV to about 40 keV in the nebula. Doppler boost of the emission in the radiating wind suggests the flux should vary on the orbital time scale, with the largest flux observed roughly coincident with the pulsar's radio eclipse.

  17. High-energy recoil-ion emission in keV heavy-ion surface collisions

    NASA Astrophysics Data System (ADS)

    van Someren, B.; Rudolph, H.; Urazgil'din, I. F.; van Emmichoven, P. A. Zeijlmans; Niehaus, A.

    1997-11-01

    For keV Xe +, Kr + and Ar + ions incident at 30° on Cu(110) we have observed the emission of negatively charged particles with energies up to about 40% of the primary energy. By time-of-flight techniques we have found that electrons are emitted with energies up to 80 eV, whereas the negatively charged high-energy particles are Cu - recoil ions. High-energy Cu + ions have also been found. Simple energy and momentum conservation arguments show that such high recoil energies are indeed possible for multiple collision events in which the primary recoil ion scatters off one or more Cu atoms.

  18. High-energy two-electron capture with emission of a single photon

    SciTech Connect

    Drukarev, E. G.; Mikhailov, A. I.; Mikhailov, I. A.; Scheid, W.

    2007-12-15

    We investigate the two-electron capture with emission of a single photon to the ground state in the Coulomb field of a heavy nucleus in its collision with a light atom. Describing electron-electron interactions in the bound state perturbatively, we obtained an analytical formula for the high-energy limit of the cross section. In combination with previous results obtained in the same approach we calculated the cross section in a broad interval of energies of the collision. We show that the amplitude of the process at high energy depends on the behavior of the bound state wave function near the triple coalescence point. We analyze the properties of the approximate wave functions which are necessary for the description of the high-energy limit.

  19. A serach for moderate- and high-energy neturino emission correlated with gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Becker-Szendy, R.; Bratton, C. B.; Breault, J.; Casper, D.; Dye, S. T.; Gajewski, W.; Goldhaber, M.; Haines, T. J.; Halverson, P. G.; Kielczewska, D.

    1995-01-01

    A temporal correlation analysis between moderate- (60 Mev less than or equal to E(sub nu)greater than or equal to 2500 MeV) and high-energy (E(sub nu) greater than or equal to 2000 MeV) neutrino interactions consist of two types: the moderate-energy interactions that are contained within the volume of IMB-3 and the upward-going muons produced by high-energy nu(sub mu) interactions in the rock around the detector. No evidence is found for moderate- or high-energy neutrino emission from GRBs nor for any neutrino/neutrino correlation. The nonobservation of nu/GRB correlations allows upper limits to be placed on the neutrino flux associated with GRBs.

  20. Very high energy gamma-ray emission from Tycho's supernova remnant

    NASA Astrophysics Data System (ADS)

    Saxon, Dana Boltuch

    Supernova remnant (SNR) G120.1+1.4 (also known as Tycho's SNR) is the remnant of one of only five confirmed historical supernovae. As such, it has been well studied across the electromagnetic spectrum. This thesis describes the first statistically significant detection of very high energy (VHE) (˜ 100 GeV to 100 TeV) gamma rays from Tycho's SNR, reported in 2011 by the VERITAS collaboration. The analysis that led to that detection was performed by this author, and this dissertation will discuss the process in detail. Subsequently, a statistically significant detection in high energy (HE) (˜ 30 MeV to 100 GeV) gamma rays was reported by other authors using data from the Fermi Gamma-Ray Space Telescope. Comparison of models to the spectral energy distribution of the photon flux from this remnant in HE and VHE gamma rays favors a hadronic origin for the emission, particularly when combined with current X-ray data, although a leptonic origin cannot be ruled out at this time. This is significant because a confirmed hadronic origin for the gamma-ray emission would identify this SNR as a site of cosmic ray acceleration, providing observational evidence for the idea that SNRs are the source of the Galactic cosmic ray population. Chapter 1 of this dissertation will provide historical background on Tycho's SNR, along with a summary of modern observations of the remnant across the electromagnetic spectrum. Chapter 2 is a discussion of the role played by SNRs in the process of cosmic ray acceleration, including both theoretical underpinnings and observational evidence. Chapter 3 provides an overview of the field of VHE gamma-ray astronomy, with discussions of gamma-ray production mechanisms and gamma-ray source classes. Chapter 4 describes the instruments used to observe HE and VHE gamma rays. Chapter 5 is a discussion of general analysis methods and techniques for data from Imaging Atmospheric Cherenkov Telescopes (IACTs). Chapter 6 provides details about the specific

  1. Elementary Quantum Mechanics in a High-Energy Process

    ERIC Educational Resources Information Center

    Denville, A.; And Others

    1978-01-01

    Compares two approaches to strong absorption in elementary quantum mechanics; the black sphere and a model based on the continuum theory of nuclear reactions. Examines the application to proton-antiproton interactions at low momenta and concludes that the second model is the appropriate and simplest to use. (Author/GA)

  2. Modulated High-Energy Gamma-Ray Emission from the Microquasar Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Fermi LAT Collaboration; Abdo, A. A.; Ackermann, M.; Ajello, M.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T. H.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Chaty, S.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cominsky, L. R.; Conrad, J.; Corbel, S.; Corbet, R.; Dermer, C. D.; de Palma, F.; Digel, S. W.; do Couto e Silva, E.; Drell, P. S.; Dubois, R.; Dubus, G.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Fortin, P.; Frailis, M.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giavitto, G.; Giebels, B.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hill, A. B.; Hjalmarsdotter, L.; Horan, D.; Hughes, R. E.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocian, M. L.; Koerding, E.; Kuss, M.; Lande, J.; Latronico, J.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Marchand, L.; Marelli, M.; Max-Moerbeck, W.; Mazziotta, M. N.; McColl, N.; McEnery, J. E.; Meurer, C.; Michelson, P. F.; Migliari, S.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Omodei, N.; Ong, R. A.; Ormes, J. F.; Paneque, D.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Pooley, G.; Porter, T. A.; Pottschmidt, K.; Rainò, S.; Rando, R.; Ray, P. S.; Razzano, M.; Rea, N.; Readhead, A.; Reimer, A.; Reimer, O.; Richards, J. L.; Rochester, L. S.; Rodriguez, J.; Rodriguez, A. Y.; Romani, R. W.; Ryde, F.; Sadrozinski, H. F.-W.; Sander, A.; Saz Parkinson, P. M.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spinelli, P.; Starck, J.-L.; Stevenson, M.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tomsick, J. A.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Wilms, J.; Winer, B. L.; Wood, K. W.; Ylinen, T.; Ziegler, M.

    2009-12-01

    Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets.

  3. Modulated high-energy gamma-ray emission from the microquasar Cygnus X-3.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, O; Chaty, S; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Conrad, J; Corbel, S; Corbet, R; Dermer, C D; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Dubois, R; Dubus, G; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fusco, P; Gargano, F; Gehrels, N; Germani, S; Giavitto, G; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hill, A B; Hjalmarsdotter, L; Horan, D; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Koerding, E; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marchand, L; Marelli, M; Max-Moerbeck, W; Mazziotta, M N; McColl, N; McEnery, J E; Meurer, C; Michelson, P F; Migliari, S; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Ong, R A; Ormes, J F; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Pooley, G; Porter, T A; Pottschmidt, K; Rainò, S; Rando, R; Ray, P S; Razzano, M; Rea, N; Readhead, A; Reimer, A; Reimer, O; Richards, J L; Rochester, L S; Rodriguez, J; Rodriguez, A Y; Romani, R W; Ryde, F; Sadrozinski, H F-W; Sander, A; Saz Parkinson, P M; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spinelli, P; Starck, J-L; Stevenson, M; Strickman, M S; Suson, D J; Takahashi, H; Tanaka, T; Thayer, J B; Thompson, D J; Tibaldo, L; Tomsick, J A; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Wilms, J; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2009-12-11

    Microquasars are accreting black holes or neutron stars in binary systems with associated relativistic jets. Despite their frequent outburst activity, they have never been unambiguously detected emitting high-energy gamma rays. The Fermi Large Area Telescope (LAT) has detected a variable high-energy source coinciding with the position of the x-ray binary and microquasar Cygnus X-3. Its identification with Cygnus X-3 is secured by the detection of its orbital period in gamma rays, as well as the correlation of the LAT flux with radio emission from the relativistic jets of Cygnus X-3. The gamma-ray emission probably originates from within the binary system, opening new areas in which to study the formation of relativistic jets. PMID:19965378

  4. Search for ultra-high energy emission from Geminga and five unidentified EGRET sources

    SciTech Connect

    Not Available

    1993-01-01

    Data from the CYGNUS extensive air shower array were searched for continuous ultra-high energy (UHE) gamma radiation from five unidentified EGRET sources and from the Geminga pulsar. No evidence for continuous emission from any of these objects was found. Data in the Geminga source bin were also searched for pulsed emission using the recent EGRET ephemeris (237 ms period). No evidence of a periodic signal was found. The 90% confidence level upper limit on the continuous gamma-ray flux above 80 TeV for Geminga is 7.9 [times] 10[sup [minus]14] cm[sup [minus]2] s[sup [minus]1].

  5. Search for ultra-high energy emission from Geminga and five unidentified EGRET sources

    SciTech Connect

    The CYGNUS Collaboration

    1993-05-01

    Data from the CYGNUS extensive air shower array were searched for continuous ultra-high energy (UHE) gamma radiation from five unidentified EGRET sources and from the Geminga pulsar. No evidence for continuous emission from any of these objects was found. Data in the Geminga source bin were also searched for pulsed emission using the recent EGRET ephemeris (237 ms period). No evidence of a periodic signal was found. The 90% confidence level upper limit on the continuous gamma-ray flux above 80 TeV for Geminga is 7.9 {times} 10{sup {minus}14} cm{sup {minus}2} s{sup {minus}1}.

  6. High-Energy Emission From the Polar Cap and Slot Gap

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2006-01-01

    Thirty-five years after the discovery of rotation-powered pulsars, we still do not understand the fundamentals of their pulsed emission at any wavelength. I will review the latest developments in understanding the high-energy emission of rotation-powered pulsars, with particular emphasis on the polar cap and slot gap models. Special and general relativistic effects play important roles in pulsar emission, from inertial frame-dragging near the stellar surface to aberration, time-of-flight and retardation of the magnetic field near the light cylinder. Understanding how these effects determine what we observe at different wavelengths is critical to unraveling the emission physics. I will discuss how the next generation of gamma-ray detectors, AGILE and GLAST, will test prediction of these models.

  7. Simulating three-dimensional nonthermal high-energy photon emission in colliding-wind binaries

    SciTech Connect

    Reitberger, K.; Kissmann, R.; Reimer, A.; Reimer, O.

    2014-07-01

    Massive stars in binary systems have long been regarded as potential sources of high-energy γ rays. The emission is principally thought to arise in the region where the stellar winds collide and accelerate relativistic particles which subsequently emit γ rays. On the basis of a three-dimensional distribution function of high-energy particles in the wind collision region—as obtained by a numerical hydrodynamics and particle transport model—we present the computation of the three-dimensional nonthermal photon emission for a given line of sight. Anisotropic inverse Compton emission is modeled using the target radiation field of both stars. Photons from relativistic bremsstrahlung and neutral pion decay are computed on the basis of local wind plasma densities. We also consider photon-photon opacity effects due to the dense radiation fields of the stars. Results are shown for different stellar separations of a given binary system comprising of a B star and a Wolf-Rayet star. The influence of orbital orientation with respect to the line of sight is also studied by using different orbital viewing angles. For the chosen electron-proton injection ratio of 10{sup –2}, we present the ensuing photon emission in terms of two-dimensional projections maps, spectral energy distributions, and integrated photon flux values in various energy bands. Here, we find a transition from hadron-dominated to lepton-dominated high-energy emission with increasing stellar separations. In addition, we confirm findings from previous analytic modeling that the spectral energy distribution varies significantly with orbital orientation.

  8. From Radio with Love: an overview of the role of radio observations in understanding high-energy emission from active galaxies

    NASA Astrophysics Data System (ADS)

    Ojha, Roopesh

    2012-03-01

    The gamma-ray satellite Fermi and the ground based TeV facilities MAGIC, VERITAS and HESS have ushered in a new era in the observation of high-energy emission from active galaxies. The energy budgets of these objects have a major contribution from gamma-rays and it is simply not possible to understand their physics without high-energy observations. Though the exact mechanisms for high-energy production in galaxies remains an open question, gamma-rays typically result from interactions between high-energy particles. Via different interactions these same particles can produce radio emission. Thus the non-thermal nature of gamma-ray emission practically guarantees that high-energy emitters are also radio loud. Aside from their obvious role as a component of multiwavelength analysis, radio observations provide two crucial elements essential to understanding the source structure and physical processes of high-energy emitters: very high timing resolution and very high spatial resolution. A brief overview of the unique role played by radio observations in unraveling the mysteries of the high energy Universe is presented here.

  9. From Radio with Love: An Overview of the Role of Radio Observations in Understanding High-Energy Emission from Active Galaxies

    NASA Technical Reports Server (NTRS)

    Ojha, Roopesh

    2012-01-01

    The gamma-ray satellite Fermi and the ground based TeV facilities MAGIC, VERITAS and HESS have ushered in a new era in the observation of high-energy emission from active galaxies. The energy budgets of these objects have a major contribution from gamma-rays and it is simply not possible to understand their physics without high-energy observations. Though the exact mechanisms for high-energy production in galaxies remains an open question, gamma-rays typically result from interactions between high-energy particles. Via different interactions these same particles can produce radio emission. Thus the non-thermal nature of gamma-ray emission practically guarantees that high-energy emitters are also radio loud. Aside from their obvious role as a component of multiwavelength analysis, radio observations provide two crucial elements essential to understanding the source structure and physical processes of high-energy emitters: very high timing resolution and very high spatial resolution. A brief overview of the unique role played by radio observations in unraveling the mysteries of the high energy Universe as presented here.

  10. FERMI OBSERVATIONS OF HIGH-ENERGY GAMMA-RAY EMISSION FROM GRB 090217A

    SciTech Connect

    Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Borgland, A. W.; Bouvier, A.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Baring, M. G.; Bastieri, D.; Bhat, P. N.; Briggs, M. S.; Bissaldi, E.; Bonamente, E.; Brigida, M. E-mail: piron@lpta.in2p3.f

    2010-07-10

    The Fermi observatory is advancing our knowledge of gamma-ray bursts (GRBs) through pioneering observations at high energies, covering more than seven decades in energy with the two on-board detectors, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Here, we report on the observation of the long GRB 090217A which triggered the GBM and has been detected by the LAT with a significance greater than 9{sigma}. We present the GBM and LAT observations and on-ground analyses, including the time-resolved spectra and the study of the temporal profile from 8 keV up to {approx}1 GeV. All spectra are well reproduced by a Band model. We compare these observations to the first two LAT-detected, long bursts GRB 080825C and GRB 080916C. These bursts were found to have time-dependent spectra and exhibited a delayed onset of the high-energy emission, which are not observed in the case of GRB 090217A. We discuss some theoretical implications for the high-energy emission of GRBs.

  11. Fermi Observations of High-energy Gamma-ray Emission from GRB 090217A

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bhat, P. N.; Bissaldi, E.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Briggs, M. S.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Connaughton, V.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Granot, J.; Grenier, I. A.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kippen, R. M.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Llena Garde, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McBreen, S.; McEnery, J. E.; McGlynn, S.; Meegan, C.; Mehault, J.; Mészáros, P.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakajima, H.; Nakamori, T.; Naumann-Godo, M.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paciesas, W. S.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Porter, T. A.; Preece, R.; Racusin, J. L.; Rainò, S.; Rando, R.; Rau, A.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Ripken, J.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sander, A.; Scargle, J. D.; Schalk, T. L.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uehara, T.; Usher, T. L.; Vandenbroucke, J.; van der Horst, A. J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wang, P.; Wilson-Hodge, C.; Winer, B. L.; Wood, K. S.; Wu, X. F.; Yamazaki, R.; Yang, Z.; Ylinen, T.; Ziegler, M.; Fermi LAT Collaboration; Fermi GBM Collaboration

    2010-07-01

    The Fermi observatory is advancing our knowledge of gamma-ray bursts (GRBs) through pioneering observations at high energies, covering more than seven decades in energy with the two on-board detectors, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Here, we report on the observation of the long GRB 090217A which triggered the GBM and has been detected by the LAT with a significance greater than 9σ. We present the GBM and LAT observations and on-ground analyses, including the time-resolved spectra and the study of the temporal profile from 8 keV up to ~1 GeV. All spectra are well reproduced by a Band model. We compare these observations to the first two LAT-detected, long bursts GRB 080825C and GRB 080916C. These bursts were found to have time-dependent spectra and exhibited a delayed onset of the high-energy emission, which are not observed in the case of GRB 090217A. We discuss some theoretical implications for the high-energy emission of GRBs.

  12. VERITAS UPPER LIMIT ON THE VERY HIGH ENERGY EMISSION FROM THE RADIO GALAXY NGC 1275

    SciTech Connect

    Acciari, V. A.; Benbow, W.; Aliu, E.; Boltuch, D.; Arlen, T.; Celik, O.; Aune, T.; Bautista, M.; Cogan, P.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Bradbury, S. M.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Duke, C.

    2009-12-01

    The recent detection by the Fermi gamma-ray space telescope of high-energy gamma-rays from the radio galaxy NGC 1275 makes the observation of the very high energy (VHE: E>100 GeV) part of its broadband spectrum particularly interesting, especially for the understanding of active galactic nuclei with misaligned multi-structured jets. The radio galaxy NGC 1275 was recently observed by VERITAS at energies above 100 GeV for about 8 hr. No VHE gamma-ray emission was detected by VERITAS from NGC 1275. A 99% confidence level upper limit of 2.1% of the Crab Nebula flux level is obtained at the decorrelation energy of approximately 340 GeV, corresponding to 19% of the power-law extrapolation of the Fermi Large Area Telescope result.

  13. Very high energy gamma-ray emission of Perseus Cluster and NGC 1275

    NASA Astrophysics Data System (ADS)

    Sinitsyna, V. G.; Sinitsyna, V. Y.

    2016-07-01

    The Perseus cluster of galaxies with the central galaxy NGC 1275 is ideally suitable both for studying the physics of relativistic jets from Active Galactic Nuclei and for revealing the feedback role of the central galaxy. The data obtained at very high energies by SHALON, namely the images of the galaxy and its surroundings, and the flux variability indicate that the TeV γ-ray emission is produced by a number of processes: in partraular, part of this emission is generated by relativistic jets in the nucleus of NGC 1275 itself. Unique data on GK Per(Nova 1901) TeV γ-ray emission were obtained with SHALON experiment for the first time.

  14. Search for Very High Energy Emission from Gamma-Ray Bursts using Milagro

    SciTech Connect

    Saz Parkinson, P. M.

    2007-07-12

    Gamma-Ray Bursts (GRBs) have been detected at GeV energies by EGRET and models predict emission at > 100 GeV. Milagro is a wide field (2 sr) high duty cycle (> 90%) ground based water Cherenkov detector that records extensive air showers in the energy range 100 GeV to 100 TeV. We have searched for very high energy emission from a sample of 106 gamma-ray bursts (GRB) detected since the beginning of 2000 by BATSE, BeppoSax, HETE-2, INTEGRAL, Swift or the IPN. No evidence for emission from any of the bursts has been found and we present upper limits from these bursts.

  15. Unraveling the high-energy emission components of gamma-ray binaries

    NASA Astrophysics Data System (ADS)

    Zabalza, V.; Bosch-Ramon, V.; Aharonian, F.; Khangulyan, D.

    2013-03-01

    Context. The high and very high energy spectrum of gamma-ray binaries has become a challenge for all theoretical explanations since the detection of powerful, persistent GeV emission from LS 5039 and LS I +61 303 by Fermi/LAT. The spectral cutoff at a few GeV indicates that the GeV component and the fainter, hard TeV emission above 100 GeV are not directly related. Aims: We explore the possible origins of these two emission components in the framework of a young, non-accreting pulsar orbiting the massive star, and initiating the non-thermal emission through the interaction of the stellar and pulsar winds. Methods: The pulsar/stellar wind interaction in a compact-orbit binary gives rise to two potential locations for particle acceleration: the shocks at the head-on collision of the winds and the termination shock caused by Coriolis forces on scales larger than the binary separation. We explore the suitability of these two locations to host the GeV and TeV emitters, respectively, through the study of their non-thermal emission along the orbit. We focus on the application of this model to LS 5039 given its well-determined stellar wind with respect to other gamma-ray binaries. Results: The application of the proposed model to LS 5039 indicates that these two potential emitter locations provide the necessary conditions for reproduction of the two-component high-energy gamma-ray spectrum of LS 5039. In addition, the ambient postshock conditions required at each of the locations are consistent with recent hydrodynamical simulations. Conclusions: The scenario based on the interaction of the stellar and pulsar winds is compatible with the GeV and TeV emission observed from gamma-ray binaries with unknown compact objects, such as LS 5039 and LS I +61 303.

  16. THE {gamma}-RAY SPECTRUM OF GEMINGA AND THE INVERSE COMPTON MODEL OF PULSAR HIGH-ENERGY EMISSION

    SciTech Connect

    Lyutikov, Maxim

    2012-09-20

    We reanalyze the Fermi spectra of the Geminga and Vela pulsars. We find that the spectrum of Geminga above the break is well approximated by a simple power law without the exponential cutoff, making Geminga's spectrum similar to that of Crab. Vela's broadband {gamma}-ray spectrum is equally well fit with both the exponential cutoff and the double power-law shapes. In the broadband double power-law fits, for a typical Fermi spectrum of a bright {gamma}-ray pulsar, most of the errors accumulate due to the arbitrary parameterization of the spectral roll-off. In addition, a power law with an exponential cutoff gives an acceptable fit for the underlying double power-law spectrum for a very broad range of parameters, making such fitting procedures insensitive to the underlying Fermi photon spectrum. Our results have important implications for the mechanism of pulsar high-energy emission. A number of observed properties of {gamma}-ray pulsars-i.e., the broken power-law spectra without exponential cutoffs and stretching in the case of Crab beyond the maximal curvature limit, spectral breaks close to or exceeding the maximal breaks due to curvature emission, patterns of the relative intensities of the leading and trailing pulses in the Crab repeated in the X-ray and {gamma}-ray regions, presence of profile peaks at lower energies aligned with {gamma}-ray peaks-all point to the inverse Compton origin of the high-energy emission from majority of pulsars.

  17. Sources of High-Energy Emission in the Green Pea Galaxies: New Constraints from Magellan Spectra

    NASA Astrophysics Data System (ADS)

    Carroll, Derek Alexander

    2016-01-01

    The recently discovered Green Pea galaxies display extreme starburst activity and may be some of the only possible Lyman continuum emitting galaxies at low redshift. Green Peas are characterized by their unusually high [O III]/[O II] ratios, similar to the ratios observed in high-redshift galaxies. In addition, the presence of the high-energy He II 4686 line shows that the Green Peas are highly ionized. However, the origin of the He II emission in the Green Peas, and many other starburst galaxies, is still an open question. We analyze IMACS and MagE spectra from the Magellan telescopes in order to evaluate the most probable cause of this He II emission. We also analyze other properties like dust content, temperature and density, and kinematic components. Our IMACS spectra show no Wolf-Rayet (WR) features. We set upper limits on the WR populations in our sample and conclude that Wolf-Rayet stars are not a likely candidate for the He II emission. With deeper MagE spectra we investigate energetic shocks as a possible source of the He II, and move one step closer to uncovering the origin of high-energy photons in these unique starbursts.

  18. An outer gap model of high-energy emission from rotation-powered pulsars

    NASA Technical Reports Server (NTRS)

    Chiang, James; Romani, Roger W.

    1994-01-01

    We describe a refined calculation of high-energy emission from rotation-powered pulsars based on the outer gap model of Cheng, Ho, & Ruderman (1986 a, b). In this calculation, vacuum gaps form in regions near the speed-of-light cylinder of the pulsar magnetosphere along the boundary between the closed and open field line zones. We have improved upon previous efforts to model the spectra from these pulsars (e.g., Cheng et al. 1986b; Ho 1989) by following the variation in particle production and radiation properties with position in the outer gap. Curvature, synchotron, and inverse-Compton scattering fluxes vary significantly over the gap, and their interactions via photon-photon pair production build up the radiating charge populations at varying rates. We have also incorporated an approximate treatment of the transport particle and photon fluxes between gap emission zones. These effects, along with improved computations of the particle and photon distribution, provide very important modifications of the model gamma-ray flux. In paticular, we attempt to make specific predictions of pulse profile shapes and spectral variations as a function of pulse phase and suggest further extensions to the model which may provide accurate computations of the observed high-energy emissions.

  19. High energy (gamma)-ray emission from the starburst nucleus of NGC 253

    SciTech Connect

    Domingo-Santamaria, E; Torres, D F

    2005-06-15

    The high density medium that characterizes the central regions of starburst galaxies and its power to accelerate particles up to relativistic energies make these objects good candidates as {gamma}-rays sources. In this paper, a self-consistent model of the multifrequency emission of the starburst galaxy NGC 253, from radio to gamma-rays, is presented. The model is in agreement with all current measurements and provides predictions for the high energy behavior of the NGC 253 central region. Prospects for observations with the HESS array and GLAST satellite are especially discussed.

  20. The prompt GRB high energy emission from internal shocks: synchrotron vs inverse Compton component

    SciTech Connect

    Bosnjak, Zeljka; Daigne, Frederic; Dubus, Guillaume

    2009-05-25

    We performed a detailed calculation of gamma-ray burst (GRB) prompt emission in the framework of the internal shock scenario, focusing on the high energy (GeV) bands. In order to follow the evolution of the ultrarelativistic inhomogeneous wind, we combined a model for the dynamics of internal shocks with a detailed calculation of the radiative processes occurring in the shocked medium. We present the resulting synthetic GRB light curves and spectra. We show the spectral evolution that can be expected for different sets of microphysics parameters and parameters of the dynamical evolution, and how the relative importance of synchrotron and inverse Compton components is varying during a burst.

  1. Related investigations on the physics of high energy emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Margon, Bruce

    1991-01-01

    The Final Technical Report on a number of related investigations on the physics of high energy emission from active galactic nuclei, such as Seyfert galaxies and quasi-stellar objects is presented. The chief conclusions of the work are briefly described, and citations to the papers supported by this grant and published in the refereed scientific literature are provided. Areas of research included: 'warm' galaxies observed in x rays; x ray/infrared correlations in galaxies; the contribution of active galaxies to the cosmic x ray background radiation; and an unusual x ray emitting starburst galaxy.

  2. Modelling the high-energy emission from gamma-ray binaries using numerical relativistic hydrodynamics

    NASA Astrophysics Data System (ADS)

    Dubus, G.; Lamberts, A.; Fromang, S.

    2015-09-01

    Context. Detailed modelling of the high-energy emission from gamma-ray binaries has been propounded as a path to pulsar wind physics. Aims: Fulfilling this ambition requires a coherent model of the flow and its emission in the region where the pulsar wind interacts with the stellar wind of its companion. Methods: We have developed a code that follows the evolution and emission of electrons in the shocked pulsar wind based on inputs from a relativistic hydrodynamical simulation. The code is used to model the well-documented spectral energy distribution and orbital modulations from LS 5039. Results: The pulsar wind is fully confined by a bow shock and a back shock. The particles are distributed into a narrow Maxwellian, emitting mostly GeV photons, and a power law radiating very efficiently over a broad energy range from X-rays to TeV gamma rays. Most of the emission arises from the apex of the bow shock. Doppler boosting shapes the X-ray and very high energy (VHE) lightcurves, constraining the system inclination to i ≈ 35°. There is tension between the hard VHE spectrum and the level of X-ray to MeV emission, which requires differing magnetic field intensities that are hard to achieve with constant magnetisation σ and Lorentz factor Γp of the pulsar wind. Our best compromise implies σ ≈ 1 and Γp ≈ 5 × 103, so respectively higher and lower than the typical values in pulsar wind nebulae. Conclusions: The high value of σ derived here, where the wind is confined close to the pulsar, supports the classical picture that has pulsar winds highly magnetised at launch. However, such magnetisations will require that further investigations are based on relativistic MHD simulations. Movies associated to Figs. A.1-A.4 are available in electronic form at http://www.aanda.org

  3. EVIDENCE FOR A SECOND COMPONENT IN THE HIGH-ENERGY CORE EMISSION FROM CENTAURUS A?

    SciTech Connect

    Sahakyan, N.; Yang, R.; Aharonian, F. A.; Rieger, F. M.

    2013-06-10

    We report on an analysis of Fermi Large Area Telescope data from four years of observations of the nearby radio galaxy Centaurus A (Cen A). The increased photon statistics results in a detection of high-energy (>100 MeV) gamma-rays up to 50 GeV from the core of Cen A, with a detection significance of about 44{sigma}. The average gamma-ray spectrum of the core reveals evidence for a possible deviation from a simple power law. A likelihood analysis with a broken power-law model shows that the photon index becomes harder above E{sub b} {approx_equal} 4 GeV, changing from {Gamma}{sub 1} = 2.74 {+-} 0.03 below to {Gamma}{sub 2} = 2.09 {+-} 0.20 above. This hardening could be caused by the contribution of an additional high-energy component beyond the common synchrotron self-Compton jet emission. No clear evidence for variability in the high-energy domain is seen. We compare our results with the spectrum reported by H.E.S.S. in the TeV energy range and discuss possible origins of the hardening observed.

  4. Evidence for a Second Component in the High-energy Core Emission from Centaurus A?

    NASA Astrophysics Data System (ADS)

    Sahakyan, N.; Yang, R.; Aharonian, F. A.; Rieger, F. M.

    2013-06-01

    We report on an analysis of Fermi Large Area Telescope data from four years of observations of the nearby radio galaxy Centaurus A (Cen A). The increased photon statistics results in a detection of high-energy (>100 MeV) gamma-rays up to 50 GeV from the core of Cen A, with a detection significance of about 44σ. The average gamma-ray spectrum of the core reveals evidence for a possible deviation from a simple power law. A likelihood analysis with a broken power-law model shows that the photon index becomes harder above Eb ~= 4 GeV, changing from Γ1 = 2.74 ± 0.03 below to Γ2 = 2.09 ± 0.20 above. This hardening could be caused by the contribution of an additional high-energy component beyond the common synchrotron self-Compton jet emission. No clear evidence for variability in the high-energy domain is seen. We compare our results with the spectrum reported by H.E.S.S. in the TeV energy range and discuss possible origins of the hardening observed.

  5. Influence of high energy ion irradiation on the field emission characteristics of CVD diamond films

    NASA Astrophysics Data System (ADS)

    Koinkar, P. M.; Khairnar, R. S.; Khan, S. A.; Gupta, R. P.; Avasthi, D. K.; More, M. A.

    2006-03-01

    The field emission characteristics of ion-irradiated CVD diamond thin film deposited on silicon substrate has been studied. The diamond thin films, synthesized by hot filament chemical vapor deposition (HFCVD) method, were irradiated by high energy (100 MeV) silver ion (107Ag+ with charge state 9) in the fluence range of 3 × 1011-1 × 1013 ions/cm2. The CVD diamond films were characterized by Raman spectroscopy. The Raman spectra of irradiated samples clearly reveal structural damage due to ion irradiation, which is observed to be fluence dependent. However complete graphitization is not observed. The field emission current-voltage (I-V) characteristics were recorded in 'diode' configuration at base pressure ∼1 × 10-8 mbar. Upon ion irradiation the field emission current is observed to increase with the reduction in the threshold voltage, required to draw 1 μA current. The results indicate that ion irradiation leads to better emission characteristics and the structural damage caused by ion irradiation plays a significant role in emission behavior of CVD diamond films.

  6. On the Evolution of and High-Energy Emission from GHz-Peaked-Spectrum Sources

    SciTech Connect

    Stawarz, L.; Ostorero, L.; Begelman, M.C.; Moderski, R.; Kataoka, J.; Wagner, S.

    2007-12-18

    Here we discuss evolution and broad-band emission of compact (< kpc) lobes in young radio sources. We propose a simple dynamical description for these objects, consisting of a relativistic jet propagating into a uniform gaseous medium in the central parts of an elliptical host. In the framework of the proposed model, we follow the evolution of ultrarelativistic electrons injected from a terminal hotspot of a jet to expanding lobes, taking into account their adiabatic energy losses as well as radiative cooling. This allows us to discuss the broad-band lobe emission of young radio sources. In particular, we argue that the observed spectral turnover in the radio synchrotron spectra of these objects cannot originate from the synchrotron self-absorption process but is most likely due to free-free absorption effects connected with neutral clouds of interstellar medium engulfed by the expanding lobes and photoionized by active centers. We also find a relatively strong and complex high-energy emission component produced by inverse-Compton up-scattering of various surrounding photon fields by the lobes electrons. We argue that such high energy radiation is strong enough to account for several observed properties of GHz-peaked-spectrum (GPS) radio galaxies at UV and X-ray frequencies. In addition, this emission is expected to extend up to GeV (or possibly even TeV) photon energies and can thus be probed by several modern {gamma}-ray instruments. In particular, we suggest that GPS radio galaxies should constitute a relatively numerous class of extragalactic sources detected by GLAST.

  7. MAGIC DISCOVERY OF VERY HIGH ENERGY EMISSION FROM THE FSRQ PKS 1222+21

    SciTech Connect

    Aleksic, J.; Blanch, O.; Antonelli, L. A.; Bonnoli, G.; Antoranz, P.; Backes, M.; Barrio, J. A.; Bastieri, D.; Becerra Gonzalez, J.; Berger, K.; Bednarek, W.; Berdyugin, A.; Bernardini, E.; Biland, A.; Boller, A.; Braun, I.; Bock, R. K.; Borla Tridon, D.; Bretz, T.; Canellas, A. E-mail: antonio.stamerra@pi.infn.it E-mail: ksaito@mpp.mpg.de

    2011-03-20

    Very high energy (VHE) {gamma}-ray emission from the flat spectrum radio quasar (FSRQ) PKS 1222+21 (4C 21.35, z = 0.432) was detected with the MAGIC Cherenkov telescopes during a short observation ({approx}0.5 hr) performed on 2010 June 17. The MAGIC detection coincides with high-energy MeV/GeV {gamma}-ray activity measured by the Large Area Telescope (LAT) on board the Fermi satellite. The VHE spectrum measured by MAGIC extends from about 70 GeV up to at least 400 GeV and can be well described by a power-law dN/dE {proportional_to} E {sup -}{Gamma} with a photon index {Gamma} = 3.75 {+-} 0.27{sub stat} {+-} 0.2{sub syst}. The averaged integral flux above 100 GeV is (4.6 {+-} 0.5) x 10{sup -10} cm{sup -2} s{sup -1} ({approx}1 Crab Nebula flux). The VHE flux measured by MAGIC varies significantly within the 30 minute exposure implying a flux doubling time of about 10 minutes. The VHE and MeV/GeV spectra, corrected for the absorption by the extragalactic background light (EBL), can be described by a single power law with photon index 2.72 {+-} 0.34 between 3 GeV and 400 GeV, and is consistent with emission belonging to a single component in the jet. The absence of a spectral cutoff constrains the {gamma}-ray emission region to lie outside the broad-line region, which would otherwise absorb the VHE {gamma}-rays. Together with the detected fast variability, this challenges present emission models from jets in FSRQs. Moreover, the combined Fermi/LAT and MAGIC spectral data yield constraints on the density of the EBL in the UV-optical to near-infrared range that are compatible with recent models.

  8. Fermi Large Area Telescope observation of high-energy solar flares: constraining emission scenarios

    NASA Astrophysics Data System (ADS)

    Omodei, Nicola; Pesce-Rollins, Melissa; Petrosian, Vahe; Liu, Wei; Rubio da Costa, Fatima

    2015-08-01

    The Fermi Large Area Telescope (LAT) is the most sensitive instrument ever deployed in space for observing gamma-ray emission >100 MeV. This has also been demonstrated by its detection of quiescent gamma-ray emission from pions produced by cosmic-ray protons interacting in the solar atmosphere, and from cosmic-ray electron interactions with solar optical photons. The Fermi LAT has also detected high-energy gamma-ray emission associated with GOES M-class and X-class X-ray flares, each accompanied by a coronal mass ejection and a solar energetic particle event increasing the number of detected solar flares by almost a factor of 10 with respect to previous space observations. During the impulsive phase, gamma rays with energies up to several hundreds of MeV have been recorded by the LAT. Emission up to GeV energies lasting several hours after the flare has also been recorded by the LAT. Of particular interest are the recent detections of two solar flares whose position behind the limb was confirmed by the STEREO-B satellite. While gamma-ray emission up to tens of MeV resulting from proton interactions has been detected before from occulted solar flares, the significance of these particular events lies in the fact that these are the first detections of >100 MeV gamma-ray emission from footpoint-occulted flares. We will present the Fermi-LAT, RHESSI and STEREO observations of these flares and discuss the various emission scenarios for these sources.

  9. Fermi-LAT Observations of High-Energy Gamma-Ray Emission toward the Galactic Center

    NASA Astrophysics Data System (ADS)

    Ajello, M.; Albert, A.; Atwood, W. B.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caputo, R.; Caragiulo, M.; Caraveo, P. A.; Cecchi, C.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Cominsky, L. R.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Di Venere, L.; Drell, P. S.; Favuzzi, C.; Ferrara, E. C.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Guiriec, S.; Gustafsson, M.; Harding, A. K.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Karwin, C.; Knödlseder, J.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill, J.; Maldera, S.; Malyshev, D.; Manfreda, A.; Mayer, M.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nuss, E.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Ritz, S.; Sánchez-Conde, M.; Saz Parkinson, P. M.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Spada, F.; Spandre, G.; Spinelli, P.; Suson, D. J.; Tajima, H.; Takahashi, H.; Thayer, J. B.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Vianello, G.; Winer, B. L.; Wood, K. S.; Zaharijas, G.; Zimmer, S.

    2016-03-01

    The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission toward the Galactic center (GC) in high-energy γ-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1-100 GeV from a 15° × 15° region about the direction of the GC. Specialized interstellar emission models (IEMs) are constructed to enable the separation of the γ-ray emissions produced by cosmic ray particles interacting with the interstellar gas and radiation fields in the Milky Way into that from the inner ˜1 kpc surrounding the GC, and that from the rest of the Galaxy. A catalog of point sources for the 15° × 15° region is self-consistently constructed using these IEMs: the First Fermi-LAT Inner Galaxy Point Source Catalog (1FIG). The spatial locations, fluxes, and spectral properties of the 1FIG sources are presented, and compared with γ-ray point sources over the same region taken from existing catalogs. After subtracting the interstellar emission and point-source contributions a residual is found. If templates that peak toward the GC are used to model the positive residual the agreement with the data improves, but none of the additional templates tried account for all of its spatial structure. The spectrum of the positive residual modeled with these templates has a strong dependence on the choice of IEM.

  10. High-energy emissions from young pulsars: Perspective from the outer gap model

    SciTech Connect

    Ho, Cheng

    1992-09-01

    Young pulsars such as the Crab and Vela pulsars are the most prominent gamma-ray sources in the Galaxy, powered by the neutron star`s rotational energy and the spinning magnetic field. Since the late 1960`s, a large amount of data has been amassed for these pulsars. With the recent launches of ROSAT, Compton Gamma-Ray Observatory and other new instruments, many exciting new results have been reported. In this Workshop, we learned the weak and soft pulsed emission from the Vela pulsar, the possible detection of spectral turn-over at {approximately} 30 MeV, the detection of gamma-ray emission from PSR1509-58, and observation of pulse profile variability from the Crab pulsar. Soon after the Workshop, the discovery of gamma-ray pulsations from PSR1706-44 and Geminga were reported. All of these contribute to the large pool of hints that theorists need in order to explain the origin of these powerful emission. In this paper, we discuss results from the outer gap model and comparisons to observations. Section 2 gives a brief overview of the outer gap model. Section 3 discusses the high-energy spectrum from the Crab, PSR0540-693, and Vela. In Section 4, we discuss the pulse profile for pulsars with Crab-like parameters. Section 5 discusses outer gap evolution.

  11. High-energy emissions from young pulsars: Perspective from the outer gap model

    SciTech Connect

    Ho, Cheng.

    1992-01-01

    Young pulsars such as the Crab and Vela pulsars are the most prominent gamma-ray sources in the Galaxy, powered by the neutron star's rotational energy and the spinning magnetic field. Since the late 1960's, a large amount of data has been amassed for these pulsars. With the recent launches of ROSAT, Compton Gamma-Ray Observatory and other new instruments, many exciting new results have been reported. In this Workshop, we learned the weak and soft pulsed emission from the Vela pulsar, the possible detection of spectral turn-over at {approximately} 30 MeV, the detection of gamma-ray emission from PSR1509-58, and observation of pulse profile variability from the Crab pulsar. Soon after the Workshop, the discovery of gamma-ray pulsations from PSR1706-44 and Geminga were reported. All of these contribute to the large pool of hints that theorists need in order to explain the origin of these powerful emission. In this paper, we discuss results from the outer gap model and comparisons to observations. Section 2 gives a brief overview of the outer gap model. Section 3 discusses the high-energy spectrum from the Crab, PSR0540-693, and Vela. In Section 4, we discuss the pulse profile for pulsars with Crab-like parameters. Section 5 discusses outer gap evolution.

  12. Fermi observations of high-energy gamma-ray emission from GRB 080916C.

    PubMed

    Abdo, A A; Ackermann, M; Arimoto, M; Asano, K; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Band, D L; Barbiellini, G; Baring, M G; Bastieri, D; Battelino, M; Baughman, B M; Bechtol, K; Bellardi, F; Bellazzini, R; Berenji, B; Bhat, P N; Bissaldi, E; Blandford, R D; Bloom, E D; Bogaert, G; Bogart, J R; Bonamente, E; Bonnell, J; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Briggs, M S; Brigida, M; Bruel, P; Burnett, T H; Burrows, D; Busetto, G; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Ceccanti, M; Cecchi, C; Celotti, A; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L R; Connaughton, V; Conrad, J; Costamante, L; Cutini, S; Deklotz, M; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Dingus, B L; do Couto E Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Evans, P A; Fabiani, D; Farnier, C; Favuzzi, C; Finke, J; Fishman, G; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Goldstein, A; Granot, J; Greiner, J; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Haller, G; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hernando Morat, J A; Hoover, A; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kavelaars, A; Kawai, N; Kelly, H; Kennea, J; Kerr, M; Kippen, R M; Knödlseder, J; Kocevski, D; Kocian, M L; Komin, N; Kouveliotou, C; Kuehn, F; Kuss, M; Lande, J; Landriu, D; Larsson, S; Latronico, L; Lavalley, C; Lee, B; Lee, S-H; Lemoine-Goumard, M; Lichti, G G; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marangelli, B; Mazziotta, M N; McBreen, S; McEnery, J E; McGlynn, S; Meegan, C; Mészáros, P; Meurer, C; Michelson, P F; Minuti, M; Mirizzi, N; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Moretti, E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Nelson, D; Nolan, P L; Norris, J P; Nuss, E; Ohno, M; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paciesas, W S; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Perri, M; Pesce-Rollins, M; Petrosian, V; Pinchera, M; Piron, F; Porter, T A; Preece, R; Rainò, S; Ramirez-Ruiz, E; Rando, R; Rapposelli, E; Razzano, M; Razzaque, S; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Reyes, L C; Ritz, S; Rochester, L S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Segal, K N; Sgrò, C; Shimokawabe, T; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stamatikos, M; Starck, J-L; Stecker, F W; Steinle, H; Stephens, T E; Strickman, M S; Suson, D J; Tagliaferri, G; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Tenze, A; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Turri, M; Tuvi, S; Usher, T L; van der Horst, A J; Vigiani, L; Vilchez, N; Vitale, V; von Kienlin, A; Waite, A P; Williams, D A; Wilson-Hodge, C; Winer, B L; Wood, K S; Wu, X F; Yamazaki, R; Ylinen, T; Ziegler, M

    2009-03-27

    Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass. PMID:19228997

  13. The MIDAS experiment: A prototype for the microwave emission of Ultra-High Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Monasor, M.; Alekotte, I.; Alvarez-Muñiz, J.; Berlin, A.; Bertou, X.; Bodgan, M.; Bohacova, M.; Bonifazi, C.; Carvalho, W.; de Mello Neto, J. R. T.; Genat, J. F.; Facal San Luis, P.; Mills, E.; Rouille D'Orfeuil, B.; Wayne, S.; Reyes, L. C.; Santos, E. M.; Privitera, P.; Williams, C.; Zas, E.

    2011-06-01

    Recent measurements suggest that extensive air showers initiated by ultra-high energy cosmic rays (UHECR) emit signals in the microwave band of the electromagnetic spectrum caused by the collisions of the free-electrons with the atmospheric neutral molecules in the plasma produced by the passage of the shower. Such emission is isotropic and could allow the detection of air showers with 100% duty cycle and a calorimetric-like energy measurement, a significant improvement over current detection techniques. We have built MIDAS (MIcrowave Detection of Air Showers), a prototype of microwave detector, which consists of a 4.5 m diameter antenna with a cluster of 53 feed-horns in the 4 GHz range. The details of the prototype and first results will be presented.

  14. The high-energy γ-ray emission of AP Librae

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Backes, M.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; O'C. Drury, L.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Méhault, J.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Odaka, H.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reichardt, I.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.; Finke, J.; Fortin, P.; Horan, D.

    2015-01-01

    The γ-ray spectrum of the low-frequency-peaked BL Lac (LBL) object AP Librae is studied, following the discovery of very-high-energy (VHE; E> 100 GeV) γ-ray emission up to the TeV range by the H.E.S.S. experiment. This makes AP Librae one of the few VHE emitters of the LBL type. The measured spectrum yields a flux of (8.8 ± 1.5stat ± 1.8sys) × 10-12 cm-2 s-1 above 130 GeV and a spectral index of Γ = 2.65 ± 0.19stat ± 0.20sys. This study also makes use of Fermi-LAT observations in the high energy (HE, E> 100 MeV) range, providing the longest continuous light curve (5 years) ever published on this source. The source underwent a flaring event between MJD 56 306-56 376 in the HE range, with a flux increase of a factor of 3.5 in the 14 day bin light curve and no significant variation in spectral shape with respect to the low-flux state. While the H.E.S.S. and (low state) Fermi-LAT fluxes are in good agreement where they overlap, a spectral curvature between the steep VHE spectrum and the Fermi-LAT spectrum is observed. The maximum of the γ-ray emission in the spectral energy distribution is located below the GeV energy range.

  15. Effects of high energy radiation on the mechanical properties of epoxy graphite fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Gilbert, R. D.; Fornes, R. E.; Memory, J. D.

    1983-01-01

    The effects of high energy radiation on mechanical properties and on the molecular and structural properties of graphite fiber reinforced composites are assessed so that durability in space applications can be predicted. A listing of composite systems irradiated along with the maximum radiation dose applied and type of mechanical tests performed is shown. These samples were exposed to 1/2 MeV electrons.

  16. Search for High-energy Gamma-ray Emission from Tidal Disruption Events with the Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Peng, Fang-Kun; Tang, Qing-Wen; Wang, Xiang-Yu

    2016-07-01

    Massive black holes at galaxy center may tear apart a star when the star passes occasionally within the disruption radius, which is the so-called tidal disruption event (TDE). Most TDEs radiate with thermal emission resulting from the acceleration disk, but three TDEs have been detected in bright nonthermal X-ray emission, which is interpreted as arising from the relativistic jets. A search for high-energy gamma-ray emission from one relativistic TDE (Swift J164449.3+573451) with the Fermi Large Area Telescope (LAT) has yielded nondetection. In this paper, we report the search for high-energy emission from the other two relativistic TDEs (Swift J2058.4+0516 and Swift J1112.2-8238) during the flare period. No significant GeV emission is found, with an upper limit fluence in the LAT energy range being less than 1% of that in X-rays. Compared with gamma-ray bursts and blazars, these TDEs have the lowest flux ratio between GeV emission and X-ray emission. The nondetection of high-energy emission from relativistic TDEs could be due to the fact that the high-energy emission is absorbed by soft photons in the source. Based on this hypothesis, upper limits on the bulk Lorentz factors, {{Γ }}≲ 30, are then obtained for the jets in these TDEs. We also search for high-energy gamma-ray emission from the nearest TDE discovered to date, ASASSN-14li. No significant GeV emission is found, and an upper limit of L(0.1{--}10 {GeV})≤slant 4.4× {10}42 erg s‑1 (at 95% confidence level) is obtained for the first 107 s after the disruption.

  17. Effects of high energy photon emissions in laser generated ultra-relativistic plasmas: Real-time synchrotron simulations

    SciTech Connect

    Wallin, Erik; Gonoskov, Arkady; Marklund, Mattias

    2015-03-15

    We model the emission of high energy photons due to relativistic charged particle motion in intense laser-plasma interactions. This is done within a particle-in-cell code, for which high frequency radiation normally cannot be resolved due to finite time steps and grid size. A simple expression for the synchrotron radiation spectra is used together with a Monte-Carlo method for the emittance. We extend previous work by allowing for arbitrary fields, considering the particles to be in instantaneous circular motion due to an effective magnetic field. Furthermore, we implement noise reduction techniques and present validity estimates of the method. Finally, we perform a rigorous comparison to the mechanism of radiation reaction, and find the emitted energy to be in excellent agreement with the losses calculated using radiation reaction.

  18. Milagro Search for Very High Energy Emission from Gamma-Ray Bursts in the Swift Era

    SciTech Connect

    Saz Parkinson, P. M.

    2006-05-19

    The recently launched Swift satellite is providing an unprecedented number of rapid and accurate Gamma-Ray Burst (GRB) localizations, facilitating a flurry of follow-up observations by a large number of telescopes at many different wavelengths. The Very High Energy (VHE, >100 GeV) regime has so far been relatively unexplored. Milagro is a wide field of view (2 sr) and high duty cycle (> 90%) ground-based gamma-ray telescope which employs a water Cherenkov detector to monitor the northern sky almost continuously in the 100 GeV to 100 TeV energy range. We have searched the Milagro data for emission from the most recent GRBs identified within our field of view. These include three Swift bursts which also display late-time X-ray flares. We have searched for emission coincident with these flares. No significant detection was made. A 99% confidence upper limit is provided for each of the GRBs, as well as the flares.

  19. Extended Acceleration in Slot Gaps and Pulsar High-Energy Emission

    NASA Technical Reports Server (NTRS)

    White, Nicholas E. (Technical Monitor); Muslimov, Alex G.; Harding, Alice K.

    2003-01-01

    We revise the physics of primary electron acceleration in the "slot gap" (SG) above the pulsar polar caps (PCs), a regime originally proposed by Arons and Scharlemann (1979) in their electrodynamic model of pulsar PCs. We employ the standard definition of the SG as a pair-free space between the last open field lines and the boundary of the pair plasma column which is expected to develop above the bulk of the PC. The rationale for our revision is that the proper treatment of primary acceleration within the pulsar SGs should take into account the effect of the narrow geometry of the gap on the electrodynamics within the gap and also to include the effect of inertial frame dragging on the particle acceleration. We show that the accelerating electric field within the gap, being significantly boosted by the effect of frame dragging, becomes reduced because of the gap geometry by a factor proportional to the square of the SG width. The combination of the effects of frame dragging and geometrical screening in the gap region naturally gives rise to a regime of extended acceleration, that is not limited to favorably curved field lines as in earlier models, and the possibility of multiple-pair production by curvature photons at very high altitudes, up to several stellar radii. We present our estimates of the characteristic SG thickness across the PC, energetics of primaries accelerated within the gap, high-energy bolometric luminosities emitted from the high altitudes in the gaps, and maximum heating luminosities produced by positrons returning from the elevated pair fronts. The estimated theoretical high-energy luminosities are in good agreement with the corresponding empirical relationships for gamma-ray pulsars. We illustrate the results of our modeling of the pair cascades and gamma-ray emission from the high altitudes in the SG for the Crab pulsar. The combination of the frame-dragging field and high-altitude SG emission enables both acceleration at the smaller

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

    SciTech Connect

    Lacki, Brian C.; Thompson, Todd A.

    2013-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Lacki, Brian C.; Thompson, Todd A.

    2013-01-01

    The origin of the diffuse hard X-ray (2-10 keV) emission from starburst galaxies is a long-standing problem. We suggest that synchrotron emission of 10-100 TeV electrons and positrons (e ±) can contribute to this emission, because starbursts have strong magnetic fields. We consider three sources of e ± at these energies: (1) primary electrons directly accelerated by supernova remnants, (2) pionic secondary e ± created by inelastic collisions between cosmic ray (CR) protons and gas nuclei in the dense interstellar medium of starbursts, and (3) pair e ± produced between the interactions between 10 and 100 TeV γ-rays and the intense far-infrared (FIR) radiation fields of starbursts. We create one-zone steady-state models of the CR population in the Galactic center (R <= 112 pc), NGC 253, M82, and Arp 220's nuclei, assuming a power-law injection spectrum for electrons and protons. We consider different injection spectral slopes, magnetic field strengths, CR acceleration efficiencies, and diffusive escape times, and include advective escape, radiative cooling processes, and secondary and pair e ±. We compare these models to extant radio and GeV and TeV γ-ray data for these starbursts, and calculate the diffuse synchrotron X-ray and inverse Compton (IC) luminosities of these starbursts in the models which satisfy multiwavelength constraints. If the primary electron spectrum extends to ~PeV energies and has a proton/electron injection ratio similar to the Galactic value, we find that synchrotron emission contributes 2%-20% of their unresolved, diffuse hard X-ray emission. However, there is great uncertainty in this conclusion because of the limited information on the CR electron spectrum at these high energies. IC emission is likewise a minority of the unresolved X-ray emission in these starbursts, from 0.1% in the Galactic center to 10% in Arp 220's nuclei, with the main uncertainty being the starbursts' magnetic field. We also model generic starbursts, including

  2. CONSTRAINING THE HIGH-ENERGY EMISSION FROM GAMMA-RAY BURSTS WITH FERMI

    SciTech Connect

    Ackermann, M.; Ajello, M.; Bechtol, K.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Buehler, R.; Cameron, R. A.; Charles, E.; Baldini, L.; Bellazzini, R.; Barbiellini, G.; Baring, M. G.; Bonamente, E.; Cecchi, C.; Bouvier, A.; Brigida, M.; Buson, S.; Caliandro, G. A. E-mail: kocevski@slac.stanford.edu E-mail: connauv@uah.edu E-mail: michael.briggs@nasa.gov; Collaboration: Fermi Large Area Telescope Team; Fermi Gamma-ray Burst Monitor Team; and others

    2012-08-01

    We examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the {nu}F{sub {nu}} spectra (E{sub pk}). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E{sub pk} than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to {gamma}{gamma} attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

  3. Constraining the High-Energy Emission from Gamma-Ray Bursts with Fermi

    NASA Technical Reports Server (NTRS)

    Gehrels, Neil; Harding, A. K.; Hays, E.; Racusin, J. L.; Sonbas, E.; Stamatikos, M.; Guirec, S.

    2012-01-01

    We examine 288 GRBs detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field-of-view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the nuF(sub v) spectra (E(sub pk)). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E(sub pk) than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cut-off in their high-energy spectra, which if assumed to be due to gamma gamma attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

  4. Unraveling the high and very-high energy emission components of LS 5039

    NASA Astrophysics Data System (ADS)

    Zabalza, Víctor; Bosch-Ramon, Valentí; Aharonian, Felix A.

    2012-12-01

    Since the detection of gamma-ray binaries in the GeV range with Fermi, the GeV and TeV spectra of these systems have challenged our picture of their high-energy emission. The exponential cutoff at a few GeV, combined with the hard spectrum at TeV and the anticorrelation between the two bands, points towards two different origins for the GeV and TeV emission from LS 5039 and LS I +61 303. If these systems are powered by a young pulsar, one of the locations could be the apex of the contact discontinuity between the pulsar and stellar winds, located between the pulsar and the star. This location is a good candidate for emission of the GeV component, but the strong photon field density from the star makes it an unsuitable TeV emitter owing to pair production opacity. However, the rotation of the pulsar around the star gives rise to a bending of the wind interaction region by Coriolis forces at distances larger than the size of the binary system. We show that the particles accelerated in the pulsar wind shock at this location could be responsible for the TeV component in gamma-ray binaries. The spectral and lightcurve resulting from this simple two-emitter model match satisfactorily the Fermi and HESS observations of LS 5039, and provide a starting point for a future broadband analysis, from radio to TeV, of the properties of the system.

  5. Constraining the High-energy Emission from Gamma-Ray Bursts with Fermi

    NASA Astrophysics Data System (ADS)

    Fermi Large Area Telescope Team; Ackermann, M.; Ajello, M.; Baldini, L.; Barbiellini, G.; Baring, M. G.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bouvier, A.; Brigida, M.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cutini, S.; D'Ammando, F.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Granot, J.; Grenier, I. A.; Grove, J. E.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hays, E.; Horan, D.; Jóhannesson, G.; Kataoka, J.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McEnery, J.; McGlynn, S.; Michelson, P. F.; Mitthumsiri, W.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Norris, J. P.; Nuss, E.; Nymark, T.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Racusin, J. L.; Rainò, S.; Rando, R.; Razzaque, S.; Reimer, A.; Reimer, O.; Ritz, S.; Ryde, F.; Sgrò, C.; Siskind, E. J.; Sonbas, E.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Stawarz, Łukasz; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Uehara, T.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Fermi Gamma-ray Burst Monitor Team; Connaughton, V.; Briggs, M. S.; Guirec, S.; Goldstein, A.; Burgess, J. M.; Bhat, P. N.; Bissaldi, E.; Camero-Arranz, A.; Fishman, J.; Fitzpatrick, G.; Foley, S.; Gruber, D.; Jenke, P.; Kippen, R. M.; Kouveliotou, C.; McBreen, S.; Meegan, C.; Paciesas, W. S.; Preece, R.; Rau, A.; Tierney, D.; van der Horst, A. J.; von Kienlin, A.; Wilson-Hodge, C.; Xiong, S.

    2012-08-01

    We examine 288 gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field of view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the νF ν spectra (E pk). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E pk than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cutoff in their high-energy spectra, which if assumed to be due to γγ attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

  6. High-energy emissions from the gamma-ray binary LS 5039

    SciTech Connect

    Takata, J.; Leung, Gene C. K.; Cheng, K. S.; Tam, P. H. T.; Kong, A. K. H.; Hui, C. Y. E-mail: gene930@connect.hku.hk

    2014-07-20

    We study mechanisms of multi-wavelength emissions (X-ray, GeV, and TeV gamma-rays) from the gamma-ray binary LS 5039. This paper is composed of two parts. In the first part, we report on results of observational analysis using 4 yr data of the Fermi Large Area Telescope. Due to the improvement of instrumental response function and increase of the statistics, the observational uncertainties of the spectrum in the ∼100-300 MeV bands and >10 GeV bands are significantly improved. The present data analysis suggests that the 0.1-100 GeV emissions from LS 5039 contain three different components: (1) the first component contributes to <1 GeV emissions around superior conjunction, (2) the second component dominates in the 1-10 GeV energy bands, and (3) the third component is compatible with the lower-energy tail of the TeV emissions. In the second part, we develop an emission model to explain the properties of the phase-resolved emissions in multi-wavelength observations. Assuming that LS 5039 includes a pulsar, we argue that emissions from both the magnetospheric outer gap and the inverse-Compton scattering process of cold-relativistic pulsar wind contribute to the observed GeV emissions. We assume that the pulsar is wrapped by two kinds of termination shock: Shock-I due to the interaction between the pulsar wind and the stellar wind and Shock-II due to the effect of the orbital motion. We propose that the X-rays are produced by the synchrotron radiation at the Shock-I region and the TeV gamma-rays are produced by the inverse-Compton scattering process at the Shock-II region.

  7. The LAGO Collaboration: Searching for high energy GRB emissions in Latin America

    NASA Astrophysics Data System (ADS)

    Barros, H.; Lago Collaboration

    2012-02-01

    During more than a decade Gamma Ray Bursts (GRB a cosmological phenomena of tremendous power) have been extensively studied in the keV - MeV energy range. However, the higher energy emission still remains a mystery. The Large Aperture GRB Observatory (L.A.G.O.) is an international collaboration started in 2005 aiming at a better understanding of the GRB by studying their emission at high energies (> 1 GeV), where the fluxes are low and measurements by satellites are difficult. This is done using the Single Particle Technique, by means of ground-based Water Cherenkov Detectors (WCD) at sites of high altitude. At those altitudes it is possible to detect air showers produced by high energy photons from the GRB, i. e. a higher rate of events on a short time scale, of the order of the second. The Pierre Auger Observatory could detect such GRB given its large number of detectors, but at 1400 m.a.s.l. the expected signal is quite small. At higher altitudes, similar performance is expected with only a very small number of WCD. As of 2011, high altitude WCD are in operation at Sierra Negra (Mexico, 4650 m.a.s.l.), Chacaltaya (Bolivia, 5200 m.a.s.l.), Maracapomacocha (Peru, 4200 m.a.s.l.), and new WCDs are being installed in Venezuela (Pico Espejo, 4750 m.a.s.l.), Argentina, Brazil, Chile, Colombia and Guatemala. Most of the new WCDs will not be at high enough altitude to detect GRB, never the less it will allow obtaining valuable measurements of secondaries at ground level, which are relevant for solar physics. The LAGO sensitivity to GRB is determined from simulations (under a sudden increase of 1 GeV - 1 TeV photons from a GRB) of the gamma initiated particle shower in the atmosphere and the WCD response to secondaries. We report on WDC calibration and operation at high altitude, GRB detectability, background rates, search for bursts in several months of preliminary data, as well as search for signals at ground level when satellite burst is reported, all these show the

  8. THE VERY HIGH ENERGY EMISSION FROM PULSARS: A CASE FOR INVERSE COMPTON SCATTERING

    SciTech Connect

    Lyutikov, Maxim; Otte, Nepomuk; McCann, Andrew

    2012-07-20

    The observations of gamma-ray emission from pulsars with the Fermi-LAT detector and the detection of the Crab pulsar with the VERITAS array of Cherenkov telescopes at energies above 100 GeV make it unlikely that curvature radiation is the main source of photons above GeV energies in the Crab and many other pulsars. We outline a model in which the broad UV-X-ray component and the very high energy {gamma}-ray emission of pulsars are explained within the synchrotron self-Compton framework. We argue that the bulk of the observed radiation is generated by the secondary plasma, which is produced in cascades in the outer gaps of the magnetosphere. We find that the inverse Compton (IC) scattering occurs in the Klein-Nishina regime, which favors synchrotron photons in the UV band as target field for the scattering process. The primary beam is accelerated in a modest electric field, with a field strength that is of the order of a few percent of the magnetic field near the light cylinder. Overall, for IC scattering occurring in the Klein-Nishina regime, the particle distribution in the gap does not evolve toward a stationary distribution and thus is intrinsically time-dependent. We point out that in a radiation reaction-limited regime of particle acceleration the gamma-ray luminosity L{sub {gamma}} scales linearly with the pulsar spin-down power E-dot , L{sub {gamma}}{proportional_to} E-dot , and not proportional to {radical}( E-dot ) as expected from potential-limited acceleration.

  9. VERY HIGH ENERGY {gamma}-RAY EMISSION FROM PASSIVE SUPERMASSIVE BLACK HOLES: CONSTRAINTS FOR NGC 1399

    SciTech Connect

    Pedaletti, G.; Wagner, S. J.; Rieger, F. M.

    2011-09-10

    Very high energy (VHE, >100 GeV) {gamma}-rays are expected to be emitted from the vicinity of supermassive black holes (SMBHs), irrespective of their activity state. In the magnetosphere of rotating SMBH, efficient acceleration of charged particles can take place through various processes. These particles could reach energies up to E {approx} 10{sup 19} eV. VHE {gamma}-ray emission from these particles is then feasible via leptonic or hadronic processes. Therefore, passive systems, where the lack of a strong photon field allows the VHE {gamma}-rays to escape, are expected to be detected by Cherenkov telescopes. We present results from recent VHE experiments on the passive SMBH in the nearby elliptical galaxy NGC 1399. No {gamma}-ray signal has been found, neither by the H.E.S.S. experiment nor in the Fermi data analyzed here. We discuss possible implications for the physical characteristics of the system. We conclude that in a scenario where particles are accelerated in vacuum gaps in the magnetosphere, only a fraction {approx}0.3 of the gap is available for particle acceleration, indicating that the system is unlikely to be able to accelerate protons up to E {approx} 10{sup 19} eV.

  10. Effects of high energy radiation on the mechanical properties of epoxy-graphite fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Fornes, R. E.; Gilbert, R. D.; Memory, J. D.

    1984-01-01

    The effects of high energy radiation on the mechanical properties and on the molecular and structural properties of graphite fiber reinforced composites were assessed so that the durability of such composites in space applications could be predicted. Investigative techniques including ESR and infrared spectroscopy, ESCA, contact angle measurements, and dynamic and static mechanical testing (3-point bending and interlaminar shear) were employed. The results using these different techniques are individually described, and the implications of the data are discussed. The proposed plan of work for the next fiscal year is outlined.

  11. NuSTAR Detection of High-energy X-Ray Emission and Rapid Variability from Sagittarius Asstarf Flares

    NASA Astrophysics Data System (ADS)

    Barrière, Nicolas M.; Tomsick, John A.; Baganoff, Frederick K.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Dexter, Jason; Grefenstette, Brian; Hailey, Charles J.; Harrison, Fiona A.; Madsen, Kristin K.; Mori, Kaya; Stern, Daniel; Zhang, William W.; Zhang, Shuo; Zoglauer, Andreas

    2014-05-01

    Sagittarius Asstarf harbors the supermassive black hole that lies at the dynamical center of our Galaxy. Sagittarius Asstarf spends most of its time in a low luminosity emission state but flares frequently in the infrared and X-ray, increasing up to a few hundred fold in brightness for up to a few hours at a time. The physical processes giving rise to the X-ray flares are uncertain. Here we report the detection with the NuSTAR observatory in Summer and Fall 2012 of four low to medium amplitude X-ray flares to energies up to 79 keV. For the first time, we clearly see that the power-law spectrum of Sagittarius Asstarf X-ray flares extends to high energy, with no evidence for a cutoff. Although the photon index of the absorbed power-law fits are in agreement with past observations, we find a difference between the photon index of two of the flares (significant at the 95% confidence level). The spectra of the two brightest flares (~55 times quiescence in the 2-10 keV band) are compared to simple physical models in an attempt to identify the main X-ray emission mechanism, but the data do not allow us to significantly discriminate between them. However, we confirm the previous finding that the parameters obtained with synchrotron models are, for the X-ray emission, physically more reasonable than those obtained with inverse Compton models. One flare exhibits large and rapid (<100 s) variability, which, considering the total energy radiated, constrains the location of the flaring region to be within ~10 Schwarzschild radii of the black hole.

  12. The High-energy Continuum Emission of the Gamma-Ray Blazar PKS 0528+134

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita M.; Urry, C. Megan; Maraschi, L.; Ghisellini, G.; Mukherjee, R.; Pesce, Joseph E.; Wagner, S. J.; Wehrle, A. E.; Hartman, R. C.; Lin, Y. C.; VonMintigny, C.

    1997-01-01

    We present Advanced Satellite for Cosmology and Astrophysics (ASCA) observations of the gamma-ray blazar PKS 0528 + 134, obtained at two separate epochs in 1994 August and 1995 March. These data represent the first measurement of the X-ray continuum emission of this source in the medium-hard X-ray band. Both ASCA spectra are consistent with a single power law with photon index GAMMA approx. = 1.7-1.8 and column density N(sub H) approx. = 5 x 10(exp 21)/ sq cm, higher than Galactic. The X-ray flux increased by a factor of 4 in approx. 7 months without appreciable change of the spectral shape. During the lower state of 1994 August, PKS 0528 + 134 was observed simultaneously in the optical, X-rays, and at gamma-ray energies with Energetic Gamma Ray Experiment Telescope (EGRET). The gamma-ray intensity is the faintest detected thus far in the source, with a steep spectrum (GAMMA approx. = 2.7). The extrapolation of the X-ray continuum to the gamma-ray range requires a sharp spectral break at approx. 10(exp 22) Hz. We discuss the radio through gamma-ray spectral energy distribution of PKS 0528 + 134, comparing the low state of 1994 August with the flare state of 1993 March. We show that in PKS 0528 + 134, a non-negligible contribution from the external radiation field is present and that, although synchrotron self-Compton scenarios cannot be ruled out, inverse Compton upscattering of thermal seed photons may be the dominant cooling process for the production of the high-energy continuum in this blazar.

  13. The High-Energy Continuum Emission of the Gamma-Ray Blazar PKS 0528+134

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita M.; Urry, C. Megan; Maraschi, L.; Ghisellini, G.; Mukherjee, R.; Pesce, Joseph E.; Wagner, S. J.; Wehrle, A. E.; Hartman, R. C.; Lin, Y. C.

    1997-01-01

    We present Advanced Satellite for Cosmology and Astrophysics (ASCA) observations of the gamma-ray blazar PKS 0528 + 134, obtained at two separate epochs in 1994 August and 1995 March. These data represent the first measurement of the X-ray continuum emission of this source in the medium-hard X-ray band. Both ASCA spectra are consistent with a single power law with photon index GAMMA approximate 1.7-1.8 and column density N(sub H) approximately 5 x 10(exp 21) /sq cm, higher than Galactic. The X-ray flux increased by a factor of 4 in approximately 7 months without appreciable change of the spectral shape. During the lower state of 1994 August, PKS 0528 + 134 was observed simultaneously in the optical, X-rays, and at gamma-ray energies with EGRET. The gamma-ray intensity is the faintest detected thus far in the source, with a steep spectrum (GAMMA approximately 2.7). The extrapolation of the X-ray continuum to the gamma-ray range requires a sharp spectral break at approximately 10(exp 22) Hz. We discuss the radio through gamma-ray spectral energy distribution of PKS 0528 + 134, comparing the low state of 1994 August with the flare state of 1993 March. We show that in PKS 0528 + 134, a non-negligible contribution from the external radiation field is present and that, although synchrotron self-Compton scenarios cannot be ruled out, inverse Compton upscattering of thermal seed photons may be the dominant cooling process for the production of the high-energy continuum in this blazar.

  14. POWERFUL HIGH-ENERGY EMISSION OF THE REMARKABLE BL Lac OBJECT S5 0716+714

    SciTech Connect

    Vittorini, V.; Chen, A. W.; Ferrari, A.; Tavani, M.; D'Ammando, F.; Donnarumma, I.; Pacciani, L.; Pucella, G.; Bulgarelli, A.; Colafrancesco, S.; Giommi, P.

    2009-12-01

    BL Lac objects of the intermediate subclass (IBLs) are known to emit a substantial fraction of their power in the energy range 0.1-10 GeV. Detecting gamma-ray emission from such sources provides therefore a direct probe of the emission mechanisms and of the underlying powerhouse. The gamma-ray satellite, AGILE, detected the remarkable IBL S5 0716+714 (z approx = 0.3) during a high state in the period from 2007 September-October, marked by two very intense flares reaching peak fluxes of 200 x 10{sup -8} photons cm{sup -2} s{sup -1} above 100 MeV, with simultaneous optical and X-ray observations. We present here a theoretical model for the two major flares and discuss the overall energetics of the source. We conclude that 0716+714 is among the brightest BL Lac's ever detected at gamma-ray energies. Because of its high power and lack of signs for ongoing accretion or surrounding gas, the source is an ideal candidate to test the maximal power extractable from a rotating supermassive black hole via the pure Blandford-Znajek (BZ) mechanism. We find that during the 2007 gamma-ray flares 0716+714 approached or just exceeded the upper limit set by BZ for a black hole of mass 10{sup 9} M{sub sun}.

  15. Very-high-energy gamma-ray emission from the direction of the Galactic globular cluster Terzan 5

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Barnacka, A.; Barres de Almeida, U.; Becherini, Y.; Becker, J.; Behera, B.; Bernlöhr, K.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Büsching, I.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Chounet, L.-M.; Clapson, A. C.; Coignet, G.; Cologna, G.; Conrad, J.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubois, F.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gallant, Y. A.; Gast, H.; Gérard, L.; Gerbig, D.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Goret, P.; Göring, D.; Häffner, S.; Hague, J. D.; Hampf, D.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hoffmann, A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Keogh, D.; Khangulyan, D.; Khélifi, B.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Laffon, H.; Lamanna, G.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, D.; Maxted, N.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Moderski, R.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; de Oña Wilhelmi, D.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Paz Arribas, M.; Pedaletti, G.; Pelletier, G.; Petrucci, P.-O.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Rayner, S. M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Ruppel, J.; Ryde, F.; Sahakian, V.; Santangelo, A.; Schlickeiser, R.; Schöck, F. M.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sikora, M.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Vialle, J. P.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2011-07-01

    The HESS very-high-energy (VHE, E > 0.1 TeV) gamma-ray telescope system has discovered a new source, HESS J1747-248. The measured integral flux is (1.2 ± 0.3) × 10-12 cm-2 s-1 above 440 GeV for a power-law photon spectral index of 2.5 ± 0.3stat ± 0.2sys. The VHE gamma-ray source is located in the close vicinity of the Galactic globular cluster Terzan 5 and extends beyond the HESS point spread function (0.07°). The probability of a chance coincidence with Terzan 5 and an unrelated VHE source is quite low (~10-4). With the largest population of identified millisecond pulsars (msPSRs), a very high core stellar density and the brightest GeV range flux as measured by Fermi-LAT, Terzan 5 stands out among Galactic globular clusters. The properties of the VHE source are briefly discussed in the context of potential emission mechanisms, notably in relation to msPSRs. Interpretation of the available data accommodates several possible origins for this VHE gamma-ray source, although none of them offers a satisfying explanation of its peculiar morphology.

  16. Tracing High-Energy Radiation from T Tauri Stars Using Mid-Infrared Neon Emission from Disks

    NASA Astrophysics Data System (ADS)

    Espaillat, Catherine

    2013-01-01

    High-energy radiation from T Tauri stars (TTS) influences the amount and longevity of gas in disks, thereby playing a crucial role in the creation of gas giant planets. Here we probe the high-energy ionizing radiation from TTS using mid-infrared (MIR) Spitzer IRS Neon forbidden line detections in a sample of disks from I 348, NG 2068, and Chamaeleon. We report three new detections of [Ne III] and use their [Ne III]/[Ne II] ratios in conjunction with X-ray emission measurements to probe Extreme-Ultraviolet (EUV) radiation from TTS. We report the first observational evidence for EUV dominated heating in a T Tauri disk: [Ne III]/[Ne II] ~ 1. Our results provide a unique insight into the EUV emission from TTS.

  17. THE LONG AND THE SHORT OF THE HIGH-ENERGY EMISSION IN GRB090926A: AN EXTERNAL SHOCK

    SciTech Connect

    Sacahui, J. R.; Fraija, N.; Gonzalez, M. M.; Lee, W. H. E-mail: nifraija@astro.unam.mx E-mail: wlee@astro.unam.mx

    2012-08-20

    Synchrotron self-Compton (SSC) emission from a reverse shock has been suggested as the origin for the high-energy component lasting 2 s in the prompt phase of GRB98080923. The model describes spectral indices, fluxes, and the duration of the high-energy component as well as a long keV tail present in the prompt phase of GRB980923. Here, we present an extension of this model to describe the high-energy emission of GRB090926A. We argue that the emission consists of two components, one with a duration less than 1 s during the prompt phase, and a second, longer-lasting GeV phase lasting hundred of seconds after the prompt phase. The short high-energy phase can be described as SSC emission from a reverse shock similar to that observed in GRB980923, while the longer component arises from the forward shock. The main assumption is that the jet is magnetized and evolves in the thick-shell case, and the calculated fluxes and break energies are all consistent with the observed values. A comparison between the resulting parameters obtained for GRB980923 and GRB090926A suggests differences in burst tails that could be attributable to the circumburst medium, and this could account for previous analyses reported in the literature for other bursts. We find that the density of the surrounding medium inferred from the observed values associated with the forward shock agrees with standard values for host galaxies such as the one associated with GRB090926A.

  18. Effects of high energy radiation on the mechanical properties of epoxy/graphite fiber composites

    NASA Technical Reports Server (NTRS)

    Fornes, R. E.; Memory, J. D.

    1981-01-01

    Studies on the effects of high energy radiation on graphite fiber reinforced composites are summarized. Studies of T300/5208 and C6000/PMR15 composites, T300 fibers and the resin system MY720/DDS (tetraglycidyl-4,4'-diaminodiphenyl methane cured with diaminodiphenyl sulfone) are included. Radiation dose levels up to 8000 Mrads were obtained with no deleterious effects on the breaking stress or modulus. The effects on the structure and morphology were investigated using mechanical tests, electron spin resonance, X-ray diffraction, and electron spectroscopy for chemical analysis (ESCA or X-ray photoelectron spectroscopy). Details of the experiments and results are given. Studies of the fracture surfaces of irradiated samples were studied with scanning electron microscopy; current results indicate no differences in the morphology of irradiated and control samples.

  19. The slingshot effect: A possible new laser-driven high energy acceleration mechanism for electrons

    SciTech Connect

    Fiore, Gaetano; Fedele, Renato; Angelis, Umberto de

    2014-11-15

    We show that under appropriate conditions the impact of a very short and intense laser pulse onto a plasma causes the expulsion of surface electrons with high energy in the direction opposite to the one of the propagations of the pulse. This is due to the combined effects of the ponderomotive force and the huge longitudinal field arising from charge separation (“slingshot effect”). The effect should also be present with other states of matter, provided the pulse is sufficiently intense to locally cause complete ionization. An experimental test seems to be feasible and, if confirmed, would provide a new extraction and acceleration mechanism for electrons, alternative to traditional radio-frequency-based or laser-wake-field ones.

  20. Detection of High-energy Gamma-Ray Emission During the X-Ray Flaring Activity in GRB 100728A

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bhat, P. N.; Bissaldi, E.; Blandford, R. D.; Bonamente, E.; Bonnell, J.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Connaughton, V.; Conrad, J.; Cutini, S.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Favuzzi, C.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Granot, J.; Grenier, I. A.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Longo, F.; Loparco, F.; Lott, B.; Lubrano, P.; Mazziotta, M. N.; McEnery, J. E.; Mészáros, P.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Paciesas, W. S.; Pelassa, V.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Porter, T. A.; Racusin, J. L.; Rainò, S.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Reyes, L. C.; Roth, M.; Sadrozinski, H. F.-W.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Sonbas, E.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Strickman, M. S.; Takahashi, H.; Tanaka, T.; Tanaka, Y.; Thayer, J. G.; Thayer, J. B.; Torres, D. F.; Tosti, G.; Troja, E.; Uehara, T.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vilchez, N.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yamazaki, R.; Yang, Z.; Ziegler, M.; Piro, L.

    2011-06-01

    We present the simultaneous Swift and Fermi observations of the bright GRB 100728A and its afterglow. The early X-ray emission is dominated by a vigorous flaring activity continuing until 1 ks after the burst. In the same time interval, high-energy emission is significantly detected by the Fermi/Large Area Telescope. Marginal evidence of GeV emission is observed up to later times. We discuss the broadband properties of this burst within both the internal and external shock scenarios, with a particular emphasis on the relation between X-ray flares, the GeV emission, and a continued long-duration central engine activity as their power source.

  1. HEAO 1 observations of high-energy X-rays from 3C273. [quasar emissions

    NASA Technical Reports Server (NTRS)

    Primini, F. A.; Cooke, B. A.; Dobson, C. A.; Howe, S. K.; Scheepmaker, A.; Wheaton, W. A.; Lewin, W. H. G.; Baity, W. A.; Gruber, D. E.; Matteson, J. L.

    1979-01-01

    The first detection of high energy (13 to 120 keV) X rays from the quasar 3C273, made by the HEAO 1 satellite, is reported. Observations were made with the 13 to 180 keV slat collimated detectors of the high energy X-ray and low energy gamma-ray (A4) experiment during December 1977-January 1978 and June-July 1978. Results are consistent with the previously observed X-ray flux variability on a scale of months. Photon count rates are presented for each of five energy bands and count rate and photon spectra for the June through July 1978 observations are derived. A comparison of the data obtained with that at lower X-ray energies and higher gamma-ray energies indicates that there is an overall spectral steepening from low to high energies and a possible break near 20 keV, which may be due to the gamma rays originating from a different region than that of the X rays.

  2. Tracing High-energy Radiation from T Tauri Stars Using Mid-infrared Neon Emission from Disks

    NASA Astrophysics Data System (ADS)

    Espaillat, C.; Ingleby, L.; Furlan, E.; McClure, M.; Spatzier, A.; Nieusma, J.; Calvet, N.; Bergin, E.; Hartmann, L.; Miller, J. M.; Muzerolle, J.

    2013-01-01

    High-energy radiation from T Tauri stars (TTS) influences the amount and longevity of gas in disks, thereby playing a crucial role in the creation of gas giant planets. Here we probe the high-energy ionizing radiation from TTS using high-resolution mid-infrared (MIR) Spitzer Infrared Spectrograph neon forbidden line detections in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We report three new detections of [Ne III] from CS Cha, SZ Cha, and T 54, doubling the known number of [Ne III] detections from TTS. Using [Ne III]-to-[Ne II] ratios in conjunction with X-ray emission measurements, we probe high-energy radiation from TTS. The majority of previously inferred [Ne III]/[Ne II] ratios based on [Ne III] line upper limits are significantly less than 1, pointing to the dominance of either X-ray radiation or soft extreme-ultraviolet (EUV) radiation in producing these lines. Here we report the first observational evidence for hard EUV-dominated Ne forbidden line production in a T Tauri disk: [Ne III]/[Ne II] ~ 1 in SZ Cha. Our results provide a unique insight into the EUV emission from TTS, by suggesting that EUV radiation may dominate the creation of Ne forbidden lines, albeit in a minority of cases.

  3. TRACING HIGH-ENERGY RADIATION FROM T TAURI STARS USING MID-INFRARED NEON EMISSION FROM DISKS

    SciTech Connect

    Espaillat, C.; Ingleby, L.; McClure, M.; Nieusma, J.; Calvet, N.; Bergin, E.; Hartmann, L.; Miller, J. M. E-mail: lingleby@umich.edu E-mail: jdnieusma@gmail.com E-mail: ebergin@umich.edu; and others

    2013-01-01

    High-energy radiation from T Tauri stars (TTS) influences the amount and longevity of gas in disks, thereby playing a crucial role in the creation of gas giant planets. Here we probe the high-energy ionizing radiation from TTS using high-resolution mid-infrared (MIR) Spitzer Infrared Spectrograph neon forbidden line detections in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We report three new detections of [Ne III] from CS Cha, SZ Cha, and T 54, doubling the known number of [Ne III] detections from TTS. Using [Ne III]-to-[Ne II] ratios in conjunction with X-ray emission measurements, we probe high-energy radiation from TTS. The majority of previously inferred [Ne III]/[Ne II] ratios based on [Ne III] line upper limits are significantly less than 1, pointing to the dominance of either X-ray radiation or soft extreme-ultraviolet (EUV) radiation in producing these lines. Here we report the first observational evidence for hard EUV-dominated Ne forbidden line production in a T Tauri disk: [Ne III]/[Ne II] {approx} 1 in SZ Cha. Our results provide a unique insight into the EUV emission from TTS, by suggesting that EUV radiation may dominate the creation of Ne forbidden lines, albeit in a minority of cases.

  4. Variable very-high-energy gamma-ray emission from the microquasar LS I +61 303.

    PubMed

    Albert, J; Aliu, E; Anderhub, H; Antoranz, P; Armada, A; Asensio, M; Baixeras, C; Barrio, J A; Bartelt, M; Bartko, H; Bastieri, D; Bavikadi, S R; Bednarek, W; Berger, K; Bigongiari, C; Biland, A; Bisesi, E; Bock, R K; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Ciprini, S; Coarasa, J A; Commichau, S; Contreras, J L; Cortina, J; Curtef, V; Danielyan, V; Dazzi, F; De Angelis, A; de Los Reyes, R; De Lotto, B; Domingo-Santamaría, E; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernández, E; Firpo, R; Flix, J; Fonseca, M V; Font, L; Fuchs, M; Galante, N; Garczarczyk, M; Gaug, M; Giller, M; Goebel, F; Hakobyan, D; Hayashida, M; Hengstebeck, T; Höhne, D; Hose, J; Hsu, C C; Isar, P G; Jacon, P; Kalekin, O; Kosyra, R; Kranich, D; Laatiaoui, M; Laille, A; Lenisa, T; Liebing, P; Lindfors, E; Lombardi, S; Longo, F; López, J; López, M; Lorenz, E; Lucarelli, F; Majumdar, P; Maneva, G; Mannheim, K; Mansutti, O; Mariotti, M; Martínez, M; Mase, K; Mazin, D; Merck, C; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Mizobuchi, S; Moralejo, A; Nilsson, K; Oña-Wilhelmi, E; Orduña, R; Otte, N; Oya, I; Paneque, D; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pavel, N; Pegna, R; Persic, M; Peruzzo, L; Piccioli, A; Poller, M; Pooley, G; Prandini, E; Raymers, A; Rhode, W; Ribó, M; Rico, J; Riegel, B; Rissi, M; Robert, A; Romero, G E; Rügamer, S; Saggion, A; Sánchez, A; Sartori, P; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Shore, S N; Sidro, N; Sillanpää, A; Sobczynska, D; Stamerra, A; Stark, L S; Takalo, L; Temnikov, P; Tescaro, D; Teshima, M; Tonello, N; Torres, A; Torres, D F; Turini, N; Vankov, H; Vitale, V; Wagner, R M; Wibig, T; Wittek, W; Zanin, R; Zapatero, J

    2006-06-23

    Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I 61 + 303. Six orbital cycles were recorded. Several detections occur at a similar orbital phase, which suggests that the emission is periodic. The strongest gamma-ray emission is not observed when the two stars are closest to one another, implying a strong orbital modulation of the emission or absorption processes. PMID:16709745

  5. EGRET upper limits to the high-energy gamma-ray emission from the millisecond pulsars in nearby globular clusters

    NASA Technical Reports Server (NTRS)

    Michelson, P. F.; Bertsch, D. L.; Brazier, K.; Chiang, J.; Dingus, B. L.; Fichtel, C. E.; Fierro, J.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.

    1994-01-01

    We report upper limits to the high-energy gamma-ray emission from the millisecond pulsars (MSPs) in a number of globular clusters. The observations were done as part of an all-sky survey by the energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) during Phase I of the CGRO mission (1991 June to 1992 November). Several theoretical models suggest that MSPs may be sources of high-energy gamma radiation emitted either as primary radiation from the pulsar magnetosphere or as secondary radiation generated by conversion into photons of a substantial part of the relativistic e(+/-) pair wind expected to flow from the pulsar. To date, no high-energy emission has been detected from an individual MSP. However, a large number of MSPs are expected in globular cluster cores where the formation rate of accreting binary systems is high. Model predictions of the total number of pulsars range in the hundreds for some clusters. These expectations have been reinforced by recent discoveries of a substantial number of radio MSPs in several clusters; for example, 11 have been found in 47 Tucanae (Manchester et al.). The EGRET observations have been used to obtain upper limits for the efficiency eta of conversion of MSP spin-down power into hard gamma rays. The upper limits are also compared with the gamma-ray fluxes predicted from theoretical models of pulsar wind emission (Tavani). The EGRET limits put significant constraints on either the emission models or the number of pulsars in the globular clusters.

  6. Towards an effective nonlinear Quantum Mechanics for High Energy-density (HED) Matter

    NASA Astrophysics Data System (ADS)

    Mahajan, Swadesh

    2015-11-01

    A relativistic quantum framework is presented for dealing with high energy density matter, in particular, an assembly of particles in the field of an electromagnetic (EM) wave of arbitrary magnitude. Two different approaches are presented: 1) A Statistical Mechanical model for the HED matter is developed - Principal steps involve solving the eigenvalue problem for a quantum relativistic particle in the presence of arbitrary strength EM field. The resulting energy eigenvalue (dependent on the magnitudes A, ω and k) defines the appropriate Boltzmann factor to construct expressions for physical variables for a weakly interacting system of these field-dressed particles. The fluid equations are the conservation laws, 2) Second, an equivalent nonlinear quantum mechanics is constructed to represent a hot fluid with and without internal degrees of freedom (like spin). Representative initial results are displayed and discussed: 1) fundamental changes in the particle energy momentum relationship 2) The EM wave induces anisotropy in the energy momentum tensor, 3) the EM wave splits the spin-degenerate states, 4) the propagation characteristics of the EM wave are modified by thermal and field effects causing differential self-induced transparency, 5) Particle trapping and ``pushing'' by the high amplitude EM wave. Attempts will be made to highlight testable predictions. Research supported by the U.S. Dept. of Energy Grant DE-FG02-04ER-54742.

  7. Temporalization of peak electric generation particulate matter emissions during high energy demand days.

    PubMed

    Farkas, Caroline M; Moeller, Michael D; Felder, Frank A; Baker, Kirk R; Rodgers, Mark; Carlton, Annmarie G

    2015-04-01

    Underprediction of peak ambient pollution by air quality models hinders development of effective strategies to protect health and welfare. The U.S. Environmental Protection Agency's community multiscale air quality (CMAQ) model routinely underpredicts peak ozone and fine particulate matter (PM2.5) concentrations. Temporal misallocation of electricity sector emissions contributes to this modeling deficiency. Hourly emissions are created for CMAQ by use of temporal profiles applied to annual emission totals unless a source is matched to a continuous emissions monitor (CEM) in the National Emissions Inventory (NEI). More than 53% of CEMs in the Pennsylvania-New Jersey-Maryland (PJM) electricity market and 45% nationally are unmatched in the 2008 NEI. For July 2006, a United States heat wave with high electricity demand, peak electric sector emissions, and elevated ambient PM2.5 mass, we match hourly emissions for 267 CEM/NEI pairs in PJM (approximately 49% and 12% of unmatched CEMs in PJM and nationwide) using state permits, electricity dispatch modeling and CEMs. Hourly emissions for individual facilities can differ up to 154% during the simulation when measurement data is used rather than default temporalization values. Maximum CMAQ PM2.5 mass, sulfate, and elemental carbon predictions increase up to 83%, 103%, and 310%, at the surface and 51%, 75%, and 38% aloft (800 mb), respectively. PMID:25705922

  8. Chemical and mechanical instabilities in high energy heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Gervino, G.; Lavagno, A.; Pigato, D.

    2015-07-01

    We investigate the possible thermodynamic instability in a warm and dense nuclear medium where a phase transition from nucleonic matter to resonance-dominated Δ-matter can take place. Such a phase transition is characterized by both mechanical instability (fluctuations on the baryon density) and by chemical-diffusive instability (fluctuations on the isospin concentration) in asymmetric nuclear matter. Similarly to the liquid-gas phase transition, the nucleonic and the Δ-matter phase have a different isospin density in the mixed phase. In the liquid-gas phase transition, the process of producing a larger neutron excess in the gas phase is referred to as isospin fractionation. A similar effects can occur in the nucleon-Δ matter phase transition due essentially to a Δ- excess in the Δ-matter phase in asymmetric nuclear matter. In this context, we study the hadronic equation of state by means of an effective quantum relativistic mean field model with the inclusion of the full octet of baryons, the Δ-isobar degrees of freedom, and the lightest pseudoscalar and vector mesons. Finally, we will investigate the presence of thermodynamic instabilities in a hot and dense nuclear medium where phases with different values of antibaryon-baryon ratios and strangeness content may coexist. Such a physical regime could be in principle investigated in the future high-energy compressed nuclear matter experiments where will make it possible to create compressed baryonic matter with a high net baryon density.

  9. FERMI OBSERVATIONS OF HIGH-ENERGY GAMMA-RAY EMISSION FROM GRB 080825C

    SciTech Connect

    Abdo, A. A.; Ackermann, M.; Bechtol, K.; Berenji, B.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bhat, P. N.; Bissaldi, E.; Bonamente, E. E-mail: j.granot@herts.ac.u

    2009-12-10

    The Fermi Gamma-ray Space Telescope has opened a new high-energy window in the study of gamma-ray bursts (GRBs). Here we present a thorough analysis of GRB 080825C, which triggered the Fermi Gamma-ray Burst Monitor (GBM), and was the first firm detection of a GRB by the Fermi Large Area Telescope (LAT). We discuss the LAT event selections, background estimation, significance calculations, and localization for Fermi GRBs in general and GRB 080825C in particular. We show the results of temporal and time-resolved spectral analysis of the GBM and LAT data. We also present some theoretical interpretation of GRB 080825C observations as well as some common features observed in other LAT GRBs.

  10. Fermi Observations of High-energy Gamma-ray Emission from GRB 080825C

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Band, D. L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bhat, P. N.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Briggs, M. S.; Brigida, M.; Bruel, P.; Burnett, T. H.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Chaplin, V.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cominsky, L. R.; Connaughton, V.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Gibby, L.; Giebels, B.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Goldstein, A.; Granot, J.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocevski, D.; Komin, N.; Kouveliotou, C.; Kuehn, F.; Kuss, M.; Latronico, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McBreen, S.; McEnery, J. E.; McGlynn, S.; Meegan, C.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paciesas, W. S.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Preece, R.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, O.; Reposeur, T.; Ritz, S.; Rochester, L. S.; Rodriguez, A. Y.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stamatikos, M.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; van der Horst, A. J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; von Kienlin, A.; Waite, A. P.; Wang, P.; Wilson-Hodge, C.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.

    2009-12-01

    The Fermi Gamma-ray Space Telescope has opened a new high-energy window in the study of gamma-ray bursts (GRBs). Here we present a thorough analysis of GRB 080825C, which triggered the Fermi Gamma-ray Burst Monitor (GBM), and was the first firm detection of a GRB by the Fermi Large Area Telescope (LAT). We discuss the LAT event selections, background estimation, significance calculations, and localization for Fermi GRBs in general and GRB 080825C in particular. We show the results of temporal and time-resolved spectral analysis of the GBM and LAT data. We also present some theoretical interpretation of GRB 080825C observations as well as some common features observed in other LAT GRBs.

  11. MAGIC upper limits on the Very High Energy emission from GRBs

    SciTech Connect

    Bastieri, D.; Gaug, M.; Galante, N.; Garczarczyk, M.; Mizobuchi, S.; Longo, F.; Scapin, V.; Stamerra, A.

    2007-07-12

    Since the beginning of its operation in April 2005, the MAGIC telescope was able to observe ten different GRB events since their early beginning, even while the prompt emission was still ongoing. Observations, with energy thresholds spanning between 80 and 300 GeV, did not reveal any {gamma}-ray emission. We present a direct determination of the MAGIC sensitivity in GRB mode and the upper limits for the ten follow-up observations. At energies around 100 GeV, MAGIC is currently the fastest and most sensitive operational GRB detector in the world.

  12. SEARCH FOR VERY HIGH ENERGY GAMMA-RAY EMISSION FROM PULSAR-PULSAR WIND NEBULA SYSTEMS WITH THE MAGIC TELESCOPE

    SciTech Connect

    Anderhub, H.; Biland, A.; Antonelli, L. A.; Antoranz, P.; Balestra, S.; Barrio, J. A.; Bose, D.; Backes, M.; Becker, J. K.; Baixeras, C.; Bastieri, D.; Bock, R. K.; Gonzalez, J. Becerra; Bednarek, W.; Berger, K.; Bernardini, E.; Bonnoli, G.; Bordas, P.; Bosch-Ramon, V.; Tridon, D. Borla E-mail: miguel@gae.ucm.e

    2010-02-10

    The MAGIC collaboration has searched for high-energy gamma-ray emission of some of the most promising pulsar candidates above an energy threshold of 50 GeV, an energy not reachable up to now by other ground-based instruments. Neither pulsed nor steady gamma-ray emission has been observed at energies of 100 GeV from the classical radio pulsars PSR J0205+6449 and PSR J2229+6114 (and their nebulae 3C58 and Boomerang, respectively) and the millisecond pulsar PSR J0218+4232. Here, we present the flux upper limits for these sources and discuss their implications in the context of current model predictions.

  13. High energy neutrino emission and neutrino background from gamma-ray bursts in the internal shock model

    SciTech Connect

    Murase, Kohta; Nagataki, Shigehiro

    2006-03-15

    High energy neutrino emission from gamma-ray bursts (GRBs) is discussed. In this paper, by using the simulation kit GEANT4, we calculate proton cooling efficiency including pion-multiplicity and proton-inelasticity in photomeson production. First, we estimate the maximum energy of accelerated protons in GRBs. Using the obtained results, neutrino flux from one burst and a diffuse neutrino background are evaluated quantitatively. We also take account of cooling processes of pion and muon, which are crucial for resulting neutrino spectra. We confirm the validity of analytic approximate treatments on GRB fiducial parameter sets, but also find that the effects of multiplicity and high-inelasticity can be important on both proton cooling and resulting spectra in some cases. Finally, assuming that the GRB rate traces the star formation rate, we obtain a diffuse neutrino background spectrum from GRBs for specific parameter sets. We introduce the nonthermal baryon-loading factor, rather than assume that GRBs are main sources of ultra-high energy cosmic rays (UHECRs). We find that the obtained neutrino background can be comparable with the prediction of Waxman and Bahcall, although our ground in estimation is different from theirs. In this paper, we study on various parameters since there are many parameters in the model. The detection of high energy neutrinos from GRBs will be one of the strong evidences that protons are accelerated to very high energy in GRBs. Furthermore, the observations of a neutrino background has a possibility not only to test the internal shock model of GRBs but also to give us information about parameters in the model and whether GRBs are sources of UHECRs or not.

  14. Synthesis and characterization of mechanically alloyed aluminum-based compounds as high energy density materials

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoying

    2006-12-01

    A new type of metastable reactive powders for potential use as high energy density materials in propellants, explosives, and pyrotechnics was developed. These powders are intended to replace aluminum typically added to energetic formulations to increase reaction enthalpy and temperature. The new materials are metastable aluminum-based alloys, which enable achievement of substantially reduced ignition temperatures and accelerated bulk burn rates compared to aluminum. Titanium and lithium were used as alloying components. The materials properties and characteristics leading to their enhanced combustion performance were investigated. The powders were prepared using mechanical alloying and characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive X-ray spectrometer (SEM/EDX), and thermal analysis. Detailed ignition measurements were performed to identify the processes affecting ignition for the prepared metastable powders. Al-Ti alloys were prepared with compositions ranging from Al0.95 Ti0.05 to Al0.75Ti0.25. Mechanically alloyed powders comprised solid solution of Ti and Al. Upon their heating, a number of subsolidus exothermic transitions were detected and assigned to formation of different modifications of Al3Ti. Three distinguishable oxidation steps were observed for the prepared alloys. The products formed at different oxidation stages were quantitatively analyzed by XRD. Ignition of mechanically alloyed Al-Ti powders was investigated experimentally for heating rates ranging from 3·103 to 2·10 4 K/s. It was shown that ignition was triggered by the exothermic formation of a metastable L12 phase of Al3Ti. Al-Li alloys were synthesized with a fixed bulk composition of Al 0.7Li0.3. At short milling times, an intermetallic LiAl delta-phase was readily produced. At longer milling times, the LiAl phase disappears and a solid solution of Li in Al (alpha-phase) formed with as much as 10 at % of dissolved Li. Continuing milling

  15. Local Absorption of High-energy Emission from Gamma-ray Bursts

    NASA Astrophysics Data System (ADS)

    Gilmore, R.; Ramirez-Ruiz, E.

    2010-09-01

    High-energy photons emitted from gamma-ray bursts (GRBs) are subject to pair-production interactions with lower energy photons, leading to an effective optical depth. In this paper, we estimate the opacity resulting from photon fields located at various distances from long GRB sites: those of the binary companion to the massive stellar progenitor, the star-forming molecular cloud containing the GRB, and the total photon field of the host galaxy. The first two photon fields are found to be transparent for most reasonable sets of assumptions about these systems. In the case of galactic radiation fields, we have performed several numerical simulations to calculate the expected opacities for two different line-of-sight geometries through the host galaxy and include a full accounting of the infrared radiation produced by the absorption and re-radiation of starlight by dust. The optical depth for GeV gamma rays due to direct starlight is less than unity for all host galaxies. At higher energies, >10 TeV, a spectral cutoff can occur due to the rapidly increasing number of mid- to far-IR intragalactic photons re-radiated by dust. Photons in the extragalactic background light therefore remain the only relevant source of photon-photon opacity for ongoing GRB observations with Fermi-LAT and potential future detections with ground-based gamma-ray telescopes.

  16. HIGH-ENERGY EMISSION OF GRB 130427A: EVIDENCE FOR INVERSE COMPTON RADIATION

    SciTech Connect

    Fan, Yi-Zhong; Zhang, Fu-Wen; He, Hao-Ning; Zhou, Bei; Yang, Rui-Zhi; Jin, Zhi-Ping; Wei, Da-Ming; Tam, P. H. T.; Liang, Yun-Feng E-mail: fwzhang@pmo.ac.cn

    2013-10-20

    A nearby superluminous burst GRB 130427A was simultaneously detected by six γ-ray space telescopes (Swift, the Fermi GLAST Burst Monitor (GBM)/Large Area Telescope, Konus-Wind, SPI-ACS/INTEGRAL, AGILE, and RHESSI) and by three RAPTOR full-sky persistent monitors. The isotropic γ-ray energy release is ∼10{sup 54} erg, rendering it the most powerful explosion among gamma-ray bursts (GRBs) with a redshift z ≤ 0.5. The emission above 100 MeV lasted about one day, and four photons are at energies greater than 40 GeV. We show that the count rate of 100 MeV-100 GeV emission may be mainly accounted for by the forward shock synchrotron radiation and the inverse Compton radiation likely dominates at GeV-TeV energies. In particular, an inverse Compton radiation origin is favored for the ∼(95.3, 47.3, 41.4, 38.5, 32) GeV photons arriving at t ∼ (243, 256.3, 610.6, 3409.8, 34366.2) s after the trigger of Fermi-GBM. Interestingly, the external inverse Compton scattering of the prompt emission (the second episode, i.e., t ∼ 120-260 s) by the forward-shock-accelerated electrons is expected to produce a few γ-rays at energies above 10 GeV, while five were detected in the same time interval. A possible unified model for the prompt soft γ-ray, optical, and GeV emission of GRB 130427A, GRB 080319B, and GRB 090902B is outlined. Implications of the null detection of >1 TeV neutrinos from GRB 130427A by IceCube are discussed.

  17. High-energy Emission of GRB 130427A: Evidence for Inverse Compton Radiation

    NASA Astrophysics Data System (ADS)

    Fan, Yi-Zhong; Tam, P. H. T.; Zhang, Fu-Wen; Liang, Yun-Feng; He, Hao-Ning; Zhou, Bei; Yang, Rui-Zhi; Jin, Zhi-Ping; Wei, Da-Ming

    2013-10-01

    A nearby superluminous burst GRB 130427A was simultaneously detected by six γ-ray space telescopes (Swift, the Fermi GLAST Burst Monitor (GBM)/Large Area Telescope, Konus-Wind, SPI-ACS/INTEGRAL, AGILE, and RHESSI) and by three RAPTOR full-sky persistent monitors. The isotropic γ-ray energy release is ~1054 erg, rendering it the most powerful explosion among gamma-ray bursts (GRBs) with a redshift z <= 0.5. The emission above 100 MeV lasted about one day, and four photons are at energies greater than 40 GeV. We show that the count rate of 100 MeV-100 GeV emission may be mainly accounted for by the forward shock synchrotron radiation and the inverse Compton radiation likely dominates at GeV-TeV energies. In particular, an inverse Compton radiation origin is favored for the ~(95.3, 47.3, 41.4, 38.5, 32) GeV photons arriving at t ~ (243, 256.3, 610.6, 3409.8, 34366.2) s after the trigger of Fermi-GBM. Interestingly, the external inverse Compton scattering of the prompt emission (the second episode, i.e., t ~ 120-260 s) by the forward-shock-accelerated electrons is expected to produce a few γ-rays at energies above 10 GeV, while five were detected in the same time interval. A possible unified model for the prompt soft γ-ray, optical, and GeV emission of GRB 130427A, GRB 080319B, and GRB 090902B is outlined. Implications of the null detection of >1 TeV neutrinos from GRB 130427A by IceCube are discussed.

  18. A LEPTONIC MODEL OF STEADY HIGH-ENERGY GAMMA-RAY EMISSION FROM Sgr A*

    SciTech Connect

    Kusunose, Masaaki; Takahara, Fumio E-mail: takahara@vega.ess.sci.osaka-u.ac.jp

    2012-03-20

    Recent observations of Sgr A* by Fermi and HESS have detected steady {gamma}-ray emission in the GeV and TeV bands. We present a new model to explain the GeV {gamma}-ray emission by inverse Compton scattering by nonthermal electrons supplied by the NIR/X-ray flares of Sgr A*. The escaping electrons from the flare regions accumulate in a region with a size of {approx}10{sup 18} cm and magnetic fields of {approx}< 10{sup -4} G. Those electrons produce {gamma}-rays by inverse Compton scattering off soft photons emitted by stars and dust around the central black hole. By fitting the GeV spectrum, we find constraints on the magnetic field and the energy density of optical-UV radiation in the central 1 pc region around the supermassive black hole. While the GeV spectrum is well fitted by our model, the TeV {gamma}-rays, whose spectral index is different from that of the GeV emission, may be from different sources such as pulsar wind nebulae.

  19. High-energy Emission from the Composite Supernova Remnant MSH 15-56

    NASA Technical Reports Server (NTRS)

    Temim, Tea; Slane, Patrick; Castro, Daniel; Plucinsky, Paul; Gelfand, Joseph; Dickel, John R.

    2013-01-01

    MSH 1556 (G326.3-1.8) is a composite supernova remnant (SNR) that consists of an SNR shell and a displaced pulsar wind nebula (PWN) in the radio. We present XMM-Newton and Chandra X-ray observations of the remnant that reveal a compact source at the tip of the radio PWN and complex structures that provide evidence for mixing of the supernova (SN) ejecta with PWN material following a reverse shock interaction. The X-ray spectra are well fitted by a non-thermal power-law model whose photon index steepens with distance from the presumed pulsar, and a thermal component with an average temperature of 0.55 keV. The enhanced abundances of silicon and sulfur in some regions, and the similar temperature and ionization timescale, suggest that much of the X-ray emission can be attributed to SN ejecta that have either been heated by the reverse shock or swept up by the PWN. We find one region with a lower temperature of 0.3 keV that appears to be in ionization equilibrium.Assuming the Sedov model, we derive a number of SNR properties, including an age of 16,500 yr. Modeling of the gamma-ray emission detected by Fermi shows that the emission may originate from the reverse shock-crushed PWN.

  20. Probing the micro-mechanical behavior of bone via high-energy x-rays.

    SciTech Connect

    Almer, J.; Stock, S. R.; X-Ray Science Division; Northwestern Univ.

    2006-01-01

    the sample. While under load, high-energy x-rays (80.7 keV) of transverse size 0.05(x) x 0.05(y) mm{sup 2} were used to sample through the entire thickness (z) of the sample. Wide-angle scattering patterns at multiple x-positions (y=0) were collected using a large area detector, with each 2D pattern containing data in a plane approximately parallel to the sample x-y plane. Internal strains along the longitudinal/loading direction ({var_epsilon}{sub yy}) are shown for the apatite (002) reflection in Fig. 1. Values for five different lateral positions are shown, with x = -1 mm near the convex side of the sample and x = +1 near the concave side. Also shown are value from the strain gage located on the concave side of the specimen. All internal strains are non-zero before unloading and {var_epsilon}{sub yy} {approx} -700 {mu}{var_epsilon}. When stress is applied, strain response varies substantially across the sample, with {var_epsilon}{sub yy} (x = 1) showing the highest compression while {var_epsilon}{sub yy} (x = -1) slightly more tensile values. The macroscopic strain increases similar to, but at a higher degree than, {var_epsilon}{sub yy} (x = -1). At the maximum applied stress of {approx}33 MPa the sample experienced multiple cracks, as verified via post-mortem analysis. Upon unloading the macroscopic strain was primarily elastic, as values (nearly) returned to those seen upon loading.

  1. LONG-TERM MONITORING OF MRK 501 FOR ITS VERY HIGH ENERGY {gamma} EMISSION AND A FLARE IN 2011 OCTOBER

    SciTech Connect

    Bartoli, B.; Catalanotti, S.; Bernardini, P.; Bleve, C.; Bi, X. J.; Cao, Z.; Chen, S. Z.; Chen, Y.; Bolognino, I.; Branchini, P.; Budano, A.; Calabrese Melcarne, A. K.; Cardarelli, R.; Cattaneo, C.; Chen, T. L.; Creti, P.; Cui, S. W.; Dai, B. Z.; D'Ali Staiti, G.; Collaboration: ARGO-YBJ Collaboration; and others

    2012-10-10

    As one of the brightest active blazars in both X-ray and very high energy {gamma}-ray bands, Mrk 501, is very useful for physics associated with jets from active galactic nuclei. The ARGO-YBJ experiment has monitored Mrk 501 for {gamma}-rays above 0.3 TeV since 2007 November. The largest flare since 2005 was observed from 2011 October and lasted until about 2012 April. In this paper, a detailed analysis of this event is reported. During the brightest {gamma}-ray flaring episodes from 2011 October 17 to November 22, an excess of the event rate over 6{sigma} is detected by ARGO-YBJ in the direction of Mrk 501, corresponding to an increase of the {gamma}-ray flux above 1 TeV by a factor of 6.6 {+-} 2.2 from its steady emission. In particular, the {gamma}-ray flux above 8 TeV is detected with a significance better than 4{sigma}. Based on time-dependent synchrotron self-Compton (SSC) processes, the broadband energy spectrum is interpreted as the emission from an electron energy distribution parameterized with a single power-law function with an exponential cutoff at its high-energy end. The average spectral energy distribution for the steady emission is well described by this simple one-zone SSC model. However, the detection of {gamma}-rays above 8 TeV during the flare challenges this model due to the hardness of the spectra. Correlations between X-rays and {gamma}-rays are also investigated.

  2. Very high-energy γ-ray emission from IC 310

    NASA Astrophysics Data System (ADS)

    Neronov, A.; Semikoz, D.; Vovk, Ie.

    2010-09-01

    Context. We search for persistent extragalactic sources of γ-ray s with energies above 100 GeV with the Fermi telescope. Aims: We construct a systematic survey of the extragalactic γ-ray sky at energies above 100 GeV. Such a survey has not been done before by the ground-based Cherenkov γ-ray telescopes, which have, contrary to Fermi, a narrow field of view. Methods: We study a map of arrival directions of the highest energy photons detected by Fermi at Galactic latitudes |b| > 10° and search for significant point-source-like excesses above the diffuse Galactic and extragalactic γ-ray backgrounds. We identify eight significant point-source-like excesses in this map. Results: Seven of the eight sources are known TeV blazars. The previously unknown source is identified with the galaxy IC 310, which is situated in Perseus cluster of galaxies. The source is detected with a significance 6σ above 30 GeV. We identify two possible scenarii for γ-ray emission from this source. One possibility is that emission originates from the base of relativistic outflow from the active nucleus, as in the BL Lacs and FR I type radio galaxies. Otherwise γ-ray photons could be produced at the bow shock that is formed as a result of the fast motion of the galaxy through the intracluster medium. The two models could be distinguished through studying of the γ-ray signal variability.

  3. Gamma-ray emission from globular clusters. Shock high energy emission from the Be-Star/Pulsar System PSR 1259-63. Echoes in x-ray novae

    NASA Technical Reports Server (NTRS)

    Kaaret, Philip

    1995-01-01

    This grant covers work on the Compton phase 3 investigation, 'Shock High Energy Emission from the Be- Star/Pulsar System PSR 1259-63' and cycle 4 investigations 'Diffuse Gamma-Ray Emission at High Latitudes' and 'Echoes in X-Ray Novae'. Work under the investigation 'Diffuse Gamma-Ray Emission at High Latitudes' has lead to the publication of a paper (attached), describing gamma-ray emissivity variations in the northern galactic hemisphere. Using archival EGRET data, we have found a large irregular region of enhanced gamma-ray emissivity at energies greater 100 MeV. This is the first observation of local structure in the gamma-ray emissivity. Work under the investigation 'Echoes in X-Ray Novae' is proceeding with analysis of data from OSSE from the transient source GRO J1655-40. The outburst of this source last fall triggered this Target of Opportunity investigation. Preliminary spectral analysis shows emission out to 600 keV and a pure power low spectrum with no evidence of an exponential cutoff. Work is complete on the analysis of BATSE data from the Be-Star/Pulsar Sustem PSR 1259-63.

  4. Ultra-bright, high-energy-density γ-ray emission from a gas-filled gold cone-capillary

    NASA Astrophysics Data System (ADS)

    Zhu, Xing-Long; Yin, Yan; Yu, Tong-Pu; Liu, Jin-Jin; Zou, De-Bin; Ge, Zhe-Yi; Wang, Wei-Quan; Shao, Fu-Qiu

    2015-09-01

    We propose a new scheme to obtain a compact ultra-bright, high-energy-density γ ray source by ultra-intense laser interaction with a near-critical-density (NCD) plasmas filled gold cone-capillary. By using the particle-in-cell code EPOCH, it is shown that NCD electrons are accelerated by the laser ponderomotive force in the gold cone and emit strong radiation. Considering the effect of large radiation back-reaction force, some electrons are kicked into the laser field. The trapped electrons oscillate significantly in the transverse direction and emit ultra-bright γ ray in the forward direction. By attaching a capillary to the gold cone, the trapped electrons are able to keep oscillating for a long distance and the radiation emission can be significantly enhanced. Three-dimensional simulations show that the total γ photon flux with the photon energy in the range of 3 MeV to 30 MeV is approximately 1013/shot, and the corresponding peak brightness is in the order of 1023 photons/s/mm2/mrad2/0.1%BW. The average energy-density of the radiated γ photons is about 1017J /m3 , which is six orders of magnitude higher than the threshold of high-energy-density physics. The energy conversion efficiency from the laser to the γ photons is estimated to be about 5% at the irradiation of a laser with intensity ˜1.37 ×1022W /cm2 .

  5. Prospects for exploring the local galaxies through the study of their high-energy gamma-ray emission

    NASA Technical Reports Server (NTRS)

    Ozel, Mehmet E.; Fichtel, Carl E.

    1988-01-01

    In the near future, high-energy (E greater than 20 MeV) gamma-ray astronomy offers the promise of a new means of examining the closest galaxies. Three local galaxies, the SMCs, LMCs, and M31, should be visible to the high-energy gamma-ray telescope on the Gamma Ray Observatory and the first two should be seen by GAMMA-1. It is expected that the intensity and the structure of both of the Magellanic Clouds can be examined in sufficient detail to study the cosmic-ray density and its variation, and, thereby, to determine the relevant scale of coupling for the cosmic rays and diffuse matter. With the assumptions of adequate sources and reasonable magnetic field strengths, both of which should likely be satisfied, very specific predictions of the gamma-ray emission can be made separating the three current cosmic-ray containment concepts, namely that it is on the scale of one to a few kiloparsec mass clustering, the whole galaxy, or some much larger scale. Further, because of the markedly different distributions of molecular and atomic hydrogen in the galaxies and the differences between the galaxies, an independent measure of the normalization of the diffuse molecular hydrogen density is possible.

  6. Systematic search for molecular clouds near supernova remnants as sources of very-high-energy γ-ray emission

    NASA Astrophysics Data System (ADS)

    Häffner, Stephanie; Stegmann, Christian; Jung-Richardt, Ira

    2015-12-01

    Supernova remnants accelerate particles up to energies of at least 100 TeV as established by observations in very-high-energy γ-ray astronomy. Molecular clouds in their vicinity provide an increased amount of target material for proton-proton interaction and subsequent neutral pion decay into γ-rays of accelerated hadrons escaping the remnant. Therefore, these molecular clouds are potential γ-ray sources. The γ-ray emission from these clouds provides a unique environment to derive information on the propagation of very-high-energy particles through the interstellar medium as well as on the acceleration of hadrons in supernova remnants. Current Imaging Atmospheric Cherenkov Telescope systems are suitable to explore a large parameter space of the propagation properties depending on the age of the supernova remnant and the distance between the remnant and the nearby molecular cloud. In this paper we present our strategy and results of a systematic search for γ-ray emitting molecular clouds near supernova remnants which are potentially detectable with current experiments in the TeV energy range and explore the prospects of future experiments.

  7. Prospects for detection of very high-energy emission from GRB in the context of the external shock model

    NASA Astrophysics Data System (ADS)

    Galli, A.; Piro, L.

    2008-10-01

    Context: The detection of the 100 GeV-TeV emission by a gamma-ray burst (GRB) will provide an unprecedented opportunity to study the nature of the central engine and the interaction between the relativistic flow and the environment of the burst's progenitor. Aims: In this paper we show that there are exciting prospects of detecting from the burst by MAGIC high-energy (HE) emission during the early X-ray flaring activity and, later, during the normal afterglow phase. We also identify the best observational strategy: trigger conditions and time period of observation. Methods: We determine the expected HE emission from the flaring and afterglow phases of GRBs in the context of the external shock scenario and compare them with the MAGIC threshold. Results: We find that an X-ray flare with the average properties of the class can be detected in the 100 GeV range by MAGIC, provided that z ≲ 0.7. The requested observational window with MAGIC should then start from 10-20 s after the burst and cover about 1000-2000 s. Furthermore, we demonstrate that there are solid prospects of detecting the late afterglow emission in the same energy range for most of the bursts with z ≲ 0.5 if the density of the external medium is n ≳ a few cm-3. In this case, the MAGIC observation shall extend to about 10-20 ks. We provide recipes for tailoring this prediction to the observational properties of each burst, in particular the fluence in the prompt emission and the redshift, thus allowing an almost real time decision procedure to decide whether to continue the follow-up observation of a burst at late times.

  8. The extended jet of AP Librae: Origin of the very high-energy γ-ray emission?

    NASA Astrophysics Data System (ADS)

    Zacharias, Michael; Wagner, Stefan J.

    2016-04-01

    The low-frequency peaked BL Lac object (LBL) AP Librae exhibits very-high-energy (VHE, E > 100 GeV) γ-ray emission and hosts an extended jet, which has been detected in radio and X-rays. The jet X-ray spectral index implies an inverse Compton origin. These observations are unusual for LBLs calling for a consistent explanation of this extraordinary source. The observationally constrained parameters necessary to describe the core emission within the standard one-zone model are unable to explain the broad-band spectrum, even if observationally unconstrained external photon fields are taken into account. We demonstrate that the addition of the extended jet emission successfully reproduces the total spectral energy distribution. In particular, the VHE radiation is produced in the >100 kpc long extended jet via inverse Compton scattering of cosmic microwave background photons by highly relativistic electrons. We present several ways to test this theory. The extended jet is weakly magnetized (B0 = 2.5 μG), while its minimum and maximum electron Lorentz factors are γmin = 60 and γmax = 5 × 106, respectively. The electron spectral index is s = 2.6. These parameters are comparable to parameters of other blazars with extended X-ray jets dominated by inverse Compton scattering.

  9. Modeling the Delayed Emission in the 2005 Mkn 501 Very-High-Energy Gamma-Ray Flare

    SciTech Connect

    Bednarek, Wlodek; Wagner, Robert

    2008-12-24

    Recently, the MAGIC collaboration reported evidence for a delay in the arrival times of photons of different energies during a {gamma}-ray flare from the blazar Markarian 501 on 2005 July 9. We describe the observed delayed high-energy emission by applying a homogeneous synchrotron self-Compton (SSC) model under the assumption that the blob, containing relativistic electrons, was observed in its acceleration phase. This modified SSC model predicts the appearance of a {gamma}-ray flare first at lower energies and subsequently at higher energies. Based on the reported time delay, we predict a delay on the order of 1 h if observed between 10 GeV and 100 GeV, which can be tested in the future by simultaneous flare observations using, e.g., the Fermi Gamma-Ray Telescope and Cerenkov telescopes.

  10. High-energy side-peak emission of exciton-polariton condensates in high density regime

    PubMed Central

    Horikiri, Tomoyuki; Yamaguchi, Makoto; Kamide, Kenji; Matsuo, Yasuhiro; Byrnes, Tim; Ishida, Natsuko; Löffler, Andreas; Höfling, Sven; Shikano, Yutaka; Ogawa, Tetsuo; Forchel, Alfred; Yamamoto, Yoshihisa

    2016-01-01

    In a standard semiconductor laser, electrons and holes recombine via stimulated emission to emit coherent light, in a process that is far from thermal equilibrium. Exciton-polariton condensates–sharing the same basic device structure as a semiconductor laser, consisting of quantum wells coupled to a microcavity–have been investigated primarily at densities far below the Mott density for signatures of Bose-Einstein condensation. At high densities approaching the Mott density, exciton-polariton condensates are generally thought to revert to a standard semiconductor laser, with the loss of strong coupling. Here, we report the observation of a photoluminescence sideband at high densities that cannot be accounted for by conventional semiconductor lasing. This also differs from an upper-polariton peak by the observation of the excitation power dependence in the peak-energy separation. Our interpretation as a persistent coherent electron-hole-photon coupling captures several features of this sideband, although a complete understanding of the experimental data is lacking. A full understanding of the observations should lead to a development in non-equilibrium many-body physics. PMID:27193700

  11. High-energy side-peak emission of exciton-polariton condensates in high density regime

    NASA Astrophysics Data System (ADS)

    Horikiri, Tomoyuki; Yamaguchi, Makoto; Kamide, Kenji; Matsuo, Yasuhiro; Byrnes, Tim; Ishida, Natsuko; Löffler, Andreas; Höfling, Sven; Shikano, Yutaka; Ogawa, Tetsuo; Forchel, Alfred; Yamamoto, Yoshihisa

    2016-05-01

    In a standard semiconductor laser, electrons and holes recombine via stimulated emission to emit coherent light, in a process that is far from thermal equilibrium. Exciton-polariton condensates–sharing the same basic device structure as a semiconductor laser, consisting of quantum wells coupled to a microcavity–have been investigated primarily at densities far below the Mott density for signatures of Bose-Einstein condensation. At high densities approaching the Mott density, exciton-polariton condensates are generally thought to revert to a standard semiconductor laser, with the loss of strong coupling. Here, we report the observation of a photoluminescence sideband at high densities that cannot be accounted for by conventional semiconductor lasing. This also differs from an upper-polariton peak by the observation of the excitation power dependence in the peak-energy separation. Our interpretation as a persistent coherent electron-hole-photon coupling captures several features of this sideband, although a complete understanding of the experimental data is lacking. A full understanding of the observations should lead to a development in non-equilibrium many-body physics.

  12. High-energy side-peak emission of exciton-polariton condensates in high density regime.

    PubMed

    Horikiri, Tomoyuki; Yamaguchi, Makoto; Kamide, Kenji; Matsuo, Yasuhiro; Byrnes, Tim; Ishida, Natsuko; Löffler, Andreas; Höfling, Sven; Shikano, Yutaka; Ogawa, Tetsuo; Forchel, Alfred; Yamamoto, Yoshihisa

    2016-01-01

    In a standard semiconductor laser, electrons and holes recombine via stimulated emission to emit coherent light, in a process that is far from thermal equilibrium. Exciton-polariton condensates-sharing the same basic device structure as a semiconductor laser, consisting of quantum wells coupled to a microcavity-have been investigated primarily at densities far below the Mott density for signatures of Bose-Einstein condensation. At high densities approaching the Mott density, exciton-polariton condensates are generally thought to revert to a standard semiconductor laser, with the loss of strong coupling. Here, we report the observation of a photoluminescence sideband at high densities that cannot be accounted for by conventional semiconductor lasing. This also differs from an upper-polariton peak by the observation of the excitation power dependence in the peak-energy separation. Our interpretation as a persistent coherent electron-hole-photon coupling captures several features of this sideband, although a complete understanding of the experimental data is lacking. A full understanding of the observations should lead to a development in non-equilibrium many-body physics. PMID:27193700

  13. Detection techniques of radio emission from ultra high energy cosmic rays

    NASA Astrophysics Data System (ADS)

    Morris, Chad M.

    We discuss recent and future efforts to detect radio signals from extended air showers at the Pierre Auger Observatory in Malargue, Argentina. With the advent of low-cost, high-performance digitizers and robust digital signal processing software techniques, radio detection of cosmic rays has resurfaced as a promising measurement system. The inexpensive nature of the detector media (metallic wires, rods or parabolic dishes) and economies of scale working in our favor (inexpensive high-quality C-band amplifiers and receivers) make an array of radio antennas an appealing alternative to the expense of deploying an array of Cherenkov detector water tanks or 'fly's eye' optical telescopes for fluorescence detection. The calorimetric nature of the detection and the near 100% duty cycle gives the best of both traditional detection techniques. The history of cosmic ray detection detection will be discussed. A short review on the astrophysical properties of cosmic rays and atmospheric interactions will lead into a discussion of two radio emission channels that are currently being investigated.

  14. A Search for High-Energy Neutrino Emission from Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Whitehorn, Nathan

    2012-05-01

    A century after their discovery, the origin of cosmic rays remains one of the most enduring mysteries in physics. They can have energies that exceed 1020 eV, a hundred million times as energetic as the most powerful Earth-bound particle accelerators and must therefore be produced in the universe's most violent environments. Direct observation of their origins, however, has proven difficult due to deflection of charged cosmic ray particles in galactic and intergalactic magnetic fields, obscuring their true origins. Astronomy using electrically neutral particles, such as photons and neutrinos, does not, however, share this difficulty. This work presents a search for neutrino emission from one of the primary candidates for the sources of the highest-energy cosmic rays, Gamma-Ray Bursts, using the recently-completed IceCube neutrino telescope located at the South Pole. The null result obtained from this search contradicts well-established predictions for the neutrino flux from Gamma-Ray Bursts if they are the cosmic ray sources, forcing a reevaluation of these theoretical models.

  15. A Search for Ultra--High-Energy Gamma-Ray Emission from Five Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Allen, G. E.; Berley, D.; Biller, S.; Burman, R. L.; Cavalli-Sforza, M.; Chang, C. Y.; Chen, M. L.; Chumney, P.; Coyne, D.; Dion, C. L.; Dorfan, D.; Ellsworth, R. W.; Goodman, J. A.; Haines, T. J.; Hoffman, C. M.; Kelley, L.; Klein, S.; Schmidt, D. M.; Schnee, R.; Shoup, A.; Sinnis, C.; Stark, M. J.; Williams, D. A.; Wu, J.-P.; Yang, T.; Yodh, G. B.

    1995-07-01

    The majority of the cosmic rays in our Galaxy with energies in the range of ~1010--1014 eV are thought to be accelerated in supernova remnants (SNRs). Measurements of SNR gamma-ray spectra in this energy region could support or contradict this concept. The Energetic Gamma-Ray Experiment Telescope (EGRET) collaboration has reported six sources of gamma rays above 108 eV whose coordinates are coincident with SNRs. Five of these sources are within the field of view of the CYGNUS extensive air shower detector. A search of the CYGNUS data set reveals no evidence of gamma-ray emission at energies ~1014 eV for these five SNRs. The flux upper limits from the CYGNUS data are compared to the lower energy fluxes measured with the EGRET detector using Drury, Aharonian, & Volk's recent model of gamma-ray production in the shocks of SNRs. The results suggest one or more of the following: (1) the gamma-ray spectra for these five SNRs soften by about 1014 eV, (2) the integral gamma-ray spectra of the SNRs are steeper than about E-1.3, or (3) most of the gamma rays detected with the EGRET instrument for each SNR are not produced in the SNR's shock but are produced at some other site (such as a pulsar).

  16. Discovery of high and very high-energy emission from the BL Lacertae object SHBL J001355.9-185406

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; O'C. Drury, L.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Gast, H.; Giebels, B.; Glicenstein, J. F.; Göring, D.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hague, J. D.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Nedbal, D.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spieß, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2013-06-01

    The detection of the high-frequency peaked BL Lac object (HBL) SHBL J001355.9-185406 (z = 0.095) at high (HE; 100 MeV < E < 300 GeV) and very high-energy (VHE; E > 100 GeV) with the Fermi Large Area Telescope (LAT) and the High Energy Stereoscopic System (H.E.S.S.) is reported. Dedicated observations were performed with the H.E.S.S. telescopes, leading to a detection at the 5.5σ significance level. The measured flux above 310 GeV is (8.3 ± 1.7stat ± 1.7sys) × 10-13 photons cm-2 s-1 (about 0.6% of that of the Crab Nebula), and the power-law spectrum has a photon index of Γ = 3.4 ± 0.5stat ± 0.2sys. Using 3.5 years of publicly available Fermi-LAT data, a faint counterpart has been detected in the LAT data at the 5.5σ significance level, with an integrated flux above 300 MeV of (9.3 ± 3.4stat ± 0.8sys) × 10-10 photons cm-2 s-1 and a photon index of Γ = 1.96 ± 0.20stat ± 0.08sys. X-ray observations with Swift-XRT allow the synchrotron peak energy in νFν representation to be located at ~1.0 keV. The broadband spectral energy distribution is modelled with a one-zone synchrotronself-Compton (SSC) model and the optical data by a black-body emission describing the thermal emission of the host galaxy. The derived parameters are typical of HBLs detected at VHE, with a particle-dominated jet.

  17. Wavelength dependent high-energy ion emission from intense mid-IR laser-cluster interaction

    NASA Astrophysics Data System (ADS)

    Park, Hyunwook; Wang, Zhou; Agostini, Pierre; Dimauro, Louis

    2015-05-01

    We present the first measurements on the wavelength dependence from the near-infrared to mid-infrared of inert gas clusters interacting with an intense, ultrafast pulse. In the experiments, ion energy distributions have been recorded with various wavelength (0.8-2.2 μm), while all other conditions are fixed. It is found that the wavelength plays a significant role in electron-plasma heating and thus energetic ion production. The maximum energy of the detected ion, Emax , decreases with increasing wavelength, reaches a minimum, then increases. We attribute this result to two different electron-heating mechanisms depending on the wavelength- volume (Inverse Bremsstrahlung: IB) and surface (Brunel) heating. In the short wavelength regime (0.8-1.5 μm), IB heating dominates the production of multiply charged ions, since the electrons are resonantly heated near plasma frequency. As the wavelength is increased, IB heating is progressively suppressed, resulting in a smaller value of Emax . Brunel heating, on the other hand, increases due to a quadratic increase of the electrons ponderomotive energy, and becomes dominant in the long wavelength regime (1.7-2.2 μm). The lowest Emax values would thus occur at the wavelength where the dominant heating mechanism switches from volume to surface. Air Force Office of Scientific Res.

  18. Experimental study on the fabrication of advanced materials for energy applications using high energy mechanical milling

    NASA Astrophysics Data System (ADS)

    Narayana Swamy, Ashvin Kumar

    The reaction of aluminum (Al) powder with water has the potential for on demand hydrogen generation. Conventional Al powders, however, react with water slowly due to a highly protective oxide layer on the particle surface. Current methods for Al activation involve harmful and expensive materials. The nano-scale Al powders also remain very expensive and have problems such as a large amount of oxide on the surface. The use of aluminum in an energy generation cycle is also hindered by the fact that, although Al is the most abundant metal in the Earth's crust, its recovery from ore consumes a lot of energy. Recycling aluminum hydroxide, formed as a result of Al reaction with water, would also require large amounts of energy. The energy consumption for production of Al powder and hence its cost could be significantly reduced by using recycled aluminum scrap and waste where aluminum is contained in metallic, non-oxidized form. The research work presented here investigates the preparation of an activated aluminum powder from aluminum foil that is widely available as scrap and waste. The obtained results demonstrate that a highly reactive, fine powder can be obtained from Al foil by high-energy ball milling with sodium chloride (NaCl). The obtained powder readily reacts with hot water, releasing hydrogen. Note that NaCl is an environment-friendly additive that can easily be removed after milling and recycled. After washing NaCl out, the powders retain a high reactivity with respect to hot water. As compared to previously studied activation of commercial Al powders, a major advantage of the investigated process is the feasibility of using secondary aluminum. Another area of research presented here is the synthesis of gallium oxide (Ga2O3) nanostructures for their use as high-temperature sensors. Quasi one-dimensional nanomaterials are of great interest due to increased focus on their importance in physics research and also their applications in the nanodevices industry

  19. High-Energy X-Ray Detection of G359.89-0.08 (SGR A-E): Magnetic Flux Tube Emission Powered by Cosmic Rays?

    NASA Technical Reports Server (NTRS)

    Zhang, Shuo; Hailey, Charles J.; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Christensen, Finn E.; Gotthelf, Eric V.; Harrison, Fiona A.; Mori, Kaya; Nynka, Melania; Stern, Daniel; Tomsick, John A; Zhang, Will

    2014-01-01

    We report the first detection of high-energy X-ray (E (is) greater than 10 keV) emission from the Galactic center non-thermal filament G359.89-0.08 (Sgr A-E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to approximately 50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index gamma approximately equals 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3-79 keV band is F(sub X) = (2.0 +/- 0.1) × 10(exp -12)erg cm(-2) s(-1) , corresponding to an unabsorbed X-ray luminosity L(sub X) = (2.6+/-0.8)×10(exp 34) erg s(-1) assuming a distance of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A-E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to (is) approximately 100 kyr) with low surface brightness and radii up to (is) approximately 30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.

  20. DISCOVERY OF VARIABILITY IN THE VERY HIGH ENERGY {gamma}-RAY EMISSION OF 1ES 1218+304 WITH VERITAS

    SciTech Connect

    Acciari, V. A.; Benbow, W.; Aliu, E.; Beilicke, M.; Bugaev, V.; Dickherber, R.; Boltuch, D.; Boettcher, M.; Bradbury, S. M.; Byrum, K.; Cesarini, A.; Ciupik, L.; Fortson, L.; Cogan, P.; Cui, W.; Finley, J. P.; Duke, C.; Falcone, A.; Finnegan, G.; Furniss, A.

    2010-02-01

    We present results from an intensive VERITAS monitoring campaign of the high-frequency peaked BL Lac object 1ES 1218+304 in 2008/2009. Although 1ES 1218+304 was detected previously by MAGIC and VERITAS at a persistent level of {approx}6% of the Crab Nebula flux, the new VERITAS data reveal a prominent flare reaching {approx}20% of the Crab. While very high energy (VHE) flares are quite common in many nearby blazars, the case of 1ES 1218+304 (redshift z = 0.182) is particularly interesting since it belongs to a group of blazars that exhibit unusually hard VHE spectra considering their redshifts. When correcting the measured spectra for absorption by the extragalactic background light, 1ES 1218+304 and a number of other blazars are found to have differential photon indices {gamma}{<=} 1.5. The difficulty in modeling these hard spectral energy distributions in blazar jets has led to a range of theoretical {gamma}-ray emission scenarios, one of which is strongly constrained by these new VERITAS observations. We consider the implications of the observed light curve of 1ES 1218+304, which shows day scale flux variations, for shock acceleration scenarios in relativistic jets, and in particular for the viability of kiloparsec-scale jet emission scenarios.

  1. Sub-second variations of high energy ( 300 keV) hard X-ray emission from solar flares

    NASA Technical Reports Server (NTRS)

    Bai, Taeil

    1986-01-01

    Subsecond variations of hard X-ray emission from solar flares were first observed with a balloon-borne detector. With the launch of the Solar Maximum Mission (SMM), it is now well known that subsecond variations of hard X-ray emission occur quite frequently. Such rapid variations give constraints on the modeling of electron energization. Such rapid variations reported until now, however, were observed at relatively low energies. Fast mode data obtained by the Hard X-ray Burst Spectrometer (HXRBS) has time resolution of approximately 1 ms but has no energy resolution. Therefore, rapid fluctuations observed in the fast-mode HXRBS data are dominated by the low energy hard X-rays. It is of interest to know whether rapid fluctuations are observed in high-energy X-rays. The highest energy band at which subsecond variations were observed is 223 to 1057 keV. Subsecond variations observed with HXRBS at energies greater than 300 keV are reported, and the implications discussed.

  2. The Relationship between the High-Energy Continuum and Emission Lines in Quasars: A Low-Redshift Sample

    NASA Astrophysics Data System (ADS)

    Green, Paul J.

    1996-08-01

    Photoionization models dictate that many prominent quasar emission lines are sensitive to both the luminosity and shape of the quasars high- energy continuum-primarily the extreme ultraviolet (EUV) and soft X-ray continuum. Unfortunately, the EUV band is severely obscured by Galactic absorption. Using data from the adjacent UV and soft X-ray bandpasses, we initiate the first large-scale, multiline investigation of correlations between the QSO soft X-ray continuum and line emission in a sample of QSOs observed by Einstein and IUE. We present a new error analysis for objective, automated line measurements, which enables us to include the information contained in weak or undetected lines. We tabulate more than 300 UV emission-line equivalent widths from IUE spectra of 85 QSOs in the atlas of Lanzetta, Turnshek, & Sandoval, then characterize the distributions of line equivalent and velocity widths (Wlambda_ and FWHM). We then compare these line parameters to the QSO continuum spectral energy distributions from optical through soft X-ray wavelengths, using survival analysis to incorporate any nondetections for X-ray flux and/or UV emission lines. Several correlations noted in previous studies are not reproduced here. However, we illustrate that the exclusion of undetected lines from such studies may spuriously enhance apparent correlations. We find significant correlations between Wlambda_ and UV luminosity (e.g., the well-studied Baldwin effect) for Lyα, C IV, He II, and C III]. Wlambda_(C III]) and Wlambda_(He II) also show previously unreported correlations with X-ray luminosity that, for C III], appears to be primary. The line ratios C III]/Lyα and He II/Lyα both show strongest dependence on l_x_. Wlambda_(Lyα) correlates strongly with spectral slopes α_UV_ and α_OX_ (between 2500 A and 2 keV), but not with X-ray luminosity. Using these results, we argue that one simple geometrical interpretation of the Baldwin effect (BEff) as a result of a distribution of

  3. Variable Gamma-Ray Emission Induced by Ultra-high Energy Neutral Beams: Application to 4C +21.35

    NASA Astrophysics Data System (ADS)

    Dermer, Charles D.; Murase, Kohta; Takami, Hajime

    2012-08-01

    The flat-spectrum radio quasar 4C +21.35 (PKS 1222+216) displays prominent nuclear infrared emission from ≈1200 K dust. A 70-400 GeV flare with ≈10 minute variations during half an hour of observations was found by the MAGIC telescopes, and GeV variability was observed on sub-day timescales with the Large Area Telescope on Fermi. We examine 4C +21.35, assuming that it is a source of ultra-high energy cosmic rays (UHECRs). UHECR proton acceleration in the inner jet powers a neutral beam of neutrinos, neutrons, and γ-rays from pγ photopion production. The radiative efficiency and production spectra of neutrals formed through photohadronic processes with isotropic external target photons of the broad-line region (BLR) and torus are calculated. Secondary radiations made by this process have a beaming factor vpropδ5 D, where δD is the Doppler factor. The pair-production optical depth for γ-rays and the photopion efficiency for UHECR neutrons as they pass through external isotropic radiation fields are calculated. If target photons come from the BLR and dust torus, large Doppler factors, δD >~ 100, are required to produce rapidly variable secondary radiation with isotropic luminosity >~ 1047 erg s-1 at the pc scale. The γ-ray spectra from leptonic secondaries are calculated from cascades initiated by the UHECR neutron beam at the pc-scale region and fit to the flaring spectrum of 4C +21.35. Detection of >~ 100 TeV neutrinos from 4C +21.35 or other very high energy γ-ray blazars with IceCube or KM3NeT would confirm this scenario.

  4. On the dehydration mechanism of Mg(OH){sub 2} by a high-energy electron beam

    SciTech Connect

    Su Dong; Jiang, Nan; Spence, John C. H.; He Feng; Petuskey, William T.

    2008-09-15

    The dehydration process in Mg(OH){sub 2} induced by high-energy electron irradiation is studied by in situ electron energy loss spectroscopy. During dehydration, both the low energy-loss spectra and the Mg L{sub 23} edge show the existence of partially oxidized Mg- or O-deficient MgO in the dehydrated products, which is not seen in the thermally dehydrated MgO. This indicates that the dehydration mechanism under the electron beam may be different from the mechanism involved in a thermal process.

  5. Mechanism of multiple grating formation in high-energy recording of holographic sensors

    NASA Astrophysics Data System (ADS)

    Yetisen, Ali K.; Montelongo, Yunuen; Farandos, Nicholas M.; Naydenova, Izabela; Lowe, Christopher R.; Yun, Seok Hyun

    2014-12-01

    We report numerical analyses of Bragg diffraction by Denisyuk reflection holograms recorded by a high-energy pulsed laser. An intensity threshold must be passed to pattern a multilayer reflection and transmission hologram, which exhibits a nonlinear fringe structure. Numerical evaluations are provided for the laser light intensity, readout diffraction offset angle, transmission of the layer, and thickness of the polymer matrix during hologram recording. A non-sinusoidal surface pattern is formed at the top of the multilayer structure, and its effect on the diffraction properties of the structure becomes significant when the recording tilt angle is increased. Experimental results show that the angle of the diffracted light increases nonlinearly according to the tilt geometry in grating formation.

  6. Mechanism of multiple grating formation in high-energy recording of holographic sensors

    SciTech Connect

    Yetisen, Ali K. Yun, Seok Hyun; Montelongo, Yunuen; Farandos, Nicholas M.; Naydenova, Izabela; Lowe, Christopher R.

    2014-12-29

    We report numerical analyses of Bragg diffraction by Denisyuk reflection holograms recorded by a high-energy pulsed laser. An intensity threshold must be passed to pattern a multilayer reflection and transmission hologram, which exhibits a nonlinear fringe structure. Numerical evaluations are provided for the laser light intensity, readout diffraction offset angle, transmission of the layer, and thickness of the polymer matrix during hologram recording. A non-sinusoidal surface pattern is formed at the top of the multilayer structure, and its effect on the diffraction properties of the structure becomes significant when the recording tilt angle is increased. Experimental results show that the angle of the diffracted light increases nonlinearly according to the tilt geometry in grating formation.

  7. Impulsive and long duration high-energy gamma-ray emission from the very bright 2012 March 7 solar flares

    SciTech Connect

    Ajello, M.; Albert, A.; Allafort, A.; Caliandro, G. A.; Cameron, R. A.; Charles, E.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Buson, S.; Bellazzini, R.; Bregeon, J.; Bissaldi, E.; Bonamente, E.; Cecchi, C.; Brandt, T. J.; Brigida, M.; Bruel, P.; Caraveo, P. A. E-mail: vahep@stanford.edu; and others

    2014-07-01

    The Fermi Large Area Telescope (LAT) detected gamma-rays up to 4 GeV from two bright X-class solar flares on 2012 March 7, showing both an impulsive and temporally extended emission phases. The gamma-rays appear to originate from the same active region as the X-rays associated with these flares. The >100 MeV gamma-ray flux decreases monotonically during the first hour (impulsive phase) followed by a slower decrease for the next 20 hr. A power law with a high-energy exponential cutoff can adequately describe the photon spectrum. Assuming that the gamma rays result from the decay of pions produced by accelerated protons and ions with a power-law spectrum, we find that the index of that spectrum is ∼3, with minor variations during the impulsive phase. During the extended phase the photon spectrum softens monotonically, requiring the proton index varying from ∼4 to >5. The >30 MeV proton flux observed by the GOES satellites also shows a flux decrease and spectral softening, but with a harder spectrum (index ∼2-3). Based on these observations, we explore the relative merits of prompt or continuous acceleration scenarios, hadronic or leptonic emission processes, and acceleration at the solar corona or by the fast coronal mass ejections. We conclude that the most likely scenario is continuous acceleration of protons in the solar corona that penetrate the lower solar atmosphere and produce pions that decay into gamma rays. However, acceleration in the downstream of the shock cannot be definitely ruled out.

  8. Discovery of Very High Energy Gamma-Ray Emission from 1FGL J2001.1 4351 by MAGIC

    SciTech Connect

    Berger, Karsten; Paneque, David; Giavitto, Gianluca; /Barcelona, IFAE

    2012-05-07

    We report the discovery of Very High Energy (VHE; >100 GeV) gamma-ray emission from the source 1FGL J2001.1+4351, (RA 20 01 13.5, dec 43 53 02.8, J2000), which is positionally consistent with the location of the flat spectrum radio source MG4 J200112+4352 (RA 20 01 12.9, dec 43 52 52.8, J2000). The VHE detection is based on a 1.5 hour-long observation performed on July 16th in stereoscopic mode with the two 17m diameter imaging Cherenkov telescopes on La Palma, Canary Islands, Spain. The preliminary analysis of the MAGIC data using the standard cuts optimized for soft energy spectra sources yields a detection of 125 gamma-rays above 90 GeV, corresponding to a pre-trail statistical significance of 7.6 standard deviations. The observed flux is estimated to be {approx}20% of the Crab nebula flux above 100 GeV. Earlier MAGIC observations indicated a substantially lower flux; hence indicating that the source is variable on a few days timescale.

  9. High-energy chemistry of formamide: A unified mechanism of nucleobase formation

    PubMed Central

    Ferus, Martin; Nesvorný, David; Šponer, Jiří; Kubelík, Petr; Michalčíková, Regina; Shestivská, Violetta; Šponer, Judit E.; Civiš, Svatopluk

    2015-01-01

    The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life about 4 billion years ago suggest that extraterrestrial impacts could contribute to the synthesis of the building blocks of the first life-giving molecules. We simulated the high-energy synthesis of nucleobases from formamide during the impact of an extraterrestrial body. A high-power laser has been used to induce the dielectric breakdown of the plasma produced by the impact. The results demonstrate that the initial dissociation of the formamide molecule could produce a large amount of highly reactive CN and NH radicals, which could further react with formamide to produce adenine, guanine, cytosine, and uracil. Based on GC-MS, high-resolution FTIR spectroscopic results, as well as theoretical calculations, we present a comprehensive mechanistic model, which accounts for all steps taking place in the studied impact chemistry. Our findings thus demonstrate that extraterrestrial impacts, which were one order of magnitude more abundant during the LHB period than before and after, could not only destroy the existing ancient life forms, but could also contribute to the creation of biogenic molecules. PMID:25489115

  10. High-energy chemistry of formamide: a unified mechanism of nucleobase formation.

    PubMed

    Ferus, Martin; Nesvorný, David; Šponer, Jiří; Kubelík, Petr; Michalčíková, Regina; Shestivská, Violetta; Šponer, Judit E; Civiš, Svatopluk

    2015-01-20

    The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life about 4 billion years ago suggest that extraterrestrial impacts could contribute to the synthesis of the building blocks of the first life-giving molecules. We simulated the high-energy synthesis of nucleobases from formamide during the impact of an extraterrestrial body. A high-power laser has been used to induce the dielectric breakdown of the plasma produced by the impact. The results demonstrate that the initial dissociation of the formamide molecule could produce a large amount of highly reactive CN and NH radicals, which could further react with formamide to produce adenine, guanine, cytosine, and uracil. Based on GC-MS, high-resolution FTIR spectroscopic results, as well as theoretical calculations, we present a comprehensive mechanistic model, which accounts for all steps taking place in the studied impact chemistry. Our findings thus demonstrate that extraterrestrial impacts, which were one order of magnitude more abundant during the LHB period than before and after, could not only destroy the existing ancient life forms, but could also contribute to the creation of biogenic molecules. PMID:25489115

  11. MAGIC detects very high energy gamma-ray emission from the blazar OT 081 (PKS 1749+096, 4C +09.57)

    NASA Astrophysics Data System (ADS)

    Mirzoyan, Razmik

    2016-07-01

    The MAGIC collaboration reports on the detection of very high energy (VHE; E > 150 GeV) gamma-ray emission from OT 081 (RA=17 51 32.82, dec=+09 39 00.73, J2000.0; also known as PKS 1749+096 and 4C +09.57).

  12. Mechanical properties improvement of pulsed laser-deposited hydroxyapatite thin films by high energy ion-beam implantation

    NASA Astrophysics Data System (ADS)

    Nelea, V.; Pelletier, H.; Müller, D.; Broll, N.; Mille, P.; Ristoscu, C.; Mihailescu, I. N.

    2002-01-01

    Major problems in the hydroxyapatite (HA), Ca 5(PO 4) 3OH, thin films processing still keep the poor mechanical properties and the lack in density. We present a study on the feasibility of high energy ion-beam implantation technique to densify HA bioceramic films. Crystalline HA films were grown by pulsed laser deposition (PLD) method using an excimer KrF ∗ laser ( λ=248 nm, τ FWHM≥20 ns). The films were deposited on Ti-5Al-2.5Fe alloys substrates previously coated with a ceramic TiN buffer layer. After deposition the films were implanted with Ar + ions at high energy. Optical microscopy (OM), white light confocal microscopy (WLCM), grazing incidence X-ray diffraction (GIXRD) and Berkovich nanoindentation in normal and scratch options have been applied for the characterization of the obtained structures. We put into evidence an enhancement of the mechanical characteristics after implantation, while GIXRD measurements confirm that the crystalline structure of HA phase is preserved. The improvement in mechanical properties is an effect of a densification after ion treatment as a result of pores elimination and grains regrowth.

  13. NuSTAR Detection of High-Energy X-Ray Emission and Rapid Variability from Sagittarius A(star) Flares

    NASA Technical Reports Server (NTRS)

    Barriere, Nicolas M.; Tomsick, John A.; Baganoff, Frederick K.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Dexter, Jason; Grefenstette, Brian; Hailey, Charles J.; Zhang, William W.

    2014-01-01

    Sagittarius A(star) harbors the supermassive black hole that lies at the dynamical center of our Galaxy. Sagittarius A(star) spends most of its time in a low luminosity emission state but flares frequently in the infrared and X-ray, increasing up to a few hundred fold in brightness for up to a few hours at a time. The physical processes giving rise to the X-ray flares are uncertain. Here we report the detection with the NuSTAR observatory in Summer and Fall 2012 of four low to medium amplitude X-ray flares to energies up to 79 keV. For the first time, we clearly see that the power-law spectrum of Sagittarius A(star) X-ray flares extends to high energy, with no evidence for a cut off. Although the photon index of the absorbed power-law fits are in agreement with past observations, we find a difference between the photon index of two of the flares (significant at the 95% confidence level). The spectra of the two brightest flares (approx. 55 times quiescence in the 2- 10 keV band) are compared to simple physical models in an attempt to identify the main X-ray emission mechanism, but the data do not allow us to significantly discriminate between them. However, we confirm the previous finding that the parameters obtained with synchrotron models are, for the X-ray emission, physically more reasonable than those obtained with inverse-Compton models. One flare exhibits large and rapid (less than 100 s) variability, which, considering the total energy radiated, constrains the location of the flaring region to be within approx. 10 Schwarzschild radii of the black hole.

  14. High-energy X-ray detection of G359.89–0.08 (SGR A–E): Magnetic flux tube emission powered by cosmic rays?

    SciTech Connect

    Zhang, Shuo; Hailey, Charles J.; Gotthelf, Eric V.; Mori, Kaya; Nynka, Melania; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Tomsick, John A.; Christensen, Finn E.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.

    2014-03-20

    We report the first detection of high-energy X-ray (E > 10 keV) emission from the Galactic center non-thermal filament G359.89–0.08 (Sgr A–E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to ∼50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index Γ ≈ 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3-79 keV band is F{sub X} = (2.0 ± 0.1) × 10{sup –12} erg cm{sup –2} s{sup –1}, corresponding to an unabsorbed X-ray luminosity L{sub X} = (2.6 ± 0.8) × 10{sup 34} erg s{sup –1} assuming a distance of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A–E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to ∼100 kyr) with low surface brightness and radii up to ∼30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.

  15. NuSTAR detection of high-energy X-ray emission and rapid variability from Sagittarius A{sup *} flares

    SciTech Connect

    Barrière, Nicolas M.; Tomsick, John A.; Boggs, Steven E.; Craig, William W.; Zoglauer, Andreas; Baganoff, Frederick K.; Christensen, Finn E.; Dexter, Jason; Grefenstette, Brian; Harrison, Fiona A.; Madsen, Kristin K.; Hailey, Charles J.; Mori, Kaya; Zhang, Shuo; Stern, Daniel; Zhang, William W.

    2014-05-01

    Sagittarius A{sup *} harbors the supermassive black hole that lies at the dynamical center of our Galaxy. Sagittarius A{sup *} spends most of its time in a low luminosity emission state but flares frequently in the infrared and X-ray, increasing up to a few hundred fold in brightness for up to a few hours at a time. The physical processes giving rise to the X-ray flares are uncertain. Here we report the detection with the NuSTAR observatory in Summer and Fall 2012 of four low to medium amplitude X-ray flares to energies up to 79 keV. For the first time, we clearly see that the power-law spectrum of Sagittarius A{sup *} X-ray flares extends to high energy, with no evidence for a cutoff. Although the photon index of the absorbed power-law fits are in agreement with past observations, we find a difference between the photon index of two of the flares (significant at the 95% confidence level). The spectra of the two brightest flares (∼55 times quiescence in the 2-10 keV band) are compared to simple physical models in an attempt to identify the main X-ray emission mechanism, but the data do not allow us to significantly discriminate between them. However, we confirm the previous finding that the parameters obtained with synchrotron models are, for the X-ray emission, physically more reasonable than those obtained with inverse Compton models. One flare exhibits large and rapid (<100 s) variability, which, considering the total energy radiated, constrains the location of the flaring region to be within ∼10 Schwarzschild radii of the black hole.

  16. Deducing dust emission mechanisms from field measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field observations are needed to both develop and test theories on dust emission for use in global modeling systems. The mechanism of dust emission (aerodynamic entrainment, saltation bombardment, aggregate disintegration) and the amount and particle-size distribution of emitted dust may vary under ...

  17. GRB 110709A, 111117A, AND 120107A: FAINT HIGH-ENERGY GAMMA-RAY PHOTON EMISSION FROM FERMI-LAT OBSERVATIONS AND DEMOGRAPHIC IMPLICATIONS

    SciTech Connect

    Zheng Weikang; Akerlof, Carl W.; McKay, Timothy A.; Pandey, Shashi B.; Zhang Binbin; Zhang Bing; Sakamoto, Takanori

    2012-09-01

    Launched on 2008 June 11, the Large Area Telescope (LAT) instrument on board the Fermi Gamma-ray Space Telescope has provided a rare opportunity to study high-energy photon emission from gamma-ray bursts (GRBs). Although the majority of such events (27) have been identified by the Fermi-LAT Collaboration, four were uncovered by using more sensitive statistical techniques. In this paper, we continue our earlier work by finding three more GRBs associated with high-energy photon emission, GRB 110709A, 111117A, and 120107A. To systematize our matched filter approach, a pipeline has been developed to identify these objects in nearly real time. GRB 120107A is the first product of this analysis procedure. Despite the reduced threshold for identification, the number of GRB events has not increased significantly. This relative dearth of events with low photon number prompted a study of the apparent photon number distribution. We find an extremely good fit to a simple power law with an exponent of -1.8 {+-} 0.3 for the differential distribution. As might be expected, there is a substantial correlation between the number of lower energy photons detected by the Gamma-ray Burst Monitor (GBM) and the number observed by LAT. Thus, high-energy photon emission is associated with some but not all of the brighter GBM events. Deeper studies of the properties of the small population of high-energy emitting bursts may eventually yield a better understanding of these entire phenomena.

  18. GRB 110709A, 111117A, and 120107A: Faint High-energy Gamma-Ray Photon Emission from Fermi-LAT Observations and Demographic Implications

    NASA Astrophysics Data System (ADS)

    Zheng, WeiKang; Akerlof, Carl W.; Pandey, Shashi B.; McKay, Timothy A.; Zhang, BinBin; Zhang, Bing; Sakamoto, Takanori

    2012-09-01

    Launched on 2008 June 11, the Large Area Telescope (LAT) instrument on board the Fermi Gamma-ray Space Telescope has provided a rare opportunity to study high-energy photon emission from gamma-ray bursts (GRBs). Although the majority of such events (27) have been identified by the Fermi-LAT Collaboration, four were uncovered by using more sensitive statistical techniques. In this paper, we continue our earlier work by finding three more GRBs associated with high-energy photon emission, GRB 110709A, 111117A, and 120107A. To systematize our matched filter approach, a pipeline has been developed to identify these objects in nearly real time. GRB 120107A is the first product of this analysis procedure. Despite the reduced threshold for identification, the number of GRB events has not increased significantly. This relative dearth of events with low photon number prompted a study of the apparent photon number distribution. We find an extremely good fit to a simple power law with an exponent of -1.8 ± 0.3 for the differential distribution. As might be expected, there is a substantial correlation between the number of lower energy photons detected by the Gamma-ray Burst Monitor (GBM) and the number observed by LAT. Thus, high-energy photon emission is associated with some but not all of the brighter GBM events. Deeper studies of the properties of the small population of high-energy emitting bursts may eventually yield a better understanding of these entire phenomena.

  19. Effects of high energy radiation on the mechanical properties of epoxy/graphite fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Fornes, R. E.; Gilbert, R. D.; Memory, J. D.

    1986-01-01

    The epoxy resin system formed by tetraglycidyl 4,4'-diamino diphenyl methane (TGDDM) and 4,4'-diamino diphenyl sulfone (DDS) was characterized by dynamic mechanical analysis and differential scanning calorimetry. Dynamic mechanical properties of graphite fiber epoxy composite specimens formulated with two different adhesive systems (NARMCO 5208, NARMCO 5209) were determined. The specimens were exposed to varying dose levels of ionizing radiation (0.5 MeV electrons) with a maximum absorbed dose of 10,000 Mrads. Following irradiation, property measurements were made to assess the influence of radiation on the epoxy and composite specimens. The results established that ionizing radiation has a limited effect on the properties of epoxy and composite specimens.

  20. Effects of high energy radiation on the mechanical properties of epoxy-graphite fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Fornes, R. E.; Gilbert, R. D.; Memory, J. D.

    1985-01-01

    In an effort to elucidate the changes in molecular structural and mechanical properties of epoxy/graphite fiber composites upon exposure to ionizing radiation in a simulated space environment, spectroscopic and surface properties of tetraglycidyl-4,4'-diamino diphenyl methane (TGDDM) red with diamino diphenyl sulfone (DDS) and T-300 graphite fiber were investigated following exposure to ionizing radiation. Cobalt-60 gamma radiation and 1/2 MeV electrons were used as radiation sources. The system was studied using electron spin resonance (ESR) spectroscopy, infrared absorption spectroscopy, contact angle measurements, and electron spectroscopy for chemical analysis.

  1. A Statistical Mechanics Framework for Multiparticle Production in High Energy Hadron Reactions

    NASA Astrophysics Data System (ADS)

    Buccella, F.; Popova, L.

    We deduce the particle distributions in particle collisions with multihadron-production in the framework of mechanical statistics. They are derived as functions of x, PT2 and the rest mass of different species for a fixed total number of all produced particles, inelasticity and total transverse energy. For PT larger than the mass of each particle, we have \\[ \\frac{dn_i}{dP_T} \\sim \\sqrt{P_T} e^{-\\frac{P_T}{T_H}} . \\] Values of π, K and < PT>_{¯ p} in agreement with experiment are found by taking TH = 180 MeV (the Hagedorn temperature).

  2. Demographics of high-energy mechanisms of injury in the Kids Inpatient Database.

    PubMed

    Leung, Brian; Koval, Kenneth J; Carney, Brian; Spratt, Kevin F

    2006-01-01

    The purpose of this study was to review the relationship of patient demographics to mechanism of injury (MOI). The 2000 Kids Inpatient Database (KID) was used. Logistic regression was used to evaluate the relationship between each MOI relative to other MOIs for each of five identified predictors (age, gender, race, socioeconomic status, geographic region). The KID had 87,795 children with a MOI coded and complete data for all predictors. For motor vehicle accidents, 16- to 20-year-olds were up to 3.72 times more likely to be involved than any other age group, and males were 40% less likely compared with females. For firearm hospitalizations, 16- to 20-year-old black males have significantly higher risk compared with all other identified groups. PMID:17087885

  3. Production of the High Energy-Momentum Spectra of Quasars 3C 279 and 3C 273 Using the Penrose Mechanism

    NASA Astrophysics Data System (ADS)

    Williams, R. K.

    2000-05-01

    Monte Carlo computer model simulations show that Penrose Compton scattering (PCS) near the event horizon and Penrose pair production (PPP) at or near the photon orbit, in the ergosphere of a supermassive (M=108 Msun) rotating black hole, can generate the necessary energy-momentum spectra to explain the origin of the mysterious fluxes of ultrarelativistic electrons, inferred from observations to emerge from the cores of Quasars 3C 279 and 3C 273, and other active galactic nuclei (AGNs). Particles from an accretion disk surrounding the black hole fall into the ergosphere and scatter off particles that are in trapped or bound unstable orbits. The Penrose mechanism allows rotational energy of a Kerr black hole, and energy-momentum produced by its strong gravitational field, to be extracted by scattered particles escaping from the ergosphere to infinity (i.e., large distances from the black hole). The results of these model calculations show that the Penrose mechanism is capable of producing the observed high energy particles ( ~ GeV) emitted by quasars and other AGNs. This mechanism can extract hard X-ray/⪆ -ray photons from PCS of initially infalling low energy UV/soft X-ray photons by target orbiting electrons in the ergosphere. The PPP (⪆ ⪆ --> e-e^+) allows the escape of relativistic e- e+ pairs---produced by infalling low energy photons interacting with highly blueshifted target photons at the photon orbit. These e- e+ pairs emerge with maximum Lorentz factor ~ 104, which are consistent with relativistic beaming models used to explain the high energy spectra of so-called blazars, such as 3C 279 and 3C 273. Moreover, and importantly, the emission of scattered particles by this mechanism naturally produces relativistic jets collimated about the polar axis, and in most cases one-sided or asymmetrical, agreeing with observations of AGNs. In these fully relativistic calculations, the energy-momentum four vectors (or four-momenta) of the scattered particles are

  4. Heating of the Hot Intergalactic Medium by Powerful Radio Galaxies and Associated High-Energy Gamma-Ray Emission

    NASA Astrophysics Data System (ADS)

    Inoue, Susumu; Sasaki, Shin

    2001-12-01

    There is increasing evidence that some heating mechanism in addition to gravitational shock heating has been important for the hot gas inside clusters and groups of galaxies, as indicated by their observed X-ray scaling properties. While supernovae are the most obvious candidate heating sources, a number of recent studies have suggested that they may be energetically insufficient. Here we consider high-power, FR II radio galaxies and shock heating of the intracluster medium (ICM including the case of the intergalactic medium prior to cluster formation) by their large-scale jets. Based on the observed statistics of radio galaxies in clusters and their evolution, along with the most reasonable assumptions, it is shown that they can provide the ICM with excess specific energies of 1-2 keV particle-1, mainly during the redshift interval z~1-3. This naturally meets the requirements of cluster evolution models with nongravitational feedback in accounting for the observed deviations in the X-ray luminosity-temperature relation. In contrast to supernovae, such large-scale jets deposit their energy directly into the low-density ICM outside galaxies and are much less susceptible to radiative losses. As a clear and potentially decisive test of this scenario, we propose the observation of ``prompt'' high-energy gamma rays emitted by shock-accelerated, nonthermal electrons during the epoch of ICM heating by radio galaxies, which may be feasible with the GLAST satellite. Implications for recent detections of excess hard X-rays from groups are also discussed.

  5. Characterization of Al and Fe nanosized powders synthesized by high energy mechanical milling

    SciTech Connect

    Mhadhbi, Mohsen; Khitouni, Mohamed Azabou, Myriam; Kolsi, Abdelwaheb

    2008-07-15

    The process of nanocrystalline structure formation during mechanical milling was studied in Al and Fe powders. A detailed microstructural study of powder samples was carried out by X-ray diffraction experiments as a function of milling time. As a result, nanosized powders have been synthesized with microstructures showing a significant decrease of the coherent diffraction domains and the creation of a large number of linear defects, which induce microstrains. SEM results show that welding of very small particles to the surfaces of larger particles occurred and that the powder particles tended to form a matrix of randomly welded thin layers of highly deformed particles. Calorimetric measurements, as a function of milling time, indicated the decrease of the melting point of Al powder and at early stages it can be seen that initially endothermic peak was divided to two endothermic melting peaks. This is probably due to the oxide layer around the Al grains. In the case of Fe powder, the DSC measurements show a broad exothermal peak occurring over quite a large temperature interval, corresponding to the strain release and grain growth.

  6. High energy emission of GRB 130821A: Constraining the density profile of the circum-burst medium as well as the initial Lorentz factor of the outflow

    SciTech Connect

    Liang, Yun-Feng; Zhou, Bei; He, Hao-Ning; Fan, Yi-Zhong; Wei, Da-Ming; Tam, Pak-Hin Thomas

    2014-02-01

    GRB 130821A was detected by Fermi-GBM/LAT, Konus-WIND, SPI-ACS/INTEGRAL, RHESSI and Mars Odyssey-HEND. Although the data of GRB 130821A are very limited, we show in this work that the high energy γ-ray emission (i.e., above 100 MeV) alone imposes tight constraint on the density profile of the circum-burst medium as well as the initial Lorentz factor of the outflow. The temporal behavior of the high energy γ-ray emission is consistent with the forward shock synchrotron radiation model, and the circum-burst medium likely has a constant-density profile. The Lorentz factor is about a few hundred, similar to other bright GRBs.

  7. Radio imaging of the very-high-energy gamma-ray emission region in the central engine of a radio galaxy.

    PubMed

    Acciari, V A; Aliu, E; Arlen, T; Bautista, M; Beilicke, M; Benbow, W; Bradbury, S M; Buckley, J H; Bugaev, V; Butt, Y; Byrum, K; Cannon, A; Celik, O; Cesarini, A; Chow, Y C; Ciupik, L; Cogan, P; Cui, W; Dickherber, R; Fegan, S J; Finley, J P; Fortin, P; Fortson, L; Furniss, A; Gall, D; Gillanders, G H; Grube, J; Guenette, R; Gyuk, G; Hanna, D; Holder, J; Horan, D; Hui, C M; Humensky, T B; Imran, A; Kaaret, P; Karlsson, N; Kieda, D; Kildea, J; Konopelko, A; Krawczynski, H; Krennrich, F; Lang, M J; LeBohec, S; Maier, G; McCann, A; McCutcheon, M; Millis, J; Moriarty, P; Ong, R A; Otte, A N; Pandel, D; Perkins, J S; Petry, D; Pohl, M; Quinn, J; Ragan, K; Reyes, L C; Reynolds, P T; Roache, E; Roache, E; Rose, H J; Schroedter, M; Sembroski, G H; Smith, A W; Swordy, S P; Theiling, M; Toner, J A; Varlotta, A; Vincent, S; Wakely, S P; Ward, J E; Weekes, T C; Weinstein, A; Williams, D A; Wissel, S; Wood, M; Walker, R C; Davies, F; Hardee, P E; Junor, W; Ly, C; Aharonian, F; Akhperjanian, A G; Anton, G; Barres de Almeida, U; Bazer-Bachi, A R; Becherini, Y; Behera, B; Bernlöhr, K; Bochow, A; Boisson, C; Bolmont, J; Borrel, V; Brucker, J; Brun, F; Brun, P; Bühler, R; Bulik, T; Büsching, I; Boutelier, T; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L-M; Clapson, A C; Coignet, G; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dyks, J; Dyrda, M; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Füssling, M; Gabici, S; Gallant, Y A; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göhring, D; Hauser, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Holleran, M; Hoppe, S; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jung, I; Katarzyński, K; Katz, U; Kaufmann, S; Kendziorra, E; Kerschhaggl, M; Khangulyan, D; Khélifi, B; Keogh, D; Kluźniak, W; Kneiske, T; Komin, Nu; Kosack, K; Lamanna, G; Lenain, J-P; Lohse, T; Marandon, V; Martin, J M; Martineau-Huynh, O; Marcowith, A; Maurin, D; McComb, T J L; Medina, M C; Moderski, R; Moulin, E; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Olive, J-F; de Oña Wilhelmi, E; Orford, K J; Ostrowski, M; Panter, M; Paz Arribas, M; Pedaletti, G; Pelletier, G; Petrucci, P-O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raubenheimer, B C; Raue, M; Rayner, S M; Renaud, M; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Sahakian, V; Santangelo, A; Schlickeiser, R; Schöck, F M; Schröder, R; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sikora, M; Skilton, J L; Sol, H; Spangler, D; Stawarz, Ł; Steenkamp, R; Stegmann, C; Stinzing, F; Superina, G; Szostek, A; Tam, P H; Tavernet, J-P; Terrier, R; Tibolla, O; Tluczykont, M; van Eldik, C; Vasileiadis, G; Venter, C; Venter, L; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A; Anderhub, H; Antonelli, L A; Antoranz, P; Backes, M; Baixeras, C; Balestra, S; Barrio, J A; Bastieri, D; Becerra González, J; Becker, J K; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Bock, R K; Bonnoli, G; Bordas, P; Borla Tridon, D; Bosch-Ramon, V; Bose, D; Braun, I; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Commichau, S; Contreras, J L; Cortina, J; Costado, M T; Covino, S; Curtef, V; Dazzi, F; De Angelis, A; De Cea del Pozo, E; Delgado Mendez, C; De los Reyes, R; De Lotto, B; De Maria, M; De Sabata, F; Dominguez, A; Dorner, D; Doro, M; Elsaesser, D; Errando, M; Ferenc, D; Fernández, E; Firpo, R; Fonseca, M V; Font, L; Galante, N; García López, R J; Garczarczyk, M; Gaug, M; Goebel, F; Hadasch, D; Hayashida, M; Herrero, A; Hildebrand, D; Höhne-Mönch, D; Hose, J; Hsu, C C; Jogler, T; Kranich, D; La Barbera, A; Laille, A; Leonardo, E; Lindfors, E; Lombardi, S; Longo, F; López, M; Lorenz, E; Majumdar, P; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Miranda, J M; Mirzoyan, R; Miyamoto, H; Moldón, J; Moles, M; Moralejo, A; Nieto, D; Nilsson, K; Ninkovic, J; Oya, I; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pegna, R G; Perez-Torres, M A; Persic, M; Peruzzo, L; Prada, F; Prandini, E; Puchades, N; Reichardt, I; Rhode, W; Ribó, M; Rico, J; Rissi, M; Robert, A; Rügamer, S; Saggion, A; Saito, T Y; Salvati, M; Sanchez-Conde, M; Satalecka, K; Scalzotto, V; Scapin, V; Schweizer, T; Shayduk, M; Shore, S N; Sidro, N; Sierpowska-Bartosik, A; Sillanpää, A; Sitarek, J; Sobczynska, D; Spanier, F; Stamerra, A; Stark, L S; Takalo, L; Tavecchio, F; Temnikov, P; Tescaro, D; Teshima, M; Torres, D F; Turini, N; Vankov, H; Wagner, R M; Zabalza, V

    2009-07-24

    The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole. PMID:19574351

  8. Mechanical Design of a High Energy Beam Absorber for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab

    SciTech Connect

    Baffes, C.; Church, M.; Leibfritz, J.; Oplt, S.; Rakhno, I.; /Fermilab

    2012-05-10

    A high energy beam absorber has been built for the Advanced Superconducting Test Accelerator (ASTA) at Fermilab. In the facility's initial configuration, an electron beam will be accelerated through 3 TTF-type or ILC-type SRF cryomodules to an energy of 750MeV. The electron beam will be directed to one of multiple downstream experimental and diagnostic beam lines and then deposited in one of two beam absorbers. The facility is designed to accommodate up to 6 cryomodules, which would produce a 75kW beam at 1.5GeV; this is the driving design condition for the beam absorbers. The beam absorbers consist of water-cooled graphite, aluminum and copper layers contained in a helium-filled enclosure. This paper describes the mechanical implementation of the beam absorbers, with a focus on thermal design and analysis. The potential for radiation-induced degradation of the graphite is discussed.

  9. Investigation of the 2p_{32}-3d_{52} line emission of Au;{53+}-Au;{69+} for diagnosing high energy density plasmas.

    PubMed

    Brown, G V; Hansen, S B; Träbert, E; Beiersdorfer, P; Widmann, K; Chen, H; Chung, H K; Clementson, J H T; Gu, M F; Thorn, D B

    2008-06-01

    Measurements of the L -shell emission of highly charged gold ions were made under controlled laboratory conditions using the SuperEBIT electron beam ion trap, allowing detailed spectral observations of lines from Fe-like Au53+ through Ne-like Au69+ . Using atomic data from the Flexible Atomic Code, we have identified strong 3d_{52}-->2p_{32} emission features that can be used to diagnose the charge state distribution in high energy density plasmas, such as those found in the laser entrance hole of hot hohlraum radiation sources. We provide collisional-radiative calculations of the average ion charge Z as a function of temperature and density, which can be used to relate charge state distributions inferred from 3d_{52}-->2p_{32} emission features to plasma conditions, and investigate the effects of plasma density on calculated L -shell Au emission spectra. PMID:18643382

  10. A System for Conducting Sophisticated Mechanical Tests in Situ with High Energy Synchrotron X-Rays Final Technical Report

    SciTech Connect

    Jeremy Weiss

    2012-08-02

    This is the final technical report for the SBIR Phase I project titled 'A System for Conducting Sophisticated Mechanical Tests in Situ with High Energy Synchrotron X-Rays.' Experiments using diffraction of synchrotron radiation that help scientists understand engineering material failure modes, such as fracture and fatigue, require specialized machinery. This machinery must be able to induce these failure modes in a material specimen while adhering to strict size, weight, and geometric limitations prescribed by diffraction measurement techniques. During this Phase I project, Mechanical Solutions, Inc. (MSI) developed one such machine capable of applying uniaxial mechanical loading to a material specimen in both tension and compression, with zero backlash while transitioning between the two. Engineers currently compensate for a lack of understanding of fracture and fatigue by employing factors of safety in crucial system components. Thus, mechanical and structural parts are several times bigger, thicker, and heavier than they need to be. The scientific discoveries that result from diffraction experiments which utilize sophisticated mechanical loading devices will allow for broad material, weight, fuel, and cost savings in engineering design across all industries, while reducing the number of catastrophic failures in transportation, power generation, infrastructure, and all other engineering systems. With an existing load frame as the starting point, the research focused on two main areas: (1) the design of a specimen alignment and gripping system that enables pure uniaxial tension and compression loading (and no bending, shear, or torsion), and (2) development of a feedback control system that is adaptive and thus can maintain a load set point despite changing specimen material properties (e.g. a decreasing stiffness during yield).

  11. Mössbauer analysis of high-energy mechanical-milled sand fraction of a magnetic soil developing on basalt

    NASA Astrophysics Data System (ADS)

    Borges, José Flávio Marcelino; Hneda, Marlon Luiz; Brinatti, André Maurício; Cunha, João Batista Marimon da; Rosa, Jadir Aparecido; Fabris, José Domingos

    2011-11-01

    A sample of the coarse sand fraction from the soil material of the A-horizon (0-0.2 m from the soil surface) of a dusky red magnetic Oxisol was submitted to high-energy mechanical milling for different times. This assay aimed mainly at (a) monitoring the individualization of strongly aggregated mineral particles, and (b) measuring the effect of the milling pressure on the mineralogy changes of the material. These data are also intended to experimentally subside any physical model describing the mechanical behavior of the superficial soil layer that is subjected to intensive machine management, in agriculture fields. Powder X-ray data reveal that some mineralogical phases, notably gibbsite, disappear soon after the first few hours milling. The 298 K-transmission Mössbauer spectrum for the non-milled sand sample shows a qualitatively typical pattern for the sand fraction of basalt derived soils, with magnetically ordered sextets, assignable mainly to hematite and maghemite, and an intense central (super)paramagnetic Fe3 + doublet. For the milled samples, spectra revealed progressive spectral reduction of the magnetic hyperfine structure, with concomitant increase of relative subspectral areas due to (super)paramagnetic phases, as the milling time increased. This result is consistent with the reduction of measured saturation magnetization, from 4.96(8) J T - 1 kg - 1, for the non-milled sample, to 3.26(7) J T - 1 kg - 1, for the sample milled for 8 hours.

  12. A search for short-term variability in the very high energy γ-ray emission from the Crab nebula

    NASA Astrophysics Data System (ADS)

    O'Faoláin de Bhróithe, Anna; VERITAS Collaboration

    2012-12-01

    The Crab Nebula has long been considered a standard candle in high energy astrophysics, but in recent years this assumpation has been strongly contradicted in keV-GeV wavebands. In light of these developments, a search for variability is being performed on the nebula at Very High Energies (VHE; E > 300 GeV), the preliminary results of which are presented here. This initial study is based on 10 years (2001-2011) of archival data from the Whipple 10m telescope. The data set was searched for evidence of variability on the timescales of 1, 7, and 14 days. To date, no significant flaring activity has been found, but simulations are in progress to determine the level of variability that would be detected.

  13. Effect of high energy X-ray irradiation on the nano-mechanical properties of human enamel and dentine.

    PubMed

    Liang, Xue; Zhang, Jing Yang; Cheng, Iek Ka; Li, Ji Yao

    2016-01-01

    Radiotherapy for malignancies in the head and neck can cause common complications that can result in tooth damage that are also known as radiation caries. The aim of this study was to examine damage to the surface topography and calculate changes in friction behavior and the nano-mechanical properties (elastic modulus, nanohardness and friction coefficient) of enamel and dentine from extracted human third molars caused by exposure to radiation. Enamel and dentine samples from 50 human third molars were randomly assigned to four test groups or a control group. The test groups were exposed to high energy X-rays at 2 Gy/day, 5 days/week for 5 days (10 Gy group), 15 days (30 Gy group), 25 days (50 Gy group), 35 days (70 Gy group); the control group was not exposed. The nanohardness, elastic modulus, and friction coefficient were analyzed using a Hysitron Triboindenter. The nano-mechanical properties of both enamel and dentine showed significant dose-response relationships. The nanohardness and elastic modulus were most variable between 30-50 Gy, while the friction coefficient was most variable between 0-10 Gy for dentine and 30-50 Gy for enamel. After exposure to X-rays, the fracture resistance of the teeth clearly decreased (rapidly increasing friction coefficient with increasing doses under the same load), and they were more fragile. These nano-mechanical changes in dental hard tissue may increase the susceptibility to caries. Radiotherapy caused nano-mechanical changes in dentine and enamel that were dose related. The key doses were 30-50 Gy and the key time points occurred during the 15th-25th days of treatment, which is when application of measures to prevent radiation caries should be considered. PMID:26676192

  14. Emission of High-Energy Ions in the SHOTGUN III Divergent Gas-Puff Z-Pinch Experiment

    NASA Astrophysics Data System (ADS)

    TAKASUGI, Keiichi; IWATA, Masayuki; NISHIO, Mineyuki

    2016-03-01

    Ion pinhole measurements of high-energy ions were conducted on the divergent gas-puff z-pinch plasma. Two types of ions, 1.7 - 2.5 MeV and 0.1 - 0.7 MeV, were observed. The former was observed only on the axis. The latter showed quite different characteristics between positive and negative discharges. These ions were considered to be accelerated by inductive electric field generated by the pinch.

  15. What is learned from high energy bursts and flares

    NASA Technical Reports Server (NTRS)

    Schneid, Edward J.

    1990-01-01

    The Energetic Gamma Ray Experiment Telescope (EGRET) with its large Nal Total Absorption Shower Counter (TASC) has the scientific capability of performing spectroscopy of high energy cosmic gamma ray bursts and solar flares. EGRET, with a spectroscopy energy range from 0.6 to 140 MeV, provides an opportunity to increase the understanding of the high energy mechanisms of gamma ray bursts and solar flares. A likely interpretation of gamma ray burst sources is that they are rotating, magnetized neutron stars. High magnetic fields can influence the emission of high energy gamma rays, so observational spectroscopic data at high energies can provide information on the upper limits of the magnetic fields in the GRB regions of magnetized neutron stars. Likewise, spectroscopy of high energy gamma rays can provide information useful for deriving the flare proton spectrum which in turn can lead to an understanding of high energy solar flare particle acceleration mechanisms.

  16. Observational Signatures of High-Energy Emission during the Shallow Decay Phase of Gamma-Ray Burst X-Ray Afterglows

    NASA Astrophysics Data System (ADS)

    Yu, Y. W.; Liu, X. W.; Dai, Z. G.

    2007-12-01

    The widely existing shallow decay phase of the X-ray afterglows of gamma-ray bursts (GRBs) is generally accepted to be due to long-lasting energy injection. The outflows carrying the injecting energy, based on the component that is dominant in energy, fall into two possible types: baryon-dominated and lepton-dominated ones. The former type of outflow could be ejecta that is ejected during the prompt phase of a GRB and consists of a series of baryonic shells with a distribution of Lorentz factors, and the latter type could be an electron-positron pair wind that is driven by the postburst central engine. We here provide a unified description for the dynamics of fireballs based on these two types of energy injection and calculate the corresponding high-energy photon emission by considering synchrotron radiation and inverse Compton scattering (including synchrotron self-Compton and combined inverse Compton) of electrons. We find that, in the two energy-injection models, there is a plateau (even a hump) in high-energy light curves during the X-ray shallow decay phase. In particular, a considerable fraction of the injecting energy in the lepton-dominated model can be shared by the long-lasting reverse shock since it is relativistic. Furthermore, almost all of the energy of the reverse shock is carried by leptons, and thus, the inverse Compton emission is enhanced dramatically. Therefore, this model predicts more significant high-energy afterglow emission than the baryon-dominated model. We argue that these observational signatures would be used to discriminate between different energy-injection models in the upcoming Gamma-Ray Large Area Space Telescope (GLAST) era.

  17. Imaging of high-energy x-ray emission from cryogenic thermonuclear fuel implosions on the NIF.

    PubMed

    Ma, T; Izumi, N; Tommasini, R; Bradley, D K; Bell, P; Cerjan, C J; Dixit, S; Döppner, T; Jones, O; Kline, J L; Kyrala, G; Landen, O L; LePape, S; Mackinnon, A J; Park, H-S; Patel, P K; Prasad, R R; Ralph, J; Regan, S P; Smalyuk, V A; Springer, P T; Suter, L; Town, R P J; Weber, S V; Glenzer, S H

    2012-10-01

    Accurately assessing and optimizing the implosion performance of inertial confinement fusion capsules is a crucial step to achieving ignition on the NIF. We have applied differential filtering (matched Ross filter pairs) to provide broadband time-integrated absolute x-ray self-emission images of the imploded core of cryogenic layered implosions. This diagnostic measures the temperature- and density-sensitive bremsstrahlung emission and provides estimates of hot spot mass, mix mass, and pressure. PMID:23126937

  18. Imaging of high-energy x-ray emission from cryogenic thermonuclear fuel implosions on the NIF

    SciTech Connect

    Ma, T.; Izumi, N.; Tommasini, R.; Bradley, D. K.; Bell, P.; Cerjan, C. J.; Dixit, S.; Doeppner, T.; Jones, O.; Landen, O. L.; LePape, S.; Mackinnon, A. J.; Park, H.-S.; Patel, P. K.; Prasad, R. R.; Ralph, J.; Smalyuk, V. A.; Springer, P. T.; Suter, L.; Town, R. P. J.; and others

    2012-10-15

    Accurately assessing and optimizing the implosion performance of inertial confinement fusion capsules is a crucial step to achieving ignition on the NIF. We have applied differential filtering (matched Ross filter pairs) to provide broadband time-integrated absolute x-ray self-emission images of the imploded core of cryogenic layered implosions. This diagnostic measures the temperature- and density-sensitive bremsstrahlung emission and provides estimates of hot spot mass, mix mass, and pressure.

  19. Possible radio emission mechanism for pulsars

    NASA Technical Reports Server (NTRS)

    Kovalev, Y. A.

    1979-01-01

    A mathematical model is presented and discussed as a possible mechanism to describe radio emission from pulsars. The model determines that the magnetic field in the neutron proton electron (npe) layer of a neutron star results from a quasistationary eddy current of superconducting and normal protons relative to normal electrons, which generates radio emission by the Josephson effect. The radiation propagates in the magnetically active medium, from the optically thick npe layer to the magnetosphere through breaks in the crust. As a result, hot radio spots form on the surface of the star, and a radiation pattern forms near the magnetic poles, the cross section of which gives the observed pulse structure. Due to the specific properties of the mechanism, variations of the quasistationary current are converted to amplitude frequency variations of the radiation spectrum. Variations of the fine structure of the spectrum pulse amplitude and spectral index, as well as their correlation are discussed.

  20. A SEARCH FOR ENHANCED VERY HIGH ENERGY GAMMA-RAY EMISSION FROM THE 2013 MARCH CRAB NEBULA FLARE

    SciTech Connect

    Aliu, E.; Errando, M.; Archambault, S.; Aune, T.; Benbow, W.; Cerruti, M.; Berger, K.; Bird, R.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Feng, Q.; Dumm, J.; Falcone, A.; Federici, S. E-mail: gtrichards@gatech.edu; and others

    2014-01-20

    In 2013 March, a flaring episode from the Crab Nebula lasting ∼2 weeks was detected by Fermi-LAT (Large Area Telescope on board the Fermi Gamma-ray Space Telescope). The Very Energetic Radiation Imaging Telescope Array System (VERITAS) provides simultaneous observations throughout this period. During the flare, Fermi-LAT detected a 20 fold increase in flux above the average synchrotron flux >100 MeV seen from the Crab Nebula. Simultaneous measurements with VERITAS are consistent with the non-variable long-term average Crab Nebula flux at TeV energies. Assuming a linear correlation between the very high energy flux change >1 TeV and the flux change seen in the Fermi-LAT band >100 MeV during the period of simultaneous observations, the linear correlation factor can be constrained to be at most 8.6 × 10{sup –3} with 95% confidence.

  1. Discovery of Very High Energy Gamma-Ray Emission in the W 28 (G6.4-0.1) Region and Multiwavelength Comparisons

    SciTech Connect

    Rowell, G.; Brion, E.; Reimer, O.; Moriguchi, Y.; Fukui, Yasuo; Djannati-Atai, A.; Funk, S.; /Stanford U., HEPL /KIPAC, Menlo Park

    2007-10-29

    H.E.S.S. observations of the old-age (>10{sup 4} yr; {approx} 0.5 degree diameter) composite supernova remnant (SNR)W28 reveal very high energy (VHE) {gamma}-ray emission situated at its northeastern and southern boundaries. The northeastern VHE source (HESS J1801-233) is in an area where W 28 is interacting with a dense molecular cloud, containing OH masers, local radio and X-ray peaks. The southern VHE sources (HESS J1800-240 with components labeled A, B and C) are found in a region occupied by several HII regions, including the ultracompact HII region W 28A2. Our analysis of NANTEN CO data reveals a dense molecular cloud enveloping this southern region, and our reanalysis of EGRET data reveals MeV/GeV emission centered on HESS J1801-233 and the northeastern interaction region.

  2. Discovery of very high energy γ-ray emission from the BL Lacertae object PKS 0301-243 with H.E.S.S.

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giebels, B.; Glicenstein, J. F.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hague, J. D.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Nedbal, D.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2013-11-01

    The active galactic nucleus PKS 0301-243 (z = 0.266) is a high-synchrotron-peaked BL Lac object that is detected at high energies (HE, 100 MeV high energies (E > 100 GeV) by the High Energy Stereoscopic System (H.E.S.S.) from observations between September 2009 and December 2011 for a total live time of 34.9 h. Gamma rays above 200 GeV are detected at a significance of 9.4σ. A hint of variability at the 2.5σ level is found. An integral flux I(E > 200 GeV) = (3.3 ± 1.1stat ± 0.7syst) × 10-12 ph cm-2 s-1 and a photon index Γ = 4.6 ± 0.7stat ± 0.2syst are measured. Multi-wavelength light curves in HE, X-ray and optical bands show strong variability, and a minimal variability timescale of eight days is estimated from the optical light curve. A single-zone leptonic synchrotron self-Compton scenario satisfactorily reproduces the multi-wavelength data. In this model, the emitting region is out of equipartition and the jet is particle dominated. Because of its high redshift compared to other sources observed at TeV energies, the very high energy emission from PKS 0301-243 is attenuated by the extragalactic background light (EBL) and the measured spectrum is used to derive an upper limit on the opacity of the EBL.

  3. Interacting Cosmic Rays with Molecular Clouds: A Bremsstrahlung Origin of Diffuse High-energy Emission from the Inner 2°×1° of the Galactic Center

    NASA Astrophysics Data System (ADS)

    Yusef-Zadeh, F.; Hewitt, J. W.; Wardle, M.; Tatischeff, V.; Roberts, D. A.; Cotton, W.; Uchiyama, H.; Nobukawa, M.; Tsuru, T. G.; Heinke, C.; Royster, M.

    2013-01-01

    The high-energy activity in the inner few degrees of the Galactic center is traced by diffuse radio, X-ray, and γ-ray emission. The physical relationship between different components of diffuse gas emitting at multiple wavelengths is a focus of this work. We first present radio continuum observations using the Green Bank Telescope and model the nonthermal spectrum in terms of a broken power-law distribution of ~GeV electrons emitting synchrotron radiation. We show that the emission detected by Fermi is primarily due to nonthermal bremsstrahlung produced by the population of synchrotron emitting electrons in the GeV energy range interacting with neutral gas. The extrapolation of the electron population measured from radio data to low and high energies can also explain the origin of Fe I 6.4 keV line and diffuse TeV emission, as observed with Suzaku, XMM-Newton, Chandra, and the H.E.S.S. observatories. The inferred physical quantities from modeling multiwavelength emission in the context of bremsstrahlung emission from the inner ~300 × 120 pc of the Galactic center are constrained to have the cosmic-ray ionization rate ~1-10 × 10-15 s-1, molecular gas heating rate elevating the gas temperature to 75-200 K, fractional ionization of molecular gas 10-6-10-5, large-scale magnetic field 10-20 μG, the density of diffuse and dense molecular gas ~100 and ~103 cm-3 over 300 pc and 50 pc path lengths, and the variability of Fe I Kα 6.4 keV line emission on yearly timescales. Important implications of our study are that GeV electrons emitting in radio can explain the GeV γ-rays detected by Fermi and that the cosmic-ray irradiation model, like the model of the X-ray irradiation triggered by past activity of Sgr A*, can also explain the origin of the variable 6.4 keV emission from Galactic center molecular clouds.

  4. Investigation of the 2p3/2-3d5/2 line emission of Au53+ -- Au69+ for diagnosing high energy density plasmas

    SciTech Connect

    Brown, G V; Hansen, S B; Trabert, E; Beiersdorfer, P; Widmann, K; Chen, H; Chung, H K; Clementson, J T; Gu, M F; Thorn, D B

    2008-01-29

    Measurements of the L-shell emission of highly charged gold ions were made under controlled laboratory conditions using the SuperEBIT electron beam ion trap, allowing detailed spectral observations of lines from ironlike Au{sup 53+} through neonlike Au{sup 69+}. Using atomic data from the Flexible Atomic Code, we have identified strong 3d{sub 5/2} {yields} 2p{sub 3/2} emission features that can be used to diagnose the charge state distribution in high energy density plasmas, such as those found in the laser entrance hole of hot hohlraum radiation sources. We provide collisional-radiative calculations of the average ion charge as a function of temperature and density, which can be used to relate charge state distributions inferred from 3d{sub 5/2} {yields} 2p{sub 3/2} emission features to plasma conditions, and investigate the effects of plasma density on calculated L-shell Au emission spectra.

  5. High-energy gamma-ray emission from solar flares: Summary of Fermi large area telescope detections and analysis of two M-class flares

    SciTech Connect

    Ackermann, M.; Ajello, M.; Albert, A.; Allafort, A.; Bechtol, K.; Bottacini, E.; Buehler, R.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Buson, S.; Bellazzini, R.; Bregeon, J.; Bissaldi, E.; Bonamente, E.; Bouvier, A.; Brandt, T. J.; Brigida, M.; Bruel, P.; and others

    2014-05-20

    We present the detections of 18 solar flares detected in high-energy γ-rays (above 100 MeV) with the Fermi Large Area Telescope (LAT) during its first 4 yr of operation. This work suggests that particle acceleration up to very high energies in solar flares is more common than previously thought, occurring even in modest flares, and for longer durations. Interestingly, all these flares are associated with fairly fast coronal mass ejections (CMEs). We then describe the detailed temporal, spatial, and spectral characteristics of the first two long-lasting events: the 2011 March 7 flare, a moderate (M3.7) impulsive flare followed by slowly varying γ-ray emission over 13 hr, and the 2011 June 7 M2.5 flare, which was followed by γ-ray emission lasting for 2 hr. We compare the Fermi LAT data with X-ray and proton data measurements from GOES and RHESSI. We argue that the γ-rays are more likely produced through pion decay than electron bremsstrahlung, and we find that the energy spectrum of the proton distribution softens during the extended emission of the 2011 March 7 flare. This would disfavor a trapping scenario for particles accelerated during the impulsive phase of the flare and point to a continuous acceleration process at play for the duration of the flares. CME shocks are known for accelerating the solar energetic particles (SEPs) observed in situ on similar timescales, but it might be challenging to explain the production of γ-rays at the surface of the Sun while the CME is halfway to the Earth. A stochastic turbulence acceleration process occurring in the solar corona is another likely scenario. Detailed comparison of characteristics of SEPs and γ-ray-emitting particles for several flares will be helpful to distinguish between these two possibilities.

  6. Trap-Based Beam Formation Mechanisms and the Development of an Ultra-High-Energy-Resolution Cryogenic Positron Beam

    NASA Astrophysics Data System (ADS)

    Natisin, Michael Ryan

    The focus of this dissertation is the development of a positron beam with significantly improved energy resolution over any beam resolution previously available. While positron interactions with matter are important in a variety of contexts, the range of experimental data available regarding fundamental positron-matter interactions is severely limited as compared to analogous electron-matter processes. This difference is due largely to the difficulties encountered in creating positron beams with narrow energy spreads. Described here is a detailed investigation into the physical processes operative during positron cooling and beam formation in state-of-the-art, trap-based beam systems. These beams rely on buffer gas traps (BGTs), in which positrons are trapped and cooled to the ambient temperature (300 K) through interactions with a molecular gas, and subsequently ejected as a high resolution pulsed beam. Experimental measurements, analytic models, and simulation results are used to understand the creation and characterization of these beams, with a focus on the mechanisms responsible for setting beam energy resolution. The information gained from these experimental and theoretical studies was then used to design, construct, and operate a next-generation high-energy-resolution beam system. In this new system, the pulsed beam from the BGT is magnetically guided into a new apparatus which re-traps the positrons, cools them to 50 K, and re-emits them as a pulsed beam with superior beam characteristics. Using these techniques, positron beams with total energy spreads as low as 6.9 meV FWHM are produced. This represents a factor of ˜ 5 improvement over the previous state-of-the-art, making it the largest increase in positron beam energy resolution since the development of advanced moderator techniques in the early 1980's. These beams also have temporal spreads of 0.9 mus FWHM and radial spreads of 1 mm FWHM. This represents improvements by factors of ˜2 and 10

  7. High Energy Emission of V404 Cygni during 2015 outburst with INTEGRAL/SPI: Spectral analysis results, issues and solutions

    NASA Astrophysics Data System (ADS)

    Jourdain, Elisabeth; Roques, Jean-Pierre

    2016-04-01

    A strong outburst of the X-ray transient V404 Cygni (= GS2023-338) was observed in 2015 June/July up to a level of 50 Crab in the hard X-ray domain.We have used the INTEGRAL/SPI data to investigate the spectral behavior of the source between 20 and 1000 keV during its maximum of activity. We have found striking variability patterns at all timescales. For the 20-200 keV energy band, the huge signal to noise ratio allows us to scrutinize the source evolution on a never reached timescale (30 s). At higher energy, the spectral shape can be determined on a timescale < 1 h.However, we note that at this level of photon flux, instrument's behavior may be severely tested and that some instrumental artifacts could affect the data analysis. We have performed thorough checks to ensure a correct handling of the SPI data and present how to obtain reliable spectral results on the emission of V404 Cyg. We demonstrate that, with the correct configuration, the hard X-ray emission, up to the MeV region, is well described by a two component model (Comptonisation law + cutoff power law) as observed in Cyg X-1 and for V404 Cygni itself at lower flux levels.

  8. Imaging of High-Energy X-Ray Emission from Cryogenic Thermonuclear Fuel Implosions on the NIF

    SciTech Connect

    Ma, T

    2012-05-01

    Accurately assessing and optimizing the implosion performance of inertial confinement fusion capsules is a crucial step to achieving ignition on the NIF. We have applied differential filtering (matched Ross filter pairs) to provide spectrally resolved time-integrated absolute x-ray self-emission images of the imploded core of cryogenic layered targets. Using bremsstrahlung assumptions, the measured absolute x-ray brightness allows for the inference of electron temperature, electron density, hot spot mass, mix mass, and pressure. Current inertial confinement fusion (ICF) experiments conducted on the National Ignition Facility (NIF) seek to indirectly drive a spherical implosion, compressing and igniting a deuterium-tritium fuel. This DT fuel capsule is cryogenically prepared as a solid ice layer surrounded by a low-Z ablator material. Ignition will occur when the hot spot approaches sufficient temperature ({approx}3-4 keV) and {rho}R ({approx}0.3 g/cm{sup 2}) such that alpha deposition can further heat the hot spot and generate a self-sustaining burn wave. During the implosion, the fuel mass becomes hot enough to emit large amounts of x-ray radiation, the spectra and spatial variation of which contains key information that can be used to evaluate the implosion performance. The Ross filter diagnostic employs differential filtering to provide spectrally resolved, time-integrated, absolute x-ray self-emission images of the imploded core of cryogenic layered targets.

  9. A generation mechanism for chorus emission

    NASA Astrophysics Data System (ADS)

    Trakhtengerts, V. Y.

    1999-01-01

    A chorus generation mechanism is discussed, which is based on interrelation of ELF/VLF noise-like and discrete emissions under the cyclotron wave-particle interactions. A natural ELF/VLF noise radiation is excited by the cyclotron instability mechanism in ducts with enhanced cold plasma density or at the plasmapause. This process is accompanied by a step-like deformation of the energetic electron distribution function in the velocity space, which is situated at the boundary between resonant and nonresonant particles. The step leads to the strong phase correlation of interacting particles and waves and to a new backward wave oscillator (BWO) regime of wave generation, when an absolute cyclotron instability arises at the central cross section of the geomagnetic trap, in the form of a succession of discrete signals with growing frequency inside each element. The dynamical spectrum of a separate element is formed similar to triggered ELF/VLF emission, when the strong wavelet starts from the equatorial plane. The comparison is given of the model developed using some satellite and ground-based data. In particular, the appearance of separate groups of chorus signals with a duration 2-10 s can be connected with the preliminary stage of the step formation. BWO regime gives a succession period smaller than the bounce period of energetic electrons between the magnetic mirrors and can explain the observed intervals between chorus elements.

  10. Measurement of the high-energy gamma-ray emission from the Moon with the Fermi Large Area Telescope

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bonino, R.; Bottacini, E.; Bregeon, J.; Bruel, P.; Buehler, R.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Costanza, F.; Cuoco, A.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Digel, S. W.; Di Venere, L.; Drell, P. S.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Franckowiak, A.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Harding, A. K.; Hewitt, J. W.; Horan, D.; Hou, X.; Iafrate, G.; Jóhannesson, G.; Kamae, T.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill, J.; Maldera, S.; Manfreda, A.; Mayer, M.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Murgia, S.; Nuss, E.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Perkins, J. S.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Pivato, G.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Sgrò, C.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Takahashi, H.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Troja, E.; Vianello, G.; Winer, B. L.; Wood, K. S.; Yassine, M.; Cerutti, F.; Ferrari, A.; Sala, P. R.; Fermi LAT Collaboration

    2016-04-01

    We have measured the gamma-ray emission spectrum of the Moon using the data collected by the Large Area Telescope onboard the Fermi satellite during its first seven years of operation, in the energy range from 30 MeV up to a few GeV. We have also studied the time evolution of the flux, finding a correlation with the solar activity. We have developed a full Monte Carlo simulation describing the interactions of cosmic rays with the lunar surface. The results of the present analysis can be explained in the framework of this model, where the production of gamma rays is due to the interactions of cosmic-ray proton and helium nuclei with the surface of the Moon. Finally, we have used our simulation to derive the cosmic-ray proton and helium spectra near Earth from the Moon gamma-ray data.

  11. Discovery of very high energy gamma-ray emission from the blazar 1ES 1727+502 with the MAGIC Telescopes

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Antonelli, L. A.; Antoranz, P.; Asensio, M.; Backes, M.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnefoy, S.; Bonnoli, G.; Borla Tridon, D.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Carreto Fidalgo, D.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Cossio, L.; Covino, S.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Caneva, G.; de Lotto, B.; Delgado Mendez, C.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Eisenacher, D.; Elsaesser, D.; Farina, E.; Ferenc, D.; Fonseca, M. V.; Font, L.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giavitto, G.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadamek, A.; Hadasch, D.; Häfner, D.; Herrero, A.; Hose, J.; Hrupec, D.; Idec, W.; Jankowski, F.; Kadenius, V.; Klepser, S.; Knoetig, M. L.; Krähenbühl, T.; Krause, J.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Masbou, J.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moldón, J.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nilsson, K.; Nowak, N.; Orito, R.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Partini, S.; Persic, M.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reichardt, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamatescu, V.; Stamerra, A.; Steinke, B.; Storz, J.; Sun, S.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Weitzel, Q.; Zandanel, F.; Zanin, R.; MAGIC Collaboration

    2014-03-01

    Motivated by the prediction of a high TeV luminosity we investigated whether the blazar 1ES 1727+502 (z = 0.055) is emitting very high energy (VHE, E > 100 GeV) γ rays. We observed the BL Lac object 1ES 1727+502 in stereoscopic mode with the two MAGIC telescopes for 14 nights between May 6th and June 10th 2011, for a total effective observing time of 12.6 h. To study the multiwavelength spectral energy distribution (SED), we used simultaneous optical R-band data from the KVA telescope, archival UV/optical and X-ray observations from instruments UVOT and XRT on board of the Swift satellite, and high energy (HE, 0.1 GeV-100 GeV) γ-ray data from the Fermi-LAT instrument. We detected, for the first time, VHE γ-ray emission from 1ES 1727+502 at a statistical significance of 5.5σ. The integral flux above 150 GeV is estimated to be (2.1 ± 0.4)% of the Crab nebula flux and the de-absorbed VHE spectrum has a photon index of (2.7 ± 0.5). No significant short-term variability was found in any of the wavebands presented here. We model the SED using a one-zone synchrotron self-Compton model obtaining parameters typical for this class of sources.

  12. What Did We Learn From Chandra, Xmm-Newton And Fermi-Lat About The High Energy Emission In Young Radio Sources?

    NASA Astrophysics Data System (ADS)

    Siemiginowska, Aneta; Guainazzi, M.; Hardcastle, M.; Kelly, B. C.; Kunert-Bajraszewska, M.; Migliori, G.; Sobolewska, M.; Stawarz, L.

    2013-04-01

    Giga-Hertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources comprise a large population of compact objects with radio emission fully contained within the innermost regions of the host galaxy (< a few kpc). Spectral and kinematic age measurements indicate their young age (typically < thousands years and in some cases less a few hundred years). These sources provide the important insights to the initial phase of the jet formation, radio source growth, source evolution and the jet impact on the ISM in the very central regions of the host galaxy. We have obtained Chandra and XMM-Newton observations for a large sample of these sources over several observing cycles. Our most recent Chandra observations targeted Compact Symmetric Objects (CSO) associated with the nuclear regions of nearby galaxies. All these CSO have measured kinematic ages within 100-3000 year old. I will present the results of our ongoing observing program focusing on the high energy properties of these young sources.

  13. Poster — Thur Eve — 18: Cherenkov Emission By High-Energy Radiation Therapy Beams: A Characterization Study

    SciTech Connect

    Zlateva, Y.; El Naqa, I.; Quitoriano, N.

    2014-08-15

    We investigate Cherenkov emission (CE) by radiotherapy beams via radiation dose-versus-CE correlation analyses, CE detection optimization by means of a spectral shift towards the near-infrared (NIR) window of biological tissue, and comparison of CE to on-board MV imaging. Dose-CE correlation was investigated via simulation and experiment. A Monte Carlo (MC) CE simulator was designed using Geant4. Experimental phantoms include: water; tissue-simulating phantom composed of water, Intralipid®, and beef blood; plastic phantom with solid water insert. The detector system comprises an optical fiber and diffraction-grating spectrometer incorporating a front/back-illuminated CCD. The NIR shift was carried out with CdSe/ZnS quantum dots (QDs), emitting at (650±10) nm. CE and MV images were acquired with a CMOS camera and electronic portal imaging device. MC and experimental studies indicate a strong linear dose-CE correlation (Pearson coefficient > 0.99). CE by an 18-MeV beam was effectively NIR-shifted in water and a tissue-simulating phantom, exhibiting a significant increase at 650 nm for QD depths up to 10 mm. CE images exhibited relative contrast superior to MV images by a factor of 30. Our work supports the potential for application of CE in radiotherapy online imaging for patient setup and treatment verification, since CE is intrinsic to the beam and non-ionizing and QDs can be used to improve CE detectability, potentially yielding image quality superior to MV imaging for the case of low-density-variability, low-optical-attenuation materials (ex: breast/oropharynx). Ongoing work involves microenvironment functionalization of QDs and application of multi-channel spectrometry for simultaneous acquisition of dosimetric and tumor oxygenation signals.

  14. Ultraviolet and Visible Emission Mechanisms in Astrophysics

    NASA Technical Reports Server (NTRS)

    Stancil, Phillip C.; Schultz, David R.

    2003-01-01

    The project involved the study of ultraviolet (UV) and visible emission mechanisms in astrophysical and atmospheric environments. In many situations, the emission is a direct consequence of a charge transferring collision of an ion with a neutral with capture of an electron to an excited state of the product ion. The process is also important in establishing the ionization and thermal balance of an astrophysical plasma. As little of the necessary collision data are available, the main thrust of the project was the calculation of total and state-selective charge transfer cross sections and rate coefficients for a very large number of collision systems. The data was computed using modern explicit techniques including the molecular-orbital close-coupling (MOCC), classical trajectory Monte Carlo (CTMC), and continuum distorted wave (CDW) methods. Estimates were also made in some instances using the multichannel Landau-Zener (MCLZ) and classical over-the-barrier (COB) models. Much of the data which has been computed has been formatted for inclusion in a charge transfer database on the World Wide Web (cfadc.phy.ornl.gov/astro/ps/data/). A considerable amount of data has been generated during the lifetime of the grant. Some of it has not been analyzed, but it will be as soon as possible, the data placed on our website, and papers ultimately written.

  15. Control of Y₂O₃ phase and its nanostructure formation through a very high energy mechanical milling

    SciTech Connect

    Lee, M.K.; Park, E.K.; Park, J.J.; Rhee, C.K.

    2013-05-01

    The formation behavior of Y₂O₃ ceramic particles was studied by employing a very high energy ball milling (milling energy: ~165 kJ/g·hit, milling speed: 1000 rpm). Both the XRD and HRTEM studies revealed that the high impact strain energy generated during the milling caused a drastic phase transition from the original C-type cubic (space group Ia3, a=10.58 Å) to the metastable B-type monoclinic (space group C2/m, a=13.89 Å), finally followed by a partial solid-state amorphization. The cubic phase was difficult to be reduced down to smaller than 10 nm, while the monoclinic phase was stabilized at sizes smaller than 10 nm with a mean crystallite size of 7.57 nm. Consequently, the existence of Y₂O₃ at a nanoscale smaller than 10 nm is possible by forming metastable monoclinic crystals, which are strain-induced. - Graphical abstract: The fig shows the solid-state phase formation of Y₂O₃ by very high energy input into the particles during milling: ordered body-centered cubic phase (space group Ia3, a=10.58 Å) nanocrystalline monoclinic phase (space group C2/m, a=13.89 Å) disordered monoclinic phase partial amorphous phase. The formation of Y₂O₃ smaller than 10 nm was strongly dependent on whether the phase transition from cubic to monoclinic occurred. Highlights: • This paper analyses very high energy milling behavior of coarse Y₂O₃ particles. • A drastic phase transition from cubic to monoclinic occurred with a partial amorphization. • An existence of Y₂O₃ smaller than 10 nm is possible by forming strain-induced monoclinic crystals.

  16. High-energy particle production in solar flares (SEP, gamma-ray and neutron emissions). [solar energetic particles

    NASA Technical Reports Server (NTRS)

    Chupp, E. L.

    1987-01-01

    Electrons and ions, over a wide range of energies, are produced in association with solar flares. Solar energetic particles (SEPs), observed in space and near earth, consist of electrons and ions that range in energy from 10 keV to about 100 MeV and from 1 MeV to 20 GeV, respectively. SEPs are directly recorded by charged particle detectors, while X-ray, gamma-ray, and neutron detectors indicate the properties of the accelerated particles (electrons and ions) which have interacted in the solar atmosphere. A major problem of solar physics is to understand the relationship between these two groups of charged particles; in particular whether they are accelerated by the same mechanism. The paper reviews the physics of gamma-rays and neutron production in the solar atmosphere and the method by which properties of the primary charged particles produced in the solar flare can be deduced. Recent observations of energetic photons and neutrons in space and at the earth are used to present a current picture of the properties of impulsively flare accelerated electrons and ions. Some important properties discussed are time scale of production, composition, energy spectra, accelerator geometry. Particular attention is given to energetic particle production in the large flare on June 3, 1982.

  17. Application of the MST clustering to the high energy γ-ray sky. I—New possible detection of high-energy γ-ray emission associated with BL Lac objects

    NASA Astrophysics Data System (ADS)

    Campana, R.; Massaro, E.; Bernieri, E.; D'Amato, Q.

    2015-12-01

    In this paper we show an application of the Minimum Spanning Tree (MST) clustering method to the high-energy γ-ray sky observed at energies higher than 10 GeV in 6.3 years by the Fermi-Large Area Telescope. We report the detection of 19 new high-energy γ-ray clusters with good selection parameters whose centroid coordinates were found matching the positions of known BL Lac objects in the 5th Edition of the Roma-BZCAT catalogue. A brief summary of the properties of these sources is presented.

  18. Dissociation mechanisms of the Ar trimer induced by a third atom in high-energy electron-impact ionization

    NASA Astrophysics Data System (ADS)

    Yan, S.; Zhang, P.; Ma, X.; Xu, S.; Tian, S. X.; Li, B.; Zhu, X. L.; Feng, W. T.; Zhao, D. M.

    2014-06-01

    We experimentally studied the dissociation dynamics of a highly charged Ar3 cluster initiated by a high-energy electron. The dissociation patterns of the correlated ions from a two-body and a three-body Coulombic explosion (CE) of (Ar3)2+ suggest that predissociation alters the evolution of radiative charge transfer. The three-body CE in (Ar3)4+ and (Ar3)5+ is driven, after double ionization of one constituent Ar atom, by single ionization with a simultaneous interatomic Coulombic decay process.

  19. High-Energy Gamma-Ray Emission From Solar Flares: Summary of Fermi LAT Detections and Analysis of Two M-Class Flares

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Albert, A.; Allafort, A.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Brandt, T. J.; Guiriec, S.; Hays, E.; McEnery, J. E.; Nemmen, R.; Perkins, J. S.; Thompson, D. J.

    2013-01-01

    We present the detections of 19 solar flares detected in high-energy gamma rays (above 100 MeV) with the Fermi Large Area Telescope (LAT) during its rst four years of operation. Interestingly, all ares are associated with fairly fast Coronal Mass Ejections (CMEs) and are not all powerful X-ray ares. We then describe the detailed temporal, spatial and spectral characteristics of the rst two long-lasting events: the 2011 March 7 are, a moderate (M3.7) impulsive are followed by slowly varying gamma-ray emission over 13 hours, and the 2011 June 7 M2.5 are, which was followed by gamma-ray emission lasting for 2 hours. We compare the Fermi-LAT data with X-ray and proton data measurements from GOES and RHESSI. We argue that a hadronic origin of the gamma rays is more likely than a leptonic origin and nd that the energy spectrum of the proton distribution softens after the 2011 March 7 are, favoring a scenario with continuous acceleration at the are site. This work suggests that proton acceleration in solar ares is more common than previously thought, occurring for even modest X-ray ares, and for longer durations.

  20. Detection of Very High Energy γ-ray Emission from the Perseus Cluster Head-Tail Galaxy IC 310 by the MAGIC Telescopes

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Antonelli, L. A.; Antoranz, P.; Backes, M.; Barrio, J. A.; Bastieri, D.; Becerra González, J.; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, G.; Bordas, P.; Borla Tridon, D.; Bosch-Ramon, V.; Bose, D.; Braun, I.; Bretz, T.; Camara, M.; Cañellas, A.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Cossio, L.; Covino, S.; Dazzi, F.; De Angelis, A.; De Cea del Pozo, E.; De Lotto, B.; De Maria, M.; De Sabata, F.; Delgado Mendez, C.; Diago Ortega, A.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Errando, M.; Ferenc, D.; Fonseca, M. V.; Font, L.; García López, R. J.; Garczarczyk, M.; Giavitto, G.; Godinović, N.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Jogler, T.; Klepser, S.; Krähenbühl, T.; Kranich, D.; Krause, J.; La Barbera, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Lorenz, E.; Majumdar, P.; Makariev, M.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moralejo, A.; Nieto, D.; Nilsson, K.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Partini, S.; Pasanen, M.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, L.; Pochon, J.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puchades, N.; Puljak, I.; Reichardt, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Sánchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sierpowska-Bartosik, A.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Steinke, B.; Storz, J.; Strah, N.; Struebig, J. C.; Suric, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D. F.; Vankov, H.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.; Neronov, A.; Pfrommer, C.; Pinzke, A.; Semikoz, D. V.; MAGIC Collaboration

    2010-11-01

    We report on the detection with the MAGIC telescopes of very high energy (VHE) γ-rays from IC 310, a head-tail radio galaxy in the Perseus galaxy cluster, observed during the interval 2008 November to 2010 February. The Fermi satellite has also detected this galaxy. The source is detected by MAGIC at a high statistical significance of 7.6σ in 20.6 hr of stereo data. The observed spectral energy distribution is flat with a differential spectral index of -2.00 ± 0.14. The mean flux above 300 GeV, between 2009 October and 2010 February, (3.1 ± 0.5) × 10-12 cm-2 s-1, corresponds to (2.5 ± 0.4)% of Crab Nebula units. Only an upper limit, of 1.9% of Crab Nebula units above 300 GeV, was obtained with the 2008 data. This, together with strong hints (>3σ) of flares in the middle of 2009 October and November, implies that the emission is variable. The MAGIC results favor a scenario with the VHE emission originating from the inner jet close to the central engine. More complicated models than a simple one-zone synchrotron self-Compton (SSC) scenario, e.g., multi-zone SSC, external Compton, or hadronic, may be required to explain the very flat spectrum and its extension over more than three orders of magnitude in energy.

  1. DETECTION OF VERY HIGH ENERGY {gamma}-RAY EMISSION FROM THE PERSEUS CLUSTER HEAD-TAIL GALAXY IC 310 BY THE MAGIC TELESCOPES

    SciTech Connect

    Aleksic, J.; Blanch, O.; Antonelli, L. A.; Bonnoli, G.; Antoranz, P.; Backes, M.; Barrio, J. A.; Bose, D.; Bastieri, D.; Becerra Gonzalez, J.; Berger, K.; Bednarek, W.; Berdyugin, A.; Bernardini, E.; Biland, A.; Boller, A.; Bock, R. K.; Borla Tridon, D.; Bordas, P.; Bosch-Ramon, V. E-mail: fabio@iaa.e

    2010-11-10

    We report on the detection with the MAGIC telescopes of very high energy (VHE) {gamma}-rays from IC 310, a head-tail radio galaxy in the Perseus galaxy cluster, observed during the interval 2008 November to 2010 February. The Fermi satellite has also detected this galaxy. The source is detected by MAGIC at a high statistical significance of 7.6{sigma} in 20.6 hr of stereo data. The observed spectral energy distribution is flat with a differential spectral index of -2.00 {+-} 0.14. The mean flux above 300 GeV, between 2009 October and 2010 February, (3.1 {+-} 0.5) x 10{sup -12} cm{sup -2} s{sup -1}, corresponds to (2.5 {+-} 0.4)% of Crab Nebula units. Only an upper limit, of 1.9% of Crab Nebula units above 300 GeV, was obtained with the 2008 data. This, together with strong hints (>3{sigma}) of flares in the middle of 2009 October and November, implies that the emission is variable. The MAGIC results favor a scenario with the VHE emission originating from the inner jet close to the central engine. More complicated models than a simple one-zone synchrotron self-Compton (SSC) scenario, e.g., multi-zone SSC, external Compton, or hadronic, may be required to explain the very flat spectrum and its extension over more than three orders of magnitude in energy.

  2. Time evolution of high-energy emissions of low-mass stars. I. Age determination using stellar chronology with white dwarfs in wide binaries

    NASA Astrophysics Data System (ADS)

    Garcés, A.; Catalán, S.; Ribas, I.

    2011-07-01

    Context. Stellar ages are extremely difficult to determine and often subject to large uncertainties, especially for field low-mass stars. We plan to carry out a calibration of the decrease in high-energy emissions of low-mass GKM stars with time, and therefore precise age determination is a key ingredient. The overall goal of our research is to study the time evolution of these high-energy emissions as an essential input to studying exoplanetary atmospheres. Aims: We propose to determine stellar ages with a methodology based on wide binaries. We are interested in systems composed of a low-mass star and a white dwarf (WD), where the latter serves as a stellar chronometer for the system. We aim at obtaining reliable ages for a sample of late-type stars older than 1 Gyr. Methods: We selected a sample of wide binaries composed by a DA type WD and a GKM companion. High signal-to-noise, low-resolution spectroscopic observations were obtained for most of the WD members of the sample. Atmospheric parameters were determined by fitting the spectroscopic data to appropiate WD models. The total ages of the systems were derived by using cooling sequences, an initial-final mass relationship and evolutionary tracks, to account for the progenitor life. Results: The spectroscopic observations have allowed us to determine ages for the binary systems using WDs as cosmochronometers. We obtained reliable ages for 27 stars between 1 and 5 Gyr, which is a range where age determination becomes difficult for field objects. Roughly half of these systems have cooling ages that contribute at least 30% the total age. We select those for further study since their age estimate should be less prone to systematic errors coming from the initial-final mass relationship. Conclusions: We have determined robust ages for a sizeable sample of GKM stars that can be subsequently used to study the time evolution of their emissions associated to stellar magnetic activity. Based on observations collected at

  3. Search for Hard X-Ray Emission from Aquila X-1: High Energy Emission from Gamma-ray Radio Star 2CG 135+1/LSI 61 305

    NASA Technical Reports Server (NTRS)

    Tavani, Marco

    1998-01-01

    Several investigations supported by these CCRO grant were completed or are close to completion. The study of EGRET data for the unidentified source 2CG 135+01 was very fruitful. We discovered transient gamma-ray emission by combining several data obtained since 1994 through 1997. It is the first time that time variable emission is established for this enigmatic source, and clearly an interpretation in terms of an isolated radio pulsar (Geminga-like) is disfavored now. Our preferred model is a Galactic source, probably an energetic pulsar (such as PSR129-63) in a binary system producing gamma-rays because of pulsar wind/mass outflow interaction. We also accumulated may data concerning the radio source LSI 61 303, the possible counterpart of 2CG 135+01. We show that a possible anti-correlation between radio and gamma-ray emission exists. This anticorrelation is evident only in the energy range above 100 MeV, as demonstrated by the lack of it obtained from OSSE data. If confirmed, this anti-correlation would prove to be very important for the interpretation of the hundreds of unidentified gamma-ray sources currently discovered by EGRET near the Galactic plane, and would point to a new class of sources in addition to AGNs and isolated pulsars. We also completed the analysis of several time variable gamma-ray sources near the Galactic plane, with the discussion of evidence for transient emission from 2EG J1813-12 and 2EG J1828+01. We completed several investigations regarding gamma-ray bursts (GRBs), including the study of the brightness distribution for different spectral/duration GRB sub-classes, an investigation of acceleration processes and their consequences for GRB afterglow emission [61, the application of the synchrotron shock model of GRBs to X-ray energies.

  4. From QCD-based hard-scattering to nonextensive statistical mechanical descriptions of transverse momentum spectra in high-energy p p and p p ¯ collisions

    NASA Astrophysics Data System (ADS)

    Wong, Cheuk-Yin; Wilk, Grzegorz; Cirto, Leonardo J. L.; Tsallis, Constantino

    2015-06-01

    Transverse spectra of both jets and hadrons obtained in high-energy p p and p p ¯ collisions at central rapidity exhibit power-law behavior of 1 /pTn at high pT . The power index n is 4-5 for jet production and is 6-10 for hadron production. Furthermore, the hadron spectra spanning over 14 orders of magnitude down to the lowest pT region in p p collisions at the LHC can be adequately described by a single nonextensive statistical mechanical distribution that is widely used in other branches of science. This suggests indirectly the possible dominance of the hard-scattering process over essentially the whole pT region at central rapidity in high-energy p p and p p ¯ collisions. We show here direct evidences of such a dominance of the hard-scattering process by investigating the power indices of UA1 and ATLAS jet spectra over an extended pT region and the two-particle correlation data of the STAR and PHENIX collaborations in high-energy p p and p p ¯ collisions at central rapidity. We then study how the showering of the hard-scattering product partons alters the power index of the hadron spectra and leads to a hadron distribution that may be cast into a single-particle nonextensive statistical mechanical distribution. Because of such a connection, the nonextensive statistical mechanical distribution may be considered as a lowest-order approximation of the hard-scattering of partons followed by the subsequent process of parton showering that turns the jets into hadrons, in high-energy p p and p p ¯ collisions.

  5. Discovery of very high energy γ-ray emission from the blazar 1ES 0033+595 by the MAGIC telescopes

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Carreto Fidalgo, D.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Caneva, G.; de Lotto, B.; Delgado Mendez, C.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Farina, E.; Ferenc, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Hayashida, M.; Herrera, J.; Herrero, A.; Hildebrand, D.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nilsson, K.; Nishijima, K.; Noda, K.; Nowak, N.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Partini, S.; Persic, M.; Prada, F.; Moroni, P. G. Prada; Prandini, E.; Preziuso, S.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Rügamer, S.; Saggion, A.; Saito, T.; Saito, K.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Stamatescu, V.; Stamerra, A.; Steinbring, T.; Storz, J.; Sun, S.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Tronconi, V.; Buson, S.; Borghese, A.

    2015-01-01

    The number of known very high energy (VHE) blazars is ˜50, which is very small in comparison to the number of blazars detected in other frequencies. This situation is a handicap for population studies of blazars, which emit about half of their luminosity in the γ-ray domain. Moreover, VHE blazars, if distant, allow for the study of the environment that the high-energy γ-rays traverse in their path towards the Earth, like the extragalactic background light (EBL) and the intergalactic magnetic field (IGMF), and hence they have a special interest for the astrophysics community. We present the first VHE detection of 1ES 0033+595 with a statistical significance of 5.5σ. The VHE emission of this object is constant throughout the MAGIC observations (2009 August and October), and can be parametrized with a power law with an integral flux above 150 GeV of (7.1 ± 1.3) × 10-12 photons cm-2 s-1 and a photon index of (3.8 ± 0.7). We model its spectral energy distribution (SED) as the result of inverse Compton scattering of synchrotron photons. For the study of the SED, we used simultaneous optical R-band data from the KVA telescope, archival X-ray data by Swift as well as INTEGRAL, and simultaneous high-energy (HE, 300 MeV-10 GeV) γ-ray data from the Fermi Large Area Telescope (LAT) observatory. Using the empirical approach of Prandini et al. (2010) and the Fermi LAT and MAGIC spectra for this object, we estimate the redshift of this source to be 0.34 ± 0.08 ± 0.05. This is a relevant result because this source is possibly one of the 10 most distant VHE blazars known to date, and with further (simultaneous) observations could play an important role in blazar population studies, as well as future constraints on the EBL and IGMF.

  6. Equal-Channel Angular Extrusion of a Low-Density High-Entropy Alloy Produced by High-Energy Cryogenic Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Hammond, Vincent H.; Atwater, Mark A.; Darling, Kristopher A.; Nguyen, Hoang Q.; Kecskes, Laszlo J.

    2014-10-01

    In this study, we demonstrate the feasibility of forming a bulk consolidated, low-density high-entropy alloy, namely AlFeMgTiZn, which shows reasonable mechanical properties and high hardness. The fabrication of the high-entropy alloy from powdered precursors via high-energy mechanical alloying as a function of milling time is presented. In turn, the evolution of the alloy microstructure with postmilling anneal treatment is elucidated. Last, the severe plastic deformation processing methodology, i.e., equal-channel angular extrusion, chosen for consolidation, is described and shown to result in a bulk product with good results.

  7. New Prospects in High Energy Astrophysics

    SciTech Connect

    Blandford, Roger; /KIPAC, Menlo Park

    2011-11-15

    Recent discoveries using TeV, X-ray and radio telescopes as well as Ultra High Energy Cosmic Ray arrays are leading to new insights into longstanding puzzles in high energy astrophysics. Many of these insights come from combining observations throughout the electromagnetic and other spectra as well as evidence assembled from different types of source to propose general principles. Issues discussed in this general overview include methods of accelerating relativistic particles, and amplifying magnetic field, the dynamics of relativistic outflows and the nature of the prime movers that power them. Observational approaches to distinguishing hadronic, leptonic and electromagnetic outflows and emission mechanisms are discussed along with probes of the velocity field and the confinement mechanisms. Observations with GLAST promise to be very prescriptive for addressing these problems.

  8. High-energy electron irradiation of annual plants (bagasse) for an efficient production of chemi-mechanical pulp fibers

    NASA Astrophysics Data System (ADS)

    Pathak, Shailesh; Ray, A. K.; Großmann, Harald; Kleinert, Rene

    2015-12-01

    The paper industry is one of the largest consumers of energy and energy consumption has been increased several times in last few decades. Bagasse chemical pulping has very low yield about 45-55% and also generates high pollution load in the effluent as compared to mechanical pulping, g. Thermo-mechanical pulp (TMP). On the other hand,-->e.g. thermo-mechanical pulp (TMP). On the other hand, the specific energy consumption is very high for TMP pulps. ETMP (Energy efficient Thermo-Mechanical Pulping) or ECTMP (Energy efficient Chemi-Thermo Mechanical Pulping) is an innovative idea for reducing the energy demand in TMP refining. In the present investigation, energy efficient mechanical pulping potential of bagasse was studied using TMP, CTMP and ECTMP pulping methodology with electron irradiation pretreatment. It is evident from the results that more than 50% energy saving potential of irradiation pre-treatment was achieved.

  9. Effect of High Energy Radiation on Mechanical Properties of Graphite Fiber Reinforced Composites. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Naranong, N.

    1980-01-01

    The flexural strength and average modulus of graphite fiber reinforced composites were tested before and after exposure to 0.5 Mev electron radiation and 1.33 Mev gamma radiation by using a three point bending test (ASTM D-790). The irradiation was conducted on vacuum treated samples. Graphite fiber/epoxy (T300/5208), graphite fiber/polyimide (C6000/PMR 15) and graphite fiber/polysulfone (C6000/P1700) composites after being irradiated with 0.5 Mev electron radiation in vacuum up to 5000 Mrad, show increases in stress and modulus of approximately 12% compared with the controls. Graphite fiber/epoxy (T300/5208 and AS/3501-6), after being irradiated with 1.33 Mev gamma radiation up to 360 Mrads, show increases in stress and modulus of approximately 6% at 167 Mrad compared with the controls. Results suggest that the graphite fiber composites studied should withstand the high energy radiation in a space environment for a considerable time, e.g., over 30 years.

  10. Observation of intrinsic emission in β-BiNbO4 available for excitation of both UV light and high energy irradiation.

    PubMed

    Yu, Ruijin; Fan, Aiping; Yuan, Maosen; Li, Tianbao; Wang, Jinyi

    2016-09-14

    β-BiNbO4 with a high temperature triclinic form was prepared via a high-temperature solid-state reaction ceramic method. Structural refinement and surface characteristic studies were performed. The optical absorption, and electronic calculation of the band structures and density of states were also studied. β-BiNbO4 ceramic has an indirect transition with a band energy of 3.05 eV. The valence band is dominated by O-2p states whereas the conduction band has predominantly Nb 4d and Bi 6s character. The intrinsic luminescence properties of β-BiNbO4 were reported, and present a blue emission band peak at 435 nm under the excitation of UV light. The β-BiNbO4 ceramic presents scintillation properties under high energy irradiation. The luminescence was studied via the combinations of the color centers, band calculation and energy transfer from NbO6 to Bi(3+) in the lattices. The thermal quenching and activation energy for the luminescence were reported. β-BiNbO4 has potential applications in photoluminescence and scintillation materials. PMID:27511288

  11. The γ-ray emission mechanism for Fermi Blazars

    NASA Astrophysics Data System (ADS)

    Yang, J. H.; Fan, J. H.; Hua, T. X.; Wu, D. X.

    2014-08-01

    Fermi Blazars are characterized mainly by the vast effect that relativistic beaming has on their emission spectra. Fermi-LAT has detected more than 1000 blazars which provide us with a good opportunity to study the emission mechanism. In this paper, adopted the Doppler factor δ γ determined in our previous paper, the γ-ray emission mechanism is discussed using the investigation of dependence of the γ-ray luminosity on the Doppler factor. Our discussions suggest that the γ-ray emission mechanism is SSC for BL Lacs.

  12. High-energy resolution X-ray absorption and emission spectroscopy reveals insight into unique selectivity of La-based nanoparticles for CO2

    PubMed Central

    Hirsch, Ofer; Kvashnina, Kristina O.; Luo, Li; Süess, Martin J.; Glatzel, Pieter; Koziej, Dorota

    2015-01-01

    The lanthanum-based materials, due to their layered structure and f-electron configuration, are relevant for electrochemical application. Particularly, La2O2CO3 shows a prominent chemoresistive response to CO2. However, surprisingly less is known about its atomic and electronic structure and electrochemically significant sites and therefore, its structure–functions relationships have yet to be established. Here we determine the position of the different constituents within the unit cell of monoclinic La2O2CO3 and use this information to interpret in situ high-energy resolution fluorescence-detected (HERFD) X-ray absorption near-edge structure (XANES) and valence-to-core X-ray emission spectroscopy (vtc XES). Compared with La(OH)3 or previously known hexagonal La2O2CO3 structures, La in the monoclinic unit cell has a much lower number of neighboring oxygen atoms, which is manifested in the whiteline broadening in XANES spectra. Such a superior sensitivity to subtle changes is given by HERFD method, which is essential for in situ studying of the interaction with CO2. Here, we study La2O2CO3-based sensors in real operando conditions at 250 °C in the presence of oxygen and water vapors. We identify that the distribution of unoccupied La d-states and occupied O p- and La d-states changes during CO2 chemoresistive sensing of La2O2CO3. The correlation between these spectroscopic findings with electrical resistance measurements leads to a more comprehensive understanding of the selective adsorption at La site and may enable the design of new materials for CO2 electrochemical applications. PMID:26668362

  13. Study of Mechanical Properties of Bone by Measuring Load Transfer via High-energy X-ray Diffraction

    NASA Astrophysics Data System (ADS)

    Singhal, Anjali

    Synchrotron high-energy X-ray scattering is used to investigate the in situ strains in hydroxyapatite (HAP) platelets and mineralized collagen fibrils in bovine cortical bone. Compressive load-unload tests at room temperature (27°C) and body temperature (37°C) show that the load transfer to the stiff nano-sized platelets from the surrounding compliant protein matrix does not vary significantly with temperature. This emphasizes that the stiffness of bone is controlled by the stiffness of the HAP phase, which remains unaffected by this change in temperature. Monotonic loading tests in compression and tension, conducted at 37°C, illustrate the spatial variation of properties within a single femur, which is correlated to the mineral content, porosity and microstructure of the samples. The average apparent modulus of HAP and fibrils (EappHAP and Eappfib, respectively), defined as the ratio of applied stress and phase strain, is obtained as 27.5 ± 6.6 and 18.5 ± 8.9 GPa, respectively, in compression. These values are significantly higher than the values of 20.0 ± 5.4 and 4.1 ± 2.6 GPa obtained for HAP and fibrils, respectively, in tension. The difference between the two types of loading is attributed to greater plastic deformation of collagen in tension, which results in greater strains in the collagen fibril, and concomitant greater load transfer to the HAP. Increasing synchrotron X-ray doses (5-3880 kGy) affect neither apparent HAP nor fibrillar modulus, up to stresses of -60 MPa (measured during in situ loading and unloading). However, the residual elastic strains in the HAP phase decrease markedly with increased irradiation, indicating damage at the HAP-collagen interface. Analysis of the X-ray diffraction peak widths shows that unit cells of HAP which are under the highest initial residual strains are most able to relax due to irradiation, resulting in a net decrease in the strain

  14. Testing of the coalescence mechanism in high energy heavy ion collisions using two-particle correlations with identified particle trigger

    NASA Astrophysics Data System (ADS)

    Choudhury, Subikash; Sarkar, Debojit; Chattopadhyay, Subhasis

    2016-05-01

    In central Au-Au collisions at top RHIC energy, two-particle correlation measurements with identified hadron trigger have shown attenuation of near-side proton triggered jetlike yield at intermediate transverse momentum (p T ),2

    mechanism of hadronization. Baryon enhancement was also observed at LHC in the single inclusive spectra. We study the consequence of such an enhancement on two-particle correlations at LHC energy within the framework of a multiphase transport (AMPT) model that implements quark coalescence as a mode of hadronization. In this paper we have calculated the proton over pion ratio and the near side per trigger yield associated with pion and proton triggers at intermediate p T from the string melting (SM) version of AMPT. Results obtained are contrasted with the AMPT default (Def.) which does not include coalescence. Baryon enhancement was observed in AMPT SM at intermediate p T . Near-side jetlike correlated yield associated with baryon (proton) trigger in the momentum region where baryon generation is enhanced is found to be suppressed as compared to the corresponding yields for the meson (pion) trigger in most central Pb-Pb events. No such effect was found in the default version of AMPT.

  15. From QCD-based hard-scattering to nonextensive statistical mechanical descriptions of transverse momentum spectra in high-energy $pp$ and $$p\\bar p$$ collisions

    DOE PAGESBeta

    Wong, Cheuk-Yin; Wilk, Grzegorz; Cirto, Leonardo J. L.; Tsallis, Constantino

    2015-01-01

    Transverse spectra of both jets and hadrons obtained in high-energymore » $pp$ and $$p\\bar p $$ collisions at central rapidity exhibit power-law behavior of $1/p_T^n$ at high $p_T$. The power index $n$ is 4-5 for jet production and is slightly greater for hadron production. Furthermore, the hadron spectra spanning over 14 orders of magnitude down to the lowest $p_T$ region in $pp$ collisions at LHC can be adequately described by a single nonextensive statistical mechanical distribution that is widely used in other branches of science. This suggests indirectly the dominance of the hard-scattering process over essentially the whole $p_T$ region at central rapidity in $pp$ collisions at LHC. We show here direct evidences of such a dominance of the hard-scattering process by investigating the power index of UA1 jet spectra over an extended $p_T$ region and the two-particle correlation data of the STAR and PHENIX Collaborations in high-energy $pp$ and $$p \\bar p$$ collisions at central rapidity. We then study how the showering of the hard-scattering product partons alters the power index of the hadron spectra and leads to a hadron distribution that can be cast into a single-particle non-extensive statistical mechanical distribution. Because of such a connection, the non-extensive statistical mechanical distribution can be considered as a lowest-order approximation of the hard-scattering of partons followed by the subsequent process of parton showering that turns the jets into hadrons, in high energy $pp$ and $$p\\bar p$$ collisions.« less

  16. From QCD-based hard-scattering to nonextensive statistical mechanical descriptions of transverse momentum spectra in high-energy pp and pp¯ collisions

    DOE PAGESBeta

    Wong, Cheuk-Yin; Wilk, Grzegorz; Cirto, Leonardo J. L.; Tsallis, Constantino

    2015-06-22

    Transverse spectra of both jets and hadrons obtained in high-energymore » $pp$ and $$p\\bar p $$ collisions at central rapidity exhibit power-law behavior of $1/p_T^n$ at high $p_T$. The power index $n$ is 4-5 for jet production and is slightly greater for hadron production. Furthermore, the hadron spectra spanning over 14 orders of magnitude down to the lowest $p_T$ region in $pp$ collisions at LHC can be adequately described by a single nonextensive statistical mechanical distribution that is widely used in other branches of science. This suggests indirectly the dominance of the hard-scattering process over essentially the whole $p_T$ region at central rapidity in $pp$ collisions at LHC. We show here direct evidences of such a dominance of the hard-scattering process by investigating the power index of UA1 jet spectra over an extended $p_T$ region and the two-particle correlation data of the STAR and PHENIX Collaborations in high-energy $pp$ and $$p \\bar p$$ collisions at central rapidity. We then study how the showering of the hard-scattering product partons alters the power index of the hadron spectra and leads to a hadron distribution that can be cast into a single-particle non-extensive statistical mechanical distribution. Lastly, because of such a connection, the non-extensive statistical mechanical distribution can be considered as a lowest-order approximation of the hard-scattering of partons followed by the subsequent process of parton showering that turns the jets into hadrons, in high energy $pp$ and $$p\\bar p$$ collisions.« less

  17. Formation of a nanodispersed metal-matrix structure during a combined high-energy mechanical alloying of powders of aluminum-based SiC-containing alloys

    NASA Astrophysics Data System (ADS)

    Popov, V. A.; Cherdyntsev, V. V.

    2009-01-01

    Phase and structural state of composite materials produced by combined mechanical alloying of the AK12M2 and D16 powder alloys with silicon carbide in high-energy planetary mills with the use of ball charging and quasi-cylindrical bodies have been studied. It has been found out that the type of bodies substantially affects the mutual solubility of components in the systems investigated, as well as the perfection of the crystal lattice of the material treated, and its adhesion to the bodies and to the inner surface of the drum. It is shown that the use of balls favors an enhanced mutual solubility of the components and stipulates higher deformation of the crystal lattice of the product in comparison with the quasi-cylinder grinding bodies. The differences observed are discussed based on the calculated data obtained earlier for the ratio of normal and tangential components of energy consumption for different types of grinding bodies.

  18. Mechanism of directional emission from a peanut-shaped microcavity

    SciTech Connect

    Shu Fangjie; Zou Changling; Sun Fangwen; Xiao Yunfeng

    2011-05-15

    Collimated directional emission is essentially required for an asymmetric resonant cavity. In this paper, we theoretically investigate a type of peanut-shaped microcavity which can support highly directional emission with a beam divergence as small as 2.5 deg. The mechanism of the collimated emission of this type of peanut-shaped microcavity is explained with a short-term ray trajectory. Moreover, the explanations are also confirmed by a numerical wave simulation. This extremely narrow divergence of the emission holds great potential in highly collimated lasing from on-chip microcavities.

  19. DISENTANGLING HADRONIC AND LEPTONIC CASCADE SCENARIOS FROM THE VERY-HIGH-ENERGY GAMMA-RAY EMISSION OF DISTANT HARD-SPECTRUM BLAZARS

    SciTech Connect

    Takami, Hajime; Murase, Kohta; Dermer, Charles D. E-mail: murase@ias.edu

    2013-07-10

    Recent data from the Fermi Large Area Telescope have revealed about a dozen distant hard-spectrum blazars that have very-high-energy (VHE; {approx}> 100 GeV) photons associated with them, but most of them have not yet been detected by imaging atmospheric Cherenkov Telescopes. Most of these high-energy gamma-ray spectra, like those of other extreme high-frequency peaked BL Lac objects, can be well explained either by gamma rays emitted at the source or by cascades induced by ultra-high-energy cosmic rays, as we show specifically for KUV 00311-1938. We consider the prospects for detection of the VHE sources by the planned Cherenkov Telescope Array (CTA) and show how it can distinguish the two scenarios by measuring the integrated flux above {approx}500 GeV (depending on source redshift) for several luminous sources with z {approx}< 1 in the sample. Strong evidence for the origin of ultra-high-energy cosmic rays could be obtained from VHE observations with CTA. Depending on redshift, if the often quoted redshift of KUV 00311-1938 (z = 0.61) is believed, then preliminary H.E.S.S. data favor cascades induced by ultra-high-energy cosmic rays. Accurate redshift measurements of hard-spectrum blazars are essential for this study.

  20. CONSTRAINTS ON THE SYNCHROTRON EMISSION MECHANISM IN GAMMA-RAY BURSTS

    SciTech Connect

    Beniamini, Paz; Piran, Tsvi E-mail: tsvi.piran@mail.huji.ac.il

    2013-05-20

    We reexamine the general synchrotron model for gamma-ray bursts' (GRBs') prompt emission and determine the regime in the parameter phase space in which it is viable. We characterize a typical GRB pulse in terms of its peak energy, peak flux, and duration and use the latest Fermi observations to constrain the high-energy part of the spectrum. We solve for the intrinsic parameters at the emission region and find the possible parameter phase space for synchrotron emission. Our approach is general and it does not depend on a specific energy dissipation mechanism. Reasonable synchrotron solutions are found with energy ratios of 10{sup -4} < {epsilon}{sub B}/{epsilon}{sub e} < 10, bulk Lorentz factor values of 300 < {Gamma} < 3000, typical electrons' Lorentz factor values of 3 Multiplication-Sign 10{sup 3} < {gamma}{sub e} < 10{sup 5}, and emission radii of the order 10{sup 15} cm < R < 10{sup 17} cm. Most remarkable among those are the rather large values of the emission radius and the electron's Lorentz factor. We find that soft (with peak energy less than 100 keV) but luminous (isotropic luminosity of 1.5 Multiplication-Sign 10{sup 53}) pulses are inefficient. This may explain the lack of strong soft bursts. In cases when most of the energy is carried out by the kinetic energy of the flow, such as in the internal shocks, the synchrotron solution requires that only a small fraction of the electrons are accelerated to relativistic velocities by the shocks. We show that future observations of very high energy photons from GRBs by CTA could possibly determine all parameters of the synchrotron model or rule it out altogether.

  1. Volatile Emission of Mechanically Damaged Almonds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mature almonds from the Monterey variety were evaluated for their volatile composition after mechanical damage and compared to the volatile composition of the corresponding undamaged almonds. Volatiles were collected on Tenax, desorbed with diethyl ether, and identified via GC-MS analyses. Volatile ...

  2. AN EMISSION MECHANISM EXPLAINING OFF-PULSE EMISSION ORIGINATING IN THE OUTER MAGNETOSPHERE OF PULSARS

    SciTech Connect

    Basu, Rahul; Mitra, Dipanjan; Melikidze, George I. E-mail: dmitra@ncra.tifr.res.in

    2013-08-01

    We have examined the cyclotron resonance instability developing in the relativistic outflowing plasma in the pulsar magnetosphere. The instability condition leads to radio emission in the subgigahertz frequency regime which is likely to be seen as off-pulse emission. Recent studies have shown the presence of off-pulse emission in long period pulsars, and we demonstrate this plasma process to be an energetically viable mechanism.

  3. ACCELERATING HIGH-ENERGY PULSAR RADIATION CODES

    SciTech Connect

    Venter, C.; De Jager, O. C.

    2010-12-20

    Curvature radiation (CR) is believed to be a dominant mechanism for creating gamma-ray emission from pulsars and is emitted by relativistic particles that are constrained to move along curved magnetic field lines. Additionally, synchrotron radiation (SR) is expected to be radiated by both relativistic primaries (involving cyclotron resonant absorption of radio photons and re-emission of SR photons), or secondary electron-positron pairs (created by magnetic or photon-photon pair production processes involving CR gamma rays in the pulsar magnetosphere). When calculating these high-energy spectra, especially in the context of pulsar population studies where several millions of CR and SR spectra have to be generated, it is profitable to consider approximations that would save computational time without sacrificing too much accuracy. This paper focuses on one such approximation technique, and we show that one may gain significantly in computational speed while preserving the accuracy of the spectral results.

  4. High Energy Polarization of Blazars: Detection Prospects

    NASA Astrophysics Data System (ADS)

    Chakraborty, N.; Pavlidou, V.; Fields, B. D.

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

  5. HIGH ENERGY POLARIZATION OF BLAZARS: DETECTION PROSPECTS

    SciTech Connect

    Chakraborty, N.; Pavlidou, V.; Fields, B. D.

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

  6. Mechanical properties of pulsed laser-deposited hydroxyapatite thin film implanted at high energy with N + and Ar + ions. Part I: nanoindentation with spherical tipped indenter

    NASA Astrophysics Data System (ADS)

    Pelletier, H.; Nelea, V.; Mille, P.; Muller, D.

    2004-02-01

    We report here a comparison between the effects of ion beam implantation treatment using nitrogen and argon ions, on the mechanical characteristics of HA films grown by pulsed laser deposition, using a KrF ∗ excimer laser. Crystalline and stoichiometric HA films were grown on Ti-5Al-2.5Fe alloy substrate, previously coated with a TiN buffer layer. After deposition, the film were implanted with ions of N + and Ar + of high energy (1-1.5 MeV range) and dose set at 10 16 at cm -2. From the load-displacement curves determined by nanoindentation tests using a spherical tipped nanoindenter ( R=5 μm), we put into evidence an enhancement of the mechanical characteristics (hardness and elastic modulus) of the HA films after implantation, especially for those implanted with N + ions. Moreover, using various applied normal loads (ranging from 1 to 100 mN) in different implanted areas, a good reproducibility of nitrogen implantation effect are observed.

  7. Multiwavelength Observations of AGN Jets: Untangling the Coupled Problems of Emission Mechanism and Jet Structure

    NASA Astrophysics Data System (ADS)

    Perlman, Eric S.; Avachat, Sayali S.; Clautice, Devon; Georganopoulos, Markos; Meyer, Eileen; Cara, Mihai

    2016-04-01

    The discovery of X-ray and optical emission from large numbers of AGN jets is one of the key legacies of the Chandra X-ray Observatory and Hubble Space Telescope. Several dozen optical and X-ray emitting jets are now known, most of which are seen in both bands as well as in the radio, where they were first discovered. Jets carry prodigious amounts of energy and mass out from the nuclear regions out to tens to hundreds of kiloparsecs distant from the central black hole, depositing it into the host galaxy and cluster. Interpreting their multiwavelength emissions has not been easy: while in most jets, the optical and radio emission in many objects is believed to emerge via the synchrotron process, due to its characteristic spectral shape and high radio polarization, the X-ray emission has been a tougher nut to crack. In less powerful, FR I jets, such as M87, the X-ray emission is believed to be synchrotron emission from the highest energy electrons, requiring in situ particle acceleration due to the short radiative lifetimes of the particles. However, in FR II and quasar jets, a variety of emission mechanisms are possible. Until the last few years, the leading interpretation had been inverse-Comptonization of Cosmic Microwave Background photons (the IC/CMB mechanism). This requires the jet to be relativistic out to hundreds of kiloparsecs from the nucleus, and requires an electron spectrum that extends to very low Lorentz factors. However, that now appears less likely, due to observed high optical polarizations in jets where the optical and X-ray emission appears to lie on the same spectral component, as well as limits derived from Fermi observations in the GeV gamma-rays. It now appears more likely that the X-rays must arise as synchrotron emission from a second, high energy electron population. With this revelation, we must tackle anew the coupling between jet structure and emission mechanisms. Multiwavelength imaging and polarimetry can give us clues to the

  8. Acoustic emission spectral analysis of fiber composite failure mechanisms

    NASA Technical Reports Server (NTRS)

    Egan, D. M.; Williams, J. H., Jr.

    1978-01-01

    The acoustic emission of graphite fiber polyimide composite failure mechanisms was investigated with emphasis on frequency spectrum analysis. Although visual examination of spectral densities could not distinguish among fracture sources, a paired-sample t statistical analysis of mean normalized spectral densities did provide quantitative discrimination among acoustic emissions from 10 deg, 90 deg, and plus or minus 45 deg, plus or minus 45 deg sub s specimens. Comparable discrimination was not obtained for 0 deg specimens.

  9. High energy neutron radiography

    SciTech Connect

    Gavron, A.; Morley, K.; Morris, C.; Seestrom, S.; Ullmann, J.; Yates, G.; Zumbro, J.

    1996-06-01

    High-energy spallation neutron sources are now being considered in the US and elsewhere as a replacement for neutron beams produced by reactors. High-energy and high intensity neutron beams, produced by unmoderated spallation sources, open potential new vistas of neutron radiography. The authors discuss the basic advantages and disadvantages of high-energy neutron radiography, and consider some experimental results obtained at the Weapons Neutron Research (WNR) facility at Los Alamos.

  10. Black holes and high energy physics

    NASA Astrophysics Data System (ADS)

    Grib, A. A.; Pavlov, Yu. V.

    2016-01-01

    Three mechanisms of getting high energies in particle collisions in the ergosphere of the rotating black holes are considered. The consequences of these mechanisms for observation of ultra high energy cosmic rays particles on the Earth as result of conversion of superheavy dark matter particles into ordinary particles are discussed.

  11. Ammonia emissions from two mechanically ventilated UK livestock buildings

    NASA Astrophysics Data System (ADS)

    Demmers, T. G. M.; Burgess, L. R.; Short, J. L.; Phillips, V. R.; Clark, J. A.; Wathes, C. M.

    Ammonia emission rates from livestock buildings are required to construct an accurate emission inventory for the UK. Ventilation and ammonia emission rates from a fattening pig unit and a broiler house, both mechanically ventilated, were estimated using fan wheel anemometers and thermal converters with a chemiluminescence NO x-analyser to measure the ventilation rate and the ammonia concentration, respectively. The estimated ammonia emission factors were 46.9 and 16.6 kg lu -1 a -1 for the fattening pig unit and the broiler house, respectively. Both emission factors were within the range reported in the literature. A tracer gas (CO) method, based on a constant tracer release rate, was validated for measuring ventilation rates from naturally ventilated livestock buildings. Air inlets and outlets were identified using the air temperature or tracer concentration in the opening. Tracer concentration was found to be a more suitable criterion than temperature. In both houses, a significant correlation between the estimated ventilation rate using the tracer method and the measured ventilation rate using fan wheel anemometers was found. The ventilation rate was underestimated by 12 and 6% for the piggery and broiler house, respectively. The instantaneous ammonia emission derived from the tracer gas method was lower than the ammonia emission derived from the fan wheel anemometer method by 14 and 16% for the piggery and broiler house, respectively. The ventilation and ammonia emission estimates using the tracer method were within acceptable range from the ventilation and emission rates measured using measuring fans, but because of its accuracy and simplicity the fan wheel anemometer method is preferred for long-term measurements of ventilation rate in mechanically ventilated buildings.

  12. Green house gas emissions from composting and mechanical biological treatment.

    PubMed

    Amlinger, Florian; Peyr, Stefan; Cuhls, Carsten

    2008-02-01

    In order to carry out life-cycle assessments as a basis for far-reaching decisions about environmentally sustainable waste treatment, it is important that the input data be reliable and sound. A comparison of the potential greenhouse gas (GHG) emissions associated with each solid waste treatment option is essential. This paper addresses GHG emissions from controlled composting processes. Some important methodological prerequisites for proper measurement and data interpretation are described, and a common scale and dimension of emission data are proposed so that data from different studies can be compared. A range of emission factors associated with home composting, open windrow composting, encapsulated composting systems with waste air treatment and mechanical biological waste treatment (MBT) are presented from our own investigations as well as from the literature. The composition of source materials along with process management issues such as aeration, mechanical agitation, moisture control and temperature regime are the most important factors controlling methane (CH4), nitrous oxide (N2O) and ammoniac (NH3) emissions. If ammoniac is not stripped during the initial rotting phase or eliminated by acid scrubber systems, biofiltration of waste air provides only limited GHG mitigation, since additional N2O may be synthesized during the oxidation of NH3, and only a small amount of CH4 degradation occurs in the biofilter. It is estimated that composting contributes very little to national GHG inventories generating only 0.01-0.06% of global emissions. This analysis does not include emissions from preceding or post-treatment activities (such as collection, transport, energy consumption during processing and land spreading), so that for a full emissions account, emissions from these activities would need to be added to an analysis. PMID:18338701

  13. High energy flux thermo-mechanical test of 1D-carbon-carbon fibre composite prototypes for the SPIDER diagnostic calorimeter.

    PubMed

    De Muri, M; Cavallin, T; Pasqualotto, R; Dalla Palma, M; Cervaro, V; Fasolo, D; Franchin, L; Tollin, M; Greuner, H; Böswirth, B; Serianni, G

    2014-02-01

    Operation of the thermonuclear fusion experiment ITER requires additional heating via injection of neutral beams from accelerated negative ions. In the SPIDER test facility, under construction in Padova, the production of negative ions will be studied and optimised. STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) is a diagnostic used to characterise the SPIDER beam during short pulse operation (several seconds) to verify if the beam meets the ITER requirements about the maximum allowed beam non-uniformity (below ±10%). The major components of STRIKE are 16 1D-CFC (Carbon-Carbon Fibre Composite) tiles, observed at the rear side by a thermal camera. This contribution gives an overview of some tests under high energy particle flux, aimed at verifying the thermo-mechanical behaviour of several CFC prototype tiles. The tests were performed in the GLADIS facility at IPP (Max-Plank-Institut für Plasmaphysik), Garching. Dedicated linear and nonlinear simulations were carried out to interpret the experiments and a comparison of the experimental data with the simulation results is presented. The results of some morphological and structural studies on the material after exposure to the GLADIS beam are also given. PMID:24593452

  14. Nanocomposite bulk of mechanically milled Al-Pb samples consolidated pore-free by the high-energy rate forming technique.

    PubMed

    Csanády, Agnes; Sajó, István; Lábár, János L; Szalay, András; Papp, Katalin; Balaton, Géza; Kálmán, Erika

    2005-06-01

    It is shown that pore-free bulk samples were produced by the high-energy rate forming axis-symmetrical powder compaction method for different application purposes in case of the very different, immiscible Al and Pb metal pair. The starting Al-Pb nanocomposites were made by mechanical milling of atomized Al and Pb powders either in a SPEX 9000 or a Fritsch Pulverisette 4 mill. Due to the conditions that milling was carried out in air, the PbO layer, originally existing at the surface of the atomized Pb powder, ruptured and was also dispersed in the composite. The presence of the nano PbO particles was proven by XRD and TEM (BF, DF, SAED). When the energy of milling was high, the PbO crystallites became so small that they could hardly be seen by XRD technique. Local distribution of the PbO nanoparticles was still visible in a TEM, using the process diffraction method. Both XRD and SAED proved to be useful for the evaluation of the results of the milling process and compaction. PMID:16060145

  15. Investigation of the capacity retention mechanisms in novel composite sulfur copolymer-base cathodes for high-energy density Li-S batteries

    NASA Astrophysics Data System (ADS)

    Oleshko, Vladimir; Kim, Jenny; Masser, Kevin; Hudson, Steven; Soles, Christopher; Griebel, Jared; Chung, Woo Jin; Simmonds, Adam; Pyun, Jeffrey

    2013-03-01

    Utilization of the active cathode material in high-energy density Li-S batteries limited by the insulating nature of sulfur and losses in the form of insoluble polysulfides was improved by the use of 1,3-diisopropenylbenzene (DIB) copolymerized with molten sulfur. This approach termed, inverse vulcanization, transforms elemental sulfur into chemically stable processable copolymer forms with tunable thermomechanical properties. According to dielectric spectroscopy and dc conductivity measurements, composite sulfur-DIB copolymer cathodes exhibit a glassy-state beta relaxation related to short sulfur segments or to the DIB cross-linker. High-resolution AEM and FESEM studies down to the atomic scale reveal multiscale 3D-architectures created within the pristine and cycled composite cathodes with various contents of the electroactive copolymers. The morphology, structures, bonding and local compositional distributions of the constituents (sulfur, copolymers, aggregated conductive carbon nanoparticles) as well as extended pore structures and their transformations under cycling have been examined to provide insights into mechanisms of the enhanced capacity retention in the modified Li-S cells. NIST support under grant MML12-1053-N00

  16. High energy flux thermo-mechanical test of 1D-carbon-carbon fibre composite prototypes for the SPIDER diagnostic calorimeter

    SciTech Connect

    De Muri, M. Pasqualotto, R.; Dalla Palma, M.; Cervaro, V.; Fasolo, D.; Franchin, L.; Tollin, M.; Serianni, G.; Cavallin, T.; Greuner, H.; Böswirth, B.

    2014-02-15

    Operation of the thermonuclear fusion experiment ITER requires additional heating via injection of neutral beams from accelerated negative ions. In the SPIDER test facility, under construction in Padova, the production of negative ions will be studied and optimised. STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) is a diagnostic used to characterise the SPIDER beam during short pulse operation (several seconds) to verify if the beam meets the ITER requirements about the maximum allowed beam non-uniformity (below ±10%). The major components of STRIKE are 16 1D-CFC (Carbon-Carbon Fibre Composite) tiles, observed at the rear side by a thermal camera. This contribution gives an overview of some tests under high energy particle flux, aimed at verifying the thermo-mechanical behaviour of several CFC prototype tiles. The tests were performed in the GLADIS facility at IPP (Max-Plank-Institut für Plasmaphysik), Garching. Dedicated linear and nonlinear simulations were carried out to interpret the experiments and a comparison of the experimental data with the simulation results is presented. The results of some morphological and structural studies on the material after exposure to the GLADIS beam are also given.

  17. High energy physics

    SciTech Connect

    Kernan, A.; Shen, B.C.; Ma, E.

    1997-07-01

    This proposal is for the continuation of the High Energy Physics program at the University of California at Riverside. In hadron collider physics the authors will complete their transition from experiment UA1 at CERN to the DZERO experiment at Fermilab. On experiment UA1 their effort will concentrate on data analysis at Riverside. At Fermilab they will coordinate the high voltage system for all detector elements. They will also carry out hardware/software development for the D0 muon detector. The TPC/Two-Gamma experiment has completed its present phase of data-taking after accumulating 160 pb{sup {minus}}1 of luminosity. The UC Riverside group will continue data and physics analysis and make minor hardware improvement for the high luminosity run. The UC Riverside group is participating in design and implementation of the data acquisition system for the OPAL experiment at LEP. Mechanical and electronics construction of the OPAL hadron calorimeter strip readout system is proceeding on schedule. Data analysis and Monte Carlo detector simulation efforts are proceeding in preparation for the first physics run when IEP operation comenses in fall 1989.

  18. High energy physics

    SciTech Connect

    Kernan, A.; Shen, B.C.; Ma, E.

    1997-07-01

    This proposal is for the continuation of the High Energy Physics Program at the University of California, Riverside. In 1990, we will concentrate on analysis of LEP data from the OPAL detector. We expect to record 10{sup 5} Z`s by the end of 1989 and 10{sup 6} in 1990. This data will be used to measure the number of quark-lepton families in the universe. In the second half of 1990 we will also be occupied with the installation of the D-Zero detector in the Tevatron Collider and the preparation of software for the 1991 run. A new initiative made possible by generous university support is a laboratory for detector development at UCR. The focus will be on silicon strip tracking detectors both for the D-Zero upgrade and for SSC physics. The theory program will pursue further various mass-generating radiative mechanisms for understanding small quark and lepton masses as well as some novel phenomenological aspects of supersymmetry.

  19. Magnetic heating characteristics of La0.7SrxCa0.3-xMnO3 nanoparticles fabricated by a high energy mechanical milling method

    NASA Astrophysics Data System (ADS)

    Do, Hung Manh; Pham, Hong Nam; Chien Nguyen, Van; Bich Hoa Phan, Thi; Tran, Dai Lam; Nguyen, Anh Tuan; Thong Phan, Quoc; Le, Van Hong; Phuc Nguyen, Xuan

    2011-09-01

    Magnetic inductive heating (MIH) of nanoparticles (NPs) attracts considerable research attention, first because of its application to hyperthermia in biological tissues. Most reports so far have dealt with magnetite NPs with a Curie temperature, TC, of as high as above 500 °C. In this paper, we present results of a MIH study in an ac field of frequency 219 and 236 kHz and strength of 40–100 Oe for several samples of La0.7SrxCa0.3‑x MnO3 NPs of TC in the region of hyperthermia, that is some tens of degrees above human body temperature. The particle materials were fabricated by a high energy mechanical milling method combined with calcining at various temperatures in the range of 600–900 °C. The heating temperatures of the samples were observed to saturate at a field irradiating time of less than 10 min and at temperatures ranging from 40 to 75 °C depending on the strontium content, the NP concentration, c, and the field parameters. A sudden change in heating rate was clearly revealed in several heating curves for the case of low applied field and low c, which was considered to be related to the onset of a strong decrease in zero-field cooling (ZFC) magnetization of NPs. The initial temperature increase slope, dT/dt, and the saturation temperature, Ts will be analyzed as dependent on the NP concentration. Field dependences of the specific loss power will be analyzed and discussed for various concentrations, c. Evidence of fluid viscosity influence will also be noted.

  20. Analysis of Jovian decametric data: Study of radio emission mechanisms

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Arias, T. A.; Garnavich, P. M.; Rosenkranz, P. W.

    1985-01-01

    The Voyager 1 and Voyager 2 Planetary Radio Astronomy Experiments (PRA) have produced the finest set of Jovian decametric radio emission data ever obtained. Jovian decametric L-burst and S-burst arcs were characterized and the data reconciled with models for the radio emission geometry and mechanisms. The first major results involve comparisons of the distribution of arc separations with longitudes. The identification and analyses of systematic variations in the PRA data have yielded interesting results, but only the most obvious features of the data were examined. Analyses of the PRA data were extended with the use of new 6-Sec formats that are more sensitive to the S-bursts.

  1. ON THE VERY HIGH ENERGY SPECTRUM OF THE CRAB PULSAR

    SciTech Connect

    Chkheidze, N.; Machabeli, G.; Osmanov, Z.

    2011-04-01

    In the present paper, we construct a self-consistent theory interpreting the observations from the MAGIC Cherenkov Telescope of the very high energy (VHE) pulsed emission from the Crab pulsar. In particular, on the basis of Vlasov's kinetic equation, we study the process of quasi-linear diffusion (QLD) developed by means of the cyclotron instability. This mechanism provides simultaneous generation of low (radio) and VHE (0.01-25 GeV) emission on light cylinder scales in one location of the pulsar magnetosphere. A different approach to the synchrotron emission is considered, giving the spectral index of the VHE emission ({beta} = 2) and the exponential cutoff energy (23 GeV) in good agreement with the observational data.

  2. High-energy detector

    DOEpatents

    Bolotnikov, Aleksey E.; Camarda, Giuseppe; Cui, Yonggang; James, Ralph B.

    2011-11-22

    The preferred embodiments are directed to a high-energy detector that is electrically shielded using an anode, a cathode, and a conducting shield to substantially reduce or eliminate electrically unshielded area. The anode and the cathode are disposed at opposite ends of the detector and the conducting shield substantially surrounds at least a portion of the longitudinal surface of the detector. The conducting shield extends longitudinally to the anode end of the detector and substantially surrounds at least a portion of the detector. Signals read from one or more of the anode, cathode, and conducting shield can be used to determine the number of electrons that are liberated as a result of high-energy particles impinge on the detector. A correction technique can be implemented to correct for liberated electron that become trapped to improve the energy resolution of the high-energy detectors disclosed herein.

  3. High Energy Astrophysics Program

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This report reviews activities performed by members of the USRA (Universities Space Research Association) contract team during the six months during the reporting period (10/95 - 3/96) and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics. Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA), X-ray Timing Experiment (XTE), X-ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science, Archive Research Center (HEASARC), and others.

  4. High Energy Astrophysics Program

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This report reviews activities performed-by members of the USRA contract team during the six months of the reporting period and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, visiting the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics. Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA); X-ray Timing Experiment (XTE); X-ray Spectrometer (XRS); Astro-E; High Energy Astrophysics Science Archive Research Center (HEASARC), and others.

  5. High energy particle astronomy.

    NASA Technical Reports Server (NTRS)

    Buffington, A.; Muller, R. A.; Smith, L. H.; Smoot, G. F.

    1972-01-01

    Discussion of techniques currently used in high energy particle astronomy for measuring charged and neutral cosmic rays and their isotope and momentum distribution. Derived from methods developed for accelerator experiments in particle physics, these techniques help perform important particle astronomy experiments pertaining to nuclear cosmic ray and gamma ray research, electron and position probes, and antimatter searches.

  6. High Energy Astronomy Observatory

    NASA Technical Reports Server (NTRS)

    1980-01-01

    An overview of the High Energy Astronomy Observatory 2 contributions to X-ray astronomy is presented along with a brief description of the satellite and onboard telescope. Observations relating to galaxies and galactic clusters, black holes, supernova remnants, quasars, and cosmology are discussed.

  7. UNDERSTANDING THE UNUSUAL X-RAY EMISSION PROPERTIES OF THE MASSIVE, CLOSE BINARY WR 20a: A HIGH ENERGY WINDOW INTO THE STELLAR WIND INITIATION REGION

    SciTech Connect

    Montes, Gabriela; Ramirez-Ruiz, Enrico; De Colle, Fabio; Strickler, Rachel

    2013-11-10

    The problem of explaining the X-ray emission properties of the massive, close binary WR 20a is discussed. Located near the cluster core of Westerlund 2, WR 20a is composed of two nearly identical Wolf-Rayet stars of 82 and 83 solar masses orbiting with a period of only 3.7 days. Although Chandra observations were taken during the secondary optical eclipse, the X-ray light curve shows no signs of a flux decrement. In fact, WR 20a appears slightly more X-ray luminous and softer during the optical eclipse, opposite to what has been observed in other binary systems. To aid in our interpretation of the data, we compare with the results of hydrodynamical simulations using the adaptive mesh refinement code Mezcal which includes radiative cooling and a radiative acceleration force term. It is shown that the X-ray emission can be successfully explained in models where the wind-wind collision interface in this system occurs while the outflowing material is still being accelerated. Consequently, WR 20a serves as a critical test-case for how radiatively driven stellar winds are initiated and how they interact. Our models not only procure a robust description of current Chandra data, which cover the orbital phases between 0.3 and 0.6, but also provide detailed predictions over the entire orbit.

  8. Modelling of the spectral energy distribution of Fornax A: leptonic and hadronic production of high-energy emission from the radio lobes

    NASA Astrophysics Data System (ADS)

    McKinley, B.; Yang, R.; López-Caniego, M.; Briggs, F.; Hurley-Walker, N.; Wayth, R. B.; Offringa, A. R.; Crocker, R.; Bernardi, G.; Procopio, P.; Gaensler, B. M.; Tingay, S. J.; Johnston-Hollitt, M.; McDonald, M.; Bell, M.; Bhat, N. D. R.; Bowman, J. D.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Emrich, D.; Ewall-Wice, A.; Feng, L.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hewitt, J. N.; Hindson, L.; Jacobs, D.; Kaplan, D. L.; Kasper, J. C.; Kratzenberg, E.; Kudryavtseva, N.; Lenc, E.; Lonsdale, C. J.; Lynch, M. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Pindor, B.; Prabu, T.; Riding, J.; Rogers, A. E. E.; Roshi, D. A.; Udaya Shankar, N.; Srivani, K. S.; Subrahmanyan, R.; Waterson, M.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

    2015-02-01

    We present new low-frequency observations of the nearby radio galaxy Fornax A at 154 MHz with the Murchison Widefield Array, microwave flux-density measurements obtained from WMAP and Planck data, and γ-ray flux densities obtained from Fermi data. We also compile a comprehensive list of previously published images and flux-density measurements at radio, microwave and X-ray energies. A detailed analysis of the spectrum of Fornax A between 154 and 1510 MHz reveals that both radio lobes have a similar spatially averaged spectral index, and that there exists a steep-spectrum bridge of diffuse emission between the lobes. Taking the spectral index of both lobes to be the same, we model the spectral energy distribution of Fornax A across an energy range spanning 18 orders of magnitude, to investigate the origin of the X-ray and γ-ray emission. A standard leptonic model for the production of both the X-rays and γ-rays by inverse-Compton scattering does not fit the multiwavelength observations. Our results best support a scenario where the X-rays are produced by inverse-Compton scattering and the γ-rays are produced primarily by hadronic processes confined to the filamentary structures of the Fornax A lobes.

  9. Detection of high-energy gamma-ray emission from the BL Lacertae object Markarian 421 by the Egret telescope on the Compton Observatory

    NASA Technical Reports Server (NTRS)

    Lin, Y. C.; Bertsch, D. L.; Chiang, J.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Kwok, P. W.; Mattox, J. R.

    1992-01-01

    Gamma radiation in the energy range from 50 MeV to well over 1 GeV has been observed from the direction of the BL Lac object Markarian 421 by the Energetic Gamma Ray Experiment Telescope on the Compton Observatory during the period 1991 June 27-July 11. The source flux is weak, but still statistically significant at the level of 10 exp -5; the integrated photon flux above 100 MeV is (1.4 +/- 0.3) x 10 exp -7/sq cm s. The differential photon energy spectrum can be represented by a power law with exponent 1.96 +/- 0.14. This is the first detection of gamma-ray emission from a BL Lac object.

  10. Long-Term Monitoring of the High-Energy Gamma-Ray Emission from LS I +61 deg 303 and LS 5039

    NASA Technical Reports Server (NTRS)

    Hadasch, D.; Torres, D. F.; Tanaka, T.; Corbet, R. H. D.; Hill, A. B.; Dubois, R.; Dubus, G.; Glanzman, T.; Corbel, S.; Li, J.; Chen, Y. P.; Zhang, S.; Caliandro, G. A.; Kerr, M.; Richards, J. L.; Max-Moerbeck, W.; Readhead, A.; Pooley, G.

    2012-01-01

    The Fermi Large Area Telescope (LAT) reported the first definitive gigaelectron volts detections of the binaries LS I +61 deg 303 and LS 5039 in the first year after its launch in 2008 June. These detections were unambiguous as a consequence of the reduced positional uncertainty and the detection of modulated gamma-ray emission on the corresponding orbital periods. An analysis of new data from the LAT, comprising 30 months of observations, identifies a change in the gamma-ray behavior of LS I +61 deg 303. An increase in flux is detected in 2009 March and a steady decline in the orbital flux modulation is observed. Significant emission up to 30 gigaelectron volts is detected by the LAT; prior data sets led to upper limits only. Contemporaneous terraelectron volt observations no longer detected the source, or found it-in one orbit-close to periastron, far from the phases at which the source previously appeared at terraelectron volt energies. The detailed numerical simulations and models that exist within the literature do not predict or explain many of these features now observed at gigaelectron volt and terraelectron volt energies. New ideas and models are needed to fully explain and understand this behavior. A detailed phase-resolved analysis of the spectral characterization of LS I +61 deg 303 in the gigaelectron volt regime ascribes a power law with an exponential cutoff spectrum along each analyzed portion of the system's orbit. The on-source exposure of LS 5039 is also substantially increased with respect to our prior publication. In this case, whereas the general gamma-ray properties remain consistent, the increased statistics of the current data set allows for a deeper investigation of its orbital and spectral evolution.

  11. A derivation of bulk-motion insensitive implosion metrics inferred from neutron and high-energy x-ray emission in a series of high yield implosions on the NIF

    NASA Astrophysics Data System (ADS)

    Springer, P. T.; Macphee, A. G.; Hurricane, O. A.; Callahan, D. A.; Casey, D. T.; Cerjan, C. J.; Dewald, E. L.; Dittrich, T. R.; Doeppner, T.; Edgell, D. H.; Edwards, M. J.; Gaffney, J.; Grim, G. P.; Haan, S.; Hammer, J. H.; Hinkel, D. E.; Berzak Hopkins, L. F.; Jones, O.; Kritcher, A. L.; Le Pape, S.; Ma, T.; Milovich, J.; Munro, D. H.; Pak, A.; Park, H. S.

    2015-11-01

    A suite of nuclear and x-ray data is used to deduce key implosion performance metrics at stagnation including the hotspot pressure, energy, and the role of alpha heating on producing the observed yield. Key to this analysis is a determination of the burn-averaged temperature of the hot plasma so that the nuclear reactivity and yield can then be used to deduce the plasma density and pressure. In this presentation we examine the systematics of both neutron and high-energy x-ray emission (22 keV x-ray monochromator) from a series of high yield implosions on the NIF. The advantage of incorporating high energy x-rays into the analysis is their insignificant attenuation and insensitivity to bulk flows, thus providing insight as to whether these effects complicate the interpretation of the nuclear data, and that a precipitous drop in their production is expected as the thermal temperature is reduced. A dynamic model for hotspot assembly is developed that incorporates thermal conduction, radiative losses, and alpha heating, which simultaneously matches both neutron and x-ray data with nearly identical nuclear and x-ray derived thermal temperatures. Work performed under the auspices of the USDoE by Lawrence Livermore National Laboratory under contract DE-AC52-07NA273.

  12. Improvement of field emission properties of α-Fe{sub 2}O{sub 3} nanoflakes due to the lowered back contact barrier after high energy X-ray irradiation

    SciTech Connect

    Wu, J. Q.; Deng, S. Z.; Xu, N. S.; Chen, Jun; Wang, B.; Yi, F. T.

    2013-11-14

    Improvement in the field emission properties of α-Fe{sub 2}O{sub 3} nanoflakes is observed after high energy X-ray irradiation from synchrotron radiation. Field emission threshold field of α-Fe{sub 2}O{sub 3} nanoflakes is found to decrease from 10.1 to 7.8 MV/m after X-ray irradiation with the dose of 9.0 × 10{sup 14} phs/cm{sup 2}. Electrical measurement reveals that the potential barrier at the back contact between the α-Fe{sub 2}O{sub 3} layer and the iron substrate changes after X-ray irradiation. The observed threshold field decrease is well explained by the changes in potential barrier at the back contact of α-Fe{sub 2}O{sub 3} nanoflakes, which indicates the back contact plays an important role in controlling the field emission properties of α-Fe{sub 2}O{sub 3} nanoflakes. Our study shows that the α-Fe{sub 2}O{sub 3} nanoflakes are a promising material for the application as field emitter under X-ray environment.

  13. High energy from space

    NASA Technical Reports Server (NTRS)

    Margon, Bruce; Canizares, Claude; Catura, Richard C.; Clark, George W.; Fichtel, Carl E.; Friedman, Herbert; Giacconi, Riccardo; Grindlay, Jonathan E.; Helfand, David J.; Holt, Stephen S.

    1991-01-01

    The following subject areas are covered: (1) important scientific problems for high energy astrophysics (stellar activity, the interstellar medium in galaxies, supernovae and endpoints of stellar evolution, nucleosynthesis, relativistic plasmas and matter under extreme conditions, nature of gamma-bursts, identification of black holes, active nuclei, accretion physics, large-scale structures, intracluster medium, nature of dark matter, and the X- and gamma-ray background); (2) the existing experimental programs (Advanced X-Ray Astrophysics Facility (AXAF), Gamma Ray Observatory (GRO), X-Ray Timing Explorer (XTE), High Energy Transient Experiment (HETE), U.S. participation in foreign missions, and attached Shuttle and Space Station Freedom payloads); (3) major missions for the 1990's; (4) a new program of moderate missions; (5) new opportunities for small missions; (6) technology development issues; and (7) policy issues.

  14. High energy transients

    NASA Technical Reports Server (NTRS)

    Woosley, S. E.

    1984-01-01

    A meeting was convened on the campus of the University of California at Santa Cruz during the two-week interval July 11 through July 22, 1983. Roughly 100 participants were chosen so as to give broad representation to all aspects of high energy transients. Ten morning review sessions were held in which invited speakers discussed the current status of observations and theory of the above subjects. Afternoon workshops were also held, usually more than one per day, to informally review various technical aspects of transients, confront shortcomings in theoretical models, and to propose productive courses for future research. Special attention was also given to the instrumentation used to study high energy transient and the characteristics and goals of a dedicated space mission to study transients in the next decade were determined. A listing of articles written by various members of the workshop is included.

  15. High energy beam lines

    NASA Astrophysics Data System (ADS)

    Marchetto, M.; Laxdal, R. E.

    2014-01-01

    The ISAC post accelerator comprises an RFQ, DTL and SC-linac. The high energy beam lines connect the linear accelerators as well as deliver the accelerated beams to two different experimental areas. The medium energy beam transport (MEBT) line connects the RFQ to the DTL. The high energy beam transport (HEBT) line connects the DTL to the ISAC-I experimental stations (DRAGON, TUDA-I, GPS). The DTL to superconducting beam (DSB) transport line connects the ISAC-I and ISAC-II linacs. The superconducting energy beam transport (SEBT) line connects the SC linac to the ISAC-II experimental station (TUDA-II, HERACLES, TIGRESS, EMMA and GPS). All these lines have the function of transporting and matching the beams to the downstream sections by manipulating the transverse and longitudinal phase space. They also contain diagnostic devices to measure the beam properties.

  16. INSIGHTS INTO THE HIGH-ENERGY {gamma}-RAY EMISSION OF MARKARIAN 501 FROM EXTENSIVE MULTIFREQUENCY OBSERVATIONS IN THE FERMI ERA

    SciTech Connect

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Baring, M. G.; Bastieri, D.; Bonamente, E.; Brandt, T. J. E-mail: stawarz@astro.isas.jaxa.jp

    2011-02-01

    We report on the {gamma}-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) {gamma}-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 {+-} 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 {+-} 0.14, and the softest one is 2.51 {+-} 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size {approx}<0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power ({approx_equal}10{sup 44} erg s{sup -1}) constitutes only a small fraction ({approx}10{sup -3}) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a

  17. Insights into the High-energy γ-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi Era

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cannon, A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Palma, F.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Frailis, M.; Fuhrmann, L.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Guillemot, L.; Guiriec, S.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kadler, M.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Max-Moerbeck, W.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Nishino, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Parent, D.; Pavlidou, V.; Pearson, T. J.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Readhead, A.; Reimer, A.; Reimer, O.; Richards, J. L.; Ripken, J.; Ritz, S.; Roth, M.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Scargle, J. D.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stawarz, Ł.; Stevenson, M.; Strickman, M. S.; Sokolovsky, K. V.; Suson, D. J.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Wehrle, A. E.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ylinen, T.; Zensus, J. A.; Ziegler, M.; Fermi LAT Collaboration; Aleksić, J.; Antonelli, L. A.; Antoranz, P.; Backes, M.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, G.; Bordas, P.; Borla Tridon, D.; Bosch-Ramon, V.; Bose, D.; Braun, I.; Bretz, T.; Camara, M.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Dazzi, F.; de Angelis, A.; De Cea del Pozo, E.; De Lotto, B.; De Maria, M.; De Sabata, F.; Delgado Mendez, C.; Diago Ortega, A.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giavitto, G.; Godinovi, N.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Jogler, T.; Klepser, S.; Krähenbühl, T.; Kranich, D.; Krause, J.; La Barbera, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; López, M.; Lorenz, E.; Majumdar, P.; Makariev, E.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moralejo, A.; Nieto, D.; Nilsson, K.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Partini, S.; Pasanen, M.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, J.; Pochon, J.; Prada Moroni, P. G.; Prada, F.; Prandini, E.; Puchades, N.; Puljak, I.; Reichardt, T.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rissi, M.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Sánchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sierpowska-Bartosik, A.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Steinke, B.; Storz, J.; Strah, N.; Struebig, J. C.; Suric, T.; Takalo, L. O.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Vankov, H.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Acciari, V. A.; Arlen, T.; Aune, T.; Benbow, W.; Boltuch, D.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Dickherber, R.; Errando, M.; Falcone, A.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.

    2011-02-01

    We report on the γ-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) γ-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 ± 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 ± 0.14, and the softest one is 2.51 ± 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15—August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size lsim0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (sime1044 erg s-1) constitutes only a small fraction (~10-3) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk

  18. Magnetic Reconnection-Powered Relativistic Particle Acceleration, High-Energy Gamma-Ray Emission, and Pair Production in Coronae of Accreting Black Holes

    NASA Astrophysics Data System (ADS)

    Uzdensky, Dmitri

    2015-11-01

    Magnetic reconnection is a fundamental plasma process believed to play an important role in energetics of magnetically-dominated coronae of various astrophysical objects including accreting black holes. Building up on recent advances in kinetic simulations of relativistic collisionless reconnection, we investigate nonthermal particle acceleration and its key observational consequences for these systems. We argue that reconnection can efficiently accelerate coronal electrons (as well as ions) up to hundreds of MeV or even GeV energies. In brightest systems, radiation back-reaction due to inverse-Compton (and/or synchrotron) emission becomes important at these energies and limits any further electron acceleration, thereby turning reconnection layers into powerful and efficient radiators of γ-rays. We then evaluate the rate of absorption of the resulting γ-ray photons by the ambient soft (X-ray) photon fields and show that it can be a significant source of pair production, with important implications for the composition of black-hole coronae and jets. Finally, we assess the prospects of laboratory studies of magnetic reconnection in the physical regimes relevant to black-hole accretion flows using modern and future laser-plasma facilities. This work is supported by DOE, NSF, and NASA.

  19. X-ray Emission Characteristics of Ultra-High Energy Density Relativistic Plasmas Created by Ultrafast Laser Irradiation of Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Hollinger, R. C.; Bargsten, C.; Shlyaptsev, V. N.; Pukhov, A.; Purvis, M. A.; Townsend, A.; Keiss, D.; Wang, Y.; Wang, S.; Prieto, A.; Rocca, J. J.

    2014-10-01

    Irradiation of ordered nanowire arrays with high contrast femtosecond laser pulses of relativistic intensity creates volumetrically heated near solid density plasmas characterized by multi-KeV temperatures and extreme degrees of ionization. The large hydrodynamic-to-radiative lifetime ratio of these plasmas results in very efficient X-ray generation. Au nanowire array plasmas irradiated at I 5×1018 Wcm-2 are measured to convert ~ 5 percent of the laser energy into h ν > 0.9 KeV X-rays, and >1 × 10-4 into h ν > 9 KeV photons, creating bright picosecond X-ray sources. The angular distribution of the higher energy photons is measured to change from isotropic into annular as the intensity increases, while softer X-ray emission (h ν >1 KeV) remains isotropic and nearly unchanged. Model simulations suggest the unexpected annular distribution of the hard X-rays might result from bremsstrahlung of fast electrons confined in a high aspect ratio near solid density plasma in which the electron-ion collision mean free-path is of the order of the plasma thickness. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency Grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

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

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Masaki

    2012-07-01

    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 (γ < 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 γ_{min} is around 10^3. In addition, we show that the Suzaku light curve is well reproduced if γ_{min} varies in proportion to the Fermi flux.

  1. Generation mechanism of whistler-mode chorus emissions

    NASA Astrophysics Data System (ADS)

    Omura, Yoshiharu

    2012-07-01

    Whistler-mode chorus emissions are coherent waves with rising frequencies due to the nonlinear wave growth mechanism [1,2] driven by formation of electromagnetic electron hole in the velocity phase space. The nonlinear wave growth is induced by a triggering wave that is either naturally growing or artificially injected at a constant frequency. The frequency increase is induced by gradual formation of the symmetric electron hole near the equator. The increase of the frequency breaks the symmetry of the electron hole, resulting in the negative resonant current parallel to the wave electric field [3]. The negative resonant current causes the wave growth with the progressively increasing frequency. The process is an absolute instability near the equator, generating seeds of chorus emissions. The nonlinear wave growth also takes place through propagation from the equator because the asymmetry of the electron hole is maintained by the inhomogeneous magnetic field. As the chorus wave packet propagates away from the equator, the wavenormal direction deviates from the parallel direction, resulting in a parallel electric field that appears as an electrostatic potential in the frame of reference moving with the phase velocity. Stable nonlinear trapping of electrons takes place because the group velocity is nearly equal to the phase velocity at half the cyclotron frequency as far as the wavenormal angle is small. The trapped electrons are accelerated in the parallel direction, while the wave packet undergoes the nonlinear damping at half the cyclotron frequency [2], being separated into the lower-band and upper-band chorus emissions. [1] Omura, Y., Y. Katoh, and D. Summers (2008), Theory and simulation of the generation of whistler-mode chorus, J. Geophys. Res., 113, A04223, doi:10.1029/2007JA012622. [2] Omura, Y., , M. Hikishima, Y. Katoh, D. Summers, and S. Yagitani (2009), Nonlinear mechanisms of lower band and upper band VLF chorus emissions in the magnetosphere, Journal

  2. Ultra high energy neutrinos: absorption, thermal effects and signatures

    SciTech Connect

    Lunardini, Cecilia; Sabancilar, Eray; Yang, Lili E-mail: Eray.Sabancilar@asu.edu

    2013-08-01

    We study absorption of ultra high energy neutrinos by the cosmic neutrino background, with full inclusion of the effect of the thermal distribution of the background on the resonant annihilation channel. For a hierarchical neutrino mass spectrum (with at least one neutrino with mass below ∼ 10{sup −2} eV), thermal effects are important for ultra high energy neutrino sources at z∼>16. The neutrino transmission probability shows no more than two separate suppression dips since the two lightest mass eigenstates contribute as a single species when thermal effects are included. Results are applied to a number of models of ultra high energy neutrino emission. Suppression effects are strong for sources that extend beyond z ∼ 10, which can be realized for certain top down scenarios, such as superheavy dark matter decays, cosmic strings and cosmic necklaces. For these, a broad suppression valley should affect the neutrino spectrum at least in the energy interval 10{sup 12}−10{sup 13} GeV — which therefore is disfavored for ultra high energy neutrino searches — with only a mild dependence on the neutrino mass spectrum and hierarchy. The observation of absorption effects would indicate a population of sources beyond z ∼ 10, and favor top-down mechanisms; it would also be an interesting probe of the physics of the relic neutrino background in the unexplored redshift interval z ∼ 10–100.

  3. Method for Simultaneously improving the thermal stability and mechanical properties of poly(lactic acid): effect of high-energy electrons on the morphological, mechanical, and thermal properties of PLA/MMT nanocomposites.

    PubMed

    Wang, De-Yi; Gohs, Uwe; Kang, Nian-Jun; Leuteritz, Andreas; Boldt, Regine; Wagenknecht, Udo; Heinrich, Gert

    2012-08-28

    Nanocomposites derived from poly(lactic acid) (PLA) and organically modified montmorillonite (oMMT) have been cross-linked by high-energy electrons in the presence of triallyl cyanurate (TAC). The morphology of untreated and cross-linked PLA/MMT nanocomposites was characterized by wide-angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). This treatment can improve both the thermal stability and the glass-transition temperatures of the PLA nanocomposites (e.g., PLA-MMT-TAC 30kGy, 50kGy, and 70kGy) because of the formation of cross-linking structures in the nanocomposites that will considerably reduce the mobility of polymers. Interestingly, at relatively low irradiation doses (e.g., 30 and 50 kGy) a good balance between tensile strength and elongation at break for the PLA nanocomposites could be achieved. These mechanical properties are superior to those of pure PLA. Therefore, combining nanotechnology and electron beam cross-linking is a promising new method of simultaneously improving the mechanical properties (toughness and tensile strength) and thermal stability of PLA. PMID:22845883

  4. Probing the high energy universe

    NASA Astrophysics Data System (ADS)

    Davies, John K.

    1988-04-01

    Techniques and programs involved with gamma-ray astronomy are discussed. The way in which information about high energy processes in the universe can be obtained from the study of gamma-ray emissions is reviewed. Coded mask telescopes, the French and Soviet Gamma-1 project to study gamma-rays in the 100-300 MeV energy range, and the French Sigma hard X-ray/medium energy gamma-ray experiment are considered. The planned NASA Gamma-Ray Observatory mission is described, including the burst and transient source, experiment, the Compton telescope, the energetic gamma-ray experimental telescope, and the oriented scintillation spectrometer experiment. Also, the proposed ESA Gamma-Ray Astronomy with Spectroscopy and Positioning mission is examined.

  5. High-energy transients.

    PubMed

    Gehrels, Neil; Cannizzo, John K

    2013-06-13

    We present an overview of high-energy transients in astrophysics, highlighting important advances over the past 50 years. We begin with early discoveries of γ-ray transients, and then delve into physical details associated with a variety of phenomena. We discuss some of the unexpected transients found by Fermi and Swift, many of which are not easily classifiable or in some way challenge conventional wisdom. These objects are important insofar as they underscore the necessity of future, more detailed studies. PMID:23630376

  6. Very high energy colliders

    NASA Astrophysics Data System (ADS)

    Richter, B.

    1985-05-01

    The required emittance in very high energy machines are small. It will be a real challenge to produce these small emittances and to maintain them during acceleration. The small emittances probably make acceleration by laser techniques easier, if such techniques will be practical at all. The beam spot sizes are very small indeed. It will be a challenge to design beam transport systems with the necessary freedom from aberration required for these small spot sizes. It would of course help if the beta functions at the collision points could be reduced. Beam power will be large - to paraphrase the old saying, power is money - and efficient acceleration systems will be required.

  7. High energy electron cooling

    SciTech Connect

    Parkhomchuk, V.

    1997-09-01

    High energy electron cooling requires a very cold electron beam. The questions of using electron cooling with and without a magnetic field are presented for discussion at this workshop. The electron cooling method was suggested by G. Budker in the middle sixties. The original idea of the electron cooling was published in 1966. The design activities for the NAP-M project was started in November 1971 and the first run using a proton beam occurred in September 1973. The first experiment with both electron and proton beams was started in May 1974. In this experiment good result was achieved very close to theoretical prediction for a usual two component plasma heat exchange.

  8. Theoretical High Energy Physics

    SciTech Connect

    Christ, Norman H.; Weinberg, Erick J.

    2014-07-14

    we provide reports from each of the six faculty supported by the Department of Energy High Energy Physics Theory grant at Columbia University. Each is followed by a bibliography of the references cited. A complete list of all of the publications in the 12/1/2010-04/30/2014 period resulting from research supported by this grant is provided in the following section. The final section lists the Ph.D. dissertations based on research supported by the grant that were submitted during this period.

  9. Comparison of Spitzer/IRAC Galactic Center Mid-IR Survey Results with X-ray and Radio Emission Due to High-Energy Processes in the Central 100 Parsecs

    NASA Technical Reports Server (NTRS)

    Gezari, D. Y.; Arendt, R. A.; Smith, R.; Yusef-Zadeh, F.; Stolovy, S.; Law, C.; Smith, H. A.; Moseley, Harvey; Ramirez, S.; Karr, J.

    2006-01-01

    We compare the results of a small region from our 3.6 - 8.0 micron Spitzer/IRAC imaging survey of 2 x 1.5 deg around the Galactic Center with x-ray and radio emission due to high energy processes. The region we studied covers 100 x 100 parsecs, and was chosen to include a rich collection of sources, including Sgr A* and the bright Sgr AWest infrared/radio source complex, the non-thermal radio filaments and the thermal: radio arches. In a 40 x 40 parsec subset of that region we also make a preliminary analysis of the correlation between approx.2300 x-ray sources identified by Muno et al. (2003) and 20,000 infrared sources from our survey. We also investigate the correlation between infrared and radio emission in the large-scale structures including the thermal radio arches and non-thermal radio filaments. We set constrictions on the synchrotron spectrum observed at radio and millimeter wavelengths extrapolated to 8 micons, and set limits on the midinfrared variability of Sgr A* during and after the coordinated multi-wavelength observing campaign in September 2004.

  10. Research program in theoretical high energy physics

    NASA Astrophysics Data System (ADS)

    Feldman, David; Fried, Herbert M.; Jevicki, Antal; Kang, Kyungsik; Tan, Chung-I.

    1989-06-01

    This year's research has dealt with: superstrings in the early universe; the invisible axion emissions from SN1987A; quartic interaction in Witten's superstring field theory; W-boson associated multiplicity and the dual parton model; cosmic strings and galaxy formation; cosmic strings and baryogenesis; quark flavor mixing; p p(-) scattering at TeV energies; random surfaces; ordered exponentials and differential equations; initial value and back-reaction problems in quantum field theory; string field theory and Weyl invariance; the renormalization group and string field theory; the evolution of scalar fields in an inflationary universe, with and without the effects of gravitational perturbations; cosmic string catalysis of skyrmion decay; inflation and cosmic strings from dynamical symmetry breaking; the physic of flavor mixing; string-inspired cosmology; strings at high-energy densities and complex temperatures; the problem of non-locality in string theory; string statistical mechanics; large-scale structures with cosmic strings and neutrinos; the delta expansion for stochastic quantization; high-energy neutrino flux from ordinary cosmic strings; a physical picture of loop bremsstrahlung; cylindrically-symmetric solutions of four-dimensional sigma models; large-scale structure with hot dark matter and cosmic strings; the unitarization of the odderon; string thermodynamics and conservation laws; the dependence of inflationary-universe models on initial conditions; the delta expansion and local gauge invariance; particle physics and galaxy formation; chaotic inflation with metric and matter perturbations; grand-unified theories, galaxy formation, and large-scale structure; neutrino clustering in cosmic-string-induced wakes; and infrared approximations to nonlinear differential equations.

  11. Hybrid plasmonic nanodevices: Switching mechanism for the nonlinear emission

    SciTech Connect

    Bragas, Andrea V.; Singh, Mahi R.

    2014-03-31

    Control of the light emission at the nanoscale is of central interest in nanophotonics due to the many applications in very different fields, ranging from quantum information to biophysics. Resonant excitation of surface plasmon polaritons in metal nanoparticles create nanostructured and enhanced light fields around those structures, which produce their strong interaction in a hybrid nanodevice with other plasmonic or non-plasmonic objects. This interaction may in turn also modulate the far field with important consequences in the applications. We show in this paper that the nonlinear emission from semiconductor quantum dots is strongly affected by the close presence of metal nanoparticles, which are resonantly excited. Using a pulsed laser, optical second harmonic is generated in the quantum dot, and it is highly enhanced when the laser is tuned around the nanoparticle plasmon resonance. Even more interesting is the demonstration of a switching mechanism, controlled by an external continuous-wave field, which can enhance or extinguish the SH signal, even when the pulsed laser is always on. Experimental observations are in excellent agreement with the theoretical calculations, based on the dipole-dipole near-field coupling of the objects forming the hybrid system.

  12. Analysis of Jovian decametric data: Study of radio emission mechanisms

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Arias, T. A.

    1985-01-01

    Data gathered by the Voyager 1 and Voyager 2 Planetary Radio Astronomy Experiments (PRA) are unique in many ways including their frequency range, time resolution, polarization information and geometric characteristics. Studies of rapidly varying phenomena have thus far been hampered by paper display techniques which require large amounts of paper to exploit the full PRA time resolution. A software package capable of effectively displaying full 6s resolution PRA dynamic spectra on a high quality video monitor while compensating for the aforementioned variations was developed. The most striking phenomena revealed by the new display techniques is called Modulated Spectral Activity (MSA) because of its appearance in dynamic spectra as a series at least two parallel emission bands which drift back and forth in frequency on time scales of tens of seconds. In an attempt to locate and understand the MSA source mechanism, a catalogue has been compiled of the start and end of all known MSA events.

  13. Mechanically flexible organic electroluminescent device with directional light emission

    DOEpatents

    Duggal, Anil Raj; Shiang, Joseph John; Schaepkens, Marc

    2005-05-10

    A mechanically flexible and environmentally stable organic electroluminescent ("EL") device with directional light emission comprises an organic EL member disposed on a flexible substrate, a surface of which is coated with a multilayer barrier coating which includes at least one sublayer of a substantially transparent organic polymer and at least one sublayer of a substantially transparent inorganic material. The device includes a reflective metal layer disposed on the organic EL member opposite to the substrate. The reflective metal layer provides an increased external quantum efficiency of the device. The reflective metal layer and the multilayer barrier coating form a seal around the organic EL member to reduce the degradation of the device due to environmental elements.

  14. Acoustic emission classification for failure prediction due to mechanical fatigue

    NASA Astrophysics Data System (ADS)

    Emamian, Vahid; Kaveh, Mostafa; Tewfik, Ahmed H.

    2000-06-01

    Acoustic Emission signals (AE), generated by the formation and growth of micro-cracks in metal components, have the potential for use in mechanical fault detection in monitoring complex- shaped components in machinery including helicopters and aircraft. A major challenge for an AE-based fault detection algorithm is to distinguish crack-related AE signals from other interfering transient signals, such as fretting-related AE signals and electromagnetic transients. Although under a controlled laboratory environment we have fewer interference sources, there are other undesired sources which have to be considered. In this paper, we present some methods, which make their decision based on the features extracted from time-delay and joint time-frequency components by means of a Self- Organizing Map (SOM) neural network using experimental data collected in a laboratory by colleagues at the Georgia Institute of Technology.

  15. Prospects at high energies

    SciTech Connect

    Quigg, C.

    1988-11-01

    I discuss some possibilities for neutrino experiments in the fixed-target environment of the SPS, Tevatron, and UNK, with their primary proton beams of 0.4, 0.9, and 3.0 TeV. The emphasis is on unfinished business: issues that have been recognized for some time, but not yet resolved. Then I turn to prospects for proton-proton colliders to explore the 1-TeV scale. I review the motivation for new physics in the neighborhood of 1 TeV and mention some discovery possibilities for high-energy, high-luminosity hadron colliders and the implications they would have for neutrino physics. I raise the possibility of the direct study of neutrino interactions in hadron colliders. I close with a report on the status of the SSC project. 38 refs., 17 figs.

  16. High energy X-ray diffraction study of the relationship between the macroscopic mechanical properties and microstructure of irradiated HT-9 steel

    NASA Astrophysics Data System (ADS)

    Tomchik, C.; Almer, J.; Anderoglu, O.; Balogh, L.; Brown, D. W.; Clausen, B.; Maloy, S. A.; Sisneros, T. A.; Stubbins, J. F.

    2016-07-01

    Samples harvested from an HT-9 fuel test assembly (ACO-3) irradiated for six years in the Fast Flux Test Facility (FFTF) reaching 2-147 dpa at 382-504 °C were deformed in-situ while collecting high-energy X-ray diffraction data to monitor microstructure evolution. With the initiation of plastic deformation, all samples exhibited a clear load transfer from the ferrite matrix to carbide particulate. This behavior was confirmed by modeling of the control material. The evolution of dislocation density in the material as a result of deformation was characterized through full pattern line profile analysis. The dislocation densities increased substantially after deformation, the level of dislocation evolution observed was highly dependent upon the irradiation temperature of the sample. Differences in both the yield and hardening behavior between samples irradiated at higher and lower temperatures suggest the existence of a transition in tensile behavior at an irradiation temperature near 420 °C dividing regions of distinct damage effects.

  17. A mechanism for biologically induced iodine emissions from sea ice

    NASA Astrophysics Data System (ADS)

    Saiz-Lopez, A.; Blaszczak-Boxe, C. S.; Carpenter, L. J.

    2015-09-01

    Ground- and satellite-based measurements have reported high concentrations of iodine monoxide (IO) in coastal Antarctica. The sources of such a large iodine burden in the coastal Antarctic atmosphere remain unknown. We propose a mechanism for iodine release from sea ice based on the premise that micro-algae are the primary source of iodine emissions in this environment. The emissions are triggered by the biological production of iodide (I-) and hypoiodous acid (HOI) from micro-algae (contained within and underneath sea ice) and their diffusion through sea-ice brine channels, ultimately accumulating in a thin brine layer (BL) on the surface of sea ice. Prior to reaching the BL, the diffusion timescale of iodine within sea ice is depth-dependent. The BL is also a vital component of the proposed mechanism as it enhances the chemical kinetics of iodine-related reactions, which allows for the efficient release of iodine to the polar boundary layer. We suggest that iodine is released to the atmosphere via three possible pathways: (1) emitted from the BL and then transported throughout snow atop sea ice, from where it is released to the atmosphere; (2) released directly from the BL to the atmosphere in regions of sea ice that are not covered with snowpack; or (3) emitted to the atmosphere directly through fractures in the sea-ice pack. To investigate the proposed biology-ice-atmosphere coupling at coastal Antarctica we use a multiphase model that incorporates the transport of iodine species, via diffusion, at variable depths, within brine channels of sea ice. Model simulations were conducted to interpret observations of elevated springtime IO in the coastal Antarctic, around the Weddell Sea. While a lack of experimental and observational data adds uncertainty to the model predictions, the results nevertheless show that the levels of inorganic iodine (i.e. I2, IBr, ICl) released from sea ice through this mechanism could account for the observed IO concentrations during

  18. FSU High Energy Physics

    SciTech Connect

    Prosper, Harrison B.; Adams, Todd; Askew, Andrew; Berg, Bernd; Blessing, Susan K.; Okui, Takemichi; Owens, Joseph F.; Reina, Laura; Wahl, Horst D.

    2014-12-01

    The High Energy Physics group at Florida State University (FSU), which was established in 1958, is engaged in the study of the fundamental constituents of matter and the laws by which they interact. The group comprises theoretical and experimental physicists, who sometimes collaborate on projects of mutual interest. The report highlights the main recent achievements of the group. Significant, recent, achievements of the group’s theoretical physicists include progress in making precise predictions in the theory of the Higgs boson and its associated processes, and in the theoretical understanding of mathematical quantities called parton distribution functions that are related to the structure of composite particles such as the proton. These functions are needed to compare data from particle collisions, such as the proton-proton collisions at the CERN Large Hadron Collider (LHC), with theoretical predictions. The report also describes the progress in providing analogous functions for heavy nuclei, which find application in neutrino physics. The report highlights progress in understanding quantum field theory on a lattice of points in space and time (an area of study called lattice field theory), the progress in constructing several theories of potential new physics that can be tested at the LHC, and interesting new ideas in the theory of the inflationary expansion of the very early universe. The focus of the experimental physicists is the Compact Muon Solenoid (CMS) experiment at CERN. The report, however, also includes results from the D0 experiment at Fermilab to which the group made numerous contributions over a period of many years. The experimental group is particularly interested in looking for new physics at the LHC that may provide the necessary insight to extend the standard model (SM) of particle physics. Indeed, the search for new physics is the primary task of contemporary particle physics, one motivated by the need to explain certain facts, such as the

  19. Correlation of radiation-induced changes in mechanical properties and microstructural development of Alloy 718 irradiated with mixed spectra of high-energy protons and spallation neutrons

    NASA Astrophysics Data System (ADS)

    Sencer, B. H.; Bond, G. M.; Garner, F. A.; Hamilton, M. L.; Maloy, S. A.; Sommer, W. F.

    2001-07-01

    Alloy 718 is a γ '(Ni 3(Al,Ti))-γ″(Ni 3Nb) hardenable superalloy with attractive strength, and corrosion resistance. This alloy is a candidate material for use in accelerator production of tritium (APT) target and blanket applications, where it would have to withstand low-temperature irradiation by high-energy protons and spallation neutrons. The existing data base, relevant to such irradiation conditions, is very limited. Alloy 718 has therefore been exposed to a particle flux and spectrum at the Los Alamos Neutron Science Center (LANSCE), closely matching those expected in the APT target and blanket applications. The yield stress of Alloy 718 increases with increasing dose up to ˜0.5 dpa, and then decreases with further increase in dose. The uniform elongation, however, drastically decreases with increasing dose at very low doses (<0.5 dpa), and does not recover when the alloy later softens somewhat. Transmission electron microscopy (TEM) investigation of Alloy 718 shows that superlattice spots corresponding to the age-hardening precipitate phases γ ' and γ″ are lost from the diffraction patterns for Alloy 718 by only 0.6 dpa, the lowest proton-induced dose level achieved in this experiment. Examination of samples that were neutron irradiated to doses of only ˜0.1 dpa showed that precipitates are faintly visible in diffraction patterns but are rapidly becoming invisible. It is proposed that the γ ' and γ″ first become disordered (by <0.6 dpa), but remain as solute-rich aggregates that still contribute to the hardness at relatively low dpa levels, and then are gradually dispersed at higher doses.

  20. Unraveling the Voltage-Fade Mechanism in High-Energy-Density Lithium-Ion Batteries: Origin of the Tetrahedral Cations for Spinel Conversion

    SciTech Connect

    Mohanty, Debasish; Li, Jianlin; Abraham, Daniel P.; Huq, Ashfia; Payzant, E. Andrew; Wood, David L.; Daniel, Claus

    2014-09-30

    Discovery of high-voltage layered lithium-and manganese-rich (LMR) composite oxide electrode has dramatically enhanced the energy density of current Li-ion energy storage systems. However, practical usage of these materials is currently not viable because of their inability to maintain a consistent voltage profile (voltage fading) during subsequent charge-discharge cycles. This report rationalizes the cause of this voltage fade by providing the evidence of layer to spinel-like (LSL) structural evolution pathways in the host Li1.2Mn0.55Ni0.15Co0.1O2 LMR composite oxide. By employing neutron powder diffraction, and temperature dependent magnetic susceptibility, we show that LSL structural rearrangement in LMR oxide occurs through a tetrahedral cation intermediate via: i) diffusion of lithium atoms from octahedral to tetrahedral sites of the lithium layer [(LiLioct →LiLitet] which is followed by the dispersal of the lithium ions from the adjacent octahedral site of the metal layer to the tetrahedral sites of lithium layer [LiTM oct → LiLitet]; and ii) migration of Mn from the octahedral sites of the transition metal layer to the permanent octahedral site of lithium layer via tetrahedral site of lithium layer [MnTMoct MnLitet MnLioct)]. The findings opens the door to the potential routes to mitigate this atomic restructuring in the high-voltage LMR composite oxide cathodes by manipulating the composition/structure for practical use in high-energy-density lithium-ion batteries.

  1. Unraveling the Voltage-Fade Mechanism in High-Energy-Density Lithium-Ion Batteries: Origin of the Tetrahedral Cations for Spinel Conversion

    DOE PAGESBeta

    Mohanty, Debasish; Li, Jianlin; Abraham, Daniel P.; Huq, Ashfia; Payzant, E. Andrew; Wood, David L.; Daniel, Claus

    2014-09-30

    Discovery of high-voltage layered lithium-and manganese-rich (LMR) composite oxide electrode has dramatically enhanced the energy density of current Li-ion energy storage systems. However, practical usage of these materials is currently not viable because of their inability to maintain a consistent voltage profile (voltage fading) during subsequent charge-discharge cycles. This report rationalizes the cause of this voltage fade by providing the evidence of layer to spinel-like (LSL) structural evolution pathways in the host Li1.2Mn0.55Ni0.15Co0.1O2 LMR composite oxide. By employing neutron powder diffraction, and temperature dependent magnetic susceptibility, we show that LSL structural rearrangement in LMR oxide occurs through a tetrahedral cationmore » intermediate via: i) diffusion of lithium atoms from octahedral to tetrahedral sites of the lithium layer [(LiLioct →LiLitet] which is followed by the dispersal of the lithium ions from the adjacent octahedral site of the metal layer to the tetrahedral sites of lithium layer [LiTM oct → LiLitet]; and ii) migration of Mn from the octahedral sites of the transition metal layer to the permanent octahedral site of lithium layer via tetrahedral site of lithium layer [MnTMoct MnLitet MnLioct)]. The findings opens the door to the potential routes to mitigate this atomic restructuring in the high-voltage LMR composite oxide cathodes by manipulating the composition/structure for practical use in high-energy-density lithium-ion batteries.« less

  2. Recent experimental developments concerning the mechanisms underlying dust emission

    NASA Astrophysics Data System (ADS)

    McKenna Neuman, C. L.; Sanderson, R. S.; O'Brien, P.

    2012-12-01

    Field based studies have been invaluable in elucidating the great variability and complexity in natural surfaces that emit dust. Spanning hours to days, and meters to kilometers, measurements of the regional and global characteristics of dust emission and transport are contributing to a clearer understanding of these phenomena. This work has been complimented by the development of increasingly more sophisticated atmospheric dispersion models. Only very recently, however, has much attention been paid to the physics of dust emission from the bed surface that necessarily require precise, high frequency measurements over fractions of millimeters under carefully manipulated conditions. This paper provides an overview of recent advances in our understanding of the mechanisms of dust emission, as derived from experiments carried out in the Trent boundary layer wind tunnel by a variety of workers. Energy transfer to the bed surface through the impacts of saltating particles has long been recognized as crucial for the ejection of silt and clay sized particles from surfaces where interparticle bonding is significant. Using Particle Tracking Velocimetry (PTV) and laser Doppler anemometry (LDA), we are now able to measure the energy transfer to the surface and the consequent deformation/rupture for both loose and consolidated beds of silt. The coefficient of restitution is found to decrease with particle impact speed, although some compaction may also occur with plowing and displacement of loose bed material (Gordon and McKenna Neuman, 2009). Further consideration is given to wind pumping as an alternate mechanism for dust entrainment from surfaces that are armored; that is, where insufficient sand supply is available to the support the development of a saltation cloud. LDA and pressure tap measurements confirm that turbulent structures measured in the atmospheric boundary layer are able to penetrate into the pores of gravel sized material, and specifically, the smelter waste

  3. Increased chemical weathering of olivine in high-energy shelf seas can counteract human CO2 emissions and ocean acidification against a price well below that of CCS and other methods

    NASA Astrophysics Data System (ADS)

    de Boer, Poppe L.; Schuiling, Roelof D.

    2014-05-01

    In the reaction: Mg(Fe)2SiO4 (olivine) + 4 H2O 2 Mg(Fe)2+ + 4 OH- + H4SiO4, followed by 4 OH- + 4 CO2 4 HCO3-, CO2 is consumed, and Mg2+, Fe2+, H4SiO4 and HCO3- are produced. Contrary to the paradigm that olivine weathering in nature is a slow process, flume experiments show a fast reaction, consuming CO2, and raising the pH at short notice. Only under static conditions a silica coating develops that retards the reaction. In high-energy shallow marine environments such silica coatings are abraded so that the chemical reaction can continue. When kept in motion even large olivine grains and gravels, rubbing and bumping against each other and against other sediment grains, weather quickly. Experiments show that fine micron- to silt-sized olivine particles are produced, and that the chemical reaction is fast. The chemical weathering of 7 km3 olivine is needed on a yearly basis in order to compensate the human CO2 emissions. This seems much, but is of the same order of magnitude as the volume of fossil fuels (in oil equivalents ~10 km3) that are burnt annually. Olivine is readily available at the Earth' surface on all continents, and such volume of 7 km3 is exceeded by existing mines; e.g. the Bingham Canyon open pit mine in Utah has an excavated volume of 25 km3. Hydrocarbons, on the other hand, are commonly retrieved with great efforts, from great depths, and often at remote locations. Spreading of large amounts of olivine (and/or serpentinite) in high-energy shelf seas where coarse sand and gravel can be transported, will counteract human CO2 production by fossil fuel burning and ocean acidification against a price well below that of other methods; order of US 10.- per ton CO2. For example part of the continental shelf between the Shetland Isles and France, that is the Southern Bight of the North Sea, the English Channel and the Irish Sea, is covered with sand waves, and in and around the English Channel an area of well over 100,000 km2 experiences bed shear stresses

  4. High energy plasma accelerators

    SciTech Connect

    Tajima, T.

    1985-05-01

    Colinear intense laser beams ..omega../sub 0/, kappa/sub 0/ and ..omega../sub 1/, kappa/sub 1/ shone on a plasma with frequency separation equal to the electron plasma frequency ..omega../sub pe/ are capable of creating a coherent large longitudinal electric field E/sub L/ = mc ..omega../sub pe//e of the order of 1GeV/cm for a plasma density of 10/sup 18/ cm/sup -3/ through the laser beat excitation of plasma oscillations. Accompanying favorable and deleterious physical effects using this process for a high energy beat-wave accelerator are discussed: the longitudinal dephasing, pump depletion, the transverse laser diffraction, plasma turbulence effects, self-steepening, self-focusing, etc. The basic equation, the driven nonlinear Schroedinger equation, is derived to describe this system. Advanced accelerator concepts to overcome some of these problems are proposed, including the plasma fiber accelerator of various variations. An advanced laser architecture suitable for the beat-wave accelerator is suggested. Accelerator physics issues such as the luminosity are discussed. Applications of the present process to the current drive in a plasma and to the excitation of collective oscillations within nuclei are also discussed.

  5. High Energy Astrophysics Mission

    NASA Technical Reports Server (NTRS)

    White, Nicholas E.; Ormes, Jonathan F. (Technical Monitor)

    2000-01-01

    The nature of gravity and its relationship to the other three forces and to quantum theory is one of the major challenges facing us as we begin the new century. In order to make progress we must challenge the current theories by observing the effects of gravity under the most extreme conditions possible. Black holes represent one extreme, where the laws of physics as we understand them break down. The Universe as whole is another extreme, where its evolution and fate is dominated by the gravitational influence of dark matter and the nature of the Cosmological constant. The early universe represents a third extreme, where it is thought that gravity may somehow be unified with the other forces. NASA's "Cosmic Journeys" program is part of a NASA/NSF/DoE tri-agency initiative designed to observe the extremes of gravity throughout the universe. This program will probe the nature of black holes, ultimately obtaining a direct image of the event horizon. It will investigate the large scale structure of the Universe to constrain the location and nature of dark matter and the nature of the cosmological constant. Finally it will search for and study the highest energy processes, that approach those found in the early universe. I will outline the High Energy Astrophysics part of this program.

  6. High Energy Density Microwaves

    SciTech Connect

    Phillips, R.M.

    1999-04-01

    These proceedings represent papers presented at the RF98 Workshop entitled `High Energy Density Microwaves` held in California in October, 1998. The topics discussed were predominantly accelerator{minus}related. The Workshop dealt, for the most part, with the generation and control of electron beams, the amplification of RF signals, the design of mode converters, and the effect of very high RF field gradients. This Workshop was designed to address the concerns of the microwave tube industry worldwide, the plasma physicists who deal with very high beam currents and gigawatts of RF power, and researchers in accelerator centers around the world. Papers were presented on multibeam klystrons, gyrotron development, plasmas in microwave tubes, RF breakdown, and alternatives to conventional linear coliders at 1 TeV and above. The Workshop was partially sponsored by the US Department of Energy. There were 46 papers presented at the conference,out of which 19 have been abstracted for the Energy,Science and Technology database.(AIP)

  7. X-ray Emission Mechanisms in Herbig - Haro objects .

    NASA Astrophysics Data System (ADS)

    Bonito, R.; Orlando, S.; Peres, G.; Favata, F.; Rosner, R.

    X-ray emission in Herbig - Haro objects is a quite recent and uncommon finding still waiting full explanation. With the scope of explaining this X-ray emission, our project is devoted to model the interaction between a supersonic jet originating from a young stellar object and the ambient medium. We have performed a wide exploration of the parameter space to infer the configuration(s) which can give rise to X-ray emission very similar to what recently observed.

  8. Intrinsic mechanical behavior of femoral cortical bone in young, osteoporotic and bisphosphonate-treated individuals in low- and high energy fracture conditions

    DOE PAGESBeta

    Zimmermann, Elizabeth A.; Schaible, Eric; Gludovatz, Bernd; Schmidt, Felix N.; Riedel, Christoph; Krause, Matthias; Vettorazzi, Eik; Acevedo, Claire; Hahn, Michael; Püschel, Klaus; et al

    2016-02-16

    Bisphosphonates are a common treatment to reduce osteoporotic fractures. This treatment induces osseous structural and compositional changes accompanied by positive effects on osteoblasts and osteocytes. Here, we test the hypothesis that restored osseous cell behavior, which resembles characteristics of younger, healthy cortical bone, leads to improved bone quality. Microarchitecture and mechanical properties of young, treatment-naïve osteoporosis, and bisphosphonate-treated cases were investigated in femoral cortices. Tissue strength was measured using three-point bending. Collagen fibril-level deformation was assessed in non-traumatic and traumatic fracture states using synchrotron small-angle x-ray scattering (SAXS) at low and high strain rates. The lower modulus, strength and fibrilmore » deformation measured at low strain rates reflects susceptibility for osteoporotic low-energy fragility fractures. Independent of age, disease and treatment status, SAXS revealed reduced fibril plasticity at high strain rates, characteristic of traumatic fracture. We find the significantly reduced mechanical integrity in osteoporosis may originate from porosity and alterations to the intra/extrafibrillar structure, while the fibril deformation under treatment indicates improved nano-scale characteristics. In conclusion, losses in strength and fibril deformation at low strain rates correlate with the occurrence of fragility fractures in osteoporosis, while improvements in structural and mechanical properties following bisphosphonate treatment may foster resistance to fracture during physiological strain rates.« less

  9. Improving the gas barrier and mechanical properties of a-SiO x films synthesized at low temperature by using high energy and hydrogen flow rate control

    NASA Astrophysics Data System (ADS)

    Jin, Su B.; Long, Wen; Sahu, B. B.; Han, Jeon G.; Hori, M.

    2015-05-01

    Silicon-oxide thin films were deposited on polyethylene-terephthalate (PET) and glass substrates for applications in transparent barrier packaging and replacement display cover glasses by using plasma-enhanced chemical vapor deposition (PECVD). The bias conditions and the input power in the radio-frequency plasma were changed to optimize the gas barrier and the mechanical properties of the silicon-oxide thin film. We made an advanced plasma source for large-area PECVD (370 × 470 mm2 size). The dissociation of the octamethylycyclodisiloxane (OMCTS) precursor was controlled by using the plasma processing parameters. The gas barrier and the mechanical properties of the a-SiO x film were improved by controlling the plasma process parameters. The gas barrier and the mechanical properties of the coatings were examined using a Permatran (MOCON) system and a pencil hardness measurement. The chemical structure properties of the coatings were examined by using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The properties of the a-SiO x thin films were improved by the dissociation of OMCTS obtained by using various appropriate plasma processing parameters.

  10. Intrinsic mechanical behavior of femoral cortical bone in young, osteoporotic and bisphosphonate-treated individuals in low- and high energy fracture conditions

    NASA Astrophysics Data System (ADS)

    Zimmermann, Elizabeth A.; Schaible, Eric; Gludovatz, Bernd; Schmidt, Felix N.; Riedel, Christoph; Krause, Matthias; Vettorazzi, Eik; Acevedo, Claire; Hahn, Michael; Püschel, Klaus; Tang, Simon; Amling, Michael; Ritchie, Robert O.; Busse, Björn

    2016-02-01

    Bisphosphonates are a common treatment to reduce osteoporotic fractures. This treatment induces osseous structural and compositional changes accompanied by positive effects on osteoblasts and osteocytes. Here, we test the hypothesis that restored osseous cell behavior, which resembles characteristics of younger, healthy cortical bone, leads to improved bone quality. Microarchitecture and mechanical properties of young, treatment-naïve osteoporosis, and bisphosphonate-treated cases were investigated in femoral cortices. Tissue strength was measured using three-point bending. Collagen fibril-level deformation was assessed in non-traumatic and traumatic fracture states using synchrotron small-angle x-ray scattering (SAXS) at low and high strain rates. The lower modulus, strength and fibril deformation measured at low strain rates reflects susceptibility for osteoporotic low-energy fragility fractures. Independent of age, disease and treatment status, SAXS revealed reduced fibril plasticity at high strain rates, characteristic of traumatic fracture. The significantly reduced mechanical integrity in osteoporosis may originate from porosity and alterations to the intra/extrafibrillar structure, while the fibril deformation under treatment indicates improved nano-scale characteristics. In conclusion, losses in strength and fibril deformation at low strain rates correlate with the occurrence of fragility fractures in osteoporosis, while improvements in structural and mechanical properties following bisphosphonate treatment may foster resistance to fracture during physiological strain rates.

  11. Intrinsic mechanical behavior of femoral cortical bone in young, osteoporotic and bisphosphonate-treated individuals in low- and high energy fracture conditions

    PubMed Central

    Zimmermann, Elizabeth A.; Schaible, Eric; Gludovatz, Bernd; Schmidt, Felix N.; Riedel, Christoph; Krause, Matthias; Vettorazzi, Eik; Acevedo, Claire; Hahn, Michael; Püschel, Klaus; Tang, Simon; Amling, Michael; Ritchie, Robert O.; Busse, Björn

    2016-01-01

    Bisphosphonates are a common treatment to reduce osteoporotic fractures. This treatment induces osseous structural and compositional changes accompanied by positive effects on osteoblasts and osteocytes. Here, we test the hypothesis that restored osseous cell behavior, which resembles characteristics of younger, healthy cortical bone, leads to improved bone quality. Microarchitecture and mechanical properties of young, treatment-naïve osteoporosis, and bisphosphonate-treated cases were investigated in femoral cortices. Tissue strength was measured using three-point bending. Collagen fibril-level deformation was assessed in non-traumatic and traumatic fracture states using synchrotron small-angle x-ray scattering (SAXS) at low and high strain rates. The lower modulus, strength and fibril deformation measured at low strain rates reflects susceptibility for osteoporotic low-energy fragility fractures. Independent of age, disease and treatment status, SAXS revealed reduced fibril plasticity at high strain rates, characteristic of traumatic fracture. The significantly reduced mechanical integrity in osteoporosis may originate from porosity and alterations to the intra/extrafibrillar structure, while the fibril deformation under treatment indicates improved nano-scale characteristics. In conclusion, losses in strength and fibril deformation at low strain rates correlate with the occurrence of fragility fractures in osteoporosis, while improvements in structural and mechanical properties following bisphosphonate treatment may foster resistance to fracture during physiological strain rates. PMID:26879146

  12. High Energy Gas Fracturing Test

    SciTech Connect

    Schulte, R.

    2001-02-27

    The Rocky Mountain Oilfield Testing Center (RMOTC) has recently completed two tests of a high-energy gas fracturing system being developed by Western Technologies of Crossville, Tennessee. The tests involved the use of two active wells located at the Naval Petroleum Reserve No. 3 (NPR-3), thirty-five miles north of Casper, Wyoming (See Figure 1). During the testing process the delivery and operational system was enhanced by RMOTC, Western Technologies, and commercial wireline subcontractors. RMOTC has assisted an industrial client in developing their technology for high energy gas fracturing to a commercial level. The modifications and improvements implemented during the technology testing process are instrumental in all field testing efforts at RMOTC. The importance of well selection can also be critical in demonstrating the success of the technology. To date, significant increases in well productivity have been clearly proven in well 63-TPX-10. Gross fluid production was initially raised by a factor of three. Final production rates increased by a factor of six with the use of a larger submersible pump. Well productivity (bbls of fluid per foot of drawdown) increased by a factor of 15 to 20. The above results assume that no mechanical damage has occurred to the casing or cast iron bridge plug which could allow well production from the Tensleep ''B'' sand. In the case of well 61-A-3, a six-fold increase in total fluid production was seen. Unfortunately, the increase is clouded by the water injection into the well that was necessary to have a positive fluid head on the propellant tool. No significant increase in oil production was seen. The tools which were retrieved from both 63-TPX-10 and 61-A-3 indicated a large amount of energy, similar to high gram perforating, had been expended downhole upon the formation face.

  13. Current Perspectives in High Energy Astrophysics

    NASA Technical Reports Server (NTRS)

    Ormes, Jonathan F. (Editor)

    1996-01-01

    High energy astrophysics is a space-age discipline that has taken a quantum leap forward in the 1990s. The observables are photons and particles that are unable to penetrate the atmosphere and can only be observed from space or very high altitude balloons. The lectures presented as chapters of this book are based on the results from the Compton Gamma-Ray Observatory (CGRO) and Advanced Satellite for Cosmology and Astrophysics (ASCA) missions to which the Laboratory for High Energy Astrophysics at NASA's Goddard Space Flight Center made significant hardware contributions. These missions study emissions from very hot plasmas, nuclear processes, and high energy particle interactions in space. Results to be discussed include gamma-ray beaming from active galactic nuclei (AGN), gamma-ray emission from pulsars, radioactive elements in the interstellar medium, X-ray emission from clusters of galaxies, and the progress being made to unravel the gamma-ray burst mystery. The recently launched X-ray Timing Explorer (XTE) and prospects for upcoming Astro-E and Advanced X-ray Astronomy Satellite (AXAF) missions are also discussed.

  14. Nonthermal processes around collapsed objects: High energy gamma ray sources in the radio sky

    NASA Technical Reports Server (NTRS)

    Helfand, David J.; Ruderman, Malvin; Applegate, James H.; Becker, Robert H.

    1993-01-01

    In our proposal responding to the initial Guest Observer NRA for the Compton Gamma Ray Observatory, 'Nonthermal Processes Around Collapsed Objects: High Energy Gamma Ray Sources in the Radio Sky', we stated that 'At high energies - the identity of the principal Galactic source population remains unknown' although the 'one certain source of high energy emission is young radio pulsars'. These two statements remain true, although at this writing, eighteen months after the beginning of the Compton allsky survey, much of the gamma-ray data required to greatly extend our knowledge of the Galaxy's high energy emission has been collected. The thrust of the program supported by our grant was to collect and analyze a complementary set of data on the Milky Way at radio wavelengths in order to help identify the dominant Pop 1 component of the Galaxy's gamma ray sources, and to pursue theoretical investigations on the origins and emission mechanisms of young pulsars, the one component of this population identified to date. We summarize here our accomplishments under the grant. In Section 2, we describe our VLA surveys of the Galactic Plane along with the current status of the radio source catalogs derived therefrom; unfortunately, owing to the TDRSS antenna problem and subsequent extension of the Sky Survey, we were not able to carry out a comparison with the EGRET data directly, although everything is now in place to do so as soon as it becomes available. In Section 2, we summarize our progress on the theoretical side, including the substantial completion of a dissertation on pulsar origins and work on the high energy emission mechanisms of isolated pulsars. We list the personnel supported by the grant in section 4 and provide a complete bibliography of publications supported in whole or in part by the grant in the final section.

  15. Flare physics at high energies

    NASA Technical Reports Server (NTRS)

    Ramaty, R.

    1990-01-01

    High-energy processes, involving a rich variety of accelerated particle phenomena, lie at the core of the solar flare problem. The most direct manifestation of these processes are high-energy radiations, gamma rays, hard X-rays and neutrons, as well as the accelerated particles themselves, which can be detected in interplanetary space. In the study of astrophysics from the moon, the understanding of these processes should have great importance. The inner solar system environment is strongly influenced by activity on the sun; the physics of solar flares is of great intrinsic interest; and much high-energy astrophysics can be learned from investigations of flare physics at high energies.

  16. An alternative mechanism for production of emission features in some infrared objects

    NASA Technical Reports Server (NTRS)

    Apruzese, J. P.

    1975-01-01

    Two dust-envelope models of the M supergiant VX Sgr, which exhibits a prominent emission feature at 10 microns, are presented. The models indicate that, for certain envelope sizes, the presence of the observed emission feature does not necessarily indicate that the emitting grains possess a similar feature in their emissivity profile. The mechanism which may in some cases be producing the observed emission feature is discussed.

  17. Irradiation damage from low-dose high-energy protons on mechanical properties and positron annihilation lifetimes of Fe-9Cr alloy

    NASA Astrophysics Data System (ADS)

    Xu, Q.; Fukumoto, K.; Ishi, Y.; Kuriyama, Y.; Uesugi, T.; Sato, K.; Mori, Y.; Yoshiie, T.

    2016-01-01

    Nuclear reactions in accelerator-driven systems (ADS) result in the generation of helium within the ADS materials. The amount of helium produced in this way is approximately one order of magnitude higher than that generated by nuclear fusion. As helium is well-known to induce degradation in the mechanical properties of metals, its effect on ADS materials is an important factor to assess. The results obtained in this study show that low-dose proton irradiation (11 MeV at 573 K to 9.0 × 10-4 dpa and 150 MeV at room temperature to 2.6 × 10-6 dpa) leads to a decrease in yield stress and ultimate tensile strength in a Fe-9Cr alloy. Moreover, interstitial helium and hydrogen atoms, as well as the annihilation of dislocation jogs, were identified as key factors that determine the observed softening of the alloy.

  18. High energy neutrinos from gamma-ray burst fireballs

    NASA Astrophysics Data System (ADS)

    Tamborra, Irene

    2016-05-01

    The diffuse high-energy neutrino emission from long and short gamma-ray bursts (GRBs) is studied within the fireball emission model. By requiring that the GRB high-energy neutrino counterparts follow up-to-date gamma-ray luminosity functions and redshift evolutions, we find that GRBs could contribute up to a few percents to the observed IceCube high-energy neutrino flux for sub-PeV energies, if the latter has a diffuse origin. Our findings suggest that larger exposure is mandatory to detect neutrinos from GRBs in future stacking searches.

  19. Effects of high-energy electro-pulsing treatment on microstructure, mechanical properties and corrosion behavior of Ti-6Al-4V alloy.

    PubMed

    Ye, Xiaoxin; Wang, Lingsheng; Tse, Zion T H; Tang, Guoyi; Song, Guolin

    2015-04-01

    The effect of electro-pulsing treatment (EPT) on the microstructure, mechanical properties and corrosion behavior of cold-rolled Ti-6Al-4V alloy strips was investigated in this paper. It was found that the elongation to failure of materials obtains a noticeable enhancement with increased EPT processing time while slightly sacrificing strength. Fine recrystallized grains and the relative highest elongation to failure (32.5%) appear in the 11second-EPT samples. Grain coarsening and decreased ductility were brought in with longer EPT duration time. Fracture surface analysis shows that transition from intergranular brittle facture to transgranular dimple fracture takes place with an increase in processing time of EPT. Meanwhile, corrosion behavior of titanium alloys is greatly improved with increased EPT processing time, which is presented by polarization test and surface observation with the beneficial effect of forming a protective anatase-TiO2 film on the surface of alloys. The rapid recrystallization behavior and oxide formation of the titanium alloy strip under EPTs are attributed to the enhancement of nucleation rate, atomic diffusion and oxygen migration resulting from the coupling of the thermal and athermal effects. PMID:25687017

  20. Synthesis of Nanostructured Carbides of Titanium and Vanadium from Metal Oxides and Ferroalloys Through High-energy Mechanical Milling and Heat Treatment

    SciTech Connect

    Basu, P.; Jian, P. F.; Seong, K. Y.; Seng, G. S.; Hussain, Z.; Aziz, A.; Masrom, A. K.

    2010-03-11

    Carbides of Ti and V have been synthesized directly from their oxides and ferroalloys through mechanical milling and heat treatment. The powder mixtures are milled in a planetary ball mill from 15-80 hours and subsequently heat treated at 1000-1300 deg. C for TiO{sub 2}-C mixtures, at 500-550 deg. C for V{sub 2}O{sub 5}-C mixtures and at 600-1000 deg. C for (Fe-V)-C mixtures. The milled and heat treated powders are characterized by SEM, EDAX, XRD, and BET techniques. Nanostructured TiC has been successfully synthesized under suitable processing conditions. However, carbides of vanadium is unidentified even though possibilities of V{sub 2}O{sub 5}-C reaction are indicated with an extent of induced amorphism in the powder mixture. Density, specific surface area and particle size of the milled and heat treated mixtures are correlated with heat treatment temperatures. Similar attempts are also made to synthesize vanadium carbides from industrial grade Fe-V.

  1. [Mechanism of pigment content on infrared emissivity of composite coatings].

    PubMed

    Zhang, Wei-Gang; Xu, Guo-Yue; Xu, Fei-Feng; Ding, Ru-Ya; Tan, Shu-Juan

    2012-10-01

    Polyurethane (PU)/flaky metal composite coatings were prepared by using PU and flaky metal powders as adhesives and pigments, respectively. The infrared emissivity of coatings with different metal content was measured by infrared emissometer, and the microstructure of PU/flaky metal composite coatings was observed by scanning electron microscopy. The results of infrared emissivity measurement indicate that the emissivity changes significantly with increasing metal content and presents a "U" type. The results of microstructure observation indicate that PU/flaky metal composite coatings have one-dimensional photonic structural characteristics. According to the microstructure characteristics, the optical reflection spectra of one-dimensional photonic structure in PU/flaky metal composite coatings with different metal content were simulated, and the results show that "U" type variation of emissivity with increasing metal content is derived from the blueshift of reflection peak wavelength with increasing metal content of one-dimensional photonic structure in coatings. PMID:23285860

  2. Implications of the 1400 MHz flare emission from AD Leo for the emission mechanism and flare environment

    NASA Technical Reports Server (NTRS)

    Holman, G. D.; Bookbinder, J.; Golub, L.

    1985-01-01

    High brightness temperature spikes have been observed during a radio flare on the M-dwarf flare star AD Leo (Lang et al., 1983). Their high brightness temperature (greater than 10 to the 13th K) and circular polarization indicate that a coherent radiation mechanism must be responsible for the spike emission. The underlying flare emission, which is identified with a low polarization, gradual component, was found not to be spiky to within the 200 ms time resolution of the observations. This note is concerned primarily with this nonspiky emission.

  3. Astrophysical implications of high energy neutrino limits

    NASA Astrophysics Data System (ADS)

    Becker, Julia K.; Groß, Andreas; Münich, Kirsten; Dreyer, Jens; Rhode, Wolfgang; Biermann, Peter L.

    2007-09-01

    Second generation high energy neutrino telescopes are being built to reach sensitivities of neutrino emission from galactic and extragalactic sources. Current neutrino detectors are already able to set limits which are in the range of some emission models. In particular, the Antarctic Muon and Neutrino Detection Array (AMANDA) has recently presented the so-far most restrictive limit on diffuse neutrino emission [A. Achterberg et al., Phys. Rev. D, submitted for publication, astro-ph/0705.1315.]. Stacking limits which apply to AGN point source classes rather than to single point sources [A. Achterberg, et al., IceCube Collaboration and P.L. Biermann, Astrophys. Phys. 26 (2006) 282] are given as well. In this paper, the two different types of limits will be used to draw conclusions about different emission models. An interpretation of stacking limits as diffuse limits to the emission from considered point source class is presented. The limits can for instance be used to constrain the predicted correlation of EGRET-detected diffuse emission and neutrino emission. Also, the correlation between X-ray and neutrino emission is constrained. Further results for source classes like TeV blazars and FR-II galaxies are presented. Starting from the source catalogs so-far examined for the stacking method, we discuss further potential catalogs and examine the possibilities of the second generation telescopes ICECUBE and KM3NET by comparing catalogs with respect to northern and southern hemisphere total flux.

  4. High energy neutrinos from primary cosmic rays accelerated in the cores of active galaxies

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Done, C.; Salamon, M. H.; Sommers, P.

    1991-01-01

    The spectra and high-energy neutrino fluxes are calculated from photomeson production in active galactic nuclei (AGN) such as quasars and Seyfert galaxies using recent UV and X-ray observations to define the photon fields and an accretion-disk shock-acceleration model for producing ultrahigh-energy cosmic rays in the AGN. Collectively AGN should produce the dominant isotropic neutrino background between 10 exp 4 and 10 exp 10 GeV. Measurement of this background could be critical in determining the energy-generation mechanism, evolution, and distribution of AGN. High-energy background spectra and spectra from bright AGN such as NGC4151 and 3C273 are predicted which should be observable with present detectors. High energy AGN nus should produce a sphere of stellar disruption around their cores which could explain their observed broad-line emission regions.

  5. High-energy pulsed Raman fiber laser for biological tissue coagulation

    PubMed Central

    Baac, Hyoung Won; Uribe-Patarroyo, Néstor; Bouma, Brett E.

    2014-01-01

    We demonstrate a high-energy pulsed Raman fiber laser (RFL) with an emission wavelength of 1.44 μm, corresponding to an absorption peak of water. Microsecond pulses with >20 mJ/pulse and >40 W peak power were generated, well above the threshold for tissue coagulation and ablation. Here, we focus on the optical characterization and optimization of high-energy and high-power RFLs excited by an ytterbium fiber laser, comparing three configurations that use different Raman gain fibers, but all of which were prepared with a one-side opened, free-run mode without output mirrors. We show that the free-run configuration can generate sufficiently high energy without requiring a closed cavity design. Experimental RFL characteristics corresponded well with numerical simulations. We discuss the Stokes beam generation process in our system and loss mechanisms mainly associated with fiber Bragg gratings. PMID:24664059

  6. High energy gamma ray imaging

    NASA Astrophysics Data System (ADS)

    Doherty, Michael Richard

    This thesis presents a design study into gamma ray collimation techniques for use in high energy radiation imaging devices for the nuclear industry. Such technology is required to provide information on the nature and location of isotopes within nuclear facilities that have reached the end of their useful life. The work has concentrated on the use of two different techniques, namely mechanical collimation using the Anger camera and electronic collimation using a Compton camera. The work has used computational models to evaluate the performance of such systems and thereby suggest optimal design parameters for use in prototype devices. Ray tracing models have been constructed to simulate both parallel hole and tapered bore diverging collimators. Investigations have been carried out to measure the effects on the spatial resolution of changing various design parameters of the collimators. The effects of varying the hole size, septal thickness and collimator length over a range of source to collimator distances likely to be encountered in an industrial scenario have been examined. Some new insight into the nature of the point spread function of mechanical collimators has been gained and the limitations of the conventional analytical approach to collimator evaluation have been highlighted. Modifications to the standard equations used in collimator design have subsequently been suggested. An analytical description of tapered bore collimators has been derived. Monte Carlo models have been developed to model a single scatter Compton camera. Germanium, silicon and sodium iodide have been investigated as candidates for the scattering detector in such a device. A model of a complete ring array Compton camera system has been used to evaluate performance. The data from the Monte Carlo model has been reconstructed to form images. The quality of the images generated have then been compared with images obtained from parallel hole and focusing mechanical collimators.

  7. High energy physics

    SciTech Connect

    Kernan, A.; Shen, B.C.; Ma, E.

    1997-07-01

    Hadron collider studies will focus on: (i) the search for the top quark with the newly installed D0 detector at the Fermilab Tevatron collider, (ii) the upgrade of the D0 detector to match the new main injector luminosity and (iii) R&D on silicon microstrip tracking devices for the SSC. High statistics studies of Z{sup 0} decay will continue with the OPAL detector at LEP. These studies will include a direct measurement of Z decay to neutrinos, the search for Higgs and heavy quark decays of Z. Preparations for the Large Scintillation Neutrino Detector (LSND) to measure neutrino oscillations at LAMPF will focus on data acquisition and testing of photomultiplier tubes. In the theoretical area E. Ma will concentrate on mass-generating radiative mechanisms for light quarks and leptons in renormalizable gauge field theories. J. Wudka`s program includes a detailed investigation of the magnetic-flip approach to the solar neutrino.

  8. The Anatomy of a Long Gamma-Ray Burst: A Simple Classification Scheme for the Emission Mechanism(s).

    NASA Astrophysics Data System (ADS)

    Bégué, D.; Burgess, J. Michael

    2016-03-01

    Ultra-relativistic motion and efficient conversion of kinetic energy to radiation are required by gamma-ray burst (GRB) observations, yet they are difficult to simultaneously achieve. Three leading mechanisms have been proposed to explain the observed emission emanating from GRB outflows: radiation from either relativistic internal or external shocks, or thermal emission from a photosphere. Previous works were dedicated to independently treating these three mechanisms and arguing for a sole, unique origin of the prompt emission of GRBs. In contrast, herein, we first explain why all three models are valid mechanisms and that a contribution from each of them is expected in the prompt phase. Additionally, we show that a single parameter, the dimensionless entropy of the GRB outflow, determines which mechanism contributes the most to the emission. More specifically, internal shocks dominate for low values of the dimensionless entropy, external shocks for intermediate values, and finally, photospheric emission for large values. We present a unified framework for the emission mechanisms of GRBs with easily testable predictions for each process.

  9. The anatomy of a long gamma-ray burst: a simple classification scheme for the emission mechanism(s).

    NASA Astrophysics Data System (ADS)

    Bégué, Damien; Burgess, Michael

    2016-07-01

    Ultra-relativistic motion and efficient conversion of kinetic energy to radiation are required by gamma-ray burst (GRB) observations, yet they are difficult to simultaneously achieve. Three leading mechanisms have been proposed to explain the observed emission emanating from GRB outflows: radiation from either relativistic internal or external shocks, or thermal emission from a photosphere. Previous works were mechanisms and arguing for a sole, unique origin of the prompt emission of gamma-ray bursts. In contrast, herein, we first explain why all three models are valid mechanisms and that a contribution from each of them is expected in the prompt phase. Additionally, we show that a single parameter, the dimensionless entropy of the GRB outflow, determines which mechanism contributes the most to the emission. More specifically, internal shocks dominate for low values of the dimensionless entropy, external shocks for intermediate values and finally, photospheric emission for large values. We present a unified framework for the emission mechanisms of GRBs with easily testable predictions for each process.

  10. The mechanism of light emission from statistically rough tunnel junctions

    NASA Astrophysics Data System (ADS)

    Dawson, P.; Walmsley, D. G.

    1984-04-01

    Its is found that the spectrum of the light emitted by statistically rough tunnel junctions in the range 400-700 nm correlates with the calculated damping of the fast surface plasmon polariton mode of the tunnel junction structure. It is deduced that the radiative decay of this mode is responsible for the bulk of the light emission. It is shown that the view of existing theory that emission from statistically rough junctions is mediated by the slow surface plasmon polariton mode is untenable. Our deductions firmly consolidate a suggestion due to Kroo, Szentirmay and Felszerfalvi.

  11. Experimental High Energy Neutrino Astrophysics

    SciTech Connect

    Distefano, Carla

    2005-10-12

    Neutrinos are considered promising probes for high energy astrophysics. More than four decades after deep water Cerenkov technique was proposed to detect high energy neutrinos. Two detectors of this type are successfully taking data: BAIKAL and AMANDA. They have demonstrated the feasibility of the high energy neutrino detection and have set first constraints on TeV neutrino production astrophysical models. The quest for the construction of km3 size detectors have already started: in the South Pole, the IceCube neutrino telescope is under construction; the ANTARES, NEMO and NESTOR Collaborations are working towards the installation of a neutrino telescope in the Mediterranean Sea.

  12. High-energy spectroscopic astrophysics

    NASA Astrophysics Data System (ADS)

    Güdel, Manuel; Walter, Roland

    After three decades of intense research in X-ray and gamma-ray astronomy, the time was ripe to summarize basic knowledge on X-ray and gamma-ray spectroscopy for interested students and researchers ready to become involved in new high-energy missions. This volume exposes both the scientific basics and modern methods of high-energy spectroscopic astrophysics. The emphasis is on physical principles and observing methods rather than a discussion of particular classes of high-energy objects, but many examples and new results are included in the three chapters as well.

  13. Analysis of Jovian decamteric data: Study of radio emission mechanisms

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Rosenkranz, P. W.; Arias, T. A.; Garnavich, P. N.; Hammerschlag, R.

    1986-01-01

    This research effort involved careful examination of Jovian radio emission data below 40 MHz, with emphasis on the informative observations of the Planetary Radio Astronomy experiment (PRA) on the Voyager 1 and 2 spacecraft. The work is divided into three sections, decametric arcs, decametric V bursts, and hectometric modulated spectral activity (MSA).

  14. Mechanisms governing fine particulate emissions from coal flames

    SciTech Connect

    Clark, W.D.; Chen, S.L.; Kramlich, J.C.; Newton, G.H.; Seeker, W.R. ); Samuelsen, G.S. )

    1988-11-01

    The overall objectives of this project are to provide a basic understanding of the principal processes that govern fine particulate formation in pulverized coal flames, and develop procedures to predict the levels of emission of fine particles from pulverized coal combustors. (VC)

  15. Panchromatic Observations of the Textbook GRB 110205A: Constraining Physical Mechanisms of Prompt Emission and Afterglow

    NASA Technical Reports Server (NTRS)

    Zheng, W.; Shen, R. F.; Sakamoto, T.; Beardmore, A. P.; De Pasquale, M.; Wu, X. F.; Gorosabel, J.; Urata, Y.; Sugita, S.; Zhang, B.; Pozanenko, A.; Nissinen, M.; Sahu, D. K.; Im, M.; Ukwatta, T. N.; Andreev, M.; Klunko, E.; Volnova, A.; Akerlof, C. W.; Anto, P.; Barthelmy, S. D.; Breeveld, A.; Carsenty, U.; Gehrels, N.; Sonbas, E.

    2011-01-01

    We present a comprehensive analysis of a bright, long duration (T(sub 90) approx. 257 s) GRB 110205A at redshift z = 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb and BOOTES telescopes when the GRB was still radiating in the gamma-ray band. Thanks to its long duration, nearly 200 s of observations were obtained simultaneously from optical, X-ray to gamma-ray (1 eV - 5 MeV), which makes it one of the exceptional cases to study the broadband spectral energy distribution across 6 orders of magnitude in energy during the prompt emission phase. In particular, by fitting the time resolved prompt spectra, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard GRB synchrotron emission model in the fast cooling regime. Although the prompt optical emission is brighter than the extrapolation of the best fit X/ -ray spectra, it traces the -ray light curve shape, suggesting a relation to the prompt high energy emission. The synchrotron + synchrotron self-Compton (SSC) scenario is disfavored by the data, but the models invoking a pair of internal shocks or having two emission regions can interpret the data well. Shortly after prompt emission (approx. 1100 s), a bright (R = 14.0) optical emission hump with very steep rise ( alpha approx. 5.5) was observed which we interpret as the emission from the reverse shock. It is the first time that the rising phase of a reverse shock component has been closely observed.

  16. Nuclear reactions induced by high-energy alpha particles

    NASA Technical Reports Server (NTRS)

    Shen, B. S. P.

    1974-01-01

    Experimental and theoretical studies of nuclear reactions induced by high energy protons and heavier ions are included. Fundamental data needed in the shielding, dosimetry, and radiobiology of high energy particles produced by accelerators were generated, along with data on cosmic ray interaction with matter. The mechanism of high energy nucleon-nucleus reactions is also examined, especially for light target nuclei of mass number comparable to that of biological tissue.

  17. Microstructural origins of radiation-induced changes in mechanical properties of 316 L and 304 L austenitic stainless steels irradiated with mixed spectra of high-energy protons and spallation neutrons

    NASA Astrophysics Data System (ADS)

    Sencer, B. H.; Bond, G. M.; Hamilton, M. L.; Garner, F. A.; Maloy, S. A.; Sommer, W. F.

    2001-07-01

    A number of candidate alloys were exposed to a particle flux and spectrum at Los Alamos Neutron Science Center (LANSCE) that closely match the mixed high-energy proton/neutron spectra expected in accelerator production of tritium (APT) window and blanket applications. Austenitic stainless steels 316 L and 304 L are two of these candidate alloys possessing attractive strength and corrosion resistance for APT applications. This paper describes the dose dependence of the irradiation-induced microstructural evolution of SS 316 L and 304 L in the temperature range 30-60°C and consequent changes in mechanical properties. It was observed that the microstructural evolution during irradiation was essentially identical in the two alloys, a behavior mirrored in their changes in mechanical properties. With one expection, it was possible to correlate all changes in mechanical properties with visible microstructural features. A late-term second abrupt decrease in uniform elongation was not associated with visible microstructure, but is postulated to be a consequence of large levels of retained hydrogen measured in the specimens. In spite of large amounts of both helium and hydrogen retained, approaching 1 at.% at the highest exposures, no visible cavities were formed, indicating that the gas atoms were either in solution or in subresolvable clusters.

  18. Prospects of High Energy Laboratory Astrophysics

    SciTech Connect

    Ng, J.S.T.; Chen, P.; /SLAC

    2006-09-21

    Ultra high energy cosmic rays (UHECR) have been observed but their sources and production mechanisms are yet to be understood. We envision a laboratory astrophysics program that will contribute to the understanding of cosmic accelerators with efforts to: (1) test and calibrate UHECR observational techniques, and (2) elucidate the underlying physics of cosmic acceleration through laboratory experiments and computer simulations. Innovative experiments belonging to the first category have already been done at the SLAC FFTB. Results on air fluorescence yields from the FLASH experiment are reviewed. Proposed future accelerator facilities can provided unprecedented high-energy-densities in a regime relevant to cosmic acceleration studies and accessible in a terrestrial environment for the first time. We review recent simulation studies of nonlinear plasma dynamics that could give rise to cosmic acceleration, and discuss prospects for experimental investigation of the underlying mechanisms.

  19. Engine Tune-up Service. Unit 6: Emission Control Systems. Student Guide. Automotive Mechanics Curriculum.

    ERIC Educational Resources Information Center

    Bacon, E. Miles

    This student guide is for Unit 6, Emission Control Systems, in the Engine Tune-Up Service portion of the Automotive Mechanics Curriculum. It deals with inspecting, testing, and servicing an emission control system. A companion review exercise book and posttests are available separately as CE 031 221-222. An introduction tells how this unit fits…

  20. Engine Performance (Section C: Emission Control Systems). Auto Mechanics Curriculum Guide. Module 3. Instructor's Guide.

    ERIC Educational Resources Information Center

    Rains, Larry

    This engine performance (emission control systems) module is one of a series of competency-based modules in the Missouri Auto Mechanics Curriculum Guide. Topics of this module's five units are: positive crankcase ventilation (PCV) and evaporative emission control systems; exhaust gas recirculation (EGR); air injection and catalytic converters;…

  1. MEASUREMENT OF AMMONIA EMISSIONS FROM MECHANICALLY VENTILATED POULTRY HOUSES USING MULTIPATH TUNABLE DIODE LASER SPECTROSCOPY

    EPA Science Inventory

    Ammonia emissions from mechanically ventilated poultry operations are an important environmental concern. Open Path Tunable Diode Laser Absorption Spectroscopy has emerged as a robust real-time method for gas phase measurement of ammonia concentrations in agricultural settings. ...

  2. High-Energy Traumatic Maxillofacial Injury.

    PubMed

    Christensen, Jacob; Sawatari, Yoh; Peleg, Michael

    2015-07-01

    High-energy blunt or penetrating impact leads to great variability in facial injury patterns. Although the mechanism, pattern, and distribution of forces vary, the resultant damage to hard and soft tissues requires dedicated planning and execution of debridement and reconstructive procedures. This article evaluates the initial management of patients sustaining high-energy facial impact injuries resulting in one or more comminuted or displaced facial fractures, with accompanying severe facial lacerations and/or soft tissue defects and avulsion injuries. Seventy-three patients met the criteria for high-energy traumatic injuries at Jackson Memorial/University of Miami Medical Center between 2003 and 2013 and are included in this article. Thirty-nine patients sustained one or more gunshot wounds to the face, and 34 patients were involved in high-speed motor vehicle collisions; all patients met our criteria for high-energy trauma. The treatment protocol for these injuries involves meticulous surgical exploration and assessment, aggressive debridement, early definitive reduction/fixation, and reconstruction as necessary. PMID:26114523

  3. Computational studies on the crystal structure, thermodynamic properties, detonation performance, and pyrolysis mechanism of 2,4,6,8-tetranitro-1,3,5,7-tetraazacubane as a novel high energy density material.

    PubMed

    Wang, Fang; Du, Hongchen; Zhang, Jianying; Gong, Xuedong

    2011-10-27

    Studies have suggested that octanitrocubane (ONC) is one of the most powerful non-nuclear high energy density material (HEDM) currently known. 2,4,6,8-Tetranitro-1,3,5,7-tetraazacubane (TNTAC) studied in this work may also be a novel HEDM due to its high nitrogen content and crystal density. Density functional theory and molecular mechanics methods have been employed to study the crystal structure, IR spectrum, electronic structure, thermodynamic properties, gas-phase and condensed-phase heat of formation, detonation performance, and pyrolysis mechanism of TNTAC. The TNTAC has a predicted density of about 2.12 g/cm(3), and its detonation velocity (10.42 km/s) and detonation pressure (52.82 GPa) are higher than that of ONC. The crystalline packing is P2(1)2(1)2(1), and the corresponding cell parameters are Z = 4, a = 8.87 Å, b = 8.87 Å, and c = 11.47 Å. Both the density of states of the predicted crystal and the bond dissociation energy of the molecule in gas phase show that the cage C-N bond is the trigger bond during thermolysis. The activation energy of the pyrolysis initiation reaction obtained from the B3LYP/6-311++G(2df,2p) level is 125.98 kJ/mol, which indicates that TNTAC meets the thermal stability request as an exploitable HEDM. PMID:21919441

  4. Mechanical properties of pulsed laser-deposited hydroxyapatite thin films implanted at high energy with N + and Ar + ions. Part II: nano-scratch tests with spherical tipped indenter

    NASA Astrophysics Data System (ADS)

    Pelletier, H.; Nelea, V.; Mille, P.; Muller, D.

    2004-02-01

    In this study we report a method to improve the adherence of hydroxyapatite (HA) thin films, using an ion beam implantation treatment. Crystalline HA films were grown by pulsed laser deposition technique (PLD), using an excimer KrF * laser. The films were deposited at room temperature in vacuum on Ti-5Al-2.5Fe alloy substrates previously coated with a ceramic TiN buffer layer and then annealed in ambient air at (500-600) °C. After deposition the films were implanted with N + and Ar + ions accelerated at high energy (1-1.5 MeV range) at a fixed dose of 10 16 cm -2. The intrinsic mechanical resistance and adherence to the TiN buffer layer of the implanted HA films have been evaluated by nano-scratch tests. We used for measurements a spherical indenter with a tip radius of 5 μm. Different scratch tests have been performed on implanted and unimplanted areas of films to put into evidence the effects of N + and Ar + ion implantation process on the films properties. Results show an enhancement of the dynamic mechanical properties in the implanted zones and influence of the nature of the implanted species. The best results are obtained for films implanted with nitrogen.

  5. Future of high energy physics

    SciTech Connect

    Panofsky, W.K.H.

    1984-06-01

    A rough overview is given of the expectations for the extension of high energy colliders and accelerators into the xtremely high energy range. It appears likely that the SSC or something like it will be the last gasp of the conventional method of producing high energy proton-proton collisions using synchrotron rings with superconducting magnets. It is likely that LEP will be the highest energy e+e/sup -/ colliding beam storage ring built. The future beyond that depends on the successful demonstrations of new technologies. The linear collider offers hope in this respect for some extension in energy for electrons, and maybe even for protons, but is too early to judge whether, by how much, or when such an extension will indeed take place.

  6. Mechanisms governing fine particulate emissions from coal flames. Final report

    SciTech Connect

    Newton, G.H.; Schieber, C.; Socha, R.G.; Kramlich, J.C.

    1990-04-01

    The primary objective of this program was to provide a basic understanding of the principal processes that govern the formation of particulate matter in the 0.5--10 {mu}m size range in pulverized coal flames. The mechanism that produces ash particles in this size range is not clear. Particle sizes smaller than the 0.5--10 {mu}m size range are generally accepted to result from a vaporization/condensation mechanism while particles larger than this size result from the coalescence of ash in coal particles which may breakup as they burn. This program combined experimental and theoretical studies to understand the mechanisms which control the production of ash in the 0.5--10 {mu}m size range. (VC)

  7. Mechanisms governing fine particulate emissions from coal flames

    SciTech Connect

    Newton, G.H.; Schieber, C.; Socha, R.G.; Kramlich, J.C.

    1990-04-01

    The primary objective of this program was to provide a basic understanding of the principal processes that govern the formation of particulate matter in the 0.5--10 {mu}m size range in pulverized coal flames. The mechanism that produces ash particles in this size range is not clear. Particle sizes smaller than the 0.5--10 {mu}m size range are generally accepted to result from a vaporization/condensation mechanism while particles larger than this size result from the coalescence of ash in coal particles which may breakup as they burn. This program combined experimental and theoretical studies to understand the mechanisms which control the production of ash in the 0.5--10 {mu}m size range. (VC)

  8. Solvatochromism Unravels the Emission Mechanism of Carbon Nanodots.

    PubMed

    Sciortino, Alice; Marino, Emanuele; Dam, Bart van; Schall, Peter; Cannas, Marco; Messina, Fabrizio

    2016-09-01

    High quantum yield, photoluminescence tunability, and sensitivity to the environment are hallmarks that make carbon nanodots interesting for fundamental research and applications. Yet, the underlying electronic transitions behind their bright photoluminescence are strongly debated. Despite carbon-dot interactions with their environment should provide valuable insight into the emitting transitions, they have hardly been studied. Here, we investigate these interactions in a wide range of solvents to elucidate the nature of the electronic transitions. We find remarkable and systematic dependence of the emission energy and kinetics on the characteristics of the solvent, with strong response of the photoexcited dots to hydrogen bonding. These findings suggest that the fluorescence originates from the radiative recombination of a photoexcited electron migrated to surface groups with holes left in the valence band of the crystalline core. Furthermore, the results demonstrate the fluorescence tunability to inherently derive from dot-to-dot polydispersity, independent of solvent interactions. PMID:27525451

  9. High Energy Astrophysics Program (HEAP)

    NASA Technical Reports Server (NTRS)

    Angelini, Lorella; Corcoran, Michael; Drake, Stephen; McGlynn, Thomas A.; Snowden, Stephen; Mukai, Koji; Cannizzo, John; Lochner, James; Rots, Arnold; Christian, Eric; Barthelmy, Scott; Palmer, David; Mitchell, John; Esposito, Joseph; Sreekumar, P.; Hua, Xin-Min; Mandzhavidze, Natalie; Chan, Kai-Wing; Soong, Yang; Barrett, Paul

    1998-01-01

    This report reviews activities performed by the members of the USRA contract team during the 6 months of the reporting period and projected activities during the coming 6 months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in astrophysics. Supported missions include advanced Satellite for Cosmology and Astrophysics (ASCA), X-Ray Timing Experiment (XTE), X-Ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science Archive Research Center (HEASARC) and others.

  10. High Energy Astrophysics Program (HEAP)

    NASA Technical Reports Server (NTRS)

    Angelini, L.; Holdridge, David V.; Norris, J. (Technical Monitor)

    1998-01-01

    This report reviews activities performed by members of the USRA contract team during the six months of the reporting period and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA), X-ray Timing Experiment (XTE), X-ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science Archive Research Center (HEASARC), and others.

  11. Comparison of reduced chemical kinetic mechanisms for pollutant emissions predictions in gas turbines

    SciTech Connect

    Hamer, A.J.; Roby, R.J.; Klassen, M.S.

    1998-07-01

    Predicted flow, temperature, and emissions (CO and NO) concentration fields are presented for an axi-symmetric, swirl-stabilized gas turbine combustor operating at approximately 10 atmospheres. Flow field and emissions predictions were obtained by incorporating four different global kinetics mechanisms into the commercially available STAR{asterisk}CD CFD code. Two of these global reaction mechanisms were developed specifically for lean-premixed gas turbine combustion from the GRI and Miller-Bowman full reaction mechanisms. The other global mechanisms for hydrocarbon oxidation utilized in this study were initially developed for more general usage, but are commonly used in gas turbine applications. The latter mechanisms did not specifically include reactions for NO formation. NO formation was included in these mechanisms through incorporation of two reactions developed from the recently released GRI mechanism. Comparison between integrated exit plant emissions (NO and CO) predictions and laboratory measurements showed varied degrees of agreement for the different mechanisms. In all cases, the trend in NO exhaust emissions with change in operating condition is well predicted. However, the magnitudes of the NO emissions are reasonably predicted only for leanest cases investigated with significant overprediction found as the equivalence ratio approached 0.8 (which was slightly beyond the intended range of the reduced mechanisms). On the other hand, the predicted CO emissions showed significant variation for the different mechanisms. The high CO values predicted by the model were primarily due to quenching of the CO reaction by liner cooing air at the wall. Possible explanations for the discrepancies include current limitations of the model and measurement errors. The current work shows the impact that the choice of reduced global mechanism can have on predictions of flame location, size and emissions. Such a model can be a valuable tool for designers by providing

  12. A simplified reaction mechanism for prediction of NO(x) emissions in the combustion of hydrocarbons

    NASA Technical Reports Server (NTRS)

    Kundu, K. P.; Deur, J. M.

    1992-01-01

    A simplified reaction mechanism is developed for the prediction of NO(x) in hydrocarbon combustion. The mechanism uses fewer reacting species and reaction steps than the detailed mechanisms available in the literature and therefore takes less computer time when used in CFD calculations. The mechanism has been used to calculate NO(x) emissions in the combustion of propane. With slight modifications, the same mechanism can be used to calculate NO(x) in the combustion of other hydrocarbons. Results obtained with the simplified reaction are compared with experimental results and results obtained with a detailed kinetic mechanism.

  13. Extraterrestrial high energy neutrino fluxes

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1979-01-01

    Using the most recent cosmic ray spectra up to 2x10 to the 20th power eV, production spectra of high energy neutrinos from cosmic ray interactions with interstellar gas and extragalactic interactions of ultrahigh energy cosmic rays with 3K universal background photons are presented and discussed. Estimates of the fluxes from cosmic diffuse sources and the nearby quasar 3C273 are made using the generic relationship between secondary neutrinos and gammas and using recent gamma ray satellite data. These gamma ray data provide important upper limits on cosmological neutrinos. Quantitative estimates of the observability of high energy neutrinos from the inner galaxy and 3C273 above atmospheric background for a DUMAND type detector are discussed in the context of the Weinberg-Salam model with sq sin theta omega = 0.2 and including the atmospheric background from the decay of charmed mesons. Constraints on cosmological high energy neutrino production models are also discussed. It appears that important high energy neutrino astronomy may be possible with DUMAND, but very long observing times are required.

  14. Mechanism of Electron Emission from Al(100) Bombarded by Slow Li{sup +} Ions

    SciTech Connect

    Yarmoff, J.A.; Liu, T.D.; Qiu, S.R.; Sroubek, Z.

    1998-03-01

    Emission of electrons from Al(100) during bombardment by 50{endash}520eV Li{sup +} ions was measured as a function of incident ion energy and direction. The process was modeled by a surface electron-hole pair excitation mechanism and was quantified with a one-electron parametric theory. This is a previously unidentified mechanism which is characterized by a strong dependence on the energy and angle of incidence of the primary particle. Good agreement between the experimental data and theory is found, which indicates that this mechanism is indeed responsible for electron emission during Li-Ai collisions. {copyright} {ital 1998} {ital The American Physical Society}

  15. Preliminary Breakdown: Physical Mechanisms and Potential for Energetic Emissions

    NASA Astrophysics Data System (ADS)

    Petersen, D.; Beasley, W. H.

    2014-12-01

    Observations and analysis of the preliminary breakdown phase of virgin negative cloud-to-ground (-CG) lightning strokes will be presented. Of primary interest are the physical processes responsible for the fast electric field "characteristic" pulses that are often observed during this phase. The pulse widths of characteristic pulses are shown to occur as a superposed bimodal distribution, with the short and long modes having characteristic timescales on the order of 1 microsecond and 10 microseconds, respectively. Analysis of these pulses is based on comparison with laboratory observations of long spark discharge processes and with recently acquired high-speed video observations of a single -CG event. It will be argued that the fast electric field bimodal distribution is the result of conventional discharge processes operating in an extensive strong ambient electric field environment. An important related topic will also be discussed, where it will be argued that preliminary breakdown discharges are capable of generating energetic electrons and may therefore seed relativistic electron avalanches that go on to produce pulsed energetic photon emissions.

  16. On the Origin of Ultra High Energy Cosmic Rays

    SciTech Connect

    Fowler, T; Colgate, S; Li, H

    2009-07-01

    Turbulence-driven plasma accelerators produced by magnetized accretion disks around black holes are proposed as the mechanism mainly responsible for observed cosmic ray protons with ultra high energies 10{sup 19}-10{sup 21} eV. The magnetized disk produces a voltage comparable to these cosmic ray energies. Here we present a Poynting model in which this voltage provides all of the energy to create the jet-like structures observed to be ejected from accretion disks, and this voltage also accelerates ions to high energies at the top of the expanding structure. Since the inductive electric field E = -v x B driving expansion has no component parallel to the magnetic field B, ion acceleration requires plasma wave generation - either a coherent wave accelerator as recently proposed, or instability-driven turbulence. We find that turbulence can tap the full inductive voltage as a quasi-steady accelerator, and even higher energies are produced by transient events on this structure. We find that both MHD modes due to the current and ion diffusion due to kinetic instability caused by the non-Maxwellian ion distribution contribute to acceleration. We apply our results to extragalactic giant radiolobes, whose synchrotron emissions serve to calibrate the model, and we discuss extrapolating to other astrophysical structures. Approximate calculations of the cosmic ray intensity and energy spectrum are in rough agreement with data and serve to motivate more extensive MHD and kinetic simulations of turbulence that could provide more accurate cosmic ray and synchrotron spectra to be compared with observations. A distinctive difference from previous models is that the cosmic ray and synchrotron emissions arise from different parts of the magnetic structure, thus providing a signature for the model.

  17. Evaluation of mechanical behavior of soft tissue by means of random laser emission.

    PubMed

    Briones-Herrera, J C; Cuando-Espitia, N; Sánchez-Arévalo, F M; Hernández-Cordero, J

    2013-10-01

    We demonstrate the use of random laser emission for mechanical testing of bovine pericardium. An apparatus designed for tensile tests of soft and thin materials, incorporating optical and mechanical devices, allows for obtaining the mechanical behavior of the tissue samples. Using both, digital image correlation (DIC) and random laser emission analysis, the apparatus provides information regarding the response of the bovine pericardium under different stress levels. Our results show that changes in the spectral features of the random laser correlate well to the mechanical response obtained with conventional uniaxial tensile analysis coupled with DIC. Furthermore, parameters such as the shear and Young moduli are consistent with values reported previously and obtained with other techniques. Changes at the microstructural level of the tissue may thus be evaluated through spectral analysis of the random laser emission from biological samples. PMID:24182135

  18. Evaluation of mechanical behavior of soft tissue by means of random laser emission

    NASA Astrophysics Data System (ADS)

    Briones-Herrera, J. C.; Cuando-Espitia, N.; Sánchez-Arévalo, F. M.; Hernández-Cordero, J.

    2013-10-01

    We demonstrate the use of random laser emission for mechanical testing of bovine pericardium. An apparatus designed for tensile tests of soft and thin materials, incorporating optical and mechanical devices, allows for obtaining the mechanical behavior of the tissue samples. Using both, digital image correlation (DIC) and random laser emission analysis, the apparatus provides information regarding the response of the bovine pericardium under different stress levels. Our results show that changes in the spectral features of the random laser correlate well to the mechanical response obtained with conventional uniaxial tensile analysis coupled with DIC. Furthermore, parameters such as the shear and Young moduli are consistent with values reported previously and obtained with other techniques. Changes at the microstructural level of the tissue may thus be evaluated through spectral analysis of the random laser emission from biological samples.

  19. Cross sections for proton induced high energy γ -ray emission (PIGE) in reaction 19 F(p, αγ)16 O at incident proton energies between 1.5 and 4 MeV

    NASA Astrophysics Data System (ADS)

    Cabanelas, P.; Cruz, J.; Fonseca, M.; Henriques, A.; Lourenço, F.; Luís, H.; Machado, J.; Pires Ribeiro, J.; Sánchez-Benítez, A. M.; Teubig, P.; Velho, P.; Zarza-Moreno, M.; Galaviz, D.; Jesus, A. P.

    2016-08-01

    We have studied the high energy gamma-rays produced in the reaction 19 F(p, αγ)16 O for incident proton energies from 1.5 to 4.0 MeV over NaF/Ag and CaF2/Ag thin targets in two different sets of data. Gamma-rays were detected with a High Purity Ge detector with an angle of 130° with respect to the beam axis. The cross-sections for the high energy gamma-rays of 6.129, 6.915 and 7.115 MeV have been measured for the whole group between 5 and 7.2 MeV with accuracy better than 10%. A new energy range was covered and more points are included in the cross-sections data base expanding the existing set of data. Results are in agreement with previous measurements in similar conditions.

  20. Isocyanate emission from PUR adhesives: influence of temperature, monomer content, and curing mechanism.

    PubMed

    Wirts, Martin; Salthammer, Tunga

    2002-04-15

    The isocyanate emission potential of polyurethane (PUR) adhesives was evaluated by measuring the area-specific emission rate (SERa;microg m(-2) h(-1)) in a laboratory emission test chamber. The chamber was constructed for the analysis of reactive substances allowing quantitative trapping of all isocyanate monomers emitted from the substrate. Isocyanates were analyzed as their 1-(2-pyridyl)piperazine derivatives by HPLC with fluorescence and UV detection. The influence of temperature, the content of the diisocyanate in the resin, and the system pressure were investigated. These parameter studies gave evidence thatthe diisocyanate emission from the resins is a gas-phase-limited mass transfer. The overall mass-transfer coefficient (beta = Ddelta(-1)) was calculated for HDI and MDI. From the temperature dependence of emission rates, the enthalpies of evaporation for 2,4'-MDI, 4,4'-MDI, and HDI from their resins were determined. The influence of monomer content on SERa followed Henry's and Raoult's laws in the cases of HDI and MDI, respectively, allowing the prediction of emission rates proportional to diisocyanate content. Therefore, from simple parameters such as application temperature and monomer content, isocyanate emission rates can be predicted. Additionally, MDI emission from curing PUR adhesives was studied. These results elucidate the influence of monomer reactivity and curing mechanism on the decrease of MDI emission with time. PMID:11993883

  1. Microwave emission from lead zirconate titanate induced by impulsive mechanical load

    NASA Astrophysics Data System (ADS)

    Aman, A.; Majcherek, S.; Hirsch, S.; Schmidt, B.

    2015-10-01

    This paper focuses on microwave emission from Lead zirconate titanate Pb [ZrxTi1-x] O3 (PZT) induced by mechanical stressing. The mechanical stress was initiated by impact of a sharp tungsten indenter on the upper surface of PZT ceramic. The sequences of microwave and current impulses, which flew from indenter to electric ground, were detected simultaneously. The voltage between the upper and lower surface of ceramic was measured to obtain the behavior of mechanical force acting on ceramic during the impact. It was found that the amplitude, form, and frequency of measured microwave impulses were different by compression and restitution phase of impact. Two different mechanisms of electron emission, responsible for microwave impulse generation, were proposed based on the dissimilar impulse behavior. The field emission from tungsten indenter is dominant during compression, whereas ferroemission dominates during restitution phase. Indeed, it was observed that the direction of the current flow, i.e., sign of current impulses is changed by transitions from compression to restitution phase of impact. The observed dissimilar behavior of microwave impulses, caused by increasing and decreasing applied force, can be used to calculate the contact time and behavior of mechanical force during mechanical impact on ceramic surface. It is shown that the generation of microwave impulses exhibits high reproducibility, impulse intensity, a low damping factor, and high mechanical failure resistance. Based on these microwave emission properties of PZT, the development of new type of stress sensor with spatial resolution of few microns becomes possible.

  2. Observations of high-energy radiation during thunderstorms at Tien-Shan

    NASA Astrophysics Data System (ADS)

    Gurevich, A. V.; Almenova, A. M.; Antonova, V. P.; Chubenko, A. P.; Karashtin, A. N.; Kryakunova, O. N.; Lutsenko, V. Yu.; Mitko, G. G.; Ptitsyn, M. O.; Piscal, V. V.; Ryabov, V. A.; Salikhov, N. M.; Sadykov, T. Kh.; Shepetov, A. L.; Shlyugaev, Yu. V.; Thu, W. M.; Vil'danova, L. I.; Zastrozhnova, N. N.; Zybin, K. P.

    2016-07-01

    Energetic radiation during thunderstorms is studied. The possibility to identify the high-energy lightning emission in the 10 s monitoring mode is demonstrated. Simultaneous measurements of gamma-ray emission, high-energy electrons, and neutron radiation in the triggering mode are fulfilled. Energy spectra of gamma emission and electrons are obtained. The intensity both of electrons and gamma rays in lightning discharge prevail the background emission by 1.5 to 2 orders of magnitude.

  3. Detector for high-energy photon backscatter

    NASA Astrophysics Data System (ADS)

    Silver, Michael D.; Erker, Joseph W.; Duncan, Michael Z.; Hartford, Thomas J.; Sivers, E. A.; Hopkinson, James F.

    1993-12-01

    High energy photon backscatter uses pair production to probe deep beneath surfaces with single side accessibility or to image thick, radiographically opaque objects. At the higher photon energies needed to penetrate thick and/or highly attenuating objects, Compton backscatter becomes strongly forward peaked with relatively little backscatter flux. Furthermore, the downward energy shift of the backscattered photon makes it more susceptible to attenuation on its outbound path. Above 1.022 MeV, pair production is possible; at about 10 MeV, pari production crosses over Compton scatter as the dominant x-ray interaction mechanism. The backscattered photons can be hard x rays from the bremsstrahlung of the electrons and positrons or 0.511 MeV photons from the annihilation of the positron. Monte Carlo computer simulations of such a backscatter system were done to characterize the output signals and to optimize a high energy detector design. This paper touches on the physics of high energy backscatter imaging and describes at some length the detector design for tomographic and radiographic imaging.

  4. A high energy physics perspective

    SciTech Connect

    Marciano, W.J.

    1997-01-13

    The status of the Standard model and role of symmetry in its development are reviewed. Some outstanding problems are surveyed and possible solutions in the form of additional {open_quotes}Hidden Symmetries {close_quotes} are discussed. Experimental approaches to uncover {open_quotes}New Physics{close_quotes} associated with those symmetries are described with emphasis on high energy colliders. An outlook for the future is given.

  5. Cosmology for high energy physicists

    SciTech Connect

    Albrecht, A.

    1987-11-01

    The standard big bang model of cosmology is presented. Although not perfect, its many successes make it a good starting point for most discussions of cosmology. Places are indicated where well understood laboratory physics is incorporated into the big bang, leading to successful predictions. Much less established aspects of high energy physics and some of the new ideas they have introduced into the field of cosmology are discussed, such as string theory, inflation and monopoles. 49 refs., 5 figs.

  6. High energy gamma ray astronomy

    NASA Technical Reports Server (NTRS)

    Fichtel, Carl E.

    1987-01-01

    High energy gamma ray astronomy has evolved with the space age. Nonexistent twenty-five years ago, there is now a general sketch of the gamma ray sky which should develop into a detailed picture with the results expected to be forthcoming over the next decade. The galactic plane is the dominant feature of the gamma ray sky, the longitude and latitude distribution being generally correlated with galactic structural features including the spiral arms. Two molecular clouds were already seen. Two of the three strongest gamma ray sources are pulsars. The highly variable X-ray source Cygnus X-3 was seen at one time, but not another in the 100 MeV region, and it was also observed at very high energies. Beyond the Milky Way Galaxy, there is seen a diffuse radiation, whose origin remains uncertain, as well as at least one quasar, 3C 273. Looking to the future, the satellite opportunities for high energy gamma ray astronomy in the near term are the GAMMA-I planned to be launched in late 1987 and the Gamma Ray Observatory, scheduled for launch in 1990. The Gamma Ray Observatory will carry a total of four instruments covering the entire energy range from 30,000 eV to 3 x 10 to the 10th eV with over an order of magnitude increase in sensitivity relative to previous satellite instruments.

  7. High energy electron positron physics

    SciTech Connect

    Ali, A.; Soding, P.

    1987-01-01

    With the termination of the physics program at PETRA in a year from now, and with the start of TRISTAN and the SLC and later LEP, an era of e/sup +/e/sup -/ physics will come to an end and a new one begins. The field is changing from a field of a few specialists, to becoming one of the mainstream efforts of the high energy community. It seems appropriate at this moment to summarize what has been learned over the past years, in a way more useful to any high energy physicist in particular to newcomers in the e/sup +/e/sup -/ field. This is the purpose of the book. This book should be used as a reference for future workers in the field of e/sup +/e/sup -/ interactions. It includes the most relevant data, parametrizations, theoretical background, and a chapter on detectors. Contents: Foreword; Detectors for High Energy e/sup +/e/sup -/ Physics; Lepton Pair Production and Electroweak Parameters; Hadron Production, Strong and Electroweak Properties; tau Physics; Recent Results on the Charm Sector; Bottom Physics; Lifetime Measurements of tau, Charmed and Beauty Hadrons; UPSILON Spectroscopy; Hadronic Decays of the UPSILON; Quark and Gluon Fragmentation in the e/sup +/e/sup -/ Continuum; Jet Production and QCD; Two Photon Physics; Search for New Particles.

  8. Tests and prospects of new physics at very high energy. Beyond the standard basic principles, and beyond conventional matter and space-time. On the possible origin of Quantum Mechanics.

    NASA Astrophysics Data System (ADS)

    Gonzalez-Mestres, Luis

    2015-05-01

    Recent results and announcements by Planck and BICEP2 have led to important controversies in the fields of Cosmology and Particle Physics. As new ideas and alternative approaches can since then more easily emerge, the link between the Mathematical Physics aspects of theories and the interpretation of experimental results becomes more direct. This evolution is also relevant for Particle Physics experiments at very high energy, where the interpretation of data on the highest-energy cosmic rays remains a major theoretical and phenomenological challenge. Alternative particle physics and cosmology can raise fundamental questions such as that of the structure of vacuum and space-time. In particular, the simplified description of the physical vacuum contained in standard quantum field theory does not necessarily correspond to reality at a deeper level, and similarly for the relativistic space-time based on four real variables. In a more general approach, the definition itself of vacuum can be a difficult task. The spinorial space-time (SST) we suggested in 1996-97 automatically incorporates a local privileged space direction (PSD) for each comoving observer, possibly leading to a locally anisotropic vacuum structure. As the existence of the PSD may have been confirmed by Planck, and a possible discovery of primordial B-modes in the polarization of the cosmic microwave background radiation (CMB) may turn out to contain new evidence for the SST, we explore other possible implications of this approach to space-time. The SST structure can naturally be at the origin of Quantum Mechanics at distance scales larger than the fundamental one if standard particles are dealt with as vacuum excitations. We also discuss possible implications of our lack of knowledge of the structure of vacuum, as well as related theoretical, phenomenological and cosmological uncertainties. Pre-Big Bang scenarios and new ultimate constituents of matter (including superbradyons) are crucial open subjects

  9. Features of >130 Gamma-Ray Bursts at high energy: towards the 2nd Fermi LAT GRB catalog

    NASA Astrophysics Data System (ADS)

    Vianello, Giacomo; Omodei, Nicola; Fermi LAT Collaboration

    2016-01-01

    The high-energy emission from Gamma-Ray Bursts is a formidable probe for extreme physics, calling for highly relativistic sources with very large Lorentz factors. Despite the advancements prompted by observations from the Fermi Large Area Telescope and the Fermi Gamma-Ray Burst Monitor, as well as other observatories, many questions remain open, especially on radiative processes and mechanisms. We present here the most extensive search for GRBs at high energies performed so far, featuring a detection efficiency more than 50% better than previous works, and returning more than 130 detections. With this sample size, much larger than the 35 detections presented in the first Fermi/LAT GRB catalog, we are able to assess the characteristics of the population of GRBs at high energy with unprecedented sensitivity. We will review the preliminary results of this work, as well as their interpretation.

  10. Microbial mechanisms to reduce the uncertainties in the CH4 emissions from global rice fields

    NASA Astrophysics Data System (ADS)

    Kamaljit, K.; Tian, H.; Ren, W.; Yang, J.

    2013-12-01

    In terrestrial ecosystems, methane (CH4) uptake or emission represents the net balance between activities of different microbial organisms including anaerobic Methanogens that produce CH4 and Methanotrophs which oxidize CH4 in the aerobic environments. In this way, anaerobic soil environments such as rice fields are major source of terrestrial CH4 emissions. However, large uncertainties in the CH4 emission estimates have been reported from rice fields. The bottom-up and top-down methods showed a wide range of CH4 emissions estimations ranging from 25 to 300 Tg yr-1 from rice fields. The major reason for uncertainties in the CH4 emissions includes the water management that alters the balance of Methanogens and Methanotrophs in the rice fields. Two kinds of water management practices are followed including continuous flooding (CF) which refers to the continuous submergence as well as alternate wetting and drying (AWD) in which the rice fields are drained for several days during the growing season. The AWD provides aeration stress on Methanogens resulting in lower CH4 emissions than CF water management followed in the rice fields. A single aeration during growing season may significantly reduce the CH4 emission from the rice fields. Currently, most of the models structures assume that Methanogens become active once the soil moisture content is raised to saturation. However, several laboratory scale studies have indicated that following aeration the Methanogens don't become fully functional immediately even if the soil moisture content is raised to saturation. In this study, we integrated the aeration stress mechanisms on the Methanogens in the Dynamic Land Ecosystem Model (DLEM). The improved version of DLEM was used to conduct uncertainty analysis on global CH4 emission estimation following CF and AWD water management in the rice fields. Results of this study have shown that inclusion of the aeration stress mechanism on Methanogens in the modeling framework has

  11. Self-consistent particle-in-cell simulations of fundamental and harmonic radio plasma emission mechanisms

    NASA Astrophysics Data System (ADS)

    Tsiklauri, D.; Thurgood, J. O.

    2015-12-01

    first co-author Jonathan O. Thurgood (QMUL) The simulation of three-wave interaction based plasma emission, an underlying mechanism for type III solar radio bursts, is a challenging task requiring fully-kinetic, multi-dimensional models. This paper aims to resolve a contradiction in past attempts, whereby some authors report that no such processes occur and others draw conflicting conclusions, by using 2D, fully kinetic, particle-in-cell simulations of relaxing electron beams. Here we present the results of particle-in-cell simulations which for different physical parameters permit or prohibit the plasma emission. We show that the possibility of plasma emission is contingent upon the frequency of the initial electrostatic waves generated by the bump-in-tail instability, and that these waves may be prohibited from participating in the necessary three-wave interactions due to the frequency beat requirements. We caution against simulating astrophysical radio bursts using unrealistically dense beams (a common approach which reduces run time), as the resulting non-Langmuir characteristics of the initial wave modes significantly suppresses the emission. Comparison of our results indicates that, contrary to the suggestions of previous authors, a plasma emission mechanism based on two counter-propagating beams is unnecessary in astrophysical context. Finally, we also consider the action of the Weibel instability, which generates an electromagnetic beam mode. As this provides a stronger contribution to electromagnetic energy than the emission, we stress that evidence of plasma emission in simulations must disentangle the two contributions and not simply interpret changes in total electromagnetic energy as the evidence of plasma emission. In summary, we present the first self-consistent demonstration of fundamental and harmonic plasma emission from a single-beam system via fully kinetic numerical simulation. Pre-print can be found at http://astro.qmul.ac.uk/~tsiklauri/jtdt1

  12. Extreme Transients in the High Energy Universe

    NASA Technical Reports Server (NTRS)

    Kouveliotou, Chryssa

    2013-01-01

    The High Energy Universe is rich in diverse populations of objects spanning the entire cosmological (time)scale, from our own present-day Milky Way to the re-ionization epoch. Several of these are associated with extreme conditions irreproducible in laboratories on Earth. Their study thus sheds light on the behavior of matter under extreme conditions, such as super-strong magnetic fields (in excess of 10^14 G), high gravitational potentials (e.g., Super Massive Black Holes), very energetic collimated explosions resulting in relativistic jet flows (e.g., Gamma Ray Bursts, exceeding 10^53 ergs). In the last thirty years, my work has been mostly focused on two apparently different but potentially linked populations of such transients: magnetars (highly magnetized neutron stars) and Gamma Ray Bursts (strongly beamed emission from relativistic jets), two populations that constitute unique astrophysical laboratories, while also giving us the tools to probe matter conditions in the Universe to redshifts beyond z=10, when the first stars and galaxies were assembled. I did not make this journey alone I have either led or participated in several international collaborations studying these phenomena in multi-wavelength observations; solitary perfection is not sufficient anymore in the world of High Energy Astrophysics. I will describe this journey, present crucial observational breakthroughs, discuss key results and muse on the future of this field.

  13. Acoustic Emission as a Tool for Exploring Deformation Mechanisms in Magnesium and Its Alloys In Situ

    NASA Astrophysics Data System (ADS)

    Vinogradov, Alexei; Máthis, Kristian

    2016-06-01

    Structural performance of magnesium alloys depends strongly on specific deformation mechanisms operating during mechanical loading. Therefore, in situ monitoring of the acting mechanisms is a key to performance tailoring. We review the capacity of the advanced acoustic emission (AE) technique to understand the interplay between two primary deformation mechanisms—dislocation slip and twinning—in real time scale. Details of relative contributions of dislocation slip and deformation twinning to the mechanical response of pure Mg and Mg-Al alloy are discussed in view of AE results obtained with the aid of recently proposed spectral and signal categorization algorithms in conjunction with with neutron diffraction data.

  14. High Energy Neutrinos from the Fermi Bubbles

    SciTech Connect

    Lunardini, Cecilia; Razzaque, Soebur

    2012-06-01

    Recently the Fermi-LAT data have revealed two gamma-ray emitting bubble-shaped structures at the Galactic center. If the observed gamma rays have hadronic origin (collisions of accelerated protons), the bubbles must emit high energy neutrinos as well. This new, Galactic, neutrino flux should trace the gamma-ray emission in spectrum and spatial extent. Its highest energy part, above 20–50 TeV, is observable at a kilometer-scale detector in the northern hemisphere, such as the planned KM3NeT, while interesting constraints on it could be obtained by the IceCube Neutrino Observatory at the South Pole. The detection or exclusion of neutrinos from the Fermi bubbles will discriminate between hadronic and leptonic models, thus bringing unique information on the still mysterious origin of these objects and on the time scale of their formation.

  15. Modelling high-energy pulsar light curves from first principles

    NASA Astrophysics Data System (ADS)

    Cerutti, Benoît; Philippov, Alexander A.; Spitkovsky, Anatoly

    2016-04-01

    Current models of gamma-ray light curves in pulsars suffer from large uncertainties on the precise location of particle acceleration and radiation. Here, we present an attempt to alleviate these difficulties by solving for the electromagnetic structure of the oblique magnetosphere, particle acceleration, and the emission of radiation self-consistently, using 3D spherical particle-in-cell simulations. We find that the low-energy radiation is synchro-curvature radiation from the polar-cap regions within the light cylinder. In contrast, the high-energy emission is synchrotron radiation that originates exclusively from the Y-point and the equatorial current sheet where relativistic magnetic reconnection accelerates particles. In most cases, synthetic high-energy light curves contain two peaks that form when the current sheet sweeps across the observer's line of sight. We find clear evidence of caustics in the emission pattern from the current sheet. High-obliquity solutions can present up to two additional secondary peaks from energetic particles in the wind region accelerated by the reconnection-induced flow near the current sheet. The high-energy radiative efficiency depends sensitively on the viewing angle, and decreases with increasing pulsar inclination. The high-energy emission is concentrated in the equatorial regions where most of the pulsar spin-down is released and dissipated. These results have important implications for the interpretation of gamma-ray pulsar data.

  16. HIGH-ENERGY NEUTRINO AND GAMMA-RAY TRANSIENTS FROM TRANS-RELATIVISTIC SUPERNOVA SHOCK BREAKOUTS

    SciTech Connect

    Kashiyama, Kazumi; Gao, Shan; Meszaros, Peter; Murase, Kohta; Horiuchi, Shunsaku

    2013-05-20

    Trans-relativistic shocks that accompany some supernovae (SNe) produce X-ray burst emissions as they break out in the dense circumstellar medium around the progenitors. This phenomenon is sometimes associated with peculiar low-luminosity gamma-ray bursts (LL GRBs). Here, we investigate the high-energy neutrino and gamma-ray counterparts of such a class of SNe. Just beyond the shock breakout radius, particle acceleration in the collisionless shock starts to operate in the presence of breakout photons. We show that protons may be accelerated to sufficiently high energies and produce high-energy neutrinos and gamma rays via the photomeson interaction. These neutrinos and gamma rays may be detectable from {approx}< 10 Mpc away by IceCube/KM3Net as multi-TeV transients almost simultaneously with the X-ray breakout, and even from {approx}< 100 Mpc away with follow-up observations by the Cherenkov Telescope Array using a wide-field sky monitor like Swift as a trigger. A statistical technique using a stacking approach could also be possible for the detection, with the aid of the SN optical/infrared counterparts. Such multi-messenger observations offer the possibility to probe the transition of trans-relativistic shocks from radiation-mediated to collisionless ones, and would also constrain the mechanisms of particle acceleration and emission in LL GRBs.

  17. Odour emission factors for the prediction of odour emissions from plants for the mechanical and biological treatment of MSW

    NASA Astrophysics Data System (ADS)

    Sironi, Selena; Capelli, Laura; Céntola, Paolo; Del Rosso, Renato; Il Grande, Massimiliano

    In this study, the results of odour concentration measurements sampled from the principal odour sources of 40 dimensionally different and representative Italian waste mechanical and biological treatment (MBT) plants are presented. Experimental data are then used to estimate the odour emission factors (OEFs) relevant to single-process steps. An OEF is a representative value that relates the quantity of odour released to the atmosphere to a specific activity index, which may be for example the waste treatment capacity, the gross weight production, the site surface or a time unit. In this study, the OEFs were calculated as a function of the plant capacity, and expressed in ou E t -1, because of the existence of a proportionality between plant capacity and odour emissions. The results show that the major odour source of a waste MBT plant is represented by the aerobic biological treatment (with an OEF equal to 1.40×10 8 ou E t -1). In general, the OEFs calculated according to this approach represent a model for a rough prediction of odour emissions independently from the specific characteristics of the different plants.

  18. High-energy neutron dosimetry

    NASA Astrophysics Data System (ADS)

    Sutton, Michele Rhea

    2001-12-01

    Fluence-to-dose conversion coefficients for the radiation protection quantity effective dose were calculated for neutrons, photons and protons with energies up to 2 GeV using the MCNPX code. The calculations were performed using the Pacific Northwest National Laboratory versions of the MIRD-V male and female anthropomorphic phantoms modified to include the skin and esophagus. The latest high-energy neutron evaluated cross-section libraries and the recommendations given in ICRP Publication 60 and ICRP Publication 74 were utilized to perform the calculations. Sets of fluence-to- effective dose conversion coefficients are given for anterior-posterior, posterior-anterior, left-lateral, right-lateral and rotational irradiation geometries. This is the first set of dose conversion coefficients over this energy range calculated for the L-LAT irradiation geometry. A unique set of high-energy neutron depth-dose benchmark experiments were performed at the Los Alamos Neutron Science Center/Weapons Neutron Research (LANSCE/WNR) complex. The experiments consisted of filtered neutron beams with energies up to 800 MeV impinging on a 30 x 30 x 30 cm3 tissue-equivalent phantom. The absorbed dose was measured in the phantom at various depths with tissue-equivalent ion chambers. The phantom and the experimental set-up were modeled using MCNPX. Comparisons of the experimental and computational depth- dose distributions indicate that the absorbed dose calculated by MCNPX is within 13% for neutrons with energies up to 750 MeV. This experiment will serve as a benchmark experiment for the testing of high-energy radiation transport codes for the international radiation protection community.

  19. Electron emission mechanism during the nanosecond high-voltage pulsed discharge in pressurized air

    NASA Astrophysics Data System (ADS)

    Levko, D.; Yatom, S.; Vekselman, V.; Krasik, Ya. E.

    2012-02-01

    A comparison between the results of x-ray absorption spectroscopy of runaway electrons (RAEs) generated during nanosecond timescale high-voltage (HV) gas discharge and the simulated attenuation of the x-ray flux produced by the runaway electron spectrum calculated using particle-in-cell numerical modeling of such a type of discharge is presented. The particle-in-cell simulation considered the field and explosive emissions (EEs) of the electrons from the cathode. It is shown that the field emission is the dominant emission mechanism for the short-duration (<2.5 ns) high-voltage pulses, while for the long-duration (>5 ns) high-voltage pulses, the explosive emission is likely to play a significant role.

  20. High Energy Astronomy Observatory (HEAO)

    NASA Technical Reports Server (NTRS)

    1972-01-01

    This is an artist's concept describing the High Energy Astronomy Observatory (HEAO). The HEAO project involved the launching of three unmarned scientific observatories into low Earth orbit between 1977 and 1979 to study some of the most intriguing mysteries of the universe; pulsars, black holes, neutron stars, and super nova. This concept was painted by Jack Hood of the Marshall Space Flight Center (MSFC). Hardware support for the imaging instruments was provided by American Science and Engineering. The HEAO spacecraft were built by TRW, Inc. under project management of the MSFC.

  1. Effect of biochar on nitrous oxide emission and its potential mechanisms.

    PubMed

    Liu, Liang; Shen, Guoqing; Sun, Mingxing; Cao, Xinde; Shang, Guofeng; Chen, Ping

    2014-08-01

    Extensive use of biochar to mitigate nitrous oxide (N2O) emission is limited by the lack of understanding on the exact mechanisms altering N2O emission from biochar-amended soil. Biochars produced from rice straw and dairy manure at 350 and 500 degrees C by oxygen-limited pyrolysis were used to investigate their influence on N2O emission. A quadratic effect of biochar levels was observed on the N2O emissions. The potential mechanisms were explored by terminal restriction fragment length polymorphism (T-RFLP) and real-time polymerase chain reaction (qPCR). A lower relative abundance of bacteria, which included ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), was observed at 4% biochar application rate. Reduced copy numbers of the ammonia monooxygenase gene amoA and the nitrite reductase gene nirS coincided with decreased N2O emissions. Therefore, biochar may potentially alter N2O emission by affecting ammonia-oxidizing and denitrification bacteria, which is determined by the application rate of biochar in soil. Implications: Biochar research has received increased interest in recent years because of the potential beneficial effects of biochar on soil properties. Recent research shows that biochar can alter the rates of nitrogen cycling in soil systems by influencing nitrification and denitrification, which are key sources of the greenhouse gas nitrous oxide (N2O). However, there are still some controversial data. The purpose of this research was to (1) examine how applications of different dose of biochar to soil affect emission of N2O and (2) improve the understanding of the underlying mechanisms. PMID:25185392

  2. Elements for the expected mechanisms on 'reduced emissions from deforestation and degradation, REDD' under UNFCCC

    NASA Astrophysics Data System (ADS)

    Mollicone, D.; Freibauer, A.; Schulze, E. D.; Braatz, S.; Grassi, G.; Federici, S.

    2007-10-01

    Carbon emissions from deforestation and degradation account for about 20% of global anthropogenic emissions. Strategies and incentives for reduced emissions from deforestation and degradation (REDD) have emerged as one of the most active areas in the international climate change negotiations under the United Nations Framework Convention on Climate Change (UNFCCC). While the current negotiations focus on a REDD mechanism in developing countries, it should be recognized that risks of carbon losses from forests occur in all climate zones and also in industrialized countries. A future climate change agreement would be more effective if it included all carbon losses and gains from land use in all countries and climate zones. The REDD mechanism will be an important step towards reducing emissions from land use change in developing countries, but needs to be followed by steps in other land use systems and regions. A national approach to REDD and significant coverage globally are needed to deal with the risk that deforestation and degradation activities are displaced rather than avoided. Favourable institutional and governance conditions need to be established that guarantee in the long-term a stable incentive and control system for maintaining forest carbon stocks. Ambitious emission reductions from deforestation and forest degradation need sustained financial incentives, which go beyond positive incentives for reduced emissions but also give incentives for sustainable forest management. Current data limitations need—and can be—overcome in the coming years to allow accurate accounting of reduced emissions from deforestation and degradation. A proper application of the conservativeness approach in the REDD context could allow a simplified reporting of emissions from deforestation in a first phase, consistent with the already agreed UNFCCC reporting principles.

  3. COMPARISON OF RELATIVE EMISSIONS FROM DOUBLE MECHANICAL PUMP SEALS TO OTHER TYPES OF PUMP SHAFT SEALS

    EPA Science Inventory

    The report gives results of a comparison of pump seal data from nine petroleum refineries, to evaluate emissions from double mechanical pump seals versus those from other types of pump shaft seals. Light- and heavy-liquid service seals were compared separately. Non-methane leak r...

  4. High Energy Laser Diagnostic Sensors

    NASA Astrophysics Data System (ADS)

    Luke, James R.; Goddard, Douglas N.; Lewis, Jay; Thomas, David

    2010-10-01

    Recent advancements in high energy laser (HEL) sources have outpaced diagnostic tools capable of accurately quantifying system performance. Diagnostic tools are needed that allow system developers to measure the parameters that define HEL effectiveness. The two critical parameters for quantifying HEL effectiveness are the irradiance on target and resultant rise in target temperature. Off-board sensing has its limitations, including unpredictable changes in the reflectivity of the target, smoke and outgassing, and atmospheric distortion. On-board sensors overcome the limitations of off-board techniques but must survive high irradiance levels and extreme temperatures. We have developed sensors for on-target diagnostics of high energy laser beams and for the measurement of the thermal response of the target. The conformal sensors consist of an array of quantum dot photodetectors and resistive temperature detectors. The sensor arrays are lithographically fabricated on flexible substrates and can be attached to a variety of laser targets. We have developed a nanoparticle adhesive process that provides good thermal contact with the target and that ensures the sensor remains attached to the target for as long as the target survives. We have calibrated the temperature and irradiance sensors and demonstrated them in a HEL environment.

  5. Duke University high energy physics

    SciTech Connect

    Fortney, L.R.; Goshaw, A.T.; Walker, W.D.

    1992-07-01

    This Progress Report presents a review of the research done in 1992 by the Duke High Energy Physics Group. This is the first year of a three-year grant which was approved by the Office of High Energy Physics at DOE after an external review of our research program during the summer of 1991. Our research is centered at Fermilab where we are involved with two active experiments, one using the Tevatron collider (CDF, the Collider Detector Facility) and the other using a proton beam in the high intensity laboratory (E771, study of beauty production). In addition to these running experiments we are continuing the analysis of data from experiments E735 (collider search for a quark-gluon plasma), E705 (fixed target study of direct photon and {sub {Chi}} meson production) and E597 (particle production from hadron-nucleus collisions). Finally, this year has seen an expansion of our involvement with the design of the central tracking detector for the Solenoidal Detector Collaboration (SDC) and an increased role in the governance of the collaboration. Descriptions of these research activities are presented in this report.

  6. Microwave emission from lead zirconate titanate induced by impulsive mechanical load

    SciTech Connect

    Aman, A.; Majcherek, S.; Hirsch, S.; Schmidt, B.

    2015-10-28

    This paper focuses on microwave emission from Lead zirconate titanate Pb [Zr{sub x}Ti{sub 1−x}] O{sub 3} (PZT) induced by mechanical stressing. The mechanical stress was initiated by impact of a sharp tungsten indenter on the upper surface of PZT ceramic. The sequences of microwave and current impulses, which flew from indenter to electric ground, were detected simultaneously. The voltage between the upper and lower surface of ceramic was measured to obtain the behavior of mechanical force acting on ceramic during the impact. It was found that the amplitude, form, and frequency of measured microwave impulses were different by compression and restitution phase of impact. Two different mechanisms of electron emission, responsible for microwave impulse generation, were proposed based on the dissimilar impulse behavior. The field emission from tungsten indenter is dominant during compression, whereas ferroemission dominates during restitution phase. Indeed, it was observed that the direction of the current flow, i.e., sign of current impulses is changed by transitions from compression to restitution phase of impact. The observed dissimilar behavior of microwave impulses, caused by increasing and decreasing applied force, can be used to calculate the contact time and behavior of mechanical force during mechanical impact on ceramic surface. It is shown that the generation of microwave impulses exhibits high reproducibility, impulse intensity, a low damping factor, and high mechanical failure resistance. Based on these microwave emission properties of PZT, the development of new type of stress sensor with spatial resolution of few microns becomes possible.

  7. Enhanced adhesion from high energy ion irradiation

    NASA Technical Reports Server (NTRS)

    Werner, B. T.; Vreeland, T., Jr.; Mendenhall, M. H.; Qui, Y.; Tombrello, T. A.

    1983-01-01

    It has been found that the adhesion of thin metal films on insulators, semiconductors, and metals could be improved by subjecting the material to a high-energy ion bombardment. Griffith et al. (1982) have first suggested a use of this technique with insulators. The present investigation has the objective to determine the mechanism for the adhesion enhancement. A description is presented of a preliminary transmission electron microscopy (TEM) study of thinned bonded samples of silver on silicon using electron diffraction. It is found that irradiation of a variety of thin film-substrate combinations by heavy ion beams will provide a remarkable improvement in the adherence of the film. The evidence for the mechanism involved in the enhancement of adhesion is discussed.

  8. Detection potential of the KM3NeT detector for high-energy neutrinos from the Fermi bubbles

    NASA Astrophysics Data System (ADS)

    KM3NeT Collaboration; Adrián-Martínez, S.; Ageron, M.; Aguilar, J. A.; Aharonian, F.; Aiello, S.; Albert, A.; Alexandri, M.; Ameli, F.; Anassontzis, E. G.; Anghinolfi, M.; Anton, G.; Anvar, S.; Ardid, M.; Assis Jesus, A.; Aubert, J.-J.; Bakker, R.; Ball, A. E.; Barbarino, G.; Barbarito, E.; Barbato, F.; Baret, B.; de Bel, M.; Belias, A.; Bellou, N.; Berbee, E.; Berkien, A.; Bersani, A.; Bertin, V.; Beurthey, S.; Biagi, S.; Bigongiari, C.; Bigourdan, B.; Billault, M.; de Boer, R.; Boer Rookhuizen, H.; Bonori, M.; Borghini, M.; Bou-Cabo, M.; Bouhadef, B.; Bourlis, G.; Bouwhuis, M.; Bradbury, S.; Brown, A.; Bruni, F.; Brunner, J.; Brunoldi, M.; Busto, J.; Cacopardo, G.; Caillat, L.; Calvo Díaz-Aldagalán, D.; Calzas, A.; Canals, M.; Capone, A.; Carr, J.; Castorina, E.; Cecchini, S.; Ceres, A.; Cereseto, R.; Chaleil, Th.; Chateau, F.; Chiarusi, T.; Choqueuse, D.; Christopoulou, P. E.; Chronis, G.; Ciaffoni, O.; Circella, M.; Cocimano, R.; Cohen, F.; Colijn, F.; Coniglione, R.; Cordelli, M.; Cosquer, A.; Costa, M.; Coyle, P.; Craig, J.; Creusot, A.; Curtil, C.; D'Amico, A.; Damy, G.; De Asmundis, R.; De Bonis, G.; Decock, G.; Decowski, P.; Delagnes, E.; De Rosa, G.; Distefano, C.; Donzaud, C.; Dornic, D.; Dorosti-Hasankiadeh, Q.; Drogou, J.; Drouhin, D.; Druillole, F.; Drury, L.; Durand, D.; Durand, G. A.; Eberl, T.; Emanuele, U.; Enzenhöfer, A.; Ernenwein, J.-P.; Escoffier, S.; Espinosa, V.; Etiope, G.; Favali, P.; Felea, D.; Ferri, M.; Ferry, S.; Flaminio, V.; Folger, F.; Fotiou, A.; Fritsch, U.; Gajanana, D.; Garaguso, R.; Gasparini, G. P.; Gasparoni, F.; Gautard, V.; Gensolen, F.; Geyer, K.; Giacomelli, G.; Gialas, I.; Giordano, V.; Giraud, J.; Gizani, N.; Gleixner, A.; Gojak, C.; Gómez-González, J. P.; Graf, K.; Grasso, D.; Grimaldi, A.; Groenewegen, R.; Guédé, Z.; Guillard, G.; Guilloux, F.; Habel, R.; Hallewell, G.; van Haren, H.; van Heerwaarden, J.; Heijboer, A.; Heine, E.; Hernández-Rey, J. J.; Herold, B.; Hillebrand, T.; van de Hoek, M.; Hogenbirk, J.; Hößl, J.; Hsu, C. C.; Imbesi, M.; Jamieson, A.; Jansweijer, P.; de Jong, M.; Jouvenot, F.; Kadler, M.; Kalantar-Nayestanaki, N.; Kalekin, O.; Kappes, A.; Karolak, M.; Katz, U. F.; Kavatsyuk, O.; Keller, P.; Kiskiras, Y.; Klein, R.; Kok, H.; Kontoyiannis, H.; Kooijman, P.; Koopstra, J.; Kopper, C.; Korporaal, A.; Koske, P.; Kouchner, A.; Koutsoukos, S.; Kreykenbohm, I.; Kulikovskiy, V.; Laan, M.; La Fratta, C.; Lagier, P.; Lahmann, R.; Lamare, P.; Larosa, G.; Lattuada, D.; Leisos, A.; Lenis, D.; Leonora, E.; Le Provost, H.; Lim, G.; Llorens, C. D.; Lloret, J.; Löhner, H.; Lo Presti, D.; Lotrus, P.; Louis, F.; Lucarelli, F.; Lykousis, V.; Malyshev, D.; Mangano, S.; Marcoulaki, E. C.; Margiotta, A.; Marinaro, G.; Marinelli, A.; Mariş, O.; Markopoulos, E.; Markou, C.; Martínez-Mora, J. A.; Martini, A.; Marvaldi, J.; Masullo, R.; Maurin, G.; Migliozzi, P.; Migneco, E.; Minutoli, S.; Miraglia, A.; Mollo, C. M.; Mongelli, M.; Monmarthe, E.; Morganti, M.; Mos, S.; Motz, H.; Moudden, Y.; Mul, G.; Musico, P.; Musumeci, M.; Naumann, Ch.; Neff, M.; Nicolaou, C.; Orlando, A.; Palioselitis, D.; Papageorgiou, K.; Papaikonomou, A.; Papaleo, R.; Papazoglou, I. A.; Păvălaş, G. E.; Peek, H. Z.; Perkin, J.; Piattelli, P.; Popa, V.; Pradier, T.; Presani, E.; Priede, I. G.; Psallidas, A.; Rabouille, C.; Racca, C.; Radu, A.; Randazzo, N.; Rapidis, P. A.; Razis, P.; Real, D.; Reed, C.; Reito, S.; Resvanis, L. K.; Riccobene, G.; Richter, R.; Roensch, K.; Rolin, J.; Rose, J.; Roux, J.; Rovelli, A.; Russo, A.; Russo, G. V.; Salesa, F.; Samtleben, D.; Sapienza, P.; Schmelling, J.-W.; Schmid, J.; Schnabel, J.; Schroeder, K.; Schuller, J.-P.; Schussler, F.; Sciliberto, D.; Sedita, M.; Seitz, T.; Shanidze, R.; Simeone, F.; Siotis, I.; Sipala, V.; Sollima, C.; Sparnocchia, S.; Spies, A.; Spurio, M.; Staller, T.; Stavrakakis, S.; Stavropoulos, G.; Steijger, J.; Stolarczyk, Th.; Stransky, D.; Taiuti, M.; Taylor, A.; Thompson, L.; Timmer, P.; Tonoiu, D.; Toscano, S.; Touramanis, C.; Trasatti, L.; Traverso, P.; Trovato, A.; Tsirigotis, A.; Tzamarias, S.; Tzamariudaki, E.; Urbano, F.; Vallage, B.; Van Elewyck, V.; Vannoni, G.; Vecchi, M.; Vernin, P.; Viola, S.; Vivolo, D.; Wagner, S.; Werneke, P.; White, R. J.; Wijnker, G.; Wilms, J.; de Wolf, E.; Yepes, H.; Zhukov, V.; Zonca, E.; Zornoza, J. D.; Zúñiga, J.

    2013-02-01

    A recent analysis of the Fermi Large Area Telescope data provided evidence for a high-intensity emission of high-energy gamma rays with a E-2 spectrum from two large areas, spanning 50° above and below the Galactic centre (the "Fermi bubbles"). A hadronic mechanism was proposed for this gamma-ray emission making the Fermi bubbles promising source candidates of high-energy neutrino emission. In this work Monte Carlo simulations regarding the detectability of high-energy neutrinos from the Fermi bubbles with the future multi-km3 neutrino telescope KM3NeT in the Mediterranean Sea are presented. Under the hypothesis that the gamma-ray emission is completely due to hadronic processes, the results indicate that neutrinos from the bubbles could be discovered in about one year of operation, for a neutrino spectrum with a cutoff at 100 TeV and a detector with about 6 km3 of instrumented volume. The effect of a possible lower cutoff is also considered.

  9. Quantum mechanical modeling the emission pattern and polarization of nanoscale light emitting diodes

    NASA Astrophysics Data System (ADS)

    Wang, Rulin; Zhang, Yu; Bi, Fuzhen; Frauenheim, Thomas; Chen, Guanhua; Yam, Chiyung

    2016-07-01

    Understanding of the electroluminescence (EL) mechanism in optoelectronic devices is imperative for further optimization of their efficiency and effectiveness. Here, a quantum mechanical approach is formulated for modeling the EL processes in nanoscale light emitting diodes (LED). Based on non-equilibrium Green's function quantum transport equations, interactions with the electromagnetic vacuum environment are included to describe electrically driven light emission in the devices. The presented framework is illustrated by numerical simulations of a silicon nanowire LED device. EL spectra of the nanowire device under different bias voltages are obtained and, more importantly, the radiation pattern and polarization of optical emission can be determined using the current approach. This work is an important step forward towards atomistic quantum mechanical modeling of the electrically induced optical response in nanoscale systems.

  10. Quantum mechanical modeling the emission pattern and polarization of nanoscale light emitting diodes.

    PubMed

    Wang, Rulin; Zhang, Yu; Bi, Fuzhen; Frauenheim, Thomas; Chen, GuanHua; Yam, ChiYung

    2016-07-21

    Understanding of the electroluminescence (EL) mechanism in optoelectronic devices is imperative for further optimization of their efficiency and effectiveness. Here, a quantum mechanical approach is formulated for modeling the EL processes in nanoscale light emitting diodes (LED). Based on non-equilibrium Green's function quantum transport equations, interactions with the electromagnetic vacuum environment are included to describe electrically driven light emission in the devices. The presented framework is illustrated by numerical simulations of a silicon nanowire LED device. EL spectra of the nanowire device under different bias voltages are obtained and, more importantly, the radiation pattern and polarization of optical emission can be determined using the current approach. This work is an important step forward towards atomistic quantum mechanical modeling of the electrically induced optical response in nanoscale systems. PMID:27249329

  11. Mechanism for Broadband White-Light Emission from Two-Dimensional (110) Hybrid Perovskites.

    PubMed

    Hu, Te; Smith, Matthew D; Dohner, Emma R; Sher, Meng-Ju; Wu, Xiaoxi; Trinh, M Tuan; Fisher, Alan; Corbett, Jeff; Zhu, X-Y; Karunadasa, Hemamala I; Lindenberg, Aaron M

    2016-06-16

    The recently discovered phenomenon of broadband white-light emission at room temperature in the (110) two-dimensional organic-inorganic perovskite (N-MEDA)[PbBr4] (N-MEDA = N(1)-methylethane-1,2-diammonium) is promising for applications in solid-state lighting. However, the spectral broadening mechanism and, in particular, the processes and dynamics associated with the emissive species are still unclear. Herein, we apply a suite of ultrafast spectroscopic probes to measure the primary events directly following photoexcitation, which allows us to resolve the evolution of light-induced emissive states associated with white-light emission at femtosecond resolution. Terahertz spectra show fast free carrier trapping and transient absorption spectra show the formation of self-trapped excitons on femtosecond time-scales. Emission-wavelength-dependent dynamics of the self-trapped exciton luminescence are observed, indicative of an energy distribution of photogenerated emissive states in the perovskite. Our results are consistent with photogenerated carriers self-trapped in a deformable lattice due to strong electron-phonon coupling, where permanent lattice defects and correlated self-trapped states lend further inhomogeneity to the excited-state potential energy surface. PMID:27246299

  12. Grid Computing in High Energy Physics

    NASA Astrophysics Data System (ADS)

    Avery, Paul

    2004-09-01

    Over the next two decades, major high energy physics (HEP) experiments, particularly at the Large Hadron Collider, will face unprecedented challenges to achieving their scientific potential. These challenges arise primarily from the rapidly increasing size and complexity of HEP datasets that will be collected and the enormous computational, storage and networking resources that will be deployed by global collaborations in order to process, distribute and analyze them. Coupling such vast information technology resources to globally distributed collaborations of several thousand physicists requires extremely capable computing infrastructures supporting several key areas: (1) computing (providing sufficient computational and storage resources for all processing, simulation and analysis tasks undertaken by the collaborations); (2) networking (deploying high speed networks to transport data quickly between institutions around the world); (3) software (supporting simple and transparent access to data and software resources, regardless of location); (4) collaboration (providing tools that allow members full and fair access to all collaboration resources and enable distributed teams to work effectively, irrespective of location); and (5) education, training and outreach (providing resources and mechanisms for training students and for communicating important information to the public). It is believed that computing infrastructures based on Data Grids and optical networks can meet these challenges and can offer data intensive enterprises in high energy physics and elsewhere a comprehensive, scalable framework for collaboration and resource sharing. A number of Data Grid projects have been underway since 1999. Interestingly, the most exciting and far ranging of these projects are led by collaborations of high energy physicists, computer scientists and scientists from other disciplines in support of experiments with massive, near-term data needs. I review progress in this

  13. Tactical high-energy laser

    NASA Astrophysics Data System (ADS)

    Shwartz, Josef; Wilson, Gerald T.; Avidor, Joel M.

    2002-06-01

    The Nautilus Project was started in 1995 as a joint US-Israel feasibility study for using laser systems to defend against short-range artillery rockets. It has now matured into a successful laser weapon demonstration program - the Tactical High Energy Laser (THEL) Advanced Concept Technology Demonstration (ACTD) Program. By now the THEL Demonstrator has engaged and destroyed a large number of artillery rockets in mid-flight in an extended series of demonstration tests at the US Army's White Sands Missile Range in New Mexico. The THEL ACTD hardware and development process are described in this paper, as well as the major test results. The paper also describes the operational concept for a deployed THEL weapon system and some possible growth paths for the THEL ACTD Program.

  14. Oxides having high energy densities

    DOEpatents

    Ceder, Gerbrand; Kang, Kisuk

    2013-09-10

    Certain disclosed embodiments generally relate to oxide materials having relatively high energy and/or power densities. Various aspects of the embodiments are directed to oxide materials having a structure B.sub.i(M.sub.jY.sub.k)O.sub.2, for example, a structure Li.sub.j(Ni.sub.jY.sub.k)O.sub.2 such as Li(Ni.sub.0.5Mn.sub.0.5)O.sub.2. In this structure, Y represents one or more atoms, each independently selected from the group consisting of alkaline earth metals, transition metals, Group 14 elements, Group 15, or Group 16 elements. In some embodiments, such an oxide material may have an O3 crystal structure, and/or a layered structure such that the oxide comprises a plurality of first, repeating atomic planes comprising Li, and a plurality of second, repeating atomic planes comprising Ni and/or Y.

  15. Pion exchange at high energies

    SciTech Connect

    Jones, L.M.

    1980-07-01

    The state of Regge pion exchange calculations for high-energy reactions is reviewed. Experimental evidence is summarized to show that (i) the pion trajectory has a slope similar to that of other trajectories; (ii) the pion exchange contribution can dominate contributions of higher trajectories up to quite a large energy; (iii) many two-body cross sections with large pion contributions can be fit only by models which allow for kinematical conspiracy at t=0. The theory of kinematic conspiracy is reviewed for two-body amplitudes, and calculations of the conspiring pion--Pomeron cut discussed. The author then summarizes recent work on pion exchange in Reggeized Deck models for multiparticle final states, with emphasis on the predictions of various models (with and without resonances) for phases of the partial wave amplitudes.

  16. High Energy Density Laboratory Astrophysics

    SciTech Connect

    Remington, B A

    2004-11-11

    High-energy-density (HED) physics refers broadly to the study of macroscopic collections of matter under extreme conditions of temperature and density. The experimental facilities most widely used for these studies are high-power lasers and magnetic-pinch generators. The HED physics pursued on these facilities is still in its infancy, yet new regimes of experimental science are emerging. Examples from astrophysics include work relevant to planetary interiors, supernovae, astrophysical jets, and accreting compact objects (such as neutron stars and black holes). In this paper, we will review a selection of recent results in this new field of HED laboratory astrophysics and provide a brief look ahead to the coming decade.

  17. Self-consistent particle-in-cell simulations of fundamental and harmonic plasma radio emission mechanisms

    NASA Astrophysics Data System (ADS)

    Thurgood, J. O.; Tsiklauri, D.

    2015-12-01

    Aims: The simulation of three-wave interaction based plasma emission, thought to be the underlying mechanism for Type III solar radio bursts, is a challenging task requiring fully-kinetic, multi-dimensional models. This paper aims to resolve a contradiction in past attempts, whereby some studies indicate that no such processes occur. Methods: We self-consistently simulate three-wave based plasma emission through all stages by using 2D, fully kinetic, electromagnetic particle-in-cell simulations of relaxing electron beams using the EPOCH2D code. Results: Here we present the results of two simulations; Run 1 (nb/n0 = 0.0057, vb/ Δvb = vb/Ve = 16) and Run 2 (nb/n0 = 0.05, vb/ Δvb = vb/Ve = 8), which we find to permit and prohibit plasma emission respectively. We show that the possibility of plasma emission is contingent upon the frequency of the initial electrostatic waves generated by the bump-in-tail instability, and that these waves may be prohibited from participating in the necessary three-wave interactions due to frequency conservation requirements. In resolving this apparent contradiction through a comprehensive analysis, in this paper we present the first self-consistent demonstration of fundamental and harmonic plasma emission from a single-beam system via fully kinetic numerical simulation. We caution against simulating astrophysical radio bursts using unrealistically dense beams (a common approach which reduces run time), as the resulting non-Langmuir characteristics of the initial wave modes significantly suppresses emission. Comparison of our results also indicates that, contrary to the suggestions of previous authors, an alternative plasma emission mechanism based on two counter-propagating beams is unnecessary in an astrophysical context. Finally, we also consider the action of the Weibel instability which generates an electromagnetic beam mode. As this provides a stronger contribution to electromagnetic energy than the emission, we stress that

  18. The role of triplet states in the emission mechanism of polymer light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Arif, M.; Mukhopadhyay, S.; Ramasesha, S.; Guha, S.

    2009-09-01

    The blue emission of polyfluorene (PF)-based light-emitting diodes (LEDs) is known to degrade due to a low-energy green emission, which hitherto has been attributed to oxidative defects. By studying the electroluminescence (EL) from ethyl-hexyl substituted PF LEDs in the presence of oxygen and in an inert atmosphere, and by using trace quantities of paramagnetic impurities (PM) in the polymer, we show that the triplet states play a major role in the low-energy emission mechanism. Our time-dependent many-body studies show a large cross-section for the triplet formation in the EL process in the presence of PM, primarily due to electron-hole recombination processes.

  19. Mechanisms and modeling of the effects of additives on the nitrogen oxides emission

    NASA Technical Reports Server (NTRS)

    Kundu, Krishna P.; Nguyen, Hung Lee; Kang, M. Paul

    1991-01-01

    A theoretical study on the emission of the oxides of nitrogen in the combustion of hydrocarbons is presented. The current understanding of the mechanisms and the rate parameters for gas phase reactions were used to calculate the NO(x) emission. The possible effects of different chemical species on thermal NO(x), on a long time scale were discussed. The mixing of these additives at various stages of combustion were considered and NO(x) concentrations were calculated; effects of temperatures were also considered. The chemicals such as hydrocarbons, H2, CH3OH, NH3, and other nitrogen species were chosen as additives in this discussion. Results of these calculations can be used to evaluate the effects of these additives on the NO(x) emission in the industrial combustion system.

  20. Initiation of vacuum breakdown and failure mechanism of the carbon nanotube during thermal field emission

    NASA Astrophysics Data System (ADS)

    Dan, Cai; Lie, Liu; Jin-Chuan, Ju; Xue-Long, Zhao; Hong-Yu, Zhou; Xiao, Wang

    2016-04-01

    The carbon nanotube (CNT)-based materials can be used as vacuum device cathodes. Owing to the excellent field emission properties of CNT, it has great potentials in the applications of an explosive field emission cathode. The falling off of CNT from the substrate, which frequently appears in experiments, restricts its application. In addition, the onset time of vacuum breakdown limits the performance of the high-power explosive-emission-cathode-based diode. In this paper, the characteristics of the CNT, electric field strength, contact resistance and the kind of substrate material are varied to study the parameter effects on the onset time of vacuum breakdown and failure mechanism of the CNT by using the finite element method. Project supported by the National Natural Science Foundation of China (Grant Nos. 11305263 and 61401484).

  1. Carbon dioxide emissions under different soil tillage systems in mechanically harvested sugarcane

    NASA Astrophysics Data System (ADS)

    Silva-Olaya, A. M.; Cerri, C. E. P.; La Scala, N., Jr.; Dias, C. T. S.; Cerri, C. C.

    2013-03-01

    Soil tillage and other methods of soil management may influence CO2 emissions because they accelerate the mineralization of organic carbon in the soil. This study aimed to quantify the CO2 emissions under conventional tillage (CT), minimum tillage (MT) and reduced tillage (RT) during the renovation of sugarcane fields in southern Brazil. The experiment was performed on an Oxisol in the sugarcane-planting area with mechanical harvesting. An undisturbed or no-till (NT) plot was left as a control treatment. The CO2 emissions results indicated a significant interaction (p < 0.001) between tillage method and time after tillage. By quantifying the accumulated emissions over the 44 days after soil tillage, we observed that tillage-induced emissions were higher after the CT system than the RT and MT systems, reaching 350.09 g m-2 of CO2 in CT, and 51.7 and 5.5 g m-2 of CO2 in RT and MT respectively. The amount of C lost in the form of CO2 due to soil tillage practices was significant and comparable to the estimated value of potential annual C accumulation resulting from changes in the harvesting system in Brazil from burning of plant residues to the adoption of green cane harvesting. The CO2 emissions in the CT system could respond to a loss of 80% of the potential soil C accumulated over one year as result of the adoption of mechanized sugarcane harvesting. Meanwhile, soil tillage during the renewal of the sugar plantation using RT and MT methods would result in low impact, with losses of 12% and 2% of the C that could potentially be accumulated during a one year period.

  2. X-ray Imaging and preliminary studies of the X-ray self-emission from an innovative plasma-trap based on the Bernstein waves heating mechanism

    NASA Astrophysics Data System (ADS)

    Caliri, C.; Romano, F. P.; Mascali, D.; Gammino, S.; Musumarra, A.; Castro, G.; Celona, L.; Neri, L.; Altana, C.

    2013-10-01

    Electron Cyclotron Resonance Ion Sources (ECRIS) are based on ECR heated plasmas emitting high fluxes of X-rays. Here we illustrate a pilot study of the X-ray emission from a compact plasma-trap in which an off-resonance microwave-plasma interaction has been attempted, highlighting a possible Bernstein-Waves based heating mechanism. EBWs-heating is obtained via the inner plasma EM-to-ES wave conversion and enables to reach densities much larger than the cut-off ones. At LNS-INFN, an innovative diagnostic technique based on the design of a Pinhole Camera (PHC) coupled to a CCD device for X-ray Imaging of the plasma (XRI) has been developed, in order to integrate X-ray traditional diagnostics (XRS). The complementary use of electrostatic probes measurements and X-ray diagnostics enabled us to gain knowledge about the high energy electrons density and temperature and about the spatial structure of the source. The combination of the experimental data with appropriate modeling of the plasma-source allowed to estimate the X-ray emission intensity in different energy domains (ranging from EUV up to Hard X-rays). The use of ECRIS as X-ray source for multidisciplinary applications, is now a concrete perspective due to the intense fluxes produced by the new plasma heating mechanism.

  3. Laboratory laser acceleration and high energy astrophysics: {gamma}-ray bursts and cosmic rays

    SciTech Connect

    Tajima, T.; Takahashi, Y.

    1998-08-20

    Recent experimental progress in laser acceleration of charged particles (electrons) and its associated processes has shown that intense electromagnetic pulses can promptly accelerate charged particles to high energies and that their energy spectrum is quite hard. On the other hand some of the high energy astrophysical phenomena such as extremely high energy cosmic rays and energetic components of {gamma}-ray bursts cry for new physical mechanisms for promptly accelerating particles to high energies. The authors suggest that the basic physics involved in laser acceleration experiments sheds light on some of the underlying mechanisms and their energy spectral characteristics of the promptly accelerated particles in these high energy astrophysical phenomena.

  4. Distortion product otoacoustic emissions provide clues to hearing mechanisms in the frog ear

    NASA Astrophysics Data System (ADS)

    Vassilakis, Pantelis N.; Meenderink, Sebastiaan W. F.; Narins, Peter M.

    2004-12-01

    2 f1-f2 and 2 f2-f1 distortion product otoacoustic emissions (DPOAEs) were recorded from both ears of male and female Rana pipiens pipiens and Rana catesbeiana. The input-output (I/O) curves obtained from the amphibian papilla (AP) of both frog species are analogous to I/O curves recorded from mammals suggesting that, similarly to the mammalian cochlea, there may be an amplification process present in the frog AP. DPOAE level dependence on L1-L2 is different from that in mammals and consistent with intermodulation distortion expectations. Therefore, if a mechanical structure in the frog inner ear is functioning analogously to the mammalian basilar membrane, it must be more broadly tuned. DPOAE audiograms were obtained for primary frequencies spanning the animals' hearing range and selected stimulus levels. The results confirm that DPOAEs are produced in both papillae, with R. catesbeiana producing stronger emissions than R. p. pipiens. Consistent with previously reported sexual dimorphism in the mammalian and anuran auditory systems, females of both species produce stronger emissions than males. Moreover, it appears that 2 f1-f2 in the frog is generated primarily at the DPOAE frequency place, while 2 f2-f1 is generated primarily at a frequency place around the primaries. Regardless of generation place, both emissions within the AP may be subject to the same filtering mechanism, possibly the tectorial membrane..

  5. Greenhouse gas emissions from mechanical and biological waste treatment of municipal waste.

    PubMed

    Clemens, J; Cuhls, C

    2003-06-01

    The mechanical and biological waste treatment (MBT) is an increasingly important technology for the treatment of municipal solid waste (MSW) before landfilling. This process includes composting of the material with intensive aeration in order to minimize the organic fraction that may induce methane and leachate emissions after landfilling. The exhaust air is treated by biofilters to remove odorous and volatile organic compounds. The emission of direct and indirect greenhouse gases, namely methane (CH4), carbon dioxide (CO2), ammonia (NH3), nitric (NO) and nitrous oxide (N2O) was studied in four existing treatment plants. All gases except NO were emitted from the composting material. The emission factors were 12 to 185 kg ton(-1) substrate for CO2, 6-12 x 10(3) g ton(-1) substrate for CH4, 1.44 to 378 g ton(-1) substrate for N2O and 18-1150 g ton(-1) for NH3. In general, emission factors increased with increasing treatment time. The biofilters had no net effect on CH4, but removed 13-89% of the NH3. For CO2 the biofilters were a small, for N2O a major and for NO the exclusive source. Approximately 26% of the NH3-N that was removed in the biofilter was transformed into N2O when NH3 was the exclusive nitrogen source. Assuming that all municipal waste was treated by MBT, the emissions would account for 0.3 to 5% of the N2O and for 0.1 to 3% of the CH4 emissions in Germany, respectively. Optimising aeration and removing NH3 before the exhaust gas enters the biofilter could lead to reduced greenhouse gas emissions. PMID:12868530

  6. PANCHROMATIC OBSERVATIONS OF THE TEXTBOOK GRB 110205A: CONSTRAINING PHYSICAL MECHANISMS OF PROMPT EMISSION AND AFTERGLOW

    SciTech Connect

    Zheng, W.; Shen, R. F.; Sakamoto, T.; Beardmore, A. P.; De Pasquale, M.; Wu, X. F.; Zhang, B.; Gorosabel, J.; Urata, Y.; Sugita, S.; Pozanenko, A.; Sahu, D. K.; Im, M.; Ukwatta, T. N.; Andreev, M.; Klunko, E. E-mail: rfshen@astro.utoronto.ca; and others

    2012-06-01

    We present a comprehensive analysis of a bright, long-duration (T{sub 90} {approx} 257 s) GRB 110205A at redshift z = 2.22. The optical prompt emission was detected by Swift/UVOT, ROTSE-IIIb, and BOOTES telescopes when the gamma-ray burst (GRB) was still radiating in the {gamma}-ray band, with optical light curve showing correlation with {gamma}-ray data. Nearly 200 s of observations were obtained simultaneously from optical, X-ray, to {gamma}-ray (1 eV to 5 MeV), which makes it one of the exceptional cases to study the broadband spectral energy distribution during the prompt emission phase. In particular, we clearly identify, for the first time, an interesting two-break energy spectrum, roughly consistent with the standard synchrotron emission model in the fast cooling regime. Shortly after prompt emission ({approx}1100 s), a bright (R = 14.0) optical emission hump with very steep rise ({alpha} {approx} 5.5) was observed, which we interpret as the reverse shock (RS) emission. It is the first time that the rising phase of an RS component has been closely observed. The full optical and X-ray afterglow light curves can be interpreted within the standard reverse shock (RS) + forward shock (FS) model. In general, the high-quality prompt and afterglow data allow us to apply the standard fireball model to extract valuable information, including the radiation mechanism (synchrotron), radius of prompt emission (R{sub GRB} {approx} 3 Multiplication-Sign 10{sup 13} cm), initial Lorentz factor of the outflow ({Gamma}{sub 0} {approx} 250), the composition of the ejecta (mildly magnetized), the collimation angle, and the total energy budget.

  7. The Structure and Emission Model of the Relativistic Jet in the Quasar 3C 279 Inferred From Radio To High-Energy Gamma-Ray Observations in 2008-2010

    NASA Technical Reports Server (NTRS)

    2012-01-01

    We present time-resolved broad-band observations of the quasar 3C 279 obtained from multiwavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported gamma-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears delayed with respect to the gamma-ray emission by about 10 days. X-ray observations reveal a pair of 'isolated' flares separated. by approx. 90 days, with only weak gamma-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the gamma-ray flare, while the peak appears in the mm/sub-mm band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broad-band spectra during the gamma-ray flaring event by a shift of its location from approx. 1 pc to approx. 4 pc from the central black hole. On the other hand, if the gamma-ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.

  8. THE STRUCTURE AND EMISSION MODEL OF THE RELATIVISTIC JET IN THE QUASAR 3C 279 INFERRED FROM RADIO TO HIGH-ENERGY {gamma}-RAY OBSERVATIONS IN 2008-2010

    SciTech Connect

    Hayashida, M.; Madejski, G. M.; Chiang, J.; Blandford, R. D.; Buehler, R.; Sikora, M.; Wehrle, A. E.; Ogle, P.; Collmar, W.; Larsson, S.; Fukazawa, Y.; Itoh, R.; Stawarz, L.; Richards, J. L.; Max-Moerbeck, W.; Readhead, A.; Cavazzuti, E.; Ciprini, S.; Gehrels, N. E-mail: madejski@slac.stanford.edu E-mail: sikora@camk.edu.pl; and others

    2012-08-01

    We present time-resolved broadband observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported {gamma}-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears to be delayed with respect to the {gamma}-ray emission by about 10 days. X-ray observations reveal a pair of 'isolated' flares separated by {approx}90 days, with only weak {gamma}-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the {gamma}-ray flare, while the peak appears in the millimeter (mm)/submillimeter (sub-mm) band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broadband spectra during the {gamma}-ray flaring event by a shift of its location from {approx}1 pc to {approx}4 pc from the central black hole. On the other hand, if the {gamma}-ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.

  9. The Structure and Emission Model of the Relativistic Jet in the Quasar 3C 279 Inferred from Radio to High-energy γ-Ray Observations in 2008-2010

    NASA Astrophysics Data System (ADS)

    Hayashida, M.; Madejski, G. M.; Nalewajko, K.; Sikora, M.; Wehrle, A. E.; Ogle, P.; Collmar, W.; Larsson, S.; Fukazawa, Y.; Itoh, R.; Chiang, J.; Stawarz, Ł.; Blandford, R. D.; Richards, J. L.; Max-Moerbeck, W.; Readhead, A.; Buehler, R.; Cavazzuti, E.; Ciprini, S.; Gehrels, N.; Reimer, A.; Szostek, A.; Tanaka, T.; Tosti, G.; Uchiyama, Y.; Kawabata, K. S.; Kino, M.; Sakimoto, K.; Sasada, M.; Sato, S.; Uemura, M.; Yamanaka, M.; Greiner, J.; Kruehler, T.; Rossi, A.; Macquart, J. P.; Bock, D. C.-J.; Villata, M.; Raiteri, C. M.; Agudo, I.; Aller, H. D.; Aller, M. F.; Arkharov, A. A.; Bach, U.; Benítez, E.; Berdyugin, A.; Blinov, D. A.; Blumenthal, K.; Böttcher, M.; Buemi, C. S.; Carosati, D.; Chen, W. P.; Di Paola, A.; Dolci, M.; Efimova, N. V.; Forné, E.; Gómez, J. L.; Gurwell, M. A.; Heidt, J.; Hiriart, D.; Jordan, B.; Jorstad, S. G.; Joshi, M.; Kimeridze, G.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Kurtanidze, O. M.; Lähteenmäki, A.; Lamerato, A.; Larionov, V. M.; Larionova, E. G.; Larionova, L. V.; Leto, P.; Lindfors, E.; Marscher, A. P.; McHardy, I. M.; Molina, S. N.; Morozova, D. A.; Nikolashvili, M. G.; Nilsson, K.; Reinthal, R.; Roustazadeh, P.; Sakamoto, T.; Sigua, L. A.; Sillanpää, A.; Takalo, L.; Tammi, J.; Taylor, B.; Tornikoski, M.; Trigilio, C.; Troitsky, I. S.; Umana, G.

    2012-08-01

    We present time-resolved broadband observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported γ-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears to be delayed with respect to the γ-ray emission by about 10 days. X-ray observations reveal a pair of "isolated" flares separated by ~90 days, with only weak γ-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the γ-ray flare, while the peak appears in the millimeter (mm)/submillimeter (sub-mm) band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broadband spectra during the γ-ray flaring event by a shift of its location from ~1 pc to ~4 pc from the central black hole. On the other hand, if the γ-ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.

  10. Toward an Understanding of GRB Prompt Emission Mechanism. I. The Origin of Spectral Lags

    NASA Astrophysics Data System (ADS)

    Uhm, Z. Lucas; Zhang, Bing

    2016-07-01

    Despite decades of investigations, the physical mechanism that powers the bright prompt γ-ray emission from gamma-ray bursts (GRBs) is still not identified. One important observational clue that still has not been properly interpreted is the existence of time lags of broad light curve pulses in different energy bands, referred to as “spectral lags.” Here, we show that the traditional view invoking the high-latitude emission “curvature effect” of a relativistic jet cannot account for spectral lags. Rather, the observed spectral lags demand the sweep of a spectral peak across the observing energy band in a specific manner. The duration of the broad pulses and inferred typical Lorentz factor of GRBs require that the emission region be in an optically thin emission region far from the GRB central engine. We construct a simple physical model invoking synchrotron radiation from a rapidly expanding outflow. We show that the observed spectral lags appear naturally in our model light curves given that (1) the gamma-ray photon spectrum is curved (as observed), (2) the magnetic field strength in the emitting region decreases with radius as the region expands in space, and (3) the emission region itself undergoes rapid bulk acceleration as the prompt γ-rays are produced. These requirements are consistent with a Poynting-flux-dominated jet abruptly dissipating magnetic energy at a large distance from the engine.

  11. Field emission driven direct current argon discharges and electrical breakdown mechanism across micron scale gaps

    NASA Astrophysics Data System (ADS)

    Matejčik, Štefan; Radjenović, Branislav; Klas, Matej; Radmilović-Radjenović, Marija

    2015-11-01

    In this paper results of the experimental and theoretical studies of the field emission driven direct current argon microdischarges for the gaps between 1 μm and 100 μm are presented and discussed. The breakdown voltage curves and Volt-Ampere characteristics proved to be a fertile basis providing better understanding of the breakdown phenomena in microgaps. Based on the measured breakdown voltage curves, the effective yields have been estimated confirming that the secondary electron emission due to high electric field generated in microgaps depends primarily on the electric field leading directly to the violation of the Paschen's law. Experimental data are supported by the theoretical predictions that suggest departure from the scaling law and a flattening of the Paschen curves at higher pressures confirming that Townsend phenomenology breaks down when field emission becomes the key mechanism leading to the breakdown. Field emission of electrons from the cathode, the space charge effects in the breakdown and distinction between the Fowler-Nordheim field emission and the space charge limited current density are also analyzed. Images and Volt-Ampere characteristics recorded at the electrode gap size of 20 μm indicate the existence of a discharge region similar to arc at the pressure of around 200 Torr has been observed. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.

  12. High Energy Neutrino Signals from the Epoch of Reionization

    SciTech Connect

    Iocco, F.; Murase, K.; Nagataki, S.; Serpico, P.D.

    2007-07-06

    In this paper we perform a new estimate of the high energy neutrinos expected from GRBs associated with the first generation of stars in light of new models and constraints on the epoch of reionization and a more detailed evaluation of the neutrino emission yields. We also compare the diffuse high energy neutrino background from Population III stars with the one from ''ordinary stars'' (Population II), as estimated consistently within the same cosmological and astrophysical assumptions. In disagreement with previous literature, we find that high energy neutrinos from Population III stars will not be observable with current or near future neutrino telescopes, falling below both IceCube sensitivity and atmospheric neutrino background under the most extreme assumptions for the GRB rate. This rules them out as a viable diagnostic tool for these still elusive metal-free stars.

  13. Synchronization and stimulated emission in an array of mechanical phase oscillators on a resonant support.

    PubMed

    Mertens, David; Weaver, Richard

    2011-04-01

    Inspired by recent laboratory observations, we propose a mechanical model for eccentrically weighted motors coupled through a vibrating plate. The equations are found to generalize those of Kuramoto to frequency- and position-dependent coupling. The behavior of the model, as determined analytically for no disorder and numerically for systems with and without quenched disorder, shows the key features observed in the laboratory, including hysteresis, bistability, and a spectral gap. The model exhibits stimulated emission and discontinuous lasinglike transitions. PMID:21599284

  14. High energy chemical laser system

    DOEpatents

    Gregg, D.W.; Pearson, R.K.

    1975-12-23

    A high energy chemical laser system is described wherein explosive gaseous mixtures of a reducing agent providing hydrogen isotopes and interhalogen compounds are uniformly ignited by means of an electrical discharge, flash- photolysis or an electron beam. The resulting chemical explosion pumps a lasing chemical species, hydrogen fluoride or deuterium fluoride which is formed in the chemical reaction. The generated lasing pulse has light frequencies in the 3- micron range. Suitable interhalogen compounds include bromine trifluoride (BrF$sub 3$), bromine pentafluoride (BrF$sub 5$), chlorine monofluoride (ClF), chlorine trifluoride (ClF$sub 3$), chlorine pentafluoride (ClF$sub 5$), iodine pentafluoride (IF$sub 5$), and iodine heptafluoride (IF$sub 7$); and suitable reducing agents include hydrogen (H$sub 2$), hydrocarbons such as methane (CH$sub 4$), deuterium (D$sub 2$), and diborane (B$sub 2$H$sub 6$), as well as combinations of the gaseous compound and/or molecular mixtures of the reducing agent.

  15. High Energy Plasma Space Propulsion

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    2000-01-01

    In order to meet NASA's challenge on advanced concept activity in the propulsion area, we initiated a new program entitled "High Energy Plasma Space Propulsion Studies" within the current cooperative agreement in 1998. The goals of this work are to gain further understanding of the engine of the AIMStar spacecraft, a concept which was developed at Penn State University, and to develop a prototype concept for the engine. The AIMStar engine concept was developed at Penn State University several years ago as a hybrid between antimatter and fusion technologies. Because of limited amounts of antimatter available, and concurrently the demonstrated ability for antiprotons to efficiently ignite nuclear fusion reactions, it was felt that this was a very good match. Investigations have been made concerning the performance of the reaction trap. This is a small Penning-like electromagnetic trap, which is used to simultaneously confine antiprotons and fusion fuels. Small DHe3 or DT droplets, containing a few percent molar of a fissile material, are injected into the trap, filled with antiprotons. We have found that it is important to separate the antiprotons into two adjacent wells, to inject he droplet between them and to simultaneously bring the antiprotons to the center of the trap, surrounding the droplet. Our previous concept had the droplet falling onto one cloud of antiprotons. This proved to be inefficient, as the droplet tended to evaporate away from the cloud as it interacted on its surface.

  16. Top Quarks and the High Energy Frontier

    NASA Astrophysics Data System (ADS)

    Canelli, Florencia

    2006-04-01

    One of the still missing pieces of the Standard Model of particle physics is the Higgs boson, providing a mechanism to generate the masses of the particles. Furthermore, there is strong indication that the Standard Model is merely the low energy limit of a more fundamental theory which could manifest itself near the TeV scale. This talk will explore aspects of experimentation at the High Energy frontier, starting from experience at the Tevatron accelerator currently providing the world's highest energy particle collisions. In particular, a precision measurement of the top quark mass using the Collider Detector at Fermilab (CDF) will be presented. An outlook will be given towards a direct search for the Higgs boson and New Physics at the LHC and beyond, concluding with a historic perspective.

  17. Perspectives on high-energy-density physicsa)

    NASA Astrophysics Data System (ADS)

    Drake, R. P.

    2009-05-01

    Much of 21st century plasma physics will involve work to produce, understand, control, and exploit very nontraditional plasmas. High-energy-density (HED) plasmas are often examples, variously involving strong Coulomb interactions and ≪1 particles per Debye sphere, dominant radiation effects, and strongly relativistic or strongly quantum-mechanical behavior. Indeed, these and other modern plasma systems often fall outside the early standard theoretical definitions of "plasma." Here the specific ways in which HED plasmas differ from traditional plasmas are discussed. This is first done by comparison of important physical quantities across the parameter regime accessible by existing or contemplated experimental facilities. A specific discussion of some illustrative cases follows, including strongly radiative shocks and the production of relativistic, quasimonoenergetic beams of accelerated electrons.

  18. Variability in the high energy gamma ray emission from Cyg X-3 over a two-year period (1983 - 1984) at E 4 x 10(11) eV

    NASA Technical Reports Server (NTRS)

    Cawley, M. F.; Fegan, D. J.; Gibbs, K.; Gorham, P. W.; Lamb, R. C.; Liebing, D. F.; Porter, N. A.; Stenger, V. J.; Weekes, T. C.; Williams, R. J.

    1985-01-01

    Cygnus X-3 is observed to emit gamma rays with energies in excess of 4 x 10 to the 11th power eV during two out of 9 observational categories over an 18 month time span. The emissions are observed at the 0.6 phase of the characteristic 4.8 hr light curve for this binary system. We estimate a peak flux at phase 0.6 of 5 x 10 to the minus 10th power photons cm-2s-1 at a software threshold of 8 x 10 to the 11th power eV for Oct/Nov 1983. A flux for the June 84 effect cannot be reliably calculated at present due to lack of Monte Carlo simulations for the energy range and spectral region. For the other 7 observational categories the observations are consistent with zero source emission. The light curve would appear to be variable on a time scale of a couple of weeks at these categories. Selection of compact images in accordance with Monte Carlo simulations combined with empirical optimization techniques have led to an enriched gamma ray light curve for the Oct/Nov 1983 data. Selection on the basis of shower orientation, however, has not led to any notable enhancement of the gamma ray content. Individual Cherenko images can be reliably sorted on an event by event basis into either proton-induced or photon-induced showers.

  19. Photochemical modeling in California with two chemical mechanisms: model intercomparison and response to emission reductions.

    PubMed

    Cai, Chenxia; Kelly, James T; Avise, Jeremy C; Kaduwela, Ajith P; Stockwell, William R

    2011-05-01

    An updated version of the Statewide Air Pollution Research Center (SAPRC) chemical mechanism (SAPRC07C) was implemented into the Community Multiscale Air Quality (CMAQ) version 4.6. CMAQ simulations using SAPRC07C and the previously released version, SAPRC99, were performed and compared for an episode during July-August, 2000. Ozone (O3) predictions of the SAPRC07C simulation are generally lower than those of the SAPRC99 simulation in the key areas of central and southern California, especially in areas where modeled concentrations are greater than the federal 8-hr O3 standard of 75 parts per billion (ppb) and/or when the volatile organic compound (VOC)/nitrogen oxides (NOx) ratio is less than 13. The relative changes of ozone production efficiency (OPE) against the VOC/NOx ratio at 46 sites indicate that the OPE is reduced in SAPRC07C compared with SAPRC99 at most sites by as much as approximately 22%. The SAPRC99 and SAPRC07C mechanisms respond similarly to 20% reductions in anthropogenic VOC emissions. The response of the mechanisms to 20% NOx emissions reductions can be grouped into three cases. In case 1, in which both mechanisms show a decrease in daily maximum 8-hr O3 concentration with decreasing NOx emissions, the O3 decrease in SAPRC07C is smaller. In case 2, in which both mechanisms show an increase in O3 with decreasing NOx emissions, the O3 increase is larger in SAPRC07C. In case 3, SAPRC07C simulates an increase in O3 in response to reduced NOx emissions whereas SAPRC99 simulates a decrease in O3 for the same region. As a result, the areas where NOx controls would be disbeneficial are spatially expanded in SAPRC07C. Although the results presented here are valuable for understanding differences in predictions and model response for SAPRC99 and SAPRC07C, the study did not evaluate the impact of mechanism differences in the context of the U.S. Environmental Protection Agency's guidance for using numerical models in demonstrating air quality attainment

  20. Study of fracture mechanisms of short fiber reinforced AS composite by acoustic emission technique

    SciTech Connect

    Kida, Sotoaki; Suzuki, Megumu

    1995-11-01

    The fracture mechanisms of short fiber reinforced AS composites are studied by acoustic emission technique for examining the effects of fiber contents. The loads P{sub b} and P{sub c} which the damage mechanisms change are obtained at the inflection points of the total AE energy curve the energy gradient method. The damages are generated by fiber breaking at the load point of P{sub b} and P{sub c} in B material, and by the fiber breaking and the debonding between resin and fiber at the load points of P{sub b} and P{sub c} in C material.

  1. Mechanical Modulation of Phonon-Assisted Field Emission in a Silicon Nanomembrane Detector for Time-of-Flight Mass Spectrometry

    PubMed Central

    Park, Jonghoo; Blick, Robert H.

    2016-01-01

    We demonstrate mechanical modulation of phonon-assisted field emission in a free-standing silicon nanomembrane detector for time-of-flight mass spectrometry of proteins. The impacts of ion bombardment on the silicon nanomembrane have been explored in both mechanical and electrical points of view. Locally elevated lattice temperature in the silicon nanomembrane, resulting from the transduction of ion kinetic energy into thermal energy through the ion bombardment, induces not only phonon-assisted field emission but also a mechanical vibration in the silicon nanomembrane. The coupling of these mechanical and electrical phenomenon leads to mechanical modulation of phonon-assisted field emission. The thermal energy relaxation through mechanical vibration in addition to the lateral heat conduction and field emission in the silicon nanomembrane offers effective cooling of the nanomembrane, thereby allowing high resolution mass analysis. PMID:26861329

  2. Mechanical Modulation of Phonon-Assisted Field Emission in a Silicon Nanomembrane Detector for Time-of-Flight Mass Spectrometry.

    PubMed

    Park, Jonghoo; Blick, Robert H

    2016-01-01

    We demonstrate mechanical modulation of phonon-assisted field emission in a free-standing silicon nanomembrane detector for time-of-flight mass spectrometry of proteins. The impacts of ion bombardment on the silicon nanomembrane have been explored in both mechanical and electrical points of view. Locally elevated lattice temperature in the silicon nanomembrane, resulting from the transduction of ion kinetic energy into thermal energy through the ion bombardment, induces not only phonon-assisted field emission but also a mechanical vibration in the silicon nanomembrane. The coupling of these mechanical and electrical phenomenon leads to mechanical modulation of phonon-assisted field emission. The thermal energy relaxation through mechanical vibration in addition to the lateral heat conduction and field emission in the silicon nanomembrane offers effective cooling of the nanomembrane, thereby allowing high resolution mass analysis. PMID:26861329

  3. Biochar suppression of N2O emissions from an agricultural soil: effects and potential mechanisms

    NASA Astrophysics Data System (ADS)

    Case, S. D. C.; Whitaker, J.; McNamara, N. P.; Reay, D. S.

    2012-04-01

    Biochar is biomass that has been heated in a low-oxygen environment to between 350 and 800°C that is subsequently used as a soil amendment. As well as benefits to soil fertility, biochar has potential as a tool to mitigate climate change on a large scale due to its recalcitrance, high carbon content and observed effect of reducing soil greenhouse gas emissions. Previous studies have shown that biochar-amended soil may emit less nitrous oxide (N2O) than soil alone. Our aim was to investigate the effect of fresh, hardwood biochar on N2O emissions from a clay agricultural soil from Lincolnshire, United Kingdom with a combination of field and laboratory studies. We then investigated the mechanism to try to explain the observed suppression of N2O emissions with biochar. In biochar-amended field plots, quarterly greenhouse gas measurements over two years have recorded one occurrence of significant suppression of N2O emissions (80%), with other measurements showing generally low emissions of N2O across all treatments. In laboratory experiments, biochar suppressed N2O emissions following simulated rainfall events in a low-N agricultural soil (72 % suppression), in the same field-moist soil incubated with biochar in the field for 10 months (40 % suppression) and in a relatively high-N soil from a neighbouring field (83 % suppression). We hypothesised that biochar amendment may suppress soil N2O emissions by increasing the water holding capacity (WHC) of the soil, thus rendering the biochar-amended soil less anaerobic compared to control soil at the same gravimetric water content. Water was added to raise soil to the same WHC (87 %) with and without biochar at a range of addition rates. Biochar significantly suppressed N2O emissions with 5 % biochar addition by 67 % and 10 % biochar addition by 98 %. We concluded that the increased WHC of biochar-amended soil could not explain the suppression of N2O emissions. Subsequently, we formulated two hypotheses: (1) that biochar may

  4. Very-high-energy blazars: A broad(band) perspective

    NASA Astrophysics Data System (ADS)

    Furniss, Amy Kathryn

    Very high energy (VHE; E ≥ 100 GeV) blazars are a type of active galaxy detected above 100 GeV with a jet pointed toward the observer. This work investigates VHE blazars through broadband observations, starting with a description of the VHE-discovery and time-independent modeling of the non-thermal emission from RX J0648.7+1516. Additionally, synchrotron self-Compton models are applied to six non-VHE blazars, with the VHE flux of each blazar being constrained by non-detection during observation by VERITAS. The general lack of physical measurements of model parameters is highlighted and a scheme of supplementary observations involving millimeter carbon monoxide (CO) luminosity and soft X-ray absorption measurements is explored for three VHE blazars. The limited sample supports a possible connection between the existence of CO in the vicinity of the blazar and additional soft X-ray absorption beyond what can be attributed to the Milky Way. RGB J0710+590 and W Comae both lack a significant level of CO and do not require additional absorption for the description of the soft X-ray emission as observed by Swift XRT. 1ES 1959+650, on the other hand, shows a significant level of CO in the vicinity of the blazar and requires additional absorption to describe the soft X-ray emission. The positive detection of CO in the vicinity of 1ES 1959+650 is used as motivation to apply a mirrored emission scenario to broadband variability data. Limits on the redshifts of the two VHE blazars 3C 66A and PKS 1424+240 are derived from HST/COS observations of intervening Lyman absorption. These observations show 3C 66A to reside at a redshift below the tentative z = 0.444 at 99.9% confidence and reveal PKS 1424+240 to be the most distant VHE-detected blazar thus far. The redshift information is paired with VERITAS and Fermi Large Area Telescope gamma-ray observations to probe the density of the extragalactic background light and correct the observed gamma-ray spectra to the intrinsically

  5. A radio view of high-energy emitting AGNs

    NASA Astrophysics Data System (ADS)

    Schulz, Robert Frank

    2016-07-01

    Active galactic nuclei (AGNs) are among the most energetic objects in the Universe. These galaxies that are dominated in part or even throughout the electromagnetic spectrum by emission from their central, compact region. AGNs are extensively studied by multi-wavelength observations. In the standard picture, the main driver of an AGN is a supermassive black hole (SMBH) in its centre that is surrounded by an accretion disk. Perpendicular to the disk, in the vicinity of highly magnetized SMBH relativistic outflows of plasma, so-called jets, can form on either side that can reach far beyond the host galaxy. Only about 10% of all AGNs are dominated by emission from these jets due to relativistic beaming effects and these so-called blazars dominate the extragalactic gamma-ray sky. It is commonly accepted that the low-energy emission (radio to UV/X-ray) is due to synchrotron emission from the jet. The high-energy emission is considered to stem from inverse-Compton scattering of photons on the jet particles, but different sources for these photons are discussed (internal or external to the AGN) and other models for the high-energy emission have also been proposed. The nature of the high-energy emission is strongly linked to the location of the emission region in the jet which requires a detailed understanding of the formation and evolution of jets. Radio observations especially using very long baseline interferometry (VLBI) provide the best way to gain direct information on the intrinsic properties of jets down to sub-pc scales, close to their formation region. In this thesis, I focus on the properties of three different AGNs, IC 310, PKS2004-447, and 3C 111 that belong to the small non-blazar population of gamma-ray-loud AGNs. I study them in detail with a variety of radio astronomical instruments with respect to their high-energy emission and in the context of the large monitoring programmes MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) and

  6. Dust emission mechanisms in the central Sahara: new insights from remote field observations

    NASA Astrophysics Data System (ADS)

    Allen, C.; Washington, R.; Engelstaedter, S.

    2013-12-01

    North Africa is the world's largest source of mineral aerosol (dust). The Fennec Project, an international consortium led by the University of Oxford, is the first project to systematically instrument the remote central Sahara Desert. These observations have, among others, provided new insights into the atmospheric mechanisms of dust emission. Bordj Badji Mokhtar, in south-west Algeria, is within kilometres of the centre of the global mean summer dust maximum. The site, operated by Fennec partners ONM Algerie, has been heavily instrumented since summer 2011. During the Intensive Observation Period (IOP) in June 2011, four main emission mechanisms were observed and documented: cold pool outflows, low level jets (LLJs), monsoon surges and dry convective plumes. Establishing the relative importance of dust emission mechanisms has been a long-standing research goal. A detailed partitioning exercise of dust events during the IOP shows that 45% of the dust over BBM was generated by local emission in cold pool outflows, 14% by LLJs and only 2% by dry convective plumes. 27% of the dust was advected to the site rather than locally emitted and 12% of the dust was residual or ';background' dust. The work shows the primacy of cold pool outflows for dust emission in the region and also the important contribution of dust advection. In accordance with long-held ideas, the cube of wind speed is strongly correlated with dust emission. Surprisingly however, particles in long-range advection (>500km) were found to be larger than locally emitted dust. Although a clear LLJ wind structure is evident in the mean diurnal cycle during the IOP (12m/s peak winds at 935hPa between 04-05h), LLJs are only responsible for a relatively small amount of dust emission. There is significant daily variability in LLJ strength; the strongest winds are produced by a relatively small number of events. The position and strength of the Saharan Heat Low is strongly associated with the development (or

  7. High energy hadron-hadron collisions

    SciTech Connect

    Chou, T.T.

    1990-11-01

    Results of a study on high energy collision with the geometrical model are summarized in three parts: (i) the elastic hadron-hadron collision, (ii) the inelastic hadron-hadron collision, and (iii) the e{sup +}e{sup {minus}} annihilation. For elastic collisions, a simple expression for the proton matter distribution is proposed which fits well the elastic {bar p}p scattering from ISR to S{bar p}pS energies within the geometrical model. The proton form factor is of the dipole form with an energy-dependent range parameter. The {bar p}p elastic differential cross section at Tevatron energies obtained by extrapolation is in good agreement with experiments. For multiparticle emission processes a unified physical picture for hadron-hadron and e{sup +}e{sup {minus}} collisions was proposed. A number of predictions were made, including the one that KNO-scaling does not obtain for e{sup +}e{sup {minus}} two-jet events. An extension of the considerations within the geometrical model led to a theory of the momentum distributions of the outgoing particles which are found in good agreement with current experimental data. Extrapolations of results to higher energies have been made. The cluster size of hadrons produced in e{sup +}e{sup {minus}} annihilation is found to increase slowly with energy.

  8. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Yuiko T.; Guesto-Barnak, Donna

    1992-01-01

    A low-or no-silica, low- or no-alkali phosphate glass useful as a laser amplifier in a multiple pass, high energy laser system having a high thermal conductivity, K.sub.90.degree. C. >0.85 W/mK, a low coefficient of thermal expansion, .alpha..sub.20.degree.-300.degree. C. <80.times.10.sup.-7 /.degree.C., low emission cross section, .sigma.<2.5.times.10.sup.-20 cm.sup.2, and a high fluorescence lifetime, .tau.>325 .mu.secs at 3 wt. % Nd doping, consisting essentially of (on an oxide composition basis): wherein Ln.sub.2 O.sub.3 is the sum of lanthanide oxides; .SIGMA.R.sub.2 O is <5, R being Li, Na, K, Cs, and Rb; the sum of Al.sub.2 O.sub.3 and MgO is <24 unless .SIGMA.R.sub.2 O is 0, then the sum of Al.sub.2 O.sub.3 and MgO is <42; and the ratio of MgO to B.sub.2 O.sub.3 is 0.48-4.20.

  9. High Energy Electron Detectors on Sphinx

    NASA Astrophysics Data System (ADS)

    Thompson, J. R.; Porte, A.; Zucchini, F.; Calamy, H.; Auriel, G.; Coleman, P. L.; Bayol, F.; Lalle, B.; Krishnan, M.; Wilson, K.

    2008-11-01

    Z-pinch plasma radiation sources are used to dose test objects with K-shell (˜1-4keV) x-rays. The implosion physics can produce high energy electrons (> 50keV), which could distort interpretation of the soft x-ray effects. We describe the design and implementation of a diagnostic suite to characterize the electron environment of Al wire and Ar gas puff z-pinches on Sphinx. The design used ITS calculations to model detector response to both soft x-rays and electrons and help set upper bounds to the spurious electron flux. Strategies to discriminate between the known soft x-ray emission and the suspected electron flux will be discussed. H.Calamy et al, ``Use of microsecond current prepulse for dramatic improvements of wire array Z-pinch implosion,'' Phys Plasmas 15, 012701 (2008) J.A.Halbleib et al, ``ITS: the integrated TIGER series of electron/photon transport codes-Version 3.0,'' IEEE Trans on Nuclear Sci, 39, 1025 (1992)

  10. Three Decades of High Energy Transients

    NASA Technical Reports Server (NTRS)

    Kouveliotou, Chryssa

    2012-01-01

    Gamma-Ray Bursts are the most brilliant explosions in space. The first GRB was discovered on 1967, just over 40 years ago. It took several years and multiple generations of space and ground instruments to unravel some of the mysteries of this phenomenon. However, many questions remain open today. I will discuss the history, evolution and current status of the GRB field and its contributions in our understanding of the transient high energy sky. Finally, I will describe how GRBs can be utilized in future missions as tools, to probe the cosmic chemical evolution of the Universe Magnetars are magnetically powered rotating neutron stars with extreme magnetic fields (over 10(exp 14) Gauss). They were discovered in the X- and gamma-rays where they predominantly emit their radiation. Very few sources (roughly 24) have been found since their discovery in 1987. NASA's Fermi Gamma-ray Space Telescope was launched June 11, 2009; since then the Fermi Gamma-ray Burst Monitor (GBM) recorded emission from several magnetar sources. In total, six new sources were discovered between 2008 and 2011, with a synergy between Swift, RXTE, Fermi and the Interplanetary Network (IPN). I will give a short history of magnetars and describe how this, once relatively esoteric field, has emerged as a link between several astrophysical areas including Gamma-Ray Bursts.

  11. Angular correlations in gluon production at high energy

    SciTech Connect

    Kovner, Alex; Lublinsky, Michael

    2011-02-01

    We present a general, model independent argument demonstrating that gluons produced in high energy hadronic collision are necessarily correlated in rapidity and also in the emission angle. The strength of the correlation depends on the process and on the structure/model of the colliding particles. In particular we argue that it is strongly affected (and underestimated) by factorized approximations frequently used to quantify the effect.

  12. Sonoluminescence in Space: The Critical Role of Buoyancy in Stability and Emission Mechanisms

    NASA Technical Reports Server (NTRS)

    Thomas, Charles R.; Holt, R. Glynn; Roy, Ronald A.

    2002-01-01

    Sonoluminescence is the term used to describe the emission of light from a violently collapsing bubble. Sonoluminescence ("light from sound") is the result of extremely nonlinear pulsations of gas/vapor bubbles in liquids when subject to sufficiently high amplitude acoustic pressures. In a single collapse, a bubble's volume can be compressed more than a thousand-fold in the span of less than a microsecond. Even the simplest consideration of the thermodynamics yields pressures on the order of 10,000 ATM, and temperatures of at least 10,000K. On the face of things, it is not surprising that light should be emitted from such an extreme process. Since 1990 (the year that Gaitan discovered light from a single bubble) there has been a tremendous amount of experimental and theoretical research in stable, single-bubble sonoluminescence (SBSL), yet there remain at least four unexplained phenomena associated with SBSL in 1g: the light emission mechanism itself, the existence of anisotropies in the emitted light, the disappearance of the bubble at some critical acoustic pressure, and the appearance of quasiperiodic and chaotic oscillations in the flash timing. Gravity, in the context of the buoyant force, is implicated in all four of these. We are developing KC-135 experiments probing the effect of gravity on single bubble sonoluminescence. By determining the stability boundaries experimentally in microgravity, and measuring not only light emission but mechanical bubble response, we will be able to directly test the predictions of existing theories.

  13. Comparative analysis of scintillation characteristics derived from different emission mechanisms in BaCl2

    NASA Astrophysics Data System (ADS)

    Fukabori, Akihiro

    2015-04-01

    Crack-free La3+-substituted BaCl2 single crystals without and with Eu2+ as an activator were successfully grown using the micro-pulling-down method. Luminescence bands from BaCl2 without and with the Eu2+ activator were assigned as mainly intrinsic and extrinsic, respectively. Therefore, BaCl2 as a host material is suitable for investigating the effects of the emission mechanism on the non-proportionality curves and energy resolution plots. First, the scintillation characteristics of BaCl2:La3+(11 at. %) and BaCl2:La3+(7.7 at. %):Eu2+(0.5 at. %) single crystals were determined along with those of BaCl2 and BaCl2:Eu2+(0.5 at. %) crystals. Second, the non-proportionality curves from the different emission origins in BaCl2 were confirmed to be consistent with phenomenological models. Third, the non-proportionality curves and energy resolution plots originating from intrinsic (without Eu2+) and extrinsic (with Eu2+) luminescence were compared. The results experimentally demonstrated that the emission mechanism influenced scintillator non-proportionality curves.

  14. Terrestrial Effects of High Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Atri, Dimitra

    2011-01-01

    On geological timescales, the Earth is likely to be exposed to an increased flux of high energy cosmic rays (HECRs) from astrophysical sources such as nearby supernovae, gamma ray bursts or by galactic shocks. These high-energy particles strike the Earth's atmosphere initiating an extensive air shower. As the air shower propagates deeper, it ionizes the atmosphere by producing charged secondary particles. Increased ionization could lead to changes in atmospheric chemistry, resulting in ozone depletion. This could increase the flux of solar UVB radiation at the surface, which is potentially harmful to living organisms. Increased ionization affects the global electrical circuit can could possibly enhance the low-altitude cloud formation rate. Secondary particles such as muons and thermal neutrons produced as a result of nuclear interactions are able to reach the ground, enhancing the biological radiation dose. The muon flux dominates radiation dose from cosmic rays causing DNA damage and increase in the mutation rates, which can have serious biological implications for terrestrial and sub-terrestrial life. This radiation dose is an important constraint on the habitability of a planet. Using CORSIKA, we perform massive computer simulations and construct lookup tables from 10 GeV - 1 PeV primaries (1 PeV - 0.1 ZeV in progress), which can be used to quantify these effects. These tables are freely available to the community and can be used for other studies, not necessarily relevant to Astrobiology. We use these tables to study the terrestrial implications of galactic shock generated by the infall of our galaxy toward the Virgo cluster. This could be a possible mechanism explaining the observed periodicity in biodiversity in paleobiology databases.

  15. Terrestrial effects of high energy cosmic rays

    NASA Astrophysics Data System (ADS)

    Atri, Dimitra

    On geological timescales, the Earth is likely to be exposed to higher than the usual flux of high energy cosmic rays (HECRs) from astrophysical sources such as nearby supernovae, gamma ray bursts or by galactic shocks. These high-energy particles strike the Earth's atmosphere, initiating an extensive air shower. As the air shower propagates deeper, it ionizes the atmosphere by producing charged secondary particles and photons. Increased ionization leads to changes in atmospheric chemistry, resulting in ozone depletion. This increases the flux of solar UVB radiation at the surface, which is potentially harmful to living organisms. Increased ionization affects the global electrical circuit, which could enhance the low-altitude cloud formation rate. Secondary particles such as muons and thermal neutrons produced as a result of hadronic interactions of the primary cosmic rays with the atmosphere are able to reach the ground, enhancing the biological radiation dose. The muon flux dominates the radiation dose from cosmic rays causing damage to DNA and an increase in mutation rates and cancer, which can have serious biological implications for surface and sub-surface life. Using CORSIKA, we perform massive computer simulations and construct lookup tables for 10 GeV - 1 PeV primaries, which can be used to quantify these effects from enhanced cosmic ray exposure to any astrophysical source. These tables are freely available to the community and can be used for other studies. We use these tables to study the terrestrial implications of galactic shock generated by the infall of our galaxy toward the Virgo cluster. Increased radiation dose from muons could be a possible mechanism explaining the observed periodicity in biodiversity in paleobiology databases.

  16. Theory of high-energy messengers

    NASA Astrophysics Data System (ADS)

    Dermer, Charles D.

    2016-05-01

    Knowledge of the distant high-energy universe comes from photons, ultra-high energy cosmic rays (UHECRs), high-energy neutrinos, and gravitational waves. The theory of high-energy messengers reviewed here focuses on the extragalactic background light at all wavelengths, cosmic rays and magnetic fields in intergalactic space, and neutrinos of extragalactic origin. Comparisons are drawn between the intensities of photons and UHECRs in intergalactic space, and the high-energy neutrinos recently detected with IceCube at about the Waxman-Bahcall flux. Source candidates for UHECRs and high-energy neutrinos are reviewed, focusing on star-forming and radio-loud active galaxies. HAWC and Advanced LIGO are just underway, with much anticipation.

  17. Linking acoustic emission signatures with grain-scale mechanical interactions during granular shearing

    NASA Astrophysics Data System (ADS)

    Michlmayr, G.; Cohen, D.; Or, D.

    2012-04-01

    Acoustic Emissions (AE) are high frequency (kHz range) elastic body waves, generated in deforming granular material during particle collisions, frictional slip, or other types of abrupt grain-scale mechanical interactions. The direct link with particle micro-mechanics makes AE a useful tool for gaining insights into mechanical aspects of progressive shear failure in granular material and slow granular flows. The formation of shear plane in granular matter involves numerous internal restructuring and failure events with distinct dynamics resembling features of critical phase transition. Following establishment of a shear plane, subsequent deformation involves episodic slip events interrupted by arrested flow (stick-slip behavior). We developed a model for interpreting measured AE signatures in terms of micro-failures during progressive granular shear a considering AE generation mechanisms and propagation of acoustic signals within granular material. Results from shear frame experiments include information on strains, stresses and acoustic emissions during deformation controlled tests on glass beads and sand. The number of failure associated AE event rates peaks with maximum shear resistance of the granular material. Intermittent slip events during stick-slip deformation are found to be closely related to low frequency AE events (~1kHz). Statistics of AE events and their temporal development are reproduced using a simple fiber-bundle model. A conceptual AE generation and propagation model accounts for conversion of mechanical events into elastic waves. In addition to gaining insights concerning grain-scale mechanical interactions, the AE method offers a useful tool for monitoring hazardous geologic mass movements, such as landslides, rock avalanches or debris flows.

  18. UV-radiation-induced electron emission by hormones. Hypothesis for specific communication mechanisms

    NASA Astrophysics Data System (ADS)

    Getoff, Nikola

    2009-11-01

    The highlights of recently observed electron emission from electronically excited sexual hormones (17β-estradiol, progesterone, testosterone) and the phytohormone genistein in polar media are briefly reviewed. The electron yield, Q(e aq-), dependence from substrate concentration, hormone structure, polarity of solvent, absorbed energy and temperature are discussed. The hormones reactivity with e aq- and efficiency in electron transfer ensure them the ability to communicate with other biological systems in an organism. A hypothesis is presented for the explanation of the mechanisms of the distinct recognition of signals transmitted by electrons, originating from different types of hormones to receiving centres. Biological consequences of the electron emission in respect to cancer are mentioned.

  19. Generation Mechanisms UV and X-ray Emissions During SL9 Impact

    NASA Technical Reports Server (NTRS)

    Waite, J. Hunter, Jr.

    1997-01-01

    The purpose of this grant was to study the ultraviolet and X-ray emissions associated with the impact of comet Shoemaker-Levy 9 with Jupiter. The University of Michigan task was primarily focused on theoretical calculations. The NAGW-4788 subtask was to be largely devoted to determining the constraints placed by the X-ray observations on the physical mechanisms responsible for the generation of the X-rays. Author summarized below the ROSAT observations and suggest a physical mechanism that can plausibly account for the observed emissions. It is hoped that the full set of activities can be completed at a later date. Further analysis of the ROSAT data acquired at the time of the impact was necessary to define the observational constraints on the magnetospheric-ionospheric processes involved in the excitation of the X-ray emissions associated with the fragment impacts. This analysis centered around improvements in the pointing accuracy and improvements in the timing information. Additional pointing information was made possible by the identification of the optical counterparts to the X-ray sources in the ROSAT field-of-view. Due to the large number of worldwide observers of the impacts, a serendipitous visible plate image from an observer in Venezuela provided a very accurate location of the present position of the X-ray source, virtually eliminating pointing errors in the data. Once refined, the pointing indicated that the two observed X-ray brightenings that were highly correlated in time with the K and P2 events were brightenings of the X-ray aurora (as identified in images prior to the impact).Appendix A "ROSAT observations of X-ray emissions from Jupiter during the impact of comet Shoemaker-Levy 9' also included.

  20. High-Energy Astrophysics: An Overview

    NASA Technical Reports Server (NTRS)

    Fishman, Gerald J.

    2007-01-01

    High-energy astrophysics is the study of objects and phenomena in space with energy densities much greater than that found in normal stars and galaxies. These include black holes, neutron stars, cosmic rays, hypernovae and gamma-ray bursts. A history and an overview of high-energy astrophysics will be presented, including a description of the objects that are observed. Observing techniques, space-borne missions in high-energy astrophysics and some recent discoveries will also be described. Several entirely new types of astronomy are being employed in high-energy astrophysics. These will be briefly described, along with some NASA missions currently under development.

  1. Two Emission Mechanisms in the Fermi Bubbles: A Possible Signal of Annihilating Dark Matter

    SciTech Connect

    Hooper, Dan; Slatyer, Tracy R.

    2013-09-01

    We study the variation of the spectrum of the Fermi Bubbles with Galactic latitude. Far from the Galactic plane (|b| > 30 degrees), the observed gamma-ray emission is nearly invariant with latitude, and is consistent with arising from inverse Compton scattering of the interstellar radiation field by cosmic-ray electrons with an approximately power-law spectrum. The same electrons in the presence of microgauss-scale magnetic fields can also generate the the observed microwave "haze". At lower latitudes (b < 20 degrees), in contrast, the spectrum of the emission correlated with the Bubbles possesses a pronounced spectral feature peaking at 1-4 GeV (in E^2 dN/dE) which cannot be generated by any realistic spectrum of electrons. Instead, we conclude that a second (non-inverse-Compton) emission mechanism must be responsible for the bulk of the low-energy, low-latitude emission. This second component is spectrally similar to the excess GeV emission previously reported from the Galactic Center (GC), and also appears spatially consistent with a luminosity per volume falling approximately as r^-2.4, where r is the distance from the GC. We argue that the spectral feature visible in the low-latitude Bubbles is the extended counterpart of the GC excess, now detected out to at least 2-3 kpc from the GC. The spectrum and angular distribution of the signal is consistent with that predicted from ~10 GeV dark matter particles annihilating to leptons, or from ~50 GeV dark matter particles annihilating to quarks, following a distribution similar to the canonical Navarro-Frenk-White (NFW) profile. We also consider millisecond pulsars as a possible astrophysical explanation for the signal, as observed millisecond pulsars possess a spectral cutoff at approximately the required energy. Any such scenario would require a large population of unresolved millisecond pulsars extending at least 2-3 kpc from the GC.

  2. Mapping the subcellular mechanical properties of live cells in tissues with fluorescence emission-Brillouin imaging.

    PubMed

    Elsayad, Kareem; Werner, Stephanie; Gallemí, Marçal; Kong, Jixiang; Sánchez Guajardo, Edmundo R; Zhang, Lijuan; Jaillais, Yvon; Greb, Thomas; Belkhadir, Youssef

    2016-01-01

    Extracellular matrices (ECMs) are central to the advent of multicellular life, and their mechanical properties are modulated by and impinge on intracellular signaling pathways that regulate vital cellular functions. High spatial-resolution mapping of mechanical properties in live cells is, however, extremely challenging. Thus, our understanding of how signaling pathways process physiological signals to generate appropriate mechanical responses is limited. We introduce fluorescence emission-Brillouin scattering imaging (FBi), a method for the parallel and all-optical measurements of mechanical properties and fluorescence at the submicrometer scale in living organisms. Using FBi, we showed that changes in cellular hydrostatic pressure and cytoplasm viscoelasticity modulate the mechanical signatures of plant ECMs. We further established that the measured "stiffness" of plant ECMs is symmetrically patterned in hypocotyl cells undergoing directional growth. Finally, application of this method to Arabidopsis thaliana with photoreceptor mutants revealed that red and far-red light signals are essential modulators of ECM viscoelasticity. By mapping the viscoelastic signatures of a complex ECM, we provide proof of principle for the organism-wide applicability of FBi for measuring the mechanical outputs of intracellular signaling pathways. As such, our work has implications for investigations of mechanosignaling pathways and developmental biology. PMID:27382028

  3. High energy decomposition of halogenated hydrocarbons

    SciTech Connect

    Mincher, B.J.; Arbon, R.E.; Meikrantz, D.H.

    1992-09-01

    This program is the INEL component of a joint collaborative effort with Lawrence Livermore National Laboratory (LLNL). Purpose is to demonstrate a viable process for breaking down hazardous halogenated organic wastes to simpler, nonhazardous wastes using high energy ionizing radiation. The INEL effort focuses on the use of spent reactor fuel gamma radiation sources to decompose complex wastes such as PCBS. Work in FY92 expanded upon that reported for FY91. During FY91 it was reported that PCBs were susceptible to radiolytic decomposition in alcoholic solution, but that only a small percentage of decomposition products could be accounted for. It was shown that decomposition was more efficient in methanol than in isopropanol and that the presence of a copper-zinc couple catalyst did not affect the reaction rate. Major goals of FY92 work were to determine the reaction mechanism, to identify further reaction products, and to select a more appropriate catalyst. Described in this report are results of mechanism specific experiments, mass balance studies, transformer oil irradiations, the use of hydrogen peroxide as a potential catalyst, and the irradiation of pure PCB crystals in the absence of diluent.

  4. Roles of the Major, Small, Acid-Soluble Spore Proteins and Spore-Specific and Universal DNA Repair Mechanisms in Resistance of Bacillus subtilis Spores to Ionizing Radiation from X Rays and High-Energy Charged-Particle Bombardment▿

    PubMed Central

    Moeller, Ralf; Setlow, Peter; Horneck, Gerda; Berger, Thomas; Reitz, Günther; Rettberg, Petra; Doherty, Aidan J.; Okayasu, Ryuichi; Nicholson, Wayne L.

    2008-01-01

    The role of DNA repair by nonhomologous end joining (NHEJ), homologous recombination, spore photoproduct lyase, and DNA polymerase I and genome protection via α/β-type small, acid-soluble spore proteins (SASP) in Bacillus subtilis spore resistance to accelerated heavy ions (high-energy charged [HZE] particles) and X rays has been studied. Spores deficient in NHEJ and α/β-type SASP were significantly more sensitive to HZE particle bombardment and X-ray irradiation than were the recA, polA, and splB mutant and wild-type spores, indicating that NHEJ provides an efficient DNA double-strand break repair pathway during spore germination and that the loss of the α/β-type SASP leads to a significant radiosensitivity to ionizing radiation, suggesting the essential function of these spore proteins as protectants of spore DNA against ionizing radiation. PMID:18055591

  5. Consideration on the Mechanism of Microwave Emission Due to Rock Fracture

    NASA Astrophysics Data System (ADS)

    Takano, Tadashi; Sugita, Seiji; Yoshida, Shingo; Maeda, Takashi

    2010-05-01

    Microwave emission due to rock fracture was found at 300 MHz, 2 GHz, and 22 GHz, and its power was calibrated in laboratory for the first time in the world. The observed waveform is impulsive, and contains correspondent frequency component inside the envelope at each frequency band. At such high frequencies, the electro-magnetic signal power can be calibrated as a radiating wave with high accuracy. Accordingly, it was verified that a substantial power is emitted. The microwave emission phenomena were also observed on occasions of hypervelocity impact, and esteemed as phenomena generally associated with material destruction. Earthquakes and volcanic activities are association with rock fractures so that the microwave is expected to be emitted. Actually, the e emission was confirmed by the data analysis of the brightness temperature obtained by a remote sensing satellite, which flew over great earthquakes of Wuenchan and Sumatra, and great volcanic eruptions of Reventador and Chanten. It is important to show the microwave emission during rock fracture in natural phenomena. Therefore, the field test to detect the microwave due to the collapse of a crater cliff was planned and persecuted at the volcano of Miyake-jima about 100 km south of Tokyo. Volcanic activity may be more convenient than an earthquake because of the known location and time. As a result, they observed the microwave emission which was strongly correlated with the cliff collapses. Despite of the above-mentioned phenomenological fruits, the reason of the microwave emission is not fixed yet. We have investigated the mechanism of the emission in consideration of the obtained data in rock fracture experiments so far and the study results on material destruction by hypervelocity impact. This paper presents the proposal of the hypothesis and resultant discussions. The microwave sensors may be useful to monitor natural hazards such as an earthquake or a volcanic eruption, because the microwave due to rock

  6. Sonoluminescence in Space: The Critical Role of Buoyancy in Stability and Emission Mechanisms

    NASA Technical Reports Server (NTRS)

    Holt, R. Glynn; Roy, Ronald A.

    1999-01-01

    Sonoluminescence is the term used to describe the emission of light from a violently collapsing bubble. Sonoluminescence ("light from sound") is the result of extremely nonlinear pulsations of gas/vapor bubbles in liquids when subject to sufficiently high amplitude acoustic pressures. In a single collapse, a bubble's volume can be compressed more than a thousand-fold in the span of less than a microsecond. Even the simplest consideration of the thermodynamics yields pressures on the order of 10,000 ATM. and temperatures of at least 10,000 K. On the face of things, it is not surprising that light should be emitted from such an extreme process. Since 1990 (the year that Gaitan discovered light from a single bubble) there has been a tremendous amount of experimental and theoretical research in stable, single-bubble sonoluminescence. Yet there remain four fundamental mysteries associated with this phenomenon: 1) the light emission mechanism itself; 2) the mechanism for anomalous mass flux stability; 3) the disappearance of the bubble at some critical acoustic pressure; and 4) the appearance of quasiperiodic and chaotic oscillations in the flash timing. Gravity, in the context of the buoyant force, is implicated in all four of these unexplained phenomena. We are developing microgravity experiments probing the effect of gravity on single bubble sonoluminescence. By determining the stability boundaries experimentally in microgravity, and measuring not only light emission but mechanical bubble response, we will be able to directly test the unambiguous predictions of existing theories. By exploiting the microgravity environment we will gain new knowledge impossible to obtain in earth-based labs which will enable explanations for the above mysteries. We will also be in a position to make new discoveries about bubbles which emit light.

  7. Educing the emission mechanism of internal gravity waves in the differentially heat rotating annulus

    NASA Astrophysics Data System (ADS)

    Rolland, Joran; Hien, Steffen; Achatz, Ulrich; Borchert, Sebastian; Fruman, Mark

    2016-04-01

    Understanding the lifecycle of gravity waves is fundamental to a good comprehension of the dynamics of the atmosphere. In this lifecycle, the emission mechanisms may be the most elusive. Indeed, while the emission of gravity waves by orography or convection is well understood, the so-called spontaneous emission is still a quite open topic of investigation [1]. This type of emission usually occur very near jet-front systems in the troposphere. In this abstract, we announce our numerical study of the question. Model systems of the atmosphere which can be easily simulated or built in a laboratory have always been an important part of the study of atmospheric dynamics, alongside global simulations, in situ measurements and theory. In the case of the study of the spontaneous emission of gravity waves near jet-front systems, the differentially heated rotating annulus set up has been proposed and extensively used. It comprises of an annular tank containing water: the inner cylinder is kept at a cold temperature while the outer cylinder is kept at a warm temperature. The whole system is rotating. Provided the values of the control parameters (temperature, rotation rate, gap between the cylinders, height of water) are well chosen, the resulting flow mimics the troposphere at midlatitudes: it has a jet stream, and a baroclinic lifecycle develops on top of it. A very reasonable ratio of Brunt-Väisälä frequency over rotation rate of the system can be obtained, so as to be as close to the atmosphere as possible. Recent experiments as well as earlier numerical simulations in our research group have shown that gravity waves are indeed emitted in this set up, in particular near the jet front system of the baroclinic wave [2]. After a first experimental stage of characterising the emitted wavepacket, we focused our work on testing hypotheses on the gravity wave emission mechanism: we have tested and validated the hypothesis of spontaneous imbalance generated by the flow in

  8. High-energy diffraction microscopy at the advanced photon source

    SciTech Connect

    Lienert, U.; Li, S.; Hefferan, C.; Lind, J.; Suter, R.; Bernier, J.; Barton, N.; Brandes, M.; Mills, M.; Miller, M.; Jakobsen, B.; Pantleon, W.

    2012-02-28

    The status of the High Energy Diffraction Microscopy (HEDM) program at the 1-ID beam line of the Advanced Photon Source is reported. HEDM applies high energy synchrotron radiation for the grain and sub-grain scale structural and mechanical characterization of polycrystalline bulk materials in situ during thermomechanical loading. Case studies demonstrate the mapping of grain boundary topology, the evaluation of stress tensors of individual grains during tensile deformation and comparison to a finite element modeling simulation, and the characterization of evolving dislocation structure. Complementary information is obtained by post mortem electron microscopy on the same sample volume previously investigated by HEDM.

  9. Monitoring of Temperature Fatigue Failure Mechanism for Polyvinyl Alcohol Fiber Concrete Using Acoustic Emission Sensors

    PubMed Central

    Li, Dongsheng; Cao, Hai

    2012-01-01

    The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed. PMID:23012555

  10. High energy interactions of cosmic ray particles

    NASA Technical Reports Server (NTRS)

    Jones, L. W.

    1986-01-01

    The highlights of seven sessions of the Conference dealing with high energy interactions of cosmic rays are discussed. High energy cross section measurements; particle production-models of experiments; nuclei and nuclear matter; nucleus-nucleus collision; searches for magnetic monopoles; and studies of nucleon decay are covered.

  11. GEANT4: Applications in High Energy Physics

    SciTech Connect

    Mahmood, Tariq; Zafar, Abrar Ahmed; Hussain, Talib; Rashid, Haris

    2007-02-14

    GEANT4 is a detector simulation toolkit aimed at studying, mainly experimental high energy physics. In this paper we will give an overview of this software with special reference to its applications in high energy physics experiments. A brief of process methods is given. Object-oriented nature of the simulation toolkit is highlighted.

  12. Emission enhancement mechanism of GaN:Eu by Mg codoping

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Hiroto; Takagi, Yasufumi; Otani, Tatsuki; Okada, Hiroshi; Wakahara, Akihiro

    2013-01-01

    Mg codoping into Eu-doped GaN strongly affects the two dominant optical sites A (620.3 nm) and B (622.3 nm) and dramatically improves the optical characteristics obtained from Eu3+ ions. To clarify the mechanism of the enhanced emission, the effects of the Mg concentration on the excitation and emission processes were evaluated by considering the excitation power dependence of photoluminescence (PL) and time-resolved PL at various temperatures. The excitation cross section σex, which reflected the excitation process, did not depend on the Mg concentration but strongly on the optical site, which was attributed to the different energy transfer processes of the two optical sites. σex for site A was three times larger than that for site B, indicating higher excitation efficiency for site A. Mg codoping dramatically increased the number of Eu ions in site A that remain active at room temperature (RT) and the 5D0 lifetime at RT, indicating the suppression of nonradiative components during the emission process. Therefore, the optical properties were markedly enhanced by Mg codoping.

  13. Distortion product otoacoustic emissions provide clues to hearing mechanisms in the frog

    NASA Astrophysics Data System (ADS)

    Vassilakis, Pantelis; Narins, Peter M.

    2003-10-01

    Cubic distortion product otoacoustic emissions (DPOAEs) were recorded from 10 Rana pipiens and 10 Rana catesbeiana, 5 males and 5 females each. The I/O curves obtained from the amphibian papilla (AP) of both species are very similar to the respective mammalian curves, indicating that, like in the mammalian cochlea, there may be an amplification process active in the frog AP. The DPOAE level dependence on primary levels is also similar to the mammalian case, suggesting a mechanical structure in the frog inner ear may be functioning analogously to the mammalian basilar membrane. DPOAE audiograms were obtained for primary frequencies spanning the animals hearing range and levels determined by the previous experiments. R. catesbeiana produce stronger emissions than R. pipiens and, consistent with previously reported sexual dimorphism in the mammalian and anuran auditory systems, females from both species produce stronger emissions than males. Additionally, the 2f1-f2 DPOAE is generated primarily at the DPOAE frequency place, while the 2f2-f1 DPOAE is generated primarily at a frequency place between the primaries. This difference in mammalian and frog DPOAEs may be linked to an anatomical difference that results in the acoustic energy following opposite paths through the mammalian and frog inner ears. [Work supported by NIH Grant No. DC-00222 to Peter M. Narins.] a)Currently at De Paul Univ., School of Music, Chicago, IL 60614.

  14. Volatile organic compound emission rates from mechanical surface aerators: Mass-transfer modeling

    SciTech Connect

    Chern, J.M.; Chou, S.R.

    1999-08-01

    In wastewater treatment plants, many operation units such as equalization and aeration involve oxygen transfer between wastewater and air. While oxygen is transferred from air to wastewater, volatile organic compounds (VOCs) are stripped from wastewater to air. Because of increasingly stringent environmental regulations, wastewater treatment operators have to do VOC inventory of their facilities. A new mass-transfer model has been developed to predict the VOC emission rates from batch and continuous aeration tanks with mechanical surface aerators. The model takes into consideration that the VOC mass transfer occurs in two separate mass-transfer zones instead of lumping the overall VOC transfer in the whole aeration tank as is done in the conventional ASCE-based model. The predictive capabilities of the two-zone and the ASCE-based models were examined by calculating the emission rates of 10 priority pollutants from aeration tanks. The effects of the hydraulic retention time, the Henry`s law constant, gas-phase resistance, and the water and air environmental conditions on the VOC emission rates were predicted by the two models.

  15. Field emission properties and growth mechanism of In2O3 nanostructures

    PubMed Central

    2014-01-01

    Four kinds of nanostructures, nanoneedles, nanohooks, nanorods, and nanotowers of In2O3, have been grown by the vapor transport process with Au catalysts or without any catalysts. The morphology and structure of the prepared nanostructures are determined on the basis of field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The growth direction of the In2O3 nanoneedles is along the [001], and those of the other three nanostructures are along the [100]. The growth mechanism of the nanoneedles is the vapor-liquid–solid (VLS), and those of the other three nanostructures are the vapor-solid (VS) processes. The field emission properties of four kinds of In2O3 nanostructures have been investigated. Among them, the nanoneedles have the best field emission properties with the lowest turn-on field of 4.9 V/μm and the threshold field of 12 V/μm due to possessing the smallest emitter tip radius and the weakest screening effect. PMID:24612921

  16. Field emission properties and growth mechanism of In2O3 nanostructures

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Zheng, Zhaoqiang; Wu, Huanyu; Zhu, Lianfeng

    2014-03-01

    Four kinds of nanostructures, nanoneedles, nanohooks, nanorods, and nanotowers of In2O3, have been grown by the vapor transport process with Au catalysts or without any catalysts. The morphology and structure of the prepared nanostructures are determined on the basis of field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The growth direction of the In2O3 nanoneedles is along the [001], and those of the other three nanostructures are along the [100]. The growth mechanism of the nanoneedles is the vapor-liquid-solid (VLS), and those of the other three nanostructures are the vapor-solid (VS) processes. The field emission properties of four kinds of In2O3 nanostructures have been investigated. Among them, the nanoneedles have the best field emission properties with the lowest turn-on field of 4.9 V/μm and the threshold field of 12 V/μm due to possessing the smallest emitter tip radius and the weakest screening effect.

  17. High-Energy Proximal Femur Fractures in Geriatric Patients

    PubMed Central

    Hahnhaussen, Jens; Hak, David J; Weckbach, Sebastian; Ertel, Wolfgang; Stahel, Philip F

    2011-01-01

    Background: There is limited information in the literature on the outcomes and complications in elderly patients who sustain high-energy hip fractures. As the population ages, the incidence of high-energy geriatric hip fractures is expected to increase. The purpose of this study was to analyze the outcomes and complications in patients aged 65 years or older, who sustained a high-energy proximal femur fracture. Methods: Retrospective review of a prospective trauma database from January 2000 to April 2011 at a single US academic level-1 trauma center. Inclusion criteria consisted of all patients of age 65 years or older, who sustained a proximal femur fracture related to a high-energy trauma mechanism. Details concerning injury, acute treatment, and clinical course and outcome were obtained from medical records and radiographs. Results: We identified 509 proximal femur fractures in patients older than 65 years of age, of which 32 (6.3%) were related to a high-energy trauma mechanism. The mean age in the study group was 72.2 years (range 65-87), with a mean injury severity score of 20 points (range 9-57). Three patients died before discharge (9.4%), and 22 of 32 patients sustained at least one complication (68.8%). Blunt chest trauma represented the most frequently associated injury, and the main root cause of pulmonary complications. The patients' age and comorbidities did not significantly correlate with the rate of complications and the 1-year mortality. Conclusions: High-energy proximal femur fractures in elderly patients are not very common and are associated with a low in-hospital mortality rate of less than 10%, despite high rate of complications of nearly 70%. This selective cohort of patients requires a particular attention to respiratory management due to the high incidence of associated chest trauma. PMID:23569690

  18. Experimental tests of the generation mechanism of auroral medium frequency burst radio emissions

    NASA Astrophysics Data System (ADS)

    Bunch, N. L.; Labelle, J.; Weatherwax, A. T.; Hughes, J. M.; Lummerzheim, D.

    2009-09-01

    Medium frequency (MF) burst is an impulsive auroral radio emission at 1.3-4.5 MHz commonly detected by ground-based instruments for a few minutes at substorm onsets. It is thought to arise from mode conversion radiation. The Dartmouth College MF radio interferometer at Toolik Field Station, Alaska (68.51° invariant latitude), measured spectra, amplitudes, and directions of arrival (DOA) of 47 MF burst events during 2006-2007 and 49 events during 2007-2008. Statistical analysis of these events shows that they come predominantly from the south and east of Toolik, as expected because propagation conditions are more favorable poleward and westward of the active auroral arcs than equatorward or eastward during premidnight (westward moving) substorm onset activity. Case studies of a selected MF burst event on 20 November 2007 show that motions of the radio emissions qualitatively track the motions of auroral arcs simultaneously observed with all-sky camera. Case studies of DOA data of selected MF burst events on 31 January and 20 November 2007 show that higher-frequency components of MF burst arrive at higher elevation angles than lower-frequency components. Statistical studies confirm this trend. Ray-tracing analysis shows that this trend implies that sources of the higher-frequency components of the MF burst are at higher altitudes than those of the lower-frequency components. The analysis also shows that the MF burst comes from the bottomside F region ionosphere. These observations are consistent with a mechanism of MF burst emission whereby the emissions originate from mode conversion of Langmuir or upper hybrid waves excited over a range of altitudes in the bottomside F region.

  19. Chloroform formation in Arctic and Subarctic soils - mechanism and emissions to the atmosphere

    NASA Astrophysics Data System (ADS)

    Albers, Christian N.; Johnsen, Anders R.; Jacobsen, Ole S.

    2015-04-01

    It is well established that halogenated organic compounds are formed naturally in the terrestrial environment. These compounds include volatiles such as trihalomethanes that may escape to the atmosphere. In deed most of the atmospheric chloroform (and other trihalomethane species) is regarded to have a natural origin. This origin may be both marine and terrestrial. Chloroform formation in soil has been reported in a number of studies, mostly conducted in temperate and (sub-) tropical environments. We hereby report that also colder soils emit chloroform naturally. We measured in situ the fluxes of chloroform from soil to atmosphere in 6 Subarctic and 5 Arctic areas covering different dwarf heath, wetland and forest biotopes in Greenland and Northern Sweden. Emissions were largest from the forested areas, but all areas emitted measurable amounts of chloroform. Also the brominated analog bromodichloromethane was formed in Arctic and Subarctic soils but the fluxes to the atmosphere were much lower than the corresponding chloroform emissions. No other volatile poly-halogenated organic compounds were found to be emitted from the study areas. It has previously been proposed that chloroform is formed in temperate forest soils through trichloroacetyl intermediates formed by unspecific enzymatic chlorination of soil organic matter. We found positive relationships between chloroform emissions and the concentration of trichloroacetyl groups in soil within the various biotopes. The hydrolysis of trichloroacetyl compounds is, however, very pH dependent, excluding a simple relationship between trichloroacetyl concentration and chloroform emission in any given soil. However, our results show that at low pH, turnover time of soil trichloroacetyl compounds may be counted in decades while at pH above 6, turnover time may be just a few months. We found no relationship between trichloroacetyl concentration and total organic chlorine concentration in the soils indicating that more than

  20. Duration of emission of volatile organic compounds from mechanically damaged plant leaves.

    PubMed

    Smith, Lincoln; Beck, John J

    2015-09-01

    Classical biological control of invasive alien weeds depends on the use of arthropod herbivores that are sufficiently host specific to avoid risk of injuring nontarget plants. Host plant specificity is usually evaluated by using a combination of behavioral and developmental experiments under choice, no-choice and field conditions. Secondary plant compounds are likely to have an important influence on host plant specificity. However, relatively little is known about the volatile organic compounds (VOCs) that are emitted by target and nontarget plants, and how environmental conditions may affect their emission. Previous studies have shown that mechanical damage of leaves increases the composition and content of VOCs emitted. In this study we measured the VOC emissions of five species of plants in the subtribe Centaureinae (Asteraceae)--Carthamus tinctorius, Centaurea cineraria, Centaurea melitensis, Centaurea rothrockii, and Centaurea solstitialis--that have previously been used in host specificity experiments for a prospective biological control agent of yellow starthistle (C. solstitialis). Leaves of each plant were punctured with a needle and the VOCs were collected by solid-phase microextraction (SPME) periodically over 48 h and analyzed by GC-MS. A total of 49 compounds were detected. Damage caused an immediate increase of 200-600% in the composition of VOCs emitted from each plant species, and the amounts generally remained high for at least 48 h. The results indicate that a very unspecific mechanical damage can cause a prolonged change in the VOC profile of plants. PMID:26398629

  1. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Y.T.; Payne, S.A.; Hayden, J.S.; Campbell, J.H.; Aston, M.K.; Elder, M.L.

    1996-06-11

    In a high energy laser system utilizing phosphate laser glass components to amplify the laser beam, the laser system requires a generated laser beam having an emission bandwidth of less than 26 nm and the laser glass components consist essentially of (on an oxide composition basis) in mole percent: P{sub 2}O{sub 5}, 50--75; Al{sub 2}O{sub 3}, {gt}0--10; K{sub 2}O, {gt}0--30; MgO, 0--30; CaO, 0--30; Li{sub 2}O, 0--20; Na{sub 2}O, 0--20; Rb{sub 2}O, 0--20; Cs{sub 2}O, 0--20; BeO, 0--20; SrO, 0--20; BaO, 0--20; ZnO, 0--20; PbO, 0--20; B{sub 2}O{sub 3}, 0--10; Y{sub 2}O{sub 3}, 0--10; La{sub 2}O{sub 3}, 0--8; Ln{sub 2}O{sub 3}, 0.01--8; wherein the sum of MgO and CaO is >0--30; the sum of Li{sub 2}O, Na{sub 2}O, Rb{sub 2}O, and Cs{sub 2}O is 0--20; the sum of BeO, SrO, BaO, ZnO, and PbO is 0--20; the sum of B{sub 2}O{sub 3} and Y{sub 2}O{sub 3} is 0--10; and Ln{sub 2}O{sub 3} represents the sum of the oxides of active lasing lanthanides of atomic number 58--71. 21 figs.

  2. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Yuiko T.; Payne, Stephen A.; Hayden, Joseph S.; Campbell, John H.; Aston, Mary Kay; Elder, Melanie L.

    1996-01-01

    In a high energy laser system utilizing phosphate laser glass components to amplify the laser beam, the laser system requires a generated laser beam having an emission bandwidth of less than 26 nm and the laser glass components consist essentially of (on an oxide composition basis) in mole percent: P{sub 2}O{sub 5}, 50--75; Al{sub 2}O{sub 3}, {gt}0--10; K{sub 2}O, {gt}0--30; MgO, 0--30; CaO, 0--30; Li{sub 2}O, 0--20; Na{sub 2}O, 0--20; Rb{sub 2}O, 0--20; Cs{sub 2}O, 0--20; BeO, 0--20; SrO, 0--20; BaO, 0--20; ZnO, 0--20; PbO, 0--20; B{sub 2}O{sub 3}, 0--10; Y{sub 2}O{sub 3}, 0--10; La{sub 2}O{sub 3}, 0--8; Ln{sub 2}O{sub 3}, 0.01--8; wherein the sum of MgO and CaO is >0--30; the sum of Li{sub 2}O, Na{sub 2}O, Rb{sub 2}O, and Cs{sub 2}O is 0--20; the sum of BeO, SrO, BaO, ZnO, and PbO is 0--20; the sum of B{sub 2}O{sub 3} and Y{sub 2}O{sub 3} is 0--10; and Ln{sub 2}O{sub 3} represents the sum of the oxides of active lasing lanthanides of atomic number 58--71. 21 figs.

  3. Sharpening of field emitter tips using high-energy ions

    DOEpatents

    Musket, Ronald G.

    1999-11-30

    A process for sharpening arrays of field emitter tips of field emission cathodes, such as found in field-emission, flat-panel video displays. The process uses sputtering by high-energy (more than 30 keV) ions incident along or near the longitudinal axis of the field emitter to sharpen the emitter with a taper from the tip or top of the emitter down to the shank of the emitter. The process is particularly applicable to sharpening tips of emitters having cylindrical or similar (e.g., pyramidal) symmetry. The process will sharpen tips down to radii of less than 12 nm with an included angle of about 20 degrees. Because the ions are incident along or near the longitudinal axis of each emitter, the tips of gated arrays can be sharpened by high-energy ion beams rastered over the arrays using standard ion implantation equipment. While the process is particularly applicable for sharpening of arrays of field emitters in field-emission flat-panel displays, it can be effectively utilized in the fabrication of other vacuum microelectronic devices that rely on field emission of electrons.

  4. High-Energy-Density Capacitors

    NASA Technical Reports Server (NTRS)

    Slenes, Kirk

    2003-01-01

    Capacitors capable of storing energy at high densities are being developed for use in pulse-power circuits in such diverse systems as defibrillators, particle- beam accelerators, microwave sources, and weapons. Like typical previously developed energy-storage capacitors, these capacitors are made from pairs of metal/solid-dielectric laminated sheets that are wound and pressed into compact shapes to fit into cans, which are then filled with dielectric fluids. Indeed, these capacitors can be fabricated largely by conventional fabrication techniques. The main features that distinguish these capacitors from previously developed ones are improvements in (1) the selection of laminate materials, (2) the fabrication of the laminated sheets from these materials, and (3) the selection of dielectric fluids. In simplest terms, a high-performance laminated sheet of the type used in these capacitors is made by casting a dielectric polymer onto a sheet of aluminized kraft paper. The dielectric polymer is a siloxane polymer that has been modified with polar pendant groups to increase its permittivity and dielectric strength. Potentially, this polymer is capable of withstanding an energy density of 7.5 J/cm3, which is four times that of the previous state-of-the-art-capacitor dielectric film material. However, the full potential of this polymer cannot be realized at present because (1) at thicknesses needed for optimum performance (.8.0 m), the mechanical strength of a film of this polymer is insufficient for incorporation into a wound capacitor and (2) at greater thickness, the achievable energy density decreases because of a logarithmic decrease in dielectric strength with increasing thickness. The aluminized kraft paper provides the mechanical strength needed for processing of the laminate and fabrication of the capacitor, and the aluminum film serves as an electrode layer. Because part of the thickness of the dielectric is not occupied by the modified siloxane polymer, the

  5. Concerning mechanisms for the zebra pattern formation in the solar radio emission

    SciTech Connect

    Laptukhov, A. I.; Chernov, G. P.

    2009-02-15

    The nature of the zebra patterns in continuous type-IV solar radio bursts is discussed. The most comprehensively developed models of such patterns involve mechanisms based on the double plasma resonance and plasma wave-whistler interaction. Over the last five years, there have appeared a dozen papers concerning the refinement of the mechanism based on the double plasma resonance, because, in its initial formulation, this mechanism failed to describe many features of the zebra pattern. It is shown that the improved model of this mechanism with a power-law distribution function of hot electrons within the loss cone is inapplicable to the coronal plasma. In recent papers, the formation of the zebra pattern in the course of electromagnetic wave propagation through the solar corona was considered. In the present paper, all these models are estimated comparatively. An analysis of recent theories shows that any types of zebra patterns can form in the course of radio wave propagation in the corona, provided that there are plasma inhomogeneities of different scales on the wave path. The superfine structure of zebra stripes in the form of millisecond spikes with a strict period of {approx}30 ms can be attributed to the generation of continuous radio emission in the radio source itself, assuming that plasma inhomogeneities are formed by a finite-amplitude wave with the same period.

  6. High-energy astroparticle physics with CALET

    NASA Astrophysics Data System (ADS)

    Maestro, Paolo

    2013-02-01

    The CALorimetric Electron Telescope (CALET) will be installed on the Exposure Facility of the Japanese Experiment Module (JEM-EF) on the International Space Station (ISS) in 2014 where it will measure the cosmic-ray fluxes for five years. Its main scientific goals are to search for dark matter, investigate the mechanism of cosmic-ray acceleration and propagation in the Galaxy and discover possible astrophysical sources of high-energy electrons nearby the Earth. The instrument, under construction, consists of two layers of segmented plastic scintillators for the cosmic-ray charge identification (CHD), a 3 X0-thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 X0-thick lead-tungstate calorimeter (TASC). The CHD can provide single-element separation in the interval of atomic number Z from 1 to 40, while IMC and TASC can measure the energy of cosmic-ray particles with excellent resolution in the range from few GeV up to several hundreds of TeV. Moreover, IMC and TASC provide the longitudinal and lateral development of the shower, a key issue for good electron/hadron discrimination. In this paper, we will review the status of the mission, the instrument configuration and its expected performance, and the CALET capability to measure the different components of the cosmic radiation.

  7. Spin structure in high energy processes: Proceedings

    SciTech Connect

    DePorcel, L.; Dunwoodie, C.

    1994-12-01

    This report contains papers as the following topics: Spin, Mass, and Symmetry; physics with polarized Z{sup 0}s; spin and precision electroweak physics; polarized electron sources; polarization phenomena in quantum chromodynamics; polarized lepton-nucleon scattering; polarized targets in high energy physics; spin dynamics in storage rings and linear accelerators; spin formalism and applications to new physics searches; precision electroweak physics at LEP; recent results on heavy flavor physics from LEP experiments using 1990--1992 data; precise measurement of the left-right cross section asymmetry in Z boson production by electron-positron collisions; preliminary results on heavy flavor physics at SLD; QCD tests with SLD and polarized beams; recent results from TRISTAN at KEK; recent B physics results from CLEO; searching for the H dibaryon at Brookhaven; recent results from the compton observatory; the spin structure of the deuteron; spin structure of the neutron ({sup 3}HE) and the Bjoerken sum rule; a consumer`s guide to lattice QCD results; top ten models constrained by b {yields} sy; a review of the Fermilab fixed target program; results from the D0 experiment; results from CDF at FNAL; quantum-mechanical suppression of bremsstrahlung; report from the ZEUS collaboration at HERA; physics from the first year of H1 at HERA, and hard diffraction. These papers have been cataloged separately elsewhere.

  8. A mechanism for biologically-induced iodine emissions from sea-ice

    NASA Astrophysics Data System (ADS)

    Saiz-Lopez, A.; Blaszczak-Boxe, C. S.; Carpenter, L. J.

    2015-04-01

    Ground- and satellite-based measurements have reported high concentrations of iodine monoxide (IO) in coastal Antarctica. The sources of such a large iodine burden in the coastal Antarctic atmosphere remain unknown. We propose a mechanism for iodine release from sea-ice based on the premise that micro-algae are the primary source of iodine emissions in this environment. The emissions are triggered by the biological production of iodide (I-) and hypoiodous acid (HOI) from micro-algae (contained within and underneath sea-ice) and their diffusion through sea-ice brine channels, to accumulate in the quasi-liquid layer (QLL) on the surface of sea-ice. Prior to reaching the QLL, the diffusion timescale of iodine within sea-ice is depth-dependent. The QLL is also a vital component of the proposed mechanism as it enhances the chemical kinetics of iodine-related reactions, which allows for the efficient release of iodine to the polar boundary layer. We suggest iodine is released to the atmosphere via 3 possible pathways: (1) emitted from the QLL and then transported throughout snow atop sea-ice, to be released to the atmosphere, (2) released directly from the QLL to the atmosphere in regions of sea-ice that are not covered with snowpack; or (3) emitted to the atmosphere directly through fractures in the sea-ice pack. To investigate the proposed biology-ice-atmosphere coupling at coastal Antarctica we use a multiphase model that incorporates the transport of iodine species, via diffusion, at variable depths, within brine channels of sea-ice. Model simulations were conducted to interpret observations of elevated springtime IO in the coastal Antarctic, around the Weddell Sea. The results show that the levels of inorganic iodine (i.e., I2, IBr, ICl) released from sea-ice through this mechanism could account for the observed IO concentrations during this timeframe. The model results also indicate that iodine may trigger the catalytic release of bromine from sea-ice through phase

  9. The Effect of a Mechanical Arm System on Portable Grinder Vibration Emissions

    PubMed Central

    McDowell, Thomas W.; Welcome, Daniel E.; Warren, Christopher; Xu, Xueyan S.; Dong, Ren G.

    2016-01-01

    Mechanical arm systems are commonly used to support powered hand tools to alleviate ergonomic stressors related to the development of workplace musculoskeletal disorders. However, the use of these systems can increase exposure times to other potentially harmful agents such as hand-transmitted vibration. To examine how these tool support systems affect tool vibration, the primary objectives of this study were to characterize the vibration emissions of typical portable pneumatic grinders used for surface grinding with and without a mechanical arm support system at a workplace and to estimate the potential risk of the increased vibration exposure time afforded by the use of these mechanical arm systems. This study also developed a laboratory-based simulated grinding task based on the ISO 28927-1 (2009) standard for assessing grinder vibrations; the simulated grinding vibrations were compared with those measured during actual workplace grinder operations. The results of this study demonstrate that use of the mechanical arm may provide a health benefit by reducing the forces required to lift and maneuver the tools and by decreasing hand-transmitted vibration exposure. However, the arm does not substantially change the basic characteristics of grinder vibration spectra. The mechanical arm reduced the average frequency-weighted acceleration by about 24% in the workplace and by about 7% in the laboratory. Because use of the mechanical arm system can increase daily time-on-task by 50% or more, the use of such systems may actually increase daily time-weighted hand-transmitted vibration exposures in some cases. The laboratory acceleration measurements were substantially lower than the workplace measurements, and the laboratory tool rankings based on acceleration were considerably different than those from the workplace. Thus, it is doubtful that ISO 28927-1 is useful for estimating workplace grinder vibration exposures or for predicting workplace grinder acceleration rank

  10. The Effect of a Mechanical Arm System on Portable Grinder Vibration Emissions.

    PubMed

    McDowell, Thomas W; Welcome, Daniel E; Warren, Christopher; Xu, Xueyan S; Dong, Ren G

    2016-04-01

    Mechanical arm systems are commonly used to support powered hand tools to alleviate ergonomic stressors related to the development of workplace musculoskeletal disorders. However, the use of these systems can increase exposure times to other potentially harmful agents such as hand-transmitted vibration. To examine how these tool support systems affect tool vibration, the primary objectives of this study were to characterize the vibration emissions of typical portable pneumatic grinders used for surface grinding with and without a mechanical arm support system at a workplace and to estimate the potential risk of the increased vibration exposure time afforded by the use of these mechanical arm systems. This study also developed a laboratory-based simulated grinding task based on the ISO 28927-1 (2009) standard for assessing grinder vibrations; the simulated grinding vibrations were compared with those measured during actual workplace grinder operations. The results of this study demonstrate that use of the mechanical arm may provide a health benefit by reducing the forces required to lift and maneuver the tools and by decreasing hand-transmitted vibration exposure. However, the arm does not substantially change the basic characteristics of grinder vibration spectra. The mechanical arm reduced the average frequency-weighted acceleration by about 24% in the workplace and by about 7% in the laboratory. Because use of the mechanical arm system can increase daily time-on-task by 50% or more, the use of such systems may actually increase daily time-weighted hand-transmitted vibration exposures in some cases. The laboratory acceleration measurements were substantially lower than the workplace measurements, and the laboratory tool rankings based on acceleration were considerably different than those from the workplace. Thus, it is doubtful that ISO 28927-1 is useful for estimating workplace grinder vibration exposures or for predicting workplace grinder acceleration rank

  11. Mechanical tuning of the moth ear: distortion-product otoacoustic emissions and tympanal vibrations.

    PubMed

    Mora, Emanuel C; Cobo-Cuan, Ariadna; Macías-Escrivá, Frank; Pérez, Martha; Nowotny, Manuela; Kössl, Manfred

    2013-10-15

    The mechanical tuning of the ear in the moth Empyreuma pugione was investigated by distortion-product otoacoustic emissions (DPOAE) and laser Doppler vibrometry (LDV). DPOAE audiograms were assessed using a novel protocol that may be advantageous for non-invasive auditory studies in insects. To evoke DPOAE, two-tone stimuli within frequency and level ranges that generated a large matrix of values (960 frequency-level combinations) were used to examine the acoustic space in which the moth tympanum shows its best mechanical and acoustical responses. The DPOAE tuning curve derived from the response matrix resembles that obtained previously by electrophysiology, and is V-shaped and tuned to frequencies between 25 and 45 kHz with low Q10dB values of 1.21±0.26. In addition, while using a comparable stimulation regime, mechanical distortion in the displacement of the moth's tympanal membrane at the stigma was recorded with a laser Doppler vibrometer. The corresponding mechanical vibration audiograms were compared with DPOAE audiograms. Both types of audiograms have comparable shape, but most of the mechanical response fields are shifted towards lower frequencies. We showed for the first time in moths that DPOAE have a pronounced analogy in the vibration of the tympanic membrane where they may originate. Our work supports previous studies that point to the stigma (and the internally associated transduction machinery) as an important place of sound amplification in the moth ear, but also suggests a complex mechanical role for the rest of the transparent zone. PMID:23868848

  12. On the Origin of Ultra High Energy Cosmic Rays II

    SciTech Connect

    Fowler, T K; Colgate, S; Li, H; Bulmer, R H; Pino, J

    2011-03-08

    We show that accretion disks around Active Galactic Nuclei (AGNs) could account for the enormous power in observed ultra high energy cosmic rays {approx}10{sup 20} eV (UHEs). In our model, cosmic rays are produced by quasi-steady acceleration of ions in magnetic structures previously proposed to explain jets around Active Galactic Nuclei with supermassive black holes. Steady acceleration requires that an AGN accretion disk act as a dynamo, which we show to follow from a modified Standard Model in which the magnetic torque of the dynamo replaces viscosity as the dominant mechanism accounting for angular momentum conservation during accretion. A black hole of mass M{sub BH} produces a steady dynamo voltage V {proportional_to} {radical}M{sub BH} giving V {approx} 10{sup 20} volts for M{sub BH} {approx} 10{sup 8} solar masses. The voltage V reappears as an inductive electric field at the advancing nose of a dynamo-driven jet, where plasma instability inherent in collisionless runaway acceleration allows ions to be steadily accelerated to energies {approx} V, finally ejected as cosmic rays. Transient events can produce much higher energies. The predicted disk radiation is similar to the Standard Model. Unique predictions concern the remarkable collimation of jets and emissions from the jet/radiolobe structure. Given MBH and the accretion rate, the model makes 7 predictions roughly consistent with data: (1) the jet length; (2) the jet radius; (3) the steady-state cosmic ray energy spectrum; (4) the maximum energy in this spectrum; (5) the UHE cosmic ray intensity on Earth; (6) electron synchrotron wavelengths; and (7) the power in synchrotron radiation. These qualitative successes motivate new computer simulations, experiments and data analysis to provide a quantitative verification of the model.

  13. High energy electron processing of icy regoliths on Saturn's moons

    NASA Astrophysics Data System (ADS)

    Schaible, Micah; Johnson, Robert E.

    2015-11-01

    A unique space weathering phenomenon has been identified on several icy Saturnian moons. Cassini revealed anomalous lens shaped regions in both optical and thermal wavelengths, colloquially known as the 'PacMan' feature, which are centered on the leading hemispheres and approximately symmetric about the equators. In particular, the Cassini InfraRed Spectrometer (CIRS) measurements of thermal emission in the mid-IR showed that surface temperature variations during a diurnal cycle were smaller inside the anomalous regions. The locations of the anomalies were shown to closely match the expected deposition profile of high energy (~ MeV) electrons moving counter rotational to the moons, suggesting an energetic source to drive their formation. However, the mechanisms by which thermal conductivity enhancement occur lack quantitative comparison with theoretical and experimental results.Electron interactions with the grains can excite molecules, which, if near enough to an intergrain contact, can cause atoms or molecules to migrate into the contact region, thus increasing the contact volume or 'sintering' the grains. Sintering improves the thermal contact between grains, leading to increased effective thermal conductivity of the regolith. Equations previously developed to describe material behavior in nuclear reactor were used to estimate the timescale for the energetic electrons to increase the contact volume sufficiently to describe the enhanced thermal conductivity of the anomalous regions. In order to properly constrain the sintering calculations, the unique electron energy distribution measured in the vicinity of each of the moons was used in the calculations, and molecular dynamics simulations of excited electrons in water ice were carried out to determine the length scale for an average electron excitation or ionization event. This length scale determines the distance from the primary reaction at which electrons can still be mobilized to move into the contact region

  14. High energy mode locked fiber oscillators for high contrast, high energy petawatt laser seed sources

    SciTech Connect

    Dawson, J W; Messerly, M J; An, J; Kim, D; Barty, C J

    2006-06-15

    In a high-energy petawatt laser beam line the ASE pulse contrast is directly related to the total laser gain. Thus a more energetic input pulse will result in increased pulse contrast at the target. We have developed a mode-locked fiber laser with high quality pulses and energies exceeding 25nJ. We believe this 25nJ result is scalable to higher energies. This oscillator has no intra-cavity dispersion compensation, which yields an extremely simple, and elegant laser configuration. We will discuss the design of this laser, our most recent results and characterization of all the key parameters relevant to it use as a seed laser. Our oscillator is a ring cavity mode-locked fiber laser [1]. These lasers operate in a self-similar pulse propagation regime characterized by a spectrum that is almost square. This mode was found theoretically [2] to occur only in the positive dispersion regime. Further increasing positive dispersion should lead to increasing pulse energy [2]. We established that the positive dispersion required for high-energy operation was approximately that of 2m of fiber. To this end, we constructed a laser cavity similar to [1], but with no gratings and only 2m of fiber, which we cladding pumped in order to ensure sufficient pump power was available to achieve mode-locked operation. A schematic of the laser is shown in figure 1 below. This laser produced low noise 25nJ pulses with a broad self similar spectrum (figure 2) and pulses that could be de-chirped to <100fs (figure 3). Pulse contrast is important in peta-watt laser systems. A major contributor to pulse contrast is amplified spontaneous emission (ASE), which is proportional to the gain in the laser chain. As the oscillator strength is increased, the required gain to reach 1PW pulses is decreased, reducing ASE and improving pulse contrast. We believe these lasers can be scaled in a stable fashion to pulse energies as high as 100nJ and have in fact seen 60nJ briefly in our lab, which is work still

  15. Pulsar Radiation Models - Radio to High Energies

    NASA Astrophysics Data System (ADS)

    Venter, Christo; Harding, Alice

    Rotation-powered pulsars emit over nearly 19 decades of energy. Although an all-encompassing answer as to the origin of this broad-band emission remains elusive nearly 50 years after their discovery, the theorist does have a few tools in his / her toolkit to aid investigation. Phase-averaged spectra give clues as to the emitting particles, their acceleration, environment, and the radiation mechanism. Moreover, the phase-evolution of spectra constrains the radiation energetics and environment as different parts of the magnetosphere are exposed to the observer during the pulsar's rotation. A detailed model furthermore critically depends on the specification of the emission geometry. Modeling the light curves probes this fundamental geometric assumption, which is closely tied to the posited magnetospheric structure. Studying many versions of the same system helps to constrain critical population-averaged quantities, discover population trends, and probe model performance for different regions of phase space. When coupled with population synthesis, such modeling can provide powerful discrimination between competing emission models. Polarization properties may provide complementary constraints on the magnetic field orientation and pulsar geometry. Lastly, comparison of parameters inferred from independent models for the different wavebands yields necessary crosschecks. It is indeed fortunate that the past few years have witnessed an incredible increase in number and improved characterization of rotation-powered pulsars. We will review how the enhanced quality and quantity of data are providing impetus for further model refinement.

  16. From QCD-based hard-scattering to nonextensive statistical mechanical descriptions of transverse momentum spectra in high-energy pp and pp¯ collisions

    SciTech Connect

    Wong, Cheuk-Yin; Wilk, Grzegorz; Cirto, Leonardo J. L.; Tsallis, Constantino

    2015-06-22

    Transverse spectra of both jets and hadrons obtained in high-energy $pp$ and $p\\bar p $ collisions at central rapidity exhibit power-law behavior of $1/p_T^n$ at high $p_T$. The power index $n$ is 4-5 for jet production and is slightly greater for hadron production. Furthermore, the hadron spectra spanning over 14 orders of magnitude down to the lowest $p_T$ region in $pp$ collisions at LHC can be adequately described by a single nonextensive statistical mechanical distribution that is widely used in other branches of science. This suggests indirectly the dominance of the hard-scattering process over essentially the whole $p_T$ region at central rapidity in $pp$ collisions at LHC. We show here direct evidences of such a dominance of the hard-scattering process by investigating the power index of UA1 jet spectra over an extended $p_T$ region and the two-particle correlation data of the STAR and PHENIX Collaborations in high-energy $pp$ and $p \\bar p$ collisions at central rapidity. We then study how the showering of the hard-scattering product partons alters the power index of the hadron spectra and leads to a hadron distribution that can be cast into a single-particle non-extensive statistical mechanical distribution. Lastly, because of such a connection, the non-extensive statistical mechanical distribution can be considered as a lowest-order approximation of the hard-scattering of partons followed by the subsequent process of parton showering that turns the jets into hadrons, in high energy $pp$ and $p\\bar p$ collisions.

  17. Practical neutron dosimetry at high energies

    SciTech Connect

    McCaslin, J.B.; Thomas, R.H.

    1980-10-01

    Dosimetry at high energy particle accelerators is discussed with emphasis on physical measurements which define the radiation environment and provide an immutable basis for the derivation of any quantities subsequently required for risk evaluation. Results of inter-laboratory dosimetric comparisons are reviewed and it is concluded that a well-supported systematic program is needed which would make possible detailed evaluations and inter-comparisons of instruments and techniques in well characterized high energy radiation fields. High-energy dosimetry is so coupled with radiation transport that it is clear their study should proceed concurrently.

  18. High energy hadrons in extensive air showers

    NASA Technical Reports Server (NTRS)

    Tonwar, S. C.

    1985-01-01

    Experimental data on the high energy hadronic component in extensive air showers of energies approx. 10 to the 14 to 10 to the 16 eV when compared with expectations from Monte Carlo simulations have shown the observed showers to be deficient in high energy hadrons relative to simulated showers. An attempt is made to understand these anomalous features with more accurate comparison of observations with expectations, taking into account the details of the experimental system. Results obtained from this analysis and their implications for the high energy physics of particle interactions at energy approx. 10 to the 15 eV are presented.

  19. New accelerators in high-energy physics

    SciTech Connect

    Blewett, J.P.

    1982-01-01

    First, I should like to mention a few new ideas that have appeared during the last few years in the accelerator field. A couple are of importance in the design of injectors, usually linear accelerators, for high-energy machines. Then I shall review some of the somewhat sensational accelerator projects, now in operation, under construction or just being proposed. Finally, I propose to mention a few applications of high-energy accelerators in fields other than high-energy physics. I realize that this is a digression from my title but I hope that you will find it interesting.

  20. High energy physics in the United States

    SciTech Connect

    Month, M.

    1985-10-16

    The US program in high energy physics from 1985 to 1995 is reviewed. The program depends primarily upon work at the national accelerator centers, but includes a modest but diversified nonaccelerator program. Involvement of universities is described. International cooperation in high energy physics is discussed, including the European, Japanese, USSR, and the People's Republic of China's programs. Finally, new facilities needed by the US high energy physics program are discussed, with particular emphasis given to a Superconducting Super Collider for achieving ever higher energies in the 20 TeV range. (LEW)

  1. High Energy Electron Detection with ATIC

    NASA Technical Reports Server (NTRS)

    Chang, J.; Schmidt, W. K. H.; Adams, James H., Jr.; Ahn, H.; Ampe, J.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    The ATIC (Advanced Thin Ionization Calorimeter) balloon-borne ionization calorimeter is well suited to record and identify high energy cosmic ray electrons. The instrument was exposed to high-energy beams at CERN H2 bean-dine in September of 1999. We have simulated the performance of the instrument, and compare the simulations with actual high energy electron exposures at the CERN accelerator. Simulations and measurements do not compare exactly, in detail, but overall the simulations have predicted actual measured behavior quite well.

  2. Computing in high-energy physics

    DOE PAGESBeta

    Mount, Richard P.

    2016-05-31

    I present a very personalized journey through more than three decades of computing for experimental high-energy physics, pointing out the enduring lessons that I learned. This is followed by a vision of how the computing environment will evolve in the coming ten years and the technical challenges that this will bring. I then address the scale and cost of high-energy physics software and examine the many current and future challenges, particularly those of management, funding and software-lifecycle management. Lastly, I describe recent developments aimed at improving the overall coherence of high-energy physics software.

  3. Perspectives on High-Energy-Density Physics

    NASA Astrophysics Data System (ADS)

    Drake, R. Paul

    2008-11-01

    Much of 21st century plasma physics will involve work to produce, understand, control, and exploit very non-traditional plasmas. High-energy density (HED) plasmas are often examples, variously involving strong Coulomb interactions and few particles per Debeye sphere, dominant radiation effects, strongly relativistic effects, or strongly quantum-mechanical behavior. Indeed, these and other modern plasma systems often fall outside the early standard theoretical definitions of ``plasma''. This presentation will focus on two types of HED plasmas that exhibit non-traditional behavior. Our first example will be the plasmas produced by extremely strong shock waves. Shock waves are present across the entire realm of plasma densities, often in space or astrophysical contexts. HED shock waves (at pressures > 1 Mbar) enable studies in many areas, from equations of state to hydrodynamics to radiation hydrodynamics. We will specifically consider strongly radiative shocks, in which the radiative energy fluxes are comparable to the mechanical energy fluxes that drive the shocks. Modern HED facilities can produce such shocks, which are also present in dense, energetic, astrophysical systems such as supernovae. These shocks are also excellent targets for advanced simulations due to their range of spatial scales and complex radiation transport. Our second example will be relativistic plasmas. In general, these vary from plasmas containing relativistic particle beams, produced for some decades in the laboratory, to the relativistic thermal plasmas present for example in pulsar winds. Laboratory HED relativistic plasmas to date have been those produced by laser beams of irradiance ˜ 10^18 to 10^22 W/cm^2 or by accelerator-produced HED electron beams. These have applications ranging from generation of intense x-rays to production of proton beams for radiation therapy to acceleration of electrons. Here we will focus on electron acceleration, a spectacular recent success and a rare

  4. High-Energy Observation of GRB 090217 with Fermi

    SciTech Connect

    Cutini, S.; Piron, F.

    2010-03-26

    The Fermi observatory is advancing our knowledge of Gamma-Ray Bursts (GRBs) through pioneering observations at high energies, covering more then 7 decades of energy with the two on-board detectors, the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). Here we report on the observation of long GRB 090217 which triggered the GBM and as been independently detected by the on-ground blind search LAT algorithm. We present the GBM and LAT observations, including a temporal profile and time-resolved spectral analysis from 8 keV up to approx1 GeV. The time-averaged and time-resolved spectra are well reproduced by a Band model, with no substantial spectral evolution. We compare these observations to the other LAT detections of long bursts, and discuss some theoretical implications on GRB high-energy emission.

  5. Exploring the High Energy Universe: GLAST Mission and Science

    NASA Technical Reports Server (NTRS)

    McEnery, Julie

    2007-01-01

    GLAST, the Gamma-Ray Large Area Space Telescope, is NASA's next-generation high-energy gamma-ray satellite scheduled for launch in Autumn 2007. GLAST will allow measurements of cosmic gamma-ray sources in t he 10 MeV to 100 GeV energy band to be made with unprecedented sensi tivity. Amongst its key scientific objectives are to understand part icle acceleration in Active Galactic Nuclei, Pulsars and Supernovae Remnants, to provide high resolution measurements of unidentified ga mma-ray sources, to study transient high energy emission from objects such as gamma-ray bursts, and to probe Dark Matter and the early Uni verse. Dr. McEnery will present an overview of the GLAST mission and its scientific goals.

  6. Exploring the High Energy Universe: GLAST Mission and Science

    NASA Technical Reports Server (NTRS)

    McEnery, Julie

    2007-01-01

    GLAST, the Gamma-Ray Large Area Space Telescope, is NASA's next-generation high-energy gamma-ray satellite scheduled for launch in Autumn 2007. GLAST will allow measurements of cosmic gamma-ray sources in the 10 MeV to 100 GeV energy band to be made with unprecedented sensitivity. Amongst its key scientific objectives are to understand particle acceleration in Active Galactic Nuclei, Pulsars and Supernovae Remnants, to provide high resolution measurements of unidentified gamma-ray sources, to study transient high energy emission from objects such as gamma-ray bursts, and to probe Dark Matter and the early Universe. Dr. McEnery will present an overview of the GLAST mission and its scientific goals.

  7. Radio detection of ultra-high energy cosmic neutrinos

    SciTech Connect

    Vieregg, Abigail G.

    2015-07-15

    Ultra-high energy (UHE) neutrino astronomy constitutes a new window of observation onto the UHE universe. The detection and characterization of astrophysical neutrinos at the highest energies (E> 10{sup 18} eV) would reveal the sources of high-energy cosmic rays, the highest energy particles ever seen, and would constrain the evolution of such sources over time. UHE neutrino astrophysics also allows us to probe weak interaction couplings at energies much greater than those available at particle colliders. One promising way of detecting the highest energy neutrinos is through the radio emission created when they interact in a large volume of dielectric, such as ice. Here I discuss current results and future efforts to instrument large volumes of detector material with radio antennas to detect, point back, and characterize the energy of UHE astrophysical neutrinos.

  8. TESTING THE ORIGIN OF HIGH-ENERGY COSMIC RAYS

    SciTech Connect

    Vladimirov, A. E.; Moskalenko, I. V.; Porter, T. A.; Johannesson, G.

    2012-06-10

    Recent accurate measurements of cosmic-ray (CR) protons and nuclei by ATIC-2, CREAM, and PAMELA reveal (1) unexpected spectral hardening in the spectra of CR species above a few hundred GeV per nucleon, (2) a harder spectrum of He compared to protons, and (3) softening of the CR spectra just below the break energy. These newly discovered features may offer a clue to the origin of the observed high-energy Galactic CRs. We discuss possible interpretations of these spectral features and make predictions for the secondary CR fluxes and secondary-to-primary ratios, anisotropy of CRs, and diffuse Galactic {gamma}-ray emission in different phenomenological scenarios. Our predictions can be tested by currently running or near-future high-energy astrophysics experiments.

  9. SAS-2 high-energy gamma-ray observations of the Vela pulsar

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Fichtel, C. E.; Kniffen, D. A.; Ogelman, H. B.

    1975-01-01

    The Second Small Astronomy Satellite (SAS-2) high-energy (in excess of 35 MeV) gamma-ray telescope has detected pulsed gamma-ray emission at the radio period from PSR 0833-45, the Vela pulsar, as well as an unpulsed flux from the Vela region. The pulsed emission consists of two peaks following the single radio peak by about 13 ms and 48 ms. The luminosity of the pulsed emission above 100 MeV from Vela is about 0.1 that of the pulsar NP 0532 in the Crab nebula, whereas the pulsed emission from Vela at optical wavelengths is less than 0.0002 that from the Crab. The relatively high intensity of the pulsed gamma-ray emission, and the double peak structure, compared with the single pulse in the radio emission, suggest that the high-energy gamma-ray pulsar emission may be produced under different conditions from those at lower energies.

  10. Research in High Energy Physics. Final report

    SciTech Connect

    Conway, John S.

    2013-08-09

    This final report details the work done from January 2010 until April 2013 in the area of experimental and theoretical high energy particle physics and cosmology at the University of California, Davis.

  11. The evolution of high energy accelerators

    SciTech Connect

    Courant, E.D.

    1989-10-01

    In this lecture I would like to trace how high energy particle accelerators have grown from tools used for esoteric small-scale experiments to gigantic projects being hotly debated in Congress as well as in the scientific community.

  12. New developments for high-energy astrophysics

    NASA Astrophysics Data System (ADS)

    Paul, J.

    2000-03-01

    Unlike nearly all branches of physics, founded on the elaboration and analysis of experiments, astronomy is, above all, a science of observation, based mainly on the detection and study of the electromagnetic radiation emitted by celestial bodies. If one excepts devices operating in the radio bands, nearly all instruments used in astrophysics are based on the detection of photons. This review intends to highlight recent developments in high-energy astronomy and astrophysics studies from ground and space observations (from the X-ray band up to high-energy γ-rays and neutrinos). Particular attention will be given not only to recent technologies of photodetection now at work in the field of high-energy astronomy and to emerging photodetection studies in progress for future missions, but also to advanced imaging techniques used in the high-energy domain, which beyond any doubt, constitutes the most arduous of new astronomical disciplines.

  13. Physics at high energy photon photon colliders

    SciTech Connect

    Chanowitz, M.S.

    1994-06-01

    I review the physic prospects for high energy photon photon colliders, emphasizing results presented at the LBL Gamma Gamma Collider Workshop. Advantages and difficulties are reported for studies of QCD, the electroweak gauge sector, supersymmetry, and electroweak symmetry breaking.

  14. High Energy Astrophysics Research and Programmatic Support

    NASA Technical Reports Server (NTRS)

    Angellini, L.

    1994-01-01

    This report reviews activities performed by members of the USRA contract team during the three months of the reporting period. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics.

  15. Stochastic reacceleration of relativistic electrons by turbulent reconnection: a mechanism for cluster-scale radio emission?

    NASA Astrophysics Data System (ADS)

    Brunetti, G.; Lazarian, A.

    2016-05-01

    In this paper, we investigate a situation where relativistic particles are reaccelerated diffusing across regions of reconnection and magnetic dynamo in super-Alfvenic, incompressible large-scale turbulence. We present an exploratory study of this mechanism in the intracluster medium (ICM). In view of large-scale turbulence in the ICM, we adopt a reconnection scheme that is based on turbulent reconnection and magnetohydrodynamics (MHD) turbulence. In this case, particles are accelerated and decelerated in a systematic way in reconnecting and magnetic-dynamo regions, respectively, and on longer time-scales undergo a stochastic process diffusing across these sites (similar to second-order Fermi). Our study extends on larger scales numerical studies that focused on the acceleration in and around turbulent reconnecting regions. We suggest that this mechanism may play a role in the reacceleration of relativistic electrons in galaxy clusters providing a new physical scenario to explain the origin of cluster-scale diffuse radio emission. Indeed differently from current turbulent reacceleration models proposed for example for radio haloes, this mechanism is based on the effect of large-scale incompressible and super-Alfvenic turbulence. In this new model, turbulence governs the interaction between relativistic particles and magnetic field lines that diffuse, reconnect and are stretched in the turbulent ICM.

  16. Sources and characteristics of acoustic emissions from mechanically stressed geologic granular media — A review

    NASA Astrophysics Data System (ADS)

    Michlmayr, Gernot; Cohen, Denis; Or, Dani

    2012-05-01

    The formation of cracks and emergence of shearing planes and other modes of rapid macroscopic failure in geologic granular media involve numerous grain scale mechanical interactions often generating high frequency (kHz) elastic waves, referred to as acoustic emissions (AE). These acoustic signals have been used primarily for monitoring and characterizing fatigue and progressive failure in engineered systems, with only a few applications concerning geologic granular media reported in the literature. Similar to the monitoring of seismic events preceding an earthquake, AE may offer a means for non-invasive, in-situ, assessment of mechanical precursors associated with imminent landslides or other types of rapid mass movements (debris flows, rock falls, snow avalanches, glacier stick-slip events). Despite diverse applications and potential usefulness, a systematic description of the AE method and its relevance to mechanical processes in Earth sciences is lacking. This review is aimed at providing a sound foundation for linking observed AE with various micro-mechanical failure events in geologic granular materials, not only for monitoring of triggering events preceding mass mobilization, but also as a non-invasive tool in its own right for probing the rich spectrum of mechanical processes at scales ranging from a single grain to a hillslope. We review first studies reporting use of AE for monitoring of failure in various geologic materials, and describe AE generating source mechanisms in mechanically stressed geologic media (e.g., frictional sliding, micro-crackling, particle collisions, rupture of water bridges, etc.) including AE statistical features, such as frequency content and occurrence probabilities. We summarize available AE sensors and measurement principles. The high sampling rates of advanced AE systems enable detection of numerous discrete failure events within a volume and thus provide access to statistical descriptions of progressive collapse of systems

  17. Elementary particle physics and high energy phenomena

    SciTech Connect

    Barker, A.R.; Cumalat, J.P.; de Alwis, S.P.; DeGrand, T.A.; Ford, W.T.; Mahanthappa, K.T.; Nauenberg, U.; Rankin, P.; Smith, J.G.

    1992-06-01

    This report discusses the following research in high energy physics: the properties of the z neutral boson with the SLD detector; the research and development program for the SDC muon detector; the fixed-target k-decay experiments; the Rocky Mountain Consortium for HEP; high energy photoproduction of states containing heavy quarks; and electron-positron physics with the CLEO II and Mark II detectors. (LSP).

  18. Nuclear diffractive structure functions at high energies

    SciTech Connect

    Marquet,C.; Kowalski, H.; Lappi, T.; Venugopalan, R.

    2008-08-08

    A future high-energy electron-ion collider would explore the non-linear weakly-coupled regime of QCD, and test the Color Glass Condensate (CGC) approach to high-energy scattering. Hard diffraction in deep inelastic scattering off nuclei will provide many fundamental measurements. In this work, the nuclear diffractive structure function F{sub 2,A}{sup D} is predicted in the CGC framework, and the features of nuclear enhancement and suppression are discussed.

  19. Probing QCD at high energy via correlations

    SciTech Connect

    Jalilian-Marian, Jamal

    2011-04-26

    A hadron or nucleus at high energy or small x{sub Bj} contains many gluons and may be described as a Color Glass Condensate. Angular and rapidity correlations of two particles produced in high energy hadron-hadron collisions is a sensitive probe of high gluon density regime of QCD. Evolution equations which describe rapidity dependence of these correlation functions are derived from a QCD effective action.

  20. New Instrumental Facilities to study High Energy Processes in the Sun, Interplanetary Space and their Effects in the Earth Atmosphere

    NASA Astrophysics Data System (ADS)

    Raulin, Jean-Pierre; Makhmutov, Vladimir

    We present a new instrumental facility to study the physical mechanisms of high-energy releases taking place in solar quiet and explosive active regions, and their signatures in the Earth's atmosphere. These facilities will be installed in the CASLEO (2550 m asl) observatory, and complement solar flare diagnostic obtained there at millimeter waves (45 and 90 GHZ), submillimeter waves (212 and 405 GHz), IR (30 THz), as well as X-ray radiation imprints in the ionosphere (VLF subionospheric propagation), and of energetic charged particles in Earth's atmosphere (Cosmic Ray CARPET sensor).Specifically, we propose to complement these existing instrumental facilities with a new detector of solar and atmospheric neutrons, a gamma-ray scintillation device, and ELF/VLF wave sensors. The main objectives are: (i) to better characterize the high-frequency radio and high-energy photon flare spectra, in order to provide new clues on the emission mechanism resulting in submillimeter and THz radiation which are still unexplained; (ii) to provide a continuous monitoring of solar energetic phenomena and investigate if they are more frequent than what we do observe nowadays; (iii) to investigate the causal relationship between atmospheric phenomena as lightning occurrence, high-energy photon and neutron production, Terrestrial Gamma-ray Flashes, and cosmic ray fluxes.

  1. The mechanism of modulation of geoacoustic emission intensity by weak electromagnetic fields in the audio-frequency range

    NASA Astrophysics Data System (ADS)

    Gavrilov, V. A.

    2016-07-01

    We propose a physical mechanism explaining the mechanism of modulation of the geoacoustic emission intensity by an external electromagnetic field in the audio-frequency range, which was previously revealed as a result of borehole measurements at the Petropavlovsk-Kamchatskii geodynamic testing area. It was established that electric double layers (EDL) at the interface between solid and liquid phases in a fluidsaturated geological medium play a key role in the mechanism proposed.

  2. A system for endoscopic mechanically scanned localized proton MR and light-induced fluorescence emission spectroscopies

    NASA Astrophysics Data System (ADS)

    Sonmez, Ahmet E.; Webb, Andrew G.; Spees, William M.; Ozcan, Alpay; Tsekos, Nikolaos V.

    2012-09-01

    Molecular and near-cellular modalities offer new opportunities in assessing living tissue in situ, and multimodality approaches, which offer complementary information, may lead to improved characterization of tissue pathophysiology benefiting diagnosis and focal therapy. However, many such modalities are limited by their low penetration through tissue, which has led to minimally invasive trans-cannula approaches to place the corresponding sensors locally at the area of interest. This work presents a system for performing localized fluorescence emission and proton magnetic resonance (MR) spectroscopies via endoscopic access. The in-house developed side-firing 1.9-mm wide dual-sensor integrates a three-fiber optical sensor for fluorescence emission optical spectroscopy and a 1-mm circular radiofrequency (RF) coil for localized MR proton spectroscopy. An MR-compatible manipulator was developed for carrying and mechanically translating the dual-sensor along a linear access channel. The hardware and software control of the system allows reconfigurable synchronization of the manipulator-assisted translation of the sensor, and MR and optical data collection. The manipulator serves as the mechanical link for the three modalities and MR images, MR spectra and optical spectra are inherently co-registered to the MR scanner coordinate system. These spectra were then used to generate spatio-spectral maps of the fluorophores and proton MR-signal sources in three-compartment phantoms with optically- and MR-visible, and distinguishable, materials. These data demonstrate a good spatial match between MR images, MR spectra and optical spectra along the scanned path. In addition to basic research, such a system may have clinical applications for assessing and characterizing cancer in situ, as well as guiding focal therapies.

  3. Probing the birth of fast rotating magnetars through high-energy neutrinos

    SciTech Connect

    Murase, Kohta; Meszaros, Peter; Zhang Bing

    2009-05-15

    We investigate the high-energy neutrino emission expected from newly born magnetars surrounded by their stellar ejecta. Protons might be accelerated up to 0.1-100 EeV energies possibly by, e.g., the wave dissipation in the winds, leading to hadronic interactions in the stellar ejecta. The resulting PeV-EeV neutrinos can be detected by IceCube/KM3Net with a typical peak time scale of a few days after the birth of magnetars, making the characteristic soft-hard-soft behavior. Detections would be important as a clue to the formation mechanism of magnetars, although there are ambiguities coming from uncertainties of several parameters such as velocity of the ejecta. Nondetections would also lead to useful constraints on the scenario.

  4. Experimental tests of a topside generation mechanism for auroral medium frequency burst radio emissions

    NASA Astrophysics Data System (ADS)

    Broughton, M.; Labelle, J. W.; Roberg-Clark, G. T.; McCready, M. A.; Bunch, N. L.; Weatherwax, A. T.

    2011-12-01

    The auroral zone is the source of multiple kinds of radio emissions that can be observed on the ground. The study of radio emissions offers a way to remotely sense space plasma processes and, in the case of auroral emissions, to use the auroral ionosphere as a large-scale plasma physics laboratory. Medium frequency (MF) burst is an impulsive radio emission at 1.5-4.5 MHz observed on the ground. Its generation mechanism is unknown, and it is often associated with the onset of substorms. Using continuous wave measurements, Bunch and LaBelle [2009] reported that MF burst is made up of both structured and unstructured features. The most commonly observed structured feature appears as a "backwards seven" on a time-frequency spectrogram. Recently, LaBelle [2011] proposed that MF bursts originate as Langmuir waves on the topside of the ionosphere that subsequently mode-convert into electromagnetic waves that are observed on the ground. We report two experimental tests of this theory. First, the theory predicts that the maximum frequency of MF burst must lie below the maximum ionospheric plasma frequency along the source magnetic field line. We have identified eleven instances where MF bursts were observed during operations of the Sondrestrom incoherent scatter radar near Kangerlussuaq, Greenland. A preliminary analysis of these data suggests that for all or nearly all eleven cases the maximum frequency of the MF burst lies below the maximum F-region plasma frequency inferred from the radar data. The second prediction of the theory concerns the "backwards seven" fine structures. The theory predicts that the lower frequency of a "backwards seven" fine structure must lie above the L-mode cutoff along the wave propagation path. Assuming a slab ionosphere, LaBelle [2011] found that this prediction held for the six fine structures reported by Bunch and LaBelle [2009]. In 2010, continuous wave measurements were made at South Pole Station, yielding over one hundred observations

  5. Phosphate glass useful in high energy lasers

    DOEpatents

    Hayden, Y.T.; Guesto-Barnak, D.

    1992-12-22

    Disclosed is a low-or no-silica, low- or no-alkali phosphate glass useful as a laser amplifier in a multiple pass, high energy laser system having a high thermal conductivity, K[sub 90 C] >0.85 W/mK, a low coefficient of thermal expansion, [alpha][sub 20-300 C] <80[times]10[sup [minus]7]/C, low emission cross section, [sigma]<2.5[times]10[sup [minus]20] cm[sup 2], and a high fluorescence lifetime, [tau]>325 [mu]secs at 3 wt. % Nd doping, consisting essentially of (on an oxide composition basis): (Mole %) P[sub 2]O[sub 5], (52-72); Al[sub 2]O[sub 3], (0-<20); B[sub 2]O[sub 3], (>0-25); ZnO, (0-31); Li[sub 2]O, (0-5); K[sub 2]O, (0-5); Na[sub 2]O, (0-5); Cs[sub 2]O, (0-5); Rb[sub 2]O, (0-5); MgO, (>0-<30); CaO, (0-20); BaO, (0-20); SrO, (0-<20); Sb[sub 2]O[sub 3], (0-<1); As[sub 2]O[sub 3], (0-<1); Nb[sub 2]O[sub 5], (0-<1); Ln[sub 2]O[sub 3], (up to 6.5); PbO, (0-<5); and SiO[sub 2], (0-3); wherein Ln[sub 2]O[sub 3] is the sum of lanthanide oxides; [Sigma]R[sub 2]O is <5, R being Li, Na, K, Cs, and Rb; the sum of Al[sub 2]O[sub 3] and MgO is <24 unless [Sigma]R[sub 2]O is 0, then the sum of Al[sub 2]O[sub 3] and MgO is <42; and the ratio of MgO to B[sub 2]O[sub 3] is 0.48-4.20. 7 figs.

  6. ROSAT: An international mission exploring the high energy universe

    NASA Technical Reports Server (NTRS)

    1991-01-01

    ROSAT was designed specifically to detect high energy radiation, by using its telescopes to study x ray and ultraviolet emissions, regions of the electromagnetic spectrum that cannot be seen and that cannot penetrate the Earth's atmosphere. ROSAT is an international astronomical observatory project. ROSAT's science mission is divided into two phases. With its in-orbit checkout period complete, ROSAT has begun phase one of its mission, an all sky survey to map the heavens. When the 6 month mapping survey is complete, the satellite will begin phase two and be pointed at selected objects, studying individual targets, for the remainder of its mission.

  7. Possible explanation for the low flux of high energy astrophysical muon neutrinos

    SciTech Connect

    Pakvasa, Sandip

    2013-05-23

    I consider the possibility that some exotic neutrino property is responsible for reducing the muon neutrino flux at high energies from distant sources; specifically, (i) neutrino decay and (ii) neutrinos being pseudo-Dirac particles. This would provide a mechanism for the lack of high energy muon events in the Icecube detector.

  8. A mechanism for biologically-induced iodine emissions from sea-ice

    NASA Astrophysics Data System (ADS)

    Boxe, C.

    2015-12-01

    Ground- and satellite-based measurements reported high concentrations of iodine monoxide (IO) in coastal Antarctica. The sources of such a large iodine burden in the coastal Antarctic atmosphere remain unknown. We propose a mechanism for iodine release from sea-ice based on the premise that micro-algae are the primary source of iodine emissions in this environment. The emissions are triggered by the biological production of iodide (I-) and hypoiodous acid (HOI) from micro-algae (contained within and underneath sea-ice) and their diffusion through sea-ice brine channels, to accumulate in a thin brine layer (BL) on the surface of sea-ice. Prior to reaching the BL, the diffusion timescale of iodine within sea-ice is depth-dependent. The BL is also a vital component of the proposed mechanism as it enhances the chemical kinetics of iodine-related reactions, which allows for the efficient release of iodine to the polar boundary layer. We suggest iodine is released to the atmosphere via 3 possible pathways: (1) emitted from the BL and then transported throughout snow atop sea-ice, to be released to the atmosphere; (2) released directly from the BL to the atmosphere in regions of sea-ice that are not covered with snowpack; or (3) emitted to the atmosphere directly through fractures in the sea-ice pack. To investigate the proposed biology-ice-atmosphere coupling at coastal Antarctica we use a multiphase model that incorporates the transport of iodine species, via diffusion, at variable depths, within brine channels of sea-ice. Model simulations were conducted to interpret observations of elevated springtime IO in the coastal Antarctic, around the Weddell Sea. While a lack of experimental and observational data adds uncertainty to the model predictions, nevertheless the results show that the levels of inorganic iodine (i.e., I2, IBr, ICl) released from sea-ice through this mechanism could account for the observed IO concentrations during this timeframe. The model results

  9. [High Energy Physics: Research in high energy physics]. Annual report, FY 1982

    SciTech Connect

    Barish, B C

    1982-12-31

    This report discusses high energy physics research on: Quantum chromodynamics; neutrinos; multiparticle spectrometers; inclusive scattering; Mark III detector; and cascade decays of phi resonances. (LSP)

  10. The quantum mechanics of ion-enhanced field emission and how it influences microscale gas breakdown

    SciTech Connect

    Li, Yingjie; Go, David B.

    2014-09-14

    The presence of a positive gas ion can enhance cold electron field emission by deforming the potential barrier and increasing the tunneling probability of electrons—a process known as ion-enhanced field emission. In microscale gas discharges, ion-enhanced field emission produces additional emission from the cathode and effectively reduces the voltage required to breakdown a gaseous medium at the microscale (<10 μm). In this work, we enhance classic field emission theory by determining the impact of a gaseous ion on electron tunneling and compute the effect of ion-enhanced field emission on the breakdown voltage. We reveal that the current density for ion-enhanced field emission retains the same scaling as vacuum cold field emission and that this leads to deviations from traditional breakdown theory at microscale dimensions.

  11. The Fe II Emission in Active Galactic Nuclei: Excitation Mechanisms and Location of the Emitting Region

    NASA Astrophysics Data System (ADS)

    Marinello, M.; Rodríguez-Ardila, A.; Garcia-Rissmann, A.; Sigut, T. A. A.; Pradhan, A. K.

    2016-04-01

    We present a study of Fe ii emission in the near-infrared region (NIR) for 25 active galactic nuclei (AGNs) to obtain information about the excitation mechanisms that power it and the location where it is formed. We employ an NIR Fe ii template derived in the literature and find that it successfully reproduces the observed Fe ii spectrum. The Fe ii bump at 9200 Å detected in all objects studied confirms that Lyα fluorescence is always present in AGNs. The correlation found between the flux of the 9200 Å bump, the 1 μm lines, and the optical Fe ii implies that Lyα fluorescence plays an important role in Fe ii production. We determined that at least 18% of the optical Fe ii is due to this process, while collisional excitation dominates the production of the observed Fe ii. The line profiles of Fe ii λ10502, O i λ11287, Ca ii λ8664, and Paβ were compared to gather information about the most likely location where they are emitted. We found that Fe ii, O i and Ca ii have similar widths and are, on average, 30% narrower than Paβ. Assuming that the clouds emitting the lines are virialized, we show that the Fe ii is emitted in a region twice as far from the central source than Paβ. The distance, though, strongly varies: from 8.5 light-days for NGC 4051 to 198.2 light-days for Mrk 509. Our results reinforce the importance of the Fe ii in the NIR to constrain critical parameters that drive its physics and the underlying AGN kinematics, as well as more accurate models aimed at reproducing this complex emission.

  12. Scientific applications for high-energy lasers

    SciTech Connect

    Lee, R.W.

    1994-03-01

    The convergence of numerous factors makes the time ripe for the development of a community of researchers to use the high-energy laser for scientific investigations. This document attempts to outline the steps necessary to access high-energy laser systems and create a realistic plan to implement usage. Since an academic/scientific user community does not exist in the USA to any viable extent, we include information on present capabilities at the Nova laser. This will briefly cover laser performance and diagnostics and a sampling of some current experimental projects. Further, to make the future possibilities clearer, we will describe the proposed next- generation high-energy laser, named for its inertial fusion confinement (ICF) goal, the multi-megaJoule, 500-teraWatt National Facility, or NIF.