X ray Emission

In our experiments, we irradiated solid CH targets with a 400 J, 5 ps, 3ϫ10 19 W/cm 2 laser, and we used x-ray imaging and spectroscopic diagnostics to monitor the keV x-ray emission from thin Al or Au tracer layers buried within the targets. The experiments were designed to quantify the spatial distribution of the thermal electron temperature and density as a function of buried layer depth; these data provide insights into the behavior of relativistic electron currents which flow within the solid target and are directly and indirectly responsible for the heating. We measured ϳ200-350 eV temperatures and near-solid densities at depths ranging from 5 to 100 m beneath the target surface. Time-resolved x-ray spectra from Al tracers indicate that the tracers emit thermal x rays and cool slowly compared to the time scale of the laser pulse. Most intriguingly, we consistently observe annular x-ray images in all buried tracer-layer experiments, and these data show that the temperature distribution is columnar, with enhanced heating along the edges of the column. The ring diameters are much greater than the laser focal spot diameter and do not vary significantly with the depth of the tracer layer for depths greater than 30 m. The local temperatures are 200-350 eV for all tracer depths. We discuss recent simulations of the evolution of electron currents deep within solid targets irradiated by ultrahigh-intensity lasers, and we discuss how modeling and analytical results suggest that the annular patterns we observe may be related to locally strong growth of the Weibel instability. We also suggest avenues for future research in order to further illuminate the complex physics of relativistic electron transport and energy deposition inside ultra-high-intensity laser-irradiated solid targets.

Gamma-ray astronomy explores the most energetic photons in nature to address some of the most pressing puzzles in contemporary astrophysics. It encompasses a wide range of objects and phenomena: stars, supernovae, novae, neutron stars, stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays and relativistic-particle acceleration, and the evolution of galaxies. MeV gamma-rays provide a unique probe of nuclear processes in astronomy, directly measuring radioactive decay, nuclear de-excitation, and positron annihilation. The substantial information carried by gamma-ray photons allows us to see deeper into these objects, the bulk of the power is often emitted at gamma-ray energies, and radioactivity provides a natural physical clock that adds unique information. New science will be driven by time-domain population studies at gamma-ray energies. This science is enabled by next-generation gamma-ray instruments with one to two orders of magnitude better sensitivity,...

Spectropolarimetry of the Type Ib SN 2008D, associated with the XRF 080109, at two separate epochs, are presented. The epochs of these observations correspond to V-band light curve maximum and 15 days after light curve maximum (or 21 and 36 days after the XRF). We find SN 2008D to be significantly polarized, although the largest contribution is due to the interstellar polarization component of Q IS P = 0 ± 0.1% and U IS P = -1.2 ± 0.1%. At the two epochs, the spectropolarimetry of SN 2008D is classified as being D1+L(He I)+L(Ca II). The intrinsic polarization of continuum wavelength regions is < 0.4%, at both epochs, implying an asymmetry of the photosphere of < 10%. Similar to other Type Ibc SNe, such as 2005bf, 2006aj and 2007gr, we observed significant polarization corresponding to the spectral features of Ca II, He I, Mg I, Fe II and, possibly, O I λ7774, about a close-to-sphericallysymmetric photosphere. We introduce a new plot showing the chemically distinct line forming regions in the ejecta and comment on the apparent ubiquity of highly polarized high-velocity Ca II features in Type Ibc SNe. The polarization angle of Ca II IR triplet was significantly different, at both epochs, to those of the other species, suggesting high-velocity Ca II forms in a separate part of the ejecta. The apparent structure in the outer layers of SN 2008D has implications for the interpretation of the early-time X-ray emission associated with shock break-out. We present two scenarios, within the jet-torus paradigm, which explain the lack of an apparent geometry discontinuity between the two observations: 1) a jet which punched a hole straight through the progenitor and deposited Ni outside the ejecta and 2) a jet which stalled inside the radius of the photosphere as observed at the second epoch. The lack of a peculiar polarization signature, suggesting strongly asymmetric excitation of the ejecta, and the reported properties of the shock-breakout favour the second scenario.

X pinches employed for x-ray generation represent excellent objects to study the details of plasma pinch processes. An X pinch is produced by passing a high current through two or more metal wires that cross and touch at a single point in the middle. During its evolution, the X-pinch forms in the middle a small Z pinch that is unstable and forms a cascade of smaller and denser necks. In the final phase, the pinch disrupts and produces extremely short and localized bursts of intense soft x-ray radiation, followed immediately by a ˜ 1 ns burst of higher energy x-rays that is attributed to energetic electrons accelerated in the gaps that appear in the X-pinch plasma structure after its soft x-ray burst. The behavior of the energetic particles that produce intense x-rays requires a kinetic description. Using a simplified kinetic approach and available results of recent MHD simulations, we will discuss the dynamics of energetic electron and ion beams formed around the central axis of the...

Seven gold artefacts found in the same cultural and chronological context in the archaeological site of Roca Vecchia, Southern Italy, have been analyzed in air by proton induced X-ray emission at CEDAD, the AMS-IBA facility of the University of Lecce, Italy. The age of the artefacts has been also indirectly determined by carrying out AMS radiocarbon analyses on short lived organic materials archaeologically associated with the studied objects. The measurements confirmed that the artefacts were formed by a native alloy with a gold concentration ranging from 83.10 to 88.51 wt%. The compositional homogeneity of the artefacts seems to confirm the hypothesis of a common metalworking and origin of the raw materials.

Se revisan las diferencias físicas que existen entre superburbujas y supervientos galácticos. Los dos eventos resultan de la energética producida por grandes brotes de formacíon estelar. Sin embargo los supervientos galácticos permiten el escape de los metales recién procesados por el brote estelar hacia el medio intergaláctico, mientras que las superburbujas al no llegar a alcanzar el borde de su galaxia anfitriona retienen a los nuevos metales con los que más tarde enriquecerán su medio interestelar. Se evalúan por lo mismo las principales propiedades de brotes masivos de formación estelar así como la tasa mínima de energía mecánica que un starburst ha de producir para causar la expulsión de su material recién procesado fuera de su galaxia anfitriona, tanto en el caso de galaxias con alta rotación que presenten un disco aplanado, como para el caso de galaxias con una rotación menor que imponen un límite ordenes de magnitud más energético. Se establecen los límites para galaxias con una masa de material interestelar que va de 10 6 M a más de 10 9 M y estos son comparados con un grupo de galaxias locales. Algunas de estas galaxias aparecen por encima del límite crítico de eyección de masa a pesar de que su estructura es la predicha teóricamente como típica de una superburbuja. Se muestra también que verdaderos supervientos galácticos, como es el caso de M82, exceden el límite crítico por más de un orden de magnitud, lo que implica que el ímite establecido por Silich & Tenorio-Tagle (2001) es una cota inferior.

Se evalúa la tasa mínima de energía mecánica que un starburst ha de producir para causar la expulsión de su material recién procesado fuera de su galaxia anfitriona. Para ello resumimos primeramente las propiedades a esperarse de grupos de estrellas masivas así como la hidrodinámica que inducen en el medio interestelar. Nuestras estimaciones resultan de una especial atención a la presión que causa el medio intergaláctico en el que la galaxia en consideración se encuentra, así como también a la rotación de la componente gaseosa. Tomamos en consideración estos hechos así como una componente oscura que domina el potencial gravitacional y desarrollamos una solución autoconsistente para la distribución de la masa gaseosa. Nuestros resultados estan en excelente acuerdo con los obtenidos por Mac Low & Ferrara (1999) para galaxias con un medio interestelar que despliega una distribución de disco aplanado y una baja presión intergaláctica (P IGM /k ≤ 1 cm -3 K). Sin embargo, nuestra solución requiere de una importante mayor tasa de energía cuando se consideran ya sea una mayor presión del medio intergaláctico, o la posible existencia de un halo extendido de baja rotación y baja densidad. Los pasos a seguir para llegar a la mezcla de elementos pesados con el medio interestelar así como la escala de tiempo que requieren son también sumarizados en esta contribución.

3C 400.2 is a supernova remnant (SNR) with a complex morphology consisting of two overlapped shells of different diameters: a large shell at the southeast and a small shell at the northwest. High-resolution radio-continuum observations carried out by Dubner et al. (1994) suggested that this complex morphology could be due to the interaction of two SNRs. However, this view has been challenged by recent studies of the H I distribution around this SNR (Giacani et al. 1998) and by the confrontation of theoretical evolutionary models with the morphology at H alpha of this remnant (Velazquez et al. 2001). These recent results suggest that the double shell structure is produced by a single supernova explosion initially expanding into a dense medium encountering a lower density medium and producing a blowout. In this work we present the results of H alpha Fabry-Perot observations obtained with the PUMA equipment at the 2.1 m telescope of the Observatorio Astronómico Nacional at San Pedro Má...

We present new HST/WFPC2 observations of 20 fields centered around T Tauri stars in the Chamaeleon I star forming region. Images have been obtained in the F631N ([OI]λ6300), F656N (Hα) and F673N ([SII]λλ6716, 6731) narrowband filters, plus the Johnson V-band equivalent F547M filter. We detect 31 T Tauri stars falling within our fields. We discuss the optical morphology of 10 sources showing evidence of either binarity, circumstellar material, or mass loss. We supplement our photometry with a compilation of optical, infrared and sub-millimeter data from the literature, together with new sub-mm data for three objects, to build the Spectral Energy Distributions (SED) of 19 single sources. Using an SED model fitting tool, we self-consistently estimate a number of stellar and disk parameters, while mass accretion rates are directly derived from our Hα photometry. We find that bolometric luminosities derived from dereddened optical data tend to be underestimated in systems with high α 2-24 IR spectral index, suggesting that disks seen nearly edge-on may occasionally be interpreted as low luminosity (and therefore more evolved) sources. On the other hand, the same α 2-24 IR spectral index, a tracer of the amount of dust in the warmer layers of the circumstellar disks, and the mass accretion rate appear to decay with the isocronal stellar age, suggesting that the observed age spread (≃ 0.5 -5 Myr) within the cluster is real. Our sample contains a few outliers that may have dissipated their circumstellar disks on shorter time-scale.

We present the results of synoptic high-resolution imaging studies of two active binary star systems. Both were conducted using the VLBA-HSA at 15 GHz, making them the first images of extrasolar stars capable of discerning structure at scales smaller than a stellar ...

In this paper we present new H 21cm spectral line images of the poor group of late type galaxies, Holmberg 124 made using archival data from the Giant Metrewave Radio Telescope (GMRT). Holmberg 124 is a group of four late type galaxies: NGC 2805, NGC 2814, NGC 2820 and Mrk 108. We detect spectral line emission from all the four galaxies and note several signatures of tidal interactions among the member galaxies. Our results for the triplet (namely NGC 2820, NGC 2814 and Mrk 108) confirm the earlier results of notably the detection of a possible tidal dwarf galaxy to the north-east of NGC 2820. Further, in these images where the pointing center of the observations was changed, we have recovered most of the H emission in NGC 2805 as compared to . We also report possible detection of small discrete clouds between NGC 2820 and NGC 2805 which might be stripped H in the intragroup medium (IGrM). However, these need confirmation. The H distribution of NGC 2805 is asymmetric with peak H column densities seen along the southern spiral arm and along a northern arc. Diffuse H is seen from the entire optical galaxy and extends much further in the southern parts, especially in the south-west. An abrupt fall in H column densities is observed to the south of NGC 2820 which is a high inclination galaxy and to the north of NGC 2805 which is a low inclination galaxy. Vigorous star formation has been observed along the southern spiral arm of NGC 2805. Based on these new H images, we support the scenario given by Kantharia et al. ( ) that both tidal interactions and ram pressure are currently playing a role in the evolution of the triplet galaxies. From the observed northern H arc and extensive star formation in the southern spiral arm of NGC 2805 and additionally the systemic velocities of the four galaxies, we suggest ram pressure effects are also playing a role in the evolution of NGC 2805. We believe that the H in the north of NGC 2805 is being compressed as it moves in the IGrM and that it is moving along a direction in the north-east close to the line-of-sight so that the entire disk is encountering the IGrM. This interaction with the IGrM would have triggered

Einstein (1936) predicted the phenomenon presently known as gravitational lensing (GL). A prime feature of GL is the magnification, because of the gravitational field, of the star visible surface as seen from a distant observer. We show here that nonlinear electrodynamics (NLED) modifies in a fundamental basis Einstein&#39;s general relativistic (GR) original derivation. The effect becomes apparent by studying the light propagation from a strongly magnetic (B) pulsar (SMP). Unlike its GR counterpart, the photon dynamics in NLED leads to a new effective GL, which depends also on the B-field permeating the pulsar. The apparent radius of a SMP appears then unexpectedly diminished, by a large factor, as compared to the classical Einstein&#39;s prediction. This may prove very crucial in determining physical properties of high B-field stars from their X-ray emission.

The x-ray spectra produced from 7.0-keV electrons in bombardment of thick targets of silver and gold have been measured using a Si͑Li͒ detector at 90°to the incident electron-beam direction. The spectra were corrected for electron backscattering, energy loss, photon attenuation in the target, and for inherent filtration, allowing a determination of absolute intensity for x-ray emission. The experimental spectra have been compared with two models, ͑i͒ a modified Kramers formula, and ͑ii͒ a semiempirical expression. There is an overall agreement between the experiment and the predictions of the models both for the shape and for the absolute magnitude of the thick-target bremsstrahlung intensity to within 21%. ͓S1050-2947͑96͒05708-3͔

We report the discovery of a dwarf Seyfert 1 active galactic nucleus (AGN) with a candidate intermediate-mass black hole hosted by the dwarf galaxy SDSS J160531.84+174826.1 at z = 0.032. A broad component of the Hα line with FWHM=781km s -1 is detected in its optical spectrum, and a bright, point-like nucleus is evident from a HST imaging observation. Non-thermal X-ray emission is also detected from the nucleus. The black hole mass, as estimated from the luminosity and width of the broad Hα component, is about 7 × 10 4 M ⊙ . The host galaxy appears to be a disk galaxy with a boxy bulge or nuclear bar; with an absolute magnitude of M R = -17.8, it is among the least luminous host galaxies ever identified for a Seyfert 1.

We report on our results of X-ray spectral analysis for a sample of radio-loud quasars covering a wide range of the radio core-dominance parameter, R, from coredominated to lobe-dominated objects, using data obtained mostly with the XMM-Newton Observatory. We find that the spectral shape of the underlying power-law continuum is flat even for the lobe-dominated objects (average photon index ∼ 1.5), indistinguishable from that of core-dominated quasars. For lobe-dominated objects, contribution of X-rays from the jets is expected to be very small based on previous unification schemes, more than one order of magnitude lower than the observed X-ray luminosities. Assuming that radio-loud quasars follow the same X-ray-UV/optical luminosity relation for the disk-corona emission as found for radio-quiet quasars, we estimate the X-ray flux contributed by the disk-corona component from the optical/UV continuum. We find that neither the luminosity, nor the spectral shape, of the disk-corona X-ray emission can account for the bulk of the observed X-ray properties. Thus in lobe-dominated quasars, either the disk-corona X-ray emission is much enhanced in strength and flatter in spectral shape (photon index ∼ 1.5) compared to normal radio-quiet quasars, or their jet X-ray emission is much enhanced compared to their weak radio core-jet emission. If the latter is the case, our result may imply that the jet emission in X-rays is less Doppler beamed than that in the radio. As a demonstrating example, we test this hypothesis by using a specific model in which the X-ray jet has a larger opening angle than the radio jet.

The article touches upon the relations of some parameters (mass, radius) of the central supermassive Black Holes (SMBH) and parent galaxies. The definite patterns of these relations are revealed which apparently played an important role in the process of the formation and evolution of galaxies. Most likely, galaxies and their central black holes have common and joint origin and their physical characteristics are always mutually conditioned… Key words: galaxy, supermassive black holes, radius of gravitational capture (radius Bondi), gravitational radius. The observations of the last decades showed that at the center of many galaxies there are supermassive black holes (SMBH). [1] In order to study their role and meaning in the formation and evolution of mother galaxies it is important to compare and determine the dependence and relations of some of their physical features. And, first of all, relations of their masses. Radius Bondi, according to the definition, is , where T is the temperature of the interstellar medium. Supposing that the temperature of the interstellar medium is equal to the virial temperature of the galaxy (which occurs frequently), it can be found that 𝑘𝑇 𝑚 𝑝

This paper presents Far-Ultraviolet Spectroscopic Explorer (FUSE ) medium-resolution slit and Chandra X-Ray Observatory ACIS-S observations of the high-excitation planetary nebula NGC 246. The Ne v k1146 and [Ne v] k3426 emission lines, the latter obtained in a previous investigation, indicate that the nebula is photoionized by the intense UV radiation of the central object and has a temperature of $20,000 K. The O vi k1032 and k1037 emission lines are moderately optically thick and probably contain contributions from both collisional excitation and radiative scattering of the UV continuum of the central star. The Chandra observation did not detect any X-ray emission from the nebula, but did detect the central star. The absence of nebular X-ray emission and the photoionized nature of the nebula support the hypothesis that the nebula contains a biconical cavity, which extends to the edge of the nebula. In this geometry the stellar wind does not shock the nebular material, resulting only in a cool photoionized plasma. The X-ray spectrum of the central object is consistent with NLTE models for PG 1159Ytype stars.

A study on X-ray emission from a low energy (3.3 kJ) plasma focus (PF) device operated with hydrogen is reported. X-rays (X-n) are detected by using an X-ray detector consisting of three Quantrad Si PIN-diodes with differential filtering and with a pinhole camera. The X-ray yield in different energy windows is measured as a function of hydrogen filling pressure. The maximum yield in 4p-geometry is found to be 46.6 J and corresponding wall plug efficiency for X-ray generation is 1.40%. In particular, to demonstrate feasibility of the present PF as a high intensity flash X-ray source for good contrast biological radiography, an X-ray radiogram of a fish, is presented. The fine structure of the specimen can be seen in different parts. The PF, because of its high X-ray yield and good reproducibility is particularly suited for this application.

Gated X-Ray imagers have been used on many ICF experiments around the world for time resolved imaging of the target implosions. DIXI (Dilation X-ray Imager) is a new fixed base diagnostic that has been developed for use in the National Ignition Facility. The DIXI diagnostic utilizes pulse-dilation technology and uses a high magnification pinhole imaging system to project images onto the instrument. DIXI is located outside the NIF target chamber approximately 6.5m from target chamber center (TCC). The pinholes are located 10cm from TCC and are aligned to the DIXI optical axis using a diagnostic instrument manipulator (DIM) on an adjacent port. By use of an extensive lead and poly shielded drawer enclosure DIXI is capable of collecting data at DT neutron yields up to Yn~ 10 16 on CCD readout and up to Yn~ 10 17 on film. Compared to existing pinhole x-ray framing cameras DIXI also provides a significant improvement in temporal resolution, <10ps, and the ability to capture a higher density of images due to the fact the pinhole array does not require collimators. The successful deployment of DIXI on the NIF required careful attention to the following subsystems, pinhole imaging, debris shielding, filtering and image plate (FIP), EMI protection, large format CsI photocathode design, detector head, detector head electronics, control electronics, CCD, film recording and neutron shielding. Here we discuss the initial design, improvements implemented after rigorous testing, infrastructure and commissioning of DIXI on the NIF.

In order to investigate the far-infrared excess detected from the west hot spot of the radio galaxy Pictor A with the Herschel observatory, a submillimeter photometry is performed with the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeter Array at Band 8 with the reference frequency of 405 GHz. A submillimeter source is discovered at the radio peak of the hot spot. Because the 405 GHz flux density of the source, 80.7 ± 3.1 mJy, agrees with the extrapolation of the synchrotron radio spectrum, the far-infrared excess is suggested to exhibit no major contribution at the ACA band. In contrast, by subtracting the power-law spectrum tightly constrained by the radio and ACA data, the significance of the excess in the Herschel band is well confirmed. No diffuse submillimeter emission is detected within the ACA field of view, and thus, the excess is ascribed to the west hot spot itself. In comparison to the previous estimate based on the Herschel data, the relative contribution of the far-infrared excess is reduced by a factor of ∼ 1.5. The spectrum of the excess below the far-infrared band is determined to be harder than that of the diffusive shock acceleration. This strengthens the previous interpretation that the excess originates via the magnetic turbulence in the substructures within the hot spot. The ACA data are utilized to evaluate the magnetic field strength of the excess and of diffuse radio structure associated to the hot spot.

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/LAT. 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 longduration central engine activity as their power source.

The Sloan Digital Sky Survey (SDSS) will provide the data to support detailed investigations of the distribution of luminous and non-luminous matter in the Universe: a photometrically and astrometrically calibrated digital imaging survey of π steradians above about Galactic latitude 30 • in five broad optical bands to a depth of g ∼ 23 m , and a spectroscopic survey of the approximately 10 6 brightest galaxies and 10 5 brightest quasars found in the photometric object catalog produced by the imaging survey. This paper summarizes the observational parameters and data products of the SDSS, and serves as an introduction to extensive technical on-line documentation.

We have studied La0.8MnO3 single crystal manganite films with varying thickness (from 4000 å to 50 å) on LaAlO3 substrates. We measured the Mn Kbeta x-ray emission spectrum, which is sensitive to the crystal field about the Mn sites. Our high-resolution x-ray emission results showed there exists a strong crystal field in manganite films near the substrate due to substrate

Galaxy clusters are the largest virialized objects in the universe. Their merger dynamics and their interactions with the cosmic filaments that connect them are important for our understanding of the formation of large-scale structure. In addition, cosmic filaments are thought to possess the missing baryons in the universe. Studying the interaction of galaxy clusters and filaments therefore has the potential to unveil the the origin of the baryons and the physical processes that occur during merger stages of galaxy clusters. In this paper, we study the connection between A3395 and the intercluster filament with NuSTAR, XMM-Newton, and Suzaku data. Since the NuSTAR observation is moderately contaminated by scattered light, we present a novel technique developed for disentangling this background from the emission from the intracluster medium. We find that the interface of the cluster and the intercluster filament connecting A3395 and A3391 does not show any signs of heated plasma, as was previously thought. This interface has low temperature, high density, and low entropy, thus we suggest that the gas is cooling, being enhanced by the turbulent or tidal 'weather' driven during the early stage of the merger. Furthermore, our temperature results from the NuSTAR data are in agreement with those from XMM-Newton, and from joint NuSTAR and XMM-Newton analysis for a region with ∼25% scattered light contamination within 1σ. We show that the temperature constraint of the intracluster medium is valid even when the data are contaminated up to ∼25% for ∼5 keV cluster emission.

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

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

We present results of analysis of a M1.0 class flare event of 12 June, 2014 (SOL2014-06-12T21:12), observed with the NASA&#39;s Interface Region Imaging Spectrograph (IRIS) mission and New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO). The IRIS observed this event in the coarse raster mode and obtained high-resolution UV spectra and Slit-Jaw (SJ) images for almost the whole flaring region. Our analysis of the IRIS data in different spectral lines reveals strong redshifted fluxes of the chromospheric material before the flare. It is also found that most of the chromospheric and transition region lines are redshifted across the flaring region during the flare. Expansion of a photospheric flux-rope structure is observed in the high-resolution images from the NST with the Broadband Filter Imager (BFI) using the TiO filter. Emission of the hot (20 MK) coronal Fe XXI line is detected ~400 seconds after the emission peaks of the lower temperature lines in the O I IRIS spectral...

It is shown that X-ray absorption can be considerably enhanced at resonant energies corresponding to K-shell excitation into higher shells with electron vacancies following Auger emissions in high-Z elements and compounds employed in biomedical applications. We calculate Auger resonant probabilities and cross sections to obtain total mass attenuation coefficients with resonant cross sections and detailed resonance structures corresponding to KR, Kβ, Kγ, Kδ, and Kη complexes lying between 6.4-7.1 keV in iron and 67-80 keV in gold. The basic parameters were computed using the relativistic atomic structure codes and the R-matrix codes. It is found that the average enhancement at resonant energies is up to a factor of 1000 or more for associated K f L, M, N, O, P transitions. The resonant energies in high-Z elements such as gold are sufficiently high to ensure significant penetration in body tissue, and hence the possibility of achieving X-radiation dose reduction commensurate with resonant enhancements for cancer theranostics using high-Z nanoparticles and molecular radiosensitizing agents embedded in malignant tumors. The in situ deposition of X-ray energy, followed by secondary photon and electron emission, will be localized at the tumor site. We also note the relevance of this work to the development of novel monochromatic or narrow-band X-ray emission sources for medical diagnostics and therapeutics. † Part of the "Russell M. Pitzer Festschrift".

Colliding Wolf-Rayet (WR) winds produce thermal X-ray emission widely observed by X-ray telescopes. In wide WR+O binaries, such as WR 140, the X-ray flux is tied to the orbital phase, and is a direct probe of the winds' properties. In the Galactic center, $\sim$30 WRs orbit the super massive black hole (SMBH) within $\sim$10", leading to a smorgasbord of wind-wind collisions. To model the X-ray emission of WR 140 and the Galactic center, we perform 3D hydrodynamic simulations to trace the complex gaseous flows, and then carry out 3D radiative transfer calculations to compute the variable X-ray spectra. The model WR 140 RXTE light curve matches the data well for all phases except the X-ray minimum associated with periastron, while the model spectra agree with the RXTE hardness ratio and the shape of the Suzaku observations throughout the orbit. The Galactic center model of the Chandra flux and spectral shape match well in the region r$<$3", but the model flux falls off too rapidly beyond this radius.

The colliding wind binary (CWB) systems η Carinae and WR140 provide unique laboratories for X-ray astrophysics. Their wind-wind collisions produce hard X-rays that have been monitored extensively by several X-ray telescopes, including RXTE. To interpret these RXTE X-ray light curves, we apply 3D hydrodynamic simulations of the wind-wind collision using smoothed particle hydrodynamics (SPH). We find adiabatic simulations that account for the absorption of X-rays from an assumed point source of X-ray emission at the apex of the wind-collision shock cone can closely match the RXTE light curves of both η Car and WR140. This point-source model can also explain the early recovery of η Car's X-ray light curve from the 2009.0 minimum by a factor of 2-4 reduction in the mass loss rate of η Car. Our more recent models account for the extended emission and absorption along the full wind-wind interaction shock front. For WR140, the computed X-ray light curves again match the RXTE observations quite well. But for η Car, a hot, post-periastron bubble leads to an emission level that does not match the extended X-ray minimum observed by RXTE. Initial results from incorporating radiative cooling and radiative forces via an anti-gravity approach into the SPH code are also discussed.

The colliding wind binary (CWB) systems η Carinae and WR140 provide unique laboratories for X-ray astrophysics. Their wind-wind collisions produce hard X-rays that have been monitored extensively by several X-ray telescopes, including RXTE. To interpret these RXTE X-ray light curves, we apply 3D hydrodynamic simulations of the wind-wind collision using smoothed particle hydrodynamics (SPH). We find adiabatic simulations that account for the absorption of X-rays from an assumed point source of X-ray emission at the apex of the wind-collision shock cone can closely match the RXTE light curves of both η Car and WR140. This point-source model can also explain the early recovery of η Car&#39;s X-ray light curve from the 2009.0 minimum by a factor of 2-4 reduction in the mass loss rate of η Car. Our more recent models account for the extended emission and absorption along the full wind-wind interaction shock front. For WR140, the computed X-ray light curves again match the RXTE observatio...

We report continued monitoring of the superluminous binary system η Car by the Proportional Counter Array on the Rossi X-ray Timing Observatory (RXTE) through the 2009 X-ray minimum. The RXTE campaign shows that the minimum began on 2009 January 16, consistent with the phasings of the two previous minima, and overall, the temporal behavior of the X-ray emission was similar to that observed by RXTE in the previous two cycles. However, important differences did occur. The 2-10 keV X-ray flux and X-ray hardness decreased in the 2.5 year interval leading up to the 2009 minimum compared to the previous cycle. Most intriguingly, the 2009 X-ray minimum was about 1 month shorter than either of the previous two minima. During the egress from the 2009 minimum the X-ray hardness increased markedly as it had during egress from the previous two minima, although the maximum X-ray hardness achieved was less than the maximum observed after the two previous recoveries. We suggest that the cycle-to-cycle variations, especially the unexpectedly early recovery from the 2009 X-ray minimum, might have been the result of a decline in η Car's wind momentum flux produced by a drop in η Car's mass loss rate or wind terminal velocity (or some combination), though if so the change in wind momentum flux required to match the X-ray variation is surprisingly large.

The electronic structure of the single molecule magnet system {M [Fe(L 1 )2]3}•4CHCl3 (M = Fe, Cr ; L 1 = CH3N(CH2CH2O)2 2-) has been studied using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, soft X-ray emission spectroscopy, as well as theoretical density functionalbased methods. There is good agreement between theoretical calculations and experimental data. The valence band mainly consists of three bands between 2 eV and 30 eV. Both theory and experiments show that the top of the valence band is dominated by the hybridization between Fe 3d and O 2p bands. From the shape of the Fe 2p spectra it is argued that Fe in the molecule is most likely in the 2+ charge state. Its neighboring atoms (O, N) exhibit a magnetic polarisation yielding effective spin S=5/2 per iron atom, giving a high spin state molecule with a total S=5 effective spin for the case of M = Fe.

Context. The blazar 3C 454.3 is one of the most active sources from the radio to the γ-ray frequencies observed in the past few years. Aims. We present multiwavelength observations of this source from April 2008 to March 2010. The radio to optical data are mostly from the GASP-WEBT, UV and X-ray data from Swift, and γ-ray data from the AGILE and Fermi satellites. The aim is to understand the connection among emissions at different frequencies and to derive information on the emitting jet. Methods. Light curves in 18 bands were carefully assembled to study flux variability correlations. We improved the calibration of optical-UV data from the UVOT and OM instruments and estimated the Lyα flux to disentangle the contributions from different components in this spectral region. Results. The observations reveal prominent variability above 8 GHz. In the optical-UV band, the variability amplitude decreases with increasing frequency due to a steadier radiation from both a broad line region and an accretion disc. The optical flux reaches nearly the same levels in the 2008-2009 and 2009-2010 observing seasons; the mm one shows similar behaviour, whereas the γ and X-ray flux levels rise in the second period. Two prominent γ-ray flares in mid 2008 and late 2009 show a double-peaked structure, with a variable γ/optical flux ratio. The X-ray flux variations seem to follow the γ-ray and optical ones by about 0.5 and 1 d, respectively. Conclusions. We interpret the multifrequency behaviour in terms of an inhomogeneous curved jet, where synchrotron radiation of increasing wavelength is produced in progressively outer and wider jet regions, which can change their orientation in time. In particular, we assume that the long-term variability is due to this geometrical effect. By combining the optical and mm light curves to fit the γ and X-ray ones, we find that the γ (X-ray) emission may be explained by inverse-Comptonisation of synchrotron optical (IR) photons by their parent relativistic electrons (SSC process). A slight, variable misalignment between the synchrotron and Comptonisation zones would explain the increased γ and X-ray flux levels in 2009-2010, as well as the change in the γ/optical flux ratio during the outbursts peaks. The time delays of the X-ray flux changes after the γ, and optical ones are consistent with the proposed scenario.

Context. The quasar 3C 279 is among the most extreme blazars in terms of luminosity and variability of flux at all wavebands. Its variations in flux and polarization are quite complex and therefore require intensive monitoring observations at multiple wavebands to characterise and interpret the observed changes. Aims. In this paper, we present radio-to-optical data taken by the WEBT, supplemented by our VLBA and RXTE observations, of 3C 279. Our goal is to use this extensive database to draw inferences regarding the physics of the relativistic jet. Methods. We assemble multifrequency light curves with data from 30 ground-based observatories and the space-based instruments SWIFT (UVOT) and RXTE, along with linear polarization vs. time in the optical R band. In addition, we present a sequence of 22 images (with polarization vectors) at 43 GHz at resolution 0.15 milliarcsec, obtained with the VLBA. We analyse the light curves and polarization, as well as the spectral energy distributions at different epochs, corresponding to different brightness states. Results. We find that the IR-optical-UV continuum spectrum of the variable component corresponds to a power law with a constant slope of -1.6, while in the 2.4-10 keV X-ray band it varies in slope from -1.1 to -1.6. The steepest X-ray spectrum occurs at a flux minimum. During a decline in flux from maximum in late 2006, the optical and 43 GHz core polarization vectors rotate by ∼300 • . Conclusions. The continuum spectrum agrees with steady injection of relativistic electrons with a power-law energy distribution of slope -3.2 that is steepened to -4.2 at high energies by radiative losses. The X-ray emission at flux minimum comes most likely from a new component that starts in an upstream section of the jet where inverse Compton scattering of seed photons from outside the jet is important. The rotation of the polarization vector implies that the jet contains a helical magnetic field that extends ∼20 pc past the 43 GHz core.

to ~20 attoliters (1 al = 10 -18 l), and nearfield scanning optical microscopy (NSOM, panel D) , which allows attoliter detection volumes. NSOM is best suited to cellsurface studies where scanning is important. Single-molecule detection in reduced detection volumes can also be achieved with stimulated emission depletion (STED, panel E) . With this method, detection volumes have been reduced to 0.67 attoliters (11). The detection volume can be placed anywhere in solution, including inside a cell. However, use of STED with more than one color of fluorophore is difficult, and the STED beam is of high intensity. Another possibility is the use of nanofluidic channels to restrict the movement of molecules to a width and depth smaller than the confocal detection volume (panel F) (13). Molecules would not be near metal surfaces, and diffusion times would be longer because diffusion would be effectively one-dimensional. Finally, if superresolution lenses can be made from materials with a negative index of refraction, they may in the future be used for single-molecule detection in small volumes (14). All these methods have strengths in different areas and are suitable for different applications. The strength of the zero-mode waveguide of Levene et al. ( ) is that it allows parallel detection of many single molecules while providing the smallest detection volumes of any method reported to date, enabling single-molecule analysis of much weaker interactions than previously possible.

High dynamic range, space-resolved X-ray spectra of an aluminum laser–plasma in the 5.5–8 Å range were obtained using a TlAP crystal and a cooled CCD camera as a detector. This technique was used to investigate the emission region in the longitudinal direction over a distance of approximately 350 μm from the solid target surface. These data show that the electron density profile varies by two orders of magnitude with the temperature ranging from about 180 eV in the overdense region to about 650 eV in the underdense region. Accordingly, different equilibria take place across the explored region which can be identified with this experimental technique. Detailed studies on highly ionized atomic species in different plasma conditions can therefore be performed simultaneously under controlled conditions.

Pulsar Wind Nebula Pulsar wind nebulae are the result of the interaction between the wind of relativistic charged particles emitted by pulsars and their surrounding interstellar medium. Using the AGILE satellite, Pellizzoni et al. (p. 663 , published online 31 December) detected extended gamma-ray emission between 100 megaelectron volts and 3 gigaelectron volts from the 10,000-year-old Vela pulsar wind nebula. This detection sets constraints on the relativistic particle wind of pulsars, its energetic content, and its interactions with the surrounding medium. It also suggests that pulsar wind nebulae could form a subset of the yet unidentified galactic gamma-ray sources.

We present Spitzer Infrared Spectrograph and Infrared Array Camera observations of the young supernova remnant E0102 (SNR 1E0102-7219) in the Small Magellanic Cloud. The infrared spectra show strong lines of Ne and O, with the [Ne ii] line at 12.8 μm having a large velocity dispersion of 2000-4500 km s -1 indicative of fast-moving ejecta. Unlike the young Galactic SNR Cas A, E0102 lacks emission from Ar and Fe. Diagnostics of the observed [Ne iii] line pairs imply that [Ne iii] emitting ejecta have a low temperature of 650 K, while [Ne v] line pairs imply that the infrared [Ne v] emitting ejecta have a high density of ∼10 4 cm -3 . We have calculated radiative shock models for various velocity ranges including the effects of photoionization. The shock model indicates that the [Ne v] lines come mainly from the cooling zone, which is hot and dense, whereas [Ne ii] and [Ne iii] come mainly from the photoionization zone, which has a low temperature of 400-1000 K. We estimate an infrared-emitting Ne ejecta mass of 0.04 M from the infrared observations, and discuss implications for the progenitor mass. The spectra also have a dust continuum feature peaking at 18 μm that coincides spatially with the ejecta, providing evidence that dust formed in the expanding ejecta. The 18 μm peak dust feature is fitted by a mixture of MgSiO 3 and Si dust grains, while the rest of the continuum requires either carbon or Al 2 O 3 grains. We measure the total dust mass formed within the ejecta of E0102 to be ∼0.014 M . The dust mass in E0102 is thus a factor of a few smaller than that in Cas A. The composition of the dust is also different, showing relatively less silicate and likely no Fe-bearing dust, as is suggested by the absence of Fe-emitting ejecta.

Effects of ballooning and radial oscillations of coronal magnetic loops on the modulations of microwave and X-ray emission from flare loops are considered. The damping mechanisms of loop MHD modes are analyzed. The method for diagnostics of flare plasma parameters using peculiarities of the microwave and X-ray pulsations is proposed. The diagnostic method was applied for two solar flares: on May 8, 1998 and August 28, 1999 observed with the Nobeyama Radioheliograph.

Radio observations allow us to probe the nature of low mass objects, including ultracool dwarfs. Additionally, very long baseline interferometric observations provide the highest angular resolution in astronomy to date, which opens a window to measure dynamical masses of these objects in order to benchmark evolutionary models. We present here a multi-epoch, multi-frequency study of the substellar triple system VHS 1256-1257. We have found radio emission at 6 GHz and 33 GHz coincident with the expected position of the central binary of VHS 1256-1257. No emission is detected at higher frequencies (230 GHz and 345 GHz) nor at 5 GHz with VLBI arrays. The emission appears to be stable over almost 3 years at 6 GHz. These results can be well explained by non-thermal gyrosynchrotron emission originating at radiation belts present in both components and viewed equatorially. We also share preliminary results from our VLA observations of 5 low-mass binary systems and EVN observations of 4 ultracool dwarfs (including a binary).

For Classical T Tauri Stars (CTTSs), the resonance doublets of N v, Si iv, and C iv, as well as the He ii 1640 Å line, trace hot gas flows and act as diagnostics of the accretion process. In this paper we assemble a large high-resolution, high-sensitivity data set of these lines in CTTSs and Weak T Tauri Stars (WTTSs). The sample comprises 35 stars: 1 Herbig Ae star, 28 CTTSs, and 6 WTTSs. We find that the C iv, Si iv, and N v lines in CTTSs all have similar shapes. We decompose the C iv and He ii lines into broad and narrow Gaussian components (BC and NC). The most common (50%) C iv line morphology in CTTSs is that of a low-velocity NC together with a redshifted BC. For CTTSs, a strong BC is the result of the accretion process. The contribution fraction of the NC to the C iv line flux in CTTSs increases with accretion rate, from ∼20% to up to ∼80%. The velocity centroids of the BCs and NCs are such that V BC ≳ 4 V NC, consistent with the predictions of the accretion shock model, in...

Monoclinic and hexagonal pyrrhotites leached in 1 mol/L HCl and exposed to the air at 100% and ϳ10% relative humidity for up to 5 months were studied using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy, Mo ¨ssbauer spectroscopy, and electron paramagnetic resonance (EPR). The amorphous, nonequilibrium, iron-depleted layer (NL) produced by the leaching amounted to half of the residue mass and was composed of predominantly low-spin ferrous iron and polysulfide anions. Elemental sulfur and goethite were the only crystalline products of the NL decomposition. FTIR spectroscopy and XPS also revealed several sulfoxy species and, at low humidity, a small amount of ferric oxide. Neither alterations of the underlying pyrrhotite nor new iron sulfide phases (pyrite, pyrrhotite, etc.) crystallized from the amorphous NL were found. The NL decomposition was faster in the wet environment than in the dry one, and the oxidation of the NL was much more rapid than that of starting pyrrhotites. The intensity and quadruple split of the Mo ¨ssbauer signal from the product (an isomer shift of 0.36 mm/s) were found to increase over the aging, indicating that the NL structure becomes more rigid and the singlet Fe(II) gradually converts to Fe(III). X-ray Fe L␣,␤ emission spectra showed the formation of intermediate, high-spin Fe(II) within the NL oxidized in the humid environment, but not in the dry air. No unpaired electron spins were detected by EPR; lines of paramagnetic Fe 3ϩ appeared after the samples were aged in the dry air for 49 d and even later in the humid atmosphere. These phenomena are explained in terms of the formation of defects with negative correlation energy, similar to noncrystalline semiconductor chalcogenides, and of the fast electron exchange between the iron species, respectively. Mechanisms for reactions involved with the weathering of iron sulfides, which take into consideration the NL lattice elasticity, S-S and S-O bonding, oxygen incorporation, and oxidative and spin state of iron, are discussed. It is suggested in particular that the surface layer, strongly enriched in sulfur, as well as elemental sulfur and ferric oxyhydroxides, do not inhibit sulfide oxidation and acid production under weathering conditions, but the partially oxidized, disordered, nonstoichiometric layer may be passive.

X-ray resonance lines between 11 Å and 17 Å emitted from iron plasmas created by a modest KrF laser have been simulated by modifying the atomic and hydrodynamic code EHYBRID. Free-free and free-bound emission from the Si-, Al-, Mg-, Na-, Ne-and F-like ions is calculated in the simulation. In the original experiments, a KrF laser (249 nm wavelength) with focused irradiances between 1 × 10 12 W/cm 2 and 1 × 10 15 W/cm 2 was focused on iron targets. The laser pulse duration was varied between 10 ps and 20 ns. We have calculated X-ray conversion efficiencies to be, for example, 0.5% over 2π sr for 2 × 10 13 W/cm 2 and 20 ns pulse duration, in good agreement with experimental measurements. The simulation of X-ray emission is also presented for an experiment where a train of eight 7 ps KrF laser pulses is incident onto an iron target.

We present an application of valence to core X-ray emission spectroscopy to understand the electronic structure of the industrially relevant catalysts titanium silicalite-1. The experimental spectrum was modelled within density functional theory, adopting a one electron approach, investigating the effects of different basis sets, density functionals and cluster sizes. The description of titanium silicalite-1 valence states follows the Kohn-Sham evaluation of the molecular orbitals involved in the computed transitions. The relevance of X-ray emission spectroscopy (XES) in the fields of chemistry and material science for the investigation of the ligand environment of 3d transition metals (TM) is well reported. We provide in the following a brief review. XES can be induced as a second order optical process (photon-in/photon-out): (i) a core electron is removed by an incident photon, then (ii) the inner shell vacancy is filled by an electron from a higher shell following the selection rules for radiative transitions. When the core hole is filled by an electron from a valence level, we refer to valence to core XES (VtC-XES). The formal VtC-XES final state electronic configuration (i.e. hole in the valence band) is identical to the one reached by valence electron photoemission spectroscopy: Xray/ultraviolet photoemission spectroscopy (PES). PES is a photon-in/electron-out technique, frequently used for chemical characterization of surfaces. Due to the large electron cross section mostly electrons originating from the superficial layers can leave the material. Furthermore PES is commonly performed in ultra high vacuum (UHV) conditions. The UHV restriction can be overcome with pressure up to mbars and high kinetic energy PES allows for depth profiling. XES, in the hard X-ray range, is a truly bulk sensitive technique and is readily performed in ambient or even high pressure conditions. Furthermore, XES is an element selective tool, i.e. only electron density at the metal site (ligands included) is probed. The theoretical interpretation was shown to be surprisingly simple. The VtC-XES spectrum, also referred to as Kβ satellite lines, splits into the Kβ" (also called cross-over peak) and Kβ 2,5 regions, that arise from transitions involving orbitals that are primarily located on the metal centre ligands and so directly reflect the configuration of the electron orbitals that participate in the chemical bonds. 9, Glatzel, 2005 #132 The applicability and thus importance of VtC-XES is due to the fact that it does not strictly require synchrotron radiation facilities, but can be performed using laboratory X-ray sources, radioactive isotopes 10- 12 and ion beam 13 laboratory sources. It is well established that the obtained spectra can be interpreted by means of density functional theory (DFT) calculations within a one electron approximation where no full multiplet structure, 15 core hole potential and multi-electronic processes 7 (shake-up/down) are taken into account. The chosen basis set and density functional influence the shape of the DFT computed VtC-XES spectrum. We investigated the occupied valence molecular orbitals of the catalyst Ti silicalite-1 16 (TS-1). We present a systematic study of the effect of different basis sets, density functionals and cluster sizes used to mimic the

In this paper, we study a sample of 65 short duration bursts contained in the 3B catalogue. We fit the time profiles of these GRBs with lognormal functions and study various temporal properties. In most of the multi-peaked bursts, our analysis leads to a statistical evidence for the evolution of temporal asymmetry in individual pulses i.e. subsequent pulses in a GRB, on an average, tend to be more symmetric. Using a peak asymmetry evolution parameter, we find that 90% of short duration GRBs with 3 or more peaks exhibit the above trend individually.

In this paper, we study a sample of 65 short duration bursts contained in the 3B catalogue. We fit the time profiles of these GRBs with lognormal functions and study various temporal properties. In most of the multi-peaked bursts, our analysis leads to a statistical evidence for the evolution of temporal asymmetry in individual pulses i.e. subsequent pulses in a GRB, on an average, tend to be more symmetric. Using a peak asymmetry evolution parameter, we find that 90% of short duration GRBs with 3 or more peaks exhibit the above trend individually.