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Cataclysmic Variables (CVs) are compact binaries with white dwarf (WD) primaries. CVs and other accreting WD binaries (AWBs) are useful laboratories for studying accretion flows, gas dynamics, outflows, transient outbursts, and explosive nuclear burning under different astrophysical plasma conditions. They have been studied over decades and are important for population studies of galactic X-ray sources. Recent space- and ground-based high resolution spectral and timing studies, along with recent surveys indicate that we still have observational and theoretical complexities yet to answer. I review accretion in nonmagnetic AWBs in the light of X-ray observations. I present X-ray diagnostics of accretion in dwarf novae and the disk outbursts, the nova-like systems, and the state of the research on the disk winds and outflows in the nonmagnetic CVs together with comparisons and relations to classical and recurrent nova systems, AM CVns and Symbiotic systems. I discuss how the advective hot accretion flows (ADAF-like) in the inner regions of accretion disks (merged with boundary layer zones) in nonmagnetic CVs explain most of the discrepancies and complexities that have been encountered in the X-ray observations. I stress how flickering variability studies from optical to X-rays can be probes to determine accretion history and disk structure together with how the temporal and spectral variability of CVs are related to that of LMXBs and AGNs. Finally, I discuss the nature of accretion in nonmagnetic WDs in terms of ADAF-like accretion flows, and elaborate on the solutions it brings and its complications, constructing an observational framework to motivate new theoretical calculations that introduce this flow-type in disks, outflow and wind models together with disk-instability models of outbursts and nova outbursts in AWBs and WD physics, in general. [ABSTRACT FROM AUTHOR]

Among hard X-ray Galactic sources detected with the Swift and INTEGRAL surveys, those discovered as accreting white dwarf binaries have surprisingly boosted in number in the recent years. The majority are identified as magnetic Cataclysmic Variables of the Intermediate Polar type, suggesting this subclass as an important constituent of the Galactic population of X-ray sources. We here review and discuss the X-ray emission properties of newly discovered sources in the framework of an identification programme with the XMM-Newton satellite that increased the sample of this subclass by a factor of two. [ABSTRACT FROM AUTHOR]

An equation for the relation between the X-ray source size and focal spot size of a single-bounce ellipsoidal glass monocapillary X-ray condenser (SBEGMXC) was constructed. According to this equation, a method by measuring the focal spot size of an SBEGMXC was used to determine the average slope error of the SBEGMXC, and this method based on an X-ray source with an adjustable source size. Compared with the existing methods for measuring the slope error of an SBEGMXC, this method could be used to obtain the average of slope errors originating from every point on the inner surface of the SBEGMXC. [ABSTRACT FROM AUTHOR]

The linear response is the key property employed by a radiation detector to determine the accurate intensity of a pulse radiation field. In this study, we investigated the high fluence rate response behavior of a LaBr 3 scintillator. We used a high-intensity pulsed X-ray source called “QiangGuang-I” which could produce an X-ray pulse with a total dose of 100 Gy, full width at half maximum of 20 ± 5 ns, and an average energy of 1 MeV, to test the linear response of the LaBr 3 scintillator. The Lissajous figure method was used in this experiment. The results showed that the fluence rate linear response limit was more than 1.8 × 10 20 MeV/(cm 2 ·s). [ABSTRACT FROM AUTHOR]

We review all the models proposed for the progenitor systems of Type Ia supernovae and discuss the strengths and weaknesses of each scenario when confronted with observations. We show that all scenarios encounter at least a few serious difficulties, if taken to represent a comprehensive model for the progenitors of all Type Ia supernovae (SNe Ia). Consequently, we tentatively conclude that there is probably more than one channel leading SNe Ia. While the single-degenerate scenario (in which a single white dwarf accretes mass from a normal stellar companion) has been studied in some detail, the other scenarios will need a similar level of scrutiny before any firm conclusions can be drawn. [ABSTRACT FROM AUTHOR]

Ionising radiation can induce giant-nucleated cells (GCs) in the progeny of irradiated populations, as demonstrated in various cellular systems. Most in vitro studies have utilised quiescent cancerous or normal cell lines but it is not clear whether radiation-induced GCs persist in the progeny of normal replicated cells. In the current work we show persistent induction of GCs in the progeny of normal human-diploid skin fibroblasts (AG1522). These cells were originally irradiated with a single equivalent clinical dose of 0.2, 1 or 2 Gy of either X-ray or proton irradiation and maintained in an active state for various post-irradiation incubation interval times before they were replated for GC analysis. The results demonstrate that the formation of GCs in the progeny of X-ray or proton irradiated cells was increased in a dose-dependent manner when measured 7 days after irradiation and this finding is in agreement with that reported for the AG1522 cells using other radiation qualities. For the 1 Gy X-ray doses it was found that the GC yield increased continually with time up to 21 days post-irradiation. These results can act as benchmark data for such work and may have important implications for studies aimed at evaluating the efficacy of radiation therapy and in determining the risk of delayed effects particularly when applying protons. [ABSTRACT FROM AUTHOR]

In the extragalactic sky, microquasars and ultra-luminous X-ray sources (ULXs) are known as energetic compact objects locating at off-nucleus positions in galaxies. Some of these objects are associated with expanding bubbles with a velocity of 80–250 km s − 1 . We investigate the shock acceleration of particles in those expanding nebulae. The nebulae having fast expansion velocity ≳ 120 km s − 1 are able to accelerate cosmic rays up to ∼100 TeV. If 10% of the shock kinetic energy goes into particle acceleration, powerful nebulae such as the microquasar S26 in NGC 7793 would emit gamma rays up to several tens TeV with a photon index of ∼2. These nebulae will be good targets for future Cherenkov Telescope Array observations given its sensitivity and angular resolution. They would also contribute to ∼7% of the unresolved cosmic gamma-ray background radiation at ≥ 0.1 GeV. In contrast, particle acceleration in slowly expanding nebulae ≲ 120 km s − 1 would be less efficient due to ion-neutral collisions and result in softer spectra at ≳ 10 GeV. [ABSTRACT FROM AUTHOR]

This paper describes the Polarization Spectroscopic Telescope Array ( PolSTAR ), a mission proposed to NASA’s 2014 Small Explorer (SMEX) announcement of opportunity. PolSTAR measures the linear polarization of 3–50 keV (requirement; goal: 2.5–70 keV) X-rays probing the behavior of matter, radiation and the very fabric of spacetime under the extreme conditions close to the event horizons of black holes, as well as in and around magnetars and neutron stars. The PolSTAR design is based on the technology developed for the Nuclear Spectroscopic Telescope Array ( NuSTAR ) mission launched in June 2012. In particular, it uses the same X-ray optics, extendable telescope boom, optical bench, and CdZnTe detectors as NuSTAR . The mission has the sensitivity to measure ∼1% linear polarization fractions for X-ray sources with fluxes down to ∼5 mCrab. This paper describes the PolSTAR design as well as the science drivers and the potential science return. [ABSTRACT FROM AUTHOR]

HESS J1841-055 is a diffuse unidentified gamma-ray source with the size of ∼1°.3 × 1°. No conclusive counterpart in other wavelengths has so far detected. To search for X-rays responsible for the TeV emission, the Suzaku observations were conducted, which covered a half region of the HESS source. In the soft band (0.5–2.0 keV), we discovered a diffuse emission, Suzaku J1840.2-0552, with the size of ∼ 10 ′ . Since its spectrum was fitted by an optically thin thermal plasma model, Suzaku J1840.2-0552 is likely to be a supernova remnant. We also discovered an extended source, Suzaku J1840.2-0544, in the hard band (2.0–8.0 keV) with an emission line at 6.1 keV. From the spectral feature and large interstellar absorption, this source is likely to be a cluster of galaxies behind the Galactic plane at the red-shift of ∼0.09. The other diffuse source spatially overlaps with the SNR candidate G26.6-0.2, which shows a non-thermal dominant spectrum. Since no other candidate is found in the hard X-ray band, we infer that these largely extended sources could be possible counterparts of HESS J1841-055. [ABSTRACT FROM AUTHOR]

We discuss the development of a compact X-ray source based on inverse-Compton scattering with a laser-driven electron beam. This source produces a beam of high-energy X-rays in a narrow cone angle (5–10 mrad), at a rate of 10 8 photons-s −1 . Tunable operation of the source over a large energy range, with energy spread of ∼50%, has also been demonstrated. Photon energies >10 MeV have been obtained. The narrowband nature of the source is advantageous for radiography with low dose, low noise, and minimal shielding. [ABSTRACT FROM AUTHOR]

X-ray emission from pyroelectric sources can be produced through non-contact thermal cycling using induction heating. In this study, we demonstrated a proof of concept non-contact x-ray source powered via induction heating. An induction heater operating at 62.5 kHz provided a total of 6.5 W of delivered peak thermal power with 140 V DC of driving voltage. The heat was applied to a ferrous substrate mechanically coupled to a cubic 1 cm 3 Lithium Niobate (LiNbO 3 ) pyroelectric crystal maintained in a 3–12 mTorr vacuum. The maximum temperature reached was 175 °C in 86 s of heating. The cooling cycle began immediately after heating and was provided by passive radiative cooling. The total combined cycle time was 250 s. x-ray photons were produced and analyzed in both heating and cooling phases. Maximum photon energies of 59 keV and 55 keV were observed during heating and cooling, respectively. Non-contact devices such as this, may find applications in cancer therapy (brachytherapy), non-destructive testing, medical imaging, and physics education fields. [ABSTRACT FROM AUTHOR]

Radiation of supersoft X-ray sources (SSS) dominates both the supersof X-ray and the far-UV domain. A fraction of their radiation can be reprocessed into the thermal nebular emission, seen in the spectrum from the near-UV to longer wavelengths. In the case of symbiotic X-ray binaries (SyXBs) a strong contribution from their cool giants is indicated in the optical/near-IR. In this paper I introduce a method of multiwavelength modelling the spectral energy distribution (SED) of SSSs from the supersoft X-rays to the near-IR with the aim to determine the physical parameters of their composite spectra. The method is demonstrated on two extragalactic SSSs, the SyXB RX J0059.1-7505 (LIN 358) in the Small Magellanic Cloud (SMC), RX J0439.8-6809 in the Large Magellanic Cloud (LMC) and two Galactic SSSs, the classical nova RX J2030.5+5237 (V1974 Cyg) during its supersoft phase and the classical symbiotic star RX J1601.6+6648 (AG Dra) during its quiescent phase. The multiwavelength approach overcomes the problem of the mutual dependence between the temperature, luminosity and amount of absorption, which appears when only the X-ray data are fitted. Thus, the method provides an unambiguous solution. It was found that selection of the model (a blackbody or an atmospheric model) is not of crucial importance in fitting the global X-ray/IR SED. The multiwavelength modelling of the SED of SSSs is essential in determining their physical parameters. [ABSTRACT FROM AUTHOR]

I modeled the 14 Å–37 μ m SED of the recurrent symbiotic nova RS Oph during its supersoft source (SSS) phase and the following quiescent phase. During the SSS phase, the model SEDs revealed the presence of a strong stellar and nebular component of radiation in the spectrum. The former was emitted by the burning WD at highly super-Eddington rate, while the latter represented a fraction of its radiation reprocessed by the thermal nebula. During the transition phase, both the components were decreasing and during quiescence the SED satisfied radiation produced by a large, optically thick disk ( R disk > 10 R ⊙ ). The super-Eddington luminosity of the burning WD during the SSS phase was independently justified by the high quantity of the nebular emission. The emitting material surrounded the burning WD, and its mass was ( 1.6 ± 0.5 ) × 10 - 4 ( d / 1.6 kpc ) 5 / 2 M ⊙ . The helium ash, deposited on the WD surface during the whole burning period, was around of 8 × 10 - 6 ( d / 1.6 kpc ) 2 M ⊙ , which yields an average growing rate of the WD mass, M ̇ WD ∼ 4 × 10 - 7 ( d / 1.6 kpc ) 2 M ⊙ yr - 1 . The mass accreted by the WD between outbursts, m acc ∼ 1.26 × 10 - 5 M ⊙ , constrains the average accretion rate, M ̇ acc ∼ 6.3 × 10 - 7 M ⊙ yr - 1 . During quiescence, the accretion rate from the model SED of ∼ 2.3 × 10 - 7 M ⊙ yr - 1 requires a super-Eddington accretion from the disk at ∼ 3.6 × 10 - 5 M ⊙ yr - 1 during the outburst. Such a high accretion can be responsible for the super-Eddington luminosity during the whole burning phase. Simultaneous presence of jets supports this scenario. If the wind from the giant is not sufficient to feed the WD at the required rate, the accretion can be realized from the disk-like reservoir of material around the WD. In this case the time between outbursts will extend, with the next explosion beyond 2027. In the opposite case, the wind from the giant has to be focused to the orbital plane to sustain the high accretion rate at a few × 10 - 7 M ⊙ yr - 1 . Then the next explosion can occur even prior to 2027. [ABSTRACT FROM AUTHOR]

The microbeam system at Tohoku University has been applied to various fields since its installation and is mainly used for biological applications. The primary purpose of this work was to develop a 3D μ-CT, in which a microbeam is used as a monoenergetic point X-ray source. The second one was to develop a microbeam analysis system for biological samples. A beam spot of 0.4×0.4μm2 at a beam current of several tens of pA has been produced. However, in our set-up, μ-PIXE/RBS analyses demand beam currents of ca. 100pA, which restricts the spatial resolution to around 1×1μm2. In order to get higher spatial resolution down to several hundred nm and higher beam current with a several μm resolution, a triplet lens system was designed and newly installed. This upgrade was carried out simultaneously with the recovery from the damage caused by the great east Japan earthquake. The triplet lens system has larger demagnification and was designed by adding a quadrupole lens to the existing doublet system. Although a beam spot size of 2×1μm2 is currently obtained, it has not achieved the performance obtained by the previous doublet system. The doublet system has been recovered to its previous performance and is routinely applied to simultaneous μ-PIXE/RBS analysis in various fields. Recent applications of 3D-PIXE-μ-CT of toxic elements in single cells with the new microbeam system are presented. [ABSTRACT FROM AUTHOR]

Abstract: We present spectral properties of a total of 996 discrete X-ray sources resolved in a sample of 23 dusty early-type galaxies selected from different environments. The combined X-ray luminosity function of all the 996 sources within the optical of the sample galaxies is well described by a broken power law with a break at 2.71×1038 ergs−1 and is close to the Eddington limit for a 1.4 neutron star. Out of the 996, about 63% of the sources have their X-ray luminosities in the range between few ×1037 to 2.0×1039 ergs−1 and are like normal LMXBs; about 15–20% with luminosities

Abstract: The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope provides both direct and indirect measurements of galactic cosmic rays (CR). The LAT high-statistics observations of the 7GeV – 1TeV electron plus positron spectrum and limits on spatial anisotropy constrain models for this cosmic-ray component. On a galactic scale, the LAT observations indicate that cosmic-ray sources may be more plentiful in the outer Galaxy than expected or that the scale height of the cosmic-ray diffusive halo is larger than conventional models. Production of cosmic rays in supernova remnants (SNR) is supported by the LAT γ-ray studies of several of these, both young SNR and those interacting with molecular clouds. [Copyright &y& Elsevier]

Abstract: Observational studies on solar flares with footpoints partially occulted by the solar limb provide an important method for diagnostics of coronal hard X-ray emissions. The statistics of hard X-ray sources in 71 such flares observed by RHESSI (Reuven Ramaty High-Energy Solar Spectroscopic Imager) show that the two kinds of hard X-ray sources proposed in previous studies (i.e., the sources with respectively a smaller and larger spatial separations between the thermal and non-thermal sources of coronal hard X-ray emissions) have no evident difference in the aspects of their photon spectra, images, light curves, GOES durations, etc. The area of the radiation region, the flare''s total thermal energy and GOES duration are well correlated with the distance of separation. These results support some unified models of solar flares proposed in recent years, and indicate that the Masuda flare is only a kind of special event, which does not possess the general features of coronal hard X-ray emissions [Copyright &y& Elsevier]

Abstract: We present the first public database of high-energy observations of all known Galactic supernova remnants (SNRs). In Section we introduce the rationale for this work motivated primarily by studying particle acceleration in SNRs, and which aims at bridging the already existing census of Galactic SNRs (primarily made at radio wavelengths) with the ever-growing but diverse observations of these objects at high-energies (in the X-ray and -ray regimes). In Section we show how users can browse the database using a dedicated web front–end (http://www.physics.umanitoba.ca/snr/SNRcat). In Section we give some basic statistics about the records we have collected so far, which provides a summary of our current view of Galactic SNRs. Finally, in Section , we discuss some possible extensions of this work. We believe that this catalogue will be useful to both observers and theorists, and timely with the synergy in radio/high-energy SNR studies as well as the upcoming new high-energy missions. A feedback form provided on the website will allow users to provide comments or input, thus helping us keep the database up-to-date with the latest observations. [Copyright &y& Elsevier]

Abstract: Radio and gamma-ray emissions in Active Galactic Nuclei (AGNs) are both related to the presence of relativistic particles in jets. With the advent of the Fermi Large Area Telescope (LAT), and thanks to its large sensitivity up to several GeV, many observational results are changing our understanding of these phenomena. BL Lac objects, which made up only a fraction of the known extragalactic gamma-ray source population before Fermi, have now become the most abundant class. However, since they are relatively weak radio sources, most of them are poorly known as far as their parsec scale structure and multi-wavelength properties are concerned. For this reason, we have selected a complete sample of 42 low redshift BL Lacs (independently of their gamma-ray properties) to study with a multi-wavelength (radio, optical, X-ray, gamma-ray) approach. Here, we present results and images of sources in the sample (most of which have never been observed before), using new VLBA observations at 8 and 15GHz. Beyond this sample of BL Lacs, the population of gamma-ray AGNs has also dramatically enlarged in the Fermi era, permitting us to discuss the presence of a correlation between radio and gamma-ray properties with improved statistical significance. We explore the radio-gamma relation with several hundreds sources and using both simultaneous and archival radio data, thus tackling the impact of time variability. [Copyright &y& Elsevier]

Abstract: MIRRORCLE is a tabletop synchrotron light source being investigated within an EC funded project named LABSYNC. To evaluate the potential of this novel x-ray source for medical imaging applications, a set of measurements was performed at the MIRRORCLE factory in Japan. In particular, the aim of this work was to characterize the proposed compact x-ray source by determining different parameters, such as the intensity of the broad spectra produced with thin wire targets, the size of the focal spot and its distribution. The average electron-beam impact current on wire targets was calculated by several methods and it was demonstrated to be in the range . By comparing these values with data available for conventional x-ray tubes, the current needed to achieve the same fluence as in a standard diagnostic examination was estimated to be about 0.1–0.5mA. Finally, results from the measurements of the electron-beam impact cross-section on the target suggested that the diameter of the electron beam circulating in the storage ring is about 6mm. [Copyright &y& Elsevier]

Abstract: Ultraluminous X-ray sources (ULXs) are accreting black holes that may contain the missing population of intermediate mass black holes or reflect super-Eddington accretion physics. Ten years of Chandra and XMM-Newton observations of ULXs, integrated by multiband studies of their counterparts, have produced a wealth of observational data and phenomenological classifications. We review the properties of their host galaxies, list popular spectral models and implications for standard and supercritical accretion physics, demonstrate how X-ray timing of these objects places constraints on their masses. We also review multiwavelength studies of ULXs, including the optical emission of the binary system and nebulosity around them. We summarize that three classes of black holes could power ULXs: normal stellar mass black holes (∼10M ⊙), massive stellar black holes (≲100M ⊙), and intermediate mass black holes (102–104 M ⊙). We collect evidence for the presence of these three types of compact objects, including caveat of each interpretation, and briefly review their formation processes. [Copyright &y& Elsevier]

Abstract: We present results from Swift, XMM-Newton, and deep INTEGRAL monitoring in the region of GRB 050925. This short Swift burst is a candidate for a newly discovered soft gamma-ray repeater (SGR) with the following observational burst properties: (1) galactic plane (b =−0.1°) localization, (2) 150ms duration, and (3) a blackbody rather than a simple power-law spectral shape (with a significance level of 97%). We found two possible X-ray counterparts of GRB 050925 by comparing the X-ray images from Swift XRT and XMM-Newton. Both X-ray sources show the transient behavior with a power-law decay index shallower than −1. We found no hard X-ray emission nor any additional burst from the location of GRB 050925 in ∼5ms of INTEGRAL data. We discuss about the three BATSE short bursts which might be associated with GRB 050925, based on their location and the duration. Assuming GRB 050925 is associated with the HII regions (W 58) at the galactic longitude of l =70°, we also discuss the source frame properties of GRB 050925. [Copyright &y& Elsevier]

Abstract: Monitor of All-sky X-ray Image (MAXI) is the unprecedentedly sensitive all-sky X-ray monitor. MAXI is mounted on the Exposed Facility of Japanese Experiment Module on the International Space Station. MAXI has two types of slit and slat X-ray cameras: Gas Slit Camera (GSC) and Solid-state Slit Camera (SSC) sensitive for 2–30 and 0.5–12keV bands, respectively. We calibrated the alignment of the GSC, then the position accuracy of X-ray point sources was significantly improved from about 1°to 0.2°(90% containment radius). This improvement of the position accuracy is essentially important to achieve various scientific objectives of MAXI. [ABSTRACT FROM AUTHOR]

Abstract: An ultra-luminous X-ray source, such as the one in M82, may very well be a signature of the presence of a black hole of intermediate mass. Such a black hole can be formed in a young and dense star cluster during the core collapse of the cluster, and subsequently capture a massive companion star. As the captured companion evolves it will overflow its Roche-lobe to start an episode of mass transfer. As long as the donor is still on the main-sequence, the mass transfer rate will be insufficient to power an ultra-luminous X-ray source, but as soon as it ascends the giant branch the X-ray luminosity increases by more than two orders of magnitude. Eventually, the companion to the intermediate mass black hole collapses to a black hole or a neutron star in a supernova explosion. In the latter case, the former X-ray source will become visible as a radio pulsar in orbit around an intermediate mass black hole. We predict that several of such sources will be detectable with the Low Frequency Array LOFAR. [ABSTRACT FROM AUTHOR]

Abstract: The origin of the extremely soft (low temperature) X-rays produced in the supersoft X-ray sources (or SSS) has been a subject of debate for much of the 25years since their discovery. The currently accepted paradigm is that they are Eddington-limited accreting white dwarfs in which the accreted material is undergoing steady nuclear burning, thereby achieving the high luminosities recorded from the brightest SSS in the Magellanic Clouds. Such a model requires an extremely high mass transfer rate from the donor, only achievable via thermally unstable mass transfer from a massive (>1M⊙) donor. An ideal SSS to probe this model in detail is the (only) recurrent, transient SSS, RX J0513.9-6951 which outbursts in X-rays every 100–150days for a month or so, but is accompanied by a substantial (∼1 mag) optical decline. Using XMM we have obtained simultaneous soft X-ray, UV and optical observations through such an event, showing that as the X-ray flux declines the temperature declines as well (moving the peak emission into the UV) whereas the optical flux and (implied) white dwarf radius increase. Such an expansion of the white dwarf is evidenced by highly ionised outflowing gas in the high resolution X-ray spectra. [ABSTRACT FROM AUTHOR]

Abstract: A formidable array of advanced laser systems are emerging that produce extreme states of light and matter. By irradiating solid and gaseous targets with lasers of increasing energy densities, new physical regimes of radiation effects are being explored for the first time in controlled laboratory settings. One result that is being accomplished or pursued using a variety of techniques, is the realization of novel sources of X-rays with unprecedented characteristics and light–matter interactions, the mechanisms of which are in many cases still being elucidated. Examples include the megajoule class of laser-produced plasmas designed in pursuit of alternative-energy and security applications and the petawatt class of lasers used for fast ignition and X-ray radiographic applications such as medical imaging and real-time imaging of plasma hydrodynamics. As these technologies mature, increased emphasis will need to be placed on advanced instrumentation and diagnostic metrology to characterize the spectra, time structure, and absolute brightness of X-rays emitted by these unconventional sources. Such customized and absolutely calibrated measurement tools will serve as an enabling technology that can help in assessing the overall system performance and progress, as well as identification of the underlying interaction mechanisms of interest to basic and applied strong-field and high-energy-density science. [Copyright &y& Elsevier]

Abstract: Assuming that soft X-ray sources in symbiotic stars result from strong thermonuclear runaways, and supersoft X-ray sources from weak thermonuclear runaways or steady hydrogen burning symbiotic stars, we investigate the Galactic soft and supersoft X-ray sources in symbiotic stars by means of population synthesis. The Galactic occurrence rates of soft X-ray sources and supersoft X-ray sources are from ∼2 to 20yr−1, and ∼2 to 17yr−1, respectively. The numbers of X-ray sources in symbiotic stars range from 2390 to 6120. We simulate the distribution of X-ray sources over orbital periods, masses and mass accretion rates of white dwarfs. The agreement with observations is reasonable. [Copyright &y& Elsevier]

Abstract: The EGRET observations have confirmed and proposed the new isotropically distributed γ-ray background, but the known objects radiating γ-rays can not supply so much radiation. Meanwhile, EGRET also reveals a population of γ-ray sources with no radio counterparts which are isotropically distributed in the sky, indicating their possible cosmological origins. Wang et al.[13] proposed a new γ-ray radiation process driven by the radiation feedback of AGNs. The energy of the radiation peaks around 1GeV—0.1TeV with the typical luminosity of 1042—1043 ergs · s−1. This kind of radiation process in the radio quiet quasars make them the potential γ-ray radiation sources as well as the contributors to the γ-ray background. We consider two cases in which the seed photons in the inverse-Compton processes are from the accretion disks of quasars and cosmic microwave background (CMB), respectively. We find that the former contributes 78%—92% of the background radiation around 1GeV, while the contribution from the latter is negligible. The radio quiet quasars are highly likely to become the objects which contribute the most energy to the γ-ray background around 1GeV. [Copyright &y& Elsevier]

Abstract: Recent observations with Chandra and XMM-Newton have shown that the X-ray source 1WGA J1346.5–6255 is associated with the Be star HD 119682, a member of the open cluster NGC 5281, and displays all the characteristics of the new class of X-ray sources known as -Cas analogues. We present a detailed spectroscopic study of this open cluster, finding an age of 40Myr and a sequence of evolved stars. These results imply that HD 119682 is a blue straggler in NGC 5281, as it is much more massive than any other cluster member, and its membership is strongly suggested by proper motion analysis. This is the second -Cas analogue found to be blue straggler in an open cluster, suggesting that evolution plays a role in the formation of these systems and that a supernova explosion has not occurred in them. [Copyright &y& Elsevier]

Abstract: Using Chandra X-ray, Spitzer mid-IR, and 1.5GHz radio data, we examine the spatial structure of SNR 3C 391. The X-ray surface brightness is generally anti-correlative with the IR and radio brightness. The multiband data clearly exhibit a heart-shaped morphology and show the multi-shell structure of the remnant. A previously unseen thin brace-like shell on the south detected at 24μm is projected outside the radio border and confines the southern faint X-ray emission. The leading 24μm knot on the SE boundary appears to be partly surrounded by soft X-ray emitting gas. The mid-IR emission is dominated by the contribution of the shocked dust grains, which may have been partly destroyed by sputtering. [Copyright &y& Elsevier]

Abstract: In the framework of the study of supernova remnants and their complex interaction with the interstellar medium and the circumstellar material, we focus on the galactic supernova remnant W49B. Its morphology exhibits an X-ray bright elongated nebula, terminated on its eastern end by a sharp perpendicular structure aligned with the radio shell. The X-ray spectrum of W49B is characterized by strong K emission lines from Si, S, Ar, Ca, and Fe. There is a variation of the temperature in the remnant with the highest temperature found in the eastern side and the lowest one in the western side. The analysis of the recent observations of W49B indicates that the remnant may be the result of an asymmetric bipolar explosion where the ejecta are collimated along a jet-like structure and the eastern jet is hotter and more Fe-rich than the western one. Another possible scenario associates the X-ray emission with a spherical explosion where parts of the ejecta are interacting with a dense belt of ambient material. To overcome this ambiguity we present new results of the analysis of an XMM-Newton observation and we perform estimates of the mass and energy of the remnant. We conclude that the scenario of an anisotropic jet-like explosion explains quite naturally our observation results, but the association of W49B with a hypernova and a γ-ray burst, although still possible, is not directly supported by any evidence. [Copyright &y& Elsevier]

Abstract: Astrosat will be the first full-fledged Indian Astronomy mission aimed at multiwavelength studies in the optical, near- and far-UV and a broad X-ray spectral band covering 0.5–100keV. This mission will have the capability of high time-resolution X-ray studies (10μs timing), low and medium energy-resolution spectral studies and high angular-resolution (about 2″) imaging observations in the UV and optical bands simultaneously. This is realized by using a set of three co-aligned X-ray astronomy instruments and one UV imaging telescope consisting of two similar instruments. Detection and timing studies of X-ray transients and persisting sources will be done by a Scanning Sky X-ray Monitor. This mission will enable studies of different classes of galactic and extragalactic sources in the frontier area of high energy astronomy. Scientific objectives of the mission are highlighted in this paper. A brief summary of the design and characteristics of the X-ray and UV instruments and their expected sensitivities are presented. [Copyright &y& Elsevier]

Abstract: Using the new generation of X-ray observatories, we are now beginning to identify populations of close binaries in globular clusters, previously elusive in the optical domain because of the high stellar density. These binaries are thought to be, at least in part, responsible for delaying the inevitable core collapse of globular clusters and their identification is therefore essential in understanding the evolution of globular clusters, as well as being valuable in the study of the binaries themselves. Here, we present observations made with XMM-Newton of six globular clusters, in which we have identified neutron star low mass X-ray binaries and their descendants (millisecond pulsars), cataclysmic variables and other types of binaries. We discuss not only the characteristics of these binaries, but also their formation and evolution in globular clusters and their use in tracing the dynamical history of these clusters. [Copyright &y& Elsevier]

Abstract: Grazing-incidence optics has revolutionized soft-X-ray astronomy yet the scientifically important hard-X-ray region has gone relatively unexplored at high sensitivity and fine angular scales. This situation is now changing with several flight-ready balloon-borne focusing telescopes and planned satellite-borne observatories. This review discusses some of the developments in mirror and focal plane technologies that are making these payloads possible. [Copyright &y& Elsevier]

Abstract: We present results on the X-ray source populations of nearby star-forming galaxies based on Chandra observations. First we discuss the monitoring campaigns on the Antennae and M82 galaxies. In both cases we find that the majority of the X-ray sources exhibit intensity and/or spectral variability. However, despite of this variability, we do not find any statistically significant variations of their X-ray luminosity functions (XLFs). We also find that the majority of the X-ray sources are associated with star-forming regions, although we do not always identify optical counterparts to the X-ray sources. Especially in the case of M82 we find that the most luminous sources are clustered in the central region of the galaxy. Finally, we present the first results from a study of a sample of nearby star-forming galaxies which form a starburst age sequence: although their XLFs to first order are represented by power-laws with consistent slopes, there is an indication for small variations, suggesting a change of their X-ray binary populations. [Copyright &y& Elsevier]

Abstract: With its ability to look at bright galactic X-ray sources with sub-millisecond time resolution, the Rossi X-ray Timing Explorer (RXTE) discovered that the X-ray emission from accreting compact stars shows quasi-periodic oscillations on the dynamical timescales of the strong field region. RXTE showed also that waveform fitting of the oscillations resulting from hot spots at the surface of rapidly rotating neutron stars constrain their masses and radii. These two breakthroughs suddenly opened up a new window on fundamental physics, by providing new insights on strong gravity and dense matter. Building upon the RXTE legacy, in the Cosmic Vision exercise, testing General Relativity in the strong field limit and constraining the equation of state of dense matter were recognized recently as key goals to be pursued in the ESA science program for the years 2015–2025. This in turn identified the need for a large (10m2 class) aperture X-ray observatory. In recognition of this need, the XEUS mission concept which has evolved into a single launch L2 formation flying mission will have a fast timing instrument in the focal plane. In this paper, I will outline the unique science that will be addressed with fast X-ray timing on XEUS. [Copyright &y& Elsevier]

Abstract: High-resolution Chandra observations have allowed the detection of populations of X-ray sources in galaxies of all morphological types. The X-ray Luminosity Functions (XLFs) of these X-ray source populations have been derived and studied to uncover the drivers for the formation and evolution of binaries in different stellar populations and environments. These XLFs also provide a tool for identifying the nature of the X-ray source population, since different XLFs characterize X-ray sources belonging to young and old stellar populations. Similarly, X-ray colors can be used for identifying different types of X-ray sources. Ultra-Luminous X-ray sources (ULXs, LX >1039 ergss−1) are found to be associated with star-forming stellar populations. The study of the ULX population of the Antennae galaxies points to compact accreting binaries. [Copyright &y& Elsevier]

Abstract: We interpret the rapid correlated UV/optical/X-ray variability of XTE J1118+480 as a signature of the coupling between the X-ray corona and a jet emitting synchrotron radiation in the optical band. We propose a scenario in which the jet and the X-ray corona are fed by the same energy reservoir where large amounts of accretion power are stored before being channelled into either the jet or the high energy radiation. This time-dependent model reproduces the main features of the rapid multi-wavelength variability of XTE J1118+480. A strong requirement of the model is that the total jet power should be at least a few times larger than the observed X-ray luminosity, implying a radiative efficiency for the jet ϵ j ≳3×10−3. This would be consistent with the overall low radiative efficiency of the source. We present independent arguments showing that the jet probably dominates the energetic output of all accreting black holes in the low-hard state. [Copyright &y& Elsevier]

Abstract: Our current theoretical and observational understandings of the accretion disks around Galactic black-holes are reviewed. Historically, a simple phenomenological accretion disk model has been used to interpret X-ray observations. Although such a phenomenological interpretation is still useful, high quality X-ray data from contemporary instruments allow us to test more realistic accretion disk models. In a simple and ideal case, the standard optically thick accretion disk model is successful to explain observations, such that the inner disk radius is constant at three times the Schwarzschild radius over large luminosity variations. However, when disk luminosity is close to or exceeds the Eddington luminosity, the standard disk model breaks, and we have to consider the “slim disk” solution in which radial energy advection is dominant. Recent observations of Ultra-luminous X-ray sources (ULXs), which may not be explained by the standard disk model, strongly suggest the slim disk solution. We compare theoretical X-ray spectra from the slim disk with observed X-ray spectra of ULXs. We have found that the slim disk model is successful to explain ULX spectra, in terms of the massive stellar black-holes with several tens of solar mass and the super-Eddington mass accretion rates. In order to explain the large luminosities (>1040 ergss−1) of ULXs, “intermediate black-holes” (>100M ⊙) are not required. Slim disks around massive stellar black-holes of up to several tens of solar mass would naturally explain the observed properties of ULXs. [Copyright &y& Elsevier]

Abstract: This paper presents an update of what we have learned in the last year about the ULX phenomenon. New results are presented on radio emission from Holmberg II and a review is given on the recent X-ray data on timing and spectra. The new X-ray spectroscopic and optical imaging survey of nearby ULX with XMM allows us, for the first time, to place the average properties of these objects on a statistical basis. Direct examination of the sites of ULXs in nearby galaxies shows that ∼1/3 of them are not in or near star forming regions, indicating that a substantial fraction of ULX are not directly associated with young star formation. There are two ULX which have been identified with B stars as the optical counterparts on the basis of optical spectroscopy. Radio imaging of the Holmberg II ULX shows that it lies in a luminous extended radio source and that the radio emission is not beamed. A statistical study of ULX spectra in nearby galaxies shows that the ratio of ‘high state’ to ‘low state’ ULXs is ∼1:1 and that the high state objects, in general, are best fit with low temperature black bodies with a steep power law index. The objects with high state spectra are systematically more luminous than the objects with low state spectra consistent with the hypothesis that both are drawn from a population which shows state changes similar to those of black holes in the Milky Way. If this is true then the masses implied for the objects with the low state spectra are greater than 50M ⊙. [Copyright &y& Elsevier]

Abstract: Outer radius variations play an important role in the disc structure and evolution. We consider theoretical and observational consequences of such variations in cataclysmic binaries and low-mass X-ray binaries. We find that the action of tidal torques must be important well inside the tidal radius. We also conclude that it is doubtful that the tidal–thermal instability is responsible for the superoutburst/superhump phenomena. [Copyright &y& Elsevier]

Abstract: The INTEGRAL satellite observed the binary black hole system Cygnus X-1 on 2003 June 7–11. The source was detected up to 800 keV, its spectrum beeing compatible with a power law of photon index 2.3. In the framework of the accreting black hole phenomenology, the source was in an unusual state, probably the so-called “intermediate state”. Using the results of the analysis performed on these INTEGRAL data, we present here the spectral properties of our observations over the whole energy range covered by the high-energy instruments on board INTEGRAL. We then compare them with those obtained from earlier observations of Cygnus X-1 performed during the INTEGRAL performance and verification phase in the fall of 2002. At that time, the source was found in the low/hard state, indicating that Cygnus X-1 underwent a transition towards a softer state in 2003 June. We discuss the spectral parameters obtained from a Comptonization model. [Copyright &y& Elsevier]

Abstract: We evaluate 0.03–20 Hz power spectra of the bright black hole binary Cyg X-1 obtained from non-deconvolved INTEGRAL-ISGRI event data. The ISGRI power spectra are compared to contemporary RXTE-PCA ones in the same hard X-ray energy band of 15–70 keV. They agree well in shape. Since the ISGRI power spectrum of Cyg X-1 is not background corrected it lies about an order of magnitude below the PCA values. In 2003 a soft outburst of Cyg X-1 occurred. From the RXTE-ASM and Ryle radio long term lightcurves and the RXTE spectra we see a canonical “hard state–intermediate state–soft state” evolution. We discuss the evolution of the power spectra in the 15–70 keV range which so far is much less well studied than that at softer energies. We interpret our results regarding the origin of certain variability components. [Copyright &y& Elsevier]

In this paper, we discuss the possible role of rotation in supernova blast energetics and morphology, and speculate on the origin of Cas A''s and SN1987A''s ejecta fields. Two “explosive” phenomena may be associated with most core collapses, the neutrino-driven supernova itself and an underenergetic jet-like ejection that follows. The latter may be a magnetic wind that easily penetrates the debris created by the much more energetic supernova. We speculate that many core-collapse supernova remnants should have sub-dominant jet-like features. In Cas A, we associate this sub-dominant collimated wind with the “jet/counter-jet” structure observed. We suggest that the actual Cas A explosion itself is at nearly right angles to this jet, along a rotation axis that coincides with the bulk of the ejecta, the iron lobes, and the putative direction of motion of the point source. It may be that when rotation becomes sufficiently rapid that the strong-neutrino-driven-supernova/weak-jet duality switches to a strong-MHD-jet scenario that might be associated with hypernovae, and in some cases GRBs. Finally, we present a calculation using a new 2D multi-group, flux-limited radiation/hydrodynamics code we have recently developed for the simulation of core-collapse supernovae. We discuss the rotation-induced anisotropy in the neutrino radiation field, neutrino heating, and the neutrino flux vectors and speculate on rotation''s possible role in the supernova mechanism. [Copyright &y& Elsevier]

Abstract: We study the possibility to probe the spatial geometry of the Universe by supernova measurement. We illustrate with an accelerating universe model with infinite-volume extra dimensions, for which the 1σ level supernova results indicate that the Universe is closed. [Copyright &y& Elsevier]

A new balloon-borne instrument is proposed which will allow the polarisation of gamma-rays in the energy range 30–200 keV to be measured. A diverse variety of astrophysical sources, such as Active Galactic Nuclei, pulsars and Galactic X-ray binaries are expected to emit polarised gamma-rays. Studies of their polarisation properties will provide a new and powerful probe of the geometry and physical conditions in these sources. [Copyright &y& Elsevier]

The study of the clumpy and irregular features in the X-ray emission of middle-aged supernova remnants shells allows us to shed light on the various characteristic of the interstellar medium, like its structure and composition. We have observed with XMM-Newton a small knot in the Vela SNR, which previous ROSAT studies have indicated as one of the best examples of an interaction between the SNR shock and an isolated cloud. We present preliminary results of this study. Thanks to the combination of good spectral and spatial resolution of the EPIC camera, we have realized maps of the X-ray emission in three different bands, pinpointing the contribution from different spatial regions. We have also studied the relation between the mean photon energy in a 10 arcsec/pixel image and the pixel count rate, arguing that at least two kinds of isobaric structures (a small isolated cloud and a larger feature) can be identified, both of which have interacted with a shock and both with their own thermal structure. [Copyright &y& Elsevier]

We use observable properties of Type IIP (core-collapse) supernovae to obtain improved insight into the type of star which explodes, the range of masses of radioactive material produced and its effect on other observable properties. Because, we now have a small sample of reasonably frequently observed Type IIP SNe, we have used the light curves to obtain the mass of 56Co produced, a method exploited for the well observed SN 1987A. With these determinatiots, we can demonstrate a correlation between the mass of 56Co and the rate of decline of the visible light curve (V) from plateau to exponential decay. This provides a distance-independent method for determining the mass of 56Co. The availability of spectra in the phase interval 200–400 days allows us to demonstrate a good correlation between the luminosity of Hα and the 56Co mass. More observed SNe with improved sampling would strengthen these conclusions. [Copyright &y& Elsevier]

Most cosmic rays are thought to be accelerated by the shocks of supernova explosions of very massive stars. Here, we review one quantitative proposal, which predicted the spectral slopes, bend and cutoff about the cosmic ray spectrum across the spectral bend or “knee” near 3×1015 eV in 1993. Many of the specific predictions have now been verified, and so it may be appropriate to investigate the consequences of that proposal. The successful fit to the cosmic ray data across the knee suggests: (1) very massive stars, above about 20–25 solar masses all converge to a common final state; (2) the supernova explosion of these very massive stars is caused by a combination of rotation, magnetic fields and the gravitational potential, just as proposed by Bisnovatyi-Kogan [Astron. Zh. (Sov. Astron.) 47 (1970) 813], based on an earlier suggestion by Kardashev [Astron. Zh. 41 (1964) 807]; (3) their stellar winds as well as the explosion provide the main injection of magnetic fields into the interstellar medium; (4) the explosive energy of these supernovae is about 1052 erg; (5) the explosion is extremely anisotropic, which may unify several classes of observed supernova types; (6) γ-ray bursts may be the ultimate version of such an explosion in the case the collapse leads to a black hole; and (7) it is plausible that the luminosity of the supernova integrated over all aspect angles is also the same for all these massive star explosions, leading to (8) a possibly very bright standard candle, if we could just find a correction for the extreme asphericity. This may solve the problem of what the mechanism of supernova explosions is for very massive stars, where most cosmic rays and magnetic fields come from, and may also point the way to a unifying scheme for supernova explosions and γ-ray bursts. [Copyright &y& Elsevier]

High energy emission from supernovae provide a direct window into the quantity and distribution of radioactive elements produced in these explosions. Combining supernova explosion calculations with 3D Monte Carlo γ-ray transport, I have studied the effect mixing and asymmetries have on the hard X-ray and γ-ray spectra. With sufficient spectral resolution, the emission line profiles from nickel decay have enough information to distinguish between spherical and mildly asymmetric supernova explosions. [Copyright &y& Elsevier]