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[en] Charge coupled devices (CCDs) optimized for soft X-ray detection were utilized for the Solid-state Imaging Spectrometers (SIS) onboard the ASCA satellite, and have been in operation since its launch in 1993. We have been carefully monitoring the change in performance of SIS due to radiation damage over three years since launch. Both an increase of dark current and a decrease of charge transfer efficiency are observed, as expected from experiments in the laboratory, but their characteristics are somewhat different from those predicted before launch. This is the first detailed analysis of radiation damage to CCDs actually operated in the space environment and gives important information for the development of similar detectors for space applications
[en] The performance of the charge coupled devices on-board the ASCA satellite has been traced for five years after the launch. We found the gradual increase of the dark current and the decrease of the charge transfer efficiency. These changes may be explained by charge traps due to the radiation damage. The nature of the radiation damage is investigated in detail using various methods
[en] The authors have discovered a new hard X-ray source near supernova 1987A, in the Large Magellanic Cloud, from the X-ray astronomy satellite Ginga. The present error box of 0.2 deg x 0.3 deg includes the supernova. The energy spectrum is very hard above 10 keV and unusual for any of the known classes of X-ray source. The flux in the range 10-30 keV as of 2-3 September is ∼ 5 x 10-11 erg cm-2 s-1. The source intensity increased steadily throughout July, August and early September, but an observation in late September revealed no further increase. The positional agreement, a steady brightening and an unusual hard spectrum support the identification of the source as SN1987A. (author)
[en] Extensive Ginga observations of PSR 0540 - 69, the Crab-like 50-msec pulsar in the LMC, have been obtained as a side benefit of a pulsar search project for SN 1987A. Through a coherent pulse-timing analysis of data from 46 separate days between July 1987 and October 1988, precise values have been obtained for the pulse frequency and its first and second derivatives. From these values, a braking index of n = 2.02 + or = 0.01 is obtained for PSR 0540 - 69. This is the first accurate measurement of a pulsar braking index from X-ray observations and the third overall. The braking index is much smaller than those previously determined for the Crab pulsar (n = 2.51) and PSR 1509 - 58 (n = 2.83). 24 refs
[en] During Ginga observations of the Rapid Burster in August 1988, strong quasi-periodic oscillations (QPOs) were detected in its X-ray intensity. The QPOs had centroid frequencies of 5 and 2 Hz during type II X-ray bursts which lasted for 10 and 30 s, respectively. The presence of the QPOs is correlated with the time scale-invariant burst profile. They are very strong during the initial peak in the burst, absent in the second peak, and strong again at the onset of the third peak. From an analysis of the X-ray spectrum as observed during the maxima and minima of the oscillations, it is found that the oscillations can be described by changes of the temperature of a blackbody emitter of constant apparent area. 47 refs
[en] We report on the hard X-ray response of the CCD detector for the X-ray imaging spectrometer (XIS), to be launched on the next Japanese X-ray Astronomical Satellite, ASTRO-E, in February 2000. XIS is prepared by an international team, comprised of MIT (USA), ISAS, Osaka University and Kyoto University (JAPAN). We have evaluated the X-ray response of the XIS in its high-energy band (1.5-10 keV). Data from the fluorescent line emission of Al, Cl, Ti, Ni, Fe, Zn, Se were used to construct the response function of the CCD detectors. Details of the response function - including the energy-scale, linearity, energy resolution, quantum efficiency -, are given as a function of incident X-ray energy. We find that the tail component of high-energy photopeaks are produced by events with incomplete charge collection. We also conclude that the size of the charge clouds can be estimated using the shapes of the tail components
[en] The nature and evolution of binary X-ray sources in globular clusters are poorly understood. Among the ∼10 bright X-ray sources in globular clusters, X2127+11 in M15 is very important because it is the only one for which the optical counterpart, AC211, and orbital period, 8.5 h, are both known. We have detected a type I X-ray burst from X2127+11, which was the only bright X-ray source in a globular cluster form which no burst had been detected. The burst was of long duration (≅ 150 s) and had a precursor separated from the main peak by ∼ 6 s. This means that the burst was very energetic and that a large photospheric expansion occurred. The observed burst peak luminosity, well above 1038 erg s-1, is hard to reconcile with the standard idea that X2127+11 is screened from direct view by an accretion disk. This latter view arises from consideration of the low ratio of X-ray to optical luminosity, which suggests that only a small fraction of X-rays is visible through scattering by an accretion-disk corona around the source. (author)
[en] This school, dedicated to young researchers, will clarify our present knowledge of the X-ray sky and give the opportunity to learn about the observatories and tools which are available. The contributions have been organized into 3 issues: -) fundamental physics, -) X-ray and Gamma-ray instruments and analysis techniques, and -) astrophysical objects. This document gathers only the slides of the presentations
[en] We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10 keV) properties for local active galactic nuclei (AGNs). The Swift Burst Alert Telescope all-sky survey provides an unbiased, flux-limited selection of hard X-ray-detected AGNs. Cross-correlating the 22 month hard X-ray survey with the AKARI all-sky survey, we studied 158 AGNs detected by the AKARI instruments. We find a strong correlation for most AGNs between the infrared (9, 18, and 90 μm) and hard X-ray (14-195 keV) luminosities, and quantify the correlation for various subsamples of AGNs. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution. The correlation for radio galaxies has a slope and normalization identical to that for Seyfert 1 galaxies, implying similar hard X-ray/infrared emission processes in both. In contrast, Compton-thick (CT) sources show a large deficit in the hard X-ray band, because high gas column densities diminish even their hard X-ray luminosities. We propose two photometric diagnostics for source classification: one is an X-ray luminosity versus infrared color diagram, in which type 1 radio-loud AGNs are well isolated from the others in the sample. The other uses the X-ray versus infrared color as a useful redshift-independent indicator for identifying CT AGNs. Importantly, CT AGNs and starburst galaxies in composite systems can also be differentiated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new and upcoming surveys such as WISE and NuSTAR.
[en] The wide-band Suzaku spectra of the black hole (BH) binary GX 339-4, acquired in 2007 February during the Very High state, were reanalyzed. Effects of event pileup (significant within ∼3' of the image center) and telemetry saturation of the X-ray Imaging Spectrometer (XIS) data were carefully considered. The source was detected up to ∼300 keV, with an unabsorbed 0.5-200 keV luminosity of 3.8 x 1038 erg s-1 at 8 kpc. The spectrum can be approximated by a power law of photon index 2.7, with a mild soft excess and a hard X-ray hump. When using the XIS data outside 2' of the image center, the Fe K line appeared extremely broad, suggesting a high BH spin as already reported by Miller et al. based on the same Suzaku data and other CCD data. When the XIS data accumulation is further limited to >3' to avoid event pileup, the Fe K profile becomes narrower, and a marginally better solution appears which suggests that the inner disk radius is 5-14 times the gravitational radius (1σ), though a maximally spinning BH is still allowed by the data at the 90% confidence level. Consistently, the optically thick accretion disk is inferred to be truncated at a radius 5-32 times the gravitational radius. Thus, the Suzaku data allow an alternative explanation without invoking a rapidly spinning BH. This inference is further supported by the disk radius measured previously in the High/Soft state.