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We present the spectral and scattering theory of the Casimir operator acting on the radial part of SL(2,R). After a suitable decomposition, these investigations consist in studying a family of differential operators acting on the half-line. For these operators, explicit expressions can be found for the resolvent, for the spectral density, and for the Moeller wave operators, in terms of the Gauss hypergeometric function. An index theorem is also introduced and discussed. The resulting equality links various asymptotic behaviors of the hypergeometric function., Comment: 27 pages

The two-dimensional layered compound PdCoO$_2$ is one of the best oxide conductors, providing an intriguing research arena opened by the long mean free path and the very high mobility of ~51000 cm2/Vs. These properties turn PdCoO$_2$ into a candidate material for nanoscale quantum devices. By exploring universal conductance fluctuations originating at nanoscale PdCoO$_2$ Hall-bar devices, we determined the phase coherence length of electron transport in c-axis oriented PdCoO$_2$ thin films to equal ~100 nm. The weak temperature dependence of the measured phase coherence length suggests that defect scattering at twin boundaries in the PdCoO$_2$ thin film governs phase breaking. These results suggest that phase coherent devices can be achieved by realizing the devices smaller than the size of twin domains, via refined microfabrication and suppression of twin boundaries., Comment: 6 pages, 5 figures

In this review paper we carry on our investigations on Schroedinger operators with inverse square potentials on the half-line. Depending on several parameters, such operators possess either a finite number of complex eigenvalues, or an infinite one, but also some spectral singularities embedded in the continuous spectrum (exceptional situations). The spectral and the scattering theory for these operators is recalled, and new results for the exceptional cases are provided. Some index theorems in scattering theory are also developed, and explanations why these results can not be extended to the exceptional cases are provided., Comment: 24 pages

Based on operators borrowed from scattering theory, several concrete realizations of index theorems are proposed. The corresponding operators belong to some C*-algebras of pseudo-differential operators with coefficients which either have limits at plus and minus infinity, or which are periodic or asymptotically periodic, or which are uniformly almost periodic. These various situations can be deduced from a single partial isometry which depends on several parameters. All computations are explicitly performed., Comment: 20 pages

In this paper we introduce a general theory of regular biorthogonal sequences and its physical applications. Biorthogonal sequences $\{ \phi_{n} \}$ and $\{ \psi_{n} \}$ in a Hilbert space ${\cal H}$ are said to be regular if $Span\; \{ \phi_{n} \}$ and $Span\; \{ \psi_{n} \}$ are dense in ${\cal H}$. The first purpose is to show that there exists a non-singular positive self-adjoint operator $T_{\mbox{$f$}}$ in ${\cal H}$ defined by an ONB $\mbox{$f$} \equiv \{ f_{n} \}$ in ${\cal H}$ such that $\phi_{n}=T_{\mbox{$f$}} f_{n}$ and $\psi_{n}= T_{\mbox{$f$}}^{-1} f_{n}$, $n=0,1, \cdots$, and such an ONB $\mbox{$f$}$ is unique. The second purpose is to define and study the lowering operators $A_{\mbox{$f$}}$ and $B_{\mbox{$f$}}^{\dagger}$, the raising operators $B_{\mbox{$f$}}$ and $A_{\mbox{$f$}}^{\dagger}$, the number operators $N_{\mbox{$f$}}$ and $N_{\mbox{$f$}}^{\dagger}$ determined by the non-singular positive self-adjoint operator $T_{\mbox{$f$}}$. These operators connect with ${\it quasi}$-${\it hermitian \; quantum \; mechanics}$ and its relatives. This paper clarifies and simplifies the mathematical structure of this framework minimized the required assumptions., Comment: 23 pages

We report measurements of the gate-bias dependent band alignment, especially the confining potential profile, at the conducting LaAlO3/SrTiO3 (001) heterointerface using soft and hard x-ray photoemission spectroscopy. Depth-profiling analysis reveals that a significant potential drop on the SrTiO3 side of the interface occurs within ~2 nm of the interface under negative gate bias voltage. These results demonstrate gate control of the collapse of permittivity at the interface, and explain the dramatic loss of electron mobility with back-gate depletion., Comment: 16 pages, 4 figures

$^{63/65}$Cu- and $^{35/37}$Cl-NMR experiments were performed to investigate triplet localization in the $S=1/2$ dimer compound NH$_4$CuCl$_3$, which shows magnetization plateaus at one-quarter and three-quarters of the saturation magnetization. In $^{63/65}$Cu-NMR experiments, signal from only the singlet Cu site was observed, because that from the triplet Cu site was invisible due to the strong spin fluctuation of onsite 3$d$-spins. We found that the temperature dependence of the shift of $^{63/65}$Cu-NMR spectra at the singlet Cu site deviated from that of macroscopic magnetization below T=6 K. This deviation is interpreted as the triplet localization in this system. From the $^{35/37}$Cl-NMR experiments at the 1/4-plateau phase, we found the two different temperature dependences of Cl-shift, namely the temperature dependence of one deviates below T=6 K from that of the macroscopic magnetization as observed in the $^{63/65}$Cu-NMR experiments, whereas the other corresponds well with that of the macroscopic magnetization in the entire experimental temperature region. We interpreted these dependences as reflecting the transferred hyperfine field at the Cl site located at a singlet site and at a triplet site, respectively. This result also indicates that the triplets are localized at low temperatures. $^{63/65}$Cu-NMR experiments performed at high magnetic fields between the one-quarter and three-quarters magnetization plateaus have revealed that the two differently oriented dimers in the unit cell are equally occupied by triplets, the fact of which limits the theoretical model on the periodic structure of the localized triplets., Comment: 19 pages, 9 figures, submitted to PRB (in press)

We report results from a Suzaku observation of the narrow-line Seyfert 1 NGC 4051. During our observation, large amplitude rapid variability is seen and the averaged 2--10 keV flux is 8.1x10^-12 erg s^-1 cm^-2, which is several times lower than the historical average. The X-ray spectrum hardens when the source flux becomes lower, confirming the trend of spectral variability known for many Seyfert 1 galaxies. The broad-band averaged spectrum and spectra in high and low flux intervals are analyzed. The spectra are first fitted with a model consisting of a power-law component, a reflection continuum originating in cold matter, a blackbody component, two zones of ionized absorber, and several Gaussian emission lines. The amount of reflection is rather large (R ~ 7, where R=1 corresponds to reflection by an infinite slab), while the equivalent width of the Fe-K line at 6.4 keV is modest (140 eV) for the averaged spectrum. We then model the overall spectra by introducing partial covering for the power-law component and reflection continuum independently. The column density for the former is 1x10^23 cm^-2, while it is fixed at 1x10^24 cm-2 for the latter. By comparing the spectra in different flux states, we identify the causes of spectral variability. (abridged), Comment: 19 pages, 18 figures, accepted for publication in PASJ (Suzaku 3rd special issue)

The vortex state in a single crystal of the layered organic superconductor \kappa-(BEDT-TTF2Cu(NCS)2, where BEDT-TTF (or ET) is bis(ethylenedithio)tetrathiafulvalene, was studied by 1H-NMR. Under a low field region around 0.75 T, the vortex glass-liquid transition was demonstrated by a diverging of the longitudinal nuclear spin relaxation rate and peak-broadening in spectra. Under a high field region near the upper critical field Hc2(0)~7 T, the curvature of nuclear spin relaxation curves showed a drastic change at the temperature where the emergence of the quantum vortex slush state was reported. The mechanism in this curvature change was discussed in terms of the fluctuating field produced by fragments of vortex glass., Comment: 5 pages, 4 figures

The Hard X-ray Detector (HXD) on board Suzaku covers a wide energy range from 10 keV to 600 keV by combination of silicon PIN diodes and GSO scintillators. The HXD is designed to achieve an extremely low in-orbit back ground based on a combination of new techniques, including the concept of well-type active shield counter. With an effective area of 142 cm^2 at 20 keV and 273 cm2 at 150 keV, the background level at the sea level reached ~1x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 30 keV for the PI N diodes, and ~2x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 100 keV, and ~7x10^{-6} cts s^{-1} cm^{-2} keV^{-1} at 200 keV for the phoswich counter. Tight active shielding of the HXD results in a large array of guard counters surrounding the main detector parts. These anti-coincidence counters, made of ~4 cm thick BGO crystals, have a large effective area for sub-MeV to MeV gamma-rays. They work as an excellent gamma-ray burst monitor with limited angular resolution (~5 degree). The on-board signal-processing system and the data transmitted to the ground are also described., Comment: 35 pages, 25 figures and 4 tables; acceted for Publication of the Astronomical Society of Japan

Cu-NMR study has been performed on the disordered spin-gap system Tl1-xKxCuCl3 In the high-field H > HC=\Delta/\mu_B, where \Delta is the spin-gap, the hyperfine field becomes extremely inhomogeneous at low temperatures due to the field-induced magnetic order, indicating that the ordered spin state must be different from the pure TlCuCl3. In the low field H < HC, a saturating behavior in the longitudinal nuclear spin relaxation rate 1/T1 was observed at low temperatures, indicating existence of the magnetic ground state proposed to be Bose-glass phase by Fisher., Comment: RHMF2006

We have developed a framework for the Monte-Carlo simulation of the X-Ray Telescopes (XRT) and the X-ray Imaging Spectrometers (XIS) onboard Suzaku, mainly for the scientific analysis of spatially and spectroscopically complex celestial sources. A photon-by-photon instrumental simulator is built on the ANL platform, which has been successfully used in ASCA data analysis. The simulator has a modular structure, in which the XRT simulation is based on a ray-tracing library, while the XIS simulation utilizes a spectral "Redistribution Matrix File" (RMF), generated separately by other tools. Instrumental characteristics and calibration results, e.g., XRT geometry, reflectivity, mutual alignments, thermal shield transmission, build-up of the contamination on the XIS optical blocking filters (OBF), are incorporated as completely as possible. Most of this information is available in the form of the FITS (Flexible Image Transport System) files in the standard calibration database (CALDB). This simulator can also be utilized to generate an "Ancillary Response File" (ARF), which describes the XRT response and the amount of OBF contamination. The ARF is dependent on the spatial distribution of the celestial target and the photon accumulation region on the detector, as well as observing conditions such as the observation date and satellite attitude. We describe principles of the simulator and the ARF generator, and demonstrate their performance in comparison with in-flight data., Comment: 19 pages with 8 figures, accepted for publication in PASJ Vol 58, Suzaku special issue

We have developed a large CdTe pixel detector with dimensions of 23.7 x 13.0 mm and a pixel size of 448 x 448 um^2. The detector is based on recent technologies of an uniform CdTe single crystal, a two-dimensional ASIC, and stud bump-bonding to connect pixel electrodes on the CdTe surface to the ASIC. Good spectra are obtained from 1051 pixels out of total 1056 pixels. When we operate the detector at -50 C, the energy resolution is 0.67 keV and 0.99 keV at 14 keV and 60 keV, respectively. Week-long stability of the detector is confirmed at operating temperatures of both -50 C and -20 C. The detector also shows high uniformity: the peak positions for all pixels agree to within 0.82%, and the average of the energy resolution is 1.04 keV at a temperature of -50 C. When we normalized the peak area by the total counts detected by each pixel, a variation of 2.1 % is obtained., Comment: 11pages, 17figures, accepted for publication in Proc. SPIE 2004

We present the results from a multiwavelength campaign of GRS 1915+105 performed from 2000 April 16 to 25. This is one of the largest coordinated set of observations ever performed for this source, covering the wide energy band in radio (13.3-0.3 cm), near-infrared (J-H-K), X-rays and Gamma-rays (from 1 keV to 10 MeV). During the campaign GRS 1915+105 was predominantly in the "plateau" (or low/hard) state but sometimes showed soft X-ray oscillations: before April 20.3, rapid, quasi-periodic (~= 45 min) flare-dip cycles were observed. The radio flares observed on April 17 shows frequency- dependent peak delay, consistent with an expansion of synchrotron-emitting region starting at the transition from the hard-dip to the soft-flare states in X-rays. On the other hand, infrared flares on April 20 appear to follow (or precede) the beginning of X-ray oscillations with an inconstant time delay of ~= 5-30 min. This implies that the infrared emitting region is located far from the black hole by >~ 10E13 cm, while its size is <~ 10E12 cm constrained from the time variability. We find a good correlation between the quasi-steady flux level in the near-infrared band and in the X-ray band. From this we estimate that the reprocessing of X-rays, probably occurring in the outer parts of the accretion disk, accounts for about 20-30% of the observed K magnitude in the plateau state. The OSSE spectrum in the 0.05-10 MeV band is represented by a single power law with a photon index of 3.1 extending to ~1 MeV with no cutoff. The power-law slope above ~30 keV is found to be very similar between different states in spite of large flux variations in soft X-rays, implying that the electron energy distribution is not affected by the change of the state in the accretion disk., Comment: 31 pages, 11 figures. Accepted for publication in ApJ, vol. 571, 2002. Minor corrections. Figure 2 is revised (numbers on the top axis are corrected). References are updated

We study the structure and emission of the SS 433 jets in the X-ray emitting region and in the inner and hotter portion inside the X-ray emitting region. In order to consider the jet structure from the inner to outer regions we develop the hybrid model combining the conical beam and the model beam whose cross section grows with the distance more slowly. We find that the jet beams in the inner and hotter portion are of two-temperature and emit a large amount of high energy gamma photons. Our analyses suggest the thick absorbing envelope to exist in the SS 433 system. Based on our results, we discuss the possible acceleration mechanism for the SS 433 jets., Comment: 15 pages. Accepted for publication by Publ. Astron. Soc. Japan

We report on multi-epoch X-ray observations of the Type IIn (narrow emission line) supernova SN 1995N with the ROSAT and ASCA satellites. The January 1998 ASCA X-ray spectrum is well fitted by a thermal bremsstrahlung (kT~10 keV, N_H~6e20 cm^-2) or power-law (alpha~1.7, N_H~1e21 cm^-2) model. The X-ray light curve shows evidence for significant flux evolution between August 1996 and January 1998: the count rate from the source decreased by 30% between our August 1996 and August 1997 ROSAT observations, and the X-ray luminosity most likely increased by a factor of ~2 between our August 1997 ROSAT and January 1998 ASCA observations, although evolution of the spectral shape over this interval is not ruled out. The high X-ray luminosity, L_X~1e41 erg/sec, places SN 1995N in a small group of Type IIn supernovae with strong circumstellar interaction, and the evolving X-ray luminosity suggests that the circumstellar medium is distributed inhomogeneously., Comment: MNRAS accepted. 6 pages, 2 figures; uses mn.sty and psfig

The JAERI/KEK Joint Project for the high-intensity proton accelerator facility has been proposed with a superconducting (SC) linac option from 400 MeV to 600MeV. System design of the SC linac has been carried out based on the equipartitioning concept. The SC linac is planned to use as an injector to a 3GeV rapid cycling synchrotron (RCS) for spallation neutron source after it meets requirement to momentum spread less than +-0.1%. In the R&D work for SC cavities, vertical tests of single-cell and 5 cell cavities were performed. Experiments on multi-cell (5 cell) cavities of b=0.50 and b=0.89 at 2K were carried out with values of maximum electric surface peak fields of 23MV/m and 31MV/m, respectively. A model describing dynamic Lorentz detuning for SC cavities has been developed for pulse mode operation. Validity of the model was confirmed experimentally to simulate the performance., Comment: LINAC2000 conference, TUD09, 3 pages, 5 figures

We report the detection of an absorbed central X-ray source and its strong, rapid variability in NGC4395, the least luminous Seyfert nucleus known. The X-ray source exhibits a number of flares with factors of 3-4 flux changes during a half day ASCA observation. Such X-ray variability is in constrast to the behaviour of other low luminosity active galaxies. It provides further support for an accreting black hole model rather than an extreme stellar process in accounting for the nuclear activity of NGC4395. The soft X-ray emission below 3 keV is strongly attenuated by absorption. The energy spectrum in this absorption band shows a dramatic change in response to the variation in continuum luminosity. A variable warm absorber appears to be an explanation for the spectral change. The absorption-corrected 2-10 keV luminosity is 4e39 erg/s for a source distance of 2.6 Mpc, and at 1 keV is one order of magnitude above previous ROSAT estimates. Our X-ray results infer the nuclear source of NGC4395 to be a scaled-down version of higher luminosity Seyfert nuclei, with an intermediate mass (10^4-10^5 Msun) black hole, unlike the nearby low luminosity active galaxies in which underfed massive black holes are suspected to reside., Comment: 12 pages, accepted for publication in MNRAS

We report results on the broad iron emission line of the Seyfert galaxy MCG-6-30-15, obtained from the second long ASCA observation in 1997. The time-averaged profile of the broad line is very similar to that seen with ASCA in 1994, so confirming the detailed model fit then obtained. A bright flare is seen in the light curve, during which the continuum was soft. At that time the emission line peaks around 5 keV and most of its emission is shifted below 6 keV with no component detected at 6.4 keV (EW<60 eV). This can be interpreted as the result of an extraordinarily large gravitational redshift due to a dominant flare occurring very close to the black hole at a radius of <5m., Comment: 5 pages, accepted or publication in MNRAS Letters

We carried out the first wide-area unbiased survey with the ASCA satellite in the 0.7-10 keV band around a north Galactic-pole region covering a continuous area of 7 square degrees (Large Sky Survey; LSS). To make the best use of ASCA capability, we developed a new source-detection method where the complicated detector responses are fully taken into account. Applying this method to the entire LSS data independently in the total (0.7-7 keV), hard (2-10 keV), and soft (0.7-2 keV) band, we detected 107 sources altogether with sensitivity limits of 6 x 10E-14 (0.7-7 keV), 1 x 10E-13 (2-10 keV), and 2 x 10E-14 erg sE-1 cmE-2 (0.7-2 keV), respectively. A complete list of the detected sources is presented. Based on detailed studies by Monte Carlo simulations, we evaluated effects of the source confusion and accurately derived Log N - Log S relation in each survey band. The Log N - Log S relation in the hard band is located on the extrapolation from the GINGA and HEAO1 results with the Euclidean slope of -3/2, while that in the soft band is consistent with the results by ROSAT. At these flux limits, 30 (+/- 3) percent of the CXB in the 0.7-7 keV band and 23 (+/- 3) percent in the 2-10 keV band have been resolved into discrete sources. The average spectrum of faint sources detected in the total band shows a photon index of 1.63 +/- 0.07 in the 0.7-10 keV range, consistent with the comparison of source counts between the hard and the soft energy band. Those detected in the hard band show a photon index of 1.49 +/- 0.10 in the 2-10 keV range. These spectral properties suggest that contribution of sources with hard energy spectra become significant at a flux of 10E-13 erg sE-1 cmE-2 (2-10 keV). The most plausible candidates are type-II AGNs, as indicated by on-going optical identifications., Comment: 28 pages, 11 figures, to appear in ApJ 518, 1999; figure 1 replaced, minor errors in text corrected

We report the ASCA results of the bursting X-ray pulsar \gro, which was observed in February 1996 and March 1997. The source flux in the 2--10 keV band was $2.0\times10^{-8}$ erg/sec/cm$^2$ in 1996 and $5.0\times10^{-9}$ erg/sec/cm$^2$ in 1997. We detected 12 and 17 Type II bursts during the two observations with mean bursting intervals of about 27 min and 37 min. Each burst is followed by an intensity dip with the depleted flux depending on the burst fluence. The energy spectra are approximated by an absorbed power law with additional structure around 6--7 keV\@. Constant absorption column, $(5-6)\times10^{22}$ cm$^{-2}$, independent of the observation dates and emission phases (persistent, burst and dip) is interpreted as an interstellar absorption. The source may be actually located near the Galactic center, at a distance of 8.5 kpc. The structure in the energy spectrum at 6--7 keV is most probably due to iron and maybe reproduced by a disk line model with additional broadening mechanism., Comment: 28 pages 11 figures. ApJ accepted

We observed the newly discovered Galactic jet source XTE J0421+560 (= CI Cam) with ASCA from 1998 April 3.3 to April 4.1 (UT), three days after the beginning of the outburst. The X-ray intensity in the 1-10 keV band gradually decreased with an e-folding time of about 30 hours; the decline was accompanied by spectral softening. Two flare-like intensity enhancements were detected below 1 keV. We could fit the average spectrum above 0.8 keV with a two-temperature model (5.7 and 1.1 keV) of thermal emission from an optically thin ionization-equilibrium plasma. The broad iron-K profile, however, requires an extra emission line at 6.4 keV, or Doppler broadening (or both). The former can be explained in terms of reflection from cold matter, while the latter can be attributed to emission from the twin jets. In both cases, the time evolution of the emission measure and of the temperature are difficult to explain by emission from a single plasma, suggesting that heat input and/or injection of material was occurring during the outburst., Comment: 7 pages, 3 figures. Accepted for publication in ApJL; Fig. 1 corrected

We report results of analysis of the ASCA observation of the Low Mass X-ray Binary dipping source XB1916-053 made on 1993, May 2nd. We have shown that the spectra can be well fitted by the same two-component model previously used to give good explanations of the very different dip sources X1755-338 and X1624-490, consisting of point-source blackbody emission from the neutron star plus extended Comptonised emission from the accretion disk corona. In XB1916-053, all levels of dipping can be fitted using kT_bb= 2.14+/-0.28 keV and power law photon index = 2.42 +/-0.21. Dipping is shown to be due to large increases of column density for the point-like blackbody, combined with the extended power law component being progressively covered by absorber until in the deepest parts of dips, the partial covering fraction approaches unity. This approach differs radically from the ``absorbed plus unabsorbed'' approach previously used in spectral modelling of XB1916-053 and similar sources, in which the normalisation of the unabsorbed component is allowed to decrease markedly in dipping, behavior generally attributed to the effects of electron scattering. Thus we have shown that spectral evolution in XB1916-053 can be explained simply in terms of photoelectric absorption without the need for substantial electron scattering. This explanation is supported by calculation of the relative importance of photoelectric absorption and electron scattering in the absorbing region which shows that little electron scattering is expected in the ASCA energy band., Comment: 9 pages, Latex, 5 eps figures

We present Ginga measurements of the spatial fluctuations in the diffuse X-ray background. When combined with earlier results, the new data constrain the extragalactic log N - log S relation in the 2-10 keV energy band to a form close to the Euclidean prediction over the flux range 1E-10 - 5E-13 erg/cm2/s. The normalisation of the 2-10 keV source counts is a factor 2-3 above that derived in the softer 0.3-3.5 keV band from the Einstein Extended Medium Sensitivity Survey if a spectral conversion is assumed which ignores X-ray absorption intrinsic to the sources. Both this result and the spectral characteristics of the spatial fluctuations are consistent with relatively low-luminosity active galaxies (i.e. L_X < 1E44 erg/s) dominating the 2-10 keV source counts at intermediate flux levels. We also use the `excess variance' of the fluctuations to constrain possible clustering of the underlying discrete sources., Comment: 16 pages, LateX and 9 jpeg figures. Accepted in MNRAS. Also at http://www.ifca.unican.es/~barcons/preprints.html

We report the discovery of the cessation of flickering in dips in the black hole candidate Cygnus X-1, detected for the first time in the ASCA observation of May 9th., 1995. During this observation, particularly deep dipping took place resulting in strong changes in hardness ratio corresponding to absorption of the power law spectral component. The deadtime corrected light curve with high time resolution clearly shows a dramatic decrease in the extent of flickering in the band 0.7 - 4.0 keV during dipping, but in the band 4.0 - 10.0 keV, there is relatively little change. We show that the rms flickering amplitude in the band 0.7 - 4.0 keV is proportional to the X-ray intensity in this band which changes by a factor of almost three. This is direct evidence that the strong Low State flickering is intrinsic to the power law emission; ie takes place as part of the emission process. The rms amplitude is proportional to the intensity in the low energy band, except for a possible deviation from linearity at the lower intensities. If confirmed, this non-linearity could imply a process such as electron scattering of radiation which will tend to smear out the fluctuations, or a process of fluctuation generation which depends on radial position in the source. Thus timing observations during absorption dips can give information about the source region and may place constraints on its size., Comment: 6 pages including 4 figures, accepted for publication in Astrophysical Journal Letters

We report the results from an ASCA X-ray observation of the powerful Broad Line Radio Galaxy, 3C109. The ASCA spectra confirm our earlier ROSAT detection of intrinsic X-ray absorption associated with the source. The absorbing material obscures a central engine of quasar-like luminosity. The luminosity is variable, having dropped by a factor of two since the ROSAT observations 4 years before. The ASCA data also provide evidence for a broad iron emission line from the source, with an intrinsic FWHM of ~ 120,000 km/s. Interpreting the line as fluorescent emission from the inner parts of an accretion disk, we can constrain the inclination of the disk to be $> 35$ degree, and the inner radius of the disk to be $< 70$ Schwarzschild radii. Our results support unified schemes for active galaxies, and demonstrate a remarkable similarity between the X-ray properties of this powerful radio source, and those of lower luminosity, Seyfert 1 galaxies., Comment: MNRAS in press. 7 pages, 5 figures in MNRAS LaTex style

The X-ray/radio transient superluminal jet source GRO J1655-40 was recently suggested to contain a black hole from optical observations. Being a relatively close-by system (d \sim 3.2 kpc), it can likely provide us with rich information about the physics operating in both galactic and extragalactic jet sources. We present the first simultaneous broad band high energy observations of GRO J1655-40 during the 1995 July-August outburst by three instruments: ASCA, WATCH/GRANAT and BATSE/CGRO, in the energy band from 1 keV to 2 MeV. Our observations strengthen the interpretation that GRO J1655-40 contains a black hole. We detected a two-component energy spectrum, commonly seen from other galactic black hole binaries, but never detected from a neutron star system. Combining our results with the mass limits derived from optical radial velocity and orbital period measurements, we further constrain the mass of the central object to be between 3.3 and 5.8 M$_{\sun}$, above the well-established mass upper limit of 3.2 M$_{\sun}$ for a neutron star (the optical mass function for GRO J1655-40 is 3.16$\pm$0.2 M$_{\sun}$). This system is therefore the first galactic superluminal jet source for which there is strong evidence that the system contains a stellar mass black hole. The inclination angle of the binary system is constrained to be between 76 and 87 degrees, consistent with estimates obtained from optical light curves and radio jet kinematics., Comment: 27 pages, 4 PostScript figures, Accepted for ApJ publication

We shall discuss various kinds of geometric bremsstrahlung processes in the spatially flat Robertson-Walker universe. Despite that the temperature of the universe is much higher than particle masses and the Hubble parameter, the transition probability of these processes do not vanish. It is also pointed out that explicit forms of the probability possess a new duality with respect to scale factor of background geometry., Comment: 27 pages, LATEX file

We report on ASCA energy spectra of Cir X-1 taken near its zero phase on 1994 August 4-5. The ASCA SIS detectors allow a more detailed study of the iron K complex than has been possible before. We find that prior to a sudden upward flux transition the dominant iron K feature appears to consist of a large edge from neutral or nearly-neutral iron. The depth of the edge corresponds to an absorption column of about 1.5E24 cm^{-2}, while little absorption over that expected from the Galaxy is seen at lower X-ray energies. The differential absorption at high and low X-ray energies combined with the iron edge energy are strong evidence that partial covering is a crucial determinant of the behaviour observed from Cir X-1. The continuum spectral variability observed by ASCA can also be understood naturally in terms of partial covering column changes. There is evidence for a relatively weak emission line from neutral iron with an equivalent width of only about 65 eV. After the flux transition, the strength of the edge feature is greatly reduced, suggesting a large reduction in the amount of partial covering. For a large region of statistically acceptable chi-squared parameter space, the luminosity of Cir X-1, after correction for partial covering, need not change during the transition. We discuss models for the partial covering and suggest that X-ray scattering by electrons may be important. Aspects of the Cir X-1 spectrum are very similar to those of Seyfert 2 galaxies with Compton-thin tori., Comment: 14 pages, uuencoded compressed tar file, MNRAS

We report on the variability of the iron K emission line in the Seyfert 1 galaxy MCG--6-30-15 during a four-day ASCA observation. The line consists of a narrow core at an energy of about 6.4 keV, and a broad red wing extending to below 5 keV, which are interpreted as line emission arising from the inner parts of an accretion disk. The narrow core correlates well with the continuum flux whereas the broad wing weakly anti-correlates. When the source is brightest, the line is dominated by the narrow core, whilst during a deep minimum, the narrow core is very weak and a huge red tail appears. However, at other times when the continuum shows rather rapid changes, the broad wing is more variable than the narrow core, and shows evidence for correlated changes contrary to its long time scale behaviour. The peculiar line profile during the deep minimum spectrum suggests that the line emitting region is very close to a central spinning (Kerr) black hole where enormous gravitational effects operate., Comment: 13 pages, 13 ps figures, uses mn.sty (included) Accepted for publication in MNRAS

We present the results of a 4 day ASCA observation of the Seyfert galaxy MCG-6-30-15, focussing on the nature of the X-ray absorption by the warm absorber, characterizd by the K-edges of the intermediately ionized oxygen, OVII and OVIII. We confirm that the column density of OVIII changes on a timescale of $\sim 10^4$~s when the X-ray continuum flux decreases. The significant anti-correlation of column density with continuum flux gives direct evidence that the warm absorber is photoionized by the X-ray continuum. From the timescale of the variation of the OVIII column density, we estimate that it originates from gas within a radius of about $10^{17}\cm$ of the central engine. In contrast, the depth of the OVII edge shows no response to the continuum flux, which indicates that it originates in gas at larger radii. Our results strongly suggest that there are two warm absorbing regions; one located near or within the Broad Line Region, the other associated with the outer molecular torus, scattering medium or Narrow Line Region., Comment: 8 pages (including figures) uuencoded gziped PS file. Submitted to Publications of the Astronomical Society of Japan

We discuss photon emission from particles decelerlated by the cosmic expansion. This can be interpretated as a kind of bremsstrahlung induced by the Universe geometry. In the high momentum limit its transition probability does not depend on detailed behavior of the expansion., Comment: 20 pages, No figures

The X-ray spectrum obtained by Tanaka et al from a long observation of the active galaxy MCG$-6-30-15$ shows a broad iron K$\alpha$ line skewed to low energies. The simplest interpretation of the shape of the line is that it is due to doppler and gravitational redshifts from the inner parts of a disk about a massive black hole. Similarly broad lines are evident in shorter observations of several other active galaxies. In this paper we investigate other line broadening and skewing mechanisms such as Comptonization in cold gas and doppler shifts from outflows. We have also fitted complex spectral models to the data of MCG$-6-30-15$ to see whether the broad skewed line can be mimicked well by other absorption or emission features. No satisfactory mechanism or spectral model is found, thus strengthening the relativistic disk line model., Comment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.html

Using ASCA data, we have measured the electron temperature in A2163 out to 1.5h^{-1} Mpc (10a_x) from the center, in three radial bins. The temperatures are 12.2+1.9-1.2 keV, 11.5+2.7-2.9 keV and 3.8+1.1-0.9 keV (90%) in the 0-3 a_x (0-3.5'), 3-6 a_x and 6-13 a_x spherical shells, respectively. Applying the hydrostatic equilibrium and spherical symmetry assumptions and using these data together with the Ginga spectral and the Rosat imaging data, we were able to severely limit the possible binding mass distribution of the generic form rho=rho_0 (1+r^2/a_b^2)^{-n/2}. All the allowed binding mass profiles are steeper than the gas density profiles and mass profiles with the same slope as gas are excluded at a greater than 99% confidence. The total mass inside 0.5h^{-1} Mpc is 4.3+-0.5 10^14 h^{-1} Msun, of which 0.074 h^{-3/2} is gas while inside 1.5h^{-1} Mpc the mass is 1.07+-0.13 10^15 h^{-1} Msun. We note that in the cluster outer part, the timescale for electron-ion temperature equlibration is comparable to the merger timescale, so the measured electron temperature may give an underestimate of the gas pressure there. Otherwise, if our low temperature is indeed representative of the gas temperature in the outer shell, the cluster atmosphere should be convectionally unstable and gas turbulence should exist. Bulk motions of the gas are also expected during the merger. Their existense would increase the total gas pressure above that indicated by the observed temperature. Thus, failure of the "gas follows dark matter" model, favored by hydrodynamic simulations, may be due to the neglect of these phenomena, leading to an underestimate of the total density at large radii., Comment: 19 pages, 5 postscript figures, uses aaspp.sty. Accepted for ApJ

We present a detailed re-analysis of the two {\it ASCA} Performance Verification observations of the nearby Seyfert 1 galaxy MCG-6-30-15. Confirming the results of Fabian et al. (1994), we find definite evidence for the {\sc O\,vii} and {\sc O\,viii} K-shell absorption edges of the warm absorber and a doubling of the warm absorber column density within the 3 weeks separating the two observations. No intra-day {\it flux-correlated} variability of the warm absorber is found. However, we report the discovery of an `event' in which the warm absorber parameters temporarily change for \sim10\,000\thinspace s before returning to their original values. Possible interpretations are discussed but a contradiction remains: the constancy of the ionization state of the warm absorber argues that it lies at large distances from the central source whereas the short term change in column density argues for small distances. Fluorescent iron emission is examined. As found by Fabian et al. (1994), the iron line is broad and strong (equivalent width \sim300\thinspace eV). The line profile is also suggestive of it being skewed. Such a line would be expected from a relativistic accretion disk. We also find very rapid primary X-ray variability. Assuming relativistic beaming to be unimportant, the derived efficiency is comparable to the maximum obtainable from accretion onto a Schwarzschild black hole. Correlated variability outside of the energy range of {\it ASCA} might exceed this maximum, thus requiring efficient accretion onto a Kerr hole., Comment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.html

We present {\it ASCA} observations of the Seyfert 1 galaxies Mrk~1040 and MS~0225.5+3121. Mrk~1040 was found to have decreased in flux by almost a factor of 4 since an {\it EXOSAT} observation 10\,years ago. The energy spectrum of Mrk~1040 displays complexity both at soft energies (below 0.8\thinspace keV) and at hard energies (6--7\thinspace keV). The latter is readily interpreted as fluorescent K$\alpha$ emission from cold iron expected when the primary X-ray source illuminates cold optically-thick material. This line is both broad (with FWHM 16\,000--70\,000 km\,s$^{-1}$) and strong (equivalent width $\sim 550\pm 250$\, eV) suggesting that it originates from material close to the compact object with non-solar abundances. Abundance effects on the equivalent width of such a line are investigated via Monte Carlo simulations. We find that strong lines can be produced with physically plausible abundances. The effect of abundances on the associated reflection continuum is also discussed. The soft spectral complexity implies either a strong soft excess together with intrinsic absorption, or a complex absorber. Various models for the nature of such a complex absorber are discussed. MS~0225.5+3121 shows no evidence for any variability and has a spectrum that is well described by a power law with Galactic absorption., Comment: 8 pages (including figures) uuencoded compressed Postscript file. Submitted to Monthly Notices of the Royal Astronomical Society

The X-ray/radio transient superluminal jet source GRO J1655-40 was recently suggested to contain a black hole from optical observations. Because it is a relatively close-by system (d approximately 3.2 kpc), it can likely provide us with rich information about the physics operating in both Galactic and extragalactic jet sources. We present the first simultaneous broadband high-energy observations of GRO J1655-40 during the 1995 July-August outburst by three instruments: ASCA, WATCH/Granat, and BATSE/CGRO, in the energy band from 1 keV to 2 MeV. Our observations strengthen the interpretation that GRO J1655-40 contains a black hole. We detected a two-component energy spectrum, commonly seen from other Galactic black hole binaries, but never detected from a neutron star system. Combining our results with the mass limits derived from optical radial velocity and orbital period measurements, we further constrain the mass of the central object to be between 3.3 and 5.8 solar mass, above the well-established mass upper limit of 3.2 solar mass for a neutron star (the optical mass function for GRO J1655-40 is 3.16 + 0.2 solar mass). This system is therefore the first Galactic superluminal jet source for which there is strong evidence that the system contains a stellar mass black hole. The inclination angle of the binary system is constrained to be between 76 deg and 87 deg, consistent with estimates obtained from optical light curves and radio jet kinematics.

Attention is given to a series of observations of Centaurus X-3 made with Ginga on March 22-24, 1989, over a complete orbital cycle. The data set includes a preeclipse dip, the eclipse ingress and egress, the eclipse itself, and a phase of high steady emission after egress. The mideclipse ephemeris obtained yields an estimate of the rate of change of the orbital period of -(1.738 +/- 0.004) x 10 exp 6/yr, confirming the rate of change reported by Kelley et al. (1983) and improving the precision by a factor of 20. The pulse profiles obtained with Ginga during the high postegress phase are double-peaked at low energies, and show a reversal of phase of 180 deg. No pulsations are detected during the eclipse and at low energies during the preeclipse dip, indicating that X-ray emission at these phases is due to scattering by extended matter. The energy of the iron emission line varies between 6.5 and 6.7 keV during the observation, while its equivalent width varies between 0.18 and 1.5 keV.

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.

Simultaneous multifrequency observations of the BL Lac object Mrk 421 covering radio through X-ray wavelengths were performed on two occasions separated by 5 weeks in January and March 1984, and each observation was coordinated for about 1 week. Composite multifrequency spectra of the central nonthermal component were obtained at the two epochs after subtracting the optical and infrared light of the underlying galaxy. The spectra show the gradual steepening toward high frequency; the power law indices are about 0.1, about 0.6, and about 1.0 for radio, infrared-optical, and UV bands, respectively. The UV and optical-infrared fluxes decreased by about 20 percent in 5 weeks, while the radio flux remained stable. The X-ray flux decreased by a factor of about 2, and the change was more pronounced at hard X-rays, which suggest that X-ray emission possibly consists of two components. The degree of polarization at the optical band varied on the time scale of a few days, while the position angle remained unchanged. Physical parameters of Mrk 421 are discussed in terms of the synchrotron self-Compton model.

Eight methoxynitrophenazines with a methoxy group at the 1 or 2 position and a nitro group at the 6-, 7-, 8- or 9-position of the phenazine ring 1,6, 1,7. 1,8, 1,9, 2,6, 2,7, 2,8 and 2,9 were prepared and their photocurrents were measured by illuminating the surface-type cell with white light from a W lamp under a N atmosphere at room temp. The photocurrents of 1-nitrophenazine 6 and 2-nitrophenazine 7 are compared with those of the methoxynitrophenazines. The photocurrent (i sub p) increases with increasing light intensity (I), thus satisfying log i varies as n log I. The n values are 0.5-1.0. When the nitro group is located at the beta-position of the phenazine ring, the photocurrent becomes larger owing to the electron withdrawing property of the nitro group. On the other hand, the photocurrents of phenazines with the nitro group at the Alpha-position are extremely small. The photoconductivities of methoxynitrophenazines are lower in air.

The photocurrents of the substituted anthracenes, 1,5-diacetylanthracene (2), 1-acetylanthracene (3), 9-acetylanthracene (4), 1,5-dichloroanthracene (5), 1,5-diethylanthracene (6), 1,5-dimethoxyanthracene (7), 9-cyanoanthracene (8), and anthracene (1) were measured by using their surface type cells in nitrogen. The compounds of (1), (5), (6), (7), and (8) showed the photocurrent spectra which corresponded to the absorption spectra of their evaporated films. In the cases of (2) and (3), however, the anomalous photocurrent appeared in the threshold region of their absorption spectra. The appearance of the anomalous photocurrent was characteristic of anthracenes having the acetyl group at 1- and/or 5-position. The magnitude of the photocurrents of the 1,5-disubstituted anthracenes was similar to that of (1). The photocurrents of the monosubstituted anthracenes were smaller than that of (1). Among the monosubstituted anthracenes, the compound (4) showed no photocurrent under the same conditions. Contrary to the results obtained in the cases of phenazines, the photoconductivities of the anthracene derivatives became better in air.

The and/or photoconductivities of 16 substituted phenazines having methoxy, hydroxy, chloro, nitro, amino or t-butyl group at 1-, 2-, 1, 6- or 2,7- positions of the phenazine ring measured by using the surface type cells. The energy gaps of the dark conductivities in the range 2.0 to 2.3 were independent of the kinds and the positions of the substituent groups, although the photo-absorption wavelength of the evaporated films changed with them. No correlation between photoconductivity and fluorescence was observed. The photocurrent was affected by the position of the substituents; namely, the photocurrents of the 1,6-di-substituted phenazines. When the substituent at 1,6-positions was hydroxy or amino group, however, the photocurrents decreased. The photocurrents decreased drastically in the presence of oxygen.

The characteristics and preparation methods of Si3N4 are reviewed. Special emphasis is placed on the correlation between impurities and strength of sintered Si3N4.

Observations of simultaneous optical and X-ray bursts from 4U/MXB 1636-53 were made using the Hakucho burst monitor system and optical telescopes at the European Southern Observatory during 1979 and 1980. The six best cases among the 10 coinciding observations are analyzed in terms of a model in which the optical emission is the result of reprocessing of X-rays (through blackbody heating). From this analysis, the temperature (spatially averaged) and size of a reprocessor, and the smearing and delay of the optical bursts are obtained. For the maximum temperatures of the optical reprocessor, the values differ from burst to burst, ranging from about 3 x 10 to the 4th to about 10 to the 5th K. The present analysis suggests that the size of the reprocessor varies by a factor of a few. For the smearing of the optical bursts an upper limit of a few seconds is derived. The most important result of this analysis is that the delay times are not the same for all bursts. The possible constraints which these results put on a low-mass binary model of this burst source are discussed.

The X-ray pulsar Her X-1 was observed in an on-state during its 35th cycle of activity in May, 1983 using the gas scintillation proportional counter (GSPC) array of the Tenma X-ray astronomy satellite. The outstanding features observed during the declining phase of the on-state included: a sharp decrease in the main X-ray pulse amplitude; and a steady increase in the column density of cool matter. On the basis of the spectral shape of the pulses, it is suggested that the main phase was attenuated due to electron scattering of the X-ray beam in a highly ionized medium located 3 x 10 to the 8th cm from the neutron star. Near the end of the on-state, the main pulse totally disappeared and a plain sinusoidal profile was observed. The observed pulse profiles are reproduced in graphic form.

The paper reports partially simultaneous observations of the 'rapid burster' (MXB 1730-335) at X-ray, infrared, and radio wavelengths, covering several hundred hours during 1979 and 1980. None of the authors of this report saw any infrared or radio bursts. On several occasions an absence of infrared bursting was observed during X-ray bursting. On one occasion an absence of X-ray bursting was observed during a radio burst (4.1 GHz) reported by Calla et al. (1979). To date, radio bursts (a total of at least a dozen) have been reported only by Calla et al. (1980). Considering these and other observations summarized here, the reported radio bursts are either unreal or do not bear a simple relation to the X-ray bursts from the 'rapid burster'. The status of the reported infrared bursts also remain ambiguous. Limits to the brightness of any persistent radio source at the position of MXB 1730-335, limits to persistent X-ray emission during an extended X-ray quiet phase, and a measurement of the infrared polarization in the direction of the X-ray source are also reported.

Methods of obtaining information about the geometry of X-ray burster systems from simultaneous optical and X-ray observations are discussed, and such simultaneous observations of 4U/MXB 1636-53 are reported. The physical idea of an optical burst being due to reprocessing of an X-ray burst in material in the vicinity of the compact object is discussed. The resulting modification of the X-ray burst signal is described in terms of an optical response function. Delay and smearing due to radiative processes are discussed along with those due to the geometry. For 4U/MXB 1636-53, the estimated delay is 2.5 seconds, the smearing is less than four seconds, and the maximum temperature of the reprocessing region is about 75,000 K. The projected area of the reprocessing region is about 6 x 10 to the 21st square cm. The neutron star is about 1.4 solar masses, the radius of the accretion disk is greater than 1.5 lt-sec, and the mass of the Roche lobe filling companion star is less than 2.0 solar masses, corresponding to a binary period between about one and ten hours.

Effects of thirty additives on sintering A/N were investigated. The addition of alkali earth oxides and rare earth oxides gave fully densified aluminum nitride. This is due to the formation of nitrogen-containing aluminate liquid in the system aluminum nitride-alkali earth oxides or rare earth oxides. Microstructural studies of the sintered specimens with the above two types of additives suggested that the densification was due to the liquid phase sintering. Additions of silicon compounds resulted in poor densification by the formation of highly refractory compounds such as A/N polytypes.