Search

LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34GHz to 448GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Medium- and High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89-224GHz) and the High-Frequency Telescope (166-448GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD., Comment: SPIE Conference

LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with its expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic microwave background (CMB) polarization over the full sky with unprecedented precision. Its main scientific objective is to carry out a definitive search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with an insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. To this end, LiteBIRD will perform full-sky surveys for three years at the Sun-Earth Lagrangian point L2 for 15 frequency bands between 34 and 448 GHz with three telescopes, to achieve a total sensitivity of 2.16 micro K-arcmin with a typical angular resolution of 0.5 deg. at 100GHz. We provide an overview of the LiteBIRD project, including scientific objectives, mission requirements, top-level system requirements, operation concept, and expected scientific outcomes., Comment: 20 pages, 9 figures

LiteBIRD has been selected as JAXA's strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) $B$-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of $-56$ dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT : 34--161 GHz), one of LiteBIRD's onboard telescopes. It has a wide field-of-view ($18^\circ \times 9^\circ$) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90$^\circ$ are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at $5\,$K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented., Comment: 21 pages, 14 figures

We designed, fabricated, and measured anti-reflection coating (ARC) on sapphire that has 116% fractional bandwidth and transmission of at least 97% in the millimeter wave band. The ARC was based on patterning pyramid-like sub-wavelength structures (SWS) using ablation with a 15 W femto-second laser operating at 1030 nm. One side of each of two discs was fabricated with SWS that had a pitch of 0.54 mm and height of 2 mm. The average ablation volume removal rate was 1.6 mm$^{3}$/min. Measurements of the two-disc sandwich show transmission higher than 97% between 43 and 161 GHz. We characterize instrumental polarization (IP) arising from differential transmission due to asymmetric SWS. We find that with proper alignment of the two disc sandwich RMS IP across the band is predicted to be 0.07% at normal incidence, and less than 0.6% at incidence angles up to 20 degrees. These results indicate that laser ablation of SWS on sapphire and on other hard materials such as alumina is an effective way to fabricate broad-band ARC.

The low-lying isomeric state of $^{229}$Th provides unique opportunities for high-resolution laser spectroscopy of the atomic nucleus. We determine the energy of this isomeric state by taking the absolute energy difference between the excitation energy required to populate the 29.2-keV state from the ground-state and the energy emitted in its decay to the isomeric excited state. A transition-edge sensor microcalorimeter was used to measure the absolute energy of the 29.2-keV $\gamma$-ray. Together with the cross-band transition energy (29.2 keV$\to$ground) and the branching ratio of the 29.2-keV state measured in a recent study, the isomer energy was determined to be 8.30$\pm$0.92 eV. Our result is in agreement with latest measurements based on different experimental techniques, which further confirms that the isomeric state of $^{229}$Th is in the laser-accessible vacuum ultraviolet range., Comment: 6 pages, 4 figures, 2 tables

Inflation is the leading theory of the first instant of the universe. Inflation, which postulates that the universe underwent a period of rapid expansion an instant after its birth, provides convincing explanation for cosmological observations. Recent advancements in detector technology have opened opportunities to explore primordial gravitational waves generated by the inflation through B-mode (divergent-free) polarization pattern embedded in the Cosmic Microwave Background anisotropies. If detected, these signals would provide strong evidence for inflation, point to the correct model for inflation, and open a window to physics at ultra-high energies. LiteBIRD is a satellite mission with a goal of detecting degree-and-larger-angular-scale B-mode polarization. LiteBIRD will observe at the second Lagrange point with a 400 mm diameter telescope and 2,622 detectors. It will survey the entire sky with 15 frequency bands from 40 to 400 GHz to measure and subtract foregrounds. The U.S. LiteBIRD team is proposing to deliver sub-Kelvin instruments that include detectors and readout electronics. A lenslet-coupled sinuous antenna array will cover low-frequency bands (40 GHz to 235 GHz) with four frequency arrangements of trichroic pixels. An orthomode-transducer-coupled corrugated horn array will cover high-frequency bands (280 GHz to 402 GHz) with three types of single frequency detectors. The detectors will be made with Transition Edge Sensor (TES) bolometers cooled to a 100 milli-Kelvin base temperature by an adiabatic demagnetization refrigerator.The TES bolometers will be read out using digital frequency multiplexing with Superconducting QUantum Interference Device (SQUID) amplifiers. Up to 78 bolometers will be multiplexed with a single SQUID amplidier. We report on the sub-Kelvin instrument design and ongoing developments for the LiteBIRD mission., Comment: 7 pages 2 figures Journal of Low Temperature Physics - Special edition - LTD17 Proceeding

DIOS (Diffuse Intergalactic Oxygen Surveyor) is a small satellite aiming for a launch around 2020 with JAXA's Epsilon rocket. Its main aim is a search for warm-hot intergalactic medium with high-resolution X-ray spectroscopy of redshifted emission lines from OVII and OVIII ions. The superior energy resolution of TES microcalorimeters combined with a very wide field of view (30--50 arcmin diameter) will enable us to look into gas dynamics of cosmic plasmas in a wide range of spatial scales from Earth's magnetosphere to unvirialized regions of clusters of galaxies. Mechanical and thermal design of the spacecraft and development of the TES calorimeter system are described. We also consider revising the payload design to optimize the scientific capability allowed by the boundary conditions of the small mission., Comment: 10 pages, 11 figures, Proceedings of the SPIE Astronomical Instrumentation : Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray

ASTRO-H White Papers are meant to provide useful information to scientists who plan observations from the satellite. This short paper introduces the 16 ASTRO-H White Papers in addition to general description of the satellite and its new features., Comment: 5 pages, ASTRO-H White Paper

We have fabricated multilayer readout wiring Transition Edge Sensors (TES), which enable us to realize both large effective area and high-energy resolution for future X-ray astrophysical missions, such as DIOS. By sandwiching a SiO2 insulation layer between Al superconducting signal and return lines, self/mutual inductances and self fielding of bias leads are expected to be reduced. We fabricated 4x4 and 20x20 TES array on the multilayer wiring and tested their performance. Under the low temperature condition, several pixels in the TES array showed sharp superconducting transitions at around ~300 mK. We also succeeded in detecting X-ray signals from the 4x4 TES, contrary to the previous results of 20x20 TES. We further investigated the reasons for the differences between the 4x4 TES and the 20x20 TES, and present future plans for improving the multilayer TES array fabrication., Comment: 6 pagas, 4 figures, LTD15

LiteBIRD is a next-generation satellite mission to measure the polarization of the cosmic microwave background (CMB) radiation. On large angular scales the B-mode polarization of the CMB carries the imprint of primordial gravitational waves, and its precise measurement would provide a powerful probe of the epoch of inflation. The goal of LiteBIRD is to achieve a measurement of the characterizing tensor to scalar ratio $r$ to an uncertainty of $\delta r=0.001$. In order to achieve this goal we will employ a kilo-pixel superconducting detector array on a cryogenically cooled sub-Kelvin focal plane with an optical system at a temperature of 4~K. We are currently considering two detector array options; transition edge sensor (TES) bolometers and microwave kinetic inductance detectors (MKID). In this paper we give an overview of LiteBIRD and describe a TES-based polarimeter designed to achieve the target sensitivity of 2~$\mu$K$\cdot$arcmin over the frequency range 50 to 320~GHz., Comment: 6 pages, 2 figures

The Athena+ mission concept is designed to implement the Hot and Energetic Universe science theme submitted to the European Space Agency in response to the call for White Papers for the definition of the L2 and L3 missions of its science program. The Athena+ science payload consists of a large aperture high angular resolution X-ray optics and twelve meters away, two interchangeable focal plane instruments: the X-ray Integral Field Unit (X-IFU) and the Wide Field Imager (WFI). The X-IFU is a cryogenic X-ray spectrometer, based on a large array of Transition Edge Sensors (TES), offering 2.5 eV spectral resolution, with ~5" pixels, over a field of view of 5 arc minutes in diameter. In this paper, we briefly describe the Athena+ mission concept and the X-IFU performance requirements. We then present the X-IFU detector and readout electronics principles, the current design of the focal plane assembly, the cooling chain and review the global architecture design. Finally, we describe the current performance estimates, in terms of effective area, particle background rejection, count rate capability and velocity measurements. Finally, we emphasize on the latest technology developments concerning TES array fabrication, spectral resolution and readout performance achieved to show that significant progresses are being accomplished towards the demanding X-IFU requirements., Comment: Supporting paper for the science theme "The Hot and Energetic Universe" to be implemented by the Athena+ X-ray observatory (http://www.the-athena-x-ray-observatory.eu). 17 pages, 19 figures

ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z=10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z ~ 0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs., Comment: 34 pages, 13 figures. ESA Cosmic Vision medium-class mission (M3) proposal. Accepted for publication in Experimental Astronomy. Including minor corrections in the author list

The International X-Ray Observatory (IXO) will address fundamental questions in astrophysics, including "When did the first SMBH form? How does large scale structure evolve? What happens close to a black hole? What is the connection between these processes? What is the equation of state of matter at supra-nuclear density?" This report presents an overview of the assessment study phase of the IXO candidate ESA L-class Cosmic Vision mission. We provide a description of the IXO science objectives, the mission implementation and the payload. The performance will offer more than an order of magnitude improvement in capability compared with Chandra and XMM-Newton. This observatory-class facility comprises a telescope with highly nested grazing incidence optics with a performance requirement of 2.5 sq.m. of effective area at 1.25 keV with a 5" PSF. There is an instrument complement that provides capabilities in imaging, spatially resolved spectroscopy, timing, polarimetry and high resolution dispersive spectroscopy. Since earlier submissions to the Astro2010 Decadal Survey, substantial technological progress has been made, particularly in the mirror development. Risk reduction measures and important programmatic choices have also been identified. An independent internal Technical and Programmatic Review has also been carried out by ESA, concluding with positive recommendations. Subject to successful conclusion of agreements between the partner space agencies, IXO is fully ready to proceed to further definition, moving towards an eventual launch in 2021-2022., Comment: The full version of the Yellow Book and the Technical Review Board reports are available at http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=47796&fbodylongid=2176

The results from Suzaku observations of the central region of the Perseus cluster are presented. Deep exposures with the X-ray Imaging Spectrometer provide high quality X-ray spectra from the intracluster medium. X-ray lines from helium-like Cr and Mn have been detected significantly for the first time in clusters. In addition, elemental abundances of Ne, Mg, Si, S, Ar, Ca, Fe, and Ni are accurately measured within 10' (or 220 kpc) from the cluster center. The relative abundance ratios are found to be within a range of 0.8-1.5 times the solar value. These abundance ratios are compared with previous measurements, those in extremely metal-poor stars in the Galaxy, and theoretical models., Comment: 10 pages, 3 figures, accepted for ApJL

The soft diffuse X-ray emission of twelve fields observed with Suzaku are presented together with two additional fields from previous analyses. All have galactic longitudes 65 deg < l < 295 deg to avoid contributions from the very bright diffuse source that extends at least 30 deg from the Galactic center. The surface brightnesses of the Suzaku nine fields for which apparently uncontaminated ROSAT All Sky Survey (RASS) were available were statistically consistent with the RASS values, with an upper limit for differences of 17 x 10^{-6} c s^{-1} amin^{-2} in R45}-band. The Ovii and Oviii intensities are well correlated to each other, and Ovii emission shows an intensity floor at ~2 photons s^{-1} cm^{-2 str^{-1} (LU). The high-latitude Oviii emission shows a tight correlation with excess of Ovii emission above the floor, with (Oviii intensity) = 0.5 x [(Ovii intensity) -2 LU], suggesting that temperatures averaged over different line-of-sight show a narrow distribution around ~0.2 keV. We consider that the offset intensity of Ovii arises from the Heliospheric solar wind charge exchange and perhaps from the local hot bubble, and that the excess Ovii (2-7 LU) is emission from more distant parts of the Galaxy. The total bolometric luminosity of this galactic emission is estimated to be 4 x 10^{39} erg s^{-1}, and its characteristic temperature may be related to the virial temperature of the Galaxy., Comment: 22 Pages, 8 figures, to appear in PASJ (Vol.61 No.4)

Although about 40% of the soft X-ray background emission in 0.4 to 1 keV range has extragalactic origins and thus is totally blocked by the Galactic absorption in midplane directions, it decreases at most by about 20 % in midplane. Suzaku observation of the direction, (l, b) = (235, 0), showed an OVII Kalpha emission intensity comparable with that of the MBM-12 on cloud Suzaku observation, but revealed a narrow bump peaked at ~ 0.9 keV. The latter component is partly filling the decrease of the extragalactic component in midplane. The feature can be well represented by a thin thermal emission with a temperature of about 0.8 keV. Because of the high pressure implied for spatially extended hot gas, the emission is likely a sum of unresolved faint sources. We consider a large fraction of the emission originates from faint dM stars. We constructed a model spectrum for spatially unresolved dM stars that consistently explains the observed spectrum and the surface brightness. The model also suggests that the emission from dM stars decreases very rapidly with increasing b, and thus that it cannot compensate entirely the decrease of the extragalactic component at b ~ 2 - 10 deg., Comment: 8 pages, 4 figures, to appear in PASJ (Suzaku 3rd special issue)

We present Suzaku spectra of X-ray emission in the fields just off the LMC X-3 sight line. OVII, OVIII, and NeIX emission lines are clearly detected, suggesting the presence of an optically thin thermal plasma with an average temperature of 2.4E6. This temperature is significantly higher than that inferred from existing X-ray absorption line data obtained with Chandra grating observations of LMC X-3, strongly suggesting that the gas is not isothermal. We then jointly analyze these data to characterize the spatial and temperature distributions of the gas. Assuming a vertical exponential Galactic disk model, we estimate the gas temperature and density at the Galactic plane and their scale heights as 3.6(2.9, 4.7)E6 K and 1.4(0.3, 3.4)E-3 cm^{-3} and 1.4(0.2, 5.2) kpc and $2.8(1.0, 6.4)$ kpc, respectively. This characterization can account for all the \ovi line absorption, as observed in a FUSE spectrum of LMC X-3, but only predicts less than one tenth of the OVI line emission intensity typically detected at high Galactic latitudes. The bulk of the OVI emission most likely arises at interfaces between cool and hot gases., Comment: 10 pages, 7 figures, 3 tables, accepted for publication in ApJ, 2009

The NeXT (New exploration X-ray Telescope), the new Japanese X-ray Astronomy Satellite following Suzaku, is an international X-ray mission which is currently planed for launch in 2013. NeXT is a combination of wide band X-ray spectroscopy (3 - 80 keV) provided by multi-layer coating, focusing hard X-ray mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3 - 10 keV) provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD camera as a focal plane detector for a soft X-ray telescope and a non-focusing soft gamma-ray detector. With these instruments, NeXT covers very wide energy range from 0.3 keV to 600 keV. The micro-calorimeter system will be developed by international collaboration lead by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of Delta E ~ 7 eV by the micro-calorimeter will enable a wide variety of important science themes to be pursued., Comment: 14 pages, 10 figures, Proceedings of the SPIE meeting, "Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray 2008", Marseille (2008)

We present our proposal for a small X-ray mission DIOS (Diffuse Intergalactic Oxygen Surveyor), consisting of a 4-stage X-ray telescope and an array of TES microcalorimeters, cooled with mechanical coolers, with a total weight of about 400 kg. The mission will perform survey observations of warm-hot intergalactic medium using OVII and OVIII emission lines, with the energy coverage up to 1.5 keV. The wide field of view of about 50' diameter, superior energy resolution close to 2 eV FWHM, and very low background will together enable us a wide range of science for diffuse X-ray sources. We briefly describe the design of the satellite, performance of the subsystems and the expected results., Comment: 9 pages, 11 figures, a proceedings of SPIE "Astronomical Telescopes and Instrumentation" 2006

We present results from Chandra observations of SDSS J1004+4112, a strongly lensed quasar system with a maximum image separation of 15". All four bright images of the quasar, as well as resolved X-ray emission originating from the lensing cluster, are clearly detected. The emission from the lensing cluster extends out to approximately 1.5 arcmin. We measure the bolometric X-ray luminosity and temperature of the lensing cluster to be 4.7e44 erg s^-1 and 6.4 keV, consistent with the luminosity-temperature relation for distant clusters. The mass estimated from the X-ray observation shows excellent agreement with the mass derived from gravitational lensing. The X-ray flux ratios of the quasar images differ markedly from the optical flux ratios, and the combined X-ray spectrum of the images possesses an unusually strong Fe Kalpha emission line, both of which are indicative of microlensing., Comment: 9 pages, 5 figures. Accepted for publication in ApJ. Version with high-quality color figures at http://cosmic.riken.jp/ota/publications/index.html

To detect a warm-hot intergalactic medium associated with the large-scale structure of the universe, we observed a quasar behind the Virgo cluster with XMM-Newton. With a net exposure time of 54 ks, we marginally detected an OVIII K alpha absorption line at 650.9 +0.8/-1.9 eV in the RGS spectra, with a statistical confidence of 96.4 %. The observed line center energy is consistent with the redshift of M87, and hence the absorber is associated with the Virgo cluster. From the curve of growth, the OVIII column density was estimated to be > 7 x 10^16 cm^-2. In the EPIC spectra, excess emission was found after evaluating the hot intracluster medium in the Virgo cluster and various background components. We inspected the ROSAT All-Sky Survey map of the diffuse soft X-ray background, and confirmed that the level of the north and west regions just outside of the Virgo cluster is consistent with the background model that we used, while that of the east side is significantly higher and the enhancement is comparable with the excess emission found in the EPIC data. We consider a significant portion of the excess emission to be associated with the Virgo cluster, although a possible contribution from the North Polar Spur cannot be excluded. Using the column density and the emission measure and assuming an oxygen abundance of 0.1 and an ionization fraction of 0.4, we estimate that the mean electron density and the line-of-sight distance of the warm-hot gas are < 6 x 10^-5 cm^-3 and > 9 Mpc, respectively. These numbers strongly suggest that we have detected a warm-hot intergalactic medium in a filament associated with the Virgo cluster., Comment: 6 pages, 4 figures. Accepted for publication in PASJ. A reference is added

We present an analysis of mock spectral observation of warm-hot intergalactic medium (WHIM) using a constrained simulation of the local universe. The simulated map of oxygen emission lines from local WHIM reproduces well the observed structures traced by galaxies in the real local universe. We further attempt to perform mock observations of outer parts of simulated Coma cluster and A3627 adopting the expected performance of DIOS (Diffuse Intergalactic Oxygen Surveyor), which is proposed as a dedicated soft X-ray mission to search for cosmic missing baryons. We find that WHIMs surrounding nearby clusters are detectable with a typical exposure time of a day, and thus constitute realistic and promising targets for DIOS. We also find that an X-ray emitting clump in front of Coma cluster, recently reported in the XMM-Newton observation, has a counterpart in the simulated local universe, and its observed spectrum can be well reproduced in the simulated local universe if the gas temperature is set to the observationally estimated value., Comment: 25 pages, 3 tables, 16 figures. Accepted for publication in PASJ. High resolution PS/PDF files are available at http://www-utap.phys.s.u-tokyo.ac.jp/~kohji/research/x-ray/index.html

We present our proposal for a small X-ray mission DIOS (Diffuse Intergalactic Oxygen Surveyor) to perform survey observations of warm-hot intergalactic medium using OVII and OVIII emission lines. This will be proposed to a small satellite program planned by ISAS/JAXA in Japan for a launch in 2008. The instrument consists of an array of TES microcalorimeters with an energy resolution 2 eV, cooled by mechanical coolers. The X-ray telescope will employ 4-stage reflection mirrors with a focal length as short as 70 cm and an angular resolution 2'. In addition to DIOS, we briefly describe the NeXT (New X-ray Telescope) mission, which is a larger Japanese X-ray observatory to be launched in 2010 and plans to explore non-thermal processes in the universe., Comment: 6 pages, 9 figures. To appear in the proceedings of "Modelling the Intergalactic and Intracluster Media", Vulcano Island, October 1-4, 2003

The Astro-E2 high resolution X-Ray Spectrometer (XRS) is expected to provide a major enhancement in study of clusters of galaxies. Astro-E2 is the fifth Japanese X-ray astronomy observatory, which is scheduled for launch in early 2005. The XRS instrument, developed under a Japan-US collaboration, is an X-ray microcalorimeter with a capability of observing extended objects, and a high energy resolution of about 6 eV at 6 keV. The spectral resolving power is 20 times higher than CCDs over the 0.5-10 keV energy band. We have obtained several new results of clusters with Chandra and XMM, which show that high-resolution imaging spectroscopy can clarify some outstanding questions. New sciences from Astro-E2 include the first clear measurement of gas velocities, determination of ion and electron temperatures, and electron densities based on the resolved line features. We will describe the XRS instrument design, and present simulations of the expected performance., Comment: 6 pages, 7 figures. To appear in the proceedings of "Modelling the Intergalactic and Intracluster Media", Vulcano Island, October 1-4, 2003. Gzipped postscript and pdf with higher resolution figures also available at http://www-x.phys.metro-u.ac.jp/~furusho/papers.html

We present the X-ray energy spectrum of the lensed BAL QSO H1413+117 (the Cloverleaf) at z=2.56 observed with the Chandra X-ray observatory. We detected 293 photons in a 40 ks Advanced CCD Imaging Spectrometer (ACIS-S) observation. The X-ray image consists of four lensed image components, thus the photons are from the lensed QSO itself. The overall spectrum can be described with a power-law function heavily absorbed by neutral matter at a redshift consistent with the QSO redshift. This supports the idea that intrinsic absorption is significant for BAL QSOs. The spectral fit significantly (99% confidence) improves when we include an emission line. The centroid energy and intrinsic width (Gaussian \sigma) of the line are 6.21 \pm 0.16 keV and 220 ^{+270}_{-130} eV (90% errors), respectively, in the QSO rest frame, assuming the absorbed power-law as the continuum. The equivalent width of the line in the QSO rest frame is 960 ^{+1400}_{-480} eV. We suggest that the large equivalent width, the centroid energy, and the line broadness can be explained by iron K emission arising from X-ray reprocessing in the BAL flow, assuming it has a conical thin-sheet structure., Comment: 3 figures, Accepted for publication in ApJ Letters

The X-ray emission from the central region of the Galactic plane, |l|<45 deg and |b|<0.4 deg, was studied in the 0.7-10 keV energy band with a spatial resolution of ~3' with the ASCA observatory. We developed a new analysis method for the ASCA data to resolve discrete sources from the extended Galactic ridge X-ray emission (GRXE). We resolved 163 discrete sources with a flux down to 10^-12.5 ergs cm^-2 s^-1 and determined the intensity variations of the GRXE as a function of the Galactic longitude with a spatial resolution of ~1 deg. The longitudinal variation of the GRXE in the energy band above 4 keV shows a large enhancement within |l|<30 deg. This suggests a strong enhancement of X-ray emissivity inside the 4-kpc arms. Searches for identifications of the resolved sources with cataloged X-ray sources and optical stars show that the 66% are unidentified. Spectral analysis of each source shows that a large number of the unidentified sources have hard X-ray spectra. We classified the sources into several groups according to the spectra and analyzed the spectra summed within each group. Possible X-ray origins of these sources are discussed based on the grouping analysis. Also, we derived the LogN-LogS relations of the resolved sources in the energy bands below and above 2 keV. The obtained LogN-LogS relation of the Galactic X-ray sources above 2 keV is represented by a power-law with an index of -0.79+/-0.07. This flat LogN-LogS relation suggests that the spatial distribution of the sources should have an arm-like structure in which the Solar system is included. The integrated surface brightness of the resolved sources is about 10% of the total GRXE in both energy bands. The approximately 90% of the emission remaining is still unresolved., Comment: 54 pages, 12 figures, accepted for publication in ApJ Supplements Series

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 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 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