Author
Kai Wing Chan
Other affiliations: University of Maryland, College Park, University of Maryland, Baltimore County, Harvard University
Bio: Kai Wing Chan is an academic researcher from Goddard Space Flight Center. The author has contributed to research in topics: Telescope & X-ray telescope. The author has an hindex of 11, co-authored 19 publications receiving 1257 citations. Previous affiliations of Kai Wing Chan include University of Maryland, College Park & University of Maryland, Baltimore County.
Topics: Telescope, X-ray telescope, Grating, Observatory, Spectrometer
Papers
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Massachusetts Institute of Technology1, Goddard Space Flight Center2, Kyoto University3, Nagoya University4, University of Tokyo5, Osaka University6, Ehime University7, University of Cambridge8, Hiroshima University9, Carnegie Mellon University10, Max Planck Society11, University of Miyazaki12, Franklin W. Olin College of Engineering13, Rutgers University14, Tokyo Metropolitan University15, Kobe University16, Stanford University17, Tokyo Institute of Technology18, Rikkyo University19, Kogakuin University20, Tokyo University of Science21, University of Wisconsin-Madison22, Kanazawa University23, Nihon University24, Pennsylvania State University25, European Space Research and Technology Centre26, Yale University27, Saitama University28, Chuo University29, University of Leicester30, Nihon Fukushi University31, Aoyama Gakuin University32, Iwate University33
TL;DR: In this paper, the authors summarized the spacecraft, in-orbit performance, operations, and data processing that are related to observations of the Suzaku X-ray observatory, including high-sensitivity wide-band Xray spectroscopy.
Abstract: High-sensitivity wide-band X-ray spectroscopy is the key feature of the Suzaku X-ray observatory, launched on 2005 July 10. This paper summarizes the spacecraft, in-orbit performance, operations, and data processing that are related to observations. The scientific instruments, the high-throughput X-ray telescopes, X-ray CCD cameras, non-imaging hard X-ray detector are also described.
908 citations
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TL;DR: The practical use of a grazing x-ray telescope is demonstrated for hard-x-ray imaging as hard as 40 keV by means of a depth-graded d-spacing multilayer, a so-called supermirror.
Abstract: The practical use of a grazing x-ray telescope is demonstrated for hard-x-ray imaging as hard as 40 keV by means of a depth-graded d-spacing multilayer, a so-called supermirror. Platinum-carbon multilayers of 26 layer pairs in three blocks with a different periodic length d of 3-5 nm were designed to enhance the reflectivity in the energy range from 24 to 36 keV at a grazing angle of 0.3 deg. The multilayers were deposited on thin-replica-foil mirrors by a magnetron dc sputtering system. The reflectivity was measured to be 25%-30% in this energy range; 20 mirror shells thus deposited were assembled into the tightly nested grazing-incidence telescope. The focused hard-x-ray image was observed with a newly developed position-sensitive CdZnTe solid-state detector. The angular resolution of this telescope was found to be 2.4 arc min in the half-power diameter.
84 citations
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TL;DR: In this article, a novel grating fabrication method that utilizes common lithographic and microfabrication techniques to produce the high fidelity groove profile necessary to achieve high resolving power grating spectrometers is presented.
Abstract: Future NASA X-ray spectroscopy missions will require high throughput, high resolving power grating spectrometers Off-plane reflection gratings are capa- ble of meeting the performance requirements needed to realize the scientific goals of these missions We have identified a novel grating fabrication method that utilizes common lithographic and microfabrication techniques to produce the high fidelity groove profile necessary to achieve this performance Application of this process has produced an initial pre-master that exhibits a radial (variable line spacing along the groove dimension), high density (>6000 grooves/mm), laminar profile This pre- master has been tested for diffraction efficiency at the BESSY II synchrotron light facility and diffracts up to 55 % of incident light into usable spectral orders Fur- thermore, tests of spectral resolving power show that these gratings are capable of obtaining resolving powers well above 1300 (λ/�λ ) with limitations due to the test apparatus, not the gratings Obtaining these results has provided confidence that this
66 citations
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TL;DR: X-ray telescopes (XRT's) of nested thin foil mirrors are developed for Astro-E, the fifth Japanese x-ray astronomy satellite, although the launch was not successful, the design concept, fabrication, and alignment procedure are summarized.
Abstract: X-ray telescopes (XRT’s) of nested thin foil mirrors are
developed for Astro-E, the fifth Japanese x-ray astronomy
satellite. Although the launch was not successful, the design
concept, fabrication, and alignment procedure are summarized. The
main purpose of the Astro-E XRT is to collect hard x rays up to 10 keV
with high efficiency and to provide medium spatial resolution in
limited weight and volume. Compared with the previous mission,
Advanced Satellite for Cosmology and Astrophysics (ASCA), a
slightly longer focal length of 4.5–4.75 m and a larger diameter of 40
cm yields an effective area of 1750 cm2 at 8 keV with five
telescopes. The image quality is also improved to 2-arc min
half-power diameter by introduction of a replication
process. Platinum is used instead of gold for the reflectors of one
of the five telescopes to enhance the high-energy response. The
fabrication and alignment procedure is also summarized. Several
methods for improvement are suggested for the reflight Astro-E II
mission and for other future missions. Preflight calibration
results will be described in a forthcoming second paper, and a detailed
study of images will be presented in a third paper.
44 citations
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TL;DR: A hard-x-ray telescope is successfully produced for balloon observations by making use of depth-graded multilayers, or so-called supermirrors, with platinum-carbon (Pt/C) layer pairs by taking into account the figure errors of reflectors and their optical alignment in the telescope assembly.
Abstract: A hard-x-ray telescope is successfully produced for balloon observations by making use of depth-graded multilayers, or so-called supermirrors, with platinum–carbon (Pt/C) layer pairs. It consists of four quadrant units assembled in an optical configuration with a diameter of 40 cm and a focal length of 8 m. Each quadrant is made of 510 pieces of coaxially and confocally aligned supermirrors that significantly enhance the sensitivity in an energy range of 20–40 keV. The configuration of the telescope is similar to the x-ray telescope onboard Astro-E, but with a longer focal length. The reflectivity of supermirrors is of the order of 40% in the energy range concerned at a grazing angle of 0.2 deg. The effective area of a fully assembled telescope is 50 cm2 at 30 keV. The angular resolution is 2.37 arc min at half-power diameter 8.0 keV. The field of view is 12.6 arc min in the hard-x-ray region, depending somewhat on x-ray energies. We discuss these characteristics, taking into account the figure errors of reflectors and their optical alignment in the telescope assembly. This hard-x-ray telescope is unanimously afforded in the International Focusing Optics Collaboration for µCrab Sensitivity balloon experiment.
35 citations
Cited by
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TL;DR: In this article, a catalog of gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite is presented.
Abstract: This catalog summarizes 117 high-confidence > 0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data, through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.
929 citations
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TL;DR: In this article, the design parameters, production process, and in-flight performance of the X-ray telescopes (XRTs) onboard Suzaku were presented. And the optical axes were found to be distributed within a radius of 1. 0 8 −2.
Abstract: We present the design parameters, production process, and in-flight performance of the X-ray telescopes (XRTs) onboard Suzaku. The imaging capability is significantly improved over the ASCA XRT, which had half-power diameters of 3. 0 6, to 1. 0 8–2. 0 3 for all four XRT-I modules. The optical axes are found to be distributed within a radius of 1. 3, which makes the observation efficiency of all the XRTs more than 97% at the XIS-default observing position. The vignetting over the XIS field of view predicted via ray-tracing coincides with that measured for observations of the Crab Nebula to within »10%. Contemporaneous fits of a power law to all the XIS spectra of the Crab Nebula taken at the two standard observing positions (XIS/HXDdefault positions) gives a flux consistent with that obtained by Toor & Seward (1974) to within »2%. The pre-collimator on the top of each XRT module successfully re
615 citations
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Tokyo Metropolitan University1, Japan Aerospace Exploration Agency2, Kyoto University3, Nagoya University4, Johns Hopkins University5, Goddard Space Flight Center6, Universities Space Research Association7, University of Maryland, Baltimore County8, Tokyo Institute of Technology9, Osaka University10, Massachusetts Institute of Technology11
TL;DR: In this article, a framework for the Monte-Carlo simulation of X-Ray Telescopes (XRT) and X-ray Imaging Spectrometers (XIS) onboard Suzaku was developed for the scientific analysis of spatially and spectroscopically complex celestial sources.
Abstract: 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.
569 citations
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TL;DR: In this article, the number density and evolution of active galactic nuclei (AGNs) in the local universe were investigated using the wide-area surveys from the Swift and INTEGRAL satellites.
Abstract: We constrain the number density and evolution of Compton-thick (CT) active galactic nuclei (AGNs). In the local universe, we use the wide-area surveys from the Swift and INTEGRAL satellites, while for high redshifts we explore candidate selections based on a combination of X-ray and mid-infrared (mid-IR) parameters. We find a significantly lower space density of CT AGNs in the local universe than expected from published AGN population synthesis models to explain the X-ray background (XRB). This can be explained by the numerous degeneracies in the parameters of those models; we use the high-energy surveys described here to remove those degeneracies. We show that only direct observations of CT AGNs can currently constrain the number of heavily obscured supermassive black holes. At high redshift, the inclusion of IR-selected CT AGN candidates leads to a much higher space density, implying (1) a different (steeper) evolution for these sources compared to less-obscured AGNs, (2) that the IR selection includes a large number of interlopers, and/or (3) that there is a large number of reflection-dominated AGNs missed in the INTEGRAL and Swift observations. The contribution of CT AGN to the XRB is small, ~9%, with a comparable contribution to the total cosmic accretion, unless reflection-dominated CT AGNs significantly outnumber transmission-dominated CT AGNs, in which case their contribution can be much higher. Using estimates derived here for the accretion luminosity over cosmic time, we estimate the local mass density in supermassive black holes and find a good agreement with available constraints for an accretion efficiency of ~10%. Transmission-dominated CT AGNs contribute only ~8% to total black hole growth.
385 citations
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TL;DR: In this article, a piece-wise linear spline function was proposed to modify the vignetting response of the nuclear Spectroscopic Telescope Array (NuSTAR) X-ray satellite.
Abstract: We present the calibration of the Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray satellite. We used the Crab as the primary effective area calibrator and constructed a piece-wise linear spline function to modify the vignetting response. The achieved residuals for all off-axis angles and energies, compared to the assumed spectrum, are typically better than ±2% up to 40 keV and 5%–10% above due to limited counting statistics. An empirical adjustment to the theoretical two-dimensional point-spread function (PSF) was found using several strong point sources, and no increase of the PSF half-power diameter has been observed since the beginning of the mission. We report on the detector gain calibration, good to 60 eV for all grades, and discuss the timing capabilities of the observatory, which has an absolute timing of ±3 ms. Finally, we present cross-calibration results from two campaigns between all the major concurrent X-ray observatories (Chandra, Swift, Suzaku, and XMM-Newton), conducted in 2012 and 2013 on the sources 3C 273 and PKS 2155-304, and show that the differences in measured flux is within ~10% for all instruments with respect to NuSTAR.
345 citations