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Charge-changing cross sections $\sigma_\mathrm{CC}$ for $^{42\textrm{--}51}$Ca on a carbon target at around 280~MeV/nucleon have been measured. The measured $\sigma_\mathrm{CC}$ values differ significantly from the previously developed calculations based on the Glauber model. However, through introduction of the charged-particle evaporation effect induced by the neutron-removal reaction in addition to the Glauber-model calculation, experimental $\sigma_\mathrm{CC}$ values on $^{12}$C at around 300~MeV/nucleon for nuclides from C to Fe isotopes are all reproduced with approximately 1\% accuracy. This proposed model systematically reproduces $\sigma_\mathrm{CC}$ data without phenomenological corrections, and can also explain experimental $\sigma_\mathrm{CC}$ values obtained in other energy regions., Comment: 13 pages, 11 figures

Interaction cross sections for $^{42\textrm{-}51}$Ca on a carbon target at 280 MeV/nucleon have been measured for the first time. The neutron number dependence of derived root-mean-square matter radii shows a significant increase beyond the neutron magic number $N=28$. Furthermore, this enhancement of matter radii is much larger than that of the previously measured charge radii, indicating a novel growth in neutron skin thickness. A simple examination based on the Fermi-type distribution, and the Mean-Field calculations point out that this anomalous enhancement of the nuclear size beyond $N=28$ results from an enlargement of the core by a sudden increase in the surface diffuseness of the neutron density distribution, which implies the swelling of the bare $^{48}$Ca core in Ca isotopes beyond $N=28$., Comment: 6 pages, 3 figures

Suzaku X-ray observations of a young supernova remnant, Cassiopeia A, were carried out. K-shell transition lines from highly ionized ions of various elements were detected, including Chromium (Cr-Kalpha at 5.61 keV). The X-ray continuum spectra were modeled in the 3.4--40 keV band, summed over the entire remnant, and were fitted with a simplest combination of the thermal bremsstrahlung and the non-thermal cut-off power-law models. The spectral fits with this assumption indicate that the continuum emission is likely to be dominated by the non-thermal emission with a cut-off energy at > 1 keV. The thermal-to-nonthermal fraction of the continuum flux in the 4-10 keV band is best estimated as ~0.1. Non-thermal-dominated continuum images in the 4--14 keV band were made. The peak of the non-thermal X-rays appears at the western part. The peak position of the TeV gamma-rays measured with HEGRA and MAGIC is also shifted at the western part with the 1-sigma confidence. Since the location of the X-ray continuum emission was known to be presumably identified with the reverse shock region, the possible keV-TeV correlations give a hint that the accelerated multi-TeV hadrons in Cassiopeia A are dominated by heavy elements in the reverse shock region., Comment: Publ. Astron. Soc. Japan 61, pp.1217-1228 (2009)

Tycho's supernova remnant was observed by the XIS and HXD instruments onboard the Suzaku satellite on 2006 June 26-29 for 92 ks. The spectrum up to 30 keV was well fitted with a two-component model, consisting of a power-law with photon index of 2.7 and a thermal bremsstrahlung model with temperature of 4.7 keV. The former component can alternatively be modeled as synchrotron emission from a population of relativistic electrons with an estimated roll-off energy of around 1 keV. In the XIS spectra, in addition to the prominent Fe K_alpha line (6.445 keV), we observe for the first time significant K_alpha line emission from the trace species Cr and Mn at energies of 5.48 keV and 5.95 keV, respectively. Faint K_beta lines from Ca (4.56 keV) and Fe (7.11 keV) are also seen. The ionization states of Cr and Mn, based on their line centroids, are estimated to be similar to that of Fe K_alpha (Fe XV or XVI)., Comment: 11 pages, 8 figures, accepted by PASJ

We present the results of a spatially resolved spectral analysis from four Suzaku observations covering the northeastern rim of the Cygnus Loop. A two-kT_e non-ionization equilibrium (NEI) model fairly well represents our data, which confirms the NEI condition of the plasma there. The metal abundances are depleted relative to the solar values almost everywhere in our field of view. We find abundance inhomogeneities across the field: the northernmost region (Region A) has enhanced absolute abundances compared with other regions. In addition, the relative abundances of Mg/O and Fe/O in Region A are lower than the solar values, while those in the other regions are twice higher than the solar values. As far as we are concerned, neither a circumstellar medium, fragments of ejecta, nor abundance inhomogeneities of the local interstellar medium around the Cygnus Loop can explain the relatively enhanced abundance in Region A. This point is left as an open question for future work., Comment: 13 pages, 6 figures

We observed a linearly sliced area of the Cygnus Loop from the north-east to the south-west with Suzaku in seven pointings. After dividing the entire fields of view (FOV) into 119 cells, we extracted spectra from all of the cells and performed spectral analysis for them. We then applied both one- and two-component non-equilibrium ionization (NEI) models for all of the spectra, finding that almost all were significantly better fitted by the two-component NEI model rather than the one-component NEI model. Judging from the abundances, the high-kT_e component must be the ejecta component, while the low-kT_e component comes from the swept-up matter. Therefore, the ejecta turn out to be distributed inside a large area (at least our FOV) of the Cygnus Loop. We divided the entire FOV into northern and southern parts, and found that the ejecta distributions were asymmetric to the geometric center: the ejecta of Si, S, and Fe seem to be distributed more in the south than in the north of the Cygnus Loop by a factor of about 2. The degree of ejecta-asymmetry is consistent with that expected by recent supernova explosion models., Comment: 14 pages, 4 figures

The NeXT mission has been proposed to study high-energy non-thermal phenomena in the universe. The high-energy response of the super mirror will enable us to perform the first sensitive imaging observations up to 80 keV. The focal plane detector, which combines a fully depleted X-ray CCD and a pixellated CdTe detector, will provide spectra and images in the wide energy range from 0.5 keV to 80 keV. In the soft gamma-ray band up to ~1 MeV, a narrow field-of-view Compton gamma-ray telescope utilizing several tens of layers of thin Si or CdTe detector will provide precise spectra with much higher sensitivity than present instruments. The continuum sensitivity will reach several times 10^(-8) photons/s/keV/cm^(2) in the hard X-ray region and a few times10^(-7) photons/s/keV/cm^(2) in the soft gamma-ray region., Comment: 12 pages, 13 figures, to be published in the SPIE proceedings 5488, typo corrected in sec.3

We report on a new photon-counting detector possessing unprecedented spatial resolution, moderate spectral resolution and high background-rejection capability for 0.1-100 keV X-rays. It consists of an X-ray charge-coupled device (CCD) and scintillator. The scintillator is directly deposited on the back surface of the X-ray CCD. Low-energy X-rays below 10 keV can be directly detected in the CCD. The majority of hard X-rays above 10 keV pass through the CCD but can be detected in the scintillator, generating optical photons there. Since CCDs have a moderate detection efficiency for optical photons, they can again be absorbed by the CCD. We demonstrate the high spatial resolution of 10 micron order for 17.4 keV X-rays with our prototype device., Comment: 7 pages, 4 figures. Accepted for publication of Japanese Journal of Applied Physics Letter

We have investigated the radiation damage effects on a CCD to be employed in the Japanese X-ray astronomy mission including the Monitor of All-sky X-ray Image (MAXI) onboard the International Space Station (ISS). Since low energy protons release their energy mainly at the charge transfer channel, resulting a decrease of the charge transfer efficiency, we thus focused on the low energy protons in our experiments. A 171 keV to 3.91 MeV proton beam was irradiated to a given device. We measured the degradation of the charge transfer inefficiency (CTI) as a function of incremental fluence. A 292 keV proton beam degraded the CTI most seriously. Taking into account the proton energy dependence of the CTI, we confirmed that the transfer channel has the lowest radiation tolerance. We have also developed the different device architectures to reduce the radiation damage in orbit. Among them, the ``notch'' CCD, in which the buried channel implant concentration is increased, resulting in a deeper potential well than outside, has three times higher radiation tolerance than that of the normal CCD. We then estimated the charge transfer inefficiency of the CCD in the orbit of ISS, considering the proton energy spectrum. The CTI value is estimated to be 1.1e-5 per each transfer after two years of mission life in the worse case analysis if the highest radiation-tolerant device is employed. This value is well within the acceptable limit and we have confirmed the high radiation-tolerance of CCDs for the MAXI mission., Comment: 17 pages, 2 table, 12 figures. Accepted for publication of Japanese Journal of Applied Physics. High resolution file is available from http://wwwxray.ess.sci.osaka-u.ac.jp/~miyata/paper/proton_cti.pdf

We have employed a mesh experiment for back-illuminated (BI) CCDs. BI CCDs possess the same structure to those of FI CCDs. Since X-ray photons enter from the back surface of the CCD, a primary charge cloud is formed far from the electrodes. The primary charge cloud expands through diffusion process until it reaches the potential well that is just below the electrodes. Therefore, the diffusion time for the charge cloud produced is longer than that in the FI CCD, resulting a larger charge cloud shape expected. The mesh experiment enables us to specify the X-ray point of interaction with a subpixel resolution. We then have measured a charge cloud shape produced in the BI CCD. We found that there are two components of the charge cloud shape having different size: a narrow component and a broad component. The size of the narrow component is $2.8-5.7 \mu$m in unit of a standard deviation and strongly depends on the attenuation length in Si of incident X-rays. The shorter the attenuation length of X-rays is, the larger the charge cloud becomes. This result is qualitatively consistent with a diffusion model inside the CCD. On the other hand, the size of the broad component is roughly constant of $\simeq 13 \mu$m and does not depend on X-ray energies. Judging from the design value of the CCD and the fraction of each component, we conclude that the narrow component is originated in the depletion region whereas the broad component is in the field-free region., Comment: 14 pages, 1 table, 10 figures. Accepted for publication of Japanese Journal of Applied Physics. High resolution file is available from http://wwwxray.ess.sci.osaka-u.ac.jp/~miyata/paper/mesh_bi_jjap.pdf

A charge-coupled device (CCD) is a standard imager in optical region in which the image quality is limited by its pixel size. CCDs also function in X-ray region but with substantial differences in performance. An optical photon generates only one electron while an X-ray photon generates many electrons at a time. We developed a method to precisely determine the X-ray point of interaction with subpixel resolution. In particular, we found that a back-illuminated CCD efficiently functions as a fine imager. We present here the validity of our method through an actual imaging experiment., Comment: 7 pages, 2 figures. Accepted for publication of Japanese Journal of Applied Physics Express Letter. High resolution file is available from http://wwwxray.ess.sci.osaka-u.ac.jp/~miyata/paper/bi_sharp_res.pdf

Monitor of All-sky X-ray Image (MAXI) on the International Space Station (ISS) has two kinds of X-ray detectors: the Gas Slit Camera (GSC) and the Solid-state Slit Camera (SSC). SSC is an X-ray CCD array, consisting of 16 chips, which has the best energy resolution as an X-ray all-sky monitor in the energy band of 0.5 to 10 keV. Each chip consists of 1024x1024 pixels with a pixel size of 24$\mu$m, thus the total area is ~200 cm^2. We have developed an engineering model of SSC, i.e., CCD chips, electronics, the software and so on, and have constructed the calibration system. We here report the current status of the development and the calibration of SSC., Comment: To appear in the Proc. of "MAXI Workshop on AGN Variability", 10-11 March 2001, Nikko, Japan (5 pages, 5 Figs, requires psbox.sty), also found in http://www-maxi.tksc.nasda.go.jp/%7Esakano/work/paper/ index-e.html#Sakano2001MAXI

The newly discovered supernova remnant G266.2-1.2 (RX J0852.0-4622), along the line of sight to the Vela SNR, was observed with ASCA for 120 ks. We find that the X-ray spectrum is featureless, and well described by a power law, extending to three the class of shell-type SNRs dominated by nonthermal X-ray emission. Although the presence of the Vela SNR compromises our ability to accurately determine the column density, the GIS data appear to indicate absorption considerably in excess of that for Vela itself, indicating that G266.2-1.2 may be several times more distant. An unresolved central source may be an associated neutron star, though difficulties with this interpretation persist., Comment: 4 pages, 5 figures, uses aipproc.sty & epsfig.sty. To appear in "Young Supernova Remnants" (11th Annual Astrophysics Conference in Maryland), S. S. Holt & U. Hwang (eds), AIP, New York (2001)

When an X-ray photon lands into a pixel (event pixel), the primary charge is mainly collected into the event pixel. If the X-ray landing position is sufficiently close to the pixel boundary, the primary charge spills over to the adjacent pixel forming split events. We can easily understand that there are three parameters coupled together; the X-ray landing position inside the pixel, the X-ray event pattern and the primary charge cloud shape. We can determine any one of them from the other two parameters. Since we know the charge cloud shape using the multi-pitch mesh experiment, we can calculate the X-ray landing position with subpixel resolution using the event pattern. We applied our method to Ti-K X-rays for the charge-coupled device with $12 \mu$m square pixel. Once the primary charge splits into the adjacent pixel, we can determine the X-ray landing position with subpixel resolution. Using three- or four-pixel split events, we can determine the X-ray landing position with an accuracy of less than $1 \mu$m. For a two-pixel split event, we obtained a similar position accuracy in the split direction with no improvement in the direction perpendicular to it. We will discuss the type of CCD which can achieve the subpixel resolution for the entire area of the CCD., Comment: 16pages, 5 figures. To appear in Jpn. J. Appl. Phys. March, 2001

Several shrapnels have been detected in the vicinity of Vela SNR by the ROSAT all-sky survey. We present here the spectral properties of shrapnel `A' observed with the ASCA satellite. A prominent Si-K emission line with relatively weak emission lines from other elements have been detected, revealing that the relative abundance of Si is a few ten-times higher than those of other elements. Combining with the ROSAT PSPC results, we obtained the electron temperature, $kT_{\rm e}$, to be $0.33 \pm 0.01$ keV. The total mass of shrapnel `A' is estimated to be $\sim 0.01 M_\odot$. If it is an ejecta of a supernova explosion, the interstellar matter (ISM) would be swept up in the leading edge while the ejecta material would be peeled off in the trailing edge, which should be confirmed by future observations., Comment: 19pages, 5 figures, 1 table; Accepted for Publications of the Astronomical Society of Japan

MAXI, Monitor of All-sky X-ray Image, is the X-ray observatory on the Japanese experimental module (JEM) Exposed Facility (EF) on the International Space Station (ISS). MAXI is a slit scanning camera which consists of two kinds of X-ray detectors: one is a one-dimensional position-sensitive proportional counter with a total area of $\sim 5000 cm^2$, the Gas Slit Camera (GSC), and the other is an X-ray CCD array with a total area $\sim 200 cm^2$, the Solid-state Slit Camera (SSC). The GSC subtends a field of view with an angular dimension of 1$^\circ\times 180^\circ$ while the SSC subtends a field of view with an angular dimension of 1$^\circ$ times a little less than 180$^\circ$. In the course of one station orbit, MAXI can scan almost the entire sky with a precision of 1$^\circ$ and with an X-ray energy range of 0.5-30 keV. We have developed the engineering model of CCD chips and the analogue electronics for the SSC. The energy resolution of EM CCD for Mn K$\alpha$ has a full-width at half maximum of $\simeq$ 182 eV. Readout noise is $\simeq$ 11 e^- rms., Comment: 10 pages, 4 figures Accepted for Nuclear Instruments and Method in Physics Research

We present here the results of the mapping observation of the Cygnus Loop with the Gas Imaging Spectrometer (GIS) onboard the ASCA observatory. The data covered the entire region of the Cygnus Loop. Spatial resolution of the GIS is moderate whereas the energy resolving power is much better than those used in the previous observations. The ASCA soft-band image shows the well-known shell-like feature whereas the ASCA hard-band image shows rather center-filled morphology with a hard X-ray compact source at the blow-up southern region., Comment: 4 pages, 2figures; Accepted for publication in Advances in Space Research, in Proceedings of 32nd Sci. Ass. of COSPAR

We detected an X-ray compact source inside the Cygnus Loop during the observation project of the whole Cygnus Loop with the ASCA GIS. The source intensity is 0.11 c s$^{-1}$ for GIS and 0.15 c s$^{-1}$ for SIS, which is the strongest in the ASCA band. The X-ray spectra are well fitted by a power law spectrum of a photon index of \error{-2.1}{0.1} with neutral H column of (\error{3.1}{0.6})${\rm \times 10^{21} cm^{-2}}$. Taking into account the interstellar absorption feature, this source is X-ray bright mainly above 1 keV suggesting either an AGN or a rotating neutron star. So far, we did not detect intensity variation nor coherent pulsation mainly due to the limited observation time. There are several optical bright stellar objects within the error region of the X-ray image. We carried out the optical spectroscopy for the brightest source (V=+12.6) and found it to be a G star. The follow up deep observation both in optical and in X-ray wavelengths are strongly required., Comment: Accepted for Publications of the Astronomical Society of Japan 17 pages, 3 figure