bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suzaku Observation of the Metallicity Distribution in the Elliptical Galaxy NGC 4636
Authors: Hayashi Katsuhiro , Fukazawa Yasushi , Tozuka Miyako , Nishino Sho , Matsushita Kyoko , Takei Yoh , Arnaud Keith A. 
Published: March 2014

Abstract
NGC 4636, an X-ray bright elliptical galaxy, was observed for 70 ks with Suzaku. Thanks to low background and good energy resolution of the XIS, we succeeded to estimate the foreground Galactic emission accurately, and, for the first time, measure the metal abundance distributions out to $\sim $28${}^\prime$ ($\simeq $140 kpc) for O, Mg, Si, and Fe. The metal abundances are as high as $\gt$1 solar within 4${}^\prime$, and decreases by $\sim $50% from the center toward the outer region. In addition, the O to Fe abundance ratio is about 0.6$\sim $1.0 solar in all analyzed regions, indicating that metal products by SNe II and SNe Ia have mixed and diffused to the outer region of the galaxy. Furthermore, comparing the O and Fe mass distributions with those of NGC 1399, we found the metal mass-to-light ratio (MLR) of NGC 4636 to be 2–3 times larger. Therefore, the metal distributions in NGC 4636 are less extended than those in NGC 1399, possibly due to environmental factors, such as frequency of galaxy interaction. We also found that MLRs of NGC 4636 at 0.1$ r_{180}$ are $\sim $5-times smaller than those of clusters of galaxies, possibly consistent with the correlation between temperature and MLR of other spherically symmetric groups of galaxies. We also confirmed a signature of the resonance scattering of the Fe xvii line in the central region, as reported based on the XMM-Newton RGS observation.
Resonant Excitation of Disk Oscillations in Two-Armed-Deformed Disks and Application to High-Frequency QPOs
Authors: Kato Shoji 
Published: March 2014

Abstract
In previous papers we showed that in one-armed deformed disks, p-mode and g-mode oscillations are resonantly excited by horizontal resonance, and applied it to high-frequency quasi-periodic oscillations (QPOs) observed in low-mass X-ray binaries. In that model, the observed time variation of kHz QPOs is regarded as being the result of a time-dependent precession of the deformation. In this paper we consider another possible cause of the time variation of kHz QPOs. That is, we demonstrate that in two-armed deformed disks, p-mode and g-mode oscillations are excited by a vertical resonance, not by a horizontal resonance (horizontal resonance dampens them). Furthermore, we show that in the case of a vertical resonance, the frequencies of excited disk oscillations can vary with time if the vertical disk structure changes with time. A brief application of these results to the time variation of observed kHz QPOs is discussed.
Secular Increase of the Astronomical Unit: a Possible Explanation in Terms of the Total Angular-Momentum Conservation Law
Authors: Miura Takaho , Arakida Hideyoshi , Kasai Masumi , Kuramata Shuichi 
Published: March 2014

Abstract
We give an idea and order-of-magnitude estimations to explain a recently reported secular increase of the Astronomical Unit ($AU$) by Krasinsky and Brumberg (2004, Celest. Mech. Dyn. Astron., 90, 267). The idea proposed is analogous to tidal acceleration in the Earth–Moon system, which is based on conservation of the total angular momentum; we apply this scenario to the Sun–planets system. Assuming the existence of some tidal interactions that transfer the rotational angular momentum of the Sun, and using a reported value of the positive secular trend in the Astronomical Unit, $\displaystyle\frac{d}{dt}{AU}$$=$ 15$ \pm $4 (m cy$^{-1}$), the suggested change in the period of rotation of the Sun is about 21 ms cy$^{-1}$ in the case that the orbits of the eight planets have the same “expansion rate.” This value is sufficiently small, and at present it seems there are no observational data that exclude this possibility. The effects of a change in the Sun’s moment of inertia is also investigated. It is pointed out that a change in the moment of inertia due to radiative mass loss by the Sun may be responsible for the secular increase of $AU$, if orbital “expansion” is happening only in the inner-planets system. Although the existence of some tidal interactions is assumed between the Sun and the planets, concrete mechanisms of angular-momentum transfer are not discussed in this paper, which remain to be pursued as future investigations.
Spectral Analyses of the Nearest Persistent Ultraluminous X-Ray Source M 33 X-8
Authors: Weng Shan-Shan , Wang Jun-Xian , Gu Wei-Min , Lu Ju-Fu 
Published: March 2014

Abstract
We provide a detailed analysis of 12 XMM observations of the nearest persistent extragalactic ultraluminous X-ray source (ULX), M33 X-8. No significant spectral evolution has been detected for the period of the observations, and therefore we combine the individual observations to increase the signal-to-noise ratio for a spectral fitting. The combined spectra are best fitted by a self-consistent $p$-free disk plus power-law component model with $p$$=$ 0.571$_{-0.030}^{+0.032}$, $kT_{\rm in}$ (inner disk temperature) $=$ 1.38$_{-0.08}^{+0.09}$ keV, and the flux ratio of the $p$-free disk component to the power-law component being 0.63 : 0.37 in the 0.3–10 keV band. The fitting indicates that the black hole in M 33 X-8 is of $\sim $10$ M_{\rm\odot}$, and accretes at a super-Eddington rate ($\sim $1.5$ L_{\rm Edd}$); also, the phase of the accretion disk is close to that of a slim disk ($p$$=$ 0.5). We report, for the first time, that an extra power-law component is required in addition to the $p$-free disk model for ULXs. In super-Eddington cases, the power-law component may possibly result from an optically thin inner region of the disk or a Comptonized corona, similar to that of a standard thin disk.
Advection-Dominated Accretion Disks: Geometrically Slim or Thick?
Authors: Gu Wei-Min , Xue Li , Liu Tong , Lu Ju-Fu 
Published: March 2014

Abstract
We revisit the vertical structure of black-hole accretion disks in spherical coordinates. By comparing the advective cooling with the viscous heating, we show that advection-dominated disks are geometrically thick, i.e., with a half-opening angle of $\Delta\theta$$&gt;$ 2$\pi/$5, rather than being slim, as supposed previously in the literature.
Suzaku Observations across the Cygnus Loop from the Northeastern to the Southwestern Rim
Authors: Kimura Masashi , Tsunemi Hiroshi , Katsuda Satoru , Uchida Hiroyuki 
Published: March 2014

Abstract
We have observed the Cygnus Loop from the northeast (NE) rim to the southwest (SW) rim using Suzaku in 10 pointings just north of previous XMM-Newton observations. The observation data obtained were divided into 45 rectangular regions where the width was configured so that each region would hold 8000–12000 photons. The spectrum acquired from each region was fitted either with one-$kT_{\rm e}$-component non-equilibrium ionization (NEI) model or with a two-$kT_{\rm e}$-component NEI model. The two-$kT_{\rm e}$-component model yielded a significantly better fit in almost all of the non-rim regions. Judging from the abundances and the flux, the high-$kT_{\rm e}$-component (0.4–0.8 keV) must be the ejecta origin, while the low-$kT_{\rm e}$-component ($\sim$0.3 keV) comes from the swept-up matter. We found that the swept-up matter shell is very thin just southwest of center of the Loop. Together with previous observations, we estimated the diameter of this thin shell region to be 1$^{\circ}$. We also found that the ejecta distributions were asymmetric to the geometric center: the ejecta of O, Ne, and Mg were distributed more in the NE, while the ejecta of Si and Fe were distributed more in the SW of the Cygnus Loop. We calculated the masses for various metals and estimated the origin of the Cygnus Loop as the a 12–15$\,M_\odot$ core-collapse explosion.
Modeling and Reproducibility of Suzaku HXD PIN/GSO Background
Authors: Fukazawa Yasushi , Mizuno Tsunefumi , Watanabe Shin , Kokubun Motohide , Takahashi Hiromitsu , Kawano Naomi , Nishino Sho , Sasada Mahito , Shirai Hirohisa , Takahashi Takuya , Umeki Yudai , Yamasaki Tomonori , Yasuda Tomonori , Bamba Aya , Ohno Masanori , Takahashi Tadayuki , Ushio Masayoshi , Enoto Teruaki , Kitaguchi Takao , Makishima Kazuhiro , Nakazawa Kazuo , Uehara Yuichi , Yamada Shin’ya , Yuasa Takayuki , Isobe Naoki , Kawaharada Madoka , Tanaka Takaaki , Tashiro Makoto S. , Terada Yukikatsu , Yamaoka Kazutaka 
Published: March 2014

Abstract
Suzaku Hard X-ray Detector (HXD) achieved the lowest background level than any other previously or currently operational missions sensitive in the energy range of 10–600 keV, by utilizing PIN photodiodes and GSO scintillators mounted in BGO active shields to reject particle background and Compton-scattered events as much as possible. Because it does not have an imaging capability nor rocking mode for the background monitor, the sensitivity is limited by the reproducibility of the non X-ray background (NXB) model. We modeled the HXD NXB, which varies with time as well as other satellites with a low-Earth orbit, by utilizing several parameters, including particle monitor counts and satellite orbital/attitude information. The model background is supplied as an event file in which the background events are generated by random numbers, and can be analyzed in the same way as the real data. The reproducibility of the NXB model depends on the event selection criteria (such as cut-off rigidity and energy band) and the integration time, and the 1$\sigma$ systematic error is estimated to be less than 3% (PIN 15–40 keV) and 1% (GSO 50–100 keV) for more than 10 ks exposure.
Design and In-Orbit Performance of the Suzaku Wide-Band All-Sky Monitor
Authors: Yamaoka Kazutaka , Endo Akira , Enoto Teruaki , Fukazawa Yasushi , Hara Ryuji , Hanabata Yoshitaka , Hong Soojing , Kamae Tsuneyoshi , Kira Chie , Kodaka Natsuki , Kokubun Motohide , Maeno Shouta , Makishima Kazuo , Miyawaki Ryohei , Morigami Kouichi , Murakami Toshio , Nakagawa Yujin E. , Nakazawa Kazuhiro , Ohmori Norisuke , Ohno Masanori , Onda Kaori , Sato Goro , Sonoda Eri , Sugita Satoshi , Suzuki Masanobu , Suzuki Motoko , Tajima Hiroyasu , Takahashi Tadayuki , Takahashi Takuya , Tanaka Hiroki , Tamagawa Tohru , Tashiro Makoto S. , Terada Yukikatsu , Uehara Takeshi , Urata Yuji , Yamauchi Makoto , Yoshida Atsumasa , Hurley Kevin , Pal’shin Valentin , Sakamoto Takanori , Cummings Jay 
Published: March 2014

Abstract
The Suzaku Wide-band All-sky Monitor (WAM) consists of thick BGO anti-coincidence shields of the Hard X-ray Detectors (HXD). It views about half of the sky and has a geometrical area of 800 cm$^2$ per sdide and an effective area of 400 cm$^2$, even at 1 MeV. Hence, the WAM can provide unique opportunities to detect high-energy emission from GRBs and solar flares in the sub-MeV to MeV range. The WAM has detected more than 400 GRBs and 100 solar flares since its launch. This paper describes the in-flight performance of the HXD/WAM during the initial two years of operations, including the in-flight energy response, spectral and timing capabilities, and in-orbit background.
Deconvolution of Images Taken with the Suzaku X-Ray Imaging Spectrometer
Authors: Sugizaki Mutsumi , Kamae Tuneyoshi , Maeda Yoshitomo 
Published: March 2014

Abstract
We present a non-iterative method to deconvolve the point spread function (PSF) from images taken with the Suzaku X-ray Imaging Spectrometer (XIS). The method is optimized for analyses of extended sources with high photon statistics. Suzaku has four XIS detectors, each with its own X-ray CCD and X-Ray Telescope (XRT), and has been providing opportunities in spatially-resolved analyses of extended objects. The detectors, however, suffer from broad and position-dependent PSFs with their typical half-power diameter (HPD) of $\sim$110$^{\prime\prime}$. The present method is intended to recover spatial resolution to $\sim$15$^{\prime\prime}$ over a dynamic range of around 1:100 in the brightness without assuming any source model. Our deconvolution proceeds in two steps: An XIS image is multiplied by the inverse response matrix, calculated from its PSF after rebinning CCD pixels to larger-size tiles (typically 6$^{\prime\prime}$$\times$ 6$^{\prime\prime}$). The inverted image is then adaptively smoothed. The PSF is modeled on a ray-tracing program and an observed point-source image. The method has been applied to images of Centaurus A, PSR B1509$-$58 and RCW 89 taken by one XIS (XIS 1). The results have been compared with images taken with Chandra to conclude that the spatial resolution has been recovered to $\sim$20$^{\prime\prime}$ down to regions where the surface brightness is about 1:50 of the brightest tile. We believe the spatial resolution and the dynamic range can be improved with higher fidelity PSF modeling and higher precision pointing information.
A New Set of Variables in the Three-Body Problem
Authors: Kuwabara Kenji Hiro , Tanikawa Kiyotaka 
Published: March 2014

Abstract
We propose a set of variables of the general three-body problem both for two-dimensional and three-dimensional cases. The variables are ($\lambda, \theta, \Lambda, \Theta, k, \omega$), or equivalently ($\lambda, \theta, L, \dot{I},k,\omega)$ for the two-dimensional problem, and ($\lambda, \theta, L, \dot{I}, k, \omega, \phi, \psi$) for the three-dimensional problem. Here, ($\lambda, \theta$) and ($\Lambda, \Theta)$ specify the positions in the shape spheres in the configuration and momentum spaces, $k$ is the virial ratio, $L$ is the total angular momentum, $\dot{I}$ is the time derivative of the moment of inertia, and $\omega, \phi$, and $\psi$ are the Euler angles to bring the momentum triangle from the nominal position to a given position. This set of variables defines a shape space  of the three-body problem. This is also used as an initial-condition space. The initial condition of the so-called free-fall three-body problem is ($\lambda, \theta, k =$ 0, $L =$ 0, $\dot{I} =$ 0, $\omega =$ 0). We show that the hyper-surface $\dot{I} =$ 0 is a global surface of section.
Suzaku Constraints on Soft and Hard Excess Emissions from Abell 2199
Authors: Kawaharada Madoka , Makishima Kazuo , Kitaguchi Takao , Okuyama Sho , Nakazawa Kazuhiro , Fukazawa Yasushi 
Published: March 2014

Abstract
The nearby ($z =$ 0.03015) cluster of galaxies Abell 2199 was observed by Suzaku in X-rays, with five pointings for $\sim$ 20 ks each. From the XIS data, the temperature and metal abundance profiles were derived out to $\sim$ 700 kpc (0.4 times the virial radius). Both of these quantities decrease gradually from the center to peripheries by a factor of $\sim$ 2, while the oxygen abundance tends to be flat. The temperature within 12${}^\prime$ ($\sim$ 430 kpc) is $\sim$ 4 keV, and the 0.5–10 keV X-ray luminosity integrated up to 30${}^\prime$ is (2.9$\pm$0.1) $\times$ 10$^{44}$erg s$^{-1}$, in agreement with previous XMM-Newton measurements. Above this thermal emission, no significant excess was found either in the XIS range below $\sim$ 1 keV, or in the HXD-PIN range above $\sim$ 15 keV. The 90%-confidence upper limit on the emission measure of an assumed 0.2 keV warm gas is (3.7–7.5) $\times$ 10$^{62}$cm$^{-3}$arcmin$^{-2}$, which is 3.7–7.6 times tighter than the detection reported with XMM-Newton. The 90%-confidence upper limit on the 20–80 keV luminosity of any power-law component is 1.8 $\times$ 10$^{43}$erg s$^{-1}$, assuming a photon index of 2.0. Although this upper limit does not reject the possible 2.1$\sigma$ detection by the BeppoSAX PDS, it is a factor of 2.1 tighter than that of the PDS if both are considered upper limits. The non-detection of the hard excess can be reconciled with the upper limit on diffuse radio emission, without invoking very low magnetic fields ($&lt;$ 0.073$\mu$G) which were suggested previously.
A Study of Three-Dimensional Kinematics of the Narrow-Line Region of the Seyfert Galaxy NGC 4151 Based on Integral Field Spectroscopy
Authors: Shimono Atsushi , Sugai Hajime , Kawai Atsushi , Matsubayashi Kazuya , Ohtani Hiroshi , Ozaki Shinobu , Hattori Takashi , Kosugi George 
Published: March 2014

Abstract
By using the Integral Field Spectroscopy mode of the Kyoto Tri-dimensional Spectrograph II we have mapped the two-dimensional distribution of kinematics in a wide variety of emission lines in the narrow-line region of NGC 4151. We decomposed the emission lines and defined two components: a narrow component and a broad component. The narrow component has smaller FWHM values, and is spatially more extended than the broad component. We applied a simple model to each component, a rotation in the galactic plane for the narrow component and a biconical outflow model for the broad one. The two-dimensional velocity distributions of the narrow component was well-fitted to a normal rotation in the galactic plane, with the best-fit parameters being similar among the emission lines. We found that the residual maps show similar large positive values at a knot around 6$^{\prime\prime}$ southwest form the nucleus. For the central region, excluding the knot, the velocity field was fitted better, and the residual was small as the relative wavelength-calibration accuracy of the instrument among lenslets. We modeled the broad component with a simple biconical outflow axisymmetrical with respect to its axis by assuming a constant outflowing velocity, a constant FWHM value, and the emission line strength declining according to a power law with the distance from the nucleus. The best-fit model suggests that PA for the axis of the biconical outflow is close to the direction of the [O III] line emission elongation. Our line of sight was included within the outflowing bicone, which had filled cones.
Probing the Peculiar Behavior of GRS 1915$+$105 at Near-Eddington Luminosity
Authors: Vierdayanti Kiki , Mineshige Shin , Ueda Yoshihiro 
Published: March 2014

Abstract
To understand the nature of supercritical accretion, we systematically analyzed the RXTE/PCA data of GRS 1915$+$105 in its quasi-steady states, by choosing data with small variability during 1999–2000. We applied a multicolor disk plus a thermal Comptonization model, and took into consideration accurate interstellar absorption, a reflection component (with an iron-K emission line), and absorption features from the disk wind self-consistently. The total luminosity ranges from $\sim $0.2$L_{\rm E}$ to slightly above $L_{\rm E}$. There is a strong correlation between the inner disk temperature and the fraction of the disk component. Most of the Comptonization-dominated ($\gt$50% total flux) spectra show $T_{\rm in} \sim $ 1 keV with a high electron temperature of $\gt$10 keV, which may correspond to the very high state in canonical black hole X-ray binaries (BHBs). In contrast, the disk-dominated spectra have $T_{\rm in} \sim $ 2 keV with a low temperature ($&lt;$10 keV) and optically thick Comptonization, and show two separate branches in the luminosity vs. innermost temperature ($L$–$T_{\rm in}$) diagram. The lower branch clearly follows the $L \propto T_{\rm in}^4$-track. Furthermore, by applying the extended disk blackbody (or $p$-free disk) model, we found that 9 out of 12 datasets with disk luminosity above 0.3$L_{\rm E}$ prefer a flatter temperature gradient than that in the standard disk ($p &lt;$ 0.7). We interpret that, in the lower branch, the disk extends down to the innermost stable circular orbit, and the source is most probably in the slim-disk state. A rapidly spinning black hole can explain both the lack of the $L \propto T_{\rm in}^2$-track and a high value of the spectral hardening factor ($\sim $4) that would be required for a non-rotating black hole. The spectra in the upper branch are consistent with the picture of a truncated disk with low-temperature Comptonization. This state was uniquely observed from GRS 1915$+$105 among BHBs, which may be present at near-Eddington luminosity.
Dense and Warm Molecular Gas and Warm Dust in Nearby Galaxies
Authors: Matsushita Satoki , Kawabe Ryohei , Kohno Kotaro , Tosaki Tomoka , Vila-Vilaró Baltasar 
Published: March 2014

Abstract
We performed $^{12}$CO (1–0), $^{13}$CO (1–0), and HCN (1–0) single-dish observations (beam size $\sim $14–18) toward nearby starburst and non-starburst galaxies using the Nobeyama 45-m telescope. The $^{13}$CO (1–0) and HCN (1–0) emissions were detected from all seven starburst galaxies, with the intensities of both lines being similar (i.e., the ratios are around unity). On the other hand, for the case of non-starburst galaxies, $^{13}$CO (1–0) emission was detected from all three galaxies, while HCN (1–0) emission was weak, or not detected in past observations. This result indicates that the HCN$/{}^{13}$CO intensity ratios are significantly larger ($\sim $1.15$ \pm $0.32) in the starburst galaxy samples than the non-starburst galaxy samples ($\lt$ 0.31$ \pm $0.14). The large-velocity-gradient model suggests that the molecular gas in the starburst galaxies has warmer and denser conditions than that in the non-starburst galaxies, and the photon-dominated-region model suggests that denser molecular gas is irradiated by a stronger interstellar radiation field in starburst galaxies than that in non-starburst galaxies. In addition, HCN$/{}^{13}$CO ratios in our sample galaxies exhibit strong correlations with the IRAS 25$ \mu$m flux ratios. It is a well-established fact that there exists a strong correlation between dense molecular gas and star-formation activities, but our results suggest that the molecular gas temperature is also an important parameter.
Discovery of K-Shell Emission Lines of Neutral Atoms in the Galactic Center Region
Authors: Nobukawa Masayoshi , Koyama Katsuji , Tsuru Takeshi Go , Ryu Syukyo G. , Tatischeff Vincent 
Published: March 2014

Abstract
The K-shell emission line of neutral iron from the Galactic center (GC) region is one of the keys concerning the structure and activity of the GC. The origin is still an open question, but possibly due either to X-ray radiation or to electron bombarding to neutral atoms. To address this issue, we analyzed the Suzaku X-ray spectrum from the GC region of intense neutral iron line emission, and report on the discovery of K$\alpha$ lines of neutral argon, calcium, chrome, and manganese atoms. The equivalent widths of these K$\alpha$ lines indicate that the metal abundances in the GC region should be $\sim $1.6 and $\sim $4 of the solar value, depending on the X-ray and electron origins, respectively. On the other hand, the metal abundances in the hot plasma in the GC region are found to be $\sim $1–2 solar. These results favor that the origin of the neutral K$\alpha$ lines is due to X-ray irradiation.
Evidence of Early Enrichment of the Galactic Disk by Large-Scale Winds
Authors: Tsujimoto Takuji , Bland-Hawthorn Joss , Freeman Kenneth C. 
Published: March 2014

Abstract
Large-scale homogeneous surveys of Galactic stars may indicate that the elemental abundance gradient evolves with cosmic time, which is a phenomenon that was not foreseen in existing models of Galactic chemical evolution (GCE). If this phenomenon is confirmed in future studies, we can show that this effect, at least in part, is due to large-scale winds that once enriched the disk. These set up a steep abundance gradient in the inner disk ($R_{\rm GC} \lesssim$ 14 kpc). At the close of the wind phase, chemical enrichment through accretion of metal-poor material from the halo to the disk gradually reduced the metallicity of the inner region, whereas a slight increase in the metallicity proceeded beyond the solar circle. Our “wind$+$infall” model accounts for a flattening of the abundance gradient in the inner disk, in agreement with observations. Accordingly, we propose that enrichment by large-scale winds is a crucial factor in chemical evolution in the disk. We anticipate that rapid flattening of the abundance gradient is the hallmark of disk galaxies with significant central bulges.