bluuebunny/crossref_metadata_2025_split huggingface dataset:
Suzaku Discovery of Hard X-Ray Pulsations from a Rotating Magnetized White Dwarf, AEAquarii
Authors: Terada Yukikatsu , Hayashi Takayuki , Ishida Manabu , Mukai Koji , Dotani Tadayasu , Okada Shunsaku , Nakamura Ryoko , Naik Sachindra , Bamba Aya , Makishima Kazuo 
Published: March 2014

Abstract
A fast rotating magnetized white dwarf, AEAquarii, was observed with Suzaku, in 2005 October–November and 2006 October with exposures of 53.1 and 42.4 ks, respectively. In addition to clear spin modulation in the 0.5–10 keV band of the XIS data at the barycentric period of 33.0769$\pm$0.0001 s, the 10–30 keV HXD data in the second half of the 2005 observation also showed statistically significant periodic signals at a consistent period. On that occasion, the spin-folded HXD light curve exhibited two sharp spikes separated by $\sim$0.2 cycles in phase, in contrast to approximately sinusoidal profiles observed at energies below $\sim$4 keV. The folded 4–10 keV XIS light curves are understood to be a superposition of those two types of pulse profiles. The phase-averaged 1.5–10 keV spectra can be reproduced by two thermal components with temperatures of $2.90_{-0.16}^{+0.20}$keV and 0.53${\;}_{-0.13}^{+0.14}$keV, but the 12–25 keV HXD data show a significant excess above the extrapolated model. This excess can be explained by either a power-law model with a photon index of $1.12_{-0.62}^{+0.63}$ or a third thermal component with a temperature of 54${\;}_{-47}^{+26}$keV. At a distance of 102 pc, the 4–30 keV luminosities of the thermal and the additional components become $1.7_{-0.6}^{+1.3}$ and 5.3${\;}_{-0.3}^{+15.3}$$\times10^{29}$ergs$^{-1}$, respectively. The latter corresponds to 0.09% of the spin-down energy of the object. Possible emission mechanisms of the hard pulsations are discussed, including non-thermal ones, in particular.
A Possible Spin-Orbit Misalignment in the Transiting Eccentric Planet HD 17156b
Authors: Narita Norio , Sato Bun’ei , Ohshima Osamu , Winn Joshua N. 
Published: March 2014

Abstract
We present simultaneous photometric and spectroscopic observations of HD17156b spanning a transit on 2007 November 12 (UT). This system is of special interest because of its 21 d period (unusually long for a transiting planet) and its high orbital eccentricity of 0.67. By modeling the Rossiter–McLaughlin effect, we find the angle between the sky projections of the orbital axis and the stellar rotation axis to be $62^{\circ} \pm 25^{\circ}$. Such a large spin-orbit misalignment, as well as the high eccentricity, could be explained as a relic of a previous gravitational interaction with other planets.
Evidence for Resonance Line Scattering in the Suzaku X-Ray Spectrum of the Cygnus Loop
Authors: Miyata Emi , Masai Kuniaki , Hughes John P. 
Published: March 2014

Abstract
We present an analysis of the Suzaku observation of the northeastern rim of the Cygnus Loop supernova remnant. The high detection efficiency together with the high spectral resolution of the Suzaku X-ray CCD camera enables us to detect highly-ionized C and N emission lines from the Cygnus Loop. Given the significant plasma structure within the Suzaku field of view, we selected the softest region based on ROSAT observations. The Suzaku spectral data are well characterized by a two-component non-equilibrium ionization model with different best-fit values for both the electron temperature and ionization timescale. Abundances of C to Fe are all depleted to typically 0.23 times solar with the exception of O. The abundance of O is relatively depleted by an additional factor of two compared with other heavy elements. We found that the resonance-line-scattering optical depth for the intense resonance lines of O is significant and, whereas the optical depth for other resonance lines is not as significant, it still needs to be taken into account for accurate abundance determination.
Observational Possibility of the “Snow Line” on the Surface of
Circumstellar Disks with the Scattered Light
Authors: Inoue Akio K. , Honda Mitsuhiko , Nakamoto Taishi , Oka Akinori 
Published: March 2014

Abstract
We discuss how we obtain the spatial distribution of ice on the surface of the circumstellar disk around young stars. Ice in the disks plays a very important role in various issues, for instance, on the disk structure, on planet formation, on an isotopic anomaly in meteorites, and on the origin of the oceans on Earth. Therefore, spatially resolved observations of the condensation/sublimation front of ice, the so-called snow line is strongly required. Here, we propose a new method for obtaining a spatially resolved snow line on circumstellar disks by observing a 3µ H $_2$ O ice feature in the scattered light. Based on radiative transfer considerations, we show that the feature is clearly imprinted in the spectrum of the scattered light from both optically thick and thin circumstellar disks. We also show that the scattered light and the H $_2$ O ice feature from protoplanetary disks are detectable and spatially resolvable with current instruments through an $H_{\mathit{2}}O$ narrowband filter around 3µ. Finally, we present a diagnostics of disk dust properties on $K-H_{\mathit{2}}O$ and $K-L’$ two-color diagram.
Local Analysis of Nonlinear Oscillations of Thin Accretion
Disks
Authors: Fogelström Sara , Levin Lina , Slapak Rikard 
Published: March 2014

Abstract
We calculated the coupling coefficients for non-linear, quasi-local oscillatory modes of thin accretion disks. We found that several of them are non-zero. Mode coupling is a necessary condition for a resonance, and thus our results may be relevant for the recently discussed QPO resonance model.
Radio Polarization Properties for Blazars
Authors: Fan Jun-Hui , Yuan Yu-Hai , Liu Yi , Hua Tong-Xu , Romero Gustavo E. , Zhang Yong-Wei , Su Jiang-Bo , Gupta Alok G. , Liu Hua , Huang Yong , Guo Qian , Zhang Jiang-Shui , Wang Hong-Guang , Zhang Jing-Yi , Tao Jun 
Published: March 2014

Abstract
We used data from the University of Michigan Radio Astronomy Observatory (UMRAO) at three different bands (4.8 GHz, 8 GHz, and 14.5 GHz) to calculate the radio spectral index and the averaged polarization in a sample of 92 flat spectrum radio quasars (FSRQs). We analyzed the relationship between the polarization and other physical parameters for these objects. The results show that: 1) the polarization and its variability at high radio frequencies are higher than those at lower frequencies, 2) the degree of linear polarization is correlated with the radio spectral index, suggesting that the synchrotron mechanism is responsible for the radio emission, 3) the polarization is correlated with the core-dominance parameter for those objects for which this parameter is known, which suggests that relativistic beaming could explain some polarization characteristics of FSRQs, and 4) the polarization and flux density variabilities are correlated. These results are similar to those found for RBLs in our previous work (Fan et al. 2006). However, the distributions in the averaged polarization and the spectral index in FSRQs are different from those in RBLs.
Mapping the Dust Column Density in Dark Clouds by Using NIR Scattered Light: Case of the Lupus 3 Dark Cloud
Authors: Nakajima Yasushi , Kandori Ryo , Tamura Motohide , Nagata Tetsuya , Sato Shuji , Sugitani Koji 
Published: March 2014

Abstract
We present a method of mapping the dust column density in dark clouds by using near-infrared scattered light. Our observations of the Lupus 3 dark cloud indicate that there is a well-defined relation between (1) the $H-K_{\rm s}$ color of an individual star behind the cloud, i.e., the dust column density and (2) the surface brightness of scattered light toward the star in each of the $J, H$, and $K_{\rm s}$ bands. In the relation, the surface brightnesses increase at low $H-K_{\rm s}$ colors, then saturate and decrease with increasing $H-K_{\rm s}$. Using a simple one-dimensional radiation transfer model, we derive empirical equations that plausibly represent the observed relationship between the surface brightness and the dust column density. Using the empirical equations, we estimate the dust column density of the cloud for any direction toward which even no background stars are seen. We obtain a dust column density map with a pixel scale of 2$^{\prime\prime}$.3 $\times$ 2$^{\prime\prime}$.3 and a large dynamic range of up to $A_V =$ 50 mag. Compared to previous studies by Juvela et al. (2006, A&A, 457, 877; 2008, A&A, 480, 445), this study is the first to use the color excess of background stars for calibrating the empirical relationship and to apply it beyond the point where the surface brightness starts to decrease with increasing column density.
Stellar Parameters and Elemental Abundances of Late-G Giants
Authors: Takeda Yoichi , Sato Bun’ei , Murata Daisuke 
Published: March 2014

Abstract
The properties of 322 intermediate-mass late-G giants (comprising 10 planet-host stars) selected as the targets of the Okayama Planet Search Program, many of which are red-clump giants, were comprehensively investigated by establishing their various stellar parameters (atmospheric parameters, including turbulent velocity fields, metallicity, luminosity, mass, age, projected rotational velocity, etc.), and their photospheric chemical abundances for 17 elements, in order to study their mutual dependence, connection with the existence of planets, and possible evolution-related characteristics. The metallicity distribution of planet-host giants was found to be almost the same as that of non-planet-host giants, making marked contrast to the case of planet-host dwarfs tending to be metal-rich. Generally, the metallicities of these comparatively young (typical age of $\sim 10^{9}$ yr) giants tend to be somewhat lower than those of dwarfs at the same age, and super-metal-rich ([Fe$/$H] $\gt$ 0.2) giants appear to be lacking. Apparent correlations were found between the abundances of C, O, and Na, suggesting that the surface compositions of these elements have undergone appreciable changes due to dredge-up of H-burning products by evolution-induced deep envelope mixing, which becomes more efficient for higher mass stars.
A Synchronized Variation of the 6.7GHz Methanol Maser in Cepheus A
Authors: Sugiyama Koichiro , Fujisawa Kenta , Doi Akihiro , Honma Mareki , Isono Yasuko , Kobayashi Hideyuki , Mochizuki Nanako , Murata Yasuhiro 
Published: March 2014

Abstract
We present the results of monitoring observations of a 6.7GHz methanol maser in Cepheus A (Cep A) using the Yamaguchi 32m radio telescope and of imaging observations conducted with the JVN (Japanese VLBI Network). We identified five spectral features, which are grouped into two groupes: redshifted ($-$1.9 and $-$2.7kms$^{-1}$) and blueshifted ($-$3.8, $-$4.2, and $-$4.9kms$^{-1}$). We detected rapid variabilities in these maser features within a monitoring period of 81d. The redshifted features decreased in flux density to 50% of the initial value, while the blueshifted ones rapidly increased within 30d. The time variation in these maser features had two remarkable properties: synchronization and negative correlation between the redshifted and the blueshifted. Based on the JVN observations, we found that the maser spots were associated with the CepAHW2 object and had an arched structure with a scale of $\sim$1400AU; also, separations of the five maser features were found to be larger than 100AU. These properties of the masers, namely, the synchronization of the flux variation and the spectral and spatial isolations of the features, suggest that collisional excitation by a shock wave from a common exciting source is unlikely to happen. Instead, the synchronized time variation of the masers can be explained if all of the maser features are excited by infrared radiation from the dust that is heated by a common exciting source with a rapid variability.
VLBI Astrometry of AGB Variables with VERA — A Semiregular Variable S Crateris—
Authors: Nakagawa Akiharu , Tsushima Miyuki , Ando Kazuma , Bushimata Takeshi , Choi Yoon Kyung , Hirota Tomoya , Honma Mareki , Imai Hiroshi , Iwadate Kenzaburo , Jike Takaaki , Kameno Seiji , Kameya Osamu , Kamohara Ryuichi , Kan-Ya Yukitoshi , Kawaguchi Noriyuki , Kijima Masachika , Kim Mi Kyoung , Kobayashi Hideyuki , Kuji Seisuke , Kurayama Tomoharu , Maeda Toshihisa , Manabe Seiji , Maruyama Kenta , Matsui Makoto , Matsumoto Naoko , Miyaji Takeshi , Nagayama Takumi , Nakamura Kayoko , Nyu Daisuke , Oh Chung Sik , Omodaka Toshihiro , Oyama Tomoaki , Pradel Nicolas , Sakai Satoshi , Sasao Tetsuo , Sato Katsuhisa , Sato Mayumi , Shibata Katsunori M. , Suda Hiroshi , Tamura Yoshiaki , Ueda Kousuke , Ueno Yuji , Yamashita Kazuyoshi 
Published: March 2014

Abstract
We present a distance measurement for the semiregular variable S Crateris (S Crt) based on its annual parallax. With the unique dual beam system of the VLBI Exploration for Radio Astrometry (VERA) telescopes, we measured the absolute proper motion of a water maser spot associated with S Crt, referred to the quasar J1147$-$0724 located at an angular separation of 1.23D. In observations spanning nearly two years, we detected the maser spot at an LSR velocity of 34.7kms$^{-1}$, for which we measured an annual parallax of 2.33$\pm$0.13mas, corresponding to a distance of 430$^{+25}_{-23}$pc. This measurement has an accuracy one order of magnitude better than the parallax measurements of HIPPARCOS. The angular distribution and three-dimensional velocity field of maser spots indicate a bipolar outflow with the flow axis along the northeast-southwest direction. Using the distance and photospheric temperature, we estimated the stellar radius of S Crt and compared it with those of Mira variables.
Stellar Abundances for the Galactic Archeology (SAGA) Database — Compilation of the Characteristics of Known Extremely Metal-Poor Stars
Authors: Suda Takuma , Katsuta Yutaka , Yamada Shimako , Suwa Tamon , Ishizuka Chikako , Komiya Yutaka , Sorai Kazuo , Aikawa Masayuki , Fujimoto Masayuki Y. 
Published: March 2014

Abstract
We describe the construction of a database of extremely metal-poor (EMP) stars in the Galaxy. Our database contains detailed elemental abundances, reported equivalent widths, atmospheric parameters, photometry, and binarity status, compiled from papers in the literature that report on studies of EMP halo stars with [Fe/H]$\;\le\;$$-$2.5. The compilation procedures for this database were designed to assemble data effectively from electronic tables available from online journals. We have also developed a data retrieval system that enables data searches by various criteria and illustrations to explore relationships between stored variables. Currently, our sample includes 1212 unique stars (many of which are studied by more than one group) with more than 15000 individual reported elemental abundances, covering relevant papers published by 2007 December. We discuss the global characteristics of the present database, as revealed by the EMP stars observed to date. For stars with [Fe/H]$\;\le\;$$-$2.5, the number of giants with reported abundances is larger than that of dwarfs by a factor of two. The fraction of carbon-rich stars (among the sample for which the carbon abundance is reported) amounts to $\sim\;$30% for [Fe/H]$\;\le\;$$-$2.5. We find that known binaries exhibit different distributions of the orbital period, according to whether they are giants or dwarfs, and also as a function of the metallicity, although the total sample of such stars is still quite small.
Optical Spectroscopic Observations of Comet 73P/Schwassmann-Wachmann 3
Authors: Kanda Yu-ichi , Mori Atsushi , Kobayashi Hitomi , Kawakita Hideyo 
Published: March 2014

Abstract
Comet 73P/Schwasmann-Wachmann 3 (hereafter SW3) is known as a split comet, and its fragments are the best targets to investigate the homogeneity of a cometary nucleus. We conducted optical low-dispersion spectroscopic observations of the brightest fragments, B and C, of comet SW3 with the NAYUTA telescope in 2006 early May, in the vicinity of the closest approach to Earth on 2006 May 12, UT. We report on the chemical compositions of these fragments. Both fragments are similar to each other in composition, and are significantly depleted in C$_2$ compared with other comets.
Astrometry of H2O Masers in Nearby Star-Forming Regions with VERA III. IRAS22198+6336 in Lynds1204G
Authors: Hirota Tomoya , Ando Kazuma , Bushimata Takeshi , Choi Yoon Kyung , Honma Mareki , Imai Hiroshi , Iwadate Kenzaburo , Jike Takaaki , Kameno Seiji , Kameya Osamu , Kamohara Ryuichi , Kan-ya Yukitoshi , Kawaguchi Noriyuki , Kijima Masachika , Kyoung Kim Mi , Kobayashi Hideyuki , Kuji Seisuke , Kurayama Tomoharu , Manabe Seiji , Matsui Makoto , Matsumoto Naoko , Miyaji Takeshi , Miyazaki Atsushi , Nagayama Takumi , Nakagawa Akiharu , Namikawa Daichi , Nyu Daisuke , Sik Oh Chung , Omodaka Toshihiro , Oyama Tomoaki , Sakai Satoshi , Sasao Tetsuo , Sato Katsuhisa , Sato Mayumi , Shibata Katsunori M. , Tamura Yoshiaki , Ueda Kosuke , Yamashita Kazuyoshi 
Published: March 2014

Abstract
We present results of multi-epoch VLBI observations with VERA (VLBI Exploration of Radio Astrometry) of the 22GHz H$_{2}$O masers associated with a young stellar object (YSO) IRAS22198$+$6336 in a dark cloud, L1204G. Based on phase-referencing VLBI astrometry, we derived an annual parallax of IRAS22198$+$6336 to be 1.309$\pm$0.047mas, corresponding to the distance of 764$\pm$27pc from the Sun. Although the most principal error source of our astrometry is attributed to the internal structure of the maser spots, we successfully reduced the errors in the derived annual parallax by employing position measurements for all of the 26 detected maser spots. Based on this result, we reanalyzed the spectral energy distribution of IRAS22198$+$6336 and found that the bolometric luminosity and total mass of IRAS22198$+$6336 are 450$L_{\odot}$ and 7$M_{\odot}$, respectively. These values are consistent with an intermediate-mass YSO deeply embedded in the dense dust core, which has been proposed to be an intermediate-mass counterpart of a low-mass Class 0 source. In addition, we obtained absolute proper motions of the H$_{2}$O masers for the most blue-shifted components. We propose that the collimated jets aligned along the east-west direction are the most plausible explanation for the origin of the detected maser features.
Rare CO Isotope Observations of M51a (NGC5194)
Authors: Vila-Vilaró Baltasar 
Published: March 2014

Abstract
We present observations of the central regions of M51a (NGC5194) in the $J=$ 1-0 rotational transitions of $^{13}$CO, C$^{18}$O, and C$^{17}$O. The last two are the first detections reported for this object. We have combined these data with published HCN and CO($J=$ 1-0) observations with the same telescope to carry out some LVG modeling (single-cloud and two-cloud mixtures) of the line ratios. The results are compatible with the presence of a region emitting most of the HCN and another component at lower temperatures and densities emitting most of the rest of the molecular emission. The observed high C$^{18}$O$/$C$^{17}$O ratio, together with our models, suggest that this is caused by an underabundance of [C$^{17}$O] (compared with Galactic values). This can be explained by different evolutionary histories. The C$^{18}$O emission line has a clearly asymmetric profile, implying the presence of significant excitation differences within the observed region. Finally, there is an indication that the CO(1-0) is overestimating the molecular gas mass in the central kpc of this galaxy. This is similar to what is found in the Milky Way at similar spatial scales, and possibly associated with a change in the conversion factor due to the average cloud properties in the central regions of this object.
XMM-Newton Observations of NGC 4051: Temporal Flux and Spectral Variability during Transition to the Faintest Phase in NGC 4051
Authors: Haba Yoshito , Liebmann Andrew C. , Fukumura Keigo , Kunieda Hideyo , Tsuruta Sachiko 
Published: March 2014

Abstract
We report on the results from temporal and spectral analyses of NGC 4051 observed with XMM-Newton. The X-ray variabilities in the higher-flux states are well explained by the combination of a variable, direct power law and a temporally stable, absorbed component. In low-flux states, however, spectral variations are mainly due to flux changes of the absorbed component. Furthermore, when the source enters into the lowest-flux state, the absorbed component no longer appears. One promising interpretation is that part of the central emission region is covered by a temporally stable material, while the size of the emission region varies so as to produce a flux variation predominantly in direct power-law component. Once the emission region becomes smaller than the size of the absorber, however, the absorbed flux also begins to decrease. Finally, when the emission region is reduced sufficiently, both the direct and absorbed components disappear (i.e., “switched off” state). In this state, we found the signature of thermal emission, whose temperature of 0.8keV is in agreement with the average value obtained from statistical analyses of Seyfert 2 galaxies with starburst activity. This could suggest that NGC 4051 possesses a nuclear starburst region.
Performance of the Charge-Injection Capability of Suzaku XIS
Authors: Nakajima Hiroshi , Yamaguchi Hiroya , Matsumoto Hironori , Tsuru Takeshi Go , Koyama Katsuji , Tsunemi Hiroshi , Hayashida Kiyoshi , Torii Ken'ichi , Namiki Masaaki , Katsuda Satoru , Shoji Masayuki , Matsuura Daisuke , Miyauchi Tomofumi , Dotani Tadayasu , Ozaki Masanobu , Murakami Hiroshi , Bautz Mark W. , Kissel Steve E. , LaMarr Beverly , Prigozhin Gregory Y. 
Published: March 2014

Abstract
A charge-injection technique is applied to the X-ray CCD camera, XIS (X-ray Imaging Spectrometer) aboard Suzaku. The charge transfer inefficiency (CTI) in each CCD column (vertical transfer channel) is measured by the injection of charge packets into a transfer channel and subsequent readout. This paper reports on the performances of the charge-injection capability based on the ground experiments using a radiation-damaged device, and in-orbit measurements of the XIS. The ground experiments show that charges are stably injected with a dispersion of 91eV in FWHM in a specific column for the charges equivalent to an X-ray energy of 5.1keV. This dispersion width is significantly smaller than that of the X-ray events of 113eV (FWHM) at approximately the same energy. The amount of charge loss during transfer in a specific column, which is measured with the charge-injection capability, is consistent with that measured with the calibration source. These results indicate that the charge-injection technique can accurately measure column-dependent charge losses, rather than the calibration sources. The column-to-column CTI correction to the calibration source spectra significantly reduces the line widths compared to those with a column-averaged CTI correction (from 193eV to 173eV in FWHM on an average at the time of one year after the launch). In addition, this method significantly reduces the low-energy tail in the line profile of the calibration source spectrum.