bluuebunny/crossref_metadata_2025 huggingface dataset:
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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Resonant Excitation of Disk Oscillations in Deformed Disks III: Revision of Mathematical Treatment
Authors: Kato Shoji
Published: March 2014

In previous studies, we have examined a resonant excitation of disk oscillations in deformed disks. In these studies, however, the mathematical treatment around the resonant points was not rigorous. In this paper the inadequate point is corrected, but with no essential changes in the final results. For this excitation process to work, disks must be general relativistic. That is, a non-monotonic radial distribution of the epicyclic frequency in relativistic disks is essential for the presence of the resonance, and for trapping oscillations. In this paper, the growth rate of resonant oscillations is expressed in a form more suitable for numerical calculations.
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

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.
Reproducibility of Non-X-Ray Background for the X-Ray Imaging Spectrometer aboard Suzaku
Authors: Tawa Noriaki , Hayashida Kiyoshi , Nagai Masaaki , Nakamoto Hajime , Tsunemi Hiroshi , Yamaguchi Hiroya , Ishisaki Yoshitaka , Miller Eric D. , Mizuno Tsunefumi , Dotani Tadayasu , Ozaki Masanobu , Katayama Haruyoshi
Published: March 2014

One of the advantages of the X-ray Imaging Spectrometer (XIS) system aboard Suzaku is its low and stable non-X-ray background (NXB). In order to make the best use of this advantage, modeling the NXB spectra with high accuracy is important to subtract them from the spectra of on-source observations. We are constructing an NXB database by collecting XIS events when the the dark Earth covers the XIS FOV. The total exposure time of the NXB data is presently about 785ks for each XIS. It is found that the count rate of the NXB anti-correlates with the cut-off-rigidity and correlates with the count rate of the PIN upper discriminator (PIN-UD) in the Hard X-ray Detector aboard Suzaku. We thus model the NXB spectrum for a given on-source observation by employing either of these parameters, and obtain a better reproducibility of the NXB for the model with PIN-UD than that with the cut-off-rigidity. The reproducibility of the NXB model with PIN-UD is 4.55-5.63% for each XIS NXB in the 1-7keV band and 2.79-4.36% for each XIS NXB in the 5-12keV band for each 5ks exposure of the NXB data. This NXB reproducibility is much smaller than the spatial fluctuation of the cosmic X-ray background in the 1-7keV band, and is almost comparable to that in the 5-12keV band.
Discovery of Extended X-Ray Emission from an Unidentified TeV Source, HESS J1614$-$518, Using the Suzaku Satellite
Authors: Matsumoto Hironori , Uchiyama Hideki , Sawada Makoto , Tsuru Takeshi G. , Koyama Katsuji , Katagiri Hideaki , Yamazaki Ryo , Bamba Aya , Kohri Kazunori , Mori Koji , Uchiyama Yasunobu
Published: March 2014

We report Suzaku results concerning HESS J1614$-$518, which is the brightest extended TeV gamma-ray source discovered in the Galactic plane survey conducted using the H.E.S.S. telescope. We discovered three X-ray objects in the field of view of the X-ray Imaging Spectrometer, which were designated as Suzaku J1614$-$5141 (src A), Suzaku J1614$-$5152 (src B), and Suzaku J1614$-$5148 (src C). Src A is an extended source located at the peak position of HESS J1614$-$518, and is therefore a plausible counterpart to HESS J1614$-$518. The X-ray flux in the 2-10keV band is 5$\times 10^{-13}$ergs$^{-1}$cm$^{-2}$, which is an order of magnitude smaller than the TeV flux. The photon index is 1.7, which is smaller than the canonical value of synchrotron emissions from high-energy electrons found in some supernova remnants. These findings present a challenge to models in which the origin of TeV emission is inverse Compton scattering of the cosmic microwave background by accelerated electrons that emit X-rays via synchrotron emission. Src B is located at a relatively dim region in the TeV band image; however, its hydrogen column density is the same as that of src A. Therefore, src B may also be physically related to HESS J1614$-$518. Src C is a foreground late-type B star. We also discovered soft extended X-ray emission near HESS J1614$-$518.
Detailed Hard X-Ray Measurements of Nuclear Emission from the Seyfert2 Galaxy NGC4388 with Suzaku
Authors: Shirai Hirohisa , Fukazawa Yasushi , Sasada Mahito , Ohno Masanori , Yonetoku Daisuke , Yokota Satoshi , Fujimoto Ryuichi , Murakami Toshio , Terashima Yuichi , Awaki Hisamitsu , Ikeda Shinya , Ozawa Midori , Tsuru Takeshi G.
Published: March 2014

We report on a Suzaku observation of the nearby Seyfert2 galaxy NGC4388. The overall spectrum is well described by the combination of strongly absorbed power-law plus thin thermal plasma emission, as well as previous observations. Thanks to well-calibrated instruments and a low background level, Suzaku measured the broad-band X-ray spectra more precisely than ever, and enabled us to probe the physical structure of the nuclear region. In addition, a time variability having a factor of 1.5 with a half-day time scale was found up to above 10keV. The center energy and the K$\beta$/K$\alpha$ ratio of the narrow Fe-K line, together with less time variability, indicate that the fluorescent material is far from the black hole. A spectral hump around the 30-40keV band, together with a Compton shoulder of the Fe-K line, requires a significant contribution of the reflection component. This is also consistent with a smaller amplitude of time variability in a higher energy band. A large contribution of the reflection component was not observed by the CGRO/OSSE and BeppoSAX, suggesting that NGC4388 had been in a higher flux state, and that Suzaku observed its light echo. A He-like Fe-K$\alpha$ absorption line was also detected, indicating the existence of highly ionized plasma.
Wide-Band Spectroscopy of the Compton Thick Seyfert2 Galaxy Markarian 3 with Suzaku
Authors: Awaki Hisamitsu , Anabuki Naohisa , Fukazawa Yasushi , Gallo Luigi C. , Ikeda Shinya , Isobe Naoki , Itoh Takeshi , Kunieda Hideyo , Makishima Kazuo , Markowitz Alex , Miniutti Giovanni , Mizuno Tsunefumi , Okajima Takashi , Ptak Andrew , Reeves James N. , Takahashi Tadayuki , Terashima Yuichi , Yaqoob Tahir
Published: March 2014

We obtained a wide-band spectrum of the Compton-thick Seyfert2 galaxy Mkn3 with Suzaku. The observed spectrum was clearly resolved into weak, soft power-law emission, a heavily absorbed power-law component, cold reflection, and many emission lines. The heavily absorbed component, absorbed by gas with a column density of 1.1$\times$10$^{24}$cm$^{-2}$, has an intrinsic 2-10keV luminosity of $\sim$1.6$\times$10$^{43}$ergs$^{-1}$, and is considered to be direct emission from the Mkn3 nucleus. The reflection component was interpreted as being the reflection of direct light off a cold, thick material; the reflection fraction, $R$, was 1.36$\pm$0.20. The cold material is inferred to be located $>$ 1 pc from the central black hole of Mkn3, due to the low ionization parameter of iron ($\xi <$ 1ergcms$^{-1}$) and the narrow iron line width ($\sigma$$<$ 22eV). The weak, soft power-law emission is considered to be scattered light by ionized gas with a scattering fraction of 0.9$\pm$0.2%. The existence of many highly ionized lines in the observed spectrum indicates that the ionized gas has a broad ionized structure, with $\xi =$ 10-1000 ergcms$^{-1}$. This high-quality spectrum obtained by Suzaku can be considered to be a template for studies of Seyfert2 galaxies.
High Metallicity of the X-Ray Gas Up to the Virial Radius of a Binary Cluster of Galaxies: Evidence of Galactic Superwinds at High-Redshift
Authors: Fujita Yutaka , Tawa Noriaki , Hayashida Kiyoshi , Takizawa Motokazu , Matsumoto Hironori , Okabe Nobuhiro , Reiprich Thomas. H.
Published: March 2014

We present an analysis of a Suzaku observation of the link region between the galaxy clusters A 399 and A 401. We obtained the metallicity of the intracluster medium (ICM) up to the cluster virial radii for the first time. We determined the metallicity where the virial radii of the two clusters cross each other ($\sim 2$ Mpc away from their centers) and found that it is comparable to that in their inner regions ($\sim 0.2\: Z_\odot$). It is unlikely that the uniformity of metallicity up to the virial radii is due to mixing caused by a cluster collision. Since the ram-pressure is too small to strip the interstellar medium of galaxies around the virial radius of a cluster, the fairly high metallicity that we found there indicates that the metals in the ICM are not transported from member galaxies by ram-pressure stripping. Instead, the uniformity suggests that the proto-cluster region was extensively polluted with metals by extremely powerful outflows (superwinds) from galaxies before the clusters formed. We also searched for the oxygen emission from the warm-hot intergalactic medium in that region and obtained a strict upper limit of the hydrogen density ($n_{\rm H}<4.1\times 10^{-5}$ cm$^{-3}$).
Spectral Evolution of GRB060904A Observed with Swift and Suzaku- Possibility of Inefficient Electron Acceleration
Authors: Yonetoku Daisuke , Tanabe Sachiko , Murakami Toshio , Emura Naomi , Aoyama Yuka , Kidamura Takashi , Kodaira Hironobu , Kodama Yoshiki , Kozaka Ryota , Nashimoto Takuro , Okuno Shinya , Yokota Satoshi , Yoshinari Satoru , Abe Keiichi , Onda Kaori , Tashiro Makoto S. , Urata Yuji , Nakagawa Yujin E. , Sugita Satoshi , Yamaoka Kazutaka , Yoshida Atsumasa , Ishimura Takuto , Kawai Nobuyuki , Shimokawabe Takashi , Kinugasa Kenzo , Kohmura Takayoshi , Kubota Kaori , Sugiyasu Kei , Ueda Yoshihiro , Masui Kensuke , Nakazawa Kazuhiro , Takahashi Tadayuki , Maeno Shouta , Sonoda Eri , Yamauchi Makoto , Kuwahara Makoto , Tamagawa Toru , Matsuura Daisuke , Suzuki Motoko , Barthelmy Scott , Gehrels Neil , Nousek John
Published: March 2014

We observed an X-ray afterglow of GRB060904A with the Swift and Suzaku satellites. We found rapid spectral softening during both the prompt tail phase and the decline phase of an X-ray flare in the Swift/BAT and Swift/XRT data. The observed spectra were fit by power-law photon indices which rapidly changed from $\Gamma =$ 1.51$^{+0.04}_{-0.03}$ to $\Gamma =$ 5.30$^{+0.69}_{-0.59}$ within a few hundred seconds. This is one of the steepest X-ray spectra ever observed, making it quite difficult to explain by simple electron-acceleration and synchrotron-radiation processes. We then applied an alternative broken power-law with exponential cutoff (BPEC) model. It is valid to consider the exponential shape is equivalent to a synchrotron cutoff. Since the spectral cutoff appears in the soft X-ray band, we conclude that the electron acceleration must be inefficient in the internal shocks of GRB060904A. These cutoff spectra suddenly disappeared at the end of the prompt tail. After that, typical afterglow spectra with $\Gamma =$ 2.0 have been continuously and preciously monitored by both Swift/XRT and Suzaku/XIS. We could successfully trace the temporal history of two characteristic break energies that have a time dependence of $\propto t^{-3}$-$t^{-4}$, while the following afterglow spectra are quite stable. This fact indicates that the emitting material of the prompt tail is due to completely different dynamics from the shallow decay component. Therefore, the emission sites of two distinct phenomena obviously differ from each other.
Low/Hard State Spectra of GRO J1655$-$40 Observed with Suzaku
Authors: Takahashi Hiromitsu , Fukazawa Yasushi , Mizuno Tsunefumi , Hirasawa Ayumi , Kitamoto Shunji , Sudoh Keisuke , Ogita Takayuki , Kubota Aya , Makishima Kazuo , Itoh Takeshi , Parmar Arvind N. , Ebisawa Ken , Naik Sachindra , Dotani Tadayasu , Kokubun Motohide , Ohnuki Kousuke , Takahashi Tadayuki , Yaqoob Tahir , Angelini Lorella , Ueda Yoshihiro , Yamaoka Kazutaka , Kotani Taro , Kawai Nobuyuki , Namiki Masaaki , Kohmura Takayoshi , Negoro Hitoshi
Published: March 2014

The Galactic black-hole binary GROJ1655$-$40, a source harboring superluminal jets, was observed with Suzaku on 2005 September 22-23. The source was detected over a broad and continuous energy range of 0.7-300keV, with an intensity of $\sim$50mCrab at 20keV. At a distance of 3.2kpc, the 0.7-300keV luminosity was $\sim$5.2$\times$10$^{36}$ergs$^{-1}$ ($\sim$0.7% of the Eddington luminosity for a 6 $M_{\odot}$ black hole). The source was in a typical low/hard state, exhibiting a power-law shaped continuum with a photon index of $\sim$1.6. During the observation, the source intensity gradually decreased by 25% at energies above $\sim$3keV, and by 35% below 2keV. This, together with the soft X-ray spectra taken with the X-ray Imaging Spectrometer (XIS), suggests the presence of an independent soft component that can be represented by emission from a cool ($\sim$0.2keV) disk. The hard X-ray spectra obtained with the Hard X-ray Detector reveal a high-energy spectral cutoff, with an $e$-folding energy of $\sim$200keV. The entire 0.7-300keV spectrum cannot be reproduced by a single thermal Comptonization model, even when considering reflection effects. Instead, the spectrum (except the soft excess) can be successfully explained by invoking two thermal-Comptonization components with different $y$-parameters. In contrast to the high/soft state spectra of this object, in which narrow iron absorption lines are detected with equivalent widths of 60-100eV, the present XIS spectra bear no such features beyond an upper-limit equivalent width of 23eV.
Albedo, Size, and Surface Characteristics of Hayabusa-2 Sample-Return Target 162173 1999 JU3 from AKARI and Subaru Observations
Authors: Hasegawa Sunao , MüLler Thomas G. , Kawakami Kyoko , Kasuga Toshihiro , Wada Takehiko , Ita Yoshifusa , Takato Naruhisa , Terada Hiroshi , Fujiyoshi Takuya , Abe Masanao
Published: March 2014

Mid-infrared observations of the Apollo-type asteroid 162173 1999 JU3 were performed in 2007 May during its close Earth approach with the AKARI space telescope and in 2007 August with the Subaru telescope. A thermophysical model analysis of the obtained data resulted in a radiometric diameter of 0.92$\pm$0.12km and a visual geometric albedo of 0.063$^{+0.020}_{-0.015}$. The geometric albedo is typical for C-type asteroids. The solutions for the thermal inertia of 1999 JU3's surface material were not as clear as for the asteroid 25143 Itokawa due to less-favorable observing conditions. But the most likely solutions are connected to high thermal inertia values, indicating that the surface is predominantly covered by boulders and bare rocks, while areas with thick dust regolith are less common.
AKARI/FIS Mapping of the ISM-Wind Bow Shock around $\alpha $ Orionis
Authors: Ueta Toshiya , Izumiura Hideyuki , Yamamura Issei , Nakada Yoshikazu , Matsuura Mikako , Ita Yoshifusa , TanabÉ Toshihiko , Fukushi Hinako , Matsunaga Noriyuki , Mito Hiroyuki
Published: March 2014

We present $10$$\times$50scan maps around an M supergiant $\alpha $ Ori at 65, 90, 140, and 160$\mu$m obtained with the AKARI Infrared Astronomy Satellite. Higher spatial resolution data with the exact analytic solution permit us to fit the de-projected shape of the stellar-wind bow shock around $\alpha $ Ori to have a stand-off distance of $4\farcm8$, position angle of 55$^{\circ}$ and inclination angle of 56$^{\circ}$. The shape of the bow shock suggests that the velocity of $\alpha $ Ori with respect to the local medium is $v_* = 40n_{\rm H}^{-1/2}$, where $n_{\rm H}$ is the hydrogen nucleus density at $\alpha $ Ori. We found that the local medium is of $n_{\rm H} =$ 1.5 to 1.9cm$^{-3}\rule[3mm]{0mm}{0mm}$ and the velocity of the local flow is at 11kms$^{-1}$ by using the most recent astrometric solutions for $\alpha $ Ori under the assumption that the medium local to $\alpha $ Ori is moving away from the Orion OB 1 association. AKARI images may also reveal a vortex ring due to instabilities on the surface of the bow shock, as demonstrated by numerical models. This research exemplifies the potential of AKARI All-Sky data as well as follow-up observations with Herschel Space Telescope and Stratospheric Observatory for Infrared Astronomy for this avenue of research in revealing the nature of the interaction between the stellar wind and the interstellar medium.
Supernova Remnants in the AKARI IRC Survey of the Large Magellanic Cloud
Authors: Seok Ji Yeon , Koo Bon-Chul , Onaka Takashi , Ita Yoshifusa , Lee Ho-Gyu , Lee Jae-Joon , Moon Dae-Sik , Sakon Itsuki , Kaneda Hidehiro , Lee Hyung Mok , Lee Myung Gyoon , Kim Sung Eun
Published: March 2014

We present a near- to mid-infared study of supernova remnants (SNRs) using the AKARI IRC Survey of the Large Magellanic Cloud (LMC). The LMC survey observed about a 10 square degree area of the LMC in five bands centered at 3, 7, 11, 15, and 24$\mu$m using the Infrared Camera (IRC) aboard AKARI. The number of SNRs in the survey area is 21, which is about a half of the known LMC SNRs. We systematically examined AKARI images and identified eight SNRs with distinguishable infrared emission. All of them were detected at $\gtrsim$10$\mu$m and some at 3 and 7$\mu$m, too. We present their AKARI images and fluxes. In the 11$/$15$\mu$m versus 15$/$24$\mu$m color-color diagram, the SNRs appear to be aligned along a modified blackbody curve, representing thermal emission from dust at temperatures of between 90 and 190K. There is a good correlation between the 24$\mu$m and X-ray fluxes of the SNRs. It was also found that there is a good correlation between the 24$\mu$m and radio fluxes even if there is no direct physical connection between them. We considered the origin of the detected mid-infrared emission in individual SNRs. We conclude that the mid-infrared emissions in five SNRs that show morphologies similar to the X-rays are dominated by thermal emission from hot dust heated by X-ray emitting plasma. Their 15$/$24$\mu$m color temperatures are generally higher than the Spitzer 24$/$70$\mu$m color temperatures, which suggests that a single-temperature dust model cannot describe the full spectral energy distribution (SED) of the SNRs. It also implies that our understanding of the full SED is essential for estimating the dust destruction rate of grains by SNR shocks.
Discovery of the Inner Ring around PSR B1509$-$58
Authors: Yatsu Yoichi , Kawai Nobuyuki , Shibata Shinpei , Brinkmann Wolfgang
Published: March 2014

A Chandra study of a pulsar wind nebula around the young energetic pulsar PSR B1509$-$58 is presented. A high-resolution X-ray image with a total exposure time of 190 ks reveals a ringlike feature $10^{\prime\prime}$ apart from the pulsar. This feature is analogous to the inner ring seen in the Crab nebula, and thus may correspond to wind termination shock. The shock radius enables us to constrain the wind magnetization, $\sigma$$\geq$ 0.01, which is one order of magnitude larger than that of the Crab nebula. In the vicinity of the pulsar, the south jet appears to be as broad as the diameter of the inner ring at its beginning, in contrast to the narrow jet of the Crab. This morphology of the broad jet is consistent with a recently proposed theoretical model in which magnetic hoop stress diverts and squeezes the postshock equatorial flow toward the poloidal direction, generating a jet.
A Time-Series Analysis of the H$\alpha$ Emission Line in V3885 Sagitarii
Authors: Ribeiro Fabiola M. A. , Diaz Marcos P.
Published: March 2014

Flickering is a phenomenon related to mass accretion observed among many classes of astrophysical objects. In this paper we present a study of flickering emission lines and the continuum of the cataclysmic variable V3885 Sgr. The flickering behavior was first analyzed through statistical analysis and the power spectra of lightcurves. Autocorrelation techniques were then employed to estimate the flickering timescale of flares. A cross-correlation study between the line and its underlying continuum variability is presented. The cross-correlation between the photometric and spectroscopic data is also discussed. Periodograms, calculated using emission-line data, show a behavior that is similar to those obtained from photometric datasets found in the literature, with a plateau at lower frequencies and a power-law at higher frequencies. The power-law index is consistent with stochastic events. The cross-correlation study indicates the presence of a correlation between the variability on H$\alpha$ and its underlying continuum. Flickering timescales derived from the photometric data were estimated to be 25 min for two lightcurves and 10 min for one of them. The average timescales of the line flickering is 40 min, while for its underlying continuum it drops to 20 min.
Global Disk Oscillations in Binary Be Stars
Authors: Oktariani Finny , Okazaki Atsuo T.
Published: March 2014

We consider the effects of the tidal interaction with the companion, via orbital separation and the binary mass ratio, on the global one-armed oscillation modes in disks around binary Be stars. Our model takes into account a three-dimensional effect that contributes to mode confinement, which was recently found by Ogilvie (2008). We find that the one-armed oscillations are well confined in systems with disks larger than a few tens of stellar radii. In such systems, the oscillation period depends little on the binary parameters. On the other hand, in systems with smaller disks, where mode confinement is incomplete, the oscillation period increases with increasing orbital separation and/or decreasing binary mass ratio. The eigenmode is insensitive to the spectral type of the central star. Our results suggest that the dependence of the V$/$R oscillation period on the orbital separation and binary mass ratio should be observed only in short-period binary systems, and that, for systems with a similar orbital period, those with higher mass ratios will show shorter V$/$R variations.
Kinematic and Excitation Structure of the NGC 1068 Narrow-Line Region
Authors: Ozaki Shinobu
Published: March 2014

We investigated the kinematic and excitation structure of the NGC 1068 narrow-line region (NLR). We obtained profiles of several emission lines ([O iii]$\lambda$5007, H$\beta$, [O i]$\lambda$6300, and [Fe vii]$\lambda$6087) at high-velocity resolution ($R$$\sim$ 7500–11000), and confirmed that they showed different profiles. These profiles are useful for understanding the NLR structure, since they cover a wide ionization-potential range. By comparing the results with a photoionization model, we found that: (1) blueshifted components at the center are very dense, (2) those in the northeast region have slightly lower densities than those in the center, and (3) the ionization parameters of the blueshifted components increase with increasing velocity with respect to the systemic velocity. We investigated the NLR structure in NGC 1068 based on these results. We show that both the observed velocity dependence of the ionization parameter and the gradually increasing velocity field can be reproduced by varying the ionizing continuum attenuation, assuming a hollowed biconical geometry and varying the column densities of outflowing clouds.
An Orbital Period Investigation of the Semi-Detached Near-Contact Binary DD Monocerotis
Authors: Sheng-Bang Qian , Li-Ying Zhu , Boonrucksar Soonthornthum , Fu-Yuan Xiang , Jia-Jia He
Published: March 2014

The variations of the orbital period of the near-contact binary system DD Monocerotis were analyzed based on three new CCD times of light minimum together with others compiled from the literature. The general trend of the ($O-C$)$_1$ curve indicates a continuous period increase at a rate of $dP/dt$$=$$+$1.40 $\times$ 10$^{-7}$d yr$^{-1}$. Meanwhile, by using all available photoelectric and CCD data, a small-amplitude period oscillation ($A$$=$ 0.0039 d; $T=$ 18.8 yr) was found to be superimposed on the period increase. The continuous period increase is explained by mass transfer from the less-massive component to the more-massive one ($dM_{2}/dt$$=$$+$6.99 $\times$ 10$^{-8}M_{\odot}$yr$^{-1}$), which is consistent with the semi-detached configuration of the binary with a lobe-filling secondary discovered by Qian et al. (1997, A&AS, 125, 475). We showed that the timescale of the period change is close to the thermal time scale of the secondary, suggesting that DD Monocerotis is undergoing a case A mass transfer. The small-amplitude period oscillation reveals the presence of an extremely cool stellar companion ($M_3$sin${i^{\prime}}$$=$ 0.13$M_{\odot}$) in the system. Accumulation of photoelectric and CCD data will discover small-amplitude cyclic changes in many close binary stars in the future.
Spectropolarimetry with the Hida Domeless Solar Telescope
Authors: Hanaoka Yoichiro
Published: March 2014

We developed a spectropolarimetry system with a ferroelectric liquid crystal polarization modulator for the 60-cm Domeless Solar Telescope of Hida Observatory. The telescope is equipped with two oblique-reflection mirrors, that alter the incident polarization before it reaches the polarimeter. Furthermore, it is impossible to calibrate the polarimeter using unpolarized light because of the instrumental polarization. Here, we develop a procedure to obtain the parameters of both the instrumental polarization and for the calibration of the polarimeter from the same calibration data sets. We apply the new procedure to carry out high-sensitivity spectropolarimetry. It is now possible to measure the polarizations of various photospheric and chromospheric lines with the Domeless Solar Telescope.
High-Dispersion Spectroscopic Study of Solar Twins: HIP 56948, HIP 79672, and HIP 100963
Authors: Takeda Yoichi , Tajitsu Akito
Published: March 2014

An intensive spectroscopic study was performed for three representative solar twins (HIP 56948, HIP 79672, and HIP 100963) as well as for the Sun (Moon; reference standard), with intentions of (1) quantitatively discussing the relative-to-Sun similarities based on the precisely established differential parameters and (2) investigating the reason that causes the Li abundance differences, despite their similarities. It was concluded that HIP 56948 most resembles the Sun in every respect, including the Li abundance (though not perfectly similar) among the three, and deserves the name of “closest-ever solar twin”, while HIP 79672 and HIP 100963 have a somewhat higher effective temperature and appreciably higher surface Li composition. While there is an indication of Li being rotation-dependent, because the projected rotation in HIP 56948 (and the Sun) is slightly lower than the other two, the rotational difference alone does not seem to be so large as to efficiently produce a marked change in Li. Rather, this may be more likely to be attributed (at least partly) to a slight difference in $T_{\rm eff}$ via some $T_{\rm eff}$-sensitive Li-controlling mechanism. Since the abundance of Be was found to be essentially solar for all stars irrespective of Li, any physical process causing the Li diversity should work only on Li without affecting Be.