bluuebunny/crossref_metadata_2025 huggingface dataset:
The 2006 November Outburst of EG Aquarii: the SU UMa Nature Revealed
Authors: Imada Akira , Stubbings Rod , Kato Taichi , Uemura Makoto , Krajci Thomas , Torii Ken’ichi , Sugiyasu Kei , Kubota Kaori , Moritani Yuuki , Ishioka Ryoko , Masi Gianluca , Kiyota Seiichiro , Monard L. A. G. , Maehara Hiroyuki , Nakajima Kazuhiro , Arai Akira , Ohsugi Takashi , Yamashita Takuya , Kawabata Koji S. , Nagae Osamu , Chiyonobu Shingo , Fukazawa Yasushi , Mizuno Tsunefumi , Katagiri Hideaki , Takahashi Hiromitsu , Ueda Atsushi , Hayashi Takehiro , Okita Kiichi , Yoshida Michitoshi , Yanagisawa Kenshi , Sato Shuji , Kino Masaru , Kitagawa Masahiro , Sadakane Kozo , Nogami Daisaku
Published: March 2014

We report on time-resolved CCD photometry of the cataclysmic variable EG Aquarii during a 2006 November outburst. During the outburst, superhumps were unambiguously detected with a mean period of 0.078828(6) d, allowing for the first time to classify the object as an SU UMa-type dwarf nova. It also turned out that the outburst contained a precursor. At the end of the precursor, immature profiles of humps were observed. By a phase analysis of these humps, we interpreted the features as being superhumps. This is the second example that the superhumps were shown during a precursor. Near the maximum stage of the outburst, we discovered an abrupt shift of the superhump period by ${\sim\;}$0.002 d. After the supermaximum, the superhump period decreased at a rate of $\dot{P}/P =$$-$8.2${\;\times\;}$10$^{-5}$, which is typical for SU UMa-type dwarf novae. Although the outburst light curve was characteristic of SU UMa-type dwarf novae, long-term monitoring of the variable shows no outbursts over the past decade. We also comment on the basic properties of long period and inactive SU UMa-type dwarf novae.
Integral and RXTE/ASM Observations on IGR J17098−3628
Authors: Chen Yu-Peng , Zhang Shu , Schurch Nick , Wang Jian-Min , Collmar Werner , Li Ti-Pei , Qu Jin-Lu , Zhang Cheng-Min
Published: March 2014

To further probe the possible nature of the unidentified source IGR J17098$-$3628, we have carried out a detailed analysis of its long-term time variability, as monitored by Rossi X-ray Timing Explorer/All Sky Monitor (RXTE/ASM), and of its hard X-ray properties, as observed by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL). INTEGRAL has monitored this sky region for years, and significantly detected IGR J17098$-$3628 only when the source was in its dubbed active state. In particular, at $\ge$20 keV, Imager on Board of the INTEGRAL Satellite/INTEGRAL Soft Gamma-Ray Imager (IBIS/ISGRI) caught an outburst in 2005 March, lasting for $\sim$5 d with a detection significance of 73$\sigma$ (20-40 keV) and with emission at $/lt$200 keV. ASM observations have revealed that the outburst of the soft X-ray lightcurve is similar to that detected by INTEGRAL; however the peak of the soft X-ray lightcurve lags behind, or is preceded by, the hard X-ray ($/gt$20 keV) outburst by $\sim$2 d. This resembles the behavior of X-ray novae like XN 1124$-$683, and hence further suggests a Low-Mass X-ray Binary (LMXB) nature for IGR J17098$-$3628. While the quality of the ASM data prevents us from drawing any definite conclusions, these discoveries are important clues that, coupled with future observations, will help us to resolve the nature of IGR J17098$-$3628 that is unknown so far.
Dual-Beam Delay Calibration for VERA
Authors: Honma Mareki , Kijima Masachika , Suda Hiroshi , Kawaguchi Noriyuki , Kobayashi Hideyuki , Bushimata Takeshi , Shimizu Rie , Yoshimura Akane , Sasao Tetsuo , Hirota Tomoya , Imai Hiroshi , Iwadate Kenzaburo , Jike Takaaki , Kameya Osamu , Kamohara Ryuichi , Kuji Seisuke , Kurayama Tomoharu , Manabe Seiji , Miyaji Takeshi , Nakagawa Akiharu , Omodaka Toshihiro , Oyama Tomoaki , Sakai Satoshi , Sato Katsuhisa , Shibata Katsunori M. , Tamura Yoshiaki
Published: March 2014

We present the technique of instrumental delay calibration for the dual-beam system of VLBI Exploration of Radio Astrometry (VERA), namely, the horn-on-dish method, in which artificial noise sources are mounted on the antenna feedome base and a wide-band radio noise is injected into the dual-beam receivers after reflection by a subreflector. We introduce the basic concept of calibration with the horn-on-dish method, and also present results of the experiments to evaluate its calibration accuracy. Detailed comparisons between model path calculations and measured paths from the noise sources show that the horn-on-dish method can calibrate the dual-beam delay difference in the antenna structure and receiver within an $\sim$0.1mm level. We estimated that the systematic error in the calibration does not exceed 0.127mm, which was evaluated at an elevation angle of 15$^\circ$. This error corresponds to an astrometric error of $\sim$11$\mu$as with VERA's maximum baseline. An experimental confirmation of the systematic error in the horn-on-dish method has also been obtained by using a pair of 10m and VERA's 20m antennas at the Mizusawa station, demonstrating that the systematic difference between the dual-beam delay difference measured with noise sources and that for celestial objects was 0.118mm, being consistent with the above estimate.
Distance to NGC 281 in a Galactic Fragmenting Superbubble: Parallax Measurements with VERA
Authors: Sato Mayumi , Hirota Tomoya , Honma Mareki , Kobayashi Hideyuki , Sasao Tetsuo , Bushimata Takeshi , Choi Yoon Kyung , Imai Hiroshi , Iwadate Kenzaburo , Jike Takaaki , Kameno Seiji , Kameya Osamu , Kamohara Ryuichi , Kan-Ya Yukitoshi , Kawaguchi Noriyuki , Kim Mi Kyoung , Kuji Seisuke , Kurayama Tomoharu , Manabe Seiji , Matsui Makoto , Matsumoto Naoko , Miyaji Takeshi , Nagayama Takumi , Nakagawa Akiharu , Nakamura Kayoko , Oh Chung Sik , Omodaka Toshihiro , Oyama Tomoaki , Sakai Satoshi , Sato Katsuhisa , Shibata Katsunori M. , Tamura Yoshiaki , Yamashita Kazuyoshi
Published: March 2014

We have used the Japanese VLBI array VERA to perform high-precision astrometry of an H$_2$O maser source in the Galactic star-forming region NGC 281 West, which has been considered to be part of a 300-pc superbubble. We successfully detected a trigonometric parallax of 0.355$\pm$0.030mas, corresponding to a source distance of 2.82$\pm$0.24kpc. Our direct distance determination of NGC 281 has resolved a large distance discrepancy between previous photometric and kinematic studies; likely NGC 281 is in the far side of the Perseus spiral arm. The source distance as well as the absolute proper motions were used to demonstrate the 3D structure and expansion of the NGC 281 superbubble, $\sim\;$650pc in size parallel to the Galactic disk and with a shape slightly elongated along the disk or spherical, but not vertically elongated, indicating that the superbubble expansion may be confined to the disk. We estimate the expansion velocity of the superbubble as being $\sim\;20$km s$^{-1}$, both perpendicular to and parallel to the Galactic disk with a consistent timescale of $\sim\;20$Myr.
SiO Maser Observations toward Orion-KL with VERA
Authors: Kim Mi Kyoung , Hirota Tomoya , Honma Mareki , Kobayashi Hideyuki , Bushimata Takeshi , Choi Yoon Kyung , Imai Hiroshi , Iwadate Kenzaburo , Jike Takaaki , Kameno Seiji , Kameya Osamu , Kamohara Ryuichi , Kan-Ya Yukitoshi , Kawaguchi Noriyuki , Kuji Seisuke , Kurayama Tomoharu , Manabe Seiji , Matsui Makoto , Matsumoto Naoko , Miyaji Takeshi , Nagayama Takumi , Nakagawa Akiharu , Oh Chung Sik , Omodaka Toshihiro , Oyama Tomoaki , Sakai Satoshi , Sasao Tetsuo , Sato Katsuhisa , Sato Mayumi , Shibata Katsunori M. , Tamura Yoshiaki , Yamashita Kazuyoshi
Published: March 2014

We present results of phase-referencing VLBI observations of SiO masers in the Orion-KL region made with VERA. Using a strong maser spot in the 43GHz $v =$ 2 $J=$ 1-0 emission, we derived the trigonometric parallax of Orion-KL to be 2.39$\pm$0.03mas, corresponding to a distance of 418$\pm$6pc, with the highest accuracy among existing parallax measurements of the source. We made a superimposed image of $v =$ 1 $J=$ 1-0 and $v =$ 2 $J=$ 1-0 maser features in Orion-KL based on absolute positions obtained from the phase-referencing astrometry with a common reference source. The maser features of both transitions show similar X-shaped distributions centered at Source I. However, in each of the four arms of the X-shape, the SiO $v =$ 2 features tend to lie closer to Source I than the SiO $v =$ 1 features. The radial velocities of the maser emission decrease with the distance from Source I. The spatial and radial velocity distributions of the SiO masers suggest that the SiO masers lie in the rotating materials associated with a disk around Source I, rather than a decelerating outflow.
Asymmetric Ejecta Distribution of the Cygnus Loop Revealed with Suzaku
Authors: Katsuda Satoru , Tsunemi Hiroshi , Miyata Emi , Mori Koji , Namiki Masaaki , Nemes Norbert , Miller Eric D.
Published: March 2014

We observed a linearly sliced area of the Cygnus Loop from the north-east to the south-west with Suzaku in seven pointings. After dividing the entire fields of view (FOV) into 119 cells, we extracted spectra from all of the cells and performed spectral analysis for them. We then applied both one- and two-component non-equilibrium ionization (NEI) models for all of the spectra, finding that almost all were significantly better fitted by the two-component NEI model rather than the one-component NEI model. Judging from the abundances, the high-$kT_\mathrm{e}$ component must be the ejecta component, while the low-$kT_\mathrm{e}$ component comes from the swept-up matter. Therefore, the ejecta turn out to be distributed inside a large area (at least our FOV) of the Cygnus Loop. We divided the entire FOV into northern and southern parts, and found that the ejecta distributions were asymmetric to the geometric center: the ejecta of Si, S, and Fe seem to be distributed more in the south than in the north of the Cygnus Loop by a factor of $\sim$2. The degree of ejecta-asymmetry is consistent with that expected by recent supernova explosion models.
Suzaku Observation of the RCW86 Northeastern Shell
Authors: Yamaguchi Hiroya , Koyama Katsuji , Nakajima Hiroshi , Bamba Aya , Yamazaki Ryo , Vink Jacco , Kawachi Akiko
Published: March 2014

This paper reports on Suzaku results concerning the northeast shell of RCW86. With both spatial and spectral analyses, we separated the X-rays into three distinct components: low ($kT_{\rm e}\sim$0.3keV) and high ($kT_{\rm e}\sim$1.8keV) temperature plasmas and a non-thermal component, and discovered that their spatial distributions are different from each other. The low-temperature plasma is dominated at the east rim, whereas the non-thermal emission is brightest at the northeast rim, which is spatially connected from the east. The high-temperature plasma, found to contain the $\sim$6.42keV line (K$\alpha$ of low-ionized iron), is enhanced at the inward region with respect to the east rim, and has no spatial correlation with the non-thermal X-rays (the northeast). This result suggests that the Fe-K$\alpha$ line originates from Fe-rich ejecta heated by reverse shock. A possible scenario to explain these morphologies and spectra is that a fast-moving blast wave in a thin cavity collided with a dense interstellar medium at the east region very recently. As a result, the reverse shock in this interior decelerated, and arrived at the Fe-rich region of the ejecta and heated it. In the northeast rim, on the other hand, the blast wave is still moving fast, and is accelerating electrons causing them to emit strong synchrotron X-rays.
Suzaku X-Ray Spectroscopy of a Peculiar Hot Star in the Galactic Center Region
Authors: Hyodo Yoshiaki , Tsujimoto Masahiro , Koyama Katsuji , Nishiyama Shogo , Nagata Tetsuya , Sakon Itsuki , Murakami Hiroshi , Matsumoto Hironori
Published: March 2014

We present the results of a Suzaku study of a bright point-like source in the 6.7keV intensity map of the Galactic center region. We detected an intense FeXXV 6.7keV line with an equivalent width of $\sim$1keV as well as emission lines of highly ionized Ar and Ca from a spectrum obtained by the X-ray Imaging Spectrometer. The overall spectrum is described very well by a heavily absorbed ($\sim$2$\times$10$^{23}$cm$^{-2}$) thin thermal plasma model with a temperature of 3.8$\pm$0.6keV and a luminosity of $\sim$3$\times$10$^{34}$ergs$^{-1}$ (2.0-8.0keV) at 8kpc. The absorption, temperature, luminosity, and the 6.7keV line intensity were confirmed with the archived XMM-Newton data. The source has a very red ($J-K_{\rm s}=$ 8.2mag) infrared spectral energy distribution (SED), which was fitted by a blackbody emission of $\sim$1000K attenuated by a visual extinction of $\sim$31mag. The high plasma temperature and the large X-ray luminosity are consistent with a wind-wind colliding Wolf-Rayet binary. The similarity of the SED to those of the eponymous Quintuplet cluster members suggests that the source is a WC-type source.
Suzaku Observation of G359.79$-$0.26, a New Supernova Remnant Candidate in the Galactic Center
Authors: Mori Hideyuki , Tsuru Takeshi Go , Hyodo Yoshiaki , Koyama Katsuji , Senda Atsushi
Published: March 2014

Utilizing Suzaku observations, we obtained the X-ray spectrum of G359.79$-$0.26, an extended X-ray feature nearby the Galactic center (GC) supernova remnant (SNR) SgrA East. We estimated the contribution from the Galactic center diffuse X-rays, which allows us a proper background subtraction from the faint extended source. A thin thermal plasma with a temperature of $ kT_{\rm e} \sim 1$keV and slightly enhanced metal abundances (S and Ar) are required to reproduce the G359.79$-$0.26 spectrum. The absorption column density ($N_{\rm H} \sim 4 \times 10^{22}$ cm$^{-2}$) associated with the plasma indicates that G359.79$-$0.26 is located in the GC. The thermal energy of the plasma is estimated to be $1.7 \times 10^{50}$erg, typical for galactic SNRs. Its center-filling X-ray emission surrounded by a shell-like radio structure suggests that G359.79$-$0.26 would be a new member of the mixed-morphology SNR class. The 2.45keV mosaic image covering a $\sim 40' \times 40'$ GC field implies an alternative possibility that G359.79$-$0.26 might be a part of a large ring-like structure with a size of $18' \times 16'$.
Spectral Properties of Prompt Emission of Four Short Gamma-Ray Bursts Observed by the Suzaku-WAM and the Konus-Wind
Authors: Ohno Masanori , Fukazawa Yasushi , Takahashi Takuya , Yamaoka Kazutaka , Sugita Satoshi , Pal'shin Valentin , Frederiks Dmitry , Oleynik Philipp , Ulanov Mikhail , Sakamoto Takanori , Sato Goro , Hurley Kevin , Tashiro Makoto S. , Urata Yuji , Onda Kaori , Tamagawa Toru , Terada Yukikatsu , Suzuki Motoko , Soojing Hong
Published: March 2014

We have performed a joint analysis of prompt emission from four bright short gamma-ray bursts (GRBs) with the Suzaku-WAM and the Konus-Wind experiments. This joint analysis allows us to investigate the spectral properties of short-duration bursts over a wider energy band with a higher accuracy. We find that these bursts have a high $E_{\rm peak}$, around 1MeV and have a harder power-law component than that of long GRBs. However, we can not determine whether these spectra follow the cut-off power-law model or the Band model.

We also investigated the spectral lag, hardness ratio, inferred isotropic radiation energy and existence of a soft emission hump, in order to classify them into short or long GRBs using several criteria, in addition to the burst duration. We find that all criteria, except for the existence of the soft hump, support the fact that our four GRBsamples are correctly classified as belonging to the short class. In addition, our broad-band analysis revealed that there is no evidence of GRBs with a very large hardness ratio, as seen in the BATSE short GRBsample, and that the spectral lag of our four short GRBs is consistent with zero, even in theMeV energy band, unlike long GRBs. Although our short GRBsamples are still limited, these results suggest that the spectral hardness of short GRBs might not differ significantly from that of long GRBs, and also that the spectral lag at high energies could be a strong criterion for burst classification.
AKARI IRC Survey of the Large Magellanic Cloud: Outline of the Survey and Initial Results
Authors: Ita Yoshifusa , Onaka Takashi , Kato Daisuke , TanabÉ Toshihiko , Sakon Itsuki , Kaneda Hidehiro , Kawamura Akiko , Shimonishi Takashi , Wada Takehiko , Usui Fumihiko , Koo Bon-Chul , Matsuura Mikako , Takahashi Hidenori , Nakada Yoshikazu , Hasegawa Tetsuo , Tamura Motohide
Published: March 2014

We observed an area of 10deg$^2$ of the Large Magellanic Cloud using the Infrared Camera (IRC) on board AKARI. The observations were carried out using five imaging filters (3, 7, 11, 15, and 24$\mu$m) and a dispersion prism (2-5$\mu$m, $\lambda / \Delta\lambda \sim$ 20) equipped in the IRC. This paper describes an outline of our survey project, and presents some initial results using imaging data that detected over 5.9$\times$10$^5$ near-infrared and 6.4$\times$10$^4$ mid-infrared point sources. The 10$\sigma$ detection limits of our survey are about 16.5, 14.0, 12.3, 10.8, and 9.2 in Vega-magnitude at 3, 7, 11, 15, and 24$\mu$m, respectively. The 11 and 15$\mu$m data, which are unique to AKARI IRC, allow us to construct color-magnitude diagrams that are useful to identify stars with circumstellar dust. We found a new sequence in the color-magnitude diagram, which is attributed to red giants with luminosity fainter than that of the tip of the first red-giant branch. We suggest that this sequence is likely to be related to the broad emission feature of aluminum oxide at 11.5$\mu$m. The 11 and 15$\mu$m data also indicate that the ([11]$-$[15]) color of both oxygen-rich and carbon-rich red giants once becomes blue, and then turns red again in the course of their evolution, probably due to a change in the flux ratio of the silicate or silicon carbide emission feature at 10 or 11.3$\mu$m to the 15$\mu$m flux.
On Period Variations of the K-Type Eclipsing Binary BM Ursae Majoris
Authors: Yang Yang-Gui , Wei J.-Y. , Nakajima Kazuhiro
Published: March 2014

From new CCD observations, 11 light minimum times are presented in this paper. The orbital period change of a W UMa-type eclipsing binary, BM Urase Majoris, was investigated, based on all available times of light minimum. It was discovered that the orbital period of the binary shows cyclic oscillation, superimposed on a secular period decrease. The amplitude and the period of the cyclic variation are $A$$=$ 0.0101($\pm$0.0004)d and $P_{3}$$=$ 30.8($\pm$0.2)yr, respectively. This kind of cyclic variation may be due to a light-time effect via an unseen third body. If the existence of an additional body is true, it may remove a great amount of angular momentum from the central system, and may play an important role in the formation of close binary. The orbital period continuously decreases at a rate of $dP/dt$$=$$-$7.49($\pm$0.16) $\times$ 10$^{-8}$dyr$^{-1}$, which may be due to mass transfer from the primary to the secondary, accompanying mass and angular-momentum loss from the binary system. The orbital period decrease, accompanying mass and angular momentum loss, would cause the contact degree to increase. Therefore, this binary will evolve into a deep contact configuration.
Analysis of the Spatial Distribution of Galaxies in the Numerical Galaxy Catalog
Authors: Ueda Haruhiko , Nagashima Masahiro , Yahagi Hideki
Published: March 2014

We examine the spatial distribution of galaxies in the Numerical Galaxy Catalog, which is based on a hierarchical clustering framework. This catalog is constructed from a semianalytic model of galaxy formation combined with high-resolution $N$-body simulations in a $\Lambda$-dominated flat cold dark-matter cosmological model. To quantify the spatial distribution of galaxies, we use a graph-theoretical approach, because it is one of the most powerful statistical ways of estimating spatial data. In particular, three types of graphs are adopted: the Delaunay graph, the minimal spanning tree, and the constellation graph. To quantify the galaxy distributions, we apply statistical measures suitable for each type. The mass distributions in the cold dark-matter universe are also examined to clarify differences in the spatial distribution of dark matter and galaxies. The spatial distribution of galaxies in the two-degree field (2dF) galaxy redshift survey is finally compared with that in the Numerical Galaxy Catalog. From our analysis, we definitely show that galaxy distributions in the Numerical Galaxy Catalog are different from the dark-matter distributions. We also find that the Numerical Galaxy Catalog considerably improves the theoretical prediction of spatial galaxy distributions, although it does not do enough to reproduce the 2dF galaxy redshift survey. Finally, we show that the constellation graph and the minimal spanning tree are convenient for quantifing the galaxy distributions in an objective manner.
Suzaku Results on the Obscured Low-Luminosity Active Galactic Nucleus in NGC 4258
Authors: Yamada Shin’ya , Itoh Takeshi , Makishima Kazuo , Nakazawa Kazuhiro
Published: March 2014

In 2006 June, the obscured low-luminosity active galactic nucleus in the nearby Seyfert 1.9 galaxy NGC 4258 was observed with Suzaku for $\sim$100 ks. Utilizing the XIS and the HXD, the nucleus emission was detected over a $\sim$2 to $\sim$40 keV range, with an unabsorbed 2–10 keV luminosity of $\sim$8 $\times$ 10$^{40}$ergs$^{-1}$; it varied by a factor of $\sim$2 during the observation. Its 2–40 keV spectrum is reproduced by a single power law with a photon index of $\Gamma$$\sim$ 2.0, absorbed by an equivalent hydrogen column of $\sim$1.0 $\times$ 10$^{23}$cm$^2$. The spectrum within $4{}^{\prime}$ of the nucleus also required a softer thin-thermal emission, as well as an intermediate hardness component, attributable to integrated point sources. A weak neutral Fe-K$\alpha$ florescence line was detected at an equivalent width of $\sim$40 eV. A cold reflection component was not required by the data, with the reflector solid angle $\Omega$ seen from the nucleus constrained as $\Omega /$2$\pi$$\lesssim$ 0.3, assuming a general case of 60$^\circ$ inclination. The results suggest that the cold reflecting material around the nucleus is localized along our line of sight, rather than forming a thick torus.
Hard X-Ray Properties of the Merging Cluster Abell 3667 as Observed with Suzaku
Authors: Nakazawa Kazuhiro , Sarazin Craig L. , Kawaharada Madoka , Kitaguchi Takao , Okuyama Sho , Makishima Kazuo , Kawano Naomi , Fukazawa Yasushi , Inoue Susumu , Takizawa Motokazu , Wik Daniel R. , Finoguenov Alexis , Clarke Tracy E.
Published: March 2014

Wide-band Suzaku data on the merging cluster Abell 3667 were examined for hard X-ray emission in excess to the known thermal component. Suzaku detected X-ray signals in a wide energy band from 0.5 to 40 keV. The hard X-ray ($\gt$10 keV) flux observed by the HXD around the cluster center cannot be explained by a simple extension of the thermal emission with an average temperature of $\sim$7 keV. The emission is most likely to be from a very hot ($kT$$\gt$ 13.2 keV) thermal component around the cluster center, produced via a strong heating process in a merger. In the north-west radio relic, no signature of non-thermal emission was observed. Using the HXD, the overall upper-limit flux within a 34$^\prime$$\times$ 34$^\prime$ field-of-view around the relic was derived to be 5.3 $\times$ 10$^{-12}$ergs$^{-1}$cm$^{-2}$ in the 10–40 keV band, after subtracting the ICM contribution estimated using the XIS or the XMM-Newton spectra. Directly on the relic region, the upper limit is further tightened by the XIS data to be less than 7.3 $\times$ 10$^{-13}$ergs$^{-1}$cm$^{-2}$, when converted into the 10–40 keV band. The latter value suggest that the average magnetic field within the relic is higher than 1.6 $\mu$G. The non-thermal pressure due to magnetic fields and relativistic electrons may be as large as $\sim$20% of the thermal pressure in the region.
Effects of Minor Mergers on the Coalescence of a Supermassive Black Hole Binary
Authors: Matsui Hidenori , Habe Asao
Published: March 2014

We studied the possibility that minor mergers can resolve the loss cone depletion problem, which is a difficulty that occurs in the coalescence process of a supermassive black hole (SMBH) binary, by performing numerical simulations with a highly accurate $N$-body code. We showed that a minor merger of a dwarf galaxy disturbs stellar orbits in the galactic central region of the host galaxy where loss cone depletion has already been caused by the SMBH binary. The disturbed stars are supplied into the loss cone. Stars of the dwarf galaxy are also supplied into the loss cone. The gravitational interactions between the SMBH binary and these stars become very effective. The gravitational interaction decreases the binding energy of the SMBH binary effectively. As a result, shrinking of the separation of the SMBH binary is accelerated. Our numerical results strongly suggest that minor mergers are one of the important processes to reduce the coalescence time of the SMBH binary to much less than the Hubble time.
Determination of the Pattern Speed of Barred Spiral Galaxies
Authors: Hirota Akihiko , Kuno Nario , Sato N. , Nakanishi Hiroyuki , Tosaki Tomoka , Matsui Hidenori , Habe Asao , Sorai Kazuo
Published: March 2014

We evaluated the availability of a method proposed by Kuno et al. (2000, PASJ, 52, 775) for measuring the pattern speed of barred galaxies, and applied it to observational data. We made error estimations using a hydrodynamical galaxy model to test the validity of the method. Error estimations suggest that the method is able to determine the pattern speed within an error of 10%–20%. The method was applied to $^{12}$CO (1–0) data of three late-type barred galaxies: NGC 2903, M 83, and NGC 3627. The derived pattern speed was 40 kms$^{-1}$kpc$^{-1}$ for NGC 2903, 57 kms$^{-1}$kpc$^{-1}$ for M 83, 39 kms$^{-1}$kpc$^{-1}$ for NGC 3627, respectively. For the sake of a comparison with measurements in other galaxies, we used the distance-independent value $\cal{R}$ ($\equiv$$R_{\rm {CR}}/R_{\rm {bar}}$), and found that bars in the three late-type spirals are “slow” ($\cal{R} \gt$ 1.4). Our results support recent claims that bars are not always “fast” ($\cal{R}$$\le$ 1.4), at least for late-type spiral galaxies.
A Search for Molecular Gas toward a BzK-Selected Star-Forming Galaxy at z = 2.044
Authors: Hatsukade Bunyo , Iono Daisuke , Motohara Kentaro , Nakanishi Kouichiro , Hayashi Masao , Shimasaku Kazuhiro , Nagao Tohru , Tamura Yoichi , Malkan Matthew A. , Ly Chun , Kohno Kotaro
Published: March 2014

We present a search for CO (3–2) emission in SDF-26821, a $BzK$-selected star-forming galaxy (sBzK) at $z$$=$ 2.044, using the 45-m telescope of the Nobeyama Radio Observatory and the Nobeyama Millimeter Array. We did not detect significant emission, and derived the 2$\sigma$ limits: CO luminosity of $L^\prime_{\rm {CO}}$ 3.1 $\times$ 10$^{10}$Kkms$^{-1}$pc$^{-2}$, ratio of far-infrared luminosity to CO luminosity of $L_{\rm {FIR}}/L^\prime_{\rm {CO}}$$>$ 57 (Kkms$^{-1}$pc$^{2}$)$^{-1}$, and molecular gas mass of $M_{\rm {H_2}}$ 2.5 $\times$ 10$^{10}$, assuming a velocity width of 200 kms$^{-1}$ and a CO-to-H$_2$ conversion factor of $\alpha_{\rm {CO}}$$=$$0.8$ (Kkms$^{-1}$pc$^{2}$)$^{-1}$. The ratio $L_{\rm {FIR}}/L^\prime_{\rm {CO}}$, a measure of the star-formation efficiency (SFE), is comparable to, or higher than, the two $z$$\sim$ 1.5 sBzKs detected in CO (2-1) previously, suggesting that sBzKs can have a wide range of SFEs. Comparisons of far-infrared luminosity, gas mass, and stellar mass among the sBzKs suggest that SDF-26821 is at an earlier stage of forming stars with a similar SFE and/or more efficiently forming stars than the two $z$$\sim$ 1.5 sBzKs. The higher SFEs and specific star-formation rates of the sBzKs compared to local spirals are indicative of a difference in the star-formation modes between these systems, suggesting that sBzKs are not just scaled-up versions of local spirals.
New Period Investigation of Algol-like Near-Contact Binary EG Cephei
Authors: Ying Zhu Li , Sheng Bang Qian , Wen Ping Liao , Miloslav Zejda , Zdenek Mikulášek
Published: March 2014

The Algol-like Near Contact Binary EG Cephei was observed in 2008 October. One new observed time of the secondary minimum was derived in $BV(IR)_{\rm c}$ bands. It turns out that the times of minima at longer wavelengths occur earlier than the shorter ones. All of the available eclipse times, including 735 epochs, spanning more than 100 years were analyzed. A period oscillation with a period of 35.8($\pm$0.1)yr and an amplitude of about 0.0037($\pm$0.0002)d was found, while undergoing a secular increase at a rate of $dP/dt$$=$ 3.4 $\times$ 10$^{-8}$($\pm$0.1)dyr$^{-1}$. This continuous period increase may be caused by mass transfer from the secondary component to the primary one on a thermal timescale, which is consistent with the Algol-like semi-detached configuration of EG Cep. Combining with the spectroscopic and photometric results, we derived a conservative mass-transfer rate of this target, $dM/dt$$=$ 3.0($\pm$0.1) $\times$ 10$^{-8}M_{\odot}$yr$^{-1}$. The oscillation part of the period variation may be the result of a light-time effect due to the existence of a coplanar additional body with a mass of $M_{3}$$=$ 0.11$M_{\odot}$, and a corresponding radius of $a_{3}$$=$ 14AU. The presumed third body may play an important role in the evolution of this system.
Observational Appearance of Black Hole Winds
Authors: Fukue Jun , Sumitomo Naoko
Published: March 2014

We examine the observational appearance of an optically thick, spherically symmetric, relativistic wind (a black hole wind). In a relativistic flow, the apparent optical depth becomes small in the downstream direction, while it is large in the upstream direction due to the relativistic effect. Hence, the apparent photosphere of the relativistic flow depends on the flow velocity and direction as well as the density distribution. We calculated the temperature distribution of the apparent photosphere of the optically thick black hole wind, where the wind speed was assumed to be constant and radiation dominates matter, for various values of the wind speed and mass-outflow rate. We found that the limb-darkening effect is strongly enhanced in the relativistic regime. We also found that the observed luminosities of the black hole wind become large as the wind speed increases, but do not depend on the mass-outflow rate.
Subaru/COMICS Mid-Infrared Observation of the Near-Nucleus Region of Comet 17P/Holmes at the Early Phase of an Outburst
Authors: Watanabe Jun-ichi , Honda Mitsuhiko , Ishiguro Masateru , Ootsubo Takafumi , Sarugaku Yuki , Kadono Toshihiko , Sakon Itsuki , Fuse Tetsuharu , Takato Naruhisa , Furusho Reiko
Published: March 2014

Mid-infrared 8–25$\mu$m imaging and spectroscopic observations of the comet 17P/Holmes in the early phase of its outburst in brightness were performed on 2007 October 25–28UT using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the 8.2-m Subaru Telescope. We detected an isolated dust cloud that moved toward the south-west direction from the nucleus. The 11.2$\mu$m peak of a crystalline silicate feature onto a broad amorphous silicate feature was also detected both in the central condensation of the nucleus and an isolated dust cloud. The color temperature of the isolated dust cloud was estimated to be $\sim$200 K, which is slightly higher than the black-body temperature. Our analysis of the motion indicates that the isolated cloud moved anti-sunward. We propose several possibilities for the motion of the cloud: fluffy dust particles in the isolated cloud started to depart from the nucleus due to radiation pressure almost as soon as the main outburst occurred, or dust particles moved by some other anti-sunward forces, such as a rocket effect and photophoresis when the surrounding dust coma became optically thin. The origin and the nature of the isolated dust cloud are discussed in this paper.
A Super Bubble Candidate in the Galactic Center and a Local Enhancement G359.77$-$0.09
Authors: Mori Hideyuki , Hyodo Yoshiaki , Tsuru Takeshi Go , Nobukawa Masayoshi , Koyama Katsuji
Published: March 2014

A 20$^\prime$$\times$ 16$^\prime;$ elliptical ring-like structure has been found near the Galactic center in the narrow energy band corresponding to the K$\alpha$ line from He-like sulfur. In the ring, two diffuse sources are found, a supernova remnant candidate, G359.79$-$0.26, and an unidentified source, G359.77$-$0.09. The X-ray spectrum of G359.77$-$0.09 is similar to that of G359.79$-$0.26, which can be explained by an absorbed thin thermal plasma model with temperatures of 0.7 and 1.0 keV. The absorption column densities of these two sources are large ($N_{\rm H}$$=$ 6.9 $\times$ 10$^{22}$ and 4.5 $\times$ 10$^{22}$cm$^{-2}$) and are consistent with that of the Galactic center distance. The X-ray spectrum extracted from the ring-like structure is also represented by an absorbed thin thermal plasma model ($kT_{\rm e}$$\sim$ 0.9 keV). The thermal energy of the plasma filling the ring-like structure is estimated to be 1.0 $\times$ 10$^{51}$erg. We therefore propose that the two sources comprise a single ring-like object, which is possibly a super bubble with a size of 49 pc $\times$40 pc in the Galactic center region.
Period Changes of DF Hydrae: Evidence of Mass Transfer and the Presence of a Cool Tertiary Companion
Authors: Xiang Fuyuan , Xie Wenli , Tian Yongpo , Tao Xia
Published: March 2014

Combining our six new determined times of light minimum obtained from 2001 to 2007 with others compiled from the literature, we investigated the period changes of DF Hydrae. The general trend of the $O-C$ curve based on all available data reveals that the period of the binary star is increasing continuously at a rate of $dP/dt$$=$$+$1.11($\pm$0.02) $\times$ 10$^{-7}$dyr$^{-1}$. After the long-term period increase was removed from the $O-C$ diagram, it was discovered that the residuals of the CCD and photoelectric observations suggest a small-amplitude cyclic oscillation with a period of 21.5 years. The continuous period increase can be explained by mass transfer from the secondary to the primary, indicating that DF Hydrae is on the TRO-controlled stage of the evolutionary scenario proposed by Qian. The cyclic period variation suggests that DF Hydrae is a triple system containing a cool tertiary component with a mass of $M_3$sin${i^{\prime}}$$=$ 0.21$M_{\odot}$ in a 21.5-year orbit. By removing angular momentum from the central binary system via Kozai oscillation or a combination of the Kozai cycle and tidal friction, the tertiary companion may play an important role for the formation and evolution of the contact system, which makes the eclipsing pair to have a short initial orbital period (i.e., $P$$\lt$ 5$^{\rm d}$). In that case, the detached progenitor of DF Hydrae evolves into the present contact configuration via a combination of magnetic braking and a case A mass transfer.
Calibration and Performance of the AKARI Far-Infrared Surveyor (FIS) — Slow-Scan Observation Mode for Point-Sources
Authors: Shirahata Mai , Matsuura Shuji , Hasegawa Sunao , Ootsubo Takafumi , Makiuti Sin’itirou , Yamamura Issei , Nakagawa Takao , Kawada Mitsunobu , Kaneda Hidehiro , Shibai Hiroshi , Doi Yasuo , Suzuki Toyoaki , Müller Thomas , Cohen Martin
Published: March 2014

We present the characterization and calibration of the Slow-Scan observation mode of the Far-Infrared Surveyor (FIS) onboard the AKARI satellite. The FIS, one of the two focal-plane instruments on AKARI, has four photometric bands between 50–180$\mu$m with two types of Ge:Ga array detectors. In addition to the All-Sky Survey, FIS has also taken detailed far-infrared images of selected targets by using the Slow-Scan mode. The sensitivity of the Slow-Scan mode is one to two orders of magnitude better than that of the All-Sky Survey, because the exposure time on a targeted source is much longer. The point spread functions (PSFs) were obtained by observing several bright point-like objects, such as asteroids, stars, and galaxies. The derived full widths at the half maximum (FWHMs) are $\sim$30$^{\prime\prime}$ for the two shorter wavelength bands and $\sim$40$^{\prime\prime}$ for the two longer wavelength bands, being consistent with those expected by optical simulation, although a certain amount of excess is seen in the tails of the PSFs. A flux calibration was performed by observations of well-established photometric calibration standards (asteroids and stars) over a wide range of fluxes. After establishing the method of aperture photometry, the photometric accuracy for point-sources is better than $\pm$15% in all of the bands, expect for the longest wavelength.
Subaru Weak-Lensing Survey II: Multi-Object Spectroscopy and Cluster Masses
Authors: Hamana Takashi , Miyazaki Satoshi , Kashikawa Nobunari , Ellis Richard S. , Massey Richard J. , Refregier Alexandre , Taylor James E.
Published: March 2014

We present the first results of a multi-object spectroscopic campaign to follow up cluster candidates located via weak lensing. Our main goals are to search for spatial concentrations of galaxies that are plausible optical counterparts of the weak-lensing signals, and to determine the cluster redshifts from those of member galaxies. Around each of 36 targeted cluster candidates, we obtained 15–32 galaxy redshifts. For 28 of these targets, we confirmed a secure cluster identification, with more than five spectroscopic galaxies within a velocity of $\pm$3000 kms$^{-1}$. This includes three cases where two clusters at different redshifts are projected along the same line-of-sight. In 6 of the 8 unconfirmed targets, we found multiple small galaxy concentrations at different redshifts, each containing at least three spectroscopic galaxies. The weak-lensing signal around those systems was thus probably created by the projection of groups or small clusters along the same line-of-sight. In both of the remaining two targets, a single small galaxy concentration was found. In some candidate super-cluster systems, we found additional evidence of filaments connecting the main density peak to an additional nearby structure. For a subsample of our most cleanly measured clusters, we investigated the statistical relation between their weak-lensing mass ($M_{\rm NFW}$, $\sigma_{\rm SIS}$) and the velocity dispersion of their member galaxies ($\sigma_{v}$), comparing our sample with optically and X-ray selected samples from the literature. Our lensing-selected clusters are consistent with $\sigma_v$$=$$\sigma_{\rm SIS}$, with a similar scatter to that of optically and X-ray selected clusters. We also derived an empirical relation between the cluster mass and the galaxy velocity dispersion, $M_{200}E$($z$) $=$ 11.0 $\times$ 10$^{14}$$\times$ ($\sigma_v/$1000 kms$^{-1}$)$^{3.0}h^{-1}M_\odot$, which is in reasonable agreement with predictions of $N$-body simulations in the $\Lambda$CDM cosmology.
Discovery of Molecular Loop 3 in the Galactic Center: Evidence for a Positive-Velocity Magnetically Floated Loop towards L
= 355$^\circ$–359$^\circ$
Authors: Fujishita Motosuji , Torii Kazufumi , Kudo Natsuko , Kawase Tokuichi , Yamamoto Hiroaki , Kawamura Akiko , Mizuno Norikazu , Onishi Toshikazu , Mizuno Akira , Machida Mami , Takahashi Kunio , Nozawa Satoshi , Matsumoto Ryoji , Fukui Yasuo
Published: March 2014

We have discovered a molecular dome-like feature towards 355$^{\circ}$$\leq$$l$$\leq$ 359$^{\circ}$ and 0$^{\circ}$$\leq$$b$$\leq$ 2$^{\circ}$. The large velocity dispersions of 50–100 km s$^{-1}$ of this feature are much larger than those in the Galactic disk, and indicate that the feature is located in the Galactic center, probably within $\sim $1 kpc of Sgr A$^{\ast}$. The distribution has a projected length of $\sim $600 pc and a height of $\sim $300 pc from the Galactic disk, and shows a large-scale monotonic velocity gradient of $\sim $130 km s$^{-1}$ per $\sim $600 pc. The feature is also associated with HI gas having a more continuous spatial and velocity distribution than that of ${}^{12}$CO. We interpret the feature as being a magnetically floated loop similar to loops 1 and 2, and name it “loop 3”. Loop 3 is similar to loops 1 and 2 in its height and length, but is different from loops 1 and 2 in that the inner part of loop 3 is filled with molecular emission. We have identified two foot points at both ends of loop 3. HI, ${}^{12}$CO, and ${}^{13}$CO datasets were used to estimate the total mass and the kinetic energy of loop 3 to be $\sim $3.0 $\times$ 10$^{6} M_\odot$ and $\sim $1.7 $\times$ 10$^{52} $erg. The huge size, velocity dispersions, and energy are consistent with the magnetic origin of the Parker instability, as in the case of loops 1 and 2, but is difficult to be explained by multiple stellar explosions. We argue that loop 3 is in an earlier evolutionary phase than loops 1 and 2 based on the inner-filled morphology and the relative weakness of the foot points. This discovery indicates that the western part of the nuclear gas disk of $\sim $1 kpc radius is dominated by the three well-developed magnetically floated loops, and suggests that the dynamics of the nuclear gas disk is strongly affected by magnetic instabilities.
Thermally Driven Winds from Radiatively Inefficient Accretion Flows
Authors: Kawabata Ryoji , Mineshige Shin
Published: March 2014

Radiatively inefficient accretion flows (RIAFs) are a common feature of low-luminosity accretion flows, including quiescent states of X-ray binaries and low-lunimosity active galactic nuclei. Thermally driven winds are expected from such hot accretion flows. By assuming that the flow has a self-similarity structure in the radial direction, we solved the vertical structure of the wind and accretion flows simultaneously and evaluated the mass loss rates by wind. We have found that the ratio of the outflow rate to the accretion rate is approximately unity for a viscosity parameter of $\alpha $$\lesssim$ 0.1, despite some uncertainties in the angular momentum and temperature distributions. That is, the accretion rate in the RIAFs is roughly proportional to the radius. Moreover, we elucidated the effect of cooling by wind on the underneath accretion flow, finding that this effect could be important for calculating the energy spectrum of the RIAF. Observational implications are briefly discussed in the context of Sgr A$^\ast$.
Implications of Bulk Velocity Structures in AGN Jets
Authors: Yang Jianping , Wang Jiancheng , Dai Benzhong , Gao Xiaoyan
Published: March 2014

Synchrotron self-Compton (SSC) models and External Compton (EC) models of AGN jets with continually longitudinal and transverse bulk velocity structures have been constructed. The observed spectra show complex and interesting patterns in different velocity structures and viewing angles. These models were used to calculate the synchrotron and inverse Compton spectra of two typical BL Lac objects (BLO) (Mrk 421 and 0716$+$714) and (one) Flat Spectrum Radio Quasars (FSRQs) (3C 279), and to discuss the implications of jet bulk velocity structures in a unification of the BLO and FR I radio galaxies (FRI). By calculating the synchrotron spectra and SSC spectra of BL Lac object jets with continually bulk velocity structures, we have found that the spectra are much different from those in jets with a uniform velocity structure under increasing viewing angles. The unification of BLO and FRI is less constrained by the viewing angles, and would be imprinted by velocity structures intrinsic to the jets, themselves. By considering jets with bulk velocity structures constrained by the apparent speed, we discuss the velocity structures imprinted on the observed spectra for different viewing angles. We find that the spectra are greatly impacted by longitudinal velocity structures, because the volume elements are compressed or expanded. Finally, we present the EC spectra of FSRQs and FR II radio galaxies (FRII), and find that they are weakly affected by the velocity structures compared to synchrotron and SSC spectra.
A Massive Disk Galaxy at z$>$ 3 along the Line of Sight of QSO 1508$+$5714
Authors: Wang Yiping , Yamada Toru , Tanaka Ichi , Iye Masanori
Published: March 2014

We have obtained deep images in the BVRIJHKs bands of the field centered on QSO 1508$+$5714 ($z_{\rm em}$$=$ 4.28) with the Suprime-Cam, FOCAS, and MOIRCS cameras on Subaru telescope. We report here on the detection of a $B$-dropout galaxy, which is 3${\rlap{\hskip.75pt{^{\prime\prime}}}\hskip.75pt.\hskip1.75pt}$5 north-west of the QSO sightline. A photometric redshift analysis is presented to complement the color selection. Given the photometric properties of this object ($M$$=$$-$22.2, making $L$$\approx$ 3$ L^{\ast}$, if placed at its photometric redshift, $z$$\sim$ 3.5), as well as the Sérsic index ($n$$\sim$ 1) derived from a 2-D imaging decomposition of the HST WFPC2 image taken with the $I_{\mathit{F814}}$ filter, the identified system is consistent with a massive disk galaxy at $z > $ 3. If confirmed, it would be one of the most distant massive disk galaxies known so far.
Suzaku X-Ray Imaging and Spectroscopy of Cassiopeia A
Authors: Maeda Yoshitomo , Uchiyama Yasunobu , Bamba Aya , Kosugi Hiroko , Tsunemi Hiroshi , Helder Eveline A. , Vink Jacco , Kodaka Natsuki , Terada Yukikatsu , Fukazawa Yasushi , Hiraga Junko , Hughes John P. , Kokubun Motohide , Kouzu Tomomi , Matsumoto Hironori , Miyata Emi , Nakamura Ryoko , Okada Shunsaku , Someya Kentaro , Tamagawa Toru , Tamura Keisuke , Totsuka Kohta , Tsuboi Yohko , Ezoe Yuichiro , Holt Stephen S. , Ishida Manabu , Kamae Tsuneyoshi , Petre Robert , Takahashi Tadayuki
Published: March 2014

Suzaku X-ray observations of a young supernova remnant, Cassiopeia A, were carried out. K-shell transition lines from highly ionized ions of various elements were detected, including Chromium (Cr-K$\alpha $ at 5.61 keV). The X-ray continuum spectra were modeled in the 3.4–40 keV band, summed over the entire remnant, and were fitted with a simplest combination of the thermal bremsstrahlung and the non-thermal cut-off power-law models. The spectral fits with this assumption indicate that the continuum emission is likely to be dominated by non-thermal emission with a cut-off energy at $> $1 keV. The thermal-to-nonthermal fraction of the continuum flux in the 4–10 keV band is best estimated as $\sim $0.1. Non-thermal-dominated continuum images in the 4–14 keV band were made. The peak of the non-thermal X-rays appears at the western part. The peak position of the TeV $\gamma$-rays measured with HEGRA and MAGIC is also shifted at the western part with the 1-sigma confidence. Since the location of the X-ray continuum emission was known to be presumably identified with the reverse shock region, the possible keV–TeV correlations give a hint that the accelerated multi-TeV hadrons in Cassiopeia A are dominated by heavy elements in the reverse shock region.
Iron Emission Lines on the Galactic Ridge Observed with Suzaku
Authors: Yamauchi Shigeo , Ebisawa Ken , Tanaka Yasuo , Koyama Katsuji , Matsumoto Hironori , Yamasaki Noriko Y. , Takahashi Hiromitsu , Yuichiro Ezoe
Published: March 2014

In order to elucidate the origin of galactic ridge X-ray emission, we analyzed Suzaku data taken at various regions along the galactic plane, and studied their Fe-K emission line features. Suzaku resolved the Fe line complex into three narrow lines at $\sim$ 6.4 keV, $\sim$ 6.7 keV and $\sim$ 6.97 keV, which are K-lines from neutral (or low-ionized), He-like, and H-like iron respectively. The 6.7 keV line is clearly seen in all of the observed regions, and its longitudinal distribution is consistent with that determined from previous observations. The 6.4 keV emission line was also found in various galactic plane regions ($b\sim0^{\circ}$). Differences in the flux ratios of the 6.4 keV$/$6.7 keV and 6.97 keV$/$6.7 keV lines between the galactic plane and the galactic center regions were studied and its implication was discussed.