bluuebunny/crossref_metadata_2025 huggingface dataset:
Suzaku Detection of an Intense X-Ray Flare from an A-Type Star, HD161084
Authors: Miura Junichiro , Tsujimoto Masahiro , Tsuboi Yohko , Maeda Yoshitomo , Sugawara Yasuharu , Koyama Katsuji , Yamauchi Shigeo
Published: March 2014

We report on a serendipitous detection of an intense X-ray flare from the Tycho reference source on HD161084 during a Suzaku observation of the galactic center region for $\sim$20ks. The X-ray Imaging Spectrometer recorded a flare from this A1-type dwarf or subgiant star with a flux of $\sim$1.4$\times$10$^{-12}$erg s$^{-1}$ cm$^{-2}$ (0.5-10keV) and a decay time scale of $\sim$0.5hr. The spectrum is hard with a prominent FeXXV K$\alpha$ emission line at 6.7keV, which is explained by a $\sim$5keV thin-thermal plasma model attenuated by a $\sim$1.4$\times$10$^{21}$cm$^{-2}$ extinction. The low extinction, which is consistent with the optical reddening, indicates that the source is a foreground star toward the galactic center region. Based on a spectroscopic parallax distance of $\sim$530pc, the peak X-ray luminosity amounts to $\sim$1$\times$10$^{32}$erg s$^{-1}$ (0.5-10keV). This is much larger than the X-ray luminosity of ordinary late-type main-sequence stars, and the X-ray emission is unattributable to a hidden late-type companion that comprises a wide binary system with the A star. We discuss possible nature of HD161084, and suggest that it is most likely an interacting binary with elevated magnetic activity in the companion, such as the Algol-type system. The flux detected by Suzaku during the burst is $\sim$100-times larger than the quiescent level measured using the archived XMM-Newton and Chandra data. The large flux amplification makes this star a unique example among sources of this class.
Suzaku Spectroscopy of Extended X-Ray Emission in M17
Authors: Hyodo Yoshiaki , Tsujimoto Masahiro , Hamaguchi Kenji , Koyama Katsuji , Kitamoto Shunji , Maeda Yoshitomo , Tsuboi Yohko , Ezoe Yuichiro
Published: March 2014

We present the results of a Suzaku spectroscopic study of soft extended X-ray emission in the HII region of M17. The spectrum of the extended emission was obtained with a high signal-to-noise ratio in a spatially resolved manner using the X-ray Imaging Spectrometer (XIS). We established that contamination by unresolved point sources, the Galactic Ridge X-ray emission, the cosmic X-ray background, and the local hot bubble emission is negligible in the background-subtracted XIS spectrum of the diffuse emission. Half a dozen emission lines were clearly resolved for the first time, including K$\alpha$ lines of highly ionized O, Ne, and Mg as well as L-series complex of Fe at 0.5-1.5keV. Based on diagnosis of these lines, we obtained the following results: (1) the extended emission is an optically thin thermal plasma, represented well by a single temperature of $\sim$3.0$\pm$0.4MK, (2) the abundances of elements with emission lines in the diffuse spectrum are 0.1-0.3 solar, while those of bright discrete sources are 0.3-1.5 solar, (3) the metal abundances relative to each other in the diffuse emission are consistent with solar, except for a Ne enhancement of a factor of $\sim$2, (4) both the plasma temperature and the chemical composition of the diffuse emission show no spatial variation across the studied spatial scale of $\sim$5pc.
Performance of an Imaging Fourier Transform Spectrometer with Photoconductive Detector Arrays: An Application for the AKARI Far-Infrared Instrument
Authors: Kawada Mitsunobu , Takahashi Hidenori , Murakami Noriko , Matsuo Hiroshi , Okada Yoko , Yasuda Akiko , Matsuura Shuji , Shirahata Mai , Doi Yasuo , Kaneda Hidehiro , Ootsubo Takafumi , Nakagawa Takao , Shibai Hiroshi
Published: March 2014

We have developed an imaging Fourier transform spectrometer (FTS) for space-based far-infrared astronomical observations. The FTS employs newly developed photoconductive detector arrays with a capacitive trans-impedance amplifier, which makes the FTS a completely unique instrument. The FTS was installed as a function of the far-infrared instrument (FIS: Far-Infrared Surveyor) aboard the Japanese astronomical satellite, AKARI, which was launched on 2006 February 21 (UT) from Uchinoura Space Center. The FIS-FTS had been operated for more than one year before liquid helium ran out on 2007 August 26. The FIS-FTS was operated nearly six hundreds times, which corresponds to more than one hundred hours of astronomical observations and almost the same amount of time for calibrations. As expected from laboratory measurements, the FIS-FTS performed well and has produced a large set of astronomical data for valuable objects. Meanwhile, it has become clear that the detector transient effect is a considerable factor for FTSs with photoconductive detectors. In this paper, the instrumentation of the FIS-FTS and interesting phenomena related to FTS using photoconductive detectors are described, and future applications of this kind of FTS system are discussed.
An AKARI Search for Intracluster Dust of Globular Clusters
Authors: Matsunaga Noriyuki , Mito Hiroyuki , Nakada Yoshikazu , Fukushi Hinako , TanabÉ Toshihiko , Ita Yoshifusa , Izumiura Hideyuki , Matsuura Mikako , Ueta Toshiya , Yamamura Issei
Published: March 2014

We report on observations of 12 globular clusters with the Far-Infrared Surveyor (FIS) aboard the AKARI satellite. Our goal is to search for emission from cold dust within clusters. We detected diffuse emissions toward NGC6402 and 2808, but the IRAS 100$\mu$m maps show the presence of strong background radiation. They are likely to have been emitted from the Galactic cirrus. We also detected 28 point-like sources mainly in WIDE-S images (90$\micron$). At least several of them are not associated with clusters, but background galaxies identified in external catalogs. We present the spectral energy distributions (SEDs) by combining near-and-mid infrared data obtained with the Infrared Camera (IRC), if possible. Those SEDs suggest that most of the point sources are background galaxies. For most of the other clusters, we have confirmed a lack of intracluster dust. We evaluated the upper limits of the intracluster dust mass to be between 10$^{-5}$ and 10$^{-3}\MO$, depending on the dust temperature. The inferred lifetime of the intracluster dust is shorter than 5Myr ($T_{\mathrm{d}}$$=$ 70K) or 50Myr (35K). Such a short lifetime indicates some mechanism(s) are at work to remove the intracluster dust. We also discuss its impact on the chemical evolution of globular clusters.
Spatial Distributions of Dust and Polycyclic Aromatic Hydrocarbons in the Nearby Elliptical Galaxy NGC4589 Observed with AKARI
Authors: Kaneda Hidehiro , Suzuki Toyoaki , Onaka Takashi , Okada Yoko , Sakon Itsuki
Published: March 2014

We report on near- to far-infrared (IR) observations of the nearby elliptical galaxy NGC4589 by AKARI. NGC4589 has a complex stellar rotation field with a position angle difference of 45$^{\circ}$ between the kinematic and morphological axes, although its morphology shows a smooth optical profile that closely follows the de Vaucouleurs law. The galaxy has a minor-axis dust lane, which is twisted toward the main stellar rotation. These properties strongly support that the galaxy is a relatively old merger remnant. We have obtained the spatial distributions of dust from far-IR emission and near-IR absorption, separately. We have also estimated the distribution of polycyclic aromatic hydrocarbons (PAHs) from the difference between images in the mid-IR bands. The spatial distributions of the dust and PAHs resemble each other, both showing significant deviations from the smooth stellar distribution. They extend to the main stellar rotation and the direction of the twisted inner dust lane, thus following the relics of the merger. Therefore, a large fraction of the dust and PAHs in NGC4589 are likely to originate from a past merger event.
Systematic Infrared 2.5—5μm Spectroscopy of Nearby Ultraluminous Infrared Galaxies with AKARI
Authors: Imanishi Masatoshi , Nakagawa Takao , Ohyama Yoichi , Shirahata Mai , Wada Takehiko , Onaka Takashi , Oi Nagisa
Published: March 2014

We report on the results of systematic infrared 2.5-5$\mu$m spectroscopy of 45 nearby ultraluminous infrared galaxies (ULIRGs) at $z \lt$ 0.3 using AKARI IRC. This paper investigates whether the luminosities of these ULIRGs are dominated by starburst activity, or alternatively, whether optically elusive buried active galactic nuclei (AGNs) are energetically important, based on the strengths of 3.3$\mu$m polycyclic aromatic hydrocarbon (PAH) emission and dust absorption features at 3-4$\mu$m. Because of the AKARI IRC's spectroscopic capability in the full 2.5-5$\mu$m wavelength range, we can apply this energy diagnostic method to ULIRGs at $z\gt$ 0.15. We estimate the intrinsic luminosities of extended (several kpc), modestly obscured ($A_{V} \lt$ 15mag) starburst activity based on the observed 3.3$\mu$m PAH emission luminosities measured in AKARI IRC slitless spectra, and confirm that such starbursts are energetically unimportant in nearby ULIRGs. In roughly half of the observed ULIRGs classified optically as non-Seyferts, we find signatures of luminous buried AGNs. The fraction of ULIRGs with detectable buried AGN signatures increases with increasing infrared luminosity. Our overall results support the scenario that luminous buried AGNs are important in many ULIRGs at $z \lt$ 0.3 classified optically as non-Seyferts, and that the optical undetectability of such buried AGNs occurs merely because of a large amount of nuclear dust, which can make the sightline of even the lowest dust column density opaque to the ionizing radiation of the AGNs.
Galaxy Clusters at 0.9 < z < 1.7 in the AKARI NEP Deep Field
Authors: Goto Tomotsugu , Hanami Hitoshi , Im Myungshin , Imai Koji , Inami Hanae , Ishigaki Tsuyoshi , Mok Lee Hyung , Matsuhara Hideo , Nakagawa Takao , Ohyama Youichi , Oyabu Shinki , Pearson Chris P. , Takagi Toshinobu , Wada Takehiko
Published: March 2014

There is a huge gap between the properties of red-sequence selected massive galaxy clusters at $z\lt1$ and Lyman-break selected proto-clusters at $z\gt3$. It is important to understand when and how the $z\gt3$ proto-clusters evolve into passive clusters at $z\lt1$. We aim to fill this cluster desert by using space-based N4 (4$\mu$m) imaging with AKARI. The $z'-$N4 color is a powerful separator of cluster galaxies at $z$$\gt$ 1, taking advantage of the 4000Å break and the 1.6$\mu$m bump. We carefully selected 16 promising cluster candidates at 0.9 $\lt$$z$$\lt$ 1.7, which all show an obvious over-density of galaxies and a prominent red-sequence. At this redshift range, the mid-infrared $S_{15\micron}/S_{9\micron}$ flux ratio is an extinction-free indicator of galaxy star-formation activity due to the redshifted PAH emission lines (6.2, 7.7, and 8.6$\mu$m). We show statistically that the cluster galaxies have a lower $S_{15\micron}/S_{9\micron}$ flux ratio than do field galaxies, i.e., cluster galaxies already have lower star-formation activity at 0.9 $\lt$$z$$\lt$ 1.7, pushing the formation epoch of these galaxy clusters to a higher redshift.
Identification of Potential Weak Target Radio Quasars for ASTRO-G In-Beam Phase-Referencing
Authors: Frey Sándor , GabÁnyi Krisztina Éva , Asaki Yoshiharu
Published: March 2014

We apply an efficient selection method to identify potential weak Very Long Baseline Interferometry (VLBI) target quasars simply using optical (SDSS) and low-resolution radio (FIRST) catalogue data. Our search is restricted to within 12 from known compact radio sources that are detectable as phase-reference calibrators for ASTRO-G at 8.4 GHz frequency. These calibrators have estimated correlated flux density $>$20 mJy on the longest ground–space VLBI baselines. The search radius corresponds to the primary beam size of the ASTRO-G antenna. We show that $\sim$20 quasars with at least mJy-level expected flux density can be pre-selected as potential in-beam phase-reference targets for ASTRO-G at 8.4 GHz frequency. Most of them have never been imaged with VLBI. The sample of these dominantly weak sources offers a good opportunity to study their radio structures with unprecedented angular resolution provided by Space VLBI. The method of in-beam phase-referencing is independent from the ability of the orbiting radio telescope to do rapid position-switching manoeuvres between the calibrators and the nearby reference sources, and less sensitive to the satellite orbit determination uncertainties.
A Large-Scale 13CO Mapping of the W 49 A Molecular Cloud Complex
Authors: Miyawaki Ryosuke , Hayashi Masahiko , Hasegawa Testuo
Published: March 2014

We present $^{13}$CO ($J$$=$ 1-0) and C$^{18}$O ($J$$=$ 1-0) maps of the W 49 A molecular cloud complex observed at a resolution of 17$''$ (HPBW). Fourteen features (MHH-1 to MHH-14) were identified in the $^{13}$CO velocity channel maps, most of them distributed within an area of 6$'$ (20 pc) in diameter with their total mass amounting to 1.7 $\times$ 10$^{6}M_\odot$. The features have a three-dimensional velocity dispersion of 8 km s$^{-1}$, which leads to a mean free time per feature of 10$^{6}$yr. This suggests that they are interacting one another in a region of $\sim$20 pc in diameter. The feature MHH-1, which corresponds to W 49 N, is unique in that it exhibits a large velocity width (15 km s$^{-1}$ FWHM) and is compact in size (2.3 pc $\times$ 3.0 pc FWHM), while containing a large mass of 2.4 $\times$ 10$^{5}M_\odot$. This indicates that the free-fall time of MHH-1 is on the order of 10$^{5}$yr, an order of magnitude smaller than that of the entire complex. It has turned out that MHH-1 has a smaller spatial width at $V_{\rm LSR}$$\lesssim$ 8 km s$^{-1}$ than at $\gtrsim$8 km s$^{-1}$. This result, together with the line-profile characteristics of various optically thin lines, suggests that at least two massive clouds with different radial velocities exist toward MHH-1. The massive compact feature may have been produced by the interaction of the two different velocity clouds.
A New Mechanism for Massive Binary Black-Hole Evolution
Authors: Hayasaki Kimitake
Published: March 2014

It is still unknown how a binary black hole (BBH) evolves after its semi-major axis has reached the sub-parsec scale, where dynamical friction with neighboring stars is no longer effective (the so-called final-parsec problem). In this paper, we propose a new mechanism by which a massive BBH can naturally coalesce within a Hubble time. We consider the evolution of a BBH with a triple disk composed of an accretion disk around each black hole and one circumbinary disk surrounding them. While the circumbinary disk removes the orbital angular momentum of the BBH via a binary-disk resonant interaction, the mass transfer from the circumbinary disk to each black hole adds some fraction of its angular momentum to the orbital angular momentum of the BBH. We find that there is a critical value of the mass-transfer rate where extraction of the orbital angular momentum from the BBH is balanced with the addition of orbital angular momentum to the BBH. The semi-major axis of the BBH decays with time, whereas the orbital eccentricity of the BBH grows with time, if the mass-transfer rate is smaller than the critical one, and vice versa. Its evolutionary timescale is characterized by the product of the viscous timescale of the circumbinary disk and the ratio of the total black-hole mass to the mass of the circumbinary disk. Most massive BBHs are able to merge within a Hubble time by the proposed mechanism, which helps to solve the final parsec problem.
Correlations between Flare Parameters and Magnetic Parameters in Solar Flares
Authors: Yamamoto Tetsuya T. , Sakurai Takashi
Published: March 2014

We investigated correlations between flare parameters and magnetic parameters by picking up the largest and smaller flares in each sample region. The flare parameters that we used were the X-ray peak flux, characteristic duration time, and X-ray energy. These values were derived from Geostationary Operational Environmental Satellites (GOES) X-ray light curves (1–8Å). The magnetic parameters used were the averaged longitudinal field strength, averaged shear field strength, and characteristic length of flare ribbons. These magnetic parameters were derived from flaring areas. We used vector magnetograms obtained with the Solar Flare Telescope (National Astronomical Observatory of Japan) and SoHO/MDI (Michelson Doppler Imager) magnetograms. In this paper the regionally largest flare is defined as the flare whose X-ray peak flux exceeds one-fifth of the X-ray peak flux of the most intense flare in each region, and all the other flares are defined as smaller flares. From 1997 to 2003, we selected 20 flares as the regionally largest flares and 15 flares as smaller flares. We found that the X-ray peak flux of the regionally largest flares has definite correlations with the magnetic parameters, and the characteristic duration time has a definite correlation only with the characteristic length of flare ribbons. The regionally largest flares and smaller flares show different relations between the flare parameters and the magnetic parameters. They show, on the other hand, a single relation between the X-ray energy and the magnetic free energy index derived from the photospheric magnetic parameters.
Proper Motions with Subaru I. Methods and a First Sample in the Subaru Deep Field
Authors: Richmond Michael W. , Morokuma Tomoki , Doi Mamoru , Komiyama Yutaka , Yasuda Naoki , Okamura Sadanori , Gal-Yam Avishay
Published: March 2014

We search for stars with proper motions in a set of twenty deep Subaru images, covering about 0.28 square degrees to a depth of $i^\prime$$\simeq$ 25, taken over a span of six years. In this paper, we describe in detail our reduction and techniques to identify moving objects. We present a first sample of 99 stars with motions of high significance, and discuss briefly the populations from which they are likely drawn. Based on photometry and motions alone, we expect that 9 of the candidates may be white dwarfs. We also find a group of stars which may be extremely metal-poor subdwarfs in the halo.
Pseudo Rotation Curve Connecting the Galaxy, Dark Halo, and Local Group
Authors: Sofue Yoshiaki
Published: March 2014

We construct a Galacto-Local Group rotation curve, combining the Galactic rotation curve with a diagram, where the galacto-centric radial velocities of the outer globular clusters and the member galaxies of the Local Group are plotted against their galacto-centric distances. The high-velocity ends of this pseudo rotation curve within a radius of $R$$\sim$ 150 kpc are well traced by a rotation curve calculated for the NFW (Navaro, Frenk, White) and Burkert dark halo models. The NFW model indicates that the Galaxy’s mass within 385 kpc, half the distance to M 31, is $\sim$4$\times$10$^{11}M_\odot$. High-velocity ends of the pseudo rotation curve for the entire Local Group up to 1.5 Mpc indicate an isothermal nature with a terminal velocity of $\sim$200 kms$^{-1}$. In order for the Local Group to be gravitationally bound, an order-of-magnitude larger mass than those of the Galaxy and M 31 is required. This fact suggests that the Local Group contains dark matter of mass $\sim$5$\times$10$^{12}M_\odot$, filling the space between the Galaxy and M 31. The mass density of the Galactic dark halo becomes equal to that of the Local Group’s dark matter at $R$$\sim$ 100 kpc, beyond which the intracluster dark matter dominates. If we define the Galaxy’s radius at this distance, the enclosed Galactic mass is $\sim$3$\times$10$^{11}M_\odot$.
Deep 15 $\mu$m AKARI Observations in the CDFS: Estimating Dust Luminosities for a MIR-Selected Sample and for Lyman Break Galaxies and the Evolution of LdustLUV with the Redshift
Authors: Burgarella Denis , Buat Véronique , Takeuchi Tsutomu T. , Wada Takehiko , Pearson Chris
Published: March 2014

Deep observations of the Chandra Deep Field South have been secured at 15$\mu$m with AKARI/IRC infrared space telescope. From these observations, we define a sample of mid infrared-selected galaxies at 15$\mu$m and we also obtain 15$\mu$m flux densities for a sample of Lyman Break Galaxies at $z$$\sim $ 1 already observed at 24$\mu$m with Spitzer/MIPS. Number counts for the mid infrared-selected sample show a bump around a 15$\mu$m flux density of 0.2 mJy that can be attributed to galaxies at $z$$\gt$ 0.4 and at $z$$\gt$ 0.8 for the fainter part of the bump. This bump seems to be shifted as compared to other works and a possible origin can be the Cosmic variance. On the two above samples at $z$$\sim $ 1 we have tested the validity of the conversions from luminosities $\nu f_{\nu}$ at 8$\mu$m to total dust luminosities by comparing with luminosities estimated from 12$\mu$m data used as a reference. Some calibrations seem better when compared to $L_{\rm dust}$ evaluated from longer wavelength luminosities. We also find that the rest-frame 8$\mu$m luminosities provide good estimates of $L_{\rm dust}$. By comparing our data to several libraries of spectral energy distributions, we find that models can explain the diversity of the observed $f_{24} / f_{15}$ ratio quite reasonably. However, when we analyse the luminosity dependence of this ratio, we find important discrepancies. Finally, we revisit the evolution of $L_{\rm dust} / L_{\rm UV}$ ratio with the redshift $z$ by re-calibrating previous $L_{\rm dust}$ at $z$$\sim $ 2 based on our results and added new data points at higher redshifts. The decreasing trend is amplified as compared to the previous estimate.
No Evidence for Variability of Intervening Absorption Lines toward GRB 060206: Implications for the Mg ii Incidence Problem
Authors: Aoki Kentaro , Totani Tomonori , Hattori Takashi , Ohta Kouji , Kawabata Koji S. , Kobayashi Naoto , Iye Masanori , Nomoto Ken’ichi , Kawai Nobuyuki
Published: March 2014

We examined the variability of absorption line strength of intervening systems along the line of sight to GRB 060206 at z$=$ 4.05, utilizing low-resolution optical spectra obtained by the Subaru telescope from six to ten hours after the burst. Strong variabilities of Fe ii and Mg ii lines at z$=$ 1.48 during $t$$=$ 5–8 hr have been reported for this GRB, and those have been used to support the idea of clumpy Mg ii cloudlets, which was originally proposed to explain the anomalously high incidence of Mg ii absorbers in the GRB spectra compared to quasars. However, our spectra with a higher signal-to-noise ratio do not show any evidence for variability in $t$$=$ 6–10 hr. There is a clear discrepancy between our data and those of Hao et al. (2007, ApJ, 659, L99) in the overlapping time interval. Furthermore, the line strengths in our data are in agreement with those observed at $t$$\sim$ 2 hr by Thöne et al. (2008, A&A, 489, 37). We also detected Fe ii and Mg ii absorption lines for a system at z$=$ 2.26; these lines do not show evidence for variability either. Therefore, we conclude that there is no strong evidence for the variability in the intervening absorption lines toward GRB 060206, offering poor support for the Mg ii cloudlet hypothesis by the GRB 060206 data.
Two Types of Magnetohydrodynamic Sheath Jets
Authors: Kaburaki Osamu
Published: March 2014

Recent observations of astrophysical jets emanating from various galactic nuclei strongly suggest that a double-layered structure, or a spine-sheath structure, is likely to be their common feature. We propose that such a sheath jet structure can be formed magnetohydrodynamically within a valley of the magnetic pressures, which is formed between the peaks due to the poloidal and toroidal components, with the centrifugal force acting on the rotating sheath plasma being balanced by the hoop stress of the toroidal field. The poloidal field concentrated near the polar axis is maintained by a converging plasma flow toward the jet region, and the toroidal field is developed outside the jet cone owing to the poloidal current circulating through the jet. Under such situations, the set of magnetohydrodynamic (MHD) equations allows two main types of solutions, at least, in the region far from the footpoint. The first type solution describes the jets of marginally bound nature. This type is realized when the jet temperature decreases like a virial one, and neither the pressure-gradient nor the MHD forces, which are both determined consistently, cannot completely overcome the gravity, even at infinity. The second type is realized under an isothermal situation, and the gravity is cancelled exactly by the pressure-gradient force. Hence, the jets of this type are accelerated purely by the MHD force. It is also suggested that these two types correspond, respectively, to the jets from type I and II radio galaxies in the Fanaroff-Riley classification.
Beam Pattern Measurements and Observational Evaluations of the ALMA/ACA 12-m Antenna
Authors: Sugimoto Masahiro , Kosugi George , Iguchi Satoru , Iwashita Hiroyuki , Saito Masao , Inatani Junji , Takahashi Toshikazu , Tasaki Masahiko , Nakanishi Kouichiro , McMullin Joseph P. , Puga Jose Pablo , Hoff Brian , Norambuena Jorge , Kamazaki Takeshi , Vila-Vilaró Baltasar , Ikenoue Bungo , Morita Koh-Ichiro , Asayama Shin’ichiro , Yamada Masumi , Kiuchi Hitoshi
Published: March 2014

We have evaluated the beam pattern of the ALMA/ACA 12-m antenna with total power observations of Jupiter and the Moon. Models of the expected beam pattern as it passes across Jupiter and the Moon were derived in consideration of the radiation pattern of the actual receiving system and the surface error of the main reflector. Since the profiles of the measured beam patterns were consistent with those of the models within the range from the peak to $-$20 dB, we confirmed that the antenna achieved the beam pattern expected from its optical design. After this confirmation, we performed astronomical observations. In addition to the detection of the CS $J$$=$ 3–2 (146.969026 GHz) spectrum toward Orion KL, the change in the Moon intensity was successfully detected during the total lunar eclipse during 2008 February 20–21. A time lag longer than 10 min in the millimeter-wave eclipse relative to the corresponding optical eclipse ephemeris was detected. Mapping observations of the Sun revealed the structure of the chromospheric networks at 147 GHz. These astronomical observations confirmed that the ACA 12-m antenna could be successfully operated under various operating conditions.
A Large Expanding Molecular Arc in the Sagittarius B1 Complex
Authors: Tanaka Kunihiko , Oka Tomoharu , Nagai Makoto , Kamegai Kazuhisa
Published: March 2014

Results of molecular line observations toward the Sagittarius B1 complex are reported. Maps of the HCN, HCO$^+$ and SiO J$=$ 1–0 emissions were taken with the NRO 45-m telescope. With these data, combined with the ASTE CO J$=$ 3–2 survey data, we have investigated the spatial structure, kinematics and physical conditions of two peculiar molecular features: CO0.55$+$0.07 and SiO0.56$-$0.01. The CO arc, CO0.55$+$0.07, shows clear expanding motion with sizes of 8.5 $\times$ 6.8 pc$^2$ and an expansion velocity of 40 km s$^{-1}$. The SiO shell, SiO0.56$-$0.01, has a size of 3.0 $\times$ 3.4 pc$^2$, and surrounds an X-ray Fe line source, G0.570$-$0.018. The mass and the kinetic energy of CO0.55$+$0.07 are estimated to be 10$^{5.5}{M_\odot}$ and 10$^{51.5}$erg, respectively. The kinetic energy of SiO0.56$-$0.01 is $\sim$10$^{50.4}$erg. An LVG analysis shows that the typical density and kinetic temperature are 10$^{3.8}$cm$^{-3}$ and 28 K, respectively. High-density clumps with a density of 10$^{4.0{-}4.5}$cm$^{-3}$ associated with CO0.55$+$0.07 and SiO0.56$-$0.01 have been found, supporting the idea that they consist of swept-up material. The huge kinetic energy of CO0.55$+$0.07 is considered to be injected by a series of supernova explosions that took place within $\sim$2 $\times$ 10$^{5}$yr, which would suggest that it is a ‘bubble’ created by a massive stellar cluster, whose mass is estimated to be 10$^{3.5{-}4.5}{M_\odot}$. The origin of SiO0.56$-$0.01 is rather unclear, but we suggest that it could be related to the X-ray source G0.570$-$0.018.
An Orbital Period Investigation of the Solar-Type Overcontact Binary V700 Cygni
Authors: Xiang Fuyuan , Tian Yongpo , Tao Xia , Xie Wenli
Published: March 2014

Orbital period changes of the solar-type contact binary V700 Cyg were investigated based on one new eclipse time combined with the others collected from the literature. A cyclic oscillation, with a period of 39.1 yr and an amplitude of 0.$^{\rm d}$0197, was found to be superimposed on a secular period increase at a rate of $dP/dt$$=$$+$2.8 $\times$ 10$^{-8}{\rm d}$ yr$^{-1}$. Weak evidence indicates that there exists another small-amplitude period oscillation. The long-term period increase is in agreement with the conclusion that high-mass ratio W-type overcontact binaries usually show period increasing. This suggests that it may be in the stage controlled by thermal relaxation oscillations. Cyclic period oscillation can be explained as being the result of a light-travel time effect via the presence of an additional body. On the other hand, since both components of V700 Cyg are late-type stars, the period oscillation may be evidence of magnetic activity cycles of the two component stars.
CCD Photometry of a Newly Confirmed SU UMa-Type Dwarf Nova, NSV 4838
Authors: Imada Akira , Yasuda Tatsuki , Omodaka> Toshihiro , Oizumi Shota , Yamamoto Hiroyuki , Tanada Shunsuke , Arao Yoshihiro , Kodama Kie , Suzuki Miho , Matsuo Takeshi , Maehara Hiroyuki , Kato Taichi , Sugiyasu Kei , Moritani Yuuki , Sumiyoshi Masanao , Nakajima Kazuhiro , Pietz Johen , Yanagisawa Kenshi , Nogami Daisaku
Published: March 2014

We present time-resolved CCD photometry of a dwarf nova, NSV 4838 (UMa 8, SDSS J102320.27$+$440509.8), during 2005 June and 2007 February outbursts. The two light curves showed superhumps with mean periods of 0.0699(1)d for the 2005 outburst and 0.069824(83)d for the 2007 outburst. Using its known orbital period of 0.0678 d, we estimated the mass ratio of the system to be $q$$=$ 0.13 based on an empirical relation. Although the majority of SU UMa-type dwarf novae having similar superhump periods show negative period derivatives, we found that the superhump period increased at $\dot{P}/P_{\rm sh}$$=$$+$7($+$3, $-$4) $\times$ 10$^{-5}$ during the 2007 superoutburst. We also investigated long-term light curves of NSV 4838, from which we derived 340 d as a supercycle of this system.
Suzaku Observation Adjacent to the South End of the Radio Arc
Authors: Fukuoka Ryosuke , Koyama Katsuji , Ryu Syukyo G. , Tsuru Takeshi Go
Published: March 2014

Suzaku observed the Galactic center region near the Radio Arc at $\sim$20$^\prime$; southeast of Sagittarius A*. In an 18$^\prime$ × 18$^\prime$ field of view, we found four distinct X-ray sources: a bright star and a diffuse source associated with star clusters in the soft band (0.5–2.0 keV), a small clump in a higher energy band (4–6 keV), and a peculiar clump in the 6.4 keV line band. The latter two clumps are located at the south end of the Radio Arc. This paper reports on the results, and discusses the origin of these X-ray sources, with a particular emphasis on small clumps.
Direct Observation of the Extended Molecular Atmosphere of $o$ Ceti by Differential Spectral Imaging with an Adaptive Optics System
Authors: Takami Hideki , Goto Miwa , Gaessler Wolfgang , Hayano Yutaka , Iye Masanori , Kamata Yukiko , Kanzawa Tomio , Kobayashi Naoto , Minowa Yosuke , Oya Shin , Pyo Tae-Soo , Saint-Jacques David , Takato Naruhisa , Terada Hiroshi , Tokunaga Alan T. , Tsuji Takashi
Published: March 2014

We present new measurements of the diameter of $o$ Ceti (Mira) as a function of wavelength in the 2.2$\mu$m atmospheric window using the adaptive optics system and the infrared camera and spectrograph mounted on the Subaru Telescope. We found that the angular size of the star at the wavelengths of CO and H$_2$O absorption lines were up to twice as large as the continuum photosphere. This size difference is attributable to optically thick CO and H$_2$O molecular layers surrounding the photosphere. This measurement is the first direct differential spectroscopic imaging of stellar extension that resolves individual molecular lines with high spectral-resolution observations. This observation technique is extremely sensitive to differences in spatial profiles at different wavelengths; we show that a difference in diameter much smaller than the point spread function can be measured.
Super-Hard X-Ray Emission from η Carinae Observed with Suzaku
Authors: Sekiguchi Akiko , Tsujimoto Masahiro , Kitamoto Shunji , Ishida Manabu , Hamaguchi Kenji , Mori Hideyuki , Tsuboi Yohko
Published: March 2014

We present the Suzaku results of $\eta$ Carinae in the 5–50 keV range conducted twice around the apastron in 2005 August for 50 ks and in 2006 February for 20 ks. The X-ray Imaging Spectrometer (XIS) produced hard (5–12 keV) band spectra, resolving K shell lines from highly ionized Fe and Ni. The Hard X-ray Detector yielded a significant detection in the super-hard (15–50 keV) band, which was uncontaminated by near-by sources. We constrained the temperature of the optically thin thermal plasma emission dominant in the hard band to be 3–4 keV using the K-shell line features with the XIS. We found significant excess emission above the thermal emission in the super-hard band with the PIN, confirming the previous INTEGRAL ISGRI report. The entire 5–50 keV spectra were fitted by a combination of a thermal plasma model plus a flat power-law, or a very hot thermal bremsstrahlung model for the excess emission. No significant change of the excess emission was found at different epochs within the systematic and statistical uncertainties, and no flare-like flux amplification was seen in the hard band, indicating that the excess emission is a steady phenomenon. We argue that the super-hard emission is attributable to the inverse Compton of stellar UV photons by non-thermal electrons or to the thermal bremsstrahlung of very hot plasma, and not to the bremsstrahlung by non-thermal electrons colliding with cold ambient matter.
Radio Variability and Relativistic Beaming Effect for Blazars
Authors: Fan Jun-Hui , Huang Yong , He Tang-Mei , Yang Jiang He , Hua Tong Xu , Liu Yi , Wang Yong Xiang
Published: March 2014

In this paper, using a database of the University of Michigan Radio Astronomy Observatory at the radio frequencies (8 GHz and 14.5 GHz), we determined the variability time scales, and calculated the brightness temperature for 86 radio sources (29 BL Lacertae objects—BLs and 57 flat spectrum radio quasars—FSRQs). The time scales were found in the range of from 3 months to 16.27 years with an averaged value scale of 2.34 years. We obtained the following results: (1) The brightness temperature is in the range of log $T_{\rm b,var}$$=$ 10.98 to $T_{\rm b,var}$$=$ 15.35, which suggests that the Doppler factors are in the range of $\delta$$=$ 0.73 to $\delta$$=$ 20.74. The averaged values are $\langle\delta\rangle$$=$ 5.95$\pm$2.93 for 57 FSRQs and $\langle\delta\rangle$$=$ 5.08$\pm$2.63 for 29 BLs. (2) The radio luminosity, $L_{\rm ob}$, is found to be correlated with the radio Doppler factor, $\delta$, log$L_{\rm ob}$$=$ (0.58$\pm$0.10) log$\delta^{3}$$+$ 43.49$\pm$0.21. (3) The viewing angles and the Lorentz factors were determined for 53 sources (15 BLs and 38 FSRQS) with available superluminal velocity (Zhang & Fan 2008, Chin. J. Astron. Astrophys, 8, 385). The averaged values are $\Gamma$$=$ 24.1$\pm$17.35 and $\theta$$=$ 8$.^\circ$7$\pm$3$.^{\circ}$5 for the FSRQs, and $\Gamma$$=$ 13.5$\pm$11.16 and $\theta$$=$ 12$^{\circ}\pm$7$^{\circ}$ for the BLs.
Spectroscopic Observations of the WZ Sge-Type Dwarf Nova GW Librae during its 2007 Superoutburst
Authors: Hiroi Kazuo , Nogami Daisaku , Ueda Yoshihiro , Moritani Yuuki , Soejima Yuichi , Imada Akira , Hashimoto Osamu , Kinugasa Kenzo , Honda Satoshi , Narusawa Shin-ya , Sakamoto Makoto , Iizuka Ryo , Matsuda Kentaro , Naito Hiroyuki , Iijima Takashi , Fujii Mitsugu
Published: March 2014

We carried out an international spectroscopic observation campaign of the dwarf nova GW Librae (GW Lib) during its 2007 superoutburst. Our observation period covered the rising phase of the superoutburst, maximum, slowly decaying phase (plateau), and long fading tail phase after the rapid decline from the plateau. The spectral features dramatically changed during the observations. In the rising phase, only absorption lines of H$\alpha$, H$\beta$, and H$\gamma$ were present. Around the maximum, the spectrum showed singly peaked emission lines of H$\alpha$, He i 5876, He i 6678, He ii 4686, and C iii/N iii as well as absorption lines of the Balmer components and HeI. These emission lines significantly weakened during the latter part of the plateau phase. In the fading tail phase, all of the Balmer lines and He i 6678 were in emission, as observed in quiescence. We find that the center of the H$\alpha$ emission component was mostly stable over the whole orbital phase, being consistent with the low inclination of the system. Compared with the observational results of WZ Sagittae during its 2001 superoutburst, the same type of stars as GW Lib seen with a high inclination angle, we interpret that the change of the H$\alpha$ profile before the fading tail phase can be attributed to a photoionized region formed at the outer edge of the accretion disk, irradiated from the white dwarf and inner disk.
Light-Time Effect in the Early-Type Close Binary ZZ Cassiopeiae
Authors: Wen-Ping Liao , Sheng-Bang Qian
Published: March 2014

CCD observations of the eclipsing binary ZZ Cas were carried out during three nights from 2007 to 2008. Based on our new CCD times of light minimum and all available photoelectric and CCD data compiled from the literature, orbital period changes of ZZ Cas were analyzed. It was discovered that there may exist two cyclic variations (i.e., $P_3$$=$ 13.63 yr and $A_3$$=$ 0.02406 d, $P_4$$=$ 3.89 yr and $A_4$$=$ 0.00295 d). ZZ Cas is composed of early type component stars; the two cyclic variations can be explained by the light-time effect via the presence of the third and fourth bodies in the system. Minimal masses of $M_{3}$$=$ 5.00 $M_{\odot}$ and $M_{4}$$=$ 1.21$M_{\odot}$ were also calculated, respectively. These conclusions are in agreement with the result of previous investigations, that the additional bodies should contribute 23.6% to the total light of the system (Zasche 2009, New Astron., 14, 129), when the inclinations of the third and the fourth bodies are $i_3$$=$$i_4$$=$ 58$.\circ$9. The third and fourth bodies orbit the eclipsing binary at orbital distances of $a_3$$=$ 11.74AU and $a_4$$=$ 6.14AU, respectively.
Suzaku Observations of SN 1987A
Authors: Sturm Richard , Haberl Frank , Hasinger Günther , Kenzaki Kyoko , Itoh Masayuki
Published: March 2014

We report on Suzaku observations of SN1987A in the Large Magellanic Cloud, performed in 2005 November and 2006 June. The observations provide medium resolution X-ray spectra during the phase of the interaction between the supernova blast wave and the inner circumstellar ring. The Suzaku observations complement XMM-Newton and Chandra observations and were used to investigate the spectral evolution of SN1987A. The spectra were analyzed with two-temperature emission model from shocked gas. For the flux in the soft band (0.5−2.0 keV) we obtained 25.7$_{-1.9}^{+1.4}$$\times$ 10$^{-13}$ergcm$^{-2}$ (2005) and 30.8$_{-1.7}^{+1.4}$$\times$ 10$^{-13}$ergcm$^{-2}$ (2006). The exponential rise seen in the soft X-ray light curve of SN1987A till $\sim$6500 d after the explosion slowed down significantly between the Suzaku observations. Recent Chandra and XMM-Newton observations confirm this evolution. SN1987A continues to brighten exponentially, but with longer characteristic timescale. This must be caused by a less rapidly increasing emission measure.
NH3 in the Galactic Center is Formed under Cool Conditions
Authors: Nagayama Takumi , Omodaka Toshihiro , Handa Toshihiro , Toujima Hideyuki , Sofue Yoshiaki , Sawada Tsuyoshi , Kobayashi Hideyuki , Koyama Yasuhiro
Published: March 2014

It is an open question as to why the temperature of molecular gas in the Galactic center region is higher than that of dust. To address this problem, we made simultaneous observations in the NH$_3$ ($J,K$) $=$ (1, 1), (2, 2), and (3, 3) lines of the central molecular zone (CMZ) using the Kagoshima 6-m telescope. The ortho-to-para ratio of NH$_3$ molecules in the CMZ is 1.5–3.5 at most in the observed area. This ratio is higher than the statistical equilibrium value, and suggests that the formation temperature of NH$_3$ is 11–20 K. This temperature is similar to the dust temperature estimated from the submillimeter and infrared continuum. This result suggests that the NH$_3$ molecules in the CMZ were produced on dust grains with the currently observed temperature (11–20 K), and they were released into the gas phase by supernova shocks or collisions of dust particles. The discrepancy between warm molecular gas and cold dust can be explained by transient heating of the interstellar media in the CMZ approximately $10^5$ yr ago when NH$_3$ molecules were released from the dust.
Particle Propagation in the Galactic Center and Spatial Distribution of Non-Thermal X-Rays
Authors: Dogiel Vladimir A. , Chernyshov Dmitrii , Yuasa Takayuki , Cheng Kwong-Sang , Bamba Aya , Inoue Hajime , Ko Chung-Ming , Kokubun Motohide , Maeda Yoshitomo , Mitsuda Kazuhisa , Nakazawa Kazuhiro , Yamasaki Noriko Y.
Published: March 2014

We showed that if the non-thermal emission from the galactic center in the range 14–40 keV is due to inverse bremsstrahlung emission of subrelativistic protons, their interactions with hot and cold fractions of the interstellar medium are equally important. Our estimation shows that about 30% of the total non-thermal flux from the GC in the range 14–40 keV is generated in regions of cold gas while the rest is produced by proton interaction with hot plasma. From the spatial distribution of 6.7 keV iron line we concluded the spatial distribution of hot plasma is strongly non-uniform that should be taken into account in analysis of proton propagation in the GC. From the Suzaku data we got independent estimates for the diffusion coefficient of subrelativistic protons in the GC, which was in the range 10$^{26}$–10$^{27} $cm$^{2} $s$^{-1}$.
Metallicity Measurements of Pleiades Young Dwarfs
Authors: Funayama Hitoshi , Itoh Yoichi , Oasa Yumiko , Toyota Eri , Hashimoto Osamu , Mukai Tadashi
Published: March 2014

We present metallicity analyses of A, F, and G stars in the Pleiades cluster. High-resolution spectroscopic observations of 25 stars were made with the HIDES spectrograph on the Okayama 1.88-m telescope and the GAOES spectrograph on the Gunma 1.5-m telescope. The resultant optical spectra had an S$/$N of 70–220. We measured the equivalent widths of $\sim $60 neutral iron and $\sim $15 single-ionized iron absorption lines to determine stellar parameters and metallicities. We derived the metallicities of 22 stars by adapting the method of equivalent-width measurements. The average metallicity was $+$0.03$ \pm $0.05 dex. The dispersion was comparable to the statistical uncertainties of the metallicity measurements; in addition, the metallicities of all 22 stars fell within the dispersion range, indicating their uniform metallicities. A comparison of our results with previous studies confirmed a high probability of metallicity homogeneity in Pleiades.
WD+MS Systems as Progenitors of Type Ia Supernovae with Different Metallicities
Authors: Meng Xiangcun , Yang Wuming , Geng Xuemin
Published: March 2014

The single-degenerate model for the progenitors of type Ia supernovae (SNe Ia) is one of the two most popular models, in which a carbon–oxygen white dwarf accretes hydrogen-rich material from its companion, increases its mass to the Chandrasekhar mass limit, and then explodes as a SN Ia. Incorporating the prescription of Hachisu et al. (1999a, ApJ, 519, 314) for the accretion efficiency into Eggleton’s stellar evolution code and assuming that the prescription is valid for all metallicities, we carried out a detailed binary evolution study with different metallicities. We showed the initial and final parameter space for SNe Ia in a (log$ P$–$M_{\rm 2}$) plane. The positions of some famous recurrent novae in the (log$ P$–$M_{2}$) plane, as well as a supersoft X-ray source (SSS), RX J0513.9$-$6951 are well explained by our model, and our model can also explain the space velocity and mass of Tycho G, which is now suggested to be a companion star of Tycho’s supernova. Our study indicates that a SSS, V Sge, is a potential progenitor of supernovae, like SN 2002ic, if the delayed dynamical-instability model in Han and Podsiadlowski (2006, MNRAS, 368, 1095) is appropriate.
Viscous Accreting Magnetofluids around a Static Compact Object in Final Stages of Accretion Flow
Authors: Ghanbari Jamshid , Shaghaghian Mahboobeh
Published: March 2014

The dynamics of the stationary axisymmetric configuration of accreting magnetofluids surrounding a non-rotating compact object in the final stages of accretion flow is presented here. We discuss two classes of solutions for the angular momentum: a Keplerian solution, which demands no accretion flow for the fluids, and a non-Keplerian solution, which requires a radial inflow velocity for the matter. For the special case of no presence of electromagnetic fields, two sets of self-consistent analytical solutions of fully relativistic fluid equations are obtained separately for two different equations of state. The effect of the bulk viscosity coefficient on the physical functions was investigated for each state, as well as the bounds that exert on the free parameters due to last stages of the accretion-flow condition. To resolve the magnetohydrodynamical equations, we were inspired by previous sets of solutions, since the magnetofluid equations are just the same as the fluid ones in the case of vanishing electromagnetic fields. The azimuthal current in magnetofluids doesn’t modify the dipolar configuration of the central object magnetic field, owing to the lack of a finite resistivity. The presence of this magnetic field doesn’t affect the azimuthal velocity of the plasma, but does slow down its radial inflow, and decrease the density and pressure of the plasma. Despite the role importance of the bulk viscosity on the fluids’ dynamics in the absence of electromagnetic fields, exerting the magnetic field decreases this role.
Observational Appearance and Spectrum of Black-Hole Winds with Supercritical Accretion Disks
Authors: Fukue Jun
Published: March 2014

We examine the observational appearance and expected spectra of an optically thick, spherically symmetric, relativistic wind (a black-hole wind), blowing off from the central region of a geometrically thick supercritical accretion disk. Due to the relativistic limb-darkening (center-brightening) effect as well as the usual Doppler boost, the black-hole wind becomes luminous as the wind speed increases. We found that the spectra of the black-hole wind is somewhat similar to a blackbody one, while the spectra of a naked supercritical accretion disk is known to have a flat spectral energy distribution (SED) when viewing from the pole-on direction. In the case of a black-hole wind with a supercritical accretion disk, the spectra generally becomes a hybrid type, but we found that in almost all cases the characteristic flat SED of a supercritical disk disappears. That is, when the speed of the wind gas is low, the apparent photosphere of the black-hole wind becomes larger than the supercritical region. In this case the spectra of a black-hole wind dominates. As the wind speed increases, the apparent photosphere shrinks and the spectra of the disk emergent. However, when the wind speed becomes sufficiently high, the inner part of the naked supercritical disk is not seen, even if the inclination angle is small.