bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Structure of Umbral Dots Observed with the Hinode Solar Optical Telescope
Authors: Watanabe Hiroko , Kitai Reizaburo , Ichimoto Kiyoshi , Katsukawa Yukio
Published: March 2014

A high-resolution, seeing-free spectroscopic observation of a decaying sunspot was made with the Solar Optical Telescope aboard the Hinode satellite. The target was NOAA 10944, located in the west side of the solar surface from 2007 March 2 to March 4. The umbra included many umbral dots (UDs) with a size of $\sim$300 km in continuum light. We report on the magnetic structures and Doppler velocity fields around UDs, based on the Milne–Eddington inversions of the two iron absorption lines at 6302 Å. Histograms of the magnetic field strength (B), inclination angle (i), and Doppler velocity (v) of UDs showed a center-to-limb variation; observed at the disk center, the UDs had (i) slightly smaller field strength ($\Delta B$$=$$-$17 Gauss) and (ii) relative blue shifts ($\Delta v$$=$ 28 ms$^{-1}$) compared to their surroundings. When the sunspot got close to the limb, UDs and their surroundings showed almost no difference in the magnetic and Doppler values. This center-to-limb variation can be understood by the formation height difference in a cusp-shaped magnetized atmosphere around UDs, due to the weakly magnetized hot gas intrusion. In addition, some UDs showed the oscillatory light curves with multiple peaks separated around 10 min, which may indicate the presence of the oscillatory convection. We discuss our results within the frameworks of two theoretical models: the monolithic model (Schüssler & Vögler 2006, ApJ, 641, L73) and the field-free intrusion model (Spruit & Scharmer 2006, A&A, 447, 343).
Optically Thick Outflows of Supercritical Accretion Discs: Radiative Diffusion Approach
Authors: Abolmasov Pavel , Karpov Sergey , Kotani Taro
Published: March 2014

Highly supercritical accretion discs are probable sources of dense optically thick axisymmetric winds. We introduce a new approach based on diffusion approximation radiative transfer in a funnel geometry, and obtain an analytical solution for the energy density distribution inside the wind, assuming that all of the mass, momentum and energy are injected well inside the spherization radius. This allows us to derive the spectrum of the emergent emission for various inclination angles. We show that self-irradiation effects play an important role in altering the temperature of the outcoming radiation by about 20%, and the apparent X-ray luminosity by a factor of 2–3. The model has been successfully applied to two ULXs. The basic properties of the high ionization He ii-regions found around some ULXs are also easily reproduced in our models.
Molecular Superbubbles and Outflows from the Starburst Galaxy NGC 2146
Authors: Tsai An-Li , Matsushita Satoki , Nakanishi Kouichiro , Kohno Kotaro , Kawabe Ryohei , Inui Tatsuya , Matsumoto Hironori , Tsuru Takeshi G. , Peck Alison B. , Tarchi Andrea
Published: March 2014

We present results from a deep (1$\sigma$$=$ 5.7 mJy beam$^{-1}$ per 20.8 kms$^{-1}$ velocity channel) $^{12}$CO(1–0) interferometric observation of the central 60$^{\prime\prime}$ region of the nearby edge-on starburst galaxy NGC 2146, observed with the Nobeyama Millimeter Array. Two diffuse expanding molecular superbubbles and one molecular outflow were successfully detected. One molecular superbubble, with a size of $\sim$1 kpc and an expansion velocity of $\sim$50 kms$^{-1}$, is located below the galactic disk; a second molecular superbubble, with a size of $\sim$700 pc and an expansion velocity of $\sim$35 kms$^{-1}$, is also seen in the position-velocity diagram; the molecular outflow is located above the galactic disk with an extent of $\sim$2 kpc, expanding with a velocity of up to $\sim$200 kms$^{-1}$. The molecular outflow has an arc-like structure, and is located at the front edge of the soft X-ray outflow. In addition, the kinetic energy ($\sim$3 $\times$ 10$^{55}$erg) and the pressure ($\sim$1 $\times$ 10$^{-12\pm1}$dyncm$^{-2}$) of the molecular outflow are comparable to, or smaller than, that of the hot thermal plasma, suggesting that the hot plasma pushes the molecular gas out from the galactic disk. Inside the $\sim$1 kpc size molecular superbubble, diffuse soft X-ray emission seems to exist. However, since the superbubble lies behind the inclined galactic disk, it is largely absorbed by the molecular gas.
Search for Sc-K Line Emission from RX J0852.0$-$4622 Supernova Remnant with Suzaku
Authors: Hiraga Junko S. , Kobayashi Yusuke , Tamagawa Toru , Hayato Asami , Bamba Aya , Terada Yukikatsu , Petre Robert , Katagiri Hideaki , Tsunemi Hiroshi
Published: March 2014

We searched for evidence of line emission around 4 keV from the northwestern rim of the supernova remnant RX J0852.0$-$4622 using Suzaku XIS data. Several papers have reported on the detection of an emission line around 4.1 keV from this region of the sky. This line would arise from $K$-band fluorescence by $^{44}$Sc, the immediate decay product of $^{44}$Ti. We performed spectral analysis for the entire portion of the NW rim of the remnant within the XIS field of view, as well as various regions corresponding to regions of published claims of line emission. We found no line emission around 4.1 keV anywhere, and are able to set a restrictive upper limit to the X-ray flux: 1.1 $\times$ 10$^{-6}$s$^{-1}$cm$^{-2}$ for the entire field. For every region, our flux upper limit falls below that of the previously claimed detection. Therefore, we conclude that, to date, no definite X-ray line feature from Sc-K emission has been detected in the NW rim of RX J0852.0$-$4622. Our negative-detection supports the recent claim that RX J0852$-$4622 is neither young (1700–4000 yr) nor nearby ($\sim$750 pc).
Ejecta Distributions of Heavy Elements in the Cygnus Loop
Authors: Uchida Hiroyuki , Tsunemi Hiroshi , Katsuda Satoru , Kimura Masashi , Kosugi Hiroko
Published: March 2014

We analyzed the metal distribution of the Cygnus Loop using 14 and 7 pointing observation data obtained by the Suzaku and XMM-Newton observatories, respectively. The spectral analysis shows that all of the spectra are well fitted by a two-$kT_{\rm e}$ nonequilibrium ionization plasma model, as shown by earlier observations. From the best-fit parameters of the high-$kT_{\rm e}$ component, we calculated the emission measures about various elements, and showed the metal distribution of the ejecta component. We found that the distributions of Si and Fe are centered south of the geometric center toward the blow-out region. From the best-fit parameters, we also estimated the progenitor mass of the Cygnus Loop from our field of view (FOV) and the metal-rich region with a radius of 25$^\prime$ from the metal center. The result obtained from the metal circle is similar to that obtained from our entire FOV, which suggests a mixing of the metal. From the results, the mass of the progenitor star was estimated at 12-15$M_{\odot}$.
Photometric Studies of a WZ Sge-Type Dwarf Nova Candidate, ASAS 160048$-$4846.2
Authors: Soejima Yuichi , Imada Akira , Nogami Daisaku , Kato Taichi , Monard Berto
Published: March 2014

We report on our time-resolved CCD photometry during the 2005 June superoutburst of a WZ Sge-type dwarf nova candidate, ASAS 160048$-$4846.2. The ordinary superhumps of the object underwent a complex evolution during the superoutburst. The superhump amplitude experienced a regrowth and had two peaks. The superhump period decreased when the superhump amplitude reached the first maximum, subsequently increased gradually until the second maximum of the amplitude, and finally decreased again. Investigating other SU UMa-type dwarf novae, which show an increase in superhump period, we found the same trend of the superhump evolution in superoutbursts of them. We speculate that the superhump regrowth in the amplitude has a direct relation to the increase in superhump period, and all SU UMa-type dwarf novae with a superhump regrowth follow the same evolution of the ordinary superhumps as that of ASAS 160048$-$4846.2.
Formation of Galactic Center Magnetic Loops
Authors: Machida Mami , Matsumoto Ryoji , Nozawa Satoshi , Takahashi Kunio , Fukui Yasuo , Kudo Natsuko , Torii Kazufumi , Yamamoto Hiroaki , Fujishita Motosuji , Tomisaka Kohji
Published: March 2014

A survey of the molecular clouds in the Galaxy with the NANTEN mm telescope has discovered molecular loops in the galactic center region. They show monotonic gradients of the line-of-sight velocity along the loops and large velocity dispersions towards their foot-points. It is suggested that these loops can be explained in terms of a buoyant rise of magnetic loops due to a Parker instability. We carried out global three-dimensional magneto-hydrodynamic simulations of the gas disk in the galactic center. The gravitational potential was approximated by an axisymmetric potential proposed by Miyamoto and Nagai (1975, PASJ, 27, 533). At the initial state, we assumed a warm ($\sim$ 10$^4$K) gas torus threaded by azimuthal magnetic fields. Self-gravity and radiative cooling of the gas were ignored. We found that buoyantly rising magnetic loops are formed above the differentially rotating, magnetically turbulent disk. By analyzing the results of global MHD simulations, we identified individual loops, about 180 in the upper half of the disk, and studied their statistical properties, such as their length, width, height, and velocity distributions along the loops. The typical length and height of a loop are 1 kpc and 200 pc, respectively. The line-of-sight velocity changes linearly along a loop, and shows large dispersions around the foot-points. Numerical results indicate that loops emerge preferentially from the region where the magnetic pressure is large. We argue that these properties are consistent with those of molecular loops discovered by NANTEN.
Suzaku-WAM, Konus-Wind, and Swift-BAT Observations of Prompt Emission of the High-Redshift GRB 050904
Authors: Sugita Satoshi , Yamaoka Kazutaka , Ohno Masanori , Tashiro Makoto S. , Nakagawa Yujin E. , Urata Yuji , Pal’shin Valentin , Golenetskii Sergei , Sakamoto Takanori , Cummings Jay , Krimm Hans , Stamatikos Michael , Parsons Ann , Barthelmy Scott , Gehrels Neil
Published: March 2014

We present the results of the high-redshift GRB 050904 at z$=$ 6.295 from joint spectral analysis among Swift-BAT, Konus-Wind, and Suzaku-WAM, covering a wide energy range of 15–5000 keV. The $\nu F_{\nu}$ spectrum peak energy, $E_{\rm peak}$, was measured at 314$^{+173}_{-89}$keV, corresponding to 2291$^{+1263}_{-634}$keV in the source frame, and the isotropic equivalent radiated energy, $E_{\rm iso}$, was estimated to be 1.04$^{+0.25}_{-0.17}$$\times$ 10$^{54}$erg. Both are among the highest values that have ever been measured. GRBs with such a high $E_{\rm iso}$ ($\sim$10$^{54}$erg) might be associated with prompt optical emission. The derived spectral and energetic parameters are consistent with the correlation between the rest-frame $E_{\rm p,i}$ and the $E_{\rm iso}$ (Amati relation), but not with the correlation between the intrinsic peak energy $E_{\rm p,i}$ and the collimation-corrected energy $E_{\gamma}$ (Ghirlanda relation), unless the density of the circumburst environment of this burst is much larger than the nominal value, as suggested by other wavelength observations. We also discuss the possibility that this burst is an outlier in the correlation between $E_{\rm p,i}$ and the peak luminosity $L_{\rm p}$ (Yonetoku relation).
Chemical Evolution of Zinc in the Galaxy
Authors: Saito Yu-ji , Takada-Hidai Masahide , Honda Satoshi , Takeda Yoichi
Published: March 2014

The local thermodynamic equilibrium (LTE) abundances of zinc (Zn) of our sample of 35 metal-poor stars were explored in the range of $-$3.0 $<$ [Fe$/$H] $<$ 0.0. Based on a combination of our Zn abundances and those obtained in the literature, the behavior of Zn was investigated in the range of $-$4.2 $<$ [Fe$/$H] $<$  $+$0.5. The main results are as follows: (1) No clear separation in [Zn$/$Fe] behavior was found between halo, thick disk, and thin disk stars in our sample. (2) The decreasing trend of [Zn$/$Fe] with the increase of [Fe$/$H] was found to be confirmed to $-$4.2 $<$ [Fe$/$H] $\le$  $-$2.0, and to be explained by a chemical evolution model constructed with models of core-collapse supernovae (SNe) II or hypernovae (HNe) of Population III stars. (3) In $-$2.0 $<$ [Fe$/$H] $<$  $+$0.5, [Zn$/$Fe] follows a nearly flat trend with a slight enhancement of $\sim+$0.07 dex up to [Fe$/$H] $=$  $-$1.0, and shows the more enhanced trend in $-$1.0 $<$ [Fe$/$H] $\le$  $-$0.5, and then gradually decreases to an almost solar value in [Fe$/$H] $>$  $-$0.5. This trend is better explained by a chemical evolution model constructed with models of normal SNe II, HNe, and SNe Ia, in which the metallicity effect and the single-degenerate scenario of the SNe Ia model are incorporated.
A New Photometric Study for the Weak-Contact Binary V700 Cygni
Authors: Yang Yuan-Gui , Dai Hai-Feng
Published: March 2014

We present a new charge-coupled device (CCD) photometry for the weak-contact binary V700 Cygni. From our light curves in the VR bands, a photometric solution was deduced by the 2003 version of the W – D program. The results show that V700 Cyg is a W-subtype binary with $q$$=$ 0.5437($\pm$0.0018) and $f$$=$ 15.1%($\pm$0.3%). The contributions of the third light to the total light are $l_{3V}$$=$ 2.59%($\pm$0.10%) and $l_{3R}$$=$ 2.64%($\pm$0.10%) for the VR bands, respectively. Based on all available light-minimum times from 1946 to 2008, a detailed period analysis reveals that there exists a long-term period increase with a periodic oscillation. This cyclic variation, with $P_3$$=$ 54.0($\pm$2.0)yr, $A$$=$ 0.$^{\rm d}$0185 ($\pm$0.$^{\rm d}$0012 d), and $e{}^\prime$$=$ 0.2117($\pm$0.0059) from equation (3), may result from a light-time effect via the third body, identified by the third light in the photometric solution. If an additional body exists, V700 Cyg may be a triple star system. This kind of tertiary component may remove angular momentum from the central system, which may play an important role in the formation and evolution of the binary. A continuous period increase at a rate of $dP/dt$$=$$+$0.33($\pm$0.08) $\times$ 10$^{-7}$dyr$^{-1}$ can be interpreted as being mass transfer from the less-massive component to the more-massive one. With mass transferring, the orbital period increases and the separation between both components becomes wider. Finally, the contact configuration will break, as predicted by TRO theory. Therefore, this kind of weak-contact binary with a secular period increase will evolve into a broken-contact configuration.
Anti-Correlation of Near-Infrared and X-Ray Variations of the Microquasar GRS 1915+105 in the Soft State
Authors: Arai Akira , Uemura Makoto , Sasada Mahito , Trushkin Sergei A. , Ueda Yoshihiro , Takahashi Hiromitsu , Kawabata Koji S. , Yamanaka Masayuki , Nagae Osamu , Ikejiri Yuki , Sakimoto Kiyoshi , Matsui Risako , Ohsugi Takashi , Yamashita Takuya , Isogai Mizuki , Fukazawa Yasushi , Mizuno Tsunefumi , Katagiri Hideaki , Okita Kiichi , Yoshida Michitoshi , Yanagisawa Kenshi , Sato Shuji , Kino Masaru , Sadakane Kozo
Published: March 2014

We present detailed, long term near-infrared (NIR) light curves of GRS 1915$+$105 obtained in 2007–2008, covering its long “soft state” for the first time. From our NIR monitoring and X-ray data of the All Sky Monitor onboard Rossi X-ray Timing Explorer, we discovered that the NIR flux dropped by $\gt$ 1 mag during short X-ray flares with a time-scale of days. Upon termination of the soft state, the $H-K_{\rm s}$ color reddened and the anti-correlation pattern was broken. The observed $H-K_{\rm s}$ color variation suggests that the dominant NIR source was an accretion disk during the soft state. The short X-ray flares during the soft state were associated with spectral hardening in X-rays and increasing radio emission, indicating jet ejection. The temporal NIR fading during the X-ray flares thus implies a sudden decrease in the contribution of the accretion disk when a jet is ejected.
Photometry of Three Superoutbursts of the SU UMa-Type Dwarf Nova, SW Ursae Majoris
Authors: Soejima Yuichi , Nogami Daisaku , Kato Taichi , Uemura Makoto , Imada Akira , Sugiyasu Kei , Maehara Hiroyuki , Torii Ken’ichi , Tanabe Kenji , Oksanen Arto , Nakajima Kazuhiro , Novák Rudolf , Masi Gianluca , Hynek Tomáš , Martin Brian , Buczynski Denis , Pavlenko Elena P. , Shugarov Sergei Yu. , Cook Lewis M.
Published: March 2014

We investigated superhump evolution, analysing optical photometric observations of the 2000 February–March, the 2002 October–November, and the 2006 September superoutbursts of SW UMa. The superhumps evolved in the same way after their appearance during the 2000 and 2002 superoutbursts, and probably during the 2006 one. This indicates that superhump evolution may be governed by invariable binary parameters. We detected a periodicity in the light curve after the end of the 2000 superoutburst without any phase shift, which seems to be the remains of the superhumps. We found QPOs at the end stage of the 2000 and 2002 superoutbursts, but failed to find extraordinarily large-amplitude QPOs, called ‘super-QPOs’, which previously had been observed in SW UMa.
Effects of Hardness of Primordial Binaries on the Evolution of Star Clusters
Authors: Tanikawa Ataru , Fukushige Toshiyuki
Published: March 2014

We have investigated the effects of the hardness of primordial binaries on the whole evolution of star clusters by means of $N$-body simulations. Using a newly developed code, GORILLA, we simulated eleven $N$$=$ 16384 clusters with primordial binaries whose binding energies are equal in each cluster in the range of 1−300$kT_0$, where 1.5$kT_0$ is the average stellar kinetic energy at the initial time. We found that, in both the soft ($\le$3$kT_0$) and hard ($\ge$300$kT_0$) limits, clusters experience deep core collapse. For intermediate hardness (10−100$kT_0$), the core collapses halt halfway due to an energy releases of the primordial binaries. The core radii at the halt can be explained by their energy budget.
An X-Ray Face-On View of the Sagittarius B Molecular Clouds Observed with Suzaku
Authors: Ryu Syukyo G. , Koyama Katsuji , Nobukawa Masayoshi , Fukuoka Ryosuke , Tsuru Takeshi Go
Published: March 2014

We present a new methodology to derive the positions of the Sagittarius (Sgr) B molecular clouds (MCs) along the line of sight, as an application study of the Galactic center diffuse X-rays (GCDX). The GCDX are composed of hot plasma emission of about 7 keV and 1 keV temperatures, and non-thermal continuum emission including the 6.4 keV line from neutral irons. The former, the Galactic center plasma emission (GCPE), is uniformly distributed over 1$^\circ$ in longitude, while the latter is clumpy emission produced by Thomson scattering and fluorescence from MCs irradiated by external X-rays (the X-ray reflection nebula emission: XRNE). We examined the Suzaku X-ray spectra of the GCPE and XRNE near to the Sgr B MC complex, and found that the spectra suffer from two different absorptions of $N_{\rm H}$ (Abs1) $\geq$10$^{23}$H cm$^{-2}$ and $N_{\rm H}$ (Abs2) $\simeq$6 $\times$ 10$^{22}$H cm$^{-2}$. Abs1 is proportional to the 6.4 keV-line flux, and hence is due to the MCs, while Abs2 is typical of interstellar absorption toward the Galactic center. Assuming that the GCPE plasma is spherically-extended around Sgr A$^\ast$ with a uniform density and the same angular distribution of the two temperature components, we quantitatively estimated the line-of-sight positions of the MCs from the flux ratio the GCPE spectrum suffered by Abs1 and that with no Abs1. The results suggest that the Sgr B MCs are located at the near side of Sgr A$^\ast$ in the GCPE.
New Spectral State of Supercritical Accretion Flow with Comptonizing Outflow
Authors: Kawashima Tomohisa , Ohsuga Ken , Mineshige Shin , Heinzeller Dominikus , Takabe Hideaki , Matsumoto Ryoji
Published: March 2014

Supercritical accretion flows inevitably produce radiation-pressure driven outflows, which Compton up-scatter soft photons from the underlying accretion flow, thereby making hard emission. We performed two-dimensional radiation hydrodynamic simulations of supercritical accretion flows and outflows, while incorporating such Compton scattering effects, and demonstrated that there appears a new hard spectral state at higher photon luminosities than that of the slim-disk state. In this state, as the photon luminosity increases, the photon index decreases and the fraction of the hard emission increases. The Compton $y$-parameter is on the order of unity (and thus the photon index will be $\sim$2) when the apparent photon luminosity is ${\sim}$ 30$L_{\rm E}$ (with $L_{\rm E}$ being the Eddington luminosity) for nearly face-on sources. This explains the observed spectral hardening of the ULX NGC 1313 X-2 in its brightening phase, and thus supports the model of supercritical accretion onto stellar-mass black holes in this ULX.
Origin of 6.4 keV Line Emission from Molecular Clouds in the Galactic Center
Authors: Dogiel Vladimir , Cheng Kwong-Sang , Chernyshov Dmitrii , Bamba Aya , Ichimura Atsushi , Inoue Hajime , Ko Chung-Ming , Kokubun Motohide , Maeda Yoshitomo , Mitsuda Kazuhisa , Yamasaki Noriko Y.
Published: March 2014

We analyze the 6.4 keV line and continuum emission from the molecular cloud Sgr B2 and the source HESS J1745$-$303, which is supposed to be a complex of molecular gas. From the HESS results it follows that Sgr A$^\ast$ is a source of high energy protons, which penetrate into molecular clouds producing there a TeV gamma-ray flux. We present arguments that Sgr A$^\ast$ may also produce a flux of subrelativistic protons which generate the 6.4 keV line and bremsstrahlung continuum emission from the clouds.
Suzaku X-Ray Study of an Anomalous Source XSS J12270–4859
Authors: Saitou Kei , Tsujimoto Masahiro , Ebisawa Ken , Ishida Manabu
Published: March 2014

We report on the results of a Suzaku X-ray observation of XSS J12270$-$4859, one of the hard X-ray sources in the INTEGRAL catalogue. This object has been classified as an intermediate polar (IP) by its optical spectra, and a putative X-ray period of $\sim$860 s. With a 30 ks exposure by Suzaku, we obtained a well-exposed spectrum in the 0.2–70 keV band. We conclude against a previous IP classification based on a lack of Fe K$\alpha$ emission features in the spectrum and a failure to confirm the previously reported X-ray period. Instead, the X-ray light curve is filled with exotic phenomena, including repetitive flares lasting for $\sim$100 s, occasional dips with no apparent periodicities, spectral hardening after some flares, and bimodal changes pivoting between quiet and active phases. The rapid flux changes, the dips, and the power-law spectrum point toward an interpretation that this is a low-mass X-ray binary. Some temporal characteristics are similar to those in the Rapid Burster and GROJ1744$-$28, making XSS J12270$-$4859 a very rare object.
Similarity between the Molecular Loops in the Galactic Center and the Solar Chromospheric Arch Filaments
Authors: Takahashi Kunio , Nozawa Satoshi , Matsumoto Ryoji , Machida Mami , Fukui Yasuo , Kudo Natsuko , Torii Kazufumi , Yamamoto Hiroaki , Fujishita Motosuji
Published: March 2014

We carried out two-dimensional magnetohydrodynamic simulations of the Galactic gas disk to show that the dense loop-like structures discovered by the Galactic center molecular cloud survey using the NANTEN 4-m telescope can be formed by a buoyant rise of magnetic loops due to the Parker instability. At the initial state, we assumed a gravitationally stratified disk consisting of a cool layer ($T$$\sim$ 10$^{3} $K), a warm layer ($T$$\sim$ 10$^{4} $K), and a hot layer ($T$$\sim$ 10$^{5} $K). The simulation box was a local part of the disk containing the equatorial plane. The gravitational field was approximated by that of a point mass at the Galactic center. The self-gravity, and the effects of the Galactic rotation were ignored. Numerical results indicate that the length of the magnetic loops emerging from the disk is determined by the scale height of the hot layer ($\sim$ 100 pc at 1 kpc from the Galactic center). The loop length, velocity gradient along the loops, and large velocity dispersions at their foot points are consistent with the NANTEN observations. We also show that the loops become top-heavy when the curvature of the loop is sufficiently small, so that the rising loop accumulates the overlying gas faster than sliding it down along the loop. This mechanism is similar to that in the formation of solar chromospheric arch filaments. The molecular loops emerge from the low-temperature layer just like the dark filaments observed in the H$\alpha$ image of the emerging flux region of the Sun.
Improved Measurement of the Rossiter–McLaughlin Effect in the Exoplanetary System HD 17156
Authors: Narita Norio , Hirano Teruyuki , Sato Bun’ei , Winn Joshua N. , Suto Yasushi , Turner Edwin L. , Aoki Wako , Tamura Motohide , Yamada Toru
Published: March 2014

We present an improved measurement of the Rossiter–McLaughlin effect for the exoplanetary system HD 17156, based on radial-velocity data gathered with the Subaru 8.2-m telescope throughout the planetary transit of UT 2008 November 7. The data allow for a precise and independent determination of the projected spin-orbit angle of this system: $\lambda $$=$ 10${\rlap{^\circ}\hskip.5pt.\hskip1pt}$0 $ \pm $5${\rlap{^\circ}\hskip.5pt.\hskip1pt}$1. This result supersedes the previous claim of $\lambda $$=$ 62${}^\circ$$ \pm $25${}^\circ$ by Narita et al. (2008, PASJ, 60, L1), which was based on lower-precision data with poor statistics. Thus the stellar spin and planetary orbital axes of the HD 17156 system are likely to be well-aligned, despite the planet’s large orbital eccentricity suggesting a history of strong dynamical interactions.
The MAXI Mission on the ISS: Science and Instruments for Monitoring All-Sky X-Ray Images
Authors: Matsuoka Masaru , Kawasaki Kazuyoshi , Ueno Shiro , Tomida Hiroshi , Kohama Mitsuhiro , Suzuki Motoko , Adachi Yasuki , Ishikawa Masaki , Mihara Tatehiro , Sugizaki Mutsumi , Isobe Naoki , Nakagawa Yujin , Tsunemi Hiroshi , Miyata Emi , Kawai Nobuyuki , Kataoka Jun , Morii Mikio , Yoshida Atsumasa , Negoro Hitoshi , Nakajima Motoki , Ueda Yoshihiro , Chujo Hirotaka , Yamaoka Kazutaka , Yamazaki Osamu , Nakahira Satoshi , You Tetsuya , Ishiwata Ryoji , Miyoshi Sho , Eguchi Satoshi , Hiroi Kazuo , Katayama Haruyoshi , Ebisawa Ken
Published: March 2014

The Monitor of All-sky X-ray Image (MAXI) mission is the first astronomical payload to be installed on the Japanese Experiment Module — Exposed Facility (JEM-EF or Kibo-EF) on the International Space Station. It has two types of X-ray slit cameras with wide FOVs and two kinds of X-ray detectors consisting of gas proportional counters covering the energy range of 2 to 30 keV and X-ray CCDs covering the energy range of 0.5 to 12 keV. MAXI will be more powerful than any previous X-ray All Sky Monitor payloads, being able to monitor hundreds of Active Galactic Nuclei. A realistic simulation under optimal observation conditions suggests that MAXI will provide all-sky images of X-ray sources of $\sim $20 mCrab ($\sim $7 $\times$ 10$^{-10} $erg cm$^{-2} $s$^{-1}$ in the energy band of 2–30 keV) from observations during one ISS orbit (90 min), $\sim $4.5 mCrab for one day, and $\sim $2 mCrab for one week. The final detectability of MAXI could be $\sim $0.2 mCrab for two years, which is comparable to the source confusion limit of the MAXI field of view (FOV). The MAXI objectives are: (1) to alert the community to X-ray novae and transient X-ray sources, (2) to monitor long-term variabilities of X-ray sources, (3) to stimulate multi-wavelength observations of variable objects, (4) to create unbiased X-ray source cataloges, and (5) to observe diffuse cosmic X-ray emissions, especially with better energy resolution for soft X-rays down to 0.5 keV.
Multifrequency Study of Giant Radio Pulses from the Crab Pulsar with the K5 VLBI Recording Terminal
Authors: Popov Mikhail , Soglasnov Vladimir , Kondratiev Vladislav , Bilous Anna , Moshkina Olga , Oreshko Vasily , Ilyasov Yury , Sekido Mamoru , Kondo Tetsuro
Published: March 2014

Simultaneous multifrequency observations of Crab pulsar giant pulses (GPs) were performed with the 64-m Kalyazin radio telescope at four frequency ($\nu$$=$ 0.6, 1.4, 2.2, and 8.3 GHz) using the K5 VLBI recording terminal. The K5 terminal provided continuous recording in 16 $\times$ 4-MHz wide frequency channels distributed over 4 frequency bands. Several thousand GPs were detected during about 6 hours of observations on two successive days in 2005 July. The radio spectra of single GPs were analyzed at separate frequencies and over the whole frequency range. These spectra manifest notable modulation over the frequency ranges, $\Delta\nu$, both on large ($\Delta\nu/\nu$$\approx$ 0.5) and small ($\Delta\nu/$$\nu$$\approx$ 0.01) frequency scales. A cross-correlation analysis of GPs at 2.2 GHz showed that their pulse shapes can be interpreted as being an ensemble of unresolved bursts grouped together on time scales of $\approx$1$ \mu$s, being well-correlated over a 60-MHz band. The corresponding GP cross-correlation functions do not obey the predictions of the amplitude-modulated noise model of Rickett (1975), thus indicating that unresolved components represent a small number of elementary emitters.
Suzaku Observation of Diffuse X-Ray Emission from the Open Cluster Westerlund 2: a Hypernova Remnant?
Authors: Fujita Yutaka , Hayashida Kiyoshi , Takahashi Hiroaki , Takahara Fumio
Published: March 2014

We present an analysis of Suzaku observations of the young open cluster Westerlund 2, which is filled with diffuse X-ray emission. We found that the emission consists of three thermal components, or two thermal and one non-thermal components. The upper limit of the energy flux of the non-thermal component is smaller than that in the TeV band observed with H.E.S.S. This may indicate that active particle acceleration has stopped in this cluster, and that the accelerated electrons have already cooled. The gamma-ray emission observed with H.E.S.S. is likely to come from high-energy protons, which hardly cool, in contrast with electrons. The metal abundances of the diffuse X-ray gas may indicate the explosion of a massive star in the past.
Relativistic Spectra of Hot Black-Hole Winds
Authors: Sumitomo Naoko , Saito Hideki , Fukue Jun , Watarai Kenya
Published: March 2014

We examine hybrid thermal-nonthermal synchrotron spectra from a spherically symmetric, optically-thin wind, taking into account the relativistic effect. In relativistic flow from the central object, due to the relativistic beaming effect, the observed spectra often shift towards high frequency and high intensity directions. In optically thin outflows, however, we find that the intensity of the observed spectra decreases compared with that of the emitted ones, although the peak frequency shifts towards the high-frequency direction. This is because in the optically thin outflows we can see the far-side flows that go away from the observer. We thus carefully consider optically thin relativistic flows around a black hole, such as Sgr A$^\ast$.
Suzaku Observation of the Radio Halo Cluster Abell 2319: Gas Dynamics and Hard X-Ray Properties
Authors: Sugawara Chika , Takizawa Motokazu , Nakazawa Kazuhiro
Published: March 2014

We present the results of a Suzaku observation of the radio halo cluster Abell 2319 (A 2319). The metal abundance in the central cool region is found to be higher than the surrounding region, which was not resolved in former studies. We confirm that the line-of-sight velocities of the intracluster medium in the observed region are consistent with those of the member galaxies of the entire A 2319 and A 2319A subgroup for the first time, though no velocity difference within the region has been detected. On the other hand, we have not found any signs of gas motion relevant to the A 2319B subgroup. Hard X-ray emission from the cluster has clearly been detected, but its spectrum is likely to be thermal. Assuming a simple single-temperature model for the thermal component, we find that the upper limit of the non-thermal inverse Compton component becomes 2.6 $\times$ 10$^{-11} $erg s$^{-1} $cm$^{-2}$ in the 10–40 keV band, which means that the lower limit of the magnetic field is 0.19 $\mu$G with a radio spectral index of 0.92. Although the results slightly depend on the detailed spectral modeling, it is robust that the upper limit of the power-law component flux and lower limit of the magnetic field strength become $\sim $3 $\times$ 10$^{-11} $erg s$^{-1} $cm$^{-2}$ and $\sim $0.2$\mu$G, respectively. Considering the lack of a significant amount of very hot ($\sim $20 keV) gas and the strong bulk flow motion, it is more likely that the relativistic non-thermal electrons responsible for the radio halo are accelerated through intracluster turbulence rather than shocks.
VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars
Authors: Doi Akihiro , Kawaguchi Noriyuki , Kono Yusuke , Oyama Tomoaki , Fujisawa Kenta , Takaba Hiroshi , Sudou Hiroshi , Wakamatsu Ken-ichi , Yamauchi Aya , Murata Yasuhiro , Mochizuki Nanako , Wajima Kiyoaki , Omodaka Toshihiro , Nagayama Takumi , Nakai Naomasa , Sorai Kazuo , Kawai Eiji , Sekido Mamoru , Koyama Yasuhiro ,   the VLBI group at Geographical Survey Institute, Asano Shoichiro , Uose Hisao
Published: March 2014

We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey Third Data Release, by a very-long-baseline interferometry (VLBI) technique. The VLBI instrument we used was developed by the Optically ConnecTed Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of the Japanese VLBI Network. We aimed to select BAL quasars with nonthermal jets suitable for measuring their orientation angles and ages by subsequent detailed VLBI imaging studies to evaluate two controversial issues of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars are in a short-lived evolutionary phase of the quasar population. We detected 20 out of 22 sources using the OCTAVE baselines, implying brightness temperatures greater than 10$^{5}$ K, which presumably come from nonthermal jets. Hence, BAL outflows and nonthermal jets can be generated simultaneously in these central engines. We also found four inverted-spectrum sources, which are interpreted as Doppler-beamed, pole-on-viewed relativistic jet sources, or young radio sources: single edge-on geometry cannot describe all BAL quasars. We discuss the implications of the OCTAVE observations for investigations for the orientation and evolutionary stage of BAL quasars.
Frequency Separation Variations of the Solar Low-Degree p-Modes
Authors: Yang Wuming , Meng Xiangcun
Published: March 2014

Variations of frequency separations of low-degree p-modes have been studied over the solar-activity cycle. The studied separations were obtained from the frequencies of low-degree p-modes of the Global Oscillation Network Group (GONG). The 10.7 cm radio flux was used as an index of solar activity. Small separations of the p-mode frequencies are considered to be mainly dependent on the conditions in stellar interiors. Thus, they could be applied to a diagnosis of the changes in the stellar interior. Our calculation results show that the magnitudes of the variations of the mean large separations are less than 1$ \sigma$ over the solar-activity cycle. Small separations show different behaviors in the ascending and descending phases of activity. In the ascending phase, variations of the small separations are less than 1$ \sigma$. However, the small separations had systematic shifts during the period from 2004 to 2007. These shifts were roughly 1$ \sigma$ or more. The variations in the ratios of the small-to-large separations with time were similar to the changes of the small separations. The effects of the changes in the large separations on the ratios were negligible. The variations of the separations may be a consequence of influence from the surface activity, or systematic errors in measurements, or some processes taking place in the solar interior.
Suzaku Observations of Thermal and Non-Thermal X-Ray Emission from the Middle-Aged Supernova Remnant G156.2$+$5.7
Authors: Katsuda Satoru , Petre Robert , Hwang Una , Yamaguchi Hiroya , Mori Koji , Tsunemi Hiroshi
Published: March 2014

We present results from an X-ray analysis of a Galactic middle-aged supernova remnant (SNR), G156.2$+$5.7, which is bright and largely extended in X-ray wavelengths, showing a clear circular shape (radius $\sim$ 50$^\prime$). Using the Suzaku satellite, we observed this SNR in three pointings: partially covering the northwestern rim, the eastern rim, and the central portion of this SNR. In the northwestern rim and the central portion, we confirmed that the X-ray spectra consist of soft and hard-tail emissions, while in the eastern rim we found no significant hard-tail emission. The soft emission was well-fitted by a non-equilibrium ionization (NEI) model. In the central portion, a two-component (the interstellar medium and the metal-rich ejecta) NEI model was used to fit the soft emission better than a one-component NEI model from a statistical point of view. The relative abundances in the ejecta component suggest that G156.2$+$5.7 is a remnant from a core-collapse SN explosion whose progenitor mass is less than 15$M_\odot$. The origin of the hard-tail emission is highly likely to be non-thermal synchrotron emission from relativistic electrons. In the northwestern rim, the relativistic electrons seem to be accelerated by a forward shock with a slow velocity of $\sim$ 500 kms$^{-1}$.
Suzaku Observations of Tycho’s Supernova Remnant
Authors: Tamagawa Toru , Hayato Asami , Nakamura Satoshi , Terada Yukikatsu , Bamba Aya , Hiraga Junko S. , Hughes John P. , Hwang Una , Kataoka Jun , Kinugasa Kenzo , Kunieda Hideyo , Tanaka Takaaki , Tsunemi Hiroshi , Ueno Masaru , Holt Stephen S. , Kokubun Motohide , Miyata Emi , Szymkowiak Andrew , Takahashi Tadayuki , Tamura Keisuke , Ueno Daisuke , Makishima Kazuo
Published: March 2014

Tycho’s supernova remnant was observed by the XIS and HXD instruments onboard the Suzaku satellite on 2006 June 26–29 for 92 ks. The spectrum up to 30 keV was well fitted with a two-component model, consisting of a power-law with a photon index of 2.7 and a thermal bremsstrahlung model with a temperature of 4.7 keV. The former component can alternatively be modeled as synchrotron emission from a population of relativistic electrons with an estimated roll-off energy of around 1 keV. In the XIS spectra, in addition to the prominent Fe K$\alpha$ line (6.445 keV), we observed for the first time significant K$\alpha$ line emission from trace species Cr and Mn at energies of 5.48 keV and 5.95 keV, respectively. Faint K$\beta$ lines from Ca (4.56 keV) and Fe (7.11 keV) were also seen. The ionization states of Cr and Mn, based on their line centroids, are estimated to be similar to that of Fe K$\alpha$ (FeXV or XVI).
Suzaku Observation of 30 Dor C: A Supernova Remnant with the Largest Non-Thermal Shell
Authors: Yamaguchi Hiroya , Bamba Aya , Koyama Katsuji
Published: March 2014

This paper reports on the Suzaku results of thermal and non-thermal features of 30 Dor C, a supernova remnant (SNR) in a superbubble of the Large Magellanic Cloud (LMC). The west rim exhibits a non-thermal X-ray spectrum with no thermal component. A single power-law model is rejected, but a power-law model with spectral cutoff is accepted. The cutoff frequency of (3–7) $\times$ 10$^{17}$Hz is the highest among the shell-type SNRs, like SN 1006 ($\sim$6 $\times$ 10$^{16}$Hz), and hence 30 Dor C would be the site of the highest energy accelerator of the SNR shock. The southeast (SE) and northeast (NE) rims have both thermal and non-thermal components. The thin-thermal plasmas in both rims are in a collisional ionization equilibrium state. The electron temperature of the plasma in the SE rim ($kT_{\rm e}$$\sim$ 0.7 keV) is found to be higher than the previously reported value. The power-law index from SE is nearly the same, while that from the NE is larger than that of the West rim. The SNR age would be in the range of (4–20) $\times$ 10$^{3}$yr. Thus, 30 Dor C is likely to be the oldest shell-like SNR with non-thermal emission.
X-Ray Studies of HESS J1837$-$069 with Suzaku and ASCA: a VHE Gamma-Ray Source Originated from the Pulsar Wind Nebula
Authors: Anada Takayasu , Ebisawa Ken , Dotani Tadayasu , Bamba Aya
Published: March 2014

We present ASCA and Suzaku studies of the TeV source HESS J1837$-$069, which has not been identified in other wavelengths. We confirm the presence of two X-ray sources in the Suzaku XIS image, AX J1838.0$-$0655 and AX J1837.3$-$0652, near both ends of the elongated TeV emission region. The XIS spectra of the two sources were reproduced by an absorbed power-law model, whose parameters are all consistent with those determined by the ASCA data. Recently, 70.5 ms X-ray pulsation has been detected with RXTE in the sky region including HESS J1837$-$069 (Gotthelf & Halpern 2008, ApJ, 681, 515). Using the ASCA GIS data, which has both timing and imaging capabilities, we identified the pulsation source as AX J1838.0$-$0655. The pulse periods determined by ASCA and Suzaku, and that reported with RXTE indicate steady spin-down at $\dot{P}$$=$ 4.917(4)$\times$10$^{-14}$s s$^{-1}$. These results suggest that AX J1838.0$-$0655 is an intrinsically stable source, and presumably a pulsar wind nebula (PWN). We discuss the possibility that AX J1838.0$-$0655 is associated with HESS J1837$-$069 and the VHE $\gamma$-ray emission is originated from the PWN.
Suzaku Observation of HESS J1825$-$137: Discovery of Largely-Extended X-Rays from PSR J1826$-$1334
Authors: Uchiyama Hideki , Matsumoto Hironori , Tsuru Takeshi Go , Koyama Katsuji , Bamba Aya
Published: March 2014

We observed the brightest part of HESS J1825$-$137 with the Suzaku XIS, and found diffuse X-rays extending at least up to 15$^\prime$ ($\sim$17 pc) from the PSR J1826$-$1334. The spectra have no emission line, and were fitted with an absorbed power-law model. The X-rays, therefore, are likely to be due to synchrotron emission from a pulsar wind nebula. The photon index near the pulsar ($r$$\leq$ 1${\rlap{\hskip.75pt{^\prime}}\hskip.75pt.\hskip1pt}$5) is $\Gamma$$=$ 1.7, while those in $r$$=$ 1${\rlap{\hskip.75pt{^\prime}}\hskip.75pt.\hskip1pt}$5–16${}^\prime$ are nearly constant at $\Gamma$$=$ 2.0. The spectral energy distribution of the Suzaku and H.E.S.S. results are naturally explained by a combined process; synchrotron X-rays and $\gamma $-rays by the inverse Compton of the cosmic microwave photons by high-energy electrons in a magnetic field of $\sim$7$\mu$G. If the electrons are accelerated at the pulsar, the electrons must be transported over 17 pc in the synchrotron lifetime of 1900 yr, with a velocity of $\geq$8.8 $\times$ 10$^{3}$km s$^{-1}$.
X-Ray Observations of the Sagittarius D H ii Region toward the Galactic Center with Suzaku
Authors: Sawada Makoto , Tsujimoto Masahiro , Koyama Katsuji , Law Casey J. , Tsuru Takeshi Go , Hyodo Yoshiaki
Published: March 2014

We present a Suzaku X-ray study of the Sagittarius D (Sgr$\;$D) H ii region in the Galactic center region. Two 18$^{\prime}$$\times$ 18$^{\prime}$ images by the X-ray Imaging Spectrometer (XIS) encompass the entire Sgr$\;$D complex. Thanks to the low background, XIS discovered two diffuse sources with low surface brightness and obtained their high signal-to-noise ratio spectra. One is associated with the core of the Sgr$\;$D H ii region, arising from a young stellar cluster. The other object is new and reported here for the first time. We also present 3.5 cm and 6.0 cm radio continuum maps of the new source using the 100-m Green Bank Telescope. We conclude that the source is a new supernova remnant (SNR; G1.2$-$0.0) based on: (1) the 0.9$\pm$0.2 keV thermal X-ray spectrum with emission lines from highly ionized atoms; (2) the diffuse nature with an apparent extent of $\sim$10 pc at the Galactic center distance inferred from the X-ray absorption ($\sim$8.5 $\times$ 10$^{22}$cm$^{-2}$); and (3) the nonthermal radio continuum spectral index ($\sim-$0.5). Our discovery of an SNR in the Sgr$\;$D H ii region leads to a revision of the view of this system, which had been considered to be a thermal H ii region and its environment.
A New Supernova Remnant Candidate and an Associated Outflow in the Sagittarius C Region
Authors: Tsuru Takeshi Go , Nobukawa Masayoshi , Nakajima Hiroshi , Matsumoto Hironori , Koyama Katsuji , Yamauchi Shigeo
Published: March 2014

We present the Suzaku results on a new candidate of a supernova remnant (SNR) in the Sagittarius C region. We detected diffuse X-rays of an elliptical shape (G359.41$-$0.12) and a chimney-like structure (the Chimney), both of which were fitted with a thin thermal the model of $k_{\rm B}T$$\sim$ 1 keV temperature. The absorption columns are same between these two structures, indicating that both are located at the same distance in the same line of sight. The narrow band image and one-dimensional profile of S xv K$\alpha$ at 2.45 keV show that the Chimney is emanating from G359.41$-$0.12. Therefore, these two sources are physically connected with each other. The sum of the thermal energies of the Chimney and G359.41$-$0.12 is estimated to be 1.4 $\times$ 10$^{50}$erg, typical for a galactic SNR. G359.41$-$0.12 is likely to be a new SNR candidate and the Chimney is an associated outflow.
X-Ray Reflection Nebulae with Large Equivalent Widths of the Neutral Iron K$\alpha$ Line in the Sagittarius C Region
Authors: Nakajima Hiroshi , Tsuru Takeshi Go , Nobukawa Masayoshi , Matsumoto Hironori , Koyama Katsuji , Murakami Hiroshi , Senda Atsushi , Yamauchi Shigeo
Published: March 2014

This paper reports on the first results of a Suzaku observation in the Sgr C region. We detected four diffuse clumps with strong line emission at 6.4 keV, K$\alpha$ from neutral or low-ionized Fe. One of them, M359.38$-$0.00, was newly discovered with Suzaku. The X-ray spectra of the two bright clumps, M359.43$-$0.07 and M359.47$-$0.15, after subtracting the galactic center diffuse X-ray emission (GCDX), exhibit a strong K$\alpha$ line from Fe i with large equivalent widths ($EW$s) of 2.0–2.2 keV and a clear K$\beta$ of Fe i. The GCDX in the Sgr C region is composed of the 6.4 keV- and 6.7 keV-associated components. These were phenomenologically decomposed by taking relations between the $EW$s of the 6.4 keV and 6.7 keV lines. Then, the former $EW$s against the associated continuum in bright clump regions were estimated to be 2.4$^{+2.3}_{-0.7}$keV. Since the two different approaches give similar large $EW$s of 2 keV, we strongly suggest that the 6.4 keV clumps in the Sgr C region are due to X-ray reflection/fluorescence (the X-ray reflection nebulae).
Time Variability of the Neutral Iron Lines from the Sagittarius B2 Region and Its Implication of a Past Outburst of Sagittarius A$^\ast$
Authors: Inui Tatsuya , Koyama Katsuji , Matsumoto Hironori , Tsuru Takeshi Go
Published: March 2014

We investigated long-term X-ray behavior from the Sgr B2 complex using archival data of the X-ray satellites Suzaku, XMM-Newton, Chandra, and ASCA. The observed region of the Sgr B2 complex included two prominent spots in the FeI K$\alpha$ line at 6.40 keV, a giant molecular cloud, M0.66$-$0.02, known as the “Sgr B2 cloud” and an unusual X-ray source, G0.570$-$0.018. Although these 6.40 keV spots have spatial extensions of a few parsec scale, the morphology and flux of the 6.40 keV line has been time variable for 10 years, in contrast to the constant flux of the Fe XXV K$\alpha$ line at 6.67 keV in the Galactic diffuse X-ray emission. This time variation is mostly due to M0.66$-$0.02; the 6.40 keV line flux declined in 2001, and decreased to 60% in the time span 1994–2005. The other spot, G0.570$-$0.018, is found to be conspicuous only in the Chandra observation in 2000. From the long-term time variability ($\sim$10 years) of the Sgr B2 complex, we infer that the Galactic Center black hole Sgr A$^\ast$ was X-ray bright in the past 300 years, and exhibited a time variability with a period of a few years.