bluuebunny/crossref_metadata_2025_split huggingface dataset:
Variation of Molecular Gas Properties Across the Spiral Arms in IC 342: Large-Scale 13CO (1–0) Emission
Authors: Hirota Akihiko , Kuno Nario , Sato Naoko , Nakanishi Hiroyuki , Tosaki Tomoka , Sorai Kazuo 
Published: March 2014

Abstract
We present a $^{13}$CO (1–0) mapping survey of the nearby galaxy IC 342 carried out with the Nobeyama 45 m radio telescope. The map covers a 320$^{\prime\prime} \times$ 320$^{\prime\prime}$ region, including its center, bar, and most of one of the spiral arms. The $^{13}$CO (1–0) data were compared with $^{12}$CO (1–0), H$\alpha$, 24$\ \mu$m, and $K_{\rm s}$-band images to investigate spatial relations among molecular clouds, star-forming regions, and the stellar potential. The line ratio between both CO lines, $I$[$^{13}$CO (1–0)]$/I$[$^{12}$CO (1–0)] $\equiv R_{13/12}$, was also derived to investigate the variation of molecular gas properties. The mean value of $R_{13/12}$ in the center of IC 342 is low ($\sim\ $0.10$\ \pm\ $0.01) compared to the disk region ($\sim\ $0.15$\ \pm\ $0.01). While $R_{13/12}$ in the central region is rather uniform, significant variations of $R_{13/12}$ were found in the spiral arms; that is, while it is low ($\sim\ $0.1) at both ends of the bar and at the giant molecular cloud association (GMA) found in the spiral arm, it is high (0.14–0.20) downstream from the low $R_{13/12}$ region. The low- and high-$R_{13/12}$ regions in the disk correspond to the $^{12}$CO peak and star-forming regions, respectively. The low $R_{13/12}$ in the galactic center is likely due to the higher gas temperature in the starburst region. The most probable explanation of the $R_{13/12}$ variation in the disk is that a low $R_{13/12}$ in the GMA and the ends of the bar reflects an increased fraction of the diffuse molecular component, which has a low column density and low volume density. Around the GMA and the north end of the bar, not only are the star-forming regions downstream from the CO distributions, but $R_{13/12}$ is also higher downstream, implying the presence of gas compression and ionized/molecular gas spatial offsets, as predicted by density wave models.
A Catalog of Suzaku/WAM Hard X-Ray Solar Flares
Authors: Endo Akira , Minoshima Takashi , Morigami Kouichi , Suzuki Masanobu , Shimamori Atsushi , Sato Yumi , Terada Yukikatsu , Tashiro Makoto S. , Urata Yuji , Sonoda Eri , Yamaoka Kazutaka , Sugita Satoshi , Watanabe Kyoko 
Published: March 2014

Abstract
We developed a catalog of solar flares in the hard X-ray band observed with the Wide-band All-sky Monitor (WAM) onboard the Suzaku satellite between 2005 July and 2009 November. During this period, 105 solar flares (GOES class X: 13, M: 29, C: 47, B: 16) were detected with WAM, including 10% of GOES-class C events reported during the same period. The observed photon flux ranged between 9 $\times$ 10$^{-5}$ and 9 $\times$ 10$^{-1}\ $photons s$^{-1}\ $cm$^{-2}\ $keV$^{-1}\ $ at 100 keV. The averaged hard X-ray spectrum for each solar flare was evaluated for 70 of the 105 events, and 43 of them were well fitted with a single power-law model with a photon index ranging between $-$7 and $-$3. We observed a weak trend where events with longer durations exhibited harder spectral slopes.
MAXI GSC Observations of a Spectral State Transition in the Black Hole Candidate XTE J1752–223
Authors: Nakahira Satoshi , Yamaoka Kazutaka , Sugizaki Mutsumi , Ueda Yoshihiro , Negoro Hitoshi , Ebisawa Ken , Kawai Nobuyuki , Matsuoka Masaru , Tsunemi Hiroshi , Daikyuji Arata , Eguchi Satoshi , Hiroi Kazuo , Ishikawa Ryoji , Ishiwata Masaki , Isobe Naoki , Kawasaki Kazuyoshi , Kimura Masashi , Kohama Mitsuhiro , Mihara Tatehiro , Miyoshi Sho , Morii Mikio , Nakagawa Yujin E. , Nakajima Motoki , Ozawa Hiroshi , Sootome Tetsuya , Sugimori Kousuke , Suzuki Motoko , Tomida Hiroshi , Ueno Shiro , Yamamoto Takayuki , Yoshida Atsumasa ,   team the MAXI
Published: March 2014

Abstract
We present the first results on the black-hole candidate XTE J1752$-$223 from the Gas Slit Camera (GSC) aboard the Monitor of All-sky X-ray Image (MAXI) on the International Space Station. Including the onset of an outburst reported by the Proportional Counter Array aboard the Rossi X-ray Timing Explorer on 2009 October 23, MAXI / GSC has been monitoring this source approximately 10 times per day with high sensitivity in the 2–20 keV band. XTE J1752$-$223 was initially in a low / hard state during the first 3 months. An anti-correlated behavior between the 2–4 keV and 4–20 keV bands was observed around 2010 January 20, indicating that the source exhibited a spectral transition to the high / soft state. A transient radio jet may have been ejected when the source was in the intermediate state where the spectrum was roughly explained by a power-law with a photon index of 2.5–3.0. The unusually long period in the initial low / hard state implies a slow variation in the mass-accretion rate, and a dramatic soft X-ray increase may be explained by a sudden appearance of the accretion disk component with a relatively low innermost temperature (0.4–0.7 keV). Such a low temperature might suggest that the maximum accretion rate was just above the critical gas-evaporation rate required for the state transition.
Early Spectroscopy of the 2010 Outburst of U Scorpii
Authors: Yamanaka Masayuki , Uemura Makoto , Kawabata Koji S. , Fujii Mitsugu , Tanabe Kenji , Imamura Kazuyoshi , Komatsu Tomoyuki , Arai Akira , Sasada Mahito , Itoh Ryosuke , Harao Tatsuya , Kunitomi Nanae , Nagae Osamu , Nose Mikiha , Ohsugi Takashi , Okushima Takako , Sakimoto Kiyoshi , Yoshida Michitoshi 
Published: March 2014

Abstract
We present early spectroscopy of the recurrent nova U Sco during an outburst in 2010. We successfully obtained time-series spectra during the period of $t_{\rm d} =$ 0.37–0.44 d, where $t_{\rm d}$ is the time that elapsed since the discovery of the present outburst. This is the first time-resolved spectroscopy on the first night of U Sco outbursts. At $t_{\rm d} \sim$ 0.4 d, the H$\alpha$ line consists of a blue-shifted ($-$5000 km s$^{-1}$) narrow absorption component and a wide, triple-peak emission one: blue ($\sim-$3000 km s$^{-1}$), central ($\sim$0 km s$^{-1}$), and red ($\sim+$3000 km s$^{-1}$) peaks. The blue and red peaks developed more rapidly than the central one for the first night. This rapid variation would be caused by the growth of aspherical wind produced during the earliest stage of the outburst. At $t_{\rm d} =$ 1.4 d, the H$\alpha$ line has a nearly flat-topped profile with weak blue and red peaks at $\sim \pm$3000 km s$^{-1}$. This profile can be attributed to a nearly spherical shell, while the asphericity growing on the first night still remains. The wind asphericity is less significant after $t_{\rm d} =$ 9 d.
A Novel Jet Model: Magnetically Collimated, Radiation-Pressure Driven Jet
Authors: Takeuchi Shun , Ohsuga Ken , Mineshige Shin 
Published: March 2014

Abstract
Relativistic jets from compact objects are ubiquitous phenomena in the Unvierse, but their driving mechanism has been an enigmatic issue for several decades. Two basic models have been extensively discussed: magnetohydrodynamic (MHD) jets and radiation-hydrodynamic (RHD) jets. Currently, the former is more widely accepted, since the magnetic field is expected to provide both acceleration and collimation mechanisms, whereas the radiation field cannot collimate the outflow. Here, we propose a new type of jets, radiation-magnetohydrodynamic (RMHD) jets, based on our global RMHD simulation of luminous accretion flows onto a black hole shining above the Eddington luminosity. The RMHD jet can be accelerated up to relativistic speed by the radiation-pressure force and collimated by the Lorentz force of a magnetic tower structure inflated by toroidal magnetic field lines accumulated around the black hole, though the radiation energy greatly dominates over the magnetic energy. This magnetic tower is collimated by a geometrically thick accretion flow supported by a radiation-pressure force. This type of jet may explain relativistic jets from Galactic microquasars, appearing at high luminosity.
Origin of Molecular Outflow Determined from Thermal Dust Polarization
Authors: Tomisaka Kohji 
Published: March 2014

Abstract
The observational expectation of polarization measurements of thermal dust radiation is investigated to find information on molecular outflows based on magnetohydrodynamical (MHD) and radiation-transfer simulations. There are two major proposed models for driving of molecular outflows: (1) molecular gas is accelerated by magnetic pressure gradient or magnetocentrifugal wind mechanism before the magnetic field and molecular gas are decoupled, (2) the linear momentum of a highly collimated jet is transferred to the ambient molecular gas. In order to distinguish between these two models, it is crucial to observe the configuration of the magnetic field. An observation of a toroidal magnetic field would be strong evidence that the first model is appropriate. We calculated the polarization distribution of thermal dust radiation due to the alignment of dust grains along the magnetic field using molecular outflow data obtained from two-dimensional axisymmetric MHD simulations. An asymmetric distribution around the $z$-axis is characteristic for magnetic fields composed of both poloidal and toroidal components. We found that the outflow has a low polarization degree compared with the envelope and that the envelope and outflow have different polarization directions (B-vector); i.e., the magnetic field within the envelope is parallel to the global magnetic field lines while the magnetic field of the outflow is perpendicular to it. We, then, demonstrated that the point-symmetric (rather than axisymmetric) distributions of low polarization regions indicate that molecular outflows are likely to be magnetically driven. Observations of this polarization distribution with tools such as ALMA would confirm the origin of the molecular outflow.
SiO Maser Spectra of V407 Cygni after the 2010 March Nova Outburst
Authors: Deguchi Shuji , Koike Kazutaka , Kuno Nario , Matsunaga Noriyuki , Nakashima Jun-ichi , Takahashi Shigeru 
Published: March 2014

Abstract
We report on the time variation of SiO maser emission from the symbiotic stellar system V407 Cygni after the classical nova outburst on 2010 March 10. Although both the SiO $J$$=$ 1–0 $v$$=$ 1 and 2 lines at 43.122 and 42.821 GHz were found previously in the envelope of a mira in the binary system, only weak emission of the $J$$=$ 1–0 $v$$=$ 2 line has continuously been detectable after the nova outburst. The line profile exhibited a dramatic change several weeks after the burst; the component on the higher-velocity side of the systemic velocity disappeared two weeks after the burst, and a new persistent component appeared on the lower-velocity side later. These observations indicate that the SiO emitting regions were wiped out on a time scale of two weeks by the nova shock, but a part of the masing region was quickly replenished by cool molecular gases expelled by the mira pulsation.
Astrometry of Galactic Star-Forming Region ON 2 N with VERA: Estimation of the Galactic Constants
Authors: Ando Kazuma , Nagayama Takumi , Omodaka Toshihiro , Handa Toshihiro , Imai Hiroshi , Nakagawa Akiharu , Nakanishi Hiroyuki , Honma Mareki , Kobayashi Hideyuki , Miyaji Takeshi 
Published: March 2014

Abstract
We performed the astrometry of H$_2$O masers in the Galactic star-forming region Onsala 2 North (ON 2 N) with the VLBI Exploration of Radio Astrometry (VERA). We obtained a trigonometric parallax of 0.261$\ \pm\ $0.009 mas, corresponding to a heliocentric distance of 3.83$\ \pm\ $0.13 kpc. ON 2 N is expected to be on the solar circle, because its radial velocity with respect to the local standard of rest (LSR) is nearly zero. By using the present parallax and proper motions of the masers, the galactocentric distance of the Sun and the Galactic rotation velocity at the Sun are found to be $R_0$$=$ 7.80$\ \pm\ $0.26 kpc and $\Theta_0$$=$ 213$\ \pm\ $5 km s$^{-1}$, respectively. The ratio of Galactic constants, namely the angular rotation velocity of the LSR, can be determined more precisely, and is found to be $\Omega_0$$=$$\Theta_0/R_0$$=$ 27.3$\ \pm\ $0.8 km s$^{-1}$kpc$^{-1}$, which is consistent with recent estimations, but different from 25.9 km s$^{-1}$kpc$^{-1}$ derived from the recommended values of $\Theta_0$ and $R_0$ by the International Astronomical Union (1985).
Annual Parallax Distance and Kinematical Property of H2O Masers in IRAS 19312+1950
Authors: Imai Hiroshi , Tafoya Daniel , Honma Mareki , Hirota Tomoya , Miyaji Takeshi 
Published: March 2014

Abstract
We report on results of astrometric observations of H$_{2}$O masers in the pre-planetary nebula candidate source IRAS 19312$+$1950 with the VLBI Exploration of Radio Astrometry (VERA), yielding an annual parallax, $\pi$$=$ 263$\ \pm\ $47$\ \mu$as, and a secular motion, ($\mu_{\alpha}$, $\mu_{\delta}$) $=$ ($-$2.61$\ \pm\ $0.47, $-$6.73$\ \pm\ $0.14) [mas yr$^{-1}$], for IRAS 19312$+$1950. We then derived a heliocentric distance of $D$$=$ 3.80$^{+0.83}_{\-0.58}\ $kpc, a location in the Galaxy ($R$, $z$) $=$ (7.07$\ \pm\ $0.12 kpc, 28$\ \pm\ $3 pc), and a three-dimensional velocity vector ($V_{R}$, $V_{\theta}$, $V_{z}$) $=$ (33$\ \pm\ $28, 214$\ \pm\ $4, $-$14$\ \pm\ $8) [km s$^{-1}$] in galactic cylindrical coordinates. Based on these parameters, we discuss the intrinsic properties of IRAS 19312$+$1950. We estimated the mass of the central star to be $\sim\ $8$\ M_{\odot}$ and the deviation of the source motion from the circular galactic rotation to be $\sim\ $40 km s$^{-1}$. These are consistent with this source being an intermediate-mass late AGB or early post-AGB star.
Vibrational Instability of Population III Low-Mass Stars due to the ε-Mechanism
Authors: Sonoi Takafumi , Shibahashi Hiromoto 
Published: March 2014

Abstract
The linear vibrational instability of population III low-mass stars due to the $\varepsilon $-mechanism was investigated against g modes by using the quasi-adiabatic approximation. Since, contrary to the case of population I stars, such stars ($M$$\gtrsim$ 1$\ {M_\odot}$) have no convective envelope, a definite conclusion of the stability is obtained. It is found that stars with $M$$\lesssim$ 5$\ {M_\odot}$ become unstable during the main-sequence stage against the dipole g$_1$, g$_2$, and g$_3$ modes due to the $\varepsilon $-mechanism of $^3$He–$^3$He reaction. The $e$-folding time of the instability is on the order of 10$^{7}\ $yr, and is much shorter than the evolutionary timescale. It is thus expected that the instability grows to a finite size and induces material mixing, which has a significant influence on the later evolution of these stars.
Suzaku Discovery of a Hard Component Varying Independently of the Power-Law Emission in MCG −6–30–15
Authors: Noda Hirofumi , Makishima Kazuo , Uehara Yuuichi , Yamada Shin'ya , Nakazawa Kazuhiro 
Published: March 2014

Abstract
Focusing on hard X-ray variability, we reanalyzed Suzaku data of the Type I Seyfert galaxy MCG–6–30–15 obtained in 2006. Intensity-sorted spectroscopy and a principal-component analysis consistently revealed a very hard component that varies independently of the dominant power-law emission. Although the exact nature of this hard component has not yet been identified, it can be modeled as a power-law with a photon index of $\sim\ $2 affected by a partial covering absorption, or as a thermal Comptonization emission with a relatively large optical depth. When this component is included in the fitting model, the time-averaged 2.5–55 keV spectrum of MCG–6–30–15 can be reproduced successfully by invoking a mildly broadened iron line with its emission region located at $\gtrsim\ $8 times the gravitational radii from the central black hole, and a moderate reflection with a covering fraction of $\sim\ $3.4$\pi$. This result implies that the solution of a highly spinning black hole in MCG–6–30–15, obtained by Miniutti et al. (2007, PASJ, 59, S315) using the same Suzaku data as ours, is a model-dependent result.
High-Resolution Optical and Near-Infrared Images of the FS Tauri Circumbinary Disk
Authors: Hioki Tomonori , Itoh Yoichi , Oasa Yumiko , Fukagawa Misato , Hayashi Masahiko 
Published: March 2014

Abstract
We present an $H$-band image of FS Tauri, a 0$''\!\!\!.$2-separated classical T Tauri binary system, taken with the Coronagraphic Imager with Adaptive Optics (CIAO) on the Subaru Telescope. This new image, combined with Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) F606W-band polarimetric images, shows that the binary has complicated circumbinary features, including a circumbinary disk, western and eastern arm-like structures, and two cavities at the northeast and southwest. The circumbinary disk is 630 AU in radius and the southeast side of the disk is bright in the $H$-band. The brightness ratio (southeast$/$northwest) is 1.6$\ \pm\ $0.4. A single Rayleigh-like scattering model indicates that the disk is inclined by 30$^{\circ}$ to 40$^{\circ}$ and that the southeast side corresponds to the near side along our line of sight. The $H$-band surface brightness of the southeast side decreases as $r^{-1.9\pm0.1}$ from 15.2 mag arcsec$^{-2}$ to 16.8 mag arcsec$^{-2}$. The outer portion of the disk is possibly more flared than its inner portion. The weak centro-symmetric polarization pattern and redder F606W $-$$H$ color (4.2 $\ \pm\ $ 0.2 mag) of the southeast side are probably caused by multiple-scattering events from dust grains associated with the binary. The F606W-band image shows the bright northwest side of the disk in contrast with the $H$-band image. The F606W $-$$H$ color of the northwest side is between 1.7 mag and 3.0 mag. We consider that Haro 6-5 B (FS Tauri B), 20$''$ away, produces neutral scattered light from the northwest side. This idea is supported by the polarization pattern of the northwest side, which is centro-symmetric with respect to Haro 6-5 B. The arms appear to encompass the western and eastern cavities, suggesting that the arms $+$ cavity systems are created by a bipolar outflow from the binary. However, the direction of this outflow is inconsistent with that of outflows inferred from the circumbinary disk model. These differences may arise from a misalignment between the circumbinary disk and the circumstellar disks. Another mechanism forming the arms $+$ cavity systems is considered to be the inhomogeneous density distribution of materials in the circumbinary disk.
Multicolor Photometry of the Galaxies in Abell 1775: Substructures, Luminosity Functions, and Star-Formation Properties
Authors: Zhang Li , Yuan Qirong , Yang Qian , Zhang Shiyan , Li Feng , Zhou Xu , Jiang Zhaoji 
Published: March 2014

Abstract
An optical photometric observation in 15 bands was carried out for the nearby galaxy cluster Abell 1775 (A 1775) by the Beijing-Arizona-Taiwan-Connecticut (BATC) multi-color system. Over 5000 sources’ spectral energy distributions (SEDs) were obtained. Since this cluster has also been observed by the Sloan Digital Sky Survey (SDSS), the BATC SEDs were combined with the SDSS five-band photometric data. Using the combined SEDs, 146 faint galaxies were selected as new member galaxies by the photometric redshift technique. Based on the positions, redshifts, and 20-band SEDs of member galaxies, dynamical substructures and luminosity functions (LFs) of A 1775 were investigated. The previous reported bimodal structure of A 1775 has been confirmed: a poor subcluster with lower redshift, A 1775 A, is located $\sim$ 14$\prime$ southeast to the main concentration, A 1775 B. After taking into account the new supplemented member galaxies, a new subcluster, A 1775 C, was found along the aligned direction of A 1775 A and A 1775 B. The different LF faint ends of the two subclusters indicate that A 1775 B is a more dynamically evolved system, while A 1775 A is still dynamically young. By using the STARLIGHT spectral synthesis code, the star-formation histories of the member galaxies were studied. The dependence of the mean stellar ages upon the Hubble type was confirmed, and the environmental effect on star-formation activities for galaxies in A 1775 B has been explored.
Gamma-Ray Burst Polarimeter (GAP) aboard the Small Solar Power Sail Demonstrator IKAROS
Authors: Yonetoku Daisuke , Murakami Toshio , Gunji Shuichi , Mihara Tatehiro , Sakashita Tomonori , Morihara Yoshiyuki , Kikuchi Yukihiro , Takahashi Takuya , Fujimoto Hirofumi , Toukairin Noriyuki , Kodama Yoshiki , Kubo Shin ,   Ikaros Demonstration Team
Published: March 2014

Abstract
The small solar-power sail demonstrator ``IKAROS'' is a Japanese engineering verification spacecraft launched by the H-IIA rocket on 2010 May 21 at Japan Aerospace Exploration Agency (JAXA) Tanegashima Space Center. IKAROS has a 20 m diameter sail, which is made of a thin polyimide membrane. The sail converts the solar radiation-pressure into the propulsion force of IKAROS, and accelerates the spacecraft. The Gamma-Ray Burst Polarimeter (GAP) aboard IKAROS is the first polarimeter specifically designed to measure the polarization of Gamma-Ray Bursts (GRBs) from space, and will do so in the cruising phase of the IKAROS mission. GAP is a modest detector of 3.8 kg in weight and 17 cm in size with an energy range of between 50–300 keV. The GAP detector is now a member of the interplanetary network (IPN) for determining the GRB direction. The detection principle of gamma-ray polarization is the anisotropy of the Compton scattering. Coincidence between the central plastic Compton scattering medium and discrete CsI detectors distributed around the sides of the plastic defines the Compton-scattering angle, which is expected to show an angular dependence if polarization is present in a given GRB. In this paper, we present the GAP detector and its ground-based and onboard calibrations.
Age Determinations of Early-M Type Pre-Main Sequence Stars Using a High-Resolution Near-Infrared Spectroscopic Method
Authors: Takagi Yuhei , Itoh Yoichi , Oasa Yumiko , Sugitani Koji 
Published: March 2014

Abstract
We present a method for determining the age of early-M type pre-main sequence (PMS) stars based on estimations of the surface gravity. The surface gravity was measured using high-resolution near-infrared K-band spectroscopy. The age of the PMS stars can be determined from the surface gravity, which correlates with the photospheric contraction. To estimate the surface gravity while avoiding veiling contamination, we developed a surface gravity indicator using equivalent width ratios (EWRs) of nearby absorption lines. We derived a relationship between the ratios of the Sc (22057.8 Å and 22071.3 Å) and Na (22062.4 Å and 22089.7 Å) absorption lines and the surface gravity by observing giants and main-sequence stars. The surface gravities of early-M type stars were determined with an accuracy of 0.1 in log$g$. The ages of target PMS stars were estimated within a factor of 1.5 by comparing the surface gravity with the evolution model of Baraffe et al. (1998, A&A, 337, 403). The ages of 4 PMS stars were estimated to be older than indicated by previous age determinations made using the photometric method. The EWR method allows estimating the age of PMS stars without contaminating the uncertainty of the distance, extinction, and veiling.