bluuebunny/crossref_metadata_2025 huggingface dataset:
WIDGET: System Performance and GRB Prompt Optical Observations
Authors: Urata Yuji , Tashiro Makoto S. , Tamagawa Toru , Usui Fumihiko , Kuwahara Makoto , Lin Hungmiao , Kageyama Shoichi , Iwakiri Wataru , Sugasahara Takako , Takahara Kazuki , Kodaka Natsuki , Abe Keiichi , Masuno Keisuke , Onda Kaori
Published: March 2014

The WIDeField telescope for Gamma-ray burst Early Timing (WIDGET) is used for a fully automated, ultra-wide-field survey aimed at detecting the prompt optical emission associated with Gamma-ray Bursts (GRBs). WIDGET surveys the HETE-2 and Swift/BAT pointing directions, covering a total field of view of 62$^{\circ}$$\times$ 62$^{\circ}$ every 10 secounds using a unfiltered system. This monitoring survey allows the exploration of optical emission before the $\gamma $-ray trigger. The unfiltered magnitude is well converted to the SDSS $r'$ system at a 0.1 mag level. Since 2004, WIDGET has made a total of ten simultaneous and one pre-trigger GRB observations. The efficiency of synchronized observations with HETE-2 is four-times better than that of Swift. There has been no bright optical emission similar to that from GRB 080319B. A statistical analysis implies that GRB 080319B is a rare event. This paper summarizes the design and operation of the WIDGET system and the simultaneous GRB observations obtained with this instrument.
Origin of Molecular Outflow Determined from Thermal Dust Polarization
Authors: Tomisaka Kohji
Published: March 2014

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

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

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

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

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.
Resonant Excitation of Disk Oscillations in Deformed Disks IV: A New Formulation Studying Stability
Authors: Kato Shoji , Okazaki Atsuo T. , Finny Oktariani
Published: March 2014

The possibility has been suggested that high-frequency quasi-periodic oscillations observed in low-mass X-ray binaries are resonantly excited disk oscillations in deformed (warped or eccentric) relativistic disks (Kato 2004). In this paper we examine this wave excitation process from a viewpoint somewhat different from that of previous studies. We consider how amplitudes of a set of normal mode oscillations change secularly with time by their mutual couplings through disk deformation. As a first step, we consider the case where the number of oscillation modes contributing to the resonance coupling is two. The results show that two prograde oscillations interacting through disk deformation can grow if their wave energies have opposite signs.
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

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

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

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

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

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.
Propagation of Moreton Waves
Authors: Zhang Yuzong , Kitai Reizaburo , Narukage Noriyuki , Matsumoto Takuma , Ueno Satoru , Shibata Kazunari , Wang Jingxiu
Published: March 2014

With the Flare-Monitoring Telescope (FMT) and Solar Magnetic Activity Research Telescope (SMART) at Hida observatory of Kyoto University, 13 events of Moreton waves were captured at H$\alpha$ center, H$\alpha$  $\pm$0.5 Å, and H$\alpha$  $\pm$0.8 Å wavebands since 1997. With such samples, we have studied the statistical properties of the propagation of Moreton waves. Moreton waves were all restricted in sectorial zones with a mean value of 92$^\circ$. However, their accompanying EIT waves, observed simultaneously with SOHO/EIT at extreme-ultraviolet wavelength, were very isotropic with a quite extended scope of 193$^\circ$. The average propagation speeds of the Moreton waves and the corresponding EIT waves were 664 km s$^{-1}$ and 205 km s$^{-1}$, respectively. Moreton waves propagated either under large-scale close magnetic flux loops, or firstly in the sectorial region where two sets of magnetic loops separated from each other and diverged, and then stopped before the open magnetic flux region. The location swept by Moreton waves had a relatively weak magnetic field as compared to the magnetic fields at their sidewalls. The ratio of the magnetic flux density between the sidewall and the path falls in the range of 1.4 to 3.7 at a height of 0.01 solar radii. Additionally, we roughly estimated the distribution of the fast magnetosonic speed between the propagating path and sidewalls in an event on 1997 November 3, and found a relatively low-fast magnetosonic speed in the path. We also found that the propagating direction of Moreton waves coincided with the direction of filament eruption in a few well-observed events. This favors an interpretation of the “Piston” model, although further studies are necessary for any definitive conclusion.
Beryllium Abundances of Solar-Analog Stars
Authors: Takeda Yoichi , Tajitsu Akito , Honda Satoshi , Kawanomoto Satoshi , Ando Hiroyasu , Sakurai Takashi
Published: March 2014

An extensive Be abundance analysis was conducted for 118 solar analogs (along with 87 FGK standard stars) by applying the spectrum synthesis technique to the near-UV region comprising the Be II line at 3131.066 Å, in an attempt to investigate whether Be suffers any depletion, such as in the case of Li showing a large diversity. We found that, while most of these Sun-like stars are superficially similar in terms of their $A$(Be) (Be abundances) around the solar value within $\sim\pm$0.2 dex, 4 out of 118 samples turned out to be strikingly Be-deficient (by more than $\sim\ $2 dex), and these 4 stars belong to the group of lowest $v_{\rm e}$ sin $i$ (projected rotation velocity). Moreover, even for the other majority showing an apparent similarity in Be, we can recognize a tendency that $A$(Be) gradually increases with an increase in $v_{\rm e}$ sin $i$. These observational facts suggest that any solar analog star (including the Sun) generally suffers some kind of Be depletion during their lives, where the rotational velocity (or the angular momentum) plays an important role in the sense that the depletion tends to be enhanced by slower rotation. Hence, our findings require that the occasionally stated view “G-type dwarfs with $T_{\rm eff}$$\lesssim$ 6000 K are essentially homogeneous in Be with their original composition retained” should be revised. Also, our analysis indicates that the difference of $\sim\ $0.2 dex in $A$(Be) between the solar photosphere and the meteorite really exists, implying that the “UV missing opacity” is irrelevant at least for this Be II line.
Testing Two-Component Jet Models of GRBs with Orphan Afterglows
Authors: Inayoshi Kohei , Tsutsui Ryo
Published: March 2014

In the Swift era, two-component jet models were introduced to explain the complex temporal profiles and the diversity of early afterglows. In this paper, we concentrate on the two-component jet model: the first component is the conventional afterglow, and second is emission due to late internal dissipation, such as late-prompt emission. We suggest herein that the two-component jet model can be probed by the existence of two optical peaks for orphan GRB afterglows. Each peak is caused by its respective jet as its relativistic beaming cone widens to encompass the off-axis line of sight. Typically, the first peak appears at 10$^{4}$–10$^{5}\ $s, and the second at 10$^{5}\ $–10$^{6}\ $s. Furthermore, we expect to observe a single, bright X-ray peak at the same time as the first optical peak. Because orphan afterglows do not have prompt emission, it is necessary to monitor the entire sky every 10$^{4}$s in the X-ray regime. We can test the model with orphan afterglows through the X-ray all-sky survey collaboration, and by using ground-based optical telescopes.
Physical Relation of Source I to IRc2 in the Orion KL Region
Authors: Okumura Shin-ichiro , Yamashita Takuya , Sako Shigeyuki , Miyata Takashi , Honda Mitsuhiko , Kataza Hirokazu , Okamoto Yoshiko K.
Published: March 2014

We present mid-infrared narrow-band images of the Orion BN/KL region, and $N$-band low-resolution spectra of IRc2 and the nearby radio source ``I''. The distributions of the silicate absorption strength and the color temperature have been revealed with a subarcsec resolution. The detailed structure of the 7.8$\ \mu$m$/$12.4$\ \mu$m color temperature distribution was resolved in the vicinity of IRc2. A mid-infrared counterpart to source I has been detected as a large color temperature peak. The color temperature distribution shows an increasing gradient from IRc2 toward source I, and no dominant temperature peak is seen at IRc2. The spectral energy distribution of IRc2 could be fitted by a two-temperature component model, and the ``warmer component'' of the infrared emission from IRc2 could be reproduced by scattering of radiation from source I. IRc2 itself is not self-luminous, but is illuminated and heated by an embedded luminous young stellar object located at source I.
Wind Anisotropy and Angular Momentum Loss in a Massive Rotating Binary System
Authors: Song Han-Feng , Lu Yuan , Wang Jing-Zhou
Published: March 2014

The model of anisotropic loss of the mass and angular momentum is constructed and the non-conservative evolution of the binary system is investigated in this paper. The joint effects of the centrifugal force and tidal force cause the configurations of two components to become triaxial ellipsoids. The high-order disturbing potential, which includes the rotational and tidal distortions, is applied to describe the local gravity in a close binary system. The $g_{\rm eff}$($\theta$, $\varphi$)-effect dominates the mass-loss distribution in the massive O-type star. Both the $g_{\rm eff}$($\theta$, $\varphi$)-effect and the $\kappa$-effect have an important influence on the equatorial ejection, and the Roche lobe overflow and the H-shell burning occur earlier in the rotational models. The rotation and tide can intensify the mass loss before mass overflow, and the rate of stellar wind goes down, resulting from a decrease of the luminosity in the subsequent stages. The high-order disturbing potential and other associated physical factors may significantly affect the Roche lobe and might be possible to drive the non-conservative mass transfer process when the stars approach the break-up rotation. Rotation and tide can allow the primary to shift towards the blue side of the HR diagram and modify the thermal relaxation time-scale in the slow phase of the mass transfer in Case A. The star attempts to attain thermal equilibrium and displays a slightly cyclical expansion and contraction. When stellar wind was taken into consideration in the model, the secondary star accreted less mass than the model without stellar wind.
Multi-Color Coronagraph Experiment in a Vacuum Testbed with a Binary Shaped Pupil Mask
Authors: Haze Kanae , Enya Keigo , Abe Lyu , Kotani Takayuki , Nakagawa Takao , Sato Toshimichi , Yamamuro Tomoyasu
Published: March 2014

We conducted a number of multi-color/broadband coronagraph experiments using a vacuum chamber and a binary-shaped pupil mask, which in principle should work at all wavelengths, in the context of the research and development of a stellar coronagraph to observe extra-solar planets (exoplanets) directly. The aim of this work is to demonstrate that subtraction of the Point Spread Function (PSF) and multi-color/broadband experiments using a binary-shaped pupil mask coronagraph would help to improve the contrast in observations of exoplanets. A checkerboard mask, a kind of binary-shaped pupil mask, was used. We improved the temperature stability by installing the coronagraph optics in a vacuum chamber, while controlling the temperature of the optical bench, and covering the vacuum chamber with thermal insulation layers. Active wavefront control was not applied in this work. We evaluated how much the PSF subtraction contributed to the high-contrast observation by subtracting images obtained through the coronagraph. We also carried out multi-color/broadband experiments in order to demonstrate a more realistic observation using Super luminescent Light Emitting Diodes (SLEDs) with center wavelengths of 650 nm, 750 nm, 800 nm, and 850 nm. A contrast of 2.3 $\times$ 10$^{-7}$ was obtained for the raw coronagraphic image and a contrast of 1.3 $\times$ 10$^{-9}$ was achieved after PSF subtraction with a He-Ne laser at 632.8 nm wavelength. Thus, the contrast was improved by around two orders of magnitude from the raw contrast by subtracting the PSF. We achieved contrasts of 3.1 $\times$ 10$^{-7}$, 1.1 $\times$ 10$^{-6}$, 1.6 $\times$ 10$^{-6}$, and 2.5 $\times$ 10$^{-6}$ at the bands of 650 nm, 750 nm, 800 nm, and 850 nm, respectively, in multi-color/broadband experiments. The results show that the contrast within each of the wavelength bands was significantly improved compared with the non-coronagraphic optics. We demonstrated that PSF subtraction is potentially beneficial for improving the contrast of a binary-shaped pupil mask coronagraph; this coronagraph produces a significant improvement in contrast with multi-color/broadband light sources.
Hydrodynamic Interaction between the Be Star and the Pulsar in the TeV Binary PSR B1259$-$63/LS 2883
Authors: Okazaki Atsuo T. , Nagataki Shigehiro , Naito Tsuguya , Kawachi Akiko , Hayasaki Kimitake , Owocki Stanley P. , Takata Jumpei
Published: March 2014

We have been studying the interaction between the Be star and the pulsar in the TeV binary PSR B1259$-$63/LS 2883, using 3-D SPH simulations of the tidal and wind interactions in this Be–pulsar system. We first ran a simulation without pulsar wind nor Be wind, while taking into account only the gravitational effect of the pulsar on the Be disk. In this simulation, the gas particles are ejected at a constant rate from the equatorial surface of the Be star, which is tilted in a direction consistent with multi-waveband observations. We ran the simulation until the Be disk was fully developed and started to repeat a regular tidal interaction with the pulsar. Then, we turned on the pulsar wind and the Be wind. We ran two simulations with different wind mass-loss rates for the Be star, one for a B2 V type and the other for a significantly earlier spectral type. Although the global shape of the interaction surface between the pulsar wind and the Be wind agrees with the analytical solution, the effect of the pulsar wind on the Be disk is profound. The pulsar wind strips off an outer part of the Be disk, truncating the disk at a radius significantly smaller than the pulsar orbit. Our results, therefore, rule out the idea that the pulsar passes through the Be disk around periastron, which has been assumed in previous studies. It also turns out that the location of the contact discontinuity can be significantly different between phases when the pulsar wind directly hits the Be disk and those when the pulsar wind collides with the Be wind. It is thus important to adequately take into account the circumstellar environment of the Be star, in order to construct a satisfactory model for this prototypical TeV binary.
Widely Extended [O III] 88μm Line Emission around the 30 Doradus Region Revealed with AKARI FIS-FTS
Authors: Kawada Mitsunobu , Takahashi Ai , Yasuda Akiko , Kiriyama Yuichi , Mori Tatsuya , Mouri Akio , Kaneda Hidehiro , Okada Yoko , Takahashi Hidenori , Murakami Noriko
Published: March 2014

We present a distribution map of the far-infrared [O III] 88 $\mu$m line emission around the 30 Doradus (30 Dor) region in the Large Magellanic Cloud obtained with the Fourier Transform Spectrometer of the Far-Infrared Surveyor on board AKARI. The map reveals that the [O III] emission is widely distributed by more than 10$'$ around the super star cluster R 136, implying that the 30 Dor region is affluent with interstellar radiation field that is hard enough to ionize O$^{2+}$. The observed [O III] line intensities are as high as (1–2) $\times$ 10$^{-6}$ W m$^{-2}$ sr$^{-1}$ on the peripheral regions 4$'$–5$'$ away from the center of 30 Dor, which requires gas densities of 60–100 cm$^{-3}$. However, the observed size of the distribution of the [O III] emission is too large to be explained by massive stars in the 30 Dor region enshrouded by clouds with a constant gas density of 10$^{2}$ cm$^{-3}$. Therefore, the surrounding structure is likely to be highly clumpy. We also find a global correlation between the [O III] and the far-infrared continuum emission, suggesting that the gas and dust are well mixed in the highly ionized region where the dust survives in clumpy dense clouds shielded from energetic photons.
The Effect of Metallicity on the Delay-Time Distribution of Type Ia Supernova
Authors: Meng Xiang Cun , Li Zhong Mu , Yang Wu Ming
Published: March 2014

Measuring the delay-time distribution (DTD) of type Ia supernova (SNe Ia) is an important way to constrain the progenitor nature of SNe Ia. Recently, Strolger et al. (2010, ApJ, 713, 32, hereafter SDR10) obtained a very delayed DTD, which is much different from other measurements. They suggested that metallicity could be the origin of their delayed DTD. In this paper, we show the effect of metallicity on the DTD of SNe Ia from single-degenerate models (including WD $+$ MS and WD $+$ RG channels). Via a binary population synthesis approach, we find that the DTD from a low-metallicity population is significantly delayed compared with that from a high-metallicity one. In addition, we also find that a substantial fraction of SNe Ia have a delay time shorter than 1 Gyr, and the fraction of SNe Ia with short delay times increases with the metallicity, i.e., about 35% for $Z$  $=$ 0.001, while more than 70% for $Z$  $=$ 0.02. These results would help to qualitatively explain the result of SDR10. Furthermore, we noticed that the contribution of the WD $+$ RG channel from the low-metallicity population is higher than that from the high-metallicity one. However, we could not quantitatively obtain a DTD consistent with the results of SDR10 by changing the metallicity. As a consequence, metallicity may partly contribute to the DTD of SNe Ia, and should therefore be carefully checked when one derives the DTD of SNe Ia from observations.
Statistical Study on the Nature of Solar-Flux Emergence
Authors: Otsuji Kenichi , Kitai Reizaburo , Ichimoto Kiyoshi , Shibata Kazunari
Published: March 2014

We studied 101 flux emergence events ranging from small ephemeral regions to large emerging flux regions that were observed with the Hinode Solar Optical Telescope filtergram. We investigated how the total magnetic flux of the emergence event controls the nature of emergence. To determine the modes of emergences, horizontal velocity fields of the global motion of the magnetic patches in the flux emerging sites were measured by local correlation tracking. Between two main polarities of the large emerging flux regions with more than around 2 $\times$ 10$^{19}$ Mx, there were converging flows of anti-polarity magnetic patches. On the other hand, small ephemeral regions showed no converging flow, but a simple diverging pattern. When we looked into the detailed features in the emerging sites, irrespective of the total flux and the spatial size, all of the emergence events were observed to consist of single or multiple elementary emergence unit(s). The typical size of unitary emergence is 4 Mm, and consistent with simulation results. From a statistical study of the flux emergence events, the maximum spatial distance between two main polarities, the magnetic flux growth rate and the mean separation speed were found to follow the power-law functions of the total magnetic flux with indices of 0.27, 0.57, and $-$0.16, respectively. From a discussion on the observed power-law relations, we obtained a physical view of solar flux emergence, in which the emerging magnetic fields float and evolve while balancing to the surrounding turbulent atmosphere.
Study of Eclipsing Binary and Multiple Systems in OB Associations. I. Orion OB1a- IM Monocerotis
Authors: Bakis Hicran , Bakis Volkan , Bilir Selçuk , MikulÁšEK Zdenek , Zejda Miloslav , Yaz Esma , Demircan Osman , Bulut Ibrahim
Published: March 2014

All available photometric and spectroscopic observations were collected and used as the basis of a detailed analysis of the close binary IM Mon. The orbital period of the binary was refined to 1$.\!\!\!^{\rm d}$19024249 (0.00000014). The Roche equipotentials, fractional luminosities (in $B$, $V$, and Hp-bands) and fractional radii for the component stars in addition to the mass ratio, $q$, inclination, $i$, of the orbit, and the effective temperature, $T_{\rm eff}$, of the secondary cooler less massive component were obtained by the analysis of light curves. IM Mon is classified to be a detached binary system in contrast to the contact configuration estimations in the literature. The absolute parameters of IM Mon were derived by the simultaneous solutions of light and radial-velocity curves as $M_{1,2}$$=$ 5.50 (0.24)$\ M_{\odot}$ and 3.32 (0.16)$\ M_{\odot}$, $R_{1,2}$$=$ 3.15 (0.04)$\ R_{\odot}$ and 2.36 (0.03)$\ R_{\odot}$, $T_{{\rm eff} 1,2}$$=$ 17500 (350) K and 14500 (550) K implying spectral types of B4 and B6.5 ZAMS stars for the primary and secondary components, respectively. The modelling of the high-resolution spectrum revealed the rotational velocities of the component stars as $V_{{\rm rot}1}$$=$ 147 (15) km s$^{-1}$ and $V_{{\rm rot}2}$$=$ 90 (25) km s$^{-1}$. The photometric distance of 353 (59) pc was found to be more precise and reliable than the Hipparcos distance of 341 (85) pc. An evolutionary age of 11.5 (1.5) Myr was obtained for IM Mon. Kinematical and dynamical analyses support the membership of the young thin-disk population system IM Mon to the Ori OB1a association dynamically. Finally, we derived the distance, age, and metallicity information of Ori OB1a sub-group using information of the IM Mon parameters.
An Overview of JAXA's Ground-Observation Activities for HAYABUSA Reentry
Authors: Fujita Kazuhisa , Yamamoto Masa-yuki , Abe Shinsuke , Ishihara Yoshiaki , Iiyama Ohmi , Kakinami Yoshihiro , Hiramatsu Yoshihiro , Furumoto Muneyoshi , Takayanagi Hiroki , Suzuki Toshiyuki , Yanagisawa Toshifumi , Kurosaki Hirohisa , Shoemaker Michael , Ueda Masayoshi , Shiba Yasuo , Suzuki Masaharu
Published: March 2014

On 2010 June 13, the HAYABUSA asteroid explorer returned to Earth and underwent a super-orbital atmospheric reentry. In order to recover the sample return capsule and to take ground-based measurements, the Japan Aerospace Exploration Agency organized a ground-observation team and performed optical tracking of the capsule, spectroscopy of the fireball, and measurements of infrasounds and shock waves generated by the fireball. In this article, an overview of the ground-based observation is presented, and an outline of the preliminary results derived from observations is reported.
Entry Dispersion Analysis for the HAYABUSA Spacecraft using Ground-Based Optical Observation
Authors: Yamaguchi Tomohiro , Yoshikawa Makoto , Yagi Masafumi , Tholen David J.
Published: March 2014

The HAYABUSA asteroid explorer successfully released its sample capsule to Australia on 2010 June 13. Since the Earth reentry phase of sample return was critical, many backup plans for predicting the landing location were prepared. This paper considers the reentry dispersion using ground-based optical observation as a backup observation for radiometric observation. Several scenarios were calculated and compared for the reentry phase of HAYABUSA to evaluate the navigation accuracy of the ground-based observation. The optical observation doesn't require any active reaction from a spacecraft, and thus these results show that optical observations could be a steady backup strategy even if a spacecraft had some trouble. We also evaluated the landing dispersion of HAYABUSA only with optical observation.
Chaotic Oscillation of a One-Zone Model for Coupled Convection and Pulsation
Authors: Tanaka Yasuo
Published: March 2014

A system of nonlinear equations of Stellingwerf's one-zone model coupled pulsation and convection has been studied concerning the dependence on the depth of the convective zone. It has been shown that the system has one fixed point for the case of a shallow convective zone, and two for the case of rather deep convection, except at the origin. The numerical solutions for the cases of two fixed points show some chaotic oscillations, such as period doubling, period 6, period 3, and so on. The solutions of long-period and large oscillation width were also obtained. It is suggested that these results are helpful for interpretating the observational data of semi-regular and Mira variables. Further theoretical problems are also discussed.
Infrared Spectral Energy Distribution of Galaxies in the AKARI All Sky Survey: Correlations with Galaxy Properties, and Their Physical Origin
Authors: Totani Tomonori , Takeuchi Tsutomu T. , Nagashima Masahiro , Kobayashi Masakazu A. R. , Makiya Ryu
Published: March 2014

We have studied the properties of more than 1600 low-redshift galaxies by utilizing high-quality infrared flux measurements of the AKARI All-Sky Survey and physical quantities based on optical and 21-cm observations. Our goal is to understand the physics determining the infrared spectral energy distribution (SED). The ratio of the total infrared luminosity, $L_{\rm TIR}$, to the star-formation rate (SFR) is tightly correlated by a power-law to specific SFR (SSFR), and $L_{\rm TIR}$ is a good SFR indicator only for galaxies with the largest SSFR. We discovered a tight linear correlation for normal galaxies between the radiation field strength of dust heating, estimated by infrared SED fits ($U_h$), and that of galactic-scale infrared emission ($U_{\rm TIR} \propto L_{\rm TIR}/R^2$), where $R$ is the optical size of a galaxy. The dispersion of $U_h$ along this relation is $\sim $0.3 dex, corresponding to $\sim $13% dispersion in the dust temperature. This scaling and the $U_h/U_{\rm TIR}$ ratio can be explained physically by a thin layer of heating sources embedded in a thicker, optically-thick dust screen. The data also indicate that the heated fraction of the total dust mass is anti-correlated to the dust column density, supporting this interpretation. In the large $U_{\rm TIR}$ limit, the data of circumnuclear starbursts indicate the existence of an upper limit on $U_h$, corresponding to the maximum SFR per gas mass of $\sim $10 Gyr$^{-1}$. We find that the number of galaxies sharply drops when they become optically thin against dust-heating radiation, suggesting that a feedback process to galaxy formation (likely by the photoelectric heating) is working when dust-heating radiation is not self-shielded on a galactic scale. Implications are discussed for the $M_{{\rm H{ I}}}$-size relation, the Kennicutt-Schmidt relation, and galaxy formation in the cosmological context.
H2O Maser Motions and the Distance of the Star-Forming Region G 192.16−3.84
Authors: Shiozaki Satoshi , Imai Hiroshi , Tafoya Daniel , Omodaka Toshihiro , Hirota Tomoya , Honma Mareki , Matsui Makoto , Ueno Yuji
Published: March 2014

We present the results of astrometic observations of H$_{2}$O masers associated with the star-forming region G 192.16$-$3.84 with the VLBI Exploration of Radio Astrometry (VERA). The H$_{2}$O masers seem to be associated with two young stellar objects (YSOs) separated by $\sim\ $1200 AU, as reported in previous observations. In the present observations, we successfully detected an annual parallax of $\pi$$=$ 0.66$\ \pm\ $0.04 mas for the H$_{2}$O masers, which corresponds to a distance to G 192.16$-$3.84 of $D$$=$ 1.52$\ \pm\ $0.08 kpc from the Sun. The determined distance is shorter than the estimated kinematic distance. Using the annual parallax and the estimated parameters of the millimeter continuum emission, we estimate the mass of the disk plus circumstellar cloud in the southern YSO to be 10.0$^{+4.3}_{-3.6}\ M_{\odot}$. We also estimate the galactocentric distance and the peculiar motion of G 192.16$-$3.84, relative to a circular galactic rotation, to be $R_{\ast}$$=$ 9.99$\ \pm\ $0.08 kpc and $Z_{\ast}$$=$$-$0.10$\ \pm\ $0.01 kpc, and ($U_{\ast}$, $V_{\ast}$, $W_{\ast}$) $=$ ($-$2.8$\ \pm\ $1.0, $-$10.5$\ \pm\ $0.3, 4.9$\ \pm\ $2.7) [km s$^{-1}$], respectively. The peculiar motion of G 192.16$-$3.84 is not beyond the range of recent VLBI astrometric results. The angular distribution and three-dimensional velocity field of H$_{2}$O maser features indicate the existence of a bipolar outflow with a major axis along the northeast–southwest direction.
Design and Development of a High-Speed Data-Acquisition System for the Korean VLBI Network
Authors: Oh Se-Jin , Roh Duk-Gyoo , Wajima Kiyoaki , Kawaguchi Noriyuki , Byun Do-Young , Yeom Jae-Hwan , Je Do-Heung , Han Seog-Tae , Iguchi Satoru , Kawakami Kazuyuki , Ozeki Kensuke , Kobayashi Hideyuki , Sasao Tetsuo , Sohn BongWon , Kim JaeHeon , Miyazaki Atsushi , Oyama Tomoaki , Kurayama Tomoharu
Published: March 2014

A new high-speed Data Acquisition System (DAS) has been developed for the millimeter-wave VLBI array newly constructed in Korea, the Korean VLBI Network (KVN). The KVN DAS is specially designed to support the most distinctive feature of the KVN, that is simultaneous reception of multiple frequency bands (22, 43, 86 and 129-GHz bands in the current KVN system) for realizing multi-frequency phase referencing, which is the key technology for successful millimeter-wave VLBI observations toward active galactic nuclei and astronomical maser sources. Although the basic functions of the KVN DAS succeed technological elements originally developed in the VERA (VLBI Exploration of Radio Astrometry) Project, essentially new designs have been introduced for the simultaneous processing of four data streams in the optical data-transmission system, the digital filter, and the digital spectrometer. The KVN DAS system consists of four Gigabit Samplers (GBS), Optical Transmission System (OTS), Digital Filter Bank (DFB), Digital Spectrometer (DSM), and the data recorder. The DFB realizes very flexible and phase-stable channelization of up to four data streams. The DSM facilitates quick look of power and cross-power spectra of observed data. The VLBI output data from the DFB are recorded to the Mark5B recorder with a maximum rate of 1-Gbps. We discuss in the present paper the primary specifications, designs, and experimental results of the KVN DAS system.
Do Meteoroids Originating from Near-Earth Asteroid (25143) Itokawa Exist?
Authors: Ohtsuka Katsuhito , Abe Shinsuke , Ito Takashi , Nakamura Tomoki , Abe Masanao , Yano Hajime , Watanabe Jun-ichi
Published: March 2014

Making a survey of Itokawids, i.e., meteor(oid)s originating from Apollo-type near-Earth Asteroid (25143) Itokawa, from among the multiple-station optical meteor orbit data, and employing several orbital similarity criteria, we found five Itokawid candidates. Furthermore, we classified the Itokawid candidates in meteorite types according to their physical data. The physical analyses indicate that all of the candidates evidently belong to not cometary, but asteroidal, meteoroids. Especially, the fireball, MORP 172, is the one candidate that is classified among ordinary/carbonaceous chondrites, as against the four other at carbonaceous chondrites. Hence, the classified meteoritic matter of MORP 172 shows more similarities to Itokawa's surface composition of an LL chondrite analogue than those of the other candidates. Therefore, the fireball is considered to be the strongest of the Itokawid candidates.
Enhancement of Terrestrial Diffuse X-Ray Emission Associated with Coronal Mass Ejection and Geomagnetic Storm
Authors: Ezoe Yuichiro , Miyoshi Yoshizumi , Yoshitake Hiroshi , Mitsuda Kazuhisa , Terada Naoki , Oishi Shihoko , Ohashi Takaya
Published: March 2014

We present an analysis of a Suzaku observations taken during the geomagnetic storm of 2005 August 23–24. We found a time variation of diffuse soft X-ray emission when a coronal mass ejection hit Earth and caused a geomagnetic storm. The diffuse emission consisted of fluorescent scattering of solar X-rays and an exospheric solar wind charge exchange. The former is characterized by a neutral oxygen emission line due to strong heating of the upper atmosphere during the storm time, while the latter is dominated by the sum of C V, C VI, N VI, N VII, O VII, and O VIII emission lines due to an enhanced solar wind flux in the vicinity of the exosphere. Using the solar-wind data taken with the ACE and WIND satellites, a time correlation between the solar wind and the strong O VII line flux was investigated. We estimated necessary column densities for the solar X-ray scattering and exospheric SWCX. From these results, we argue that a part of the solar-wind ions enters inside the magnetosphere and causes the SWCX reaction.
X-Ray Observation of Mars at Solar Minimum with Suzaku
Authors: Ishikawa Kumi , Ezoe Yuichiro , Ohashi Takaya , Terada Naoki , Futaana Yoshifumi
Published: March 2014

Mars was observed in X-rays during 2008 April 3–5 for 82 ks with the Japanese Suzaku observatory. Mars has been known to emit X-rays via the scattering of solar X-rays and via charge exchange between neutral atoms in the exosphere and solar-wind ions. Past theoretical studies suggest that the exospheric neutral density may vary by a factor of up to 10 over the solar cycle. To investigate a potential change of the exospheric charge exchange emission, Mars was observed with Suzaku at solar minimum. Significant signals were not detected at the position of Mars in the energy band of 0.2–5 keV. The 2 $\sigma$ upper limit of the O II line flux in 0.5–0.65 keV was 4.3 $\times$ 10 $^{-5}$ photons cm $^{-2}$ s $^{-1}$ . Comparing this upper limit to past Chandra and XMM-Newton observations conducted near solar maximum, it was found that the exospheric density at solar minimum does not exceed that near solar maximum by more than 6–70 times.