bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of a Long-Extended Dust Trail Associated with Short-Period Comet 4P/Faye in 2006 Return
Authors: Sarugaku Yuki , Ishiguro Masateru , Pyo Jeonghyun , Miura Naoya , Nakada Yoshikazu , Usui Fumihiko , Ueno Munetaka
Published: March 2014

The longest dust trail among those so detected at optical wavelengths was found along the orbit of 4P/Faye in the 2006 return. It extended as long as 10° in the backward direction. The surface brightness increases monotonically with the distance from the nucleus between $0\rlap{.}^\circ5$ and 3°, but decreases slowly beyond 4°. The observed brightnesses of the dust trail and the tail are reasonably explained by our dust ejection model. The model shows that the dust trail is composed of cm-sized particles ejected during previous returns, and the derived power indices of the size distribution function of dust particles ejected from the nucleus ($-$3.5) and those remaining in the trail ($-$1.9) have a big difference for each other. The averaged mass-loss rate (20 kg s$^{-1}$) derived from the model is comparable to those of known IRAS dust trail comets.
Polarimetric Imager for Comets, PICO
Authors: Ikeda Yuji , Kawakita Hideyo , Furusho Reiko , Sato Yusuke , Kasuga Toshihiro
Published: March 2014

We constructed an imaging polarimeter, PICO, that was optimized for comets and/or cometary objects. PICO has a field-of-view of 5$' \times$ 10$'$ and employs a fixed Wollaston prism as an analyzer. In the case of polarimeters using a double-beam prism, such as a Wollaston prism, lateral chromatic aberrations originating from the prism often degrade the image quality and measurement accuracy. However, PICO suffers little lateral chromatic aberration due to compensation provided by newly designed lens systems that generate opposite lateral colors. Owing to this design, PICO can obtain highly resolved and very accurate polarization images throughout the FOV (field-of-view). The total accuracy is estimated to be $\Delta P \simeq [(P/8{5})^2 + 0.3^2]^{1/2}\;$% in polarization degree and $\theta \leq$ 3$^{\circ}$ in position angle; these values are satisfactory for cometary studies.
Two-Dimensional Radiation-Hydrodynamic Model for Supercritical Disk Accretion Flows onto Neutron Stars
Authors: Ohsuga Ken
Published: March 2014

We performed two-dimensional radiation hydrodynamic simulations of supercritical accretion flows around neutron stars (NSs). In contrast with accretion flows onto black holes (BHs), we find that shell-shaped high-density regions form around the NSs, since the radiation force is enhanced in the innermost regions. The enhanced radiation force drives strong outflows above and below the disk. The mass-accretion rate onto the NS exceeds the critical rate, $L_{\rm E}/c^2$, with $L_{\rm E}$ being the Eddington luminosity. However it is about 20–30% of that onto the BH, under the condition that we employ the same mass-input rate, $\dot{M}_{\rm input}$, which is the mass injected from the outer disk boundary per unit time. The mass-outflow rate is a few-times larger in flows around NSs than in flows around BHs. The supercritical NS accretion flows mainly release the accretion energy as kinetic energy of the outflows, though the disk luminosity is predominant over the kinetic energy output rate in the BH accretion flows. The resulting velocity and mass-outflow rate of the outflows are 0.2–0.3$c$ and 150–700$L_{\rm E}/c^2$, respectively, for a mass-input rate of $3 \times 10^2\lesssim \dot{M}_{\rm input} /(L_{\rm E}/c^2)\lesssim 3\times 10^3$. This implies that the SS 433 jets can be roughly explained by supercritical accretion onto a NS. However, the collimation angle of the outflows in our simulations ($\sim 20^\circ$) is larger than that of the SS 433 jets (a few degrees).
Observational Appearance of Relativistic, Spherically Symmetric Massive Winds
Authors: Sumitomo Naoko , Nishiyama Shinji , Akizuki Chizuru , Watarai Ken-ya , Fukue Jun
Published: March 2014

The photon mean free path in a relativistically moving medium becomes long in the downstream direction, while short in the upstream direction. As a result, the observed optical depth, $\tau$, becomes small in the downstream direction while large in the upstream direction. Hence, if a relativistic spherical wind blows off, the optical depth depends strongly on its speed and the angle between the velocity and the line-of-sight. Abramowicz, Novikov, and Paczynski (1991, ApJ, 369, 175) examined such a relativistic wind, and found that the shape of the photosphere at $\tau=1$ appears to be convex in the nonrelativistic case, but concave for relativistic velocities. We further calculated the temperature distribution and luminosity of the photosphere both in the comoving and inertial frames. We found that the limb-darkening effect would be strongly modified in the relativistic regime. We also found that the luminosities of the photosphere become large as the wind speed increases due to relativistic effects. In addition, the luminosity in the inertial frame is higher than that in the comoving frame. These results suggest that the observed temperature and brightness in luminous objects may be overestimated when there are strong relativistic winds.
Evidence of Hot Spot Activity on BH Virginis
Authors: Xiang Fuyuan , Tao Xia , Tian Yongpo
Published: March 2014

Photoelectric light curves of BH Vir in the UBVRI bands observed by Arévalo et al. in 1986 were analyzed by using the latest version of the Wilson–Devinney program and to investigate the photometric parameters and spot activity. Satisfactory fits were obtained by assuming a hot spot only on the secondary star. The results show that the temperature of the spotted region relative to the photosphere, $T_{\rm s}/T_{\rm ph}$, is 1.13$\pm$0.027. The active region tends to occur at low latitude (near 81$^{\circ}$). The results also show that the mass ratio obtained from the photoelectric light curves is $q=m_{2}/m_{1} =$ 0.971. It is close to the spectroscopic value of 0.968 obtained by Zhai et al. (1990). The photosphere temperature of the primary is $T_{1}=$ 5969$\pm$11 K. After checking of the activity pattern from 1953 to 1991, the activity cycle is estimated to be about 10 yr.
Low-Dimensional Chaos of High-Latitude Solar Activity
Authors: Li Qi-Xiu , Li Ke-Jun
Published: March 2014

The chaos of high-latitude solar activity has been investigated by determining the behavior of the monthly averaged polar facula counts obtained from the National Astronomical Observatory of Japan (NAOJ) on the basis of nonlinear dynamics theories and methods. It is found that the high-latitude solar activity is also governed by a low-dimensional chaotic attractor in both the northern and southern solar hemispheres, which is the same as that of the low-latitude solar activity. However, their maximal Lyapunov exponents are different, showing different strength of chaos. The maximal Lyapunov exponent (MLE) of polar faculae in the southern solar hemisphere is about 0.0211$\pm$0.0003 (month$^{-1})$, which is nearly consistent with the low-latitude Wolf sunspot numbers, while the MLE in the northern one is approximately 0.0944$\pm$0.0066 (month$^{-1}$), which is obviously greater than the above two.
MOIRCS Deep Survey. II. Clustering Properties of $K$-Band Selected Galaxies in GOODS-North Region
Authors: Ichikawa Takashi , Suzuki Ryuji , Tokoku Chihiro , Uchimoto Yuka Katsuno , Konishi Masahiro , Yoshikawa Tomohiro , Kajisawa Masaru , Ouchi Masami , Hamana Takashi , Akiyama Masayuki , Nishimura Tetsuo , Omata Koji , Tanaka Ichi , Yamada Toru
Published: March 2014

We present the first measurement of clustering properties of low-mass galaxies with a stellar mass down to $M_*\sim 10^9 M_{\odot}$ at 1$\lt z \lt $4 in 24.4 arcmin$^{2}$ of the GOODS-North region with a depth of $K_\mathrm{AB}\sim$25. Luminous galaxies in the $K$-band have a larger correlation length than faint galaxies. For color-selected samples at 2$\lt z \lt$4, distant red galaxies with $J-K \gt$1.3 show a large bias of $b\sim$7.2$\pm$1.3 on scales of up to $\theta\sim$100$^{\prime\prime}$ or 3.1 comoving Mpc, while blue galaxies with 0.5$\lt J-K \lt $1.3 have a weak clustering signal on large scales, but a possible strong small-scale excess at $\theta \lt $10$^{\prime\prime}$. For massive galaxies with $M_*\gtrsim 10^{10}M_{\odot}$, we estimate the correlation length and bias to be $r_0\sim$4.5$h^{-1}$Mpc and $b=$1.9–3.5, which are much larger than those of low-mass ($M_*\sim$10$^9-10^{10}M_{\odot}$) galaxies. The comparison of our measurements with analytic CDM models constrains the properties of hosting dark halos, and indicates that the low-mass galaxies would be progenitors of galaxies with a typical luminosity of $L\lesssim L_*$ in the local Universe. The blue galaxies in low-mass samples are more strongly clustered in more massive halos with higher occupation numbers than low-mass red galaxies. This fact suggests an environment effect due to the halo mass on the star-formation activity at high-$z$.
An Orbital Period Investigation of the W UMa-Type Binary Y Sextantis
Authors: He Jia-Jia , Qian Sheng-Bang
Published: March 2014

Four charge-coupled device (CCD) photometric times of light minimum of the overcontact binary Y Sex obtained from 2004 to 2007 are presented. It has been discovered that the light curve of Y Sex is variational. Combining the present times of light minimum with values collected from the literature, we investigated the orbital period changes of the system. It has been found that there may exist two cyclic period oscillations in the $O-C$ diagram of Y Sex. One oscillates at a period of 51.22 yr with an amplitude of 0.0218 d, and the other changes at a period of 32.10 yr with an amplitude of 0.0100 d. The period oscillations can be explained either by the light-time effect via the presence of an unseen third body and an unseen fourth body or by magnetic-activity cycles of the components.
Survey for a Small Asteroid Population in the Cosmic Evolution Survey Field
Authors: Terai Tsuyoshi , Itoh Yoichi , Mukai Tadashi
Published: March 2014

We searched for small main-belt asteroids in the Cosmic Evolution Survey (COSMOS) field using the Subaru Prime Focus Camera (Suprime-Cam). The ecliptic latitude of the region is about $-$10$^{\circ}$. Using a method we developed to detect moving objects from two images, we detected 202 moving objects with a limiting magnitude of $i^{\prime} =$ 23.8 mag in 1.7 deg$^2$. Most of them are sub-km asteroid candidates. The number density is 122 deg$^{-2}$, less than half of that in the ecliptic. The slope of the cumulative size distribution is 1.30$\pm$0.05 for asteroids with a diameter of 0.5–2 km, consistent with that of sub-km asteroids in the ecliptic derived from a previous survey.
Instability of Population III Black Hole Accretion Disks
Authors: Ohsuga Ken , Susa Hajime , Uchiyama Yosuke
Published: March 2014

We investigated the stability of black hole accretion disks in a primordial environment (POP III disks for short), by solving the vertical structure of optically thick disks, including convective energy transport, and by employing a one-zone model for optically thin isothermal disks. Because of the absence of metals in POP III disks, we find significant differences in stability associated with ionization between POP III disks and the disks of solar metallicity. An unstable branch in S-shaped equilibrium curves on the $\dot{M}$–$\Sigma$ (mass accretion rate–surface density) plane extends to a larger surface density compared with the case of disks of solar metallicity. The resulting equilibrium loci indicate that quasi-periodic oscillations in luminosity can also be driven in POP III disks, and their maximal luminosity is typically by an order of magnitude larger than that of the disks of solar metallicity. Such a strong outburst of POP III disks can be observed by future huge telescopes, in the case that the mass is supplied onto the disks at the Bondi accretion rates in typical virialized small dark halos.
A Possible Structure of the Magnetic Field in Solar Filaments Obtained by Flux Emergence
Authors: Magara Tetsuya
Published: March 2014

We report a result, that the emergence of a subsurface magnetic field naturally reproduces the feature of the global magnetic configuration observed in solar filaments. This was obtained by performing a three-dimensional simulation of a twisted flux tube that emerges in the shape of a multi-$\Omega$-loop in a highly stratified solar atmosphere, extending from the subsurface layer to the corona. One of the key findings is that a kinking of the twisted flux tube occurs at the site of a linkage between adjacent $\Omega$-loops. This develops a magnetic structure that has remarkable similarities to the structure of a filament, in that the inner part of the twisted flux tube can be applied to the main body of a filament, while the outer part is reminiscent of observations of filament feet and a coronal arcade overlying the main body of a filament. Based on the result, we concluded that the orientation of filaments observed on the Sun may have its origin in the handedness of a twisted magnetic field below the solar surface.
Evidence for Solar-Wind Charge-Exchange X-Ray Emission from the Earth’s Magnetosheath
Authors: Fujimoto Ryuichi , Mitsuda Kazuhisa , McCammon Dan , Takei Yoh , Bauer Michael , Ishisaki Yoshitaka , Porter F. Scott , Yamaguchi Hiroya , Hayashida Kiyoshi , Yamasaki Noriko Y.
Published: March 2014

We report an apparent detection of the C VI 4p to 1s transition line at 459 eV, during a long-term enhancement (LTE) in the Suzaku north ecliptic pole observation of 2005 September 2. The observed line intensity is comparable to that of the C VI 2p to 1s line at 367 eV. This is strong evidence for the charge-exchange process. In addition, O VII, O VIII, Ne X, and Mg XI lines showed clear enhancements. There are also features in the 750–900–eV range that could be due to some combination of Fe L lines, higher order transitions of O VIII (3p to 1s and 6p to 1s), and a Ne IX line. From the correlation of the X-ray intensity with the solar-wind flux on time scales of about half a day, and from the short-term ($\sim 10 \,\mathrm{minutes}$) variations of the X-ray intensity, these lines most likely arise from solar-wind heavy ions interacting with neutral material in the Earth’s magnetosheath. A hard power-law component is also necessary to explain the LTE spectrum. Its origin is not yet known. Our results indicate that solar activity can significantly contaminate Suzaku cosmic X-ray spectra below $\sim 1 \,\mathrm{keV}$. Recommendations are provided for recognizing such contamination in observations of extended sources.
X-Ray Spectral Study of the Extended Emission, ‘the Cap’, Located 11.6 kpc above the Disk of M82
Authors: Tsuru Takeshi Go , Ozawa Midori , Hyodo Yoshiaki , Matsumoto Hironori , Koyama Katsuji , Awaki Hisamitsu , Fujimoto Ryuichi , Griffiths Richard , Kilbourne Caroline , Matsushita Kyoko , Mitsuda Kazuhisa , Ptak Andrew , Ranalli Piero , Yamasaki Noriko Y.
Published: March 2014

The extended X-ray emission from ‘the Cap’ region, located $11{}^{\prime }$ (11.6 kpc) above the disk of the starburst galaxy M82, has been observed with Suzaku and XMM-Newton. Owing to the good energy resolution and the large collecting area of the XIS on Suzaku, combined with similar properties of the EPIC instrument on XMM-Newton, we have clearly detected K-shell emission lines from O VII, O VIII, Ne X, Mg XI, Mg XII, Sr XIII, and the Fe L complex. Two optically thin thermal plasma components are required to fit the observed X-ray spectra. We have determined the metal abundances of O, Ne, Mg, Si, and Fe in this region for the first time. Their metal abundance ratios agree well with those of metal-poor stars and the model prediction of metals synthesized by type-II supernovae, but they are not consistent with the metallicities of type-Ia supernovae. This result is support for the idea that the origin of the metals in the Cap is type-II supernova explosions occurring in the starburst regions in the M82 galaxy. We discuss the possible contribution from sputtered dust grains to the metals in the Cap. An emission line consistent with the C VI transition of $n=4$ to 1 at 0.459 keV has been marginally detected, although it is not statistically significant at the 99% confidence level; the presence of this line would suggest charge-exchange processes in the Cap.
Revealing the High Energy Emission from the Obscured Seyfert Galaxy MCG−5–23–16 with Suzaku
Authors: Reeves James N. , Awaki Hisamitsu , Dewangan Gulab C. , Fabian Andy C. , Fukazawa Yasushi , Gallo Luigi , Griffiths Richard , Inoue Hajime , Kunieda Hideyo , Markowitz Alex , Miniutti Giovanni , Mizuno Tsunefumi , Mushotzky Richard , Okajima Takashi , Ptak Andy , Takahashi Tadayuki , Terashima Yuichi , Ushio Masayoshi , Watanabe Shin , Yamasaki Tomonori , Yamauchi Makoto , Yaqoob Tahir
Published: March 2014

We report on a 100 ks Suzaku observation of the bright, nearby ($z=0.008486$) Seyfert 1.9 galaxy MCG $-$5–23–16. The broad-band (0.4–100 keV) X-ray spectrum allows us to determine the nature of the high energy emission with little ambiguity. The X-ray continuum consists of a cutoff power-law of photon index $\Gamma=1.9$, absorbed through Compton-thin matter of column density $N_{\mathrm{H}} = 1.6 \times 10^{22} \,\mathrm{cm}^{-2}$. A soft excess is observed below 1 keV and is likely a combination of emission from scattered continuum photons and distant photoionized gas. The iron K line profile is complex, showing narrow neutral iron $\mathrm{K}\alpha$ and $\mathrm{K}\beta$ emission, as well as a broad line which can be modeled by a moderately inclined accretion disk. The line profile shows either the disk is truncated at a few tens of gravitational radii, or the disk emissivity profile is relatively flat. A strong Compton reflection component is detected above 10 keV, which is best modeled by a combination of reflection off distant matter and the accretion disk. The reflection component does not appear to vary. The overall picture is that this Seyfert 1.9 galaxy is viewed at moderate ($\sim 50^\circ$) inclination through Compton-thin matter at the edge of a Compton-thick torus covering $\sim 2\pi$ steradians, consistent with unified models.
Near-Infrared and Mid-Infrared Spectroscopy with the Infrared Camera (IRC) for AKARI
Authors: Ohyama Youichi , Onaka Takashi , Matsuhara Hideo , Wada Takehiko , Kim Woojung , Fujishiro Naofumi , Uemizu Kazunori , Sakon Itsuki , Cohen Martin , Ishigaki Miho , Ishihara Daisuke , Ita Yoshifusa , Kataza Hirokazu , Matsumoto Toshio , Murakami Hiroshi , Oyabu Shinki , TanabÉ Toshihiko , Takagi Toshinobu , Ueno Munetaka , Usui Fumio , Watarai Hidenori , Pearson Chris P. , Takeyama Norihide , Yamamuro Tomoyasu , Ikeda Yuji
Published: March 2014

The Infrared Camera (IRC) is one of the two instruments on board the AKARI satellite, In addition to deep imaging from 1.8 to 26.5 $\mu$m for the pointed observation mode of the AKARI, it has a spectroscopic capability in its spectral range. By replacing the imaging filters by transmission-type dispersers on the filter wheels, it provides low-resolution ($\lambda$/$\delta \lambda \sim$ 20–120) spectroscopy with slits, or in a wide imaging field-of-view (approximately 10$\;\times\;$10). The IRC spectroscopic mode is unique for space infrared missions in that it has the capability to perform sensitive wide-field spectroscopic surveys in the near-and mid-infrared wavelength ranges. This paper describes the specifications of the IRC spectrograph and its in-orbit performance.
In-Orbit Focal Adjustment of the AKARI Telescope with Infrared Camera (IRC) Images
Authors: Kaneda Hidehiro , Kim Woojung , Onaka Takashi , Wada Takehiko , Ita Yoshifusa , Sakon Itsuki , Takagi Toshinobu
Published: March 2014

AKARI, currently in space, carries onboard a cryogenically cooled light-weight telescope with silicon carbide mirrors. The wavefront error of the AKARI telescope, obtained in laboratory measurements at 9 K, showed that the expected in-orbit imaging performance was diffraction-limited at a wavelength of 6.2 $\mu$m. The AKARI telescope has a function of focus adjustment by shifting the secondary mirror in parallel to the optical axis. On the 4th day after jettison of the cryostat aperture lid in orbit, we observed a star with the Infrared Camera (IRC) onboard AKARI. Since the initial star images observed in the near-infrared (NIR) bands were significantly blurred, we twice moved the secondary mirror for a focal adjustment based on the results of model analyses as well as data analyses of NIR band images. As a consequence, we successfully adjusted the focus of the telescope. The thus-obtained in-orbit imaging performance for the AKARI telescope is diffraction-limited at a wavelength of 7.3 $\mu$m, slightly degraded from that expected from laboratory measurements.
Infrared Camera (IRC) Deep Survey in the Performance-Verification Phase
Authors: Wada Takehiko , Oyabu Shinki , Ita Yoshifusa , Matsuhara Hideo , Pearson Chris P. , Onaka Takashi , Ohyama Youichi , Usui Fumihiko , Fujishiro Naofumi , Ishihara Daisuke , Kataza Hirokazu , Kim Woojung , Matsumoto Toshio , Murakami Hiroshi , Sakon Itsuki , TanabÉ Toshihiko , Takagi Toshinobu , Uemizu Kazunori , Ueno Munetaka , Watarai Hidenori
Published: March 2014

We report on the first results of a near- and mid-infrared deep survey with the Infrared Camera (IRC) onboard AKARI in the performance-verification phase. Simultaneous observations by the Near-InfraRed (NIR), Mid-InfraRed Short (MIR-S), and Mid-InfraRed Long (MIR-L) channels of the IRC with effective integration times of 4529, 4908, and 4417 seconds at 3, 7, and 15$\mu $m, covering 86.0, 70.3, and 77.3 arcmin$^2$ area, detected 955, 298, and 277 sources, respectively. The 5 $\sigma$ detection limits of the survey are 6.0, 31.5, and 71.2$\mu $Jy and the 50% completeness limit are 24.0, 47.5, and 88.1$\mu $Jy at 3, 7, and 15$\mu $m, respectively. Observation are limited by source confusion at 3$\mu $m. We have confirmed the turnover in the 15$\mu $m differential source counts around 400$\mu $Jy, previously detected by surveys with the Infrared Space Observatory. The faint end of 15$\mu $m raw source counts agrees with those from deep surveys in the GOODS fields, carried out with the Spitzer IRS peak up imager and predictions of current galaxy evolution models. These results indicate that deep surveys with comprehensive wavelength coverage at mid-infrared wavelength are very important to investigate the evolution of infrared galaxies at high redshifts.
Optical Identification of 15$\mu $m Sources in the AKARI Performance Verification Field toward the North Ecliptic Pole
Authors: Matsuhara Hideo , Wada Takehiko , Pearson Chris P. , Oyabu Shinki , Im Myungshin , Imai Koji , Takagi Toshinobu , Kang Eugene , Hwang Narae , Jeong Woong-Seob , Lee Hyung Mok , Lee Myung Gyoon , Pak Soojong , Serjeant Stephen , Nakagawa Takao , Hanami Hitoshi , Inami Hanae , Onaka Takashi , Fujishiro Naofumi , Ishihara Daisuke , Ita Yoshifusa , Kataza Hirokazu , Kim Woojung , Matsumoto Toshio , Murakami Hiroshi , Ohyama Youichi , Sakon Itsuki , TanabÉ Toshihiko , Uemizu Kazunori , Ueno Munetaka , Watarai Hidenori
Published: March 2014

We present the results of optical identifications for 257 mid-infrared sources detected with a deep 15$\;\mu$m survey over approximately 80 arcmin$^2$ area in the AKARI performance verification field near the North Ecliptic Pole. The 15$\;\mu$m fluxes of the sources range from 1 mJy down to 40 $\mu $Jy, approximately one half of which are below 100 $\mu $Jy. Optical counterparts were searched for within a 2$^{\prime\prime}$-3$^{\prime\prime}$ radius in both the $BVRi'z'$ catalog generated by using the deep Subaru/Suprime-cam field, which covers one-third of the performance verification field, and the $g'r'i'z'$ catalog based on observations made with MegaCam at CFHT. We found that the $B-R$ and $R-z'$ colors of sources with successful optical identifications are systematically redder than that of the entire optical sample in the same field. Moreover, approximately 40% of the 15$\;\mu$m sources show colors with $R-$L15$\gt$ 5, which cannot be explained by the spectral energy distribution (SED) of normal quiescent spiral galaxies, but are consistent with SEDs of redshifted ($z\gt1$) starburst or ultraluminous infrared galaxies. This result indicates that the fraction of the ultraluminous infrared galaxies in our faint 15$\;\mu$m sample is much larger than that in our brighter 15$\;\mu$m sources, which is consistent with the evolving mid-infrared luminosity function derived by recent studies based on Spitzer 24$\;\mu$m deep surveys. Based on an SED fitting technique, the nature of the faint 15$\;\mu$m sources is further discussed for a selected number of sources with available $K_{\rm s}$-band data.
Hinode Observations of Horizontal Quiet Sun Magnetic Flux and the “Hidden Turbulent Magnetic Flux”
Authors: Lites Bruce , Socas-Navarro Hector , Kubo Masahito , Berger Thomas E. , Frank Zoe , Shine Richard A. , Tarbell Theodore D. , Title Alan M. , Ichimoto Kiyoshi , Katsukawa Yukio , Tsuneta Saku , Suematsu Yoshinori , Shimizu Toshifumi , Nagata Shin’ichi
Published: March 2014

We present observations of magnetic fields of the very quiet Sun near disk center using the Spectro-Polarimeter of the Solar Optical Telescope aboard the Hinode satellite. These observations reveal for the first time the ubiquitous presence of horizontal magnetic fields in the internetwork regions. The horizontal fields are spatially distinct from the vertical fields, demonstrating that they are not arising mainly from buffeting of vertical flux tubes by the granular convection. The horizontal component has an average “apparent flux density” of 55 Mxcm$^{-2}$ (assuming the horizontal field structures are spatially resolved), in contrast to the average apparent vertical flux density of 11 Mxcm$^{-2}$. The vertical fields reside mainly in the intergranular lanes, whereas the horizontal fields occur mainly over the bright granules, with a preference to be near the outside edge of the bright granules. The large apparent imbalance of vertical and horizontal flux densities is discussed, and several scenarios are presented to explain this imbalance.
Formation Process of a Light Bridge Revealed with the Hinode Solar Optical Telescope
Authors: Yukio Katsukawa , Yokoyama Takaaki , Berger Thomas E. , Ichimoto Kiyoshi , Kubo Masahito , Lites Bruce , Nagata Shin’ichi , Shimizu Toshifumi , Shine Richard A. , Suematsu Yoshinori , Tarbell Theodore D. , Title Alan M. , Tsuneta Saku
Published: March 2014

The Solar Optical Telescope (SOT) on-board Hinode successfully and continuously observed the formation process of a light bridge in a matured sunspot of the NOAA active region 10923 for several days with high spatial resolution. During its formation, many umbral dots were observed to be emerging from the leading edges of penumbral filaments, and rapidly intruding into the umbra. The precursor of the light bridge formation was also identified as a relatively slow inward motion of the umbral dots, which emerged not near the penumbra, but inside the umbra. The spectro-polarimeter on SOT provided physical conditions in the photosphere around the umbral dots and the light bridges. We found that the light bridges and the umbral dots had significantly weaker magnetic fields associated with upflows relative to the core of the umbra, which implies that there was hot gas with weak field strength penetrating from the subphotosphere to near the visible surface inside those structures. There needs to be a mechanism to drive the inward motion of the hot gas along the light bridges. We suggest that the emergence and the inward motion are triggered by a buoyant penumbral flux tube as well as subphotospheric flow crossing the sunspot.
Initial Results on Line-of-Sight Field Calibrations of SP/NFI Data Taken by SOT/Hinode
Authors: Chae Jongchul , Moon Yong-Jae , Park Young-Deuk , Ichimoto Kiyoshi , Sakurai Takashi , Suematsu Yoshinori , Tsuneta Saku , Katsukawa Yukio , Shimizu Toshifumi , Shine Richard A. , Tarbell Theodore D. , Title Alan M. , Lites Bruce , Kubo Masahito , Nagata Shin’ichi , Yokoyama Takaaki
Published: March 2014

We present initial results on the line-of-sight field calibration of the two kinds of Stokes $I$ and $V$ data taken by the Solar Optical Telescope on the satellite Hinode: spectral profiles of Stokes $I$ and $V$ parameters recorded on the Spectro-polarimeter (SP), and monochromatic images of the same parameters recorded on the Narrow-band Filter Imager (NFI). By applying the center-of-gravity method to the SP data of AR10930 taken on 2006 December 11, we determined the line-of-sight field at every location in the active region. As a result, we found that the line-of-sight field strength ranges up to 2 kG in plages, even without taking into account the filling factor, and up to 3.5 kG or higher values inside the umbra of the major sunspot. We calibrated the NFI data in reference to the field determined from the SP data. In regions outside the sunspots and the penumbral regions, we adopted a linear relation, $B_\Vert=\beta V/I$, between the circular polarization, $V/I$, and the line-of-sight field strength, $B_\Vert$, and obtained $\beta=$ 23.5 kG in regions outside the sunspots, and $\beta=$ 12.0 kG in penumbral regions. In umbral regions of sunspots, a first-order polynomial was adopted to model the reversal of the polarization signal over the field strength.
A Tale of Two Spicules: The Impact of Spicules on the Magnetic Chromosphere
Authors: De Pontieu Bart , McIntosh Scott , Hansteen Viggo H. , Carlsson Mats , Schrijver Carolus J. , Tarbell Theodore D. , Title Alan M. , Shine Richard A. , Suematsu Yoshinori , Tsuneta Saku , Katsukawa Yukio , Ichimoto Kiyoshi , Shimizu Toshifumi , Nagata Shin’ichi
Published: March 2014

We use high-resolution observations of the Sun in Ca II H (3968 Å) from the Solar Optical Telescope on Hinode to show that there are at least two types of spicules that dominate the structure of the magnetic solar chromosphere. Both types are tied to the relentless magnetoconvective driving in the photosphere, but have very different dynamic properties. “Type-I” spicules are driven by shock waves that form when global oscillations and convective flows leak into the upper atmosphere along magnetic field lines on 3–7 minute timescales. “Type-II” spicules are much more dynamic: they form rapidly (in $\sim$10s), are very thin ($\le 200$ km wide), have lifetimes of 10–150s (at any one height), and seem to be rapidly heated to (at least) transition region temperatures, sending material through the chromosphere at speeds of order 50–150 km s$^{-1}$. The properties of Type II spicules suggest a formation process that is a consequence of magnetic reconnection, typically in the vicinity of magnetic flux concentrations in plage and network. Both types of spicules are observed to carry Alfvén waves with significant amplitudes of order 20 km s$^{-1}$.
Observations of Transient Active Region Heating with Hinode
Authors: Warren Harry P. , Ugarte-Urra Ignacio , Brooks David H. , Cirtain Jonathan W. , Williams David R. , Hara Hirohisa
Published: March 2014

We present observations of transient active region heating events observed with the Extreme Ultraviolet Imaging Spectrometer (EIS) and X-ray Telescope (XRT) on Hinode. This initial investigation focuses on NOAA active region 10940 as observed by Hinode on 2007 February 1 between 12 and 19UT. In these observations we find numerous examples of transient heating events within the active region. The high spatial resolution and broad temperature coverage of these instruments allows us to track the evolution of coronal plasma. The evolution of the emission observed with XRT and EIS during these events is generally consistent with loops that have been heated and are cooling. We have analyzed the most energetic heating event observed during this period, a small GOES B-class flare, in some detail and present some of the spectral signatures of the event, such as relative Doppler shifts at one of the loop footpoints and enhanced line widths during the rise phase of the event. While the analysis of these transient events has the potential to yield insights into the coronal heating mechanism, these observations do not rule out the possibility that there is a strong steady heating level in the active region. Detailed statistical analysis will be required to address this question definitively.
The Temperature and Density Structure of an Active Region Observed with the Extreme-Ultraviolet Imaging Spectrometer on Hinode
Authors: Doschek George A. , Mariska John T. , Warren Harry P. , Culhane Len , Watanabe Tetsuya , Young Peter R. , Mason Helen E. , Dere Kenneth P.
Published: March 2014

The Extreme-Ultraviolet Imaging Spectrometer (EIS) on Hinode produces high resolution spectra that can be combined via rasters into monochromatic images of solar structures, such as active regions. Electron temperature and density maps of the structures can be obtained by imaging the structures in different spectral lines with ratios sensitive to either temperature or density. Doppler maps and ion temperature maps can be made from spectral line wavelengths and profiles, respectively. In this paper we discuss coronal temperature and density distributions within an active region, illustrating the power of EIS for solar plasma diagnostics.
Velocity Structure of Jets in a Coronal Hole
Authors: Kamio Suguru , Hara Hirohisa , Watanabe Tetsuya , Matsuzaki Keiichi , Shibata Kazunari , Culhane Len , Warren Harry P.
Published: March 2014

The velocity structures of jets in a coronal hole have been derived for the first time. Hinode observations revealed the existence of many bright points in coronal holes. They are loop-shaped and sometimes associated with coronal jets. Spectra obtained with the Extreme-ultraviolet Imaging Spectrometer aboard Hinode were analyzed to infer the Doppler velocity of bright loops and jets in a coronal hole of the north polar region. Elongated jets above bright loops are found to be blue-shifted by 30 km s$^{-1}$ at maximum, while foot points of bright loops are red-shifted. Blue-shifts detected in coronal jets are interpreted as being upflows produced by magnetic reconnection between emerging flux and the ambient field in the coronal hole.
A Study of Polar Jet Parameters Based on Hinode XRT Observations
Authors: Savcheva Antonia , Cirtain Jonathan , DeLuca Edward E. , Lundquist Loraine L. , Golub Leon , Weber Mark , Shimojo Masumi , Shibasaki Kiyoto , Sakao Taro , Narukage Noriyuki , Tsuneta Saku , Kano Ryouhei
Published: March 2014

Hinode/SOHO campaign 7197 is the most extensive study of polar jet formation and evolution from within both the north and south polar coronal holes so far. For the first time, this study showed that the appearance of X-ray jets in the solar coronal holes occurs at very high frequency–about 60 jets d$^{-1}$ on average. Using observations collected by the X-Ray Telescope on Hinode, a number of physical parameters from a large sample of jets were statistically studied. We measured the apparent outward velocity, the height, the width and the lifetime of the jets. In our sample, all of these parameters show peaked distributions with maxima at 160 km s$^{-1}$ for the outward velocity, 5$\times$10$^4$km for the height, 8$\times$10$^3$km for the width, and about 10 min for the lifetime of the jets. We also present the first statistical study of jet transverse motions, which obtained transverse velocities of 0–35 km s$^{-1}$. These values were obtained on the basis of a larger (in terms of frequency) and better sampled set of events than what was previously statistically studied (Shimojo et al. 1996, PASJ, 48, 123). The results were made possible by the unique characteristics of XRT. We describe the methods used to determine the characteristics and set some future goals. We also show that despite some possible selection effects, jets preferably occur inside the polar coronal holes.
Radiative Transfer in Relativistic Accretion-Disk Winds
Authors: Fukue Jun
Published: March 2014

Radiative transfer in a relativistic accretion-disk wind is examined under a plane-parallel approximation in a fully special relativistic treatment. For an equilibrium flow, where the flow speed and the source function are constant, the emergent intensity is analytically obtained. In such an equilibrium flow the usual limb-darkening effect does not appear, since the source function is constant. Due to the Doppler and aberration effects associated with the relativistic motion of winds, however, the emergent intensity is strongly enhanced toward the flow direction. This is called the relativistic peaking effect . We thus carefully treat and estimate the appearance of relativistic winds and jets, when we observe them in an arbitrary direction.
Development of Iodine Cells for Subaru HDS and Okayama HIDES. III. An
Improvement on the Radial-Velocity Measurement Technique
Authors: Kambe Eiji , Ando Hiroyasu , Sato Bun’ei , Izumiura Hideyuki , Sekii Takashi , Paulson Diane B. , Yanagisawa Kenshi , Masuda Seiji , Shibahashi Hiromoto , Hatzes Artie P. , Martic Milena , Lebrun Jean-Claude , Mkrtichian David E. , Kiss Laszlo L. , Bruntt Hans , O’Toole Simon J. , Bedding Timothy R.
Published: March 2014

An improvement of the radial-velocity measurement accuracy is crucial for the detection of tiny stellar oscillations and exoplanets. Through the analysis of week-long extensive observations of solar-type stars (Procyon in 2000, 2002, and 2006/2007 and $\tau$ Cet in 2002 and 2006/2007), we have carefully examined, revised, and finely tuned the widely used multiple Gaussian IP fitting method for the spectrograph, HIDES. By determining a necessary and sufficient number of free parameters in the model as well as introducing an iterative process in the radial-velocity analysis, we can reach a precision of below 3ms $^{-1}$ , which is much smaller than the precision of 6ms $^{-1}$ officially announced so far for HIDES. We also make our technique refined for the 2002 McDonald Procyon data. Even with our revised method, slow radial velocity variations with an amplitude of about 10ms $^{-1}$ are left in the Procyon data. We emphasize that it is neither due to particular observing instruments nor radial-velocity analysis, and thus could be due to stellar origin. The analysis presented here makes the foundations of our next scientific analysis of the radial-velocity variations of Procyon, which will be presented in our forthcoming papers.
JVN Observations of H2O Masers around the Evolved Star IRAS 22480+6002
Authors: Imai Hiroshi , Fujii Takahiro , Omodaka Toshihiro , Deguchi Shuji
Published: March 2014

We report on the H$_2$O maser distributions around IRAS 22480$+$6002 ($=$ IRC$+$60370), observed with the Japanese VLBI Network (JVN) at three epochs spanning 2 months. This object was identified as a K-type supergiant in the 1970s, which was unusual as a stellar maser source. The spectrum of H$_2$O masers consists of 5peaks separated roughly equally by a fewkms$^{-1}$ each. The H$_2$O masers were spatially resolved into more than 15features, which spread about 50mas along the east–west direction. However, no correlation was found between the proper-motion vectors and their spatial positions; the velocity field of the envelope seems to be random. A statistical parallax method applied to the observed proper-motion data set gives a distance of $1.0\pm 0.4$kpc for this object, which is considerably smaller than previously thought. The distance indicates that this is an evolved star with $L\sim$5800$L_{\odot}$. This star shows radio, infrared, and optical characteristics that are quite similar to those of population II post-AGB stars, such as RV Tau variables.
Height Dependence of Gas Flows in an Ellerman Bomb
Authors: Matsumoto Takuma , Kitai Reizaburo , Shibata Kazunari , Otsuji Kenichi , Naruse Takuya , Shiota Daikou , Takasaki Hiroyuki
Published: March 2014

We performed spectroscopic observations of Ellerman bombs (EBs) in an active region of NOAA 10705 at Hida Observatory on 2004 November 24. The photospheric velocity fields of EBs have for the first time been investigated spectroscopically. From the Doppler shifts of a Ti II absorption line (6559.576 Å) and a broad H$\alpha$ emission line, we derived the photospheric velocity and the lower chromospheric velocity, respectively. The photospheric velocity of EBs was $\sim 0.2$kms$^{-1}$, indicating downward flow, on average. We found that the photospheric velocity variation of EBs has a good temporal correlation with the H$\alpha$ wing emission variation. On the other hand, the chromospheric velocity showed an upward flow of $\sim$1–3 kms$^{-1}$ on the average. From the characteristics of the flow field, we conclude that the observed EB occurred at the upper photospheric level. We suggest that it is important to know the motions of EBs in the photosphere because a plausible triggering mechanism of EBs is magnetic reconnection in the low-lying atmosphere.
Broad-Line and Multi-Wave Band Emission from Blazars
Authors: Yi Tingfeng , Xie Guangzhong
Published: March 2014

We studied the correlations of the flux of the broad-line emission ($F_{\rm BLR}$) with the X-ray emission flux, optical emission flux at 5500 ${\AA}$ and radio emission flux at 5 GHz, respectively, for a large sample of 50 blazars [39 flat-spectrum radio quasars (FSRQs) and 11 BL Lac objects]. Our main results are as follows. There are very strong correlations between $F_{\rm BLR}$ and $F_{\rm X}$ and between $L_{\rm BLR}$ and $L_{\rm X}$ in both states for 39 FSRQs, and the slopes of the linear-regression equations are almost equal to 1. There are weak correlations between $F_{\rm BLR}$ and $F_{\rm X}$ and between $L_{\rm BLR}$ and $L_{\rm X}$ for 11 BL Lac objects in both states, and the slopes of the linear-regression equations are close to 1. There are significant correlations between $F_{\rm BLR}$ and $F_{\rm X}$ and between $L_{\rm BLR}$ and $L_{\rm X}$ for 50 blazars in both states, the slopes of both linear-regression equations are also close to 1. These results support a close link between relativistic jets and accretion onto the central Kerr black hole. On the other hand, we find that BL Lac objects have a low accretion efficiency, $\eta$, whereas FSRQs have a high $\eta$. The unified model of FSRQs and BL Lac objects is also discussed.
Near-Infrared Spectra of 21 Wolf–Rayet Stars: Wind Clumping and Mass-Loss Rates
Authors: Nishimaki Yuichirou , Yamamuro Tomoyasu , Motohara Kentaro , Miyata Takashi , Tanaka Masuo
Published: March 2014

We present 0.9–2.4$\mu$m spectra of 21 galactic Wolf–Rayet (WR) stars that were obtained by using an echelle spectrograph attached to the 1.5 m infrared telescope in Tokyo. The observed Wolf–Rayet stars contain 12WNE, 3WNL, and 6WC stars. The near-infrared continuum spectra can be fitted by the superposition of stellar blackbody radiation with a stellar effective temperatures, $T_*$, of 30–60 kK and free–free radiation from the stellar wind with an electron temperature, $T_{\rm e}$, of $\sim$15 kK. However, these calculated spectra show an excess at cm wavelength compared with the cm data for almost all stars. This may be interpreted by an infrared excess flux possibly due to the clumping of the stellar wind gas. Assuming an “enhancement factor” that depends on the distance from the center of the stars as $\sim r^{-\omega}$, we can reproduce both our near-infrared spectra and the cm data by this clump-corrected free–free radiation with mass-loss rates similar to those derived by Nugis et al. On the other hand, we also estimated the mass-loss rates from our He i 1.083 and He ii 1.012 fluxes without a consideration of clumping, although a more detailed consideration should be necessary in order to estimate more reliable values of the mass-loss rates from the He line fluxes.
Dipolar Oscillations of Stars in General Relativity
Authors: Takata Masao
Published: March 2014

We present a concise second-order system of ordinary differential equations that describes the adiabatic dipolar oscillation of spherically-symmetric stars in general relativity. The derivation of the system is accomplished by formulating the equations as a Hamiltonian system, and reconsidering a known algebraic relation among the perturbed variables as an integral of the system. The new formulation allows us to examine the structure of eigenfunctions and properties of the eigenfrequency spectrum, so that we can establish a scheme to classify eigenmodes into p-modes and g-modes with mathematical rigorousness. We can also discuss the condition for the existence of dynamically-unstable modes. All of these analyses are totally analogous to those developed in the Newtonian case.
Photometric Studies of New Southern SU UMa-Type Dwarf Novae, FL Trianguli Australis and CTCV J0549–4921
Authors: Imada Akira , Kato Taichi , Berto Monard L. A. G. , Stubbings Rod , Uemura Makoto , Ishioka Ryoko , Nogami Daisaku
Published: March 2014

We report on the time-resolved optical CCD photometry of newly discovered SU UMa-type dwarf novae, FL TrA and CTCVJ0549$-$4921. During a 2006 August outburst, we detected superhumps with a period of 0.59897(11) days for FL TrA, clarifying the SU UMa nature of the system. On the first night of our observations of FL TrA, the object showed no superhumps. This implies that it takes a few days for the full development of superhumps. The superhump period variation diagram of FL TrA was similar to that observed in some WZ Sge stars and short-period SU UMa-type stars. This indicates that the system is closely related to WZ Sge stars and SU UMa stars having short orbital periods. For CTCV J0549$-$4921, the candidates of the mean superhump period are 0.083249(10) days and 0.084257(8) days, respectively. Due to a lack of observations, we cannot determine the true superhump period, but the latter period is favorable. Using the ASAS-3 archive, it turned out that the system showed only four outbursts over the past 6 years. The outburst amplitude of CTCV J0549$-$4921 was relatively small, with about 4.5 mag. One possibility is that mass evaporation may play a role during quiescence.
A Comparative Study of Size Distributions for Small L4 and L5 Jovian Trojans
Authors: Yoshida Fumi , Nakamura Tsuko
Published: March 2014

We examined the size distributions of small L4 and L5 Jovian Trojan asteroids detected in the Subaru main belt asteroid survey (SMBAS). This was the first attempt to make a comparison of the size distribution between the L4 and L5 Trojans for sizes ranging from $\sim1$ km to $\sim10$km, using the results of systematic surveys. We detected 51 L4 Trojans and 62 L5 Trojans ranging from 0.7 km to 13 km in diameter ($D$) (assuming an albedo of 0.04). We found that there is a difference of the cumulative size distribution between the L4 and L5 populations. The slopes of the cumulative size distribution of the L4 population with 2 km${<}D{<}$5 km and 5 km${<}D{<}$10 km were 1.3$\pm$0.1 and 2.4$\pm$0.1, respectively; meanwhile, that of the L5 population with 2 km${<}D{<}$5 km was $2.1\pm0.3$. For both populations, we also give composite size distributions covering a range of 5 km${<}D{<} \sim$ 100 km, whose mean slopes are found to be 2.2$\pm$0.1 for L4 and 2.1$\pm$0.1 for L5.
Performance Measurements of 8-Gsps 1-bit ADCs Developed for Wideband Radio Astronomical Observations
Authors: Okuda Takeshi , Iguchi Satoru
Published: March 2014

8-Gsps 1-bit Analog-to-Digital Converters (ADCs) were newly developed toward the realization of wideband observations. The development of wideband ADCs is one of the most essential developments for the radio interferometer. To evaluate its performance in interferometric observations, the time (phase) stability and frequency response were measured with a noise source and a signal generator. The results of these measurements show that the developed ADCs can achieve a jitter time of less than 0.05 ps at a time interval of 1second, a passband frequency response with a slope of less than 0.73 dBGHz$^{-1}$ and a ripple of less than 1.8 dB, and an aperture time of less than 20 ps. The details of the developed ADC design, the measurement methods, and the results of these measurements are presented in this paper.