bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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.
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
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

Abstract
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

Abstract
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.
Performance Measurements of 8-Gsps 1-bit ADCs Developed for Wideband Radio Astronomical Observations
Authors: Okuda Takeshi , Iguchi Satoru 
Published: March 2014

Abstract
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.
Relativistic Variable Eddington Factor
Authors: Fukue Jun 
Published: March 2014

Abstract
We analytically derived a relativistic variable Eddington factor in relativistic radiative flow, and found that the Eddington factor depends on the velocity gradient as well as the flow velocity. When the gaseous flow is accelerated and there is a velocity gradient, there also exists a density gradient. As a result, an unobstructed viewing range by a comoving observer, where the optical depth measured from the comoving observer is unity, is not a sphere, but becomes an oval shape elongated in the direction of the flow; we call it a one-tau photo-oval. For a comoving observer, an inner wall of the photo-oval generally emits at a non-uniform intensity, and has a relative velocity. Thus, the comoving radiation fields observed by the comoving observer becomes anisotropic, and the Eddington factor must deviate from the value for the isotropic radiation fields. In the case of a plane-parallel vertical flow, we examine the photo-oval and obtain the Eddington factor. In a sufficiently optically thick linear regime, the Eddington factor is analytically expressed as $f (\tau, \beta, \frac{d\beta}{d\tau}) = \frac{1}{3} (1 + \frac{16}{15} \frac{d\beta}{d\tau})$, where $\tau$ is the optical depth and $\beta$ ($=v/c$) is the flow speed normalized by the speed of light. We also examined the linear and semi-linear regimes, and found that the Eddington factor generally depends both on the velocity and its gradient.
X-Ray Emissions from Three-Dimensional Magnetohydrodynamic Coronal Accretion Flows
Authors: Kawanaka Norita , Kato Yoshiaki , Mineshige Shin 
Published: March 2014

Abstract
We calculated the radiation spectrum and its time variability of a black-hole accretion disk-corona system based on a three-dimensional magnetohydrodynamic (MHD) simulation. In explaining the spectral properties of active galactic nuclei, it is often assumed that they consist of a geometrically thin, optically thick disk and hot, optically thin corona surrounding the thin disk. As for a model of the corona, we adopted the simulation data of three-dimensional, non-radiative MHD accretion flows calculated by Y. Kato and coworkers, while for a thin disk we assumed a standard-type disk. We performed Monte-Carlo radiative transfer simulations of the corona, while taking into account the Compton scattering of soft photons from the thin disk by hot thermal electrons and coronal irradiation heating of the thin disk, which emits blackbody radiation. By adjusting the density parameter of the MHD coronal flow, we could produce emergent spectra that are consistent with those of typical Seyfert galaxies. Moreover, we found rapid time variability in the X-ray emission spectra, originating from a density fluctuation produced by a magnetorotational instability in the MHD corona. The features of reflection component including iron fluorescent line emission are also briefly discussed.