bluuebunny/crossref_metadata_2025_split huggingface dataset:
Another Interpretation of the Disk-Line Profile for the Seyfert 1 Galaxy MCG $-$ 6-30-15
Authors: Inoue Hajime , Matsumoto Chiho 
Published: March 2014

Abstract
The Seyfert 1 galaxy MCG$-$6-30-15 is a representative object possessing a “disk-line” (a broad and skewed feature around 5–7 keV in an X-ray spectrum). Using the longest MCG$-$6-30-15 observation with ASCA, Matsumoto et al. (2003, PASJ, 55, 615) found an interesting time-variability: the RMS variability as a function of a time-bin-width decreases more rapidly in the disk-line energy band (5.0–6.6 keV) than those in the other energy bands, as the time-bin-width increases from $\sim 10^{4} \,\mathrm{s}$ to $\sim 10^{5} \,\mathrm{s}$. In this paper, we argue that this energy-dependent change in the RMS variability as a function of the time-bin-width is difficult to be reproduced by simply considering the variability of a “disk-line”, but that the RMS variability of the continuum component should have an energy-dependent evolution associated with the time-bin-width change. Such an energy-dependent variability of the continuum component can be realized by introducing absorption components with the typical variation time scale longer than that of the continuum. In this interpretation, a significant part of the broad excess feature in 5–7 keV is considered to be the result of a transparent spectral window of the warm absorbers.
X-Ray Observation on the Monoceros R2 Star-Forming Region with the Chandra ACIS-I Array
Authors: Nakajima Hiroshi , Imanishi Kensuke , Takagi Shin-ichiro , Koyama Katsuji , Tsujimoto Masahiro 
Published: March 2014

Abstract
We report on the results of the Chandra ACIS-I observation on the central region of the Monoceros R2 cloud (Mon R2), a high-mass star-forming region (SFR) at a distance of 830 pc. With a deep exposure of $\sim 100 \,\mathrm{ks}$, we detected 368 X-ray sources, $\sim 80\%$ of which were identified with the near-infrared (NIR) counterparts. We systematically analyzed the spectra and time variability of most of the X-ray emitting sources and provided a comprehensive X-ray source catalog for the first time. Using the $J$-, $H$-, and $K$-band magnitudes of the NIR counterparts, we estimated the evolutionary phase (classical T Tauri stars and weak-lined T Tauri stars) and the mass of the X-ray emitting sources, and analyzed the X-ray properties as a function of the age and mass. We found a marginal hint that classical T Tauri stars have a slightly higher temperature (2.4 keV) than that of weak-lined T Tauri stars (2.0 keV). A significant fraction of the high- and intermediate-mass sources have a time variability and high plasma temperatures (2.7 keV) similar to those of low-mass sources (2.0 keV). We performed the same analysis for other SFRs, the Orion Nebula Cluster and Orion Molecular Cloud-2/3, and obtained similar results to Mon R2. This supports the earlier results of this observation obtained by Kohno et al. (2002, ApJ, 567, 423) and Preibisch et al. (2002, A&A, 392, 945) that high- and intermediate-mass young stellar objects emit X-rays via magnetic activity. We also found a significant difference in the spatial distribution between X-ray and NIR sources.
A Systematic Study of X-Ray Flares from Low-Mass Young Stellar Objects in the
$\rho$
Ophiuchi Star-Forming Region with Chandra
Authors: Imanishi Kensuke , Nakajima Hiroshi , Tsujimoto Masahiro , Koyama Katsuji , Tsuboi Yohko 
Published: March 2014

Abstract
We report on the results of a systematic study of X-ray flares from low-mass young stellar objects, using two deep exposure Chandra observations of the main region of the $\rho$ Ophiuchi star-forming cloud. From 195 X-ray sources, including class I–III sources and some young brown dwarfs, we detected a total of 71 X-ray flares. Most of the flares have the typical profile of solar and stellar flares, fast rise and slow decay, while some bright flares show unusually long rise timescales. We derived the time-averaged temperature ( $\langle kT\rangle$ ), luminosity ( $\langle L_{\mathrm{X}}\rangle$ ), rise and decay timescales ( $\tau_{\mathrm{r}}$ and $\tau_{\mathrm{d}}$ ) of the flares, finding that (1) class I–II sources tend to have a high $\langle kT\rangle$ , which sometimes exceeds 5 keV, (2) the distribution of $\langle L_{\mathrm{X}}\rangle$ during flares is nearly the same for all classes from $\sim 10^{29.5}$ to $\sim10^{31.5} \,\mathrm{erg} \,\mathrm{s}^{-1}$ , although there is a marginal hint of a higher $\langle L_{\mathrm{X}}\rangle$ distribution for class I than class II–III, and (3) positive and negative log-linear correlations are found between $\tau_{\mathrm{r}}$ and $\tau_{\mathrm{d}}$ , and $\langle kT\rangle$ and $\tau_{\mathrm{r}}$ . In order to explain these relations, we used the framework of magnetic reconnection model with heat conduction and chromospheric evaporation to formulate the observational parameters ( $\tau_{\mathrm{r}}$ , $\tau_{\mathrm{d}}$ , and $\langle kT\rangle$ ) as a function of the pre-flare (coronal) electronic density ( $n_{\mathrm{c}}$ ), the half-length of the reconnected magnetic loop ( $L$ ), and magnetic field strength ( $B$ ). The observed correlations are well reproduced if loop lengths are nearly the same for all classes, regardless of the existence of an accretion disk. The estimated loop length is almost comparable to the typical stellar radius of these objects ( $10^{10} \hbox{--} 10^{11} \,\mathrm{cm}$ ), which indicates that the observed flares are triggered by solar-type loops, rather than larger ones ( $\sim 10^{12} \,\mathrm{cm}$ ) connecting the star with its inner accretion disk. The higher $\langle kT\rangle$ observed for class I sources may be explained by a slightly higher magnetic field strength ( $\approx 500 \,\mathrm{G}$ ) than for class II–III sources (200–300 G).
The Radiant Structure of the Leonid Meteor Storm in 2001: Observations with a Telephoto Lens System
Authors: Ken’ichi Torii , Kohama Mitsuhiro , Yanagisawa Toshifumi , Ohnishi Kouji 
Published: March 2014

Abstract
We measured the radiant of the Leonid meteor storm in 2001 November by using new observational and analysis techniques. The radiant was measured as the intersections of lines which were detected and extrapolated from images obtained at a single observing site (Akeno Observatory, Japan). The images were obtained by two sets of telephoto lenses equipped with cooled CCD cameras. The measured radiant, $($R.A., Dec.$) = ( {154\rlap {.}{}^{\mathrm {\circ }}35} \pm {0\rlap {.}{}^{\mathrm {\circ }}15}, {21\rlap {.}{}^{\mathrm {\circ }}55} \pm {0\rlap {.}{}^{\mathrm {\circ} }15})$ (J2000), was found to be in reasonable agreement with theoretical prediction by McNaught and Asher (2001, WGN, 29, 156), which supports their dust trail theory.
Excitation of g-Mode Oscillations on Relativistic Disks by Parametric Resonances with a Warp
Authors: Kato Shoji 
Published: March 2014

Abstract
Excitations by parametric resonances of axisymmetric ($m=0$) and one-armed ($m=1$) $g$-mode oscillations on the innermost region of geometrically thin, relativistic disks are examined. As a deformation of the unperturbed disks from an axisymmetric steady state, which is necessary for the operation of parametric resonances, we assume a long-living warp. Analyses are made under the approximations that the oscillations are local in the radial direction in the sense that their radial wavelength is short compared with a radial characteristic length of the disk, but long compared with the disk thickness. The results show that $g$-mode oscillations are amplified by coupling with the warp through an intermediate state, which is higher harmonics in the vertical direction. The oscillations amplified have some particular frequencies. The frequency ratio of two typical oscillations is $\sim \sqrt{2}$, which is close to $3:2$ observed as twin kHz quasi-periodic oscillations in some X-ray binaries.
X-Ray Spectral Properties of Hot Gas Cavities around NGC 4636
Authors: Ohto Akimitsu , Kawano Naomi , Fukazawa Yasushi 
Published: March 2014

Abstract
A Chandra observation of NGC 4636 revealed that X-ray hot gas is violently disturbed. We investigated the detailed distributions of the temperature and absorption of hot gas, in order to derive information about the gas dynamics. The temperature gradually increases from 0.6 keV at the center to 0.78 keV at 2 arcmin of the galaxy center; this is consistent with previous measurements. On the other hand, the azimuthal profiles of the temperature and absorption strongly correlate with the disturbance of hot gas. The west part, at 80 arcsec from the galaxy center, exhibits a higher temperature by 0.1–0.2 keV and an excess absorption by $\sim 5 \times 10^{20} \,\mathrm{cm}^{-2}$ compared with the azimuthal averages. This unusual region corresponds to the western X-ray cavity with a size of 20 arcsec radius. The same behavior is also seen around the northeast cavity with a smaller size than the west part. It is suggested that these unusual regions were caused by dramatic outflow or jet from the galactic nuclei, considering the east–west symmetry. The outflow gas or jet might have disturbed the surrounding hot gas and created hole-like regions. The observed high temperature and excess absorption of unusual regions indicate that the rims of holes might have been compressed, heated, and then cooled down at the end stage. We also discuss the past possible nuclear activity in NGC 4636.
The Influence of a Dipole Magnetic Field on the Structures of Cyclotron Lines
Authors: Nishimura Osamu 
Published: March 2014

Abstract
We examined the structures of cyclotron resonant lines in a large-scaled atmosphere threaded by a dipole magnetic field. We found that the ratio of the centroid energies of the lines at the second harmonic and at the fundamental can be more than 2. This is mainly due to different values of the cross sections of cyclotron resonant scattering in each harmonic. Our calculations suggest that the effect of the dipole magnetic field could be confirmed by the variation of the ratio of these centroid energies. Our results also indicate that the 5 keV absorption feature detected in the observed spectra of the Soft Gamma Repeater SGR 1806$-$20 is not due to an electron-cyclotron resonance.
Four Probable T Tauri Stars in MBM 12
Authors: Ogura Katsuo , Sugitani Koji , Magakian Tigran Yu. , Movsessian Tigran A. , Nikogossian Elena H. , Itoh Yoichi , Tamura Motohide 
Published: March 2014

Abstract
Survey observations were carried out in the MBM 12 (sometimes referred to as Lynds 1457) dark cloud in search of $\mathrm{H}\alpha$ emission stars by using a slitless grism spectrograph on the 2.6-m reflector of Byurakan Astrophysical Observatory, Armenia. Four new $\mathrm{H}\alpha$ stars were detected by the survey and identified as candidate T Tauri stars by follow-up low-dispersion spectroscopy and/or near-infrared photometry.
Hydrogen Abundance in the Tachocline Layer of the Sun
Authors: Takata Masao , Shibahashi Hiromoto 
Published: March 2014

Abstract
Sound speed inversions of the Sun show that the profile of the relative difference between the Sun and the standard solar model has a sharp peak around $r / {{{R}_{\odot}}} = 0.65$, which is the location of the tachocline layer found by rotation inversions. It has been suggested that this sharp peak would be due to the difference, between the Sun and the model, in the hydrogen abundance in the tachocline layer, possibly caused by the weak-mixing process. In this paper, we quantitatively discuss the hydrogen abundance in the tachocline layer based on a seismic solar model, which was constructed using the sound speed and density profiles as well as the depth of the convection zone obtained by helioseismology. One of the important characteristics of the seismic solar model is that it gives us a hydrogen profile as a part of the solution. We find that the hydrogen abundance of the seismic solar model decreases more mildly than that of the standard solar models constructed by incorporating the diffusion process. This feature hardly depends on the profile of the heavy elements as well as the uncertainties in the opacity and the equation of state.
Design and Performance of the Wide-Field X-Ray Monitor on Board the High-Energy Transient Explorer 2
Authors: Shirasaki Yuji , Kawai Nobuyuki , Yoshida Atsumasa , Matsuoka Masaru , Tamagawa Toru , Torii Ken’ichi , Sakamoto Takanori , Suzuki Motoko , Urata Yuji , Sato Rie , Nakagawa Yujin , Takahashi Daiki , Fenimore Edward E. , Galassi Mark , Lamb Donald Q. , Graziani Carlo , Donaghy Timothy Q. , Vanderspek Roland , Yamauchi Makoto , Takagishi Kunio , Hatsukade Isamu 
Published: March 2014

Abstract
The Wide-field X-ray Monitor (WXM) is one of the scientific instruments carried on the High Energy Transient Explorer 2 (HETE-2) satellite launched on 2000 October 9. HETE-2 is an international mission consisting of a small satellite dedicated to provide broad-band observations and accurate localizations of gamma-ray bursts (GRBs). A unique feature of this mission is its capability to determine and transmit GRB coordinates in almost real-time through the burst alert network. The WXM consists of three elements: four identical Xe-filled one-dimensional position-sensitive proportional counters, two sets of one-dimensional coded apertures, and the main electronics. The WXM counters are sensitive to X-rays between 2 keV and 25 keV within a field-of-view of about 1.5 sr, with a total detector area of about $350 \,\mathrm{cm}^2$. The in-flight triggering and localization capability can produce a real-time GRB location of several to 30 arcmin accuracy, with a limiting sensitivity of $10^{-7} \,\mathrm{erg} \,\mathrm{cm}^{-2}$. In this report, the details of the mechanical structure, electronics, on-board software, ground and in-flight calibration, and in-flight performance of the WXM are discussed.
An Experimental Study of Submillimeter-Wave Horn Antennae for a Submillimeter-Wave Array
Authors: Matsunaga Mayumi , Sekimoto Yutaro , Matsunaga Toshiaki , Sakai Takeshi 
Published: March 2014

Abstract
This paper aims to introduce two types of submillimeter-wave horn antennae designed by the authors and to present numerical findings obtained by an evaluative testing system that has also been developed by the authors. Submillimeter-wave components are widely used in radio-astronomical observation systems. There is a need to minimize (1) the various losses possibly incurred in the wave-receiving unit, and (2) the quantity of the unwanted electromagnetic waves mixing in. It is a well-known fact that a corrugated horn antenna possesses very low levels of cross-polarized field intensity, loss, and side lobes. It is for this reason that the authors have chosen to use corrugated horn antennae as two types of such antennae—one designed for use in the range of 280 GHz to 360 GHz frequencies and tested at 280 GHz, 332 GHz, and 360 GHz, and the other designed for use in the range of 385 GHz to 500 GHz frequencies and tested at 385 GHz, 442.5 GHz, and 500 GHz. The measurements of the antenna beam patterns have been found to largely correspond to those of the numerical analyses; it may be concluded that the antennae are functionally as efficient as they were designed and the testing system doubtless serves the desired purpose.
Minkowski Functionals of SDSS Galaxies I : Analysis of Excursion Sets
Authors: Hikage Chiaki , Schmalzing Jens , Buchert Thomas , Suto Yasushi , Kayo Issha , Taruya Atsushi , Vogeley Michael S. , Hoyle Fiona , Gott J. Richard , Brinkmann Jon 
Published: March 2014

Abstract
We present a first morphometric investigation of a preliminary sample from the SDSS of 154287 galaxies with apparent magnitude $14.5 &lt; m_r &lt; 17.5$ and redshift $0.001 &lt; z &lt; 0.4$. We measure the Minkowski Functionals, which are a complete set of morphological descriptors. To account for the complicated wedge-like geometry of the present survey data, we construct isodensity contour surfaces from the galaxy positions in redshift space and employ two complementary methods of computing the Minkowski Functionals. We find that the observed Minkowski Functionals for SDSS galaxies are consistent with the prediction of a $\Lambda$-dominated spatially-flat Cold Dark Matter model with random-Gaussian initial conditions, within the cosmic variance estimated from the corresponding mock catalogue. We expect that future releases of the SDSS survey will allow us to distinguish morphological differences in the galaxy distribution with regard to different morphological types and luminosity ranges.
Radiative Collimation of Electron–Positron Jets II
Authors: Orihara Shiho , Fukue Jun 
Published: March 2014

Abstract
We consider a collimation and acceleration mechanism for relativistic jets emanating from an inner region of a relativistic accretion disk surrounding a Kerr black hole, with Keplerian angular momentum under disk radiation fields, taking into account the effect of radiation drag. When the jets consist of electron–positron pair plasmas and the disk luminosity is of the order of the Eddington luminosity, we found that the terminal speed is about $0.9 \,c$ for a Schwarzschild case, while it becomes $\sim 0.96 \,c$ for an extreme Kerr case. In such a case, the opening angle of jets is of the order of $5^\circ$. We also examined the opening angle and the listing degree when the disk radiation is not axisymmetric, but has a one-armed pattern. For the case of 0.3 amplitude, the opening angle is of the order of a few degrees, and the jet direction is bent by several degrees to $10^\circ$.
Abundance Analysis of the Silicon Star HR 6958
Authors: Kato Ken-ichi 
Published: March 2014

Abstract
The elemental composition of the chemically peculiar star HR 6958 has been studied with emphasis on doubly ionized rare earths. A visual region spectrum taken with the ELODIE spectrograph at the Haute-Provence Observatory was analyzed. A total of 40 elements including Pr III, Nd III, Tb III, Dy III, Ho III, and Er III were identified and their abundances computed. He is deficient by over 1 dex with respect to the Sun; the light elements (C-Ca), except for Si, have solar abundances; the iron group elements (Sc–Fe) are overabundant by 1 dex to 2 dex, with Ti and Cr highly overabundant; and the lanthanide rare earths are overabundant by 3 dex to 4 dex. This abundance pattern with He deficient, Si, Ti, Cr, Sr, and Pr overabundant indicates that HR 6958 is a member of Si stars.
TV Observation of the Leonid Meteor Shower in 2002: First Observation of a Faint Meteor Storm
Authors: Fujiwara Yasunori , Ueda Masayoshi , Kawasaki Yasuhiro , Nakamura Takuji 
Published: March 2014

Abstract
TV observations of the Leonid meteor shower were carried out between ${18{}^{\mathrm {h}}}$ (UT) and ${20\rlap {.}{}^{\mathrm {h}}5}$ (UT) on 2002 November 17. In total, 412 Leonid meteors were observed along with 303 non-Leonid meteors. Enhanced activity of faint ($\mbox{mag} \lt +10$ mag$&lt; +10$) Leonid meteors was observed between ${19\rlap {.}{}^{\mathrm {h}}5}$ (UT) and ${20\rlap {.}{}^{\mathrm {h}}5}$ (UT), with a peak influx of $1.8 \times 10^{-4} \,\mathrm{km}^{-2} \,\mathrm{s}^{-1}$. The activity of this peak was rich in faint meteors, without visible meteors, which was different from the storm observed in 2001 over Japan. Comparisons between the observed peak and several theoretical predictions are discussed.
GRAPE-6: Massively-Parallel Special-Purpose Computer for Astrophysical Particle Simulations
Authors: Makino Junichiro , Fukushige Toshiyuki , Koga Masaki , Namura Ken 
Published: March 2014

Abstract
In this paper, we describe the architecture and performance of the GRAPE-6 system, a massively-parallel special-purpose computer for astrophysical $N$-body simulations. GRAPE-6 is the successor of GRAPE-4, which was completed in 1995 and achieved the theoretical peak speed of 1.08 Tflops. As was the case with GRAPE-4, the primary application of GRAPE-6 is simulations of collisional systems, though it can also be used for collisionless systems. The main differences between GRAPE-4 and GRAPE-6 are (a) the processor chip of GRAPE-6 integrates 6 force-calculation pipelines, compared to one pipeline of GRAPE-4 (which needed 3 clock cycles to calculate one interaction), (b) the clock speed is increased from 32 to 90 MHz, and (C) the total number of processor chips is increased from 1728 to 2048. These improvements resulted in a peak speed of 64 Tflops. We also discuss the design of the successor of GRAPE-6.
The Infrared Counterpart of the X-Ray Nova XTE J1720—318
Authors: Tetsuya Nagata , Kato Daisuke , Baba Daisuke , Nishiyama Shogo , Nagayama Takahiro , Nagashima Chie , Kurita Mikio , Sato Shuji , Kato Taichi , Uemura Makoto , Yamaoka Hitoshi , Monard Berto , Ita Yoshifusa , Matsunaga Noriyuki , Nakajima Yasushi , Tamura Motohide , Nakaya Hidehiko , Sugitani Koji 
Published: March 2014

Abstract
We report on the discovery of an infrared counterpart to the X-ray transient XTE J1720$-$318 on 2003 January 18, nine days after an X-ray outburst, and the infrared light curve during the first 130 days after the outburst. The infrared light curve shows a decline of $\sim 1.2 \,\mathrm{mag}$ from the peak magnitude of $K_\mathrm{s} \sim 15.3$ over the observation period, and a secondary maximum, about 40 days after the outburst. Another small increase in the flux was also recorded about 20 days after the outburst. These increases were also detected in the X-ray light curve. The $J H K_\mathrm{s}$ colors are consistent with an X-ray irradiated accretion disk suffering an extinction of $A_V \sim 8$, which is also inferred from its X-ray spectrum and the extinction map constructed from far-infrared dust emission of this line of sight. These $J, H$, and $K_\mathrm{s}$ observations demonstrate that useful data can be obtained even for such an object, which suffers heavy optical extinction, possibly located beyond the galactic center.
Performance of Subaru Cassegrain Adaptive Optics System
Authors: Takami Hideki , Takato Naruhisa , Hayano Yutaka , Iye Masanori , Oya Shin , Kamata Yukiko , Kanzawa Tomio , Minowa Yosuke , Otsubo Masashi , Nakashima Koji , Gaessler Wolfgang , Saint-Jacques David 
Published: March 2014

Abstract
The design and performance of the Cassegrain Adaptive Optics (AO) system for the 8.2 m Subaru Telescope are reported. The system is based on a curvature wavefront sensor with 36 photon-counting avalanche photodiode modules and a bimorph wavefront correcting deformable mirror with 36 driving electrodes. The engineering first light of the AO system took place in 2000 December. The AO system has been in service since 2002 April for two open-use instruments, an infrared camera and spectrograph and a coronagraph imager with adaptive optics. The Strehl ratio in the $K$-band is around 0.3 for bright guide stars under ${0\rlap {.}{}^{\mathrm {\prime \prime }}4} K$-band seeing condition. The control loop performs with 2060 corrections per second. High sensitivity of the wavefront sensor allows significant improvement in the image quality, even for faint guide stars down to $R = 18 \,\mathrm{mag}$. The FWHM of stellar images in a globular cluster was measured to derive an estimation of the isoplanatic angle and was found nearly constant out to $30''$ from the guide star, indicating that the height of the effective turbulent layer of that particular night was less than 1.8 km. The on-going upgrade plans for a fivefold increase in the number of control elements and for the installation of a laser guide AO system are described.