bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three-Point Correlation Functions of SDSS Galaxies in Redshift Space: Morphology, Color, and Luminosity Dependence
Authors: Kayo Issha , Suto Yasushi , Nichol Robert C. , Pan Jun , Szapudi István , Connolly Andrew J. , Gardner Jeff , Jain Bhuvnesh , Kulkarni Gauri , Matsubara Takahiko , Sheth Ravi , Szalay Alexander S. , Brinkmann Jon 
Published: March 2014

Abstract
We present measurements of the redshift-space three-point correlation function of galaxies in the Sloan Digital Sky Survey (SDSS). For the first time, we analyze the dependence of this statistic on galaxy morphology, color, and luminosity. In order to control systematics due to selection effects, we used $r$-band, volume-limited samples of galaxies, constructed from magnitude-limited SDSS data ($14.5 &lt; r &lt; 17.5$), and further divided the samples into two morphological types (early and late) or two color populations (red and blue). The three-point correlation function of SDSS galaxies follows the hierarchical relation well, and the reduced three-point amplitudes in redshift-space are almost scale-independent ($Q_z = 0.5 \sim 1.0$). In addition, their dependence on the morphology, color, and luminosity is not statistically significant. Given the robust morphological, color, and luminosity dependences of the two-point correlation function, this implies that galaxy biasing is complex on weakly non-linear to non-linear scales. We show that a simple deterministic linear relation with the underlying mass could not explain our measurements on these scales.
ASCA Observations of the Two Nearest Globular Clusters, M 4 and NGC 6397
Authors: Ishikawa Teru , Ishida Manabu , Ishisaki Yoshitaka , Ohashi Takaya , Yamasaki Noriko Y. 
Published: March 2014

Abstract
We report on ASCA observations of the two nearby globular clusters, M 4 and NGC 6397. Although 14 and 8 sources were detected at more than the $5\,\sigma$ confidence level from each cluster field, respectively, the majority of them, except for the cores of both clusters, were found unlikely to be associated with the clusters. The core of NGC 6397 shows optically thin thermal plasma emission with a temperature of $kT \gtrsim 12 \,\mathrm{keV}$. This result supports the results of HST, ROSAT, and Chandra, indicating that the main constituent of the NGC 6397 core is cataclysmic variables (CVs). The high temperature suggests it to be magnetic CVs, which supports the result of the HST spectroscopy. The core of M 4 was unambiguously detected at a $\gtrsim 5\,\sigma$ confidence level for the first time. Although we cannot carry out a detailed spectral analysis on the M 4 core due to a statistical limitation, the hardness ratio of the detected photons is also consistent with CVs. We compared the ASCA fluxes of the core sources to those from other X-ray observations. The absorption-corrected 0.5–10keV flux of the NGC 6397 core with ASCA was obtained to be $2.5 \times 10^{-12} \,\mathrm{erg} \,\mathrm{cm}^{-2} \,\mathrm{s}^{-1}$, and had been constant within a factor of $\sim 2$ during 1993–2001. The M 4 core flux obtained under the same condition is $2.6 \times 10^{-13} \,\mathrm{erg} \,\mathrm{cm}^{-2} \,\mathrm{s}^{-1}$, which seems to be $\sim 4$ times as high as the ROSAT HRI flux, although the possibility of a constant flux between the ASCA and HRI observations cannot be excluded due to a statistical limitation. Spectral and temporal properties of other out-of-core sources, including the radio galaxy PKS 1620$-$260 and the G0V star V972 Sco, are also described.
On the Period Variation of the Neglected W UMa-type Binary System V714 Monocerotis
Authors: Sheng-Bang Qian , Boonrucksar Soonthornthum , Fu-Yuan Xiang , Li-Ying Zhu , Jia-Jia He 
Published: March 2014

Abstract
Some new CCD times of the light minimum for a neglected W UMa-type binary star, V714 Monocerotis, observed in 2002 and 2003, are presented. By considering the general trend of the $\mathrm{O}- \mathrm{C}$ variation, a plausible $\mathrm{O}- \mathrm{C}$ curve was formed and a mean linear ephemeris was obtained. It was found that the period of the binary star shows a continuous decrease with rate of $dP/dt =-1.48 \times 10^{-7} \;\mathrm{d} \;\mathrm{yr}^{-1}$. In order to understand the evolutionary state of the binary system, new photometric and spectroscopic observations and a careful investigation on those data are required.
A Fast Parallel Treecode with GRAPE
Authors: Makino Junichiro 
Published: March 2014

Abstract
In this paper, we describe an implementation of the Barnes–Hut treecode on a cluster of PCs (Beowulf-class machines) equipped with GRAPE hardware. Our implementation is designed to achieve good performance on clusters of GRAPE with a relatively slow network, such as the standard Gigabit Ethernet. With 12 processors, the speedup over single-processor code reaches around 10. Our code is available on the web.
Water-Vapor Maser Disk at the Nucleus of the Seyfert 2 Galaxy NGC 3079
Authors: Yamauchi Aya , Nakai Naomasa , Sato Naoko , Diamond Philip 
Published: March 2014

Abstract
We observed a Seyfert 2/LINER galaxy NGC 3079 using the NRO 45-m telescope from 1992 to 2002, and the Very Long Baseline Array (VLBA) in 2001 December, at 22 GHz. The 45-m telescope detected weak red-shifted and systemic features as well as strong blue-shifted features. High spatial resolution observations with the VLBA indicated that the $\mathrm{H_2O}$ maser spots are distributed along the north-south direction, showing blue-shifted velocities in the north and red-shifted in the south. We propose a nearly edge-on molecular gas disk in the nuclear region of NGC 3079, whose radius varies from 0.4 to 1.2 pc and whose thickness is 0.3 pc. The disk is rotating at $V_\mathrm{rot} = 200 \hbox{--} 100 \,\mathrm{km} \,\mathrm{s}^{-1}$, having a large velocity dispersion of $\Delta V \approx 50 \,\mathrm{km} \,\mathrm{s}^{-1}$. The binding mass within the disk is $\sim 10^6 \,{{{M}_{\odot}}}$. The disk is inclined such that the east side is nearest to us. The large luminosity of the maser emission and exceptionally strong blue-shifted features of NGC 3079 are probably the result of local shocks in the disk. Three continuum components are interpreted as jets emitted from the nucleus. The velocities of the components relative to the dynamical center of the masing disk are $(0.09 \hbox{--} 0.17) \,c, &lt;0.005 \,c$, and $&lt;0.05 \,c$.
Optical Observation of the 2003 Outburst of a Black Hole X-Ray Binary, V4641 Sagittarii
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Imada Akira , Nogami Daisaku , Monard Berto , Cook Lewis M. , Stubbings Rod , Kiyota Seiichiro , Nelson Peter , Beninger Jean-Yves , Bolt Greg , Heathcote Bernard 
Published: March 2014

Abstract
We report on the results of our optical photometric observations of a black hole X-ray binary, V4641 Sgr during an outburst in 2003 August. During the outburst, we detected several properties having noteworthy similarities to those observed during an outburst in 2002 May; the outburst lasted about 6 days, during which it exhibited flares and rapid fluctuations, having timescales of $10^{2\hbox{--}4} \,\mathrm{s}$. In complicated profiles of light curves, we identified several recurring patterns, which were also observed during the 2002 outburst. First, the object frequently experienced sudden temporary fadings, which we call “dips”, appearing just after the states characterized by strong short-term fluctuations. Second, we detected optical flashes, which are characterized by a brightening by $\sim 0.5 \,\mathrm{mag}$ within $\sim 50 \,\mathrm{s}$. Based on the similarity of the outbursts in 2002 and 2003, we conclude that they have the same nature. This is the first time that repetitive outburst phenomena have been confirmed in V4641 Sgr. The object probably has an outburst interval that can be as small as 1–2 years.
Probing Warm-Hot Intergalactic Medium Associated with the Virgo Cluster Using an Oxygen Absorption Line
Authors: Fujimoto Ryuichi , Takei Yoh , Tamura Takayuki , Mitsuda Kazuhisa , Yamasaki Noriko Y. , Shibata Ryo , Ohashi Takaya , Ota Naomi , Audley Michael D. , Kelley Richard L. , Kilbourne Caroline A. 
Published: March 2014

Abstract
To detect a warm-hot intergalactic medium (WHIM) associated with the large-scale structure of the universe, we observed a quasar behind the Virgo cluster with XMM-Newton. With 54 ks exposure, we marginally detected an O VIII $\mathrm{K}\alpha$ absorption line at $650.9^{+0.8}_{-1.9} \,\mathrm{eV}$ in the RGS spectra, with a statistical confidence of 96.4%. The observed line center energy is consistent with the redshift of M 87, and hence the absorber is associated with the Virgo cluster. From the curve of growth, the O VIII column density was estimated to be $\gtrsim 7 \times 10^{16} \,\mathrm{cm}^{-2}$. In the EPIC spectra, excess emission was found after evaluating the hot ICM in the Virgo cluster and various background components. We inspected the RASS map of the diffuse soft X-ray background, and confirmed that the level of the north and west regions just outside of the Virgo cluster is consistent with the background model that we used, while that of the east side is significantly higher and the enhancement is comparable with the excess emission found in the EPIC data. We consider a significant portion of the excess emission to be associated with the Virgo cluster, although a possible contribution from the North Polar Spur cannot be excluded. Using the column density and the emission measure and assuming an oxygen abundance of 0.1 and an ionization fraction of 0.4, we estimate that the mean electron density and the line-of-sight distance of the warm-hot gas are $\lesssim 6 \times 10^{-5} \,\mathrm{cm}^{-3}$ and $\gtrsim 9 \,\mathrm{Mpc}$. These strongly suggest detection of a WHIM in a filament associated with the Virgo cluster.
ASCA Compilation of X-Ray Properties of Hot Gas in Elliptical Galaxies and Galaxy Clusters: Two Breaks in the Temperature Dependences
Authors: Fukazawa Yasushi , Makishima Kazuo , Ohashi Takaya 
Published: March 2014

Abstract
Utilizing ASCA archival data of about 300 objects of elliptical galaxies, groups, and clusters of galaxies, we performed systematic measurements of the X-ray properties of hot gas in their systems, and compiled them in this paper. The steepness of the luminosity-temperature (LT) relation, $L_\mathrm{X} \propto (kT)^{\alpha}$, in the range of $kT \sim 1.5 \hbox{--} 15 \,\mathrm{keV}$ is $\alpha = 3.17 \pm 0.15$, consistent with previous measurements. In the relation, we find two breaks at around ICM temperatures of 1 keV and 4 keV: $\alpha = 2.34 \pm 0.29$ above 4 keV, $3.74 \pm 0.32$ in 1.5–5 keV, and $4.03 \pm 1.07$ below 1.5 keV. Such two breaks are also evident in the temperature and size relation. The steepness in the LT relation at $kT \gt 4 \,\mathrm{keV} kT \gt 4 \,\mathrm{keV}$ is consistent with the scale-relation derived from the CDM model, indicating that the gravitational effect is dominant in richer clusters, while poorer clusters suffer non-gravity effects. The steep LT relation below 1 keV is almost attributed to X-ray faint systems of elliptical galaxies and galaxy groups. We found that the ICM mass within the scaling radius $R_{1500}$ follows the relation of $M_\mathrm{gas} \propto T^{2.33\pm0.07}$ from X-ray faint galaxies to rich clusters. Therefore, we speculate that even such X-ray faint systems contain a large-scale hot gas, which is too faint to detect.
Inversion Formula for Determining the Parameters of an Astrometric Binary
Authors: Asada Hideki , Akasaka Toshio , Kasai Masumi 
Published: March 2014

Abstract
It is believed that some numerical technique must be employed for determining the system parameters of a visual binary or a star with a planet, because the relevant equations are not only highly nonlinear, but also transcendental owing to Kepler’s equation. Such common sense, however, is not true; we have discovered an analytic inversion formula, in which the original orbital parameters are expressed as elementary functions of the observable quantities, such as the location of four observed points and the time interval between these points. The key thing is that we use the time interval, but not the time of each observation, in order to avoid treating Kepler’s equation. The present formula can be applied even in cases where the observations cover a short arc of the orbit during less than one period. Thus, the formula will be useful in future astrometric missions, such as SIM, GAIA, and JASMINE.
Variable Star Network: World Center for Transient Object Astronomy and Variable Stars
Authors: Kato Taichi , Uemura Makoto , Ishioka Ryoko , Nogami Daisaku , Kunjaya Chatief , Baba Hajime , Yamaoka Hitoshi 
Published: March 2014

Abstract
Variable Star Network (VSNET) is a global professional-amateur network of researchers in variable stars and related objects, particularly in transient objects, such as cataclysmic variables, black-hole binaries, supernovae, and gamma-ray bursts. The VSNET has been playing a pioneering role in establishing the field of transient object astronomy, by effectively incorporating modern advances in observational astronomy and global electronic networks, as well as collaborative progress in theoretical astronomy and astronomical computing. The VSNET is now one of the best-featured global networks in this field of astronomy. We review the historical progress, design concept, associated technology, and a wealth of scientific achievements powered by VSNET.
Outburst and Post-Outburst Active Phase of the Black Hole X-Ray Binary V4641 Sagittarii in 2002
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Tanabe Kenji , Torii Ken’ichi , Santallo Roland , Monard Berto , Markwardt Craig B. , Swank Jean H. , Sault Robert J. , Macquart Jean-Pierre , Linnolt Michael , Kiyota Seiichiro , Stubbings Rod , Nelson Peter , Richards Tom , Bailyn Charles , West Doug , Masi Gianluca , Miyashita Atsushi , Sano Yasuo , Scarmato Toni 
Published: March 2014

Abstract
The black hole X-ray binary V4641 Sgr experienced an outburst in 2002 May, which was detected at X-ray, optical, and radio wavelengths. The outburst lasted for only 6 days, but the object remained active for the next several months. Here, we report on the detailed properties of light curves during the outburst and the post-outburst active phase. We reveal that rapid optical variations of $\sim 100 \,\mathrm{s}$ became more prominent when a thermal flare weakened and the optical spectrum flattened in the $I_{\mathrm{c}}$, $R_{\mathrm{c}}$, and $V$-band regions. In conjunction with the flat spectrum in the radio range, this strongly indicates that the origin of rapid variations is not thermal emission, but synchrotron emission. Just after the outburst, we detected repeated flares at optical and X-ray wavelengths. The optical and X-ray light curves exhibited a strong correlation with the X-rays lagging by about 7 min. The X-ray lag can be understood in terms of a hot region propagating into the inner region of the accretion flow. The short X-ray lag, however, requires modifications of this simple scenario to account for the short propagation time. We also detected high-amplitude rapid variations 50 days after the outburst, which we call optical flashes. During the most prominent optical flash, the object brightened by 1.2 mag only within 30 s. The released energy indicates that the emission source should be at the innermost region of the accretion flow.
Stellar Parameters and Photospheric Abundances of Late-G Giants: Properties of the Targets of the Okayama Planet Search Program
Authors: Takeda Yoichi , Sato Bun’ei , Kambe Eiji , Izumiura Hideyuki , Masuda Seiji , Ando Hiroyasu 
Published: March 2014

Abstract
Towards clarifying the properties of late-G giants, for which we are currently conducting a planet-search project at Okayama Astrophysical Observatory, an extensive spectroscopic study has been performed for our first target sample of fifty-seven G6–G9 III stars, in order to establish the atmospheric parameters ($T_{\mathrm{eff}}, \log g, v_\mathrm{t}$, and $\mathrm{[Fe/H]}$), the stellar mass along with the evolutionary status, and the photospheric abundances of various elements. It was confirmed that the conventional spectroscopic method of parameter determination using Fe I / II lines with the assumption of LTE works successfully for these evolved stars. We determined the abundances (relative to the Sun) of 19 elements, and examined how their $\mathrm{[X/Fe]}$ ratios behave themselves with the run of $\mathrm{[Fe/H]}$. While the trends appear to be similar to those exhibited by disk dwarfs for a number of elements, some elements (C, O, Na) showed appreciable anomalies, which may be interpreted as being due to a dredge-up of nuclear-processed material. Since the $\mathrm{[Fe/H]}$ values of these stars tend to be somewhat biased towards a subsolar regime, some mechanism of slightly reducing the metallicity might be suspected.
Black Hole Shadows of Charged Spinning Black Holes
Authors: Takahashi Rohta 
Published: March 2014

Abstract
We propose a method for measuring the black hole charge by imaging a black hole shadow in a galactic center by future interferometers. Even when the black hole is uncharged, it is possible to confirm the charge neutrality by this method. We first derive the analytic formulae of the black hole shadow in an optically thin medium around a charged spinning black hole, and then investigate how contours of the black hole shadow depend on the spin and the charge of the black hole for several inclination angles between the rotation axis of the black hole and the observer. This method only assumes a stationary black hole and general relativity. By fitting the formula of the contours of the shadow to the observed image of the shadow, in addition to the black hole charge, one can also determine the black hole spin and the inclination angle without any degeneracy among the charge, the spin, and the inclination angle unless the inclination angle is null. If the maximum width of a shadow smaller than $4 \, (1+2^{1/2})M$ or the minimum width of a shadow smaller than $9M$ is measured observationally, we can safely conclude that the black hole is charged. Here, $M$ is the gravitational radius, i.e. the half of the Schwarzschild radius.
Time-Series Analysis of Terrestrial Impact Crater Records
Authors: Chang Heon-Young , Moon Hong-Kyu 
Published: March 2014

Abstract
A database of impact craters becomes available with more accurate and more precise age estimates due to a new decay constant. This motivates us to revisit the periodicity hypothesis for the terrestrial impact cratering rate, using the new data set. We present a new way to analyze the impact cratering rate as an oscillator in the time domain. This technique aims to produce an accurate frequency of an oscillator whose phase is modulated, and to reveal the slowly varying phase function. Having applied the technique to recent cratering records, which are grouped into 6 subsamples by criteria on the age and diameter of impact craters, we found the presence of a $\sim 26 \,\mathrm{Myr}$ periodicity in the impact cratering rate over the last $\sim 250 \,\mathrm{Myr}$. Such a periodicity can be found consistently in subsamples regardless of the lower limit of the diameter up to $D \sim 35 \,\mathrm{km}$. We have also calculated the period of the impact cratering rate using the Lomb–Scargle periodogram method. The Lomb–Scargle periodogram method yields slightly more scattered periods, implying that our technique is more robust and stable than the Lomb-Scargle periodogram analysis. As reproducing $f(t)$, we found that its typical magnitude of $\epsilon\, \overline{f(t)}$ is much smaller than that of the frequency. Therefore, we conclude that the impact cratering rate may be regarded as unimodal.
Giant Flare of SGR 1806−20 from a Relativistic Jet
Authors: Yamazaki Ryo , Ioka Kunihito , Takahara Fumio , Shibazaki Noriaki 
Published: March 2014

Abstract
The Japanese magnetospheric explorer GEOTAIL recorded a detailed light curve during the initial 600 msec of a giant flare from SGR 1806$-$20 on 2004 December 27. We show that the observed light curve is well explained by emission from relativistically expanding fireballs, like those of gamma-ray bursts (GRBs). Especially, the observed rapid fading after 500 msec suggests that ejecta were collimated in a jet. We derived an upper limit on the jet opening half-angle of 0.2 rad, which is as narrow as those of GRBs.
Influence of a Non-Dipole Magnetic Field on the Peak Energies of Cyclotron Absorption Lines
Authors: Nishimura Osamu 
Published: March 2014

Abstract
We calculate cyclotron lines in a neutron star slab assuming a non-dipole surface magnetic field. We consider the influences of a non-dipole surface field on the properties of the cyclotron resonant scattering lines. When the magnetic field strength decreases with height in the line-forming region, the ratios of the higher harmonics to the fundamental at the peak energies of the cyclotron lines become less than classical harmonic ratios, $1 : 2 : 3 \dots$. On the other hand, when the magnetic field strength increases with height in the line-forming region, the ratios at the peak energies of the cyclotron lines become more than the classical harmonic ratios. The deviation from the harmonic ratios, which has actually been observed in some accretion-powered X-ray pulsars, is more significant than that expected from a relativistic effect in the cyclotron resonant energy. This may suggest the line-forming region is threaded by a strong non-dipole magnetic field in some accreting X-ray pulsars. In observations, the ratios are more or less than the classical harmonic ratios. This could imply that the magnetic field strength in the line-forming region decreases or increases with the altitude or the horizontal distance from an emission region.
Vectorization and Parallelization of the Adaptive Mesh Refinement N-Body Code
Authors: Yahagi Hideki 
Published: March 2014

Abstract
We describe our vectorized and parallelized adaptive mesh refinement (AMR) $N$-body code with shared time steps, and report its performance on a Fujitsu VPP5000 vector-parallel supercomputer. Our AMR $N$-body code puts hierarchical meshes recursively where higher resolution is required and the time step of all particles are the same. The parts that are the most difficult to vectorize are loops that access the mesh data and particle data. We vectorized such parts by changing the loop structure, so that the innermost loop steps through the cells instead of the particles in each cell, in other words, by changing the loop order from the depth-first order to the breadth-first order. We also parallelized our code for distributed memory machines. The important part of parallelization is data decomposition. We sorted the hierarchical mesh data by the Morton order, or the recursive N-shaped order, level by level and split and allocated the mesh data to the processors. Particles are allocated to the processor to which the finest refined cells including the particles are also assigned. Our timing analysis using $\Lambda$-dominated cold dark matter simulations shows that our parallel code speeds up almost ideally up to 32 processors, the largest number of processors in our test.
On Multipolar Analytical Potentials for Galaxies
Authors: Vogt Daniel , Letelier Patricio S. 
Published: March 2014

Abstract
We present analytical potential-density pairs in three dimensions for the gravitational field of galaxies, obtained by thickening the multipolar expansion up to the quadrupole term. These may be interpreted as generalizations of the Miyamoto and Nagai potential-density pairs. With a suitable restriction on the possible values of the multipole moments, the density distributions are positive and monotone decreasing functions of the radial and axial coordinates.