bluuebunny/crossref_metadata_2025 huggingface dataset:
Near-Infrared Observations of the IRAS/SiO Sources in the Galactic Bulge: a Large Scale Distribution
Authors: Deguchi Shuji , Fujii Takahiro , Nakashima Jun-ichi , Wood Peter R.
Published: March 2014

Near-infrared photometric observations in the $ J$-, $ H$-, and $ K$-bands were made for 120 IRAS sources toward the Galactic bulge ($-10^{\circ} < l < 15^{\circ}$ and $ \vert b\vert < 3^{\circ}$, excluding $ \vert l\vert < 3^{\circ}$). They are well-confirmed, mass-losing late-type stars having accurate radial velocities derived from SiO maser observations. For 118 sources, single, unambiguous near-infrared counterparts were found within the errors of the IRAS/MSX positions; and for the other 2 sources, faint candidates only detectable in the $ K$-band were found. From the $ J$-, $ H$-, $ K$-band and IRAS 12 and 25$\, {\mu \mathrm {m}}$ intensities, we estimated the spectral energy distributions of the sources, and obtained distances assuming a constant intrinsic luminosity. Adding all of the distance data of the IRAS/SiO sources in $-10^{\circ} < l < 25^{\circ}$ published in previous papers, we mapped the positions of 272 sampled stars onto the Galactic plane. The map clearly shows a bar structure, where the major axis of the bar is oriented $ 22^{\circ}(\pm 8^{\circ}$) from the Sun-Galactic center line. We also reanalyzed the radial-velocity shift with the distance in this sample. These analyses suggest that the data are consistent with the current bar theory of the Galactic bulge.
Note on the “Dead Zone” in Layered Accretion Models
Authors: Huré Jean-Marc
Published: March 2014

Current layered accretion models neglect the properties of the “dead zone”. However, as argued here from simple considerations, the thickness of this zone is a critical quantity when the disc is in hydrostatic equilibrium. It controls not only the structure of the superficial, active layers, but also the mid-plane density and the total disc mass, and should therefore be introduced in models of that kind, steady or not. But in the absence of intrinsic heating, the dead zone must have a tiny size which, given the non-stationary and turbulent character of the global flow, makes very likely its mixing together with the two active layers.
Superhumps of CC Cancri Revisited
Authors: Kato Taichi , Uemura Makoto , Ishioka Ryoko , Pietz Jochen
Published: March 2014

We observed the 2001 November superoutburst of CC Cnc. This observation represents the first detailed coverage of a superoutburst of this object. The best-determined mean superhump period is $0.075518 \pm 0.000018 \,\mathrm{d}$, which is 2.7% longer than the reported orbital period. This fractional superhump excess is a quite typical value for a normal SU UMa-type dwarf nova, excluding the previously raised possibility that CC Cnc may have an anomalously large fractional superhump excess. During the superoutburst plateau, the object showed a decrease of the superhump period at $\dot{P}/P =-10.2 \pm 1.3 \times 10^{-5}$, which is one of the largest negative period derivatives known in all SU UMa-type dwarf novae.
Photometric Study of KR Aurigae during the High State in 2001
Authors: Kato Taichi , Ishioka Ryoko , Uemura Makoto
Published: March 2014

We photometrically observed the VY Scl-type cataclysmic variable KR Aurigae after its final rise from a fading episode in 2000–2001. A time-resolved observation revealed that the light curve is dominated by a persistent short-term variation with time-scales of minutes to tens of minutes. On some nights, quasi-periodic variations with periods of 10–15 min were observed. No coherent variation was detected. The power spectral density of the variation has a power-law component ($f^{-1.63}$). The temporal properties of the short-term variations in KR Aur present additional support for the possibility that flickering in CVs may be better understood as the result of a self-organized critical state, as in black-hole candidates. The light curve lacks “superhump”-type signals, which are relatively frequently seen in VY Scl-type systems and which are suggested to arise from a tidal instability of the accretion disk induced by changing mass-transfer rates. The present observation suggests a borderline of superhump excitation in VY Scl-type stars between mass ratios of $q = 0.43$ (MV Lyr) and $q = 0.60$ (KR Aur).
Subaru/HDS Study of the Extremely Metal-Poor Star CS 29498-043: Abundance Analysis Details and Comparison with Other Carbon-Rich Objects
Authors: Aoki Wako , Norris John E. , Ryan Sean G. , Beers Timothy C. , Ando Hiroyasu
Published: March 2014

We report on the details of an abundance study using the Subaru Telescope High Dispersion Spectrograph for the extremely metal-poor ($[\mathrm{Fe/H}] =-3.75$) star CS 29498-043, whose overabundances of C, N, Mg, and Si were reported in our previous work. The effect of the large overabundance of Mg found in this object on the stellar atmosphere is included in the abundance analysis. We also performed a similar analysis for the other eight carbon-rich, metal-poor ($-2.7 < [\mathrm{Fe/H}] <-1.9$) stars with excesses of $s$-process elements, and for the carbon-rich object CS 22957-027 which shows no excess of neutron-capture elements. Neutron-capture elements in CS 29498-043, as well as CS 22949-037 which is also known to have large excesses of C, N, Mg, and Si, do not show any overabundance. This fact clearly distinguishes these two stars from other carbon-rich objects with excesses of $s$-process elements. The abundances of Mg, Al, and Si in CS 29498-043 and CS 22949-037 are significantly higher than those in other carbon-rich objects and non-carbon-rich stars with similar metallicities. The abundance nature of these two stars suggests the existence of a class of extremely metal-poor stars with large excesses of C, N, Mg, Al, and Si, which presumably originate from supernovae in which relatively little material escaped from the iron core.
Long-Term X-Ray Variability of Quasars in the Lockman Hole Field Observed with ROSAT
Authors: Ezoe Yu-ichiro , Iyomoto Naoko , Makishima Kazuo , Hasinger Günter
Published: March 2014

An improved method has been utilized to estimate the X-ray power spectral densities (PSD) and the variation time scales of three quasars in the Lockman Hole field. Five archival ROSAT PSPC data covering a two-year range were analyzed. To estimate PSD from sparse and unevenly-sampled lightcurves, a forward-method approach with extensive Monte Carlo simulations was adopted. A broken power-law type PSD with a constant Poisson noise component was assumed with a break frequency, $f_\mathrm{b}$. Then, assuming the PSD slope, $\alpha$, to be $-2 < \alpha <-1, 1/ f_\mathrm{b}$ was constrained as $\gtrsim$ 25 days for one object, while the constraints on the other two objects were very weak. The long-time scale of the one object is consistent with the view that luminous AGNs host massive black holes.
Optical Imaging of the Radiant Points of Leonids during the 2001 Storm with the 105 cm Kiso Schmidt Telescope
Authors: Nishiura Shingo , Ohnishi Kouji , Dobashi Kazuhito , Watanabe Jun-ichi , Miyata Takashi , Nakada Yoshikazu
Published: March 2014

We report on the results of CCD imaging of the radiant points of Leonids with the 105 cm Kiso Schmidt telescope during its storm in 2001. The center coordinates of the observed field were $\alpha(\mathrm{J}2000.0) = {10{}^{\mathrm {h}}17{}^{\mathrm {m}}02\rlap {.}{}^{\mathrm {s}}4}$ and $\delta(\mathrm{J}2000.0) = + {21{}^{\mathrm {\circ }}37{}^{\mathrm {\prime }}48\rlap {.}{}^{\mathrm {\prime \prime }}0}$, corresponding to the center position between the two radiant points originating from dust trails created by the 1699 and 1866 returns of the Comet 55P/Tempel–Tuttle (McNaught, Asher 2001; WGN, 29, 156). Six CCD images having a field of view of ${51\rlap {.}{}^{\mathrm {\prime }}2} \times {51\rlap {.}{}^{\mathrm {\prime }}2}$ were obtained successively from 16h 58 m to 18h 28 m on November 18 (UT) in order to cover the two expected peaks of activity of the distinct radiant points. A limiting surface brightness of $25.93 \,\mathrm{mag} \,\mathrm{arcsec}^{-2}$, i.e., the $1\,\sigma$ noise level of the sky background, was achieved in each image. As a result, we detected only one faint Leonid meteor which most likely originated from a dust trail created by the 1866 return. The integrated total magnitude of the meteor is $m_{V}=18.34\pm 0.34 \,\mathrm{mag}$ on the image. Assuming a duration time of 0.1–1 s, we estimate the magnitude at the maximum luminosity of this meteor to be $9.70\pm 1.59 \,\mathrm{mag}$. This corresponds to a photometric mass of $(2.65^{+13.5}_{-2.22})\times 10^{-10} \,\mathrm{kg}$, which makes this meteor one of the faintest and smallest Leonids detected so far.
Revision of the Selection Function of the Optical Redshift Survey Using the Sloan Digital Sky Survey Early Data Release: Toward an Accurate Estimate of the Source Number Density of Ultra-High Energy Cosmic Rays
Authors: Yoshiguchi Hiroyuki , Nagataki Shigehiro , Sato Katsuhiko , Ohama Nobuyuki , Okamura Sadanori
Published: March 2014

If Ultra-High Energy Cosmic Rays (UHECRs) originate from nearby galaxies, modeling of the distribution of nearby galaxies is important for an accurate estimate of the source number density of UHECRs. We investigate the uncertainty of the selection function of the Optical Redshift Survey (ORS), which we use to construct a source model of UHECRs. The investigation is based on a comparison of the number counts of ORS galaxies with those of the Sloan Digital Sky Survey (SDSS) Early Data Release (EDR). We carefully count galaxies of the same absolute magnitude bin from two samples. We find a slight systematic overestimate of the ORS counts outside $5000 \,\mathrm{km} \,\mathrm{s}^{-1}$ by about a factor of 2, and revise the selection function of the ORS. The revision should be taken into account in any future analysis of the source number density of UHECRs based on the ORS. Using the revised selection function, we determined the global structure of the Local Supercluster (LSC) with a source model of UHECRs consisting of a uniform spherical halo and an exponential disk. We find that the revision is insignificant in terms of the structure of the LSC. However, the revised selection function will be useful for other studies, such as those involving a peculiar velocity and the correlation function.
Radiation Properties of an Accretion Disk with a Non-Zero Torque on Its Inner Edge
Authors: Cao Xinwu , Xu Ya-Di
Published: March 2014

The structure of the inner edge of the accretion disk around a black hole can be altered, if the matter inside the marginally stable orbit is magnetically connected to the disk. In this case, a non-zero torque is exerted on its inner edge, and the accretion efficiency, $\epsilon$, can be much higher than that in the standard accretion-disk model. We explored the radiation properties of an accretion disk at its sonic point around a black hole with a time-steady torque exerted on the inner edge of the disk. The local structure of the accretion flow at the sonic point was investigated in the frame of general relativity. It was found that the accretion flow would be optically thin at its sonic point for most cases, if the additional accretion efficiency $\delta\epsilon$ caused by the torque is as high as $\sim 10\%$. The results imply that a variable torque may trigger transitions of the flow between different accretion types.
Damping and Frequencies of Non-Axisymmetric Trapped g-Mode Oscillations
Authors: Kato Shoji
Published: March 2014

The trapping of non-axisymmetric $g$-mode oscillations in relativistic disks are examined both by a WKB method and by a method of examining the energy flow through the corotation radius. The former is a reexamination of a previous paper to correct an error in the analyses. Both analyses show that the trapped $g$-mode oscillations are damping. We further examine the frequencies and the trapped regions of these oscillations. The fundamental mode and the first overtone are trapped in the innermost region of disks with a moderate ratio of frequencies. They are possible candidates of observed kHz quasi-periodic oscillations.
FTS Measurements of Submillimeter-Wave Atmospheric Opacity at Pampa la Bola: III. Water Vapor, Liquid Water, and 183 GHz Water Vapor Line Opacities
Authors: Matsushita Satoki , Matsuo Hiroshi
Published: March 2014

Further analysis has been made on the millimeter- and submillimeter-wave (100–1600 GHz or 3 mm-188$\, {\mu \mathrm {m}}$) atmospheric opacity data taken with the Fourier Transform Spectrometer (FTS) at Pampa la Bola, 4800 m above the sea level in northern Chile, which is the site of the Atacama Large Millimeter/submillimeter Array (ALMA). Time-sequence plots of millimeter- and submillimeter-wave opacities show similar variations to each other, except for during the periods with liquid water (fog or clouds) in the atmosphere. Using millimeter- and submillimeter-wave opacity correlations under two conditions, which are affected and not affected by liquid water, we succeeded to separate the measured opacity into water vapor and liquid water opacity components. The water vapor opacity shows a good correlation with the 183 GHz water vapor line opacity, which is also covered in the measured spectra. On the other hand, the liquid water opacity and the 183 GHz line opacity show no correlation. Since only the water vapor component is expected to affect the phase of interferometers significantly, and the submillimeter-wave opacity is less affected by the liquid water component, it may be possible to use the submillimeter-wave opacity for a phase correction of submillimeter interferometers.
Spectral Energy Distributions of Dusty Galaxies
Authors: Takagi Toshinobu , Vansevičius Vladas , Arimoto Nobuo
Published: March 2014

We present an SED model of dusty galaxies, in which the equations of radiative transfer were solved by assuming spherical symmetry. The temperature fluctuation of very small dust particles was calculated consistently with the radiative transfer. The adopted dust model consisted of graphite and silicate grains and PAHs, whose relative fractions were determined for each MW, LMC, and SMC-type extinction curve. This model allowed us to derive the intrinsic SEDs of stellar populations embedded in dusty ISM, which are very important indicators for the age of stellar populations. Therefore, the evolutionary phase of starburst galaxies which frequently have very dusty ISM can be investigated with this SED model. We showed that the SED of both Arp 220 and M 82 can be explained by the same single stellar population, despite significant differences in the SED and the infrared luminosity. The apparent difference between their SEDs is mainly caused by the difference in the optical depth. In contrast, the SED of prototypical star-forming ERO, HR 10, indicates that this galaxy is relatively old compared with Arp 220 and M 82. It has been found that, in the case of an optically-thin limit like elliptical galaxies, the optical depth cannot be inferred only from the SED, because of a degeneracy between the optical depth, galactic size, and the spatial distribution of dust; the latter two are important for estimating the average temperature of dust grains in elliptical galaxies. SEDs can be used to constrain the spatial distribution of dust in elliptical galaxies, when the observed size of elliptical galaxies is taken into account.
A Method for the Determination of 3-D Velocity Fields of Disappearing Solar Filaments
Authors: Morimoto Taro , Kurokawa Hiroki
Published: March 2014

The 3-D velocity fields of disappearing filaments (Disparition Brusques: DBs) on the solar disk were extensively studied in order to determine their 3-D velocity fields. Applying Beckers’ cloud model to 5 DB events observed in the $\mathrm{H}\alpha$ line center and $\mathrm{H}\alpha \pm 0.8 \,$Å with the Flare Monitoring Telescope (FMT) at Hida Observatory, we developed a method to derive the complete 3-D velocity field of DBs. The line-of-sight velocity is obtained (i) by calculating the $\mathrm{H}\alpha$ line profile of the filament, and (ii) by measuring the Doppler shift which best fits to the observed temporal variations of contrasts of the filament. The tangential velocity is obtained by tracing the motions of the internal structures on the successive images. In this method, corrections for the effective filter bandwidths of the instrument, stray lights, and Doppler brightening effect are performed. We also discuss the velocity errors which arise from the intrinsic variations of the filament plasma during its activation, the fluctuations in intensities of the background chromosphere, and the choice of different forms of the spread function for estimating the stray light. It is emphasized that the calculation of three-dimensional vector trajectories of a disappearing filament with our method can enhance the quality of a space weather forecast with better certainty.
Plug-In Cryogenic System for Cartridge-Type SIS Receivers
Authors: Yokogawa Sozo , Sekimoto Yutaro , Sugimoto Masahiro , Okuda Takeshi , Sekiguchi Tomohiko , Kamba Toshiaki , Tatematsu Ken’ichi , Nishino Tetsuo , Ogawa Hideo , Kimura Kimihiro , Noda Kazufusa , Narasaki Katsuhiro
Published: March 2014

We developed a cryogenic system, which houses 3 cartridge-type superconductor-insulator-superconductor receivers for millimeter and submillimeter wavelengths. Since it was designed as a prototype receiver of the Atacama Large Millimeter/submillimeter Array (ALMA), high stability, accurate alignment, and easy handling were required. To meet these requirements, the cryogenic system included the following technologies: 1) a thermal link without screws for receiver cartridges; 2) a central support structure to reduce vacuum and gravitational deformation; 3) bellows structures to reduce mechanical vibration of the cryocooler; and 4) a 3-stage Gifford McMahon (GM) cryocooler with an He pot (temperature stabilizer) to reduce the thermal ripple. The cryostat and receiver cartridges are composed of three stages. The temperatures on the 4 K, 12 K, and 100 K stages of the cartridge are 3.5 K, 13.4 K, and 78.3 K, respectively. The thermal conductances of the thermal links showed high performances of $1.7 \,\mathrm{W} \,\mathrm{K}^{-1}$ at the 4 K stage, $5.6 \,\mathrm{W} \,\mathrm{K}^{-1}$ at the 12 K stage, and $3.3 \,\mathrm{W} \,\mathrm{K}^{-1}$ at the 100 K stage. The mechanical vibration on the 4 K stage of the cartridge was reduced to one-tenth, as small as $\approx 2 \, {\mu \mathrm {m}}$ peak-to-peak, compared to that on the 4 K coldhead of the cryocooler, $\approx 20 \, {\mu \mathrm {m}}$ peak-to-peak. The temperature ripple on the cartridge was reduced to as small as 2 mK peak-to-peak, which corresponds to one-seventh of the ripple on the 4 K coldhead with an He pot.
Mapping of the Decameter Radio Sources of Cassiopeia A Using a 100 km Range Long-Baseline Interferometer: Verification of a New Method of Phase Calibration of Interferometers
Authors: Oya Hiroshi , Iizima Masahide
Published: March 2014

A new method is proposed for detecting the phase difference of cesium frequency standards facilitated at coupling stations of an interferometer of 100 km range baselines for observations of decameter wavelength radio waves. In this method, the Earth’s rotation is utilized. That is, a time-depending variation of the phase differences of arriving radio waves from a given source forms a so-called fringe function due to the Earth’s rotation. By generating a reference fringe function corresponding to the position of a selected radio source, the signals can be detected being selected from widely and continuously distributed radio sources in the sky, when the correlation is analyzed between the generated reference fringe function and the fringe data detected by the interferometer. The feasibility of the proposed method has been verified by applying the method to observations of a 100 km range baseline interferometer for decameter wavelength radio waves at Tohoku University selecting the radio-wave sources in the Cassiopeia A supernova remnant as the objective. The results of the analyzed correlation values averaged for the observation data of 30 hr, at 22.158 MHz, are determined being scattered around average values with a distribution of less than 25%; this distribution corresponds to a phase determination error of $\pm 12^\circ$ for the cesium frequency standards of the interferometer at 10 MHz. That is, we can calibrate the phase shift of the cesium frequency standards facilitated at each member station of the interferometer system with an accuracy of $\pm 12^\circ$, which corresponds to an accuracy of $\pm 1 ''$ for determining the direction of the radio-source position in the sky in the case of 100 km range long baseline interferometer. This accuracy is, however, only possible when an integration time longer than 30 hr is applied for analyses of the fringe correlation values.
ASCA Observation of Unusually X-Ray-Hard Radio-Quiet QSO Kaz102
Authors: Takamitsu MIYAJI , Ishisaki Yoshitaka , Ueda Yoshihiro , Ogasaka Yasushi , Awaki Hisamitsu , Hayashida Kiyoshi
Published: March 2014

We observed the radio-quiet QSO Kaz102 $(z = 0.136)$ with ASCA as a part of our program for a complete spectral characterization of hard X-ray selected AGNs. We found that Kaz102 shows unusual spectral properties. A simple power-law with absorption in our Galaxy gave a satisfactory description of the spectrum. However, it showed a very hard photon index of $\Gamma \sim 1.0$ with no sign of deep absorption or a prominent spectral feature. We further explored the Compton reflection with the Fe $\mathrm{K}\alpha$ line and warm absorber models for hardening the spectra. Both gave statistically satisfactory fits. However, the Compton reflection model requires a very low metal abundance (0.03–0.07 in solar units). The warm absorber model with no direct component is preferred, and gave a very high ionization parameter of $\xi \sim 10^{2.3}$. If this is the case, the values of $\xi$, warm absorber column density, and variability over $\sim 10\;\mathrm{yr}$ may suggest that the warm absorber resides in the broad-line region and crosses the line of sight to the central X-ray source.
A New Candidate for the Dark Group of Galaxies, RX J0419 $+$0225
Authors: Kawaharada Madoka , Makishima Kazuo , Takahashi Isao , Nakazawa Kazuhiro , Matsushita Kyoko , Shimasaku Kazuhiro , Fukazawa Yasushi , Xu Haiguang
Published: March 2014

The bright extended X-ray source RX J0419$+$0225, first discovered in the ROSAT All Sky Survey and identified with an S0 galaxy NGC 1550, was observed with ASCA for 48 ks in 1999 August. The detected diffuse X-ray emission is centered at NGC 1550, whose redshift is 0.0123, extending out to at least $15'$, or $210 \,h^{-1}_{75} \,\mathrm{kpc}$, where $h_{75}$ is the Hubble constant in units of $75 \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{Mpc}^{-1}$. The X-ray surface brightness is represented by a $\beta$ model with ${\beta \simeq 0.47}$ and a core radius of $15 \pm 1 \,h^{-1}_{75} \,\mathrm{kpc}$. The temperature and 1–10 keV X-ray luminosity (up to $15'$) of this system were measured as being 1.4 keV and $4.7 \times 10^{42} \,h^{-2}_{75} \,\mathrm{erg} \,\mathrm{s}^{-1}$, respectively. There is no strong evidence of a temperature gradient. Within a radius of $210 \,h^{-1}_{75} \,\mathrm{kpc}$, the estimated total mass of the system becomes $1.5\times 10^{13} \,h^{-1}_{75} \,{{{M}_{\odot}}}$, which is typical of a galaxy group. With the optical information currently available, there are only two other faint galaxies. Including their B-band luminosity, the mass-to-light ratio of the system comes to $\sim 400 \,h_{75} \,{{{M}_{\odot}}}/{{{L}_{\odot}}}$, which is comparable to those of galaxy clusters. Therefore, RX J0419$+$0225 can be regarded as a “dark group candidate” in that it has an unusually high mass-to-light ratio for its optical luminosity. This object is one of the nearest among those ever identified as such candidates.
Period Change of Superhumps in a WZ Sge-Type Dwarf Nova, HV Virginis
Authors: Ishioka Ryoko , Kato Taichi , Uemura Makoto , Pietz Jochen , Vanmunster Tonny , Krajci Tom , Torii Ken’ichi , Tanabe Kenji , Kiyota Seiichiro , Kinugasa Kenzo , Masi Gianluca , Morikawa Koichi , Cook Lewis M. , Schmeer Patrick , Yamaoka Hitoshi
Published: March 2014

After 10 years of quiescence, HV Vir underwent a superoutburst in 2002 January. We report on time-series observations that clearly reveal the period change of ordinary superhumps during the superoutburst. We derived a mean superhump period of 0.058260 d and a positive period derivative of $7 \times 10^{-5}$. These results are in good agreement with a value obtained from the 1992 superoutburst. We also detected early superhumps, which were not clearly recognized in the past outburst, and a possible rebrightening. Both of them are common characteristics of WZ Sge-type stars.
New Results from ASCA on the Type II Bursts of the Rapid Burster (MXB 1730$-$335)
Authors: Mahasena Putra , Inoue Hajime , Asai Kazumi , Dotani Tadayasu
Published: March 2014

Type II burst properties of the Rapid Burster have been studied with the X-ray astronomy satellite ASCA. To study spectral evolutions throughout a burst cycle from the onset of a burst to the next burst, we constructed six composite burst-cycles in terms of the burst fluence, and divided each of them into seven phases. We then fitted the 42 spectra with a two-component model consisting of a blackbody (BB) component expected from the boundary layer, and a multi-color-disk (MCD) component expected from the standard disk, systematically. The results show that the luminosity of the BB component is much larger than that of the MCD component during a burst, while the two luminosities become comparable during a persistent phase. They also indicate that the innermost radius of the standard disk tends to recede outwards in the burst decay. These results suggest that although the standard disk extends close to the neutron star surface during a persistent phase, another accretion flow onto the neutron star is needed during a burst phase. We argue that an advection-dominated accretion flow (ADAF) would be a dominant flow onto the neutron star during a burst, and that a limit cycle of the accretion flow between an ADAF and a standard disk can explain the overall properties of the type II bursts.
Acceleration Method of Neighbor Search with GRAPE and Morton Ordering
Authors: Saitoh Takayuki R. , Koda Jin
Published: March 2014

We describe a new method to accelerate neighbor searches on GRAPE, i.e. a special-purpose hardware that efficiently calculates the gravitational forces and potentials in $N$-body simulations. In addition to gravitational calculations, GRAPE simultaneously constructs lists of neighbor particles that are necessary for Smoothed Particle Hydrodynamics (SPH). However, the data transfer of the neighbor lists from GRAPE to the host computer is time-consuming, and can be a bottleneck. In fact, the data transfer can take about the same time as the calculations of the force themselves. Making use of GRAPE’s special treatment of neighbor lists, we can reduce the amount of data transfer if we search neighbors in the order that the neighbor lists, constructed in a single GRAPE run, overlap each other. We find that the Morton ordering requires very low additional calculation and programming costs, and results in successful speed-up on data transfer. We show some benchmark results in the case of GRAPE-5. Typical reduction in transferred data becomes as much as 90%. This method is suitable not only for GRAPE-5, but also for GRAPE-3 and the other versions of GRAPE.
First Fringe Detection with VERA’s Dual-Beam System and Its Phase-Referencing Capability
Authors: Honma Mareki , Fujii Takahiro , Hirota Tomoya , Horiai Koji , Iwadate Kenzaburo , Jike Takaaki , Kameya Osamu , Kamohara Ryuichi , Kan-ya Yukitoshi , Kawaguchi Noriyuki , Kobayashi Hideyuki , Kuji Seisuke , Kurayama Tomoharu , Manabe Seiji , Miyaji Takeshi , Nakashima Kouichirou , Omodaka Toshihiro , Oyama Tomoaki , Sakai Satoshi , Sakakibara Sei-ichiro , Sato Katsuhisa , Sasao Tetsuo , Shibata Katsunori M. , Shimizu Rie , Suda Hiroshi , Tamura Yoshiaki , Ujihara Hideki , Yoshimura Akane
Published: March 2014

We present the results of the first dual-beam observations with VERA (VLBI Exploration of Radio Astrometry). The observations of a pair of $\mathrm{H}_2\mathrm{O}$ maser sources, W 49N and OH 43.8$-$0.1, were carried out on 2002 May 29 and July 23, and fringes of the $\mathrm{H}_2\mathrm{O}$ maser lines at 22 GHz were successfully detected. While the residual fringe phases of both sources showed rapid variations over $360^\circ$ due to the atmospheric fluctuation, the differential phase between the two sources remained constant for 1 hour with an r.m.s. of $8^\circ$, demonstrating that the atmospheric phase fluctuation was effectively removed by dual-beam phase referencing. An analysis based on the Allan standard deviation reveals that the differential phase is mostly dominated by white phase noise, and the coherence function calculated from the differential phase shows that after phase referencing the fringe visibility can be integrated for an arbitrarily long time. These results demonstrate VERA’s high capability of phase referencing, indicating that it is a promising tool for phase-referencing VLBI astrometry at $10 \,\mu\mathrm{as}$-level accuracy.
A Differential Abundance Analysis of the Wide Binary Pair HD 219542 A and B
Authors: Sadakane Kozo , Ohkubo Michiko , Honda Satoshi
Published: March 2014

The abundances of 22 elements (Li through Zr) in the A and B components of the visual pair HD 219542 were determined and compared using a differential analysis technique. Both components were found to be metal rich, $[\mathrm{Fe/H}] = +0.13$, in the brighter component (A) and $[\mathrm{Fe/H}] = +0.08$ in the fainter component (B). The abundances of three elements (Sc, Ti, and Fe) are definitely higher (by 0.05 dex) in component A than in component B. On the other hand, both components have nearly identical abundances of the light element Si. No evidence has been found for differences in the abundances for C, O, Na, Mg, Al, S, Ca, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Y, and Zr. No clear correlation has been found between the differences in the abundance between the two components and the condensation temperature ($T_\mathrm{c}$).
Variability and Beaming of GeV Gamma-Ray-Loud Blazars
Authors: Xie Guang-Zhong , Ma Li , Zhou Shu-Bai , Chen Luo-En , Xie Zhao-Hua
Published: March 2014

Considering the Klein–Nishina effects for high-energy $\gamma$-ray emissions, we derived a corrected form of the basic Elliot–Shapiro formula. Two new lower limits to the time scales of the variability expected from an accreting Schwarzschild black hole and Kerr black hole were derived, respectively. For a sample of 25 GeV $\gamma$-ray-loud blazars known to have the shortest time scales of flux variability, $t_\mathrm{min}$, we studied the corrected Elliot–Shapiro relations between $t_\mathrm{min}$ and the GeV $\gamma$-ray luminosities in both the high and low states, respectively. We observe that: (1) No sources have been observed to have GeV $\gamma$-ray luminosities in the low state above the corrected Eddington limit being produced by a Kerr black hole and a Schwarzschild black hole. (2) Only one source has been observed to have a luminosity in the high state above the corrected Eddington limit being produced by a Kerr black hole and a Schwarzschild black hole, which is a new argument for not invoking relativistic beaming models for the present EGRET observational data alone. Our conclusion is that if one considers the Klein–Nishina effect, the evidence for beamed emission from the present gamma-ray data alone is weak. Obviously, our conclusion is consistent with that of Dermer and Gehrels (1995, ApJ, 447, 103), but it is a new independent evidence.
Gamma-Ray-Bright Blazars: The Spectral Properties in X-Rays and Gamma-Rays
Authors: Dai Ben-Zhong , Zhang Li
Published: March 2014

We have studied the spectral properties in the soft X-ray (0.1–2.0 keV), hard X-ray (2.0–10.0 keV), and $\gamma$-ray energy bands for a sample of bright $\gamma$-ray ($E \gt 100 \,\mathrm{MeV}$$E \gt 100 \,\mathrm{MeV}$) blazars. In our analysis, we used the methods of weighted and un-weighted correlation analysis using a non-parametric Spearman rank test. Our results indicate: (i) there are significant anti-correlations both between the soft X-rays and $\gamma$-rays spectral shapes and between hard X-ray and $\gamma$-ray of flat spectrum radio quasars (FSRQs) and BL Lac objects; (ii) the weighted correlation analysis on spectral indices gives a positive correlation while the un-weighted analysis gives a negative correlation between the soft and hard X-ray bands, yielding contrary results. Because the weighted correlation analysis eliminates the effect of the observational errors, we may believe that the results of weighted analysis are more reliable than those of the un-weighted analysis.
A Possible Signature of Connection between Blazars and Seyfert Galaxies
Authors: Liang En-Wei
Published: March 2014

The accretion rates ($\dot{M}$) and their correlation with cosmological redshifts for a sample of blazars and Seyfert galaxies are presented. The sample includes 77 blazars (28 FSRQs, 26 LBLs, and 23 HBLs) and 60 Seyfert galaxies, of which the extended spectral energy distribution information and redshifts are available. Within the framework of accreting black holes, the accretion rates for these sources were estimated based on their bolometric luminosities. The result shows that the accretion rates are significantly different for each subclass of the blazars and Seyfert galaxies. Their averages are, respectively, 50.2, 17.0, 1.0, $0.1 \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1}$ for the FSRQs, LBLs, HBLs, and the Seyfert galaxies, exhibiting a well descending sequence of FSRQs—LBLs—HBLs—Seyfert galaxies. They are strongly correlated with the redshifts for both blazars and Seyfert galaxies. The linear correlation coefficients are 0.81 and 0.68 with a chance probability of $p < 0.0001$, respectively. A plot of $\dot{M} \hbox{--} z$ shows that the blazars and the Seyfert galaxies distribute in a distinguishable regions with a connection at $z\sim 0.7$, and almost all the sources lie in a narrow region of $z^{1.40} \leq \dot{M} \leq 250 \, z^{1.40}$, illustrating a strong correlation between the two quantities for the whole sample. The regression line is $\dot{M} = (14.5\pm 1.2) z^{1.40\pm 0.06} \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1}$ with a linear coefficient of 0.93 and a chance probability of $p < 0.0001$. These results confirm D’Elia and Cavaliere’s argument and expand this argument to Seyfert galaxies, suggesting a connection between blazars and Seyfert galaxies. This connection might imply that the two classes are on the same evolutionary sequence. Although the correlations of the data are formally solid, the conclusion may be affected by one source of considerable uncertainty at the data level, which is also discussed.
Effects of Dust in Distorted, Irradiated, and Expanding Atmospheres of Close Binary Components
Authors: Rao Mynampati Srinivasa
Published: March 2014

We studied the transfer of line radiation with dust in distorted and expanding atmospheres of close binary components. We assumed that the distortion of the atmosphere is caused by self rotation and a tidal force exerted by the presence of a secondary component. A seventh degree equation is defined to describe the distorted surface for uniform rotation. The equation of line transfer in the presence of gas and dust is solved in the comoving frame of the expanding atmosphere of the primary component in a binary system. We have considered a complete redistribution of photons in the line and that dust scatters radiation isotropically. We used a linear law of velocity of expansion so that the density varies as $r^{-3}$, where $r$ is the radius of the star, satisfying the law of conservation of mass. We noticed that considerable changes occur in line fluxes in dusty and dust-free atmospheres. The expansion of the atmosphere produces double-peak emission lines with P Cygni characteristics. These emission peaks are reduced in a dusty atmosphere.
Spectroscopic Observations of Split Comet C/2001 A2 (LINEAR)
Authors: Furusho Reiko , Kawakita Hideyo , Fujii Mitsugu , Kinugasa Kenzo , Yamamuro Tomoyasu , Takeyama Norihide
Published: March 2014

Low-dispersion spectroscopic observations of C/2001 A2 (LINEAR) were performed before and after its perihelion passage. C/2001 A2 (LINEAR) showed the first outburst late in 2001 March, and its visual magnitude increased by more than 5 mag. In addition to this outburst, three outbursts were recognized around the perihelion passage of the comet. These outbursts are thought to be associated with splitting events of the cometary nucleus. Our first observation was performed on 2001 April 4, during the first outburst. After its perihelion passage, its spectra were obtained on July 2, with its normal activity, and July 12, during an outburst. We determined the gas-to-dust ratios $[Q(\mathrm{H_2O}) / Af\rho]$, as well as gas production rate ratios of CN, $\mathrm{C}_2$, and $\mathrm{NH}_2$ relative to water $[Q(\mathrm{X}) / Q(\mathrm{H_2O})]$ for each observation. Obtained gas-to-dust ratios (26.4–26.7) showed that C/LINEAR was a gas-rich comet. Our results showed that there were no significant changes in the gas-to-dust ratio and gas production rate ratios during 3 months around perihelion passage. In comparison with other comets, there were no significant differences in the chemical composition for C/2001 A2 (LINEAR).
Bulge Formation in Late-Type Galaxies—Cuspy–vs Soft-Core Dark-Matter Density Profiles
Authors: Huang Jie-Hao , Deng Zu-Gan , Fu Yan-Ning
Published: March 2014

The dynamical evolution of super star clusters has been investigated in dark-matter halos depicted with a cuspy- or soft-core density profile. Simulations show that (1) exponential bulges with central cusps form in both cases; (2) distinctive bulge formation fractions are derived for cuspy- and soft-core profiles; (3) the masses of the formed bulges are causally connected with the masses of nuclear clusters, which are heavier in the case of a cuspy-core profile; (4) massive, nuclear star clusters possibly form with no discernible bulges at different ages in cuspy- or soft-core cases. Based on comparisons with observations, both the soft- and cuspy-core dark matter density profiles are suitable to relevant dwarf galaxies.
Radiato-Magneto-Thermal Winds from an Accretion Disk
Authors: Fukue Jun
Published: March 2014

We examine a hydrodynamical wind, which emanates from an accretion disk and is driven by thermal, magnetic, and radiation pressures, under a one-dimensional approximation along supposed streamlines. The disk gas is assumed to be isothermal, the magnetic field has only a toroidal component, and the radiation field is evaluated along the streamline. Such a disk wind is characterized by an isothermal sound speed, the Alfvén speed at the footpoint, and the strength of radiation fields. Isothermal winds can always blow even in the cold less-luminous case, and transonic winds are established, except for the perfectly cold case without thermal pressure. Beyond some critical luminosity, disk winds are always supersonic, irrespective of the thermal and magnetic pressures. We found that the terminal speed $v_\infty$ is roughly expressed as $(1/2) v_\infty^2 = (1/2) v_0^2-(1/2) (GM/ r_0) + 10.5 a_\mathrm{T}^2 + 0.7 a_\mathrm{A0}^2 + 16 \Gamma_\mathrm{eff} (GM/r_0),$ where $v_0$ is the initial velocity, $M$ the mass of the central object, $r_0$ the radius of the wind base on the disk, $a_\mathrm{T}$ the isothermal sound speed, $a_\mathrm{A0}$ the initial Alfvén speed, and $\Gamma_\mathrm{eff}$ the effective normalized luminosity, although the coefficients depend on the configuration of the streamlines.
Galaxy Structures and External Perturbations in Gravitational Lenses
Authors: Kawano Yozo , Oguri Masamune , Matsubara Takahiko , Ikeuchi Satoru
Published: March 2014

In modeling strong gravitational lens systems, one often adopts simple models, such as singular isothermal elliptical density plus lowest-order external perturbation. However, such simple models may mislead us if the real mass distribution is more complicated than that in the assumed models. In particular, assumptions on mass models are crucial in studying flux ratio anomalies that have been suggested as evidence for a cold dark-matter substructure. We reinvestigated four quadruple lens systems using power-law Fourier models, which have advantages of clear physical meanings and the applicability of a linear method, as well as a simple singular isothermal elliptical density model. We also investigated the effect of external perturbations, including a singular isothermal sphere, lowest-order expansion, and next-order expansion. We have found that the $\cos 3\theta$ terms of the primary galaxy and/or of external perturbation significantly reduce the $\chi^2$ in PG 1115$+$080 and B1422$+$231. In particular, we could reproduce the flux ratios of B1422$+$231 with next-order external perturbation assuming 5% flux uncertainties, suggesting that external perturbation cannot be described by a simple singular isothermal sphere approximation. On the other hand, we could not fit B0712$+$472 and B2045$+$265 very well even with our models, although the $\chi^2$ were reduced compared with the case of using simple models. Our results clearly demonstrate that both the primary lens galaxy and the external perturbation are often more complicated than we usually assume.
New Photometric Data of Old Open Clusters in the Anti-Galactic Center Region
Authors: Hasegawa Takashi , Malasan Hakim L. , Kawakita Hideyo , Obayashi Hitoshi , Kurabayashi Tsutomu , Nakai Tatsuji , Hyakkai Masaaki , Arimoto Nobuo
Published: March 2014

We present new photometric data for 14 galactic open clusters taken by the 65 cm telescope at Gunma Astronomical Observatory. They were in the anti-galactic center region selected from the Catalog of Open Cluster Data (Lyngå 1987). We estimated the parameters of the clusters, i.e., age, metallicity, distance, and reddening, by fitting Padova isochrones to the color–magnitude diagram. While no clusters were dated to be as old as young globular clusters, 13 clusters out of 14 are older than 1 Gyr, ranging up to $\sim 3.6 \,\mathrm{Gyr}$. Bearing in mind that out of approximately 500 clusters dated so far, only 40 clusters are older than 1 Gyr, our sample is exclusively dominated by old clusters. Four clusters were found away from the metallicity gradient curve and age–metallicity relation so far delineated. Especially, 3 metal-rich clusters in the outer disk (Berkeley 36, Biurakan 11, and Biurakan 13) provide evidence against the picture advocated by Twarog et al. (1997, AJ, 114, 2556) that there is a break in the metallicity distribution at $r_{\mathrm{GC}} = 10 \,\mathrm{kpc}$ and that the outer disk is chemically less evolved than in the inner disk.
Soft X-Ray Transients as Ultraluminous X-Ray Sources
Authors: Lee Chang-Hwan , Brown Gerald E.
Published: March 2014

We discuss the possibility that the soft X-ray transient GRS 1915$+$105 evolved from a binary similar to V4641 Sgr (XTE J1819$-$254) by conservative mass-transfer, and estimate the possible mass-transfer rates during the evolution. The results indicate that the high mass-transfer rates could explain the high luminosities in ultraluminous X-ray sources. Although the high mass-transfer rates during evolution are accompanied by high luminosities, we find that much of the transferred matter may sweeps accompanying radiation in an adiabatic inflow of super-Eddington accretion. We suggest that soft X-ray transients with evolved companions (initial companion mass $ \gt 3 \,{{{M}_{\odot}}}$), e.g. GRS 1915$+$105, can be ultraluminous X-ray sources if they are seen through their beaming axis.
Spectroscopic Diagnostics of Symbiotic Stars. II. Statistical Analyses of Highly Resolved Emission-Line Profiles
Authors: Ikeda Yuji , Tamura Shin’ichi
Published: March 2014

We obtained highly resolved spectroscopic data of 34 symbiotic stars at $\mathrm{H}\alpha$, He II $\lambda$4686, and [O III]$\lambda$5007. We analyzed the line profiles statistically to obtain clear common characteristics of the emission nebulae in symbiotic stars. We first carried out coarse analyses, which suggested differences in the line profiles between the quiescent and outburst phases. Second, we de-convolved the line profiles with multiple Gaussian components, and statistically dealt with each component in order to extract certain characteristics as a group. In the case of almost edge-on binary orbits, the relation between the characteristic velocities of the main, the broad wing, and the absorption components of $\mathrm{H}\alpha$ versus the orbital phase can be explained by the existence and interaction of stellar winds from cool and hot stars. The difference in the width of the main component of He II $\lambda$4686 between the quiescent and the outburst phases and the changes in their radial velocities with the orbital phase support the idea that $\mathrm{He}^{+\!+}$ gas would distribute around a hot star. Double-peaked profiles of [O III]$\lambda$5007 lines and their relation to the orbital phase can be explained by bi-conical flows.
Nucleosynthesis inside an Accretion Disk in a Type II Collapsar
Authors: Matsuba Ryuichi , Arai Kenzo , Fujimoto Shin-ichirou , Hashimoto Masa-aki
Published: March 2014

Taking into account the increasing mass of a central object through fall-back, we investigated nucleosynthesis inside an accretion disk formed during a core collapse of a massive star. It has been confirmed that the disk is an advection-dominated accretion flow supported by gas or radiation pressure. A sequence of ($\alpha, \gamma$) reactions take place and Fe-group elements are produced inside the disk. At the early phase of the fall-back, when O-rich materials inflow, the ejected gas contains abundant ${{54\atop} \mathrm{Fe}}$ and ${{56, 58\atop} \mathrm{Ni}}$. At the late phase the in-coming material is He-rich and the out-going gas is abundant of ${{44\atop} \mathrm{Ti}}$ as well as Fe and Ni. Provided that the processed gas outflows from the inner region up to the ejection radius, $r_\mathrm{ej}$, we find that the ejected mass of the heavy elements is not very sensitive to $r_\mathrm{ej}$, as long as we take $r_\mathrm{ej} \ge 50 \,r_\mathrm{g}$, because these elements are produced mainly in the region $20 \hbox{--} 100 \,r_\mathrm{g}$.
Reflection Component in the Hard X-Ray Emission from the Seyfert 2 Galaxy Mrk 1210
Authors: Ohno Masanori , Fukazawa Yasushi , Iyomoto Naoko
Published: March 2014

The Seyfert 2 galaxy Mrk 1210 was found to exhibit a flat hard X-ray component by ASCA, although ASCA could not distinguish whether it is an absorbed direct component or a reflected one. We then observed Mrk 1210 with BeppoSAX, and found that the X-ray spectral properties are quite different from those of ASCA, as have been confirmed with XMM-Newton; the flux is significantly higher than that in the ASCA observation, and a clear absorption cut-off appears below 5 keV. A bright hard X-ray emission is detected up to 100 keV. The reflection component is necessary to describe the BeppoSAX PDS spectrum, and represents the ASCA hard component very well. Therefore, the hard component in the ASCA spectrum is a reflected one, whose intensity is almost constant over 6 yr. This indicates that a dramatic spectral variability is attributed to a large change of the absorption column density by a factor of $>5$, rather than the variability of the nuclear emission. The change in the absorption column density means that the torus is not homogeneous, but has a blobby structure with a typical blob size of $< 0.001 \,\mathrm{pc}$.