bluuebunny/crossref_metadata_2025 huggingface dataset:
Relativistic Variable Eddington Factor
Authors: Fukue Jun
Published: March 2014

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

We calculated the radiation spectrum and its time variability of a black-hole accretion disk-corona system based on a three-dimensional magnetohydrodynamic (MHD) simulation. In explaining the spectral properties of active galactic nuclei, it is often assumed that they consist of a geometrically thin, optically thick disk and hot, optically thin corona surrounding the thin disk. As for a model of the corona, we adopted the simulation data of three-dimensional, non-radiative MHD accretion flows calculated by Y. Kato and coworkers, while for a thin disk we assumed a standard-type disk. We performed Monte-Carlo radiative transfer simulations of the corona, while taking into account the Compton scattering of soft photons from the thin disk by hot thermal electrons and coronal irradiation heating of the thin disk, which emits blackbody radiation. By adjusting the density parameter of the MHD coronal flow, we could produce emergent spectra that are consistent with those of typical Seyfert galaxies. Moreover, we found rapid time variability in the X-ray emission spectra, originating from a density fluctuation produced by a magnetorotational instability in the MHD corona. The features of reflection component including iron fluorescent line emission are also briefly discussed.
N2H+ and HC3N Observations of the Orion A Cloud
Authors: Tatematsu Ken’ichi , Kandori Ryo , Umemoto Tomofumi , Sekimoto Yutaro
Published: March 2014

The “$\int$-shaped filament” of the Orion A giant molecular cloud was mapped in N$_2$H$^+$, and its northern end, the OMC-2/3 region, was also observed in HC$_3$N and CCS. The results were compared with maps of other molecular lines and the dust continuum emission. The N$_2$H$^+$ distribution is similar to the dust continuum distribution, except for the central part of the Orion Nebula. The distribution of H$^{13}$CO$^+$ holds a resemblance to that of the dust continuum, but the N$_2$H$^+$ distribution looks more similar to the dust continuum distribution. The N-bearing molecules, N$_2$H$^+$ and NH$_3$, seem to be more intense in OMC-2, compared with the H$^{13}$CO$^+$ and CS distribution. This suggests that OMC-2 has a higher abundance of N-bearing molecules, or a higher filling factor of the quiescent gas. We identified 34 cloud cores from N$_2$H$^+$ data. Over the Orion Nebula region, the N$_2$H$^+$ linewidth is large (1.1-2.1kms$^{-1}$). In the OMC-2/3 region, it becomes moderate (0.5-1.3kms$^{-1}$), and it is smaller (0.3-1.1kms$^{-1}$) in the south of the Orion Nebula. On the other hand, the gas kinetic temperature of the quiescent cores observed in N$_2$H$^+$ is rather constant ($\sim$20K) over the $\int$-shaped filament. We detected no CCS emission in the OMC-2/3 region. In general, the N$_2$H$^+$ and HC$_3$N distribution is quite similar in the OMC-2/3 region, but we observed a displacement between N$_2$H$^+$ and HC$_3$N over a 2$\prime$ scale in OMC-3, which has a chain of Class 0-I protostars (candidates).
A New 100-GHz Band Front-End System with a Waveguide-Type Dual-Polarization Sideband-Separating SIS Receiver for the NRO 45-m Radio Telescope
Authors: Nakajima Taku , Sakai Takeshi , Asayama Shin’ichiro , Kimura Kimihiro , Kawamura Masayuki , Yonekura Yoshinori , Ogawa Hideo , Kuno Nario , Noguchi Takashi , Tsuboi Masato , Kawabe Ryohei
Published: March 2014

We developed a waveguide-type dual-polarization sideband-separating SIS receiver system of the 100-GHz band for the 45-m radio telescope at the Nobeyama Radio Observatory, Japan. This receiver is composed of an ortho-mode transducer and two sideband-separating SIS mixers, which are both based on a waveguide technique. The receiver has four intermediate frequency (IF) bands of 4.0–8.0 GHz. Over the radio frequency range of 80–120 GHz, the single-sideband receiver noise temperatures are 50–100 K, and the image rejection ratios (IRRs) are greater than 10 dB. We developed new matching optics for the telescope beam as well as new IF chains for the four IF signals. The new receiver system was installed in the telescope, and we successfully observed the12CO,13CO, and C18O emission lines simultaneously toward the Sagittarius B2 region to confirm the performance of the receiver system. The SSB noise temperature of the system, including the atmosphere, became approximately half of that of the previous receiver system. The IRRs of the two 2SB mixers were estimated from the12CO and HCO+ spectra from the W 51 giant molecular cloud, resulting in >20 dB for one polarization and >12 dB for the other polarization.
On-The-Fly Observing System of the Nobeyama 45-m and ASTE 10-m Telescopes
Authors: Sawada Tsuyoshi , Ikeda Norio , Sunada Kazuyoshi , Kuno Nario , Kamazaki Takeshi , Morita Koh-Ichiro , Kurono Yasutaka , Koura Norikazu , Abe Katsumi , Kawase Sachiko , Maekawa Jun , Horigome Osamu , Yanagisawa Kiyohiko
Published: March 2014

We have developed a spectral line On-The-Fly (OTF) observing mode for the Nobeyama Radio Observatory 45-m and the Atacama Submillimeter Telescope Experiment 10-m telescopes. Sets of digital autocorrelation spectrometers are available for OTF with heterodyne receivers mounted on the telescopes, including the focal-plane 5$\times$5 array receiver, BEARS, on the 45-m. During OTF observations, the antenna is continuously driven to cover the mapped region rapidly, resulting in a high observing efficiency and accuracy. Pointing of the antenna and readouts from the spectrometer are recorded as fast as 0.1s. In this paper we report on improvements made to the software and instruments, requirements and optimization of observing parameters, the data-reduction process, and verification of the system. It is confirmed that, using optimal parameters, the OTF is about twice as efficient as the conventional position-switch observing method.
Implication for Super-Critical Accretion Flow in the Narrow-Line Seyfert 1 Galaxy PKS 0558–504
Authors: Haba Yoshito , Terashima Yuichi , Kunieda Hideyo , Ohsuga Ken
Published: March 2014

We present results from XMM-Newton observations of the narrow-line Seyfert 1 galaxy PKS 0558$-$504. The 2-12keV X-ray spectra can be well-reproduced by a single power law with a photon index of $\sim$2.2. The extrapolation of this power law continuum into the lower energy band reveals the existence of a strong soft excess component. When we applied a multicolor disk blackbody (MCD) model to the soft excess component, we found that the observed disk temperature, $kT_{\rm in}$, is much higher than that predicted from a standard Shakura-Sunyaev accretion disk. Furthermore, when the luminosity of the soft excess component, $L_{\rm disk}$, exceeds about 5$\times$10$^{44}$ergs$^{-1}$, $kT_{\rm in}$ seems to decrease in spite of the increase of luminosity. This trend is inconsistent with the standard accretion disk. Therefore, these results strongly suggest that the standard accretion-disk picture is no longer appropriate in the nucleus of PKS 0558$-$504. From the estimated bolometric luminosity ($\sim$10$^{46}$ergs$^{-1}$) and the central mass (5$\times$10$^7M_\odot$) of the black hole, PKS 0558$-$504 may be shining at the super-Eddington luminosity. We discuss a possible origin of the soft excess component, and suggest that significant photon trapping in the disk could explain the observational results.
Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Delphini, ξ Aquilae, and HD 81688
Authors: Sato Bun’ei , Izumiura Hideyuki , Toyota Eri , Kambe Eiji , Ikoma Masahiro , Omiya Masashi , Masuda Seiji , Takeda Yoichi , Murata Daisuke , Itoh Yoichi , Ando Hiroyasu , Yoshida Michitoshi , Kokubo Eiichiro , Ida Shigeru
Published: March 2014

We report on the detection of 3 new extrasolar planets from a precise Doppler survey of G and K giants at Okayama Astrophysical Observatory. The host stars, 18 Del (G6 III), $\xi $Aql (K0 III) and HD81688 (K0 III-IV), are located in the clump region on the HR diagram with estimated masses of 2.1-2.3$M_{\odot}$. 18Del b has a minimum mass of $10.3 M_{\rm J}$ and resides in a nearly circular orbit with period of 993d, which is the longest one around evolved stars. $\xi $ Aql b and HD81688 b have minimum masses of 2.8 and 2.7$M_{\rm J}$, and reside in nearly circular orbits with periods of 137 and 184d, respectively, which are the shortest ones around evolved stars. All of the substellar companions ever discovered around intermediate-mass (1.7-3.9$M_{\odot}$) clump giants have semimajor axes larger than 0.68AU, suggesting a lack of short-period planets. Our numerical calculations suggest that Jupiter-mass planets within about 0.5AU (even up to 1AU, depending on the metallicity and adopted models) around 2-3$M_{\odot}$ stars could be engulfed by the central stars at the tip of RGB due to tidal torque from the central stars. Assuming that most of the clump giants are post-RGB stars, we can not distinguish whether the lack of short-period planets is primordial, or due to engulfment by central stars.
Incidence of High-Amplitude δ Scuti-Type Variable Stars
Authors: Lee Yong-Hwa , Kim Sungsoo S. , Shin Jihye , Lee Jiwon , Jin Ho
Published: March 2014

An order-of-magnitude estimate for the incidence of high-amplitude $\delta$ Scuti-type variable stars (HADS) in the $\delta$Scuti area of the H-R diagram was calculated. Using a model for the stellar distribution in the Milky Way, we calculated the number of stars that are expected to fall in the $\delta$Scuti area of the H-R diagram within the magnitude range and sky coverage of the ROTSE Survey for Variables I (RSV1). The incidence of the HADS phenomenon was then obtained by comparing the number of stars calculated by the model with the actual, observed number of HADS in the RSV1. We find that $\sim$0.24% of the stars that lie in the $\delta$Scuti area of the H-R diagram within the RSV1 observational limits exhibit the HADS phenomenon. This number is much lower than the incidence of low-amplitude $\delta$Scuti stars (LADS), $\gtrsim 1/3$, implying that the HADS phenomenon takes place in a very small fraction of stars and/or its duration is very short, compared to the LADS.
Toward First-Principle Simulations of Galaxy Formation: I. How Should We Choose Star-Formation Criteria in High-Resolution Simulations of Disk Galaxies?
Authors: Saitoh Takayuki R. , Daisaka Hiroshi , Kokubo Eiichiro , Makino Junichiro , Okamoto Takashi , Tomisaka Kohji , Wada Keiichi , Yoshida Naoki
Published: March 2014

We performed three-dimensional $N$-body/SPH simulations to study how mass resolution and other model parameters, such as the star-formation efficiency parameter, $C_*$ and the threshold density for star formation, $n_{\rm th}$ affect structures of the galactic gaseous/stellar disk. We employed $10^6$–$10^7$ particles to resolve a cold ($T \lt$ 100 K) and dense ($n_{\rm H} \gt$ 100 cm$^{-3}$) phase as well as diffuse, hot phases. We found that structures of the interstellar medium (ISM) and the distribution of young stars were sensitive to the assumed values of $n_{\rm th}$. High-$n_{\rm th}$ models with $n_{\rm th} =$ 100 cm$^{-3}$ yielded clumpy multi-phase features in the ISM. Young stars were distributed in a thin disk, of which the half-mass scale height was 10–30 pc. In low-$n_{\rm th}$ models with $n_{\rm th} =$ 0.1 cm$^{-3}$, which is usually employed in cosmological galaxy-formation simulations, the gas disk appears to be smoother and the stellar disk is found to be several-times thicker than the high-$n_{\rm th}$ models. A high-resolution simulation with high-$n_{\rm th}$ is necessary to reproduce the complex structure of the gas disk. The global star-formation properties of galaxies, such as the star-formation history, in low-$n_{\rm th}$ models are similar to those in high-$n_{\rm th}$ models when we tune the value of $C_*$ so that they reproduce the observed relation between the surface gas density and the surface star-formation rate density. We however emphasize that high-$n_{\rm th}$ models automatically reproduce the relation, regardless of the values of $C_*$. The ISM structure, phase distribution and distributions of young star-forming regions are quite similar in runs with different values of $C_*$. We found that the timescale of the flow from the reservoir ($n_{\rm H} \sim$ 1 cm$^{-3}$ ) to the star-forming regions ($n_{\rm H} \gtrsim 100$ cm$^{-3}$ ) is about five-times as long as the local dynamical time, and this evolution timescale is independent of the value of $C_*$. The use of a high-$n_{\rm th}$ criterion for star formation in high-resolution simulations makes numerical models fairy insensitive to the modeling of star formation.
V802 Aquilae: A Short-Period Eclipsing Binary with Magnetic Activity
Authors: Yang Yuan-Gui , Qian Sheng-Bang , Zhu Li-Ying , Liu Liang , Nakajima Kazuhiro
Published: March 2014

New CCD observations for V802 Aql were observed from 2004 to 2007, and seven light minimum timings were obtained. Using the Wilson–Devinney code, the photometric solution was deduced from $R$-band observations. The results show that the mass-ratio and the contact degree are $q=$ 0.1443$\pm$0.0059 and $f=$ 34.9%$\pm$7.6%, respectively. Comparing the parameters of the dark spot from our results with those from Samec et al., it is found that the magnetic activity of the primary component may have been migrating towards its equator from 2002 to 2005. An orbital period analysis weakly suggests that the orbital period may undergo a cyclic variation with a period of $P_{3}=$ 8.32 yr and an amplitude of $A=$ 0$^{\rm d}$.0196. The periodic oscillation of this binary may be more plausibly explained as being the result of magnetic activity cycles. Therefore, the eclipsing star V802 Aql may be coalescing via magnetic breaking.
Note on an Inversion Formula to Determine Binary Elements by Astrometry
Authors: Asada Hideki
Published: March 2014

Simplified solutions to determine binary elements by astrometry were obtained in terms of elementary functions (Asada et al. 2004, PASJ, 56, L35), and therefore require neither iterative nor numerical methods. In the framework of the simplified solution, this paper discusses the remaining two parameters of the time of periastron passage and the longitude of the ascending node in order to complete the solution. We thus clarify a difference between the simplified solution and other analytical methods.
Long-Time Simulations of Astrophysical Jets: Energy Structure and Quasi-Periodic Ejection
Authors: Ibrahim Ahmed , Shibata Kazunari
Published: March 2014

We have performed self-consistent 2.5-dimensional nonsteady MHD numerical simulations of jet formation as long as possible, including the dynamics of accretion disks. Previous simulations showed that, in the case where the calculation time of the simulations is very short as compared with the time scale of observed jets, there is no significant difference between the characteristics of the nonsteady and steady MHD simulations. Thus, we have investigated long-time evolutions of the mass-accretion rate, mass-outflow rate, jet velocity, and various energy fluxes. We found that the ejection of a jet is quasi-periodic. The period of the ejection, $T_{\rm ejection}$, is related to the time needed for the initial magnetic field, $B_0$, to be twisted to generate a toroidal filed, $T_{\rm ejection} \propto {V_{\rm A}}^{-1} \propto {B_0}^{-1} \propto {E_{\rm mg}}^{-1/2}$, where $V_{\rm A}$ is the Alfvén velocity and $E_{\rm mg}$ the initial magnetic energy. We compared our results with both the steady-state theory and the previous 2.5-dimensional nonsteady MHD simulations. We found that the time-averaged velocity of the jet, $V_{{\rm jet}, \mathrm{avg}}$, is $\sim 0.1V_{\mathrm{K}}$ and $\sim 0.1V_{{\rm jet}, \mathrm{max}}$, where $V_{\mathrm{K}}$ is the Keplerian velocity at $(r,{z})=(1,0)$ and $V_{{\rm jet},\mathrm{max}}$ the maximum velocity of the jet. Nevertheless, the characteristics of our simulations are consistent with those of the steady solution and previous short-time simulations. We found that the dependences of the time-averaged velocity and the mass-outflow rate, $\dot{M}_{{\rm w},\mathrm{avg}}$, on the initial magnetic field are approximately $V_{{\rm jet},\mathrm{avg}} \propto {B_0}^{0.3}$ and $\dot{M}_{{\rm w},\mathrm{avg}} \propto {B_0}^{0.32}$, respectively.
Frequency Correlation of QPOs Based on a Resonantly Excited Disk-Oscillation Model
Authors: Kato Shoji
Published: March 2014

In previous papers, we have proposed a model in which the high-frequency quasi-periodic oscillations (HF QPOs) observed in black-hole and neutron-star X-ray binaries are inertial-acoustic oscillations that are resonantly excited on a one-armed deformed disk by nonlinear couplings between the oscillations and the disk deformation. In this paper we show that in addition to the inertial-acoustic waves, one-armed corrugation waves are also excited in the deformed disks. They are low-frequency oscillations. We examine the frequencies and their correlations among the inertial-acoustic oscillations and the corrugation waves that are excited, in order to know whether they can describe the observed frequency correlations among kHz QPOs and low-frequency QPOs (LF QPOs) in neutron-star X-ray binaries. The results seem to well describe the observed correlations in Cir X-1, if we adopt $M=$ 1.5–2.0$M_\odot$ and $a_* \sim 0.8$, where $M$ is the mass of the central star and $a_*$ is a dimensionless spin parameter of the metric. Finally, assumptions involved in this disk-oscillation model are briefly summarized and discussed.
Late Superhumps in WZ Sge-Type Dwarf Novae
Authors: Kato Taichi , Maehara Hiroyuki , Monard Berto
Published: March 2014

We report on the detection of very stable modulations with periods unexpectedly ($\sim\;$0.5%) longer than the superhump periods during the slowly fading stage of WZ Sge-type superoutbursts in three systems: GW Lib, V455 And, and WZ Sge. The periods are naturally explained by assuming that these modulations are superhumps arising from matter near the tidal truncation radius. This finding provides additional support for the hypothetical idea concerning expansion of the accretion disk well beyond the 3:1 orbital resonance in some low mass-ratio systems. Combined with the effect of a 2:1 resonance, we explain the origin of positive period derivatives in certain short-period SU UMa-type dwarf novae.
Japanese VLBI Network Observations of SiO Masers in the M-Type Giant IRC −10414
Authors: Ueda Kosuke , Imai Hiroshi , Deguchi Shuji , Kamohara Ryuichi , Maeda Toshihisa , Matsumoto Naoko , Omodaka Toshihiro
Published: March 2014

We present two-epoch maps of SiO masers ($v=$ 1 and $v=$ 2, $J=$ 1-0) associated with the M-type star IRC$-$10414, which were obtained with the Japanese VLBI Network (JVN). The spatial and Doppler velocity distributions, and the intensity ratio of the $v=$ 1 to $v=$ 2 ($J=$ 1-0) lines have significantly changed for eight years since our previous Very Long Baseline Array (VLBA) observation. The maser proper motions revealed by these two-epoch observations with an interval of one month are quite random and too fast to be explained by ballistic motions of the maser clumps. The maser distributions seen in the present observations cannot be explained by a rotating-infalling ring model implied in the previous work. We discuss the kinematical relation between the SiO and H$_{2}$O masers in IRC$-$10414. In the present observations, the scale sizes of SiO $v=$ 1 and $v=$ 2 masers in IRC$-$10414 were roughly equal, as observed in typical Mira variables.
Statistical Properties of Stellar HO Masers− Results of Three−Year Single−Dish Observations with the VERA Iriki Telescope
Authors: Shintani Motonobu , Imai Hiroshi , Ando Kazuma , Nakashima Kouichiro , Hirota Tomoya , Inomata Noritomo , Kai Takayuki , Kameno Seiji , Kijima Masachika , Kobayashi Hideyuki , Kuroki Mina , Maeda Toshihisa , Maruyama Kenta , Matsumoto Naoko , Miyaji Takeshi , Nagayama Takumi , Nagayoshi Riiko , Nakamura Kayoko , Nakagawa Akiharu , Namikawa Daichi , Omodaka Toshihiro , Oyama Tomoaki , Sakakibara Seiichiro , Shimizu Rie , Sora Kasumi , Tsushima Miyuki , Ueda Kosuke , Ueda Yuya , Yamashita Kazuyoshi
Published: March 2014

We report on the results of monitoring observations of 242 stellar H$_2$O masers, which have been made with the Iriki 20m telescope of the VLBI Exploration of Radio Astrometry (VERA) from 2003 July to 2006 November. The present paper mainly focuses on 85 stellar H$_2$O masers that have been tightly observed with a time spacing of typically 1−2 months. In particular, 46 masers out of them have been recognized concerning their periodic flux variation and have light−curve data of stellar visual light. Thus, the present paper shows some statistical views of the observed time variability properties of stellar H$_2$O masers. We found a good correlation between a time delay of the variation in the H$_2$O maser flux with respect to that in the stellar visual light and the stellar pulsation period. The corresponding phase lags are mildly scattered, but are mainly concentrated in the range, $0.7\leq\Delta \phi\leq\;$1.5. We also measured line−of−sight velocity drifts of the individual spectral peaks of H$_2$O maser emission, which indicate radial acceleration of mass−loss outflows from the evolved stars. We discuss possible pulsation−driven shock waves that are enhanced near the stellar surface, and are propagating outwards in the circumstellar envelope.
Suzaku Observation of the Ophiuchus Galaxy Cluster: One of the Hottest Cool Core Clusters
Authors: Fujita Yutaka , Hayashida Kiyoshi , Nagai Masaaki , Inoue Susumu , Matsumoto Hironori , Okabe Nobuhiro , Reiprich Thomas H. , Sarazin Craig L. , Takizawa Motokazu
Published: March 2014

We present the analysis of a Suzaku observation of the Ophiuchus galaxy cluster. We confirmed that the cluster has a cool core. While the temperature of the intracluster medium (ICM) decreases toward the center, the metal abundance increases. Except for the core ($r\lesssim\;$50kpc), the cluster is hot ($\sim\;$9-10keV) and is almost isothermal for $r\lesssim 1$Mpc; the latter contradicts a previous study. We do not detect any variation of the redshift of the ICM in the cluster; the upper limit of the velocity difference is 3000kms$^{-1}$. The iron-line ratios in X-ray spectra indicate that the ICM has reached the ionization equilibrium state. From these results, we conclude that the Ophiuchus cluster is not a major merger cluster, but one of the hottest clusters with a cool core. We obtain the upper limit of non-thermal emission from the cluster, which is consistent with both the recent claimed detection with INTEGRAL and the recent upper limits with the Swift/BAT. If the cluster has bright non-thermal emission, as suggested by the INTEGRAL measurement, it is probably not due to a recent major cluster merger.
Variable Eddington Factor in a Relativistic Plane-Parallel Flow
Authors: Fukue Jun
Published: March 2014

We examine the Eddington factor in an optically thick, relativistic flow accelerating in the vertical direction. When the gaseous flow is radiatively accelerated and there is a velocity gradient, there also exists a density gradient. The comoving observer sees radiation coming from a closed surface where the optical depth measured from the observer is unity. Such a surface, called a one-tau photo-oval, is elongated in the flow direction. In general, the radiation intensity emitted by the photo-oval is non-uniform, and the photo-oval surface has a relative velocity with respect to the position of the comoving observer. Both effects introduce some degree of anisotropy in the radiation field observed in the comoving frame. As a result, the radiation field observed by the comoving observer becomes anisotropic, and the Eddington factor must deviate from the usual value of 1$/$3. Thus, the relativistic Eddington factor generally depends on the optical depth $\tau$ and the velocity gradient $du/d\tau$, $u$ being the four velocity. In the case of a plane-parallel vertical flow, we obtained the shape of the photo-oval and calculated the Eddington factor in the optically thick regime. We found that the Eddington factor $f$ can be well approximated by $f(\tau, \frac{du}{d\tau}) = \frac{1}{3} \exp ( \frac{1}{u} \frac{du}{d\tau} ) $. This relativistic variable Eddington factor can be used in various relativistic radiatively-driven flows.
Tropospheric Delay Calibrations for VERA
Authors: Honma Mareki , Tamura Yoshiaki , Reid Mark J.
Published: March 2014

We present techniques for the tropospheric delay calibration, which is the key to increasing the accuracy of the phase-referencing astrometry with Very Long Baseline Interferometry (VLBI). We study three methods, and make a comparison of these methods to discuss the accuracy in calibration. Our results show that all three methods can calibrate the tropospheric zenith delay within accuracy of $\sim$2cm. We also present simulations of positional errors in VLBI Exploration of Radio Astrometry (VERA) at the presence of an error in the tropospheric zenith delay, showing that parallax measurements with accuracy of 10$\mu$as can be readily achieved for sources at high declination and with small separation angles between the target Galactic maser and extragalactic position references.
Spectroscopic Confirmation of the Fifth Image of SDSS J1004+4112 and Implications for the MBH-σ* Relation at z = 0.68
Authors: Inada Naohisa , Oguri Masamune , Falco Emilio E. , Broadhurst Tom J. , Ofek Eran O. , Kochanek Christopher S. , Sharon Keren , Smith Graham P.
Published: March 2014

We present the results of deep spectroscopy for the central region of the cluster lens SDSSJ1004$+$4112 with the Subaru Telescope. A secure detection of an emission line of the faint blue stellar object (component E) near the center of the brightest cluster galaxy (G1) confirms that it is the central fifth image of the lensed quasar system. In addition, we measured the stellar velocity dispersion of G1 to be $\sigma_*=$ 352$\pm$13kms$^{-1}$. We combined these results to obtain constraints on the mass $M_{\rm BH}$ of the putative black hole (BH) at the center of the inactive galaxy G1, and hence on the $M_{\rm BH}$-$\sigma _*$ relation at the lens redshift $z_{\rm l}=$ 0.68. From detailed mass modeling, we placed an upper limit on the black hole mass, $M_{\rm BH}\lt2.1\times10^{10}M_\odot$ at the 1$\sigma$ level ($\lt3.1\times10^{10}M_\odot$ at 3$\sigma$), which is consistent with black hole masses expected from the local and redshift-evolved $M_{\rm BH}$-$\sigma _*$ relations, $M_{\rm BH}\sim 10^9$-$10^{10}M_\odot$.
Note on Artificial Deformation in Object Shapes Due to Pixelization
Authors: Hamana Takashi , Miyazaki Satoshi
Published: March 2014

We qualitatively examine the properties of artificial deformation in the shapes of objects (galaxies and stars) induced by pixelization effects (also called aliasing effects) using toy mock simulation images. Two causes of these effects have been recognized. One is a consequence of observing the continuous sky with discrete pixels, which is called “first pixelization”. The other, called “second pixelization”, is a consequence of resampling a pixelized image onto another pixel grid whose coordinates are not perfectly adjusted to the input grid. We pay special attention to the latter, because it might be a potential source of a systematic noise in weak-lensing analysis. In particular, it is found that resampling with rotation induces artificial ellipticities in object shapes having a periodic concentric-circle-shaped pattern. Our major findings are as follows: (1) The root-mean-square (RMS) of artificial ellipticities in object shapes induced by the first pixelization effect can be as large as RMS $\gtrsim$ 10$^{-2}$ if the characteristic size of the objects (e.g., the FWHM) is smaller than twice of the pixel size. However, for larger objects, it quickly becomes very small (RMS $\lesssim$ 10$^{-5}$). (2) The amplitude of shape deformation induced by the second pixelization effect depends on the object size. It also depends strongly on the interpolation scheme adopted to carry out resampling and on the grid size of the output pixels. The RMS of ellipticities in object shapes induced by the second pixelization effect can be suppressed to well below $10^{-2}$ if one adopts a proper interpolation scheme (implemented in popular image processing softwares). We also discuss the impact of pixelization effects on a weak-lensing analysis.
Slit-Modulation Imaging Method for Detecting Any Periodic Structural Change in Interferometric Data
Authors: Miyoshi Makoto
Published: March 2014

We propose a slit-modulation imaging (SMI) method, a new imaging technique for detecting shorter periodic structural changes of interferometric data. Using simulations with artificial visibility data, we show that the SMI method is highly effective in detecting periodic change patterns, of which period is shorter than the observing time span, of interferometric data.
Suzaku Wide-Band Observations of SN 1006
Authors: Bamba Aya , Fukazawa Yasushi , Hiraga Junko S. , Hughes John P. , Katagiri Hideaki , Kokubun Motohide , Koyama Katsuji , Miyata Emi , Mizuno Tsunefumi , Mori Koji , Nakajima Hiroshi , Ozaki Masanobu , Petre Rob , Takahashi Hiromitsu , Takahashi Tadayuki , Tanaka Takaaki , Terada Yukikatsu , Uchiyama Yasunobu , Watanabe Shin , Yamaguchi Hiroya
Published: March 2014

We report on the wide-band spectra of SN1006, as observed by Suzaku. Thermal and nonthermal emissions were successfully resolved thanks to the excellent spectral response of Suzaku's X-ray CCD XIS. The nonthermal emission could not be reproduced by a simple power-law model, but needed a roll-off at 5.7$\times$10$^{16}$Hz $=$ 0.23keV. The roll-off frequency is significantly higher in the northeastern rim than in the southwestern rim. We also placed the most stringent upper limit of the flux above 10keV using the Hard X-ray Detector.
Suzaku Spectroscopy of an X-Ray Reflection Nebula and a New Supernova Remnant Candidate in the SgrB1 Region
Authors: Nobukawa Masayoshi , Tsuru Takeshi Go , Takikawa Yojiro , Hyodo Yoshiaki , Inui Tatsuya , Nakajima Hiroshi , Matsumoto Hironori , Koyama Katsuji , Murakami Hiroshi , Yamauchi Shigeo
Published: March 2014

We made a 100 ks observation of the Sagittarius (Sgr) B1 region at $(l,\ b)=$ (0D.5, $-$0D.1) near to the Galactic center (GC) with the Suzaku/XIS. Emission lines of SXV, FeI, FeXXV, and FeXXVI were clearly detected in the spectrum. We found that the FeXXV and FeXXVI line emissions smoothly distribute over the SgrB1 and B2 regions connecting from the GC. This result suggests that the GC hot plasma extends at least up to the SgrB region with constant temperature. There are two diffuse X-ray sources in the observed region. One of the two (G0.42$-$0.04) is newly discovered, and exhibits a strong SXV K$\alpha $ emission line, suggesting a candidate for a supernova remnant located in the GC region. The other one (M0.51$-$0.10), having a prominent FeI K$\alpha $ emission line and a strongly absorbed continuum, is likely to be an X-ray reflection nebula. There is no near source bright enough to irradiate M0.51$-$0.10. However, the FeI K$\alpha $ emission can be explained if SgrA* was $\sim10^6$ times brighter 300years ago, the light travel time for 100 pc to M0.51$-$0.10, than it is at present.
The Symbiotic System SS73 17 Seen with Suzaku
Authors: Smith Randall K. , Mushotzky Richard , Mukai Koji , Kallman Tim , Markwardt Craig B. , Tueller Jack
Published: March 2014

We observed with Suzaku the symbiotic star SS73 17, motivated by the discovery by the INTEGRAL satellite and the Swift BAT survey that it emits hard X-rays. Our observations showed a highly-absorbed X-ray spectrum with $N_{\rm H} \gt 10^{23}$cm$^{-2}$, equivalent to $A_{V} \gt 26$, although the source has B magnitude 11.3 and is also bright in UV. The source also shows strong, narrow iron lines including fluorescent FeK as well as FeXXV and FeXXVI. The X-ray spectrum can be fit with a thermal model including an absorption component that partially covers the source. Most of the equivalent width of the iron fluorescent line in this model can be explained as a combination of reprocessing in a dense absorber plus reflection off a white dwarf surface, but it is likely that the continuum is partially seen in reflection as well. Unlike other symbiotic systems that show hard X-ray emission (CH Cyg, RT Cru, T CrB, GX1$+$4), SS73 17 is not known to have shown nova-like optical variability, X-ray flashes, or pulsations, and has always shown faint soft X-ray emission. As a result, although it is likely a white dwarf, the nature of the compact object in SS73 17 is still uncertain. SS73 17 is probably an extreme example of the recently discovered and relatively small class of hard X-ray emitting symbiotic systems.
Suzaku Observations of Hercules X-1: Measurements of the Two Cyclotron Harmonics
Authors: Enoto Teruaki , Makishima Kazuo , Terada Yukikatsu , Mihara Tatehiro , Nakazawa Kazuhiro , Ueda Tsuyoshi , Dotani Tadayasu , Kokubun Motohide , Nagase Fumiaki , Naik Sachindra , Suzuki Motoko , Nakajima Motoki , Takahashi Hiromitsu
Published: March 2014

The accretion-powered pulsar Her X-1 was observed with Suzaku twice in its main-on state, on 2005 October 5-6 and 2006 March 29-30, for a net exposure of 30.5ks and 34.4ks, respectively. In the 2005 and 2006 observations, the source was detected at an average 10-30keV intensity of 290mCrab and 230mCrab, respectively. The intrinsic pulse period was measured on both occasions at 1.23776s by HXD-PIN, after barycentric and binary corrections. The pulse phase-averaged spectra in the energy range above 10keV were well fitted by the “Negative and Positive power-law times EXponential” (NPEX) model, multiplied by a fundamental cyclotron resonance scattering feature at $\sim$36keV, which appears very significantly in the HXD-PIN data. The resonance profiles were successfully reproduced by a Lorentzian-type scattering cross section, rather than by a Gaussian-type alternative. The pulse phase-averaged HXD-GSO data, covering 50-120keV, are featureless. However, in a differential spectrum between the pulse-decay phase and off-pulse phase, the second-harmonic cyclotron resonance was detected in the GSO data at $\sim$73keV, with a depth of 1.6$_{-0.7}^{+0.9}$. This makes Her X-1 a 6th pulsar with established second-harmonic resonance. The implications of these results are briefly discussed.
Suzaku Observations of the North Polar Spur: Evidence for Nitrogen Enhancement
Authors: Miller Eric D. , Tsunemi Hiroshi , Bautz Mark W. , McCammon Dan , Fujimoto Ryuichi , Hughes John P. , Katsuda Satoru , Kokubun Motohide , Mitsuda Kazuhisa , Porter F. Scott , Takei Yoh , Tsuboi Yohko , Yamasaki Noriko Y.
Published: March 2014

We present observations of the North Polar Spur (NPS) using the X-ray Imaging Spectrometer (XIS) aboard the Suzaku X-ray satellite. The NPS is a large region of enhanced soft X-ray and radio emission projected above the plane of the Galaxy, likely produced by a series of supernovae and stellar winds from the nearby Sco-Cen OB association. The exceptional sensitivity and spectral resolution of the XIS below 1keV allow unprecedented probing of low-energy spectral lines, including CVI (0.37keV) and NVII (0.50keV), and we have detected highly-ionized nitrogen toward the NPS for the first time. For this single pointing toward the brightest 3/4keV emission ($l =$ 26°.8, $b =$$+$22°.0), the best-fit NPS emission model implies a hot ($kT \approx 0.3$keV), collisional ionization equilibrium (CIE) plasma with depleted C, O, Ne, Mg, and Fe abundances of less than 0.5solar, but an enhanced N abundance, with N$/$O $=$$(4.0^{+0.4}_{-0.5})$ times solar. The temperature and total thermal energy of the gas suggest heating by one or more supernovae, while the enhanced nitrogen abundance is best explained by enrichment from stellar material that has been processed by the CNO cycle. Due to the time required to develop AGB stars, we conclude that this N$/$O enhancement cannot be caused by the Sco-Cen OB association, but may result from a previous enrichment episode in the solar neighborhood.
Absolute Photometric Calibration of the Infrared Camera (IRC) aboard AKARI
Authors: TanabÉ Toshihiko , Sakon Itsuki , Cohen Martin , Wada Takehiko , Ita Yoshifusa , Ohyama Youichi , Oyabu Shinki , Uemizu Kazunori , Takagi Toshinobu , Ishihara Daisuke , Kim Woojung , Ueno Munetaka , Matsuhara Hideo , Onaka Takashi
Published: March 2014

The absolute photometric calibration of imaging observations with the Infrared Camera (IRC) aboard the AKARI satellite was performed by monitoring the same stars regularly and by observing a set of standard stars. By our monitoring observations, we confirmed that all channels of the IRC were stable to within 4% and that their sensitivities were constant until the liquid helium was exhausted. Using the data of these repeated observations, we evaluated the intrinsic errors as a function of the brightnesses of objects and found that the errors increase rapidly toward fainter objects. We also checked the consistency between short and long exposure times, and confirmed that the data sampling had been executed as designed. Finally, by comparing the estimated in-band flux densities and the observed data values of standard stars, we obtained conversion factors to the absolute flux densities of all the band/exposure configurations. Their absolute uncertainties are estimated to be less than 6%.
Far-Infrared Properties of Blue Compact Dwarf Galaxies Observed with AKARI/Far-Infrared Surveyor (FIS)
Authors: Hirashita Hiroyuki , Kaneda Hidehiro , Onaka Takashi , Suzuki Toyoaki
Published: March 2014

We report on the basic far-infrared (FIR) properties of eight blue compact dwarf galaxies (BCDs) observed by AKARI. We have measured the fluxes at the four FIS bands (wavelengths of 65$\mu$m, 90$\mu$m, 140$\mu$m, and 160$\mu$m). Based on these fluxes, we have estimated basic quantities of dust: dust temperature, dust mass, and total FIR luminosity. We find that the typical dust temperature of the BCD sample is systematically higher than that of normal spiral galaxies, although there is a large variety. The interstellar radiation field estimated from the dust temperature ranges up to 100-times the galactic value. This confirms the concentrated star-forming activity in BCDs. The star-formation rate can be evaluated from the FIR luminosity as 0.01-0.5$M_{\odot}$yr$^{-1}$. Combining this quantity with the gas mass taken from the literature, we have estimated the gas consumption timescales (gas mass divided by the star-formation rate), which have proved to span a wide range from 1Gyr to 100Gyr. A natural interpretation of this large variety can be provided by intermittent star-formation activity. We finally show the relation between dust-to-gas ratio and metallicity (we utilized our estimate of dust mass, and took other necessary quantities from the literature). There is a positive correlation between dust-to-gas ratio and metallicity, as expected from chemical evolution models.
The Atacama Compact Array (ACA)
Authors: Iguchi Satoru , Morita Koh-Ichiro , Sugimoto Masahiro , Vilaró Baltasar Vila , Saito Masao , Hasegawa Tetsuo , Kawabe Ryohei , Tatematsu Ken’ichi , Sakamoto Seiichi , Kiuchi Hitoshi , Okumura Sachiko K. , Kosugi George , Inatani Junji , Takakuwa Shigehisa , Iono Daisuke , Kamazaki Takeshi , Ogasawara Ryusuke , Ishiguro Masato
Published: March 2014

For realizing high fidelity of imaging with mosaicing observations, the Atacama Large Millimeter/submillimeter Array (ALMA) consists of a homogeneous array of 12 m antennas (12 m Array) and the Atacama Compact Array (ACA) in order to cover all spatial frequency Fourier components of the brightness distribution of observed sources. The array is located at an altitude site of about 5000 m with an operating wavelength range of 0.3 to 3 mm. ACA is an array composed of four 12 m dishes [TP (Total Power) Array] and twelve 7 m dishes (7 m Array). The 7 m Array has a very compact configuration to take short-baseline data corresponding to the low spatial frequency Fourier components. The 7 m Array has two configurations extended over 30-50 m to avoid shadowing at low elevation. The scientific importances and operation concepts of ACA, and the system design of ACA and its performance are presented in this paper.
Uniting the Quiescent Emission and Burst Spectra of Magnetar Candidates
Authors: Nakagawa Yujin E. , Yoshida Atsumasa , Yamaoka Kazutaka , Shibazaki Noriaki
Published: March 2014

Spectral studies of quiescent emission and bursts of magnetar candidates based on XMM-Newton, Chandra, and Swift data are presented. Spectra of both the quiescent emission and the burst for most magnetar candidates are reproduced by a photoelectrically absorbed two-blackbody function (2BB). There is a strong correlation between the lower and higher temperatures of 2BB ($kT_{\mathrm{LT}}$ and $kT_{\mathrm{HT}}$) for the magnetar candidates of which the spectra are well reproduced by 2BB. In addition, a square of radius for $kT_{\mathrm{LT}}$ ($R_{\mathrm{LT}}^2$) is well correlated with a square of radius for $kT_{\mathrm{HT}}$ ($R_{\mathrm{HT}}^2$). The ratio $kT_{\mathrm LT}/kT_{\mathrm HT}$$\approx$ 0.4 is nearly constant irrespective of the objects and/or emission types (i.e., the quiescent emission and the burst). This would imply that an emission mechanism is common among the magnetar candidates. The relation between the quiescent emission and the burst might be analogous to a relation between the solar microflare and the solar flare. Three anomalous X-ray pulsars (AXPs) (4U0142$+$614, 1RXSJ170849.0$-$400910, and 1E 2259$+$586) seem to have an excess above $\sim$7 keV, which well agrees with a nonthermal hard component discovered by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL).
A Galactic Center 50-kms$^{-1}$ Molecular Cloud with an Expanding Shell
Authors: Tsuboi Masato , Miyazaki Atsushi , Okumura Sachiko K.
Published: March 2014

We performed high-resolution observations of a Galactic Center 50-km s$^{-1}$ molecular cloud in the CS $J$$=$ 1–0 line using the Nobeyama Millimeter Array (NMA). The molecular cloud mainly has three different spatial components with large velocity widths of up to 60 kms$^{-1}$. The northwest component is located at an apparent contact point to the Sgr A east shell, and elongated along the boundary of the shell. The large velocity width of the component is responsible for interaction with the Sgr A east shell. The molecular gas distribution in CS line emission is dissimilar to that observed previously in NH$_3$ line emissions. The appearance shows presumably the area of CS line emission enhanced by shock. The central and southwest components are located just out of the Sgr A east shell and far from it, respectively. However, these components have large velocity widths. We found a well-shaped circular molecular shell with expanding motion in the 50-km s$^{-1}$ molecular cloud. This is responsible for the large velocity width. The continuum source in the expanding molecular shell has a steep spectrum in mm-wavelengths, although this was not identified in a previous 5-GHz map. This source may be an SNR with an ionized sheath. From the aspect ratio of an expanding molecular shell of 1.1, the magnetic field in/around the shell is estimated to be smaller than 100$\mu$Gauss. This weak magnetic field is consistent with on-going active star formation in the 50-km s$^{-1}$ molecular cloud. A comparison among CS line emission, low-frequency continuum, and millimeter continuum toward the 50-km s$^{-1}$ molecular cloud suggests a face-on view of the Sgr A region. The molecular cloud is located in the Sgr A halo region.
Search for Near-Infrared Pulsation of the Anomalous X-Ray Pulsar 4U 0142$+$61
Authors: Morii Mikio , Kobayashi Naoto , Kawai Nobuyuki , Terada Hiroshi , Tanaka Yasuyuki T. , Kitamoto Shunji , Shibazaki Noriaki
Published: March 2014

We have searched for pulsation of the anomalous X-ray pulsar (AXP) 4U 0142$+$61 in the $K^\prime$ band ($\lambda_{\rm eff}$$=$ 2.11$\mu$m) using the fast-readout mode of Infrared Camera and Spectrograph (IRCS) at the Subaru 8.2 m telescope. We found no significant signal at the pulse frequency expected by the precise ephemeris based on an X-ray monitoring observation with RXTE. Nonetheless, we obtained the best upper limit of 17% (90% C.L.) for the root-mean-square pulse fraction in the $K^\prime$ band. Combined with the $i^\prime$ band pulsation (Dhillon et al. 2005, MNRAS, 363, 609), the slope of the pulsed component ($F_\nu \propto \nu^\alpha$ in units of Jy) was constrained to $\alpha$$>$$-$0.87 (90% C.L.) for an interstellar extinction of $A_{V}$$=$ 3.5.
Variation of Fluxes of RR Tel Emission Lines Measured in 2000 with Respect to 1996
Authors: Kotnik-Karuza  , Friedjung Michael , Exter Katrina
Published: March 2014

The aim of this work is to make available unpublished non-Fe$^+$ emission line fluxes from optical spectra of the symbiotic nova RR Tel, which were taken in 2000, and to compare them with fluxes of the same lines from spectra taken in 1996. After leaving out blends and misidentifications, as well as the unreliable far-red and violet lines, we present the log($F_{2000}/F_{1996}$) flux ratios for identified non-Fe$^+$ lines. The mean values of log($F_{2000}/F_{1996}$) for different ionization potential ranges of the ions producing the lines are shown separately for the permitted and forbidden lines. All means show fading, which is larger in the lowest range of the ionization potential. Provisional interpretations are suggested. We also measured the values of FWHM in 2000; the previously known decrease with time of the FWHM of lines due to the same ion has continued.