bluuebunny/crossref_metadata_2025 huggingface dataset:
ASCA Temperature Maps of Three Clusters of Galaxies: Abell 1060, AWM 7, and the Centaurus Cluster
Authors: Furusho Tae , Yamasaki Noriko Y. , Ohashi Takaya , Shibata Ryo , Kagei Tomohiro , Ishisaki Yoshitaka , Kikuchi Ken’ichi , Ezawa Hajime , Ikebe Yasushi
Published: March 2014

We present two-dimensional temperature maps of three bright clusters of galaxies (Abell 1060, AWM 7, and the Centaurus cluster), based on multi-pointing observations with the ASCA GIS. The temperatures were derived from hardness ratios by taking into account the XRT response. For the Centaurus cluster, we subtracted the central cool component using the previous ASCA and ROSAT results, and the metallicity gradients observed in AWM 7 and the Centaurus cluster were included in deriving the temperatures. The intracluster medium in Abell 1060 and AWM 7 is almost isothermal from the center to the outer regions with temperatures of 3.3 and $3.9$ keV, respectively. The Centaurus cluster exhibits remarkable hot regions within about ${30{}^{\mathrm {\prime }}}$ from the cluster center, showing a temperature increase of $+0.8$ keV from the surrounding level of 3.5 keV, and the outer cool regions with lower temperatures by $-1.3$ keV. These results imply that a strong merger has occurred in the Centaurus in the recent 2–3 Gyr, and that the central cool component has survived it. In contrast, the gas in Abell 1060 was well-mixed in an early period, which probably has prevented the development of a central cool component. In AWM 7, mixing of the gas should have occurred in a period earlier than the epoch of metal enrichment.
The Radio-to-Submillimeter Flux Density Ratio of Galaxies as a Measure of Redshift
Authors: Rengarajan T. N. , Takeuchi Tsutomu T.
Published: March 2014

We re-examine the technique of determining the redshifts of galaxies from the ratio of the submillimeter-to-radio continuum flux densities based on a recently published catalog of $850\, {\mu \mathrm {m}}$ sources. We derived the expected variation of this ratio as a function of redshift incorporating the expected average luminosity and the spectral energy distribution (SED) of dust emission and the radio continuum. We find that the existing data for most of the high redshift ($z \gtrsim 1$) sources correspond to our new calculation. Amongst the well-identified sources, there is none with an index significantly higher than predicted. Sources which have an index lower than predicted are either within the error zone or much lower, the latter presumably having AGN-dominated radio-continuum emission. We find the median redshift to be $\sim 2$, which is consistent with that deduced by previous work ($\sim 3$) within the error. We also discuss the various systematic effects that can affect the accuracy of the redshift estimate. We examine other methods of redshift estimation, like photometric ratio in the submillimeter and locating the peak of the SED in the rest system of the objects. We conclude that while the various methods are helpful in identifying high-redshift objects and making a crude estimate of the redshift, they are not, at present, accurate enough for a detailed study of redshift distribution of the submillimeter galaxies.
The Spectral Energy Distributions of Blazars and the Connections among XBLs, RBLs, and OVV Quasars
Authors: Xie Guangzhong , Dai Benzhong , Liang Enwei , Ma Li , Jiang Zejun
Published: March 2014

In this paper, we introduce two composite spectral indices, $\alpha_{\mathrm{xox}}=\alpha_{\mathrm{ox}}- \alpha_{\rm {x}}$ and $\alpha_{\mathrm{oro}}=\alpha_{\mathrm{or}}- \alpha_{\mathrm{o}}$. In the composite color–color ($\alpha_{\mathrm{xox}}$–$\alpha_{\mathrm{oro}}$) diagram, there are three regions: (1) For XBLs and XBL-like RBLs, the values of $\alpha_{\mathrm{xox}}$ is in the range of $-1.0$ -$0.0$; (2) For RBLs, $\alpha_{\mathrm{xox}}$ is in 0.0–1.5, and $\alpha_{\mathrm{oro}} \lt -0.75$; (3) For OVV quasars, $\alpha_{\mathrm{xox}}$ is in 0.0–1.5 and the $\alpha_{\mathrm{oro}} \gt-0.75 \alpha_{\mathrm{oro}} \gt-0.75$. Our results support the conclusion that RBLs are intermediate between XBLs and OVV quasars, which has been given by Sambruna et al. (1996, AAA 65.159.120). On the other hand, based on the idea that a group of extragalactic objects which can be regarded as a category with similar physical properties must fit the same relation, using the HST new observational data, we found that there is a strong correlation between the apparent magnitude of the host galaxies and log $z$ for all BL Lac objects (XBLs + RBLs), but OVV quasars lie about 4 magnitude above the Hubble line of 86 BL Lacs. This implies that all XBL-like and XBLs belong to a single category with similar physical properties, while OVV quasars and BL Lacs belong to different populations.
H2 Formation in Low-Metallicity Galaxies
Authors: Kamaya Hideyuki , Hirashita Hiroyuki
Published: March 2014

A possible formation mechanism of hydrogen molecules on a galactic scale is examined. We are interested especially in the role of hydrogen molecules for the formation and evolution of primordial galaxies. Thus, the formation process of hydrogen molecules in a very low-metallicity galaxy (I Zw 18; the most typical metal-deficient galaxy) is studied. Adopting a recent observational result of the absorption lines of hydrogen molecules in I Zw 18, we obtain the upper limit for the ionization degree in the case where hydrogen molecules can form via the $\mathrm{H}^{-}$-process, although they are generally believed to form on the surface of dust grains. Furthermore, we present a critical ionization degree, above which the $\mathrm{H}^{-}$-process can be dominant over the formation process on the surface of grains. Interestingly, this critical ionization degree is comparable to the upper limit of the ionization degree for I Zw 18. For determining the formation process of hydrogen molecules, future observational facilities can be useful. Thus, we examine the detectability in some wavelengths for metal-deficient galaxies. According to our estimate, the near-infrared line emission of hydrogen molecules is observable at the level of $10\,\mu\mathrm{Jy}$, the free–free radio emission is at the level of mJy, and the far-infrared emission from the dust on which hydrogen molecules form can also be detected at the 10-mJy level with its temperature of 16 K. The near-infrared line and the far-infrared continuum are feasible for ASTRO-F observations.
Nucleosynthesis inside Supernova-Driven Supercritical Accretion Disks
Authors: Fujimoto Shin-ichirou , Arai Kenzo , Matsuba Ryuichi , Hashimoto Masa-aki , Koike Osamu , Mineshige Shin
Published: March 2014

We have investigated nucleosynthesis in a supercritical accretion disk around a compact object of $1.4\,{{{M}_{\odot}}}$, using the self-similar solution of an optically thick advection dominated flow. Supercritical accretion is expected to occur in a supernova with fallback material accreting onto a new-born compact object. It has been found that appreciable nuclear reactions take place even for a reasonable value of the viscosity parameter, $\alpha_{\mathrm{vis}} \simeq 0.01$, when the accretion rate $\dot{m} = \dot{M}c^2/(16 L_{\mathrm{Edd}}) \gt 10^5$, where $L_{\mathrm{Edd}}$ is the Eddington luminosity. If $\dot{m} \ge 4 \times 10^6$, all heavy elements are destroyed to ${{4\atop} \mathrm{He}}$ through photodisintegrations at the inner part of the disk. Even ${{4\atop} \mathrm{He}}$ is also disintegrated to protons and neutrons near the inner edge when $\dot{m} \ge 2 \times 10^7$. If the fallback matter of the supernova explosion has the composition of a helium-rich layer of the progenitor, a considerable amount of ${{44\atop} \mathrm{Ti}}$ could be ejected via a jet from the disk.
Kashima 34-m Water Maser Survey of Late-Type Stars
Authors: Takaba Hiroshi , Iwata Takahiro , Miyaji Takeshi , Deguchi Shuji
Published: March 2014

This paper presents new results of a water maser survey of late-type stellar objects at 22.235 GHz with the Kashima 34-m radio telescope. We have detected 179 out of 643 observed sources, including 32 new detections. The sources were selected in terms of the IRAS flux density and colors of late-type stars, involving optically observable Mira/semiregular variables, IRC objects, OH/IR sources and protoplanetary nebulae. We found the highest $\mathrm{H}_{2}\mathrm{O}$ detection rate for the type of stars with a thin dust envelope (Mira/semiregular variables) among other types of sources. This is attributed to the smaller distances to such stars in the sample. The velocity spread of the $\mathrm{H}_{2}\mathrm{O}$ maser profile has an increasing tendency with the IRAS color, though it becomes more difficult to access this color dependence beyond an edge of the transition of the (oxygen-rich) Asymptotic Giant Branch stars to protoplanetary nebulae in the two-color diagram.
Absorption Measurement of Hydrogen Molecules in the Early Universe
Authors: Shibai Hiroshi , Takeuchi Tsutomu T. , Rengarajan T. N. , Hirashita Hiroyuki
Published: March 2014

We investigate the observability of hydrogen molecules in absorption. The absorption efficiency of hydrogen molecules becomes comparable with, or larger than, that of the dust grains in the metal-poor condition expected in the early Universe. If we can use bright infrared continuum sources behind the molecular-gas clouds, the absorption measurement of the hydrogen molecules could be an important technique to explore the primordial gas clouds that are contracting into first-generation objects.
How Evolved are the Mass Donor Stars in Cataclysmic Variables?
Authors: Howell Steve B.
Published: March 2014

Recent spectroscopic observations have identified several cataclysmic variables non-solar metal abundances. We present theoretical models which examine the level of core evolution expected for CV secondaries prior to contact. Our results indicate that few secondary stars evolve past 10% of their main sequence lifetime prior to the initiation of mass transfer; a result of which is in agreement with present day observations. Thus, the non-solar metal abundances observed must be due to nuclear burning by-products accreted by the secondary star during common envelope sweeping prior to initial contact or ejecta collected during classical nova outbursts.
Improvement of the Triple-Encounter Criterion
Authors: Umehara Hiroaki , Tanikawa Kiyotaka
Published: March 2014

The criterion for classifying triple encounters has been improved in order to cover wide triple-encounters compared to those in virial equilibrium. Its validity was confirmed by systematic numerical observations of orbits in the three-body problem with zero initial-velocities and equal masses.
First Subaru Observations of Sub-km Main-Belt Asteroids
Authors: Yoshida Fumi , Nakamura Tsuko , Fuse Tetsuharu , Komiyama Yutaka , Yagi Masafumi , Miyazaki Satoshi , Okamura Sadanori , Ouchi Masami , Miyazaki Masayuki
Published: March 2014

We report on the first observations of sub-km main-belt asteroids (MBAs) obtained with the prime-focus mosaic CCD camera for the Subaru telescope. We detected 27 moving objects in a single image of the sky (field of view: $ {27{}^{\mathrm {\prime }}} \times {27{}^{\mathrm {\prime }}}$), whose location was $ {41{}^{\mathrm {\circ }}}$ off opposition. From their positions and projected motions on the sky, all of the detected objects were found to be new and consistent with the characteristic of MBAs. The V-magnitudes of the discovered asteroids range approximately from 19 to 24. Under some simple, but reasonable, assumptions, we estimated the cumulative size distribution for the asteroids. This is the first statistics for sub-km MBAs (the minimum diameter corresponds to about 0.6km). It is found that the slope of the cumulative size distribution for the observed asteroids is 1.0 with an error of about 0.3. We note that our slope is fairly smaller than that obtained in the past observational surveys for asteroids larger than a few kilometers ($ \sim1.75$).
A Large-Scale CO Mapping of the Central Region of W 51
Authors: Okumura Shin-ichiro , Miyawaki Ryosuke , Sorai Kazuo , Yamashita Takuya , Hasegawa Tetsuo
Published: March 2014

We present a high-resolution (16$^{\prime\prime}$) ${{13\atop} \mathrm{CO}}$ ($J= 1$−$0$) map of the central region of W 51. We observed an area of about ${15\rlap {.}{}^{\mathrm {\prime }}3}\times {16\rlap {.}{}^{\mathrm {\prime }}7}$, which covers the entire region of G49.5–0.4, the brightest source in the W 51 region. Four discrete molecular clouds were identified toward G49.5–0.4, and evidence of cloud–cloud collisions was found. We speculate that a “pileup” of three molecular clouds resulted in a burst of massive star formation in G49.5–0.4.
Slim Disk: Viscosity Prescriptions and Observational Implications
Authors: Watarai Ken-ya , Mineshige Shin
Published: March 2014

We examine how different viscosity prescriptions and magnitudes affect the structure of the slim disk. Unlike the case with a standard disk, radiation from the slim disk is influenced by the viscosity parameter, $\alpha$, in such a way that the estimated maximum effective temperature of the disk slightly increases as $\alpha$ increases. This is because the larger is $\alpha$, the larger does the accretion velocity become and, hence, the more enhanced does the advective energy transport become, which means less efficient radiative cooling and thus higher temperatures. Furthermore, we checked different viscosity prescriptions with the form of the viscous stress tensor of $t_{r \varphi} =-\alpha \beta^{\mu}p_\mathrm{total}$, where $\beta$ is the ratio of the gas pressure to the total pressure, and $\mu$ is a parameter ($0 \le \mu \le 1$). In contrast with the case with $\mu=0$, which shows significant decrease in the inner-edge radius and the flattering of the effective temperature profile at high luminosities, for large $\mu$, say $\mu \sim 0.5$, neither of the inner-edge of the disk nor temperature profiles does not appreciably change even at the Eddington luminosity. We can rule out a case with large $\mu~(\sim 0.5)$, since it would not be able to produce a drop in the inner-edge radius of an increase in the luminosity, as was observed in an ultraluminous X-ray source, IC 342, source 1
Trapping of Non-Axisymmetric $g$-Mode Oscillations in Thin Relativistic Disks and kHz QPOs
Authors: Kato Shoji
Published: March 2014

We suggest that in the inner part of geometrically thin relativistic disks there are trapped non-axisymmetric $g$-mode oscillations which are excited by a corotation resonance. These oscillation modes would be the cause of quasi-periodic kHz oscillations observed in some low-mass X-ray sources.
The Most Massive C18O Molecular Complex in Centaurus and Star Formation Therein
Authors: Saito Hiro , Mizuno Norikazu , Morigichi Yoshiaki , Matsunaga Ken’ichi , Onishi Toshikazu , Mizuno Akira , Fukui Yasuo
Published: March 2014

New observations of the 12CO, 13CO, and $\mathrm{C}{{18\atop} \mathrm{O}}$ ($J = 1 \hbox{--} 0$) emission lines have been extensively made toward the Centaurus tangential region $({308\rlap {.}{}^{\mathrm {\circ }}5} \le l \le {310\rlap {.}{}^{\mathrm {\circ }}5}$ and $- {1\rlap {.}{}^{\mathrm {\circ }}0} \le b \le {1\rlap {.}{}^{\mathrm {\circ }}0})$ using the “NANTEN”telescope. These observations have revealed a massive molecular complex in $\mathrm{C}{{18\atop} \mathrm{O}}$ of $\sim 1.8 \times 10^{5}\,{{{M}_{\odot}}}$, the most massive one observed in $\mathrm{C}{{18\atop} \mathrm{O}}$ to date in the Galaxy. This complex is highly elongated with a size of $\sim 80 \,\mathrm{pc} \times \sim 25 \,\mathrm{pc}$ at $309^{\circ} \le l \le {309\rlap {.}{}^{\mathrm {\circ }}5}$ and $- {0\rlap {.}{}^{\mathrm {\circ }}9} \le b \le {0\rlap {.}{}^{\mathrm {\circ }}4}$, including 35 dense molecular clumps whose mass ranges from $4.7 \times 10^{2} \,{{{M}_{\odot}}}$ to $3.4 \times 10^{4} \,{{{M}_{\odot}}}$. Twenty-seven of the 35 clumps are associated with IRAS point sources whose luminosity ranges from $7.2 \times 10^{2} \,{{{L}_{\odot}}}$ to $3.6 \times 10^{5} \,{{{L}_{\odot}}}$. We find that the luminosity of the candidate protostellar IRAS sources is well correlated with the molecular line width, as fitted by a power law, $\log (L_\mathrm{IRAS}) = 1.1 + (9.2 \pm 0.6) \log (\Delta V)$. This suggests that the mass of the formed stars is determined by the internal velocity dispersion of the dense cores. A comparison with an H I distribution shows that the molecular gas forms a ring-like structure inside an H I hole of $\sim 55 \hbox{--} 70 \;\mathrm{pc}$ radius. Since the H I gas surrounding the hole shows a signature of expansion at several $\mathrm{km} \,\mathrm{s}^{-1}$, we suggest that the H I hole exhibits a shell created by some explosive events, like supernovae, during the last $\sim (6 \hbox{--} 8) \times 10^{6} \,\mathrm{yr}$. The ring-like structure of the CO distribution may be found due to the interaction between the expanding shell and the interstellar medium, leading to a trigger of massive star formation.
Galaxy Population in a Cluster of Galaxies around the Radio Galaxy 3C 324 at $z=1.2$
Authors: Nakata Fumiaki , Kajisawa Masaru , Yamada Toru , Kodama Tadayuki , Shimasaku Kazuhiro , Tanaka Ichi , Doi Mamoru , Furusawa Hisanori , Hamabe Masaru , Iye Masanori , Kimura Masahiko , Komiyama Yutaka , Miyazaki Satoshi , Okamura Sadanori , Ouchi Masami , Sasaki Toshiyuki , Sekiguchi Maki , Yagi Masafumi , Yasuda Naoki
Published: March 2014

We discuss the properties of galaxies around the radio galaxy 3C 324 at $z=1.2$ based on $BVRIK^\prime$ multi-band imaging data. We have applied a photometric-redshift technique to objects in the 3C 324 field, and identified 35 objects as plausible cluster members. We have found that red and luminous members are concentrated in a small region enclosed by a circle of 40$^\prime$ radius (0.33Mpc at $z=1.2$ for $\Omega_0 = 0.3, \lambda_0 = 0.7, H_0 = 70 \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{Mpc}^{-1}$ cosmology) from the 3C 324 galaxy. The 3C 324 cluster is probably much more compact in size compared with the local clusters. We constructed a $K^\prime$-band luminosity function of the cluster members and fitted a Schechter function, and found the characteristic magnitude to be $K^{\ast\prime}_\mathrm{AB} = 20.2 \pm 0.6$. This value is consistent with the extrapolation of the pure passive evolution seen for $z \lt 1$ clusters. We have identified eight bright galaxies which form a red color–magnitude sequence. The slope of the sequence is consistent with the passive evolution model down to $K^{\prime}_\mathrm{AB} \lt 22$; we also found that there is no clear age variation in these bright red galaxies. However, seven out of these eight galaxies exhibit a significant excess in the rest UV light with respect to the passive evolution model. This may suggest that the massive early-type galaxies in this high-redshift cluster are still forming stars to some extent. We have confirmed a truncation of the color–magnitude sequence at $K^{\prime}_\mathrm{AB}\sim22$; faint passively-evolving galaxies may not yet be present in this cluster at $z \sim 1.2$. The overall color distribution of the cluster members, selected by the photometric redshift technique, is found to be very broad. We derived the fraction of blue galaxies in this cluster following a definition of Butcher and Oemler (1984, AAA 038.160.068), and obtained $f_\mathrm{B} = 0.39 \pm 0.28$, which is higher than that for $z \lt 1$ clusters. This indicates that the star-formation activity of this cluster is, on the average, higher than that of lower redshift counterparts.
Propagation of Ultra-High Energy Cosmic Rays from Sources in the Super-Galactic Plane
Authors: Ide Yoshinori , Nagataki Shigehiro , Tsubaki Shinya , Yoshiguchi Hiroyuki , Sato Katsuhiko
Published: March 2014

We have performed detailed numerical simulations on the propagation of UHE protons in the energy range $E = (10^{19.5} \hbox{--} 10^{22.0}) \,\mathrm{eV}$ in a relatively strong extragalactic magnetic field with a strength of $B = (10 \hbox{--} 100) \,\mathrm{nG}$ within about 40Mpc. In this case, the deflection angles of UHECRs become so large that the no counterparts problem can be simply solved. As for the source distribution, we assumed that it is proportional to the number distribution of galaxies within the Greisen–Zatsepin–Kuzmin sphere. We found many clusters, meaning small-scale anisotropy, in our simulations. It has also been shown that the observed energy spectrum is well reproduced in our models without any fine-tuned parameter. We used the correlation value in order to investigate statistically the similarity between the distribution of arrival directions of UHECRs and that of galaxies. We found that each correlation value for each parameter set begins to converge when the number of detected events becomes $O(10^3)$. Since the expected number counts by the experiment of the next generation, such as TA, HiRes, Auger, and EUSO, are thought to be on the order of $10^3$, we will be able to check in the very near future whether the source distribution of UHECRs is correlated with the Super-Galactic Plane or not. Compared with the AGASA data, a significant anisotropy on the arrival directions of UHECRs is found in the analyses of the first and second harmonics. This may originate from an incompleteness of the ORS database. This problem may also be solved if the source distribution is slightly changed. For example, this problem may be solved if we assume that UHECRs come from some galaxies, such as AGNs and radio galaxies.
Multi-Phase Gas Dynamics in a Weak Barred Potential
Authors: Wada Keiichi , Koda Jin
Published: March 2014

The structure of the interstellar medium in the central kpc region of a galaxy with a weak bar-like potential was investigated while taking into account realistic cooling and heating processes and the self-gravity of the gas. Using high-resolution hydrodynamical simulations, it has been revealed that the resonant structures (e.g. smooth spiral shocks and a nuclear ring) are very different from those seen in past numerical models where simple models of the ISM, i.e. non-self-gravitating, isothermal gas, were assumed. We find that the pc-scale filaments and clumps form large-scale spirals, which resemble those seen in real galaxies. The fine structures are different between the arms and in the nuclear region. The next-generation millimeter interferometer (ALMA) may reveal the fine structures of the cold gas in nearby galaxies. We also find a large-scale anisotropy in the gas temperature, which is caused by a non-circular velocity field of the gas. The damped-orbit model based on the epicyclic approximation explains the distribution of the hot ($ \gt 10^4 \,\mathrm{K}$) and cold ($\lt 100 \,\mathrm{K}$) gases appearing alternately around the galactic center. Because of the temperature anisotropy, cold gases observed by molecular lines do not necessarily represent the real gas distribution in galaxies. Position–Velocity diagrams strongly depend on the viewing angles. As a result, the rotational velocity inferred from the P–V maps could be two-times larger or smaller than the true circular velocity.
Spectral Variations of Cyg X-1 in the Hard State Studied with ASCA Data
Authors: Takahashi Kazuki , Inoue Hajime , Dotani Tadayasu
Published: March 2014

Spectral variations of Cyg X-1 in the hard state have been studied on two time scales of about $10^{4} \,\mathrm{s}$ and 1 s using ASCA archive data. The energy spectrum was well fit by a model consisting of a multicolor blackbody expected from an optically-thick accretion disk and a broken power-law, with absorption by interstellar matter. The broken power-law component was found to change its normalization on both time scales, while keeping the spectral shape unchanged, whereas the multicolor blackbody component varies only on a time scale of $10^4 \,\mathrm{s}$. From this clear separation of the time variabilities, the two spectral components can be considered to be two real substances reflecting two respective emission processes different from each other. We found from a careful comparison of the disk parameters that the innermost radius in the hard state is a few times larger than that in the soft state, even if the uncertainty in a ratio of the observed color temperature to an effective temperature is taken into account. It is suggested that an optically-thin disk exists inside the optically-thick disk in the hard state and that the broken power-law component comes from the optically-thin inner disk.
Discovery of a Transient X-Ray Pulsar, AX J1841.0$-$0536, in the Scutum Arm Region with ASCA
Authors: Bamba Aya , Yokogawa Jun , Ueno Masaru , Koyama Katsuji , Yamauchi Shigeo
Published: March 2014

We report on the discovery of a transient X-ray pulsar, AX J1841.0$-$0536, serendipitously found in the Scutum arm region with the ASCA in two separate observations. The X-ray flux is very faint at the beginning, but exhibits two flares in the second observation. The flare flux increases by a factor 10 within only $\sim 1 \,\mathrm{hr}$. Coherent pulsations with a period of $4.7394 \pm 0.0008 \,\mathrm{s}$ were detected in the brightest flare phase. The X-ray spectra in the quiescent and flare phases were fitted with an absorbed power-law model with a photon index $\sim 1$ plus a narrow Gaussian line at the center energy of 6.4 keV. The interstellar column density of $\sim 3\times 10^{22} \,\mathrm{cm}^{-2}$ may indicate that AX J1841.0$-$0536 is located at a tangential point of the Scutum arm at $\sim 10 \,\mathrm{kpc}$ distance. The coherent pulsations, large flux variability, and the spectral shape suggest that AX J1841.0$-$0536 is a Be/X-ray binary pulsar.
HV Virginis and WZ Sge-Type Dwarf Novae
Authors: Kato Taichi , Sekine Yoshiyuki , Hirata Ryuko
Published: March 2014

A dwarf nova HV Vir was observed photometrically for eight nights during an outburst in 1992 April–May. The star showed two distinct types of periodic variation: (1) 82.20-min (0.05708d) double-humped variation with decaying amplitudes during the early stage of the outburst, and (2) 83.80-min (0.05820d) superhumps in later stages. We attributed the former to “early superhumps”, which are only seen in the earliest stage of WZ Sge-type outbursts. The superhump period and evolution of the superhumps, together with general characteristics of the light curve, make HV Vir a typical WZ Sge-type dwarf nova. HV Vir also showed a large increase of the superhump period during the superoutburst. Upon recognizing the WZ Sge-type nature of an object previously considered as a nova, we present a comprehensive list of candidates for WZ Sge-type dwarf novae and related systems.
A New Test for the Absorption Mechanism of GPS Radio Sources Using Polarization Properties
Authors: Mutoh Mutsumi , Inoue Makoto , Kameno Seiji , Asada Keiichi , Fujisawa Kenta , Uchida Yutaka
Published: March 2014

We consider the use of polarization properties as a means to discriminate between Synchrotron Self-Absorption (SSA) and Free–Free Absorption (FFA) in GHz-Peaked Spectrum (GPS) sources. The polarization position angle (PA) of synchrotron radiation at high frequencies for the optically thin regime is perpendicular to the magnetic field, whereas it is parallel to the magnetic field at low frequencies for the optically thick regime. Therefore, SSA produces a change in PA of $90^{\circ}$ across the spectral peak, while FFA does not result in such a change. We analyzed polarization data from VLA observations for six GPS sources to see if such a change in PA was present. Our results indicate that there is no significant evidence for $90^{\circ}$ change in PA across the spectral peak, suggesting that FFA is more likely than SSA for low-frequency cutoffs in these sources.
Period and Light-Curve Changes in AP Leonis
Authors: Li Lifang , Zhang Fenghui , Han Zhanwen
Published: March 2014

We present a detailed study of the period and light curve of the eclipsing binary AP Leo. We have investigated the period variation of the system in detail using a method proposed by Kalimeris et al. (1994a,b; AAA 061.117.039, AAA 062.117.142). The orbital period of the system exhibits a periodic variation which contains four components with different frequencies. Our result is very different from that of other investigators. We compared light curves obtained by other groups, and found that the light curve of the system has changed considerably. Based on an analysis, we investigated the physical mechanisms which may underlie the variations of the period and the light curve, and obtained some new results. We have concluded that the rapid light variation is probably caused by a pulsation of the common envelope, and that the mechanism causing the pulsation may be mass transfer between the two components, or its variation. In addition, we have found that the mass transfer and magnetic activity may simultaneously play an important role in the variations in the orbital period and the light curve of the system. The paper concludes with a discussion of the evolution of the system.
Spiral Molecular Front in Galaxies: Quick Transition from Atomic to Molecular Hydrogen in Spiral Arms
Authors: Hidaka Makoto , Sofue Yoshiaki
Published: March 2014

We derived a two-dimensional map of the molecular fraction, $ f_{\mathrm{mol}}$ (ratio of the molecular gas density to that of total gas), in the spiral galaxy M 51, and examined the behavior of molecular fronts (MF), where MF denotes the place where $ f_{\mathrm{mol}}$ changes drastically from nearly zero to unity, and vice versa. We showed that the MF phenomenon is not only radial, but also occurs in the azimuth direction through the spiral arms, and $ f_{\mathrm{mol}}$ changes rapidly in the arm-to-interarm transition regions. The existence of the azimuthal MF indicates that the atomic gas (H i) is quickly transformed to molecular gas ($ \mathrm{H}_2$) during passage through spiral arms. We performed a numerical simulation of MF based on an H i-to-$ \mathrm{H}_2$ phase-transition theory, and reproduced the observations. We estimated the azimuthal scale length of the transition to be less than 200 pc, corresponding to a time scale of $ \sim 2 \,\mathrm{Myr}$ for $ \mathrm{H}_2$ gas formation. The azimuthal width of a molecular arm was estimated to be at most 2.5 kpc, where the gas can remain in the molecular phase for about 25 Myr.
Super-Eddington Black-Hole Models for SS 433
Authors: Okuda Toru
Published: March 2014

We examine highly super-Eddington black-hole models for SS 433, based on two-dimensional hydrodynamical calculations coupled with radiation transport. The super-Eddington accretion flow with a small viscosity parameter, $ \alpha = 10^{-3}$, results in a geometrically–and optically-thick disk with a large opening angle of $ \sim 60^{\circ}$ to the equatorial plane and a very rarefied, hot, and optically-thin high-velocity jets region around the disk. The thick accretion flow consists of two different zones: an inner advection-dominated zone and an outer convection-dominated zone. The high-velocity region around the disk is divided into two characteristic regions, a very rarefied funnel region along the rotational axis and a moderately rarefied high-velocity region outside of the disk. The temperatures of $ \sim 10^7 \,\mathrm{K}$ and the densities of $ \sim 10^{-7} \,\mathrm{g} \,\mathrm{cm}^{-3}$ in the upper disk vary sharply to $ \sim 10^8 \,\mathrm{K}$ and $ 10^{-8}\,\mathrm{g} \,\mathrm{cm}^{-3}$, respectively, across the disk boundary between the disk and the high-velocity region. The X-ray emission of iron lines would be generated only in a confined region between the funnel wall and the photospheric disk boundary, where flows are accelerated to relativistic velocities of $ \sim 0.2 \,c$ due to the dominant radiation-pressure force. The results are discussed regarding the collimation angle of the jets, the large mass-outflow rate observed in SS 433, and the ADAFs and the CDAFs models.
Timing Observation of the Millisecond Pulsar PSR 1937 + 21 Using the Kashima 34 m-Antenna
Authors: Hanado Yuko , Shibuya Yasuhisa , Hosokawa Mizuhiko , Sekido Mamoru , Gotoh Tadahiro , Imae Michito
Published: March 2014

Communications Research Laboratory (CRL) has developed a precise measurement system for millisecond pulsar timing using the 34-m antenna at Kashima Space Research Center, one of the smallest antennas for millisecond pulsar observations. Timing observations of the millisecond pulsar PSR 1937 + 21 have been ongoing since 1997 November at Kashima. From observational data of almost three years, we obtained a timing accuracy of $ 2.65 \,\mu\mathrm{s}$ from daily-averaged residuals, and found the frequency stability to be about $ 1 \times 10^{-13}$ over a period of one year. This result confirms the observational sensitivity of our system, and shows the possibility of constructing a pulsar time scale by using a system with a small antenna.
Discovery of a Dwarf Nova Breaking the Standard Sequence of Compact Binary Evolution
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Yamaoka Hitoshi , Schmeer Patrick , Starkey Donn R. , Torii Ken’ichi , Kawai Nobuyuki , Urata Yuji , Kohama Mitsuhiro , Yoshida Atsumasa , Ayani Kazuya , Kawabata Tetsuya , Tanabe Kenji , Matsumoto Katsura , Kiyota Seiichiro , Pietz Jochen , Vanmunster Tonny , Krajci Tom , Oksanen Arto , Giambersio Antonio
Published: March 2014

We revealed that the dwarf nova 1RXS J232953.9+062814 is an SU UMa-type system with a superhump period of $ 66.774\pm 0.010 \,\mathrm{min}$. The short period strongly indicates that the orbital period of this object is below the period minimum of cataclysmic variables. The superhump period is $ 4.04\pm 0.02$% longer than the photometric period during quiescence ($ 64.184\pm 0.003 \,\mathrm{min}$), which is probably associated with the orbital period. Although the standard evolutionary scenario of cataclysmic variables predicts lower mass-transfer rates in systems with shorter orbital periods, we found firm evidence of a relatively high mass-transfer rate from its large proper motion and bright apparent magnitude. Its proximity indicates that we have overlooked a number of objects in this new class. With the analogous system of V485 Cen, these objects establish the first subpopulation in hydrogen-rich cataclysmic variables below the period minimum.
Radiative–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 and radiation pressures, under a one-dimensional approximation along supposed streamlines. Such a disk wind is characterized by the disk gravitational and radiation fields, whose behavior is rather different from the spherical case. Along the streamline of winds, the gravitational field produced by the central object generally has a peak at some height, unlike the spherical case where it decreases monotonically. The radiation field produced by the disk, on the other hand, is almost constant near to the disk surface and decreases far from the disk, again unlike the spherical case. Due to these characteristic properties of force fields, disk winds are classified into three patterns: in the cold less-luminous case no wind can blow, in the warm luminous case transonic winds are established, and beyond some critical luminosity disk winds are always supersonic. We found that transonic winds can blow for the parameter range of $a_0 + 2\Gamma_\mathrm{eff} \gtrsim 0.8$, where $a_0$ is the initial sound speed in units of the Keplerian speed at the wind base and $\Gamma_\mathrm{eff}$ the normalized disk luminosity at the wind base. Furthermore, supersonic winds blow for $\Gamma_\mathrm{eff} \gtrsim 0.4$. We derive the terminal speed as a function of $\Gamma_\mathrm{eff}$. A radial extension of the flow is also discussed and applied to mass outflow from several active objects.
Emission-Line Eclipse Mapping of Velocity Fields in a Dwarf-Nova Accretion Disk
Authors: Makita Makoto , Mineshige Shin
Published: March 2014

We propose a new method, emission-line eclipse mapping, to map the velocity fields of an accretion disk in position space. Quiescent dwarf novae usually exhibit double-peaked emission-line profiles because of disk rotation. Since a part of a disk having a different line-of-sight velocity is successively obscured by a companion in eclipsing systems, they show time-varying line profiles. We calculated the time changes of the emission-line profiles, assuming Keplerian rotation fields ($v_\varphi\propto r^{-1/2}$ with $r$ being the distance from the disk center) and an emissivity distribution of $j \propto r^{-3/2}$. We, then, applied the usual eclipse mapping technique to the light curves at each of 12–24 wavelengths across the line center to map the region with the same line-of-sight velocity. The reconstructed images typically exhibit a ‘two-eye’ pattern for high line-of-sight velocities, and we can recover the relation, $v_\varphi \propto d^{-1/2}$, on the assumption of an axisymmetric disk, where $d$ is the separation between the two ‘eyes’. We will be able to probe the Keplerian rotation law, the most fundamental assumption adopted in many disk models, by high-speed spectroscopic observations with 8-m class telescopes.
Planetary Perturbations on the 2:3 Mean Motion Resonance with Neptune
Authors: Fuse Tetsuharu
Published: March 2014

A mean motion resonance with Neptune is one of the major dynamical characteristics of the Edgeworth–Kuiper Belt Objects that spread over the outside of Neptune’s orbit. We investigated the influence of Jupiter, Saturn, and Uranus on the dynamical structure of the $2:3$ mean motion resonance with Neptune. Since the distance between the planets and objects has great influence on the dynamical structure, numerical integrations were carried out for test particles for 5 Myr under five fictitious solar-system models having different configurations. In discussion about the results, we concentrate on the size of the EKBO eccentricities, $e$, because they have an especially close relation to the orbital evolution; for example, larger $e$ objects have more opportunities to encounter other objects or planets. By comparing the results of each model, it was found that the resonance structure is not largely affected by Jupiter and Saturn, and that the largest $e$ of the resonant objects depends on the distance between Uranus and the resonance. The distance also influences the structure around the resonance because of variation in the secular resonance positions. We further found that the largest $e$ values of the non-resonant objects at each semi-major axis do not depend on the distance from Uranus; however, they depend on the distance from Neptune.
Dense Molecular Gas in Lenticular Galaxies
Authors: Kuno Nario , Nakai Naomasa , Sorai Kazuo , Nishiyama Kohta , Vila-VilarÓ Baltasar
Published: March 2014

We made CO and HCN simultaneous observations of lenticular galaxies (NGC 404, NGC 3593, and NGC 4293) and detected HCN emission in NGC 3593 and NGC 4293 as well as CO in all the galaxies. The $I_\mathrm{HCN} / I_\mathrm{CO}$ ratios were $0.025 \pm 0.006$ and $0.066 \pm 0.005$ in NGC 3593 and NGC 4293, respectively, which are comparable to that of late-type spiral galaxies. The average of the $I_\mathrm{HCN} / I_\mathrm{CO}$ ratios at the center of 12 nearby spiral galaxies including the late type was $0.055 \pm 0.028$. The line profiles of CO and HCN emission showed different shape in both galaxies. The HCN peaks were not at the systemic velocity of these galaxies, while the CO peaks were near the systemic velocity. These results suggest that the fraction of dense molecular gas is high around the center of these galaxies.
Disk–Halo Model for Flat-Spectrum T Tauri Stars
Authors: Kikuchi Nobuhiro , Nakamoto Taishi , Ogochi Koji
Published: March 2014

We explore the origin of the flat spectrum seen in some T Tauri stars by considering a three-component structure: a central star, a circumstellar disk, and a dusty halo. The radiative energy transport is faithfully treated by solving the angle- and frequency-dependent radiative transfer equation in two space dimensions assuming axisymmetry, and hence the radiative equilibrium temperature in the disk and halo is determined simultaneously. The disk is effectively heated by the scattering and reprocessing of stellar radiation through the halo. The large mid- to far-infrared excess originates from the photosphere of the warmed disk, resulting in a flat spectrum, as observed. The halo which we consider is observed as a compact reflection nebula, and is discriminated from extended, disk-like envelopes around flat-spectrum T Tauri stars. We show that the overall spectral shape of flat-spectrum T Tauri stars can be reproduced by the present disk–halo model.
First Astronomical Fringe of a Test Correlator for the ALMA: Simultaneous Achievement of Wideband and High Resolution
Authors: Okumura Sachiko K. , Iguchi Satoru , Chikada Yoshihiro , Momose Munetake , Okiura Mahoko
Published: March 2014

The first astronomical fringe of a test correlator for the Atacama Large Millimeter/Submillimeter Array (ALMA) is obtained. The newly-developed test correlator system consists of two 4096-Msps Analog-to-Digital Converters (ADCs) and an FX-type correlator that can divide a 2-GHz correlation signal from one baseline into 131072 frequency channels. A fringe spectrum that contains 20 line features as well as continuum emission at $\sim 86.2 \,\mathrm{GHz}$ was obtained by an interferometric observation of the Orion-KL regions using this test system connected to the Nobeyama Millimeter Array (NMA), demonstrating that the realization of high frequency resolution over a wide bandwidth is technically feasible. The installation of such a correlator system in the ALMA will greatly enhance its capability of multi-line imaging.
Gravitational-Wave Radiation from Magnetized Accretion Disks
Authors: Mineshige Shin , Hosokawa Takashi , Machida Mami , Matsumoto Ryoji
Published: March 2014

The detectability of gravitational-wave (GW) radiation from accretion disks is discussed based on various astrophysical contexts. In order to emit GW radiation, the disk shape should lose axial symmetry. We point out that a significant deformation is plausible in non-radiative hot accretion disks because of enhanced magnetic activity, whereas it is unlikely for standard-type cool disks. We have analyzed the 3D magnetohydrodynamical (MHD) simulation data of magnetized accretion flow, finding non-axisymmetric density patterns. The corresponding ellipticity is $ \epsilon \sim 0.01$. The expected time variations of GW radiation are overall chaotic, but there is a hint of quasi-periodicity. GW radiation has no interesting consequence, however, in the case of close binaries, because of very tiny disk masses. GW radiation is not significant, either, for AGN because of very slow rotation velocities. The most promising case can be found in gamma-ray bursts or supernovae, in which a massive torus (or disk) with a solar mass or so may be formed around a stellar-mass compact object as the result of a merger of compact objects, or by the fallback of exploded material towards the center in a supernova. Although much more intense GW radiation is expected before the formation of the torus, the detection of GW radiation in the subsequent accretion phase is of great importance, since it will provide a good probe to investigating their central engines.
Properties of Spiral-Peculiar Type of Kiso Ultraviolet-Excess Galaxies
Authors: Tomita Akihiko , Maehara Hideo
Published: March 2014

We investigated the optical spectroscopic properties of 44 Kiso Ultraviolet-excess Galaxies (KUG), which is one of the most well-known catalogs of blue galaxies. All of our sample galaxies belong to the spiral-peculiar (Sp) type, the morphological class of spiral galaxy with a peculiar bar and/or a nucleus in KUGs. Since the Sp type is considered to be the most peculiar group among KUGs, and about 45% of the KUGs have the Sp type, a detailed study of the Sp type is crucial to understand the characteristics of the KUG. The sample galaxies have luminosities in the $ B$–band of about $ 10^{8}$ to less than $ 10^{10}$ in solar unit, and a median physical size of 13 kpc. From the nuclear spectra, we determined line excitation sources in 39 galaxies. Among them, we detected four AGNs reliably: two Seyfert 1s, one Seyfert 2, and one LINER. Other sample galaxies show moderately star-forming activity. For this category of ordinary KUG group, the mode of the $ \mathrm{H}\alpha$ equivalent width at the nuclear region is a bin of 40 to 60  Å. Three galaxies have extreme starburst nuclei with an $ \mathrm{H}\alpha$ equivalent width of more than 200  Å. The internal extinction of $ A_{V}$ is about 0.8 mag, which suggests that the star-forming nuclei are not heavily enshrouded by dust.
Observation of the Supernova Remnant Kes 79
Authors: Tsunemi Hiroshi , Enoguchi Hideyuki
Published: March 2014

We report here on an ASCA observation of Kes 79, a possible mixed-morphology (MM) SNR. There are two radio shells: an inner shell and an outer shell. A ROSAT observation revealed an inner ring in X-ray that has been confirmed by the ASCA observation. The X-ray intensity peak is near the inner radio shell. The X-ray spectrum is well-fitted by a single component of the non-equilibrium ionization condition model with about 0.7-times the solar abundance. The plasma age estimated from the ionization parameter is only $ 3.3\times 10^3 \,\mathrm{yr}$. The temperature is uniform ($ \sim 0.7 \,\mathrm{keV}$) while the density profile is approximated by a point symmetric Gaussian function. Comparing the Kes79 results with those of Kes27, a prototypical MM SNR, Kes 79 may not belong to the MM type SNRs.
Detection of Zinc in the Very Metal-Poor Post-AGB Star HR 4049
Authors: Takeda Yoichi , Parthasarathy Mudumba , Aoki Wako , Ita Yoshifusa , Nakada Yoshikazu , Izumiura Hideyuki , Noguchi Kunio , Takada-Hidai Masahide , Sato Bun’ei , Tajitsu Akito , Honda Satoshi , Kawanomoto Satoshi , Ando Hiroyasu , Karoji Hiroshi
Published: March 2014

We report on the detection of two Zn i lines at 4722.15 Å and 4810.53 Å in the high-quality spectrum of the very metal-poor post-AGB star HR 4049, which was obtained with the High Dispersion Spectrograph attached to the Subaru Telescope. The strengths of these lines indicate an appreciable underabundance of Zn by $ \sim-1.3 \,\mathrm{dex}$ relative to the Sun. The fact that this volatile element, similarly to others belonging to the same group (e.g., C, N, O, S), does not conform to the extreme depletion ($ \gt 4 \,\mathrm{dex}$) of refractory metals (e.g., Fe), strongly suggests that grain formation has something to do with the origin of the chemical peculiarity. This (not extremely but significantly) subsolar value of $ \mathrm{[Zn/H]}$ is quantitatively discussed in connection with those of other volatile species, especially with respect to S. We also detected a new Fe ii line at 5159.03 Å along with the already known Fe ii 4923.93 Å line; based on these two lines the Fe abundance of HR 4049 is determined to be $ \sim 2.8$ ($ \mathrm{[Fe/H]} \sim-4.7$).
Activity Cycle of Polar Faculae
Authors: Li Kejun , Irie Makoto , Wang Jingxiu , Xiong Songying , Yun Hongsik , Liang Hongfei , Zhan Lashen , Zhao Haizhuan
Published: March 2014

The data of the polar faculae observed by the National Astronomical Observatory of Japan from the year 1951 through 1991 and the Mount Wilson Observatory from 1906 to 1990 were analysed. We found that the polar facula cycle is in complete antiphase with the sunspot cycle, and highly correlated with the sunspot cycle with a time shift of 51 months into the following sunspot cycle. We also made a quantitative analysis of the hemispheric distribution of polar faculae, and found that hemispheric asymmetry exists, as in solar activity at low latitude. However, the hemispheric asymmetry of polar faculae seems to have little relationship with the asymmetry of solar activity at low latitude.