bluuebunny/crossref_metadata_2025_split huggingface dataset:
Absorption Measurement of Hydrogen Molecules in the Early Universe
Authors: Shibai Hiroshi , Takeuchi Tsutomu T. , Rengarajan T. N. , Hirashita Hiroyuki 
Published: March 2014

Abstract
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

Abstract
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.
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

Abstract
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

Abstract
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.
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
Super-Eddington Black-Hole Models for SS 433
Authors: Okuda Toru 
Published: March 2014

Abstract
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

Abstract
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

Abstract
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.
Planetary Perturbations on the 2:3 Mean Motion Resonance with Neptune
Authors: Fuse Tetsuharu 
Published: March 2014

Abstract
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.
Disk–Halo Model for Flat-Spectrum T Tauri Stars
Authors: Kikuchi Nobuhiro , Nakamoto Taishi , Ogochi Koji 
Published: March 2014

Abstract
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.