bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solar-Cycle Variation of Magnetic Helicity in Active Regions
Authors: Hagino Masaoki , Sakurai Takashi 
Published: March 2014

Abstract
The hemispheric sign rule of helicity and its long-term variation were studied. The data were obtained from the Solar Flare Telescope at Mitaka and the 65-cm solar telescope at Okayama. The data covered the period of 1983–2001, from the declining phase of solar cycle 21 to the rising phase of cycle 23. Although the hemispheric sign rule of helicity generally holds, we also found significant time variations in the yearly values of helicity during the observation period. The hemispheric sign rule of helicity is satisfied in the solar maximum phase, but may not be so in the solar minimum phase.
Dense and Warm Molecular Gas between Double Nuclei of the Luminous Infrared Galaxy NGC 6240
Authors: Nakanishi Kouichiro , Okumura Sachiko K. , Kohno Kotaro , Kawabe Ryohei , Nakagawa Takao 
Published: March 2014

Abstract
High spatial resolution observations of the ${{12\atop} \mathrm{CO}}$ (1–0), HCN(1–0), $\mathrm{HCO}^{\mkern-1.26421mu{+}\mkern-2.52842mu}$(1–0), and ${{13\atop} \mathrm{CO}}$(1–0) molecular lines toward the luminous infrared merger NGC 6240 have been performed using the Nobeyama Millimeter Array and the RAINBOW Interferometer. All of the observed molecular emission lines are concentrated in the region between the double nuclei of the galaxy. However, the distributions of both HCN and $\mathrm{HCO}^{{\mkern-1.26421mu{+}\mkern-2.52842mu}}$ emissions are more compact compared with that of ${{12\atop} \mathrm{CO}}$, and they are not coincident with the star-forming regions. The $\mathrm{HCN} / {{12\atop} \mathrm{CO}}$ line intensity ratio is 0.25; this suggests that most of the molecular gas between the double nuclei is dense. A comparison of the observed high $\mathrm{HCN}/{{13\atop} \mathrm{CO}}$ intensity ratio, 5.9, with large velocity gradient calculations suggests that the molecular gas is dense [$n(\mathrm{H}_2) = 10^{4 \hbox{--} 6} \,\mathrm{cm}^{-3}$] and warm ($T_{\mathrm{kin}} \gt 50 \,\mathrm{K}$$T_{\mathrm{kin}} \gt 50 \,\mathrm{K}$). The observed structure in NGC 6240 may be explained by time evolution of the molecular gas and star formation, which was induced by an almost head-on collision or very close encounter of the two galactic nuclei accompanied with the dense gas and star-forming regions.
Spatially Resolved Spectral Analysis of Vela Shrapnel D
Authors: Katsuda Satoru , Tsunemi Hiroshi 
Published: March 2014

Abstract
The ROSAT all-sky survey discovered several ‘shrapnels’, showing boomerang structures outside the Vela supernova remnant. We observed shrapnel D with the XMM-Newton satellite. There is an X-ray bright ridge structure in our FOV running from north to south. Applying the VNEI model to X-ray spectra of various regions, we find that the plasma in the eastern part from the X-ray ridge is significantly different from that in the western part. The X-ray spectra in the western part can be represented by a single-temperature component. The abundances of heavy elements are almost uniform, whereas they are heavily overabundant, except for Fe; the relative abundances to the solar values are $\mathrm{O} \sim 5, \mathrm{Ne} \sim10 , \mathrm{Mg} \sim 10, \mathrm{Fe} \sim 1$. This indicates that shrapnel D originated from the ejecta of the supernova. We find that the plasma in the eastern part from the ridge consists of two components with different temperatures; the hot component comes from the ejecta, while the cold component comes from the interstellar matter. These two components are considered to be in contact with each other, forming a contact discontinuity. Around the northern part of the contact discontinuity, we find wave-like structures of which the typical scale are comparable with that of the Rayleigh–Taylor instability.
Radio Interferometer Sensitivities for Three Types of Receiving Systems: DSB, SSB, and 2SB Systems
Authors: Iguchi Satoru 
Published: March 2014

Abstract
The purpose of this paper is to study the detection sensitivity suitable to the practical situation for a radio interferometer. For the radio interferometer, the three types of receiving systems are a double-sideband (DSB), a single-sideband (SSB), and a two-single-sideband (2SB) systems. The evaluation of these receiving systems is of significance to explore the best performance for a radio interferometer. In this paper, the signal-to-noise ratios of these three-type receiving systems are newly derived to investigate the performance and key features of each system. We demonstrate the system noise temperatures of SSB, 2SB, and DSB receiving systems by using the ALMA-specification receiver noise temperature and the atmosphere condition measured at the ALMA site, and present the relative sensitivities between the 2SB and DSB receiving systems at the ALMA site. From these results, we recommend the 2SB receiving system for all bands of ALMA.
HETE-2 Localization and Observations of the Gamma-Ray Burst GRB 020813
Authors: Sato Rie , Sakamoto Takanori , Kataoka Jun , Yoshida Atsumasa , Suzuki Motoko , Kotoku Junichi , Urata Yuji , Yamamoto Yoshihisa , Arimoto Makoto , Tamagawa Toru , Shirasaki Yuji , Torii Ken’ichi , Matsuoka Masaru , Nakagawa Yujin , Yamazaki Toru , Tanaka Kaoru , Maetou Miki , Yamauchi Makoto , Takagishi Kunio , Lamb Donald Q. , Atteia Jean-Luc , Vanderspek Roland , Graziani Carlo , Prigozhin Gregory , Villasenor Joel , Jernigan J. Garrett , Crew Geoffrey B. , Hurley Kevin , Ricker George R. , Woosley Stanford E. , Butler Nat , Levine Al , Doty John P. , Donaghy Timothy Q. , Fenimore Edward E. , Galassi Mark , Boer Michel , Dezalay Jean-Pascal , Olive Jean-François , Braga Joao , Manchanda Ravi , Pizzichini Graziella , Kawai Nobuyuki 
Published: March 2014

Abstract
A bright, long gamma-ray burst (GRB) was detected and localized by the instruments on board the High Energy Transient Explorer 2 satellite (HETE-2) at 02:44:19.17 UTC (9859.17 s UT) on 2002 August 13. The location was reported to the GRB Coordinates Network (GCN) about 4 min after the burst. In the prompt emission, the burst had a duration of approximately 125 s, and more than four peaks. We analyzed the time-resolved 2–400 keV energy spectra of the prompt emission of GRB 020813 using the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE) in detail. We found that the early part of the burst (17–52 s after the burst trigger) shows a depletion of low-energy photons below about 50 keV. It is difficult to explain the depletion by either synchrotron self-absorption or Comptonization. One possibility is that the low-energy depletion may be understood as a mixture of “jitter” radiation with the usual synchrotron radiation component.
Primordial Molecular Emission in Population III Galaxies
Authors: Mizusawa Hiromi , Omukai Kazuyuki , Nishi Ryoichi 
Published: March 2014

Abstract
We consider the formation of molecules in primordial prestellar clumps and evaluate the line luminosities to assess detectability by next-generation observational facilities. If the initial $\mathrm{H}_2$ fraction is sufficiently high, HD becomes an important coolant in the clumps. The luminosity from such HD cooling clumps is lower than that from $\mathrm{H}_2$ cooling ones because of the lower temperature ($&lt;100 \,\mathrm{K}$). As for Li reactions, we include the three-body LiH formation approximately. The Li molecular fraction remains very low ($&lt;10^{-3}$) throughout the evolution, owing to the high dissociative reaction rate of $\mathrm{LiH} + \mathrm{H} \rightarrow \mathrm{Li} + \mathrm{H}_2$. LiH does not become an important coolant in any density range. The luminous emission lines from the prestellar cores include $\mathrm{H}_2$ rovibrational lines [1–0 Q(1), 1–0 O(3), 1–0 O(5)] and pure rotational lines [0–0 S(3), 0–0 S(4), 0–0 S(5)]. The next-generation facilities SPICA and JWST are able to detect $\mathrm{H}_2$ emission in a large pre-galactic cloud that forms metal-free stars at a high rate of $\sim 10^3 \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1}$ at a redshift of $z &lt; 10$. We also derive an analytical expression for the luminosity that reproduces the numerical results.
Atlas and Catalog of Dark Clouds Based on Digitized Sky Survey I
Authors: Dobashi Kazuhito , Uehara Hayato , Kandori Ryo , Sakurai Tohko , Kaiden Masahiro , Umemoto Tomofumi , Sato Fumio 
Published: March 2014

Abstract
We present a quantitative atlas and catalog of dark clouds derived by using the optical database “Digitized Sky Survey I”. Applying a traditional star-count technique to 1043 plates contained in the database, we produced an $A_V$ map covering the entire region in the galactic latitude range $\vert b\vert \le 40^\circ$. The map was drawn at two different angular resolutions of $6'$ and $18'$, and is shown in detail in a series of figures in this paper. Based on the $A_V$ map, we identified 2448 dark clouds and 2841 clumps located inside them. Some physical parameters, such as the position, extent, and optical extinction, were measured for each of the clouds and clumps. We also searched for counterparts among already known dark clouds in the literature. The catalog of dark clouds presented in this paper lists the cloud parameters as well as the counterparts.
Sunspot Gyroresonance Emission at 17 GHz: A Statistical Study
Authors: Vourlidas Angelos , Gary Dale E. , Shibasaki Kiyoto 
Published: March 2014

Abstract
We investigate the sunspot gyroresonance emission at 17 GHz using the synoptic database of the Nobeyama Radioheliograph. Our statistical study is based on full disk observations obtained during the maximum of Cycle 22 (1992–94). We study the center-to-limb variation of the brightness and polarization of the sunspot radio emission and present some cases of polarization reversal. We find that the radio emission is most likely 3rd-harmonic gyroresonance emission arising from 2000 G fields in transition region, or low corona temperatures.
Formation of Magnetically Supported Disks during Hard-to-Soft Transitions in Black Hole Accretion Flows
Authors: Machida Mami , Nakamura Kenji E. , Matsumoto Ryoji 
Published: March 2014

Abstract
We carried out three-dimensional global resistive magnetohydrodynamic simulations of the cooling instability in optically thin hot black hole accretion flows by assuming bremsstrahlung cooling. General relativistic effects are simulated using the pseudo-Newtonian potential. The cooling instability grows when the density of the accretion disk becomes sufficiently large. We found that as the instability grows the accretion flow changes from an optically thin, hot, gas pressure-supported state (low/hard state) to a cooler, magnetically supported, quasi-steady state. During this transition, the magnetic pressure exceeds the gas pressure because the disk shrinks in the vertical direction while almost conserving the toroidal magnetic flux. Since further vertical contraction of the disk is suppressed by magnetic pressure, the cool disk stays in an optically thin, spectrally hard state. The magnetically supported disk exists for a time scale much longer than the thermal time scale, and comparable to the accretion time scale. We examined the stability of the magnetically supported disk analytically, assuming that the toroidal magnetic flux is conserved, and found it to be thermally and secularly stable. Our findings may explain why black hole candidates stay in luminous, hard state even when their luminosity exceeds the threshold for the onset of the cooling instability.
Detection of HCOOCH3 toward a Low-Mass Protostar, NGC 1333 IRAS 4B
Authors: Sakai Nami , Sakai Takeshi , Yamamoto Satoshi 
Published: March 2014

Abstract
The rotational spectral lines of methylformate ($\mathrm{HCOOCH}_3$) have been detected toward a low-mass protostar, NGC 1333 IRAS 4B, with the Nobeyama 45 m radio telescope. The column density is derived to be $(7 \hbox{--} 37) \times 10^{15} \,\mathrm{cm}^{-2}$, assuming a source size of $1^{\prime\prime}$ and the range of the excitation temperature to be from 50 K to 200 K. The column density is almost comparable to those found in other low-mass star-forming regions, NGC 1333 IRAS 4A and IRAS 16293$-$2422. The line width of $\mathrm{HCOOCH}_3$ is $(1.0 \hbox{--} 1.2) \,\mathrm{km} \,\mathrm{s}^{-1}$, which is narrower than that of the high-excitation line of $\mathrm{CH}_3\mathrm{OH}$ ($8_{-4} \hbox{--} 9_{-3}$). Since NGC 1333 IRAS 4B is likely to be a very young protostar, $\mathrm{HCOOCH}_3$ appears even in the early stage of protostellar evolution. The spectral lines of $\mathrm{HCOOCH}_3$ could be used as a novel tracer for detecting an onset of star formation.
The Parsec-Scale Jet of PKS 0637−752
Authors: Edwards Philip G. , Piner B. Glenn , Tingay Steven J. , Lovell James E. J. , Kataoka Jun , Ojha Roopesh , Murata Yasuhiro 
Published: March 2014

Abstract
Chandra observations of the quasar PKS 0637$-$752 during its checkout phase resulted in the unexpected detection of a luminous kiloparsec-scale X-ray jet. The apparent superluminal speed of this jet on the parsec-scale, based on two VSOP and four ground-based observations, has proven crucial to understanding the X-ray production in the arcsec-scale jet. We present here for the first time the full details of the ground-based observations used to determine the parsec-scale jet speed, describe the results of a third VSOP observation, and examine the reported jet speed in the light of more recent ground-based VLBI observations. We find some evidence of increased source activity coincident with extrapolated epochs of jet component ejection, although the monitoring of the source is relatively sparse and the ejection epochs are not tightly constrained. We also construct the spectral energy distribution for the nucleus of PKS 0637$-$752 and show that it can be modelled well in terms of a one-zone synchrotron self-Compton model of an electron-positron jet with a Doppler factor of $\sim 10$, consistent with the results of the VLBI observations.
Systematic Bias in an Estimate of the Cluster Mass and the Fluctuation Amplitude from Cluster Abundance Statistics
Authors: Shimizu Mamoru , Kitayama Tetsu , Sasaki Shin , Suto Yasushi 
Published: March 2014

Abstract
We revisit an estimate of the mass fluctuation amplitude, $\sigma_{8}$, from the observational X-ray cluster abundance. In particular, we examine the effect of the systematic difference between the cluster virial mass estimated from the X-ray spectroscopy, $M_\mathrm{vir,\, spec}$, and the true virial mass of the corresponding halo, $M_\mathrm{vir}$. Mazzotta et al. (2004, MNRAS, 354, 10) recently pointed out the possibility that $\alpha_{M} = M_\mathrm{vir,\, spec} / M_\mathrm{vir}$ is systematically lower than unity. We performed a statistical analysis by combining the latest X-ray cluster sample and the improved theoretical models, and found that $\sigma_8 \sim 0.76 \pm 0.01 + 0.50 \, (1-\alpha_{M})$ for $0.5 \le \alpha_{M} \le 1$, where the quoted errors are only statistical. Thus, if $\alpha_{M} \sim 0.7$, the value of $\sigma_8$ from cluster abundance alone is now in better agreement with other cosmological data, including the cosmic microwave background, the galaxy power spectrum and the weak lensing data. The current study also illustrates the importance of possible systematic effects in mapping real clusters to underlying dark halos, which changes the interpretation of cluster abundance statistics.
The Near-Contact Binary RU Ursae Minoris
Authors: Li-Ying Zhu , Sheng-Bang Qian , Fu-Yuan Xiang 
Published: March 2014

Abstract
The near-contact binary RU UMi with an F0-type primary and a K-type secondary was observed in 2003. With the latest version of the Wilson–Devinney code, the photometric elements were computed. The results reveal that RU UMi is a semi-detached system with the secondary component filling its Roche lobe, which should lead to an increase of the period for conservative mass transfer between the two components. However, an orbital period analysis shows that the orbital period of this system undergoes a continuous decrease at a rate of $dP/dt =-1.72 \times 10^{-8} \,\mathrm{d} \,\mathrm{yr}^{-1}$. Therefore, the continuous period decrease may demonstrate that the system is nonconservative. This can result from a combined effect of mass transfer from the secondary component to the primary one and mass and angular momentum loss from the system. With the secular mass and angular momentum losses, RU UMi may evolve from the present short-period near-contact system into an A-type contact binary.
Subaru Near Infrared Coronagraphic Images of T Tauri
Authors: Mayama Satoshi , Tamura Motohide , Hayashi Masahiko , Itoh Yoichi , Fukagawa Misato , Suto Hiroshi , Ishii Miki , Murakawa Koji , Oasa Yumiko , Hayashi Saeko S. , Yamashita Takuya , Morino Junichi , Oya Shin , Naoi Takahiro , Pyo Tae-Soo , Nishikawa Takayuki , Kudo Tomoyuki , Usuda Tomonori , Ando Hiroyasu , Miyama Shoken M. , Kaifu Norio 
Published: March 2014

Abstract
High angular resolution near-infrared (JHK) adaptive optics images of T Tau were obtained with the infrared camera Coronagraphic Imager with Adaptive Optics (CIAO) mounted on the 8.2 m Subaru Telescope in 2002 and 2004. The images resolve a complex circumstellar structure around a multiple system. We resolved T Tau Sa and Sb as well as T Tau N and S. The estimated orbit of T Tau Sb indicates that it is probably bound to T Tau Sa. The $K$ band flux of T Tau S decreased by $\sim 1.7 \,\mathrm{Jy}$ in 2002 November compared with that in 2001 mainly because T Tau Sa became fainter. The arc-like ridge detected in our near-infrared images is consistent with what is seen at visible wavelengths, supporting the interpretation in previous studies that the arc is part of the cavity wall seen relatively pole-on. Halo emission is detected out to $\sim 2^{\prime\prime}$ from T Tau N. This may be light scattered off the common envelope surrounding the T Tauri multiple system.
Kinematics of SiOJ = 8–7 Emission towards the HH 212 Jet
Authors: Takami Michihiro , Takakuwa Shigehisa , Momose Munetake , Hayashi Masa , Davis Christopher J. , Pyo Tae-Soo , Nishikawa Takayuki , Kohno Kotaro 
Published: March 2014

Abstract
We present SiO $J = 8 \hbox{--} 7$ (347.3 GHz) observations towards HH 212 (Herbig-Haro object 212) using the ASTE (Atacama Submillimeter Telescope Experiment) telescope. Our observations with a $22^{\prime\prime}$-diameter beam show that the SiO emission is highly concentrated within $1'$ of the driving source. We carefully compare the SiO observations with archival $\mathrm{H}_2$ 1–0 S(1) images and published $\mathrm{H}_2$ echelle spectra. We find that, although the SiO velocities closely match the radial velocities seen in $\mathrm{H}_2$, the distributions of $\mathrm{H}_2$ and SiO emission differ markedly. We attribute the latter to the different excitation conditions required for $\mathrm{H}_2$ and SiO emission, particularly the higher critical density ($n_{\mathrm{H}_2} \sim 10^8 \,\mathrm{cm}^{-3}$) of the SiO $J = 8 \hbox{--} 7$ emission. The kinematic similarities imply that the $\mathrm{H}_2$ and SiO are associated with the same internal working surfaces. We conclude that the SiO $J = 8 \hbox{--} 7$ emission has a potential for probing the jet/wind launching region through interferometric observations in the future, particularly for the youngest, most deeply embedded protostars where IR observations are not possible.
Deep Extragalactic Surveys around the Ecliptic Poles with AKARI (ASTRO-F)
Authors: Matsuhara Hideo , Wada Takehiko , Matsuura Shuji , Nakagawa Takao , Kawada Mitsunobu , Ohyama Youichi , Pearson Chris P. , Oyabu Shinki , Takagi Toshinobu , Serjeant Stephen , White Glenn J. , Hanami Hitoshi , Watarai Hidenori , Takeuchi Tsutomu T. , Kodama Tadayuki , Arimoto Nobuo , Okamura Sadanori , Lee Hyung Mok , Pak Soojong , Im Myung Shin , Lee Myung Gyoon , Kim Woojung , Jeong Woong-Seob , Imai Koji , Fujishiro Naofumi , Shirahata Mai , Suzuki Toyoaki , Ihara Chiaki , Sakon Itsuki 
Published: March 2014

Abstract
AKARI (formerly ASTRO-F) is an infrared space telescope designed for an all-sky survey at 10–180$\, {\mu \mathrm {m}}$, and deep pointed surveys of selected areas at 2–180$\, {\mu \mathrm {m}}$. The deep pointed surveys with AKARI will significantly advance our understanding of galaxy evolution, the structure formation of the universe, the nature of buried AGNs, and the cosmic infrared background. We describe here the important characteristics of the AKARI mission, the orbit, and attitude control system, and investigate the optimum survey area based on the updated pre-flight sensitivities of AKARI, taking into account the cirrus confusion noise as well as the surface density of bright stars. The North Ecliptic Pole is concluded to be the best area for 2–26$\, {\mu \mathrm {m}}$ deep surveys, while the low-cirrus noise regions around the South Ecliptic Pole are worth considering for 50–180$\, {\mu \mathrm {m}}$ pointed surveys to high sensitivities limited by the galaxy confusion noise. Current observational plans concerning these pointed surveys are described in detail. Comparing these surveys with deep surveys using the Spitzer Space Telescope, the AKARI deep surveys are particularly unique in respect of their continuous wavelength coverage over the 2–26$\, {\mu \mathrm {m}}$ range in broad-band deep imaging, and their slitless spectroscopy mode over the same wavelength range.
Non-Uniform Temperature Distribution in the Galaxy Clusters 2A 0335+096 and Abell 496 Observed by XMM-Newton
Authors: Tanaka Takeshi , Kunieda Hideyo , Hudaverdi Murat , Furuzawa Akihiro , Tawara Yuzuru 
Published: March 2014

Abstract
We present the XMM-Newton results of the galaxy clusters 2A 0335$+$096 and A496. From an investigation of 2-dimensional ICM profiles, we obtained new features related to dynamical activities in the ICM. In 2A 0335$+$096, we found a spiral cool tail around the central cold core, which is trailing from the opposite side of the cold front observed by Chandra. The deprojected temperature of the tail is 1.7 keV. The spiral feature apparently shows a turnaround motion of the core. We suggest that the cool tail feature represents evidence for turbulent viscous stripping of the remaining subcluster core. For A496, we found another cold front $4^{\prime}$ south of the X-ray emission peak. From the pressure profile across the cold front, we derived an upper limit to the Mach number of a gas body of 0.2. Regarding the temperature distribution in the outer region, we found non-uniformity on the cluster scale for both clusters, which suggests that both clusters experienced a merger in the past. We argue that the gas dynamical motions seen in the central regions of both clusters can be attributed to the past merger.