bluuebunny/crossref_metadata_2025_split huggingface dataset:
Period Change and Possible Magnetic Braking in WY Cancri
Authors: Tian Yongpo , Xiang Fuyuan , Xie Wenli , Tao Xia 
Published: March 2014

Abstract
In this paper, the orbital period change of the RS CVn-type binary system WY Cnc is analyzed through a detailed description of the $O-C$ curve by a weighted least-squares method. It is found that the period variation is suffering a secular period decrease at a rate of $dp/dt$$=$$-$1.20 $\times$ 10$^{-7}$dy$^{-1}$. Since WY Cnc is a typical detached binary system, and both components are late-type stars, the long-term period decrease may be caused by angular momentum loss via magnetic braking.
Early Spectral Evolution of the Rapidly Expanding Type Ia Supernova 2006X
Authors: Yamanaka Masayuki , Naito Hiroyuki , Kinugasa Kenzo , Takanashi Naohiro , Tanaka Masaomi , Kawabata Koji S. , Ozaki Shinobu , Narusawa Shin-ya , Sadakane Kozo 
Published: March 2014

Abstract
We present optical spectroscopic and photometric observations of Type Ia supernova (SN Ia) 2006X from 10 d before the $B$-band maximum to 91 d after. This object exhibits one of the highest expansion velocities ever published for SNe Ia. At its premaximum phases, the spectra show strong and broad features of intermediate-mass elements, such as Si, S, Ca, and Mg, while the Oi$\lambda$7773 line is weak. The extremely high velocities of the Si ii and S ii lines and the weak feature of the Oi line suggest that an intense nucleosynthesis might take place in the outer layers, favoring a delayed detonation model. Interestingly, the Si ii$\lambda$5972 feature is quite shallow, resulting in an unusually low depth ratio of Si ii$\lambda$5972 to Si ii$\lambda$6355, $\cal R$(Si ii). The low $\cal R$(Si ii) is usually interpreted as being a high photospheric temperature. However, the weak Si iii$\lambda$4560 line suggests a low temperature, in contradiction with an interpretation on the low $\cal R$(Si ii). This could imply that the Si ii$\lambda$5972 line might be contaminated by underlying emission. We propose that $\cal R$(Si ii) may not be a good temperature indicator for a rapidly expanding SN Ia in the premaximum phases.
High-Power Laser Beam Transfer through Optical Relay Fibers for a Laser Guide Adaptive Optics System
Authors: Ito Meguru , Hayano Yutaka , Saito Yoshihiko , Takami Hideki , Saito Norihito , Akagawa Kazuyuki , Takazawa Akira , Ito Mayumi , Wada Satoshi , Iye Masanori 
Published: March 2014

Abstract
We are developing a laser guide star adaptive optics (LGSAO) system for the Subaru Telescope on Mauna Kea, Hawaii. The AO188 system will dramatically increase the observable sky area. This system differs from systems used at other large telescopes in that it utilizes the combination of an all-solid-state mode-locked sum-frequency generation (SFG) laser as a light source and single-mode optical fiber for beam transference. Optical fibers transfer laser light from the source, located at the Nasmyth platform, to the laser launching telescope more flexibly and more easily than do mirror relay optics. However, optical fibers induce nonlinear scattering effects, such as stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS), beyond certain threshold levels in high-power lasers. We measured the laser transmission characteristics of a photonic crystal fiber (PCF) whose mode field diameter (MFD) was 11$\mu$m, and a step index fiber (SIF) cable whose MFD was 4.2$\mu$m to evaluate the threshold levels for non-linear effects. We observed SRS in the 200-m-long SIF when we input 1.3 W. However, SRS and SBS were not induced in the 200-m-long PCF, even for an input power of 5.3 W. As a result, we estimated the threshold of SRS to be 33 W for the 35-m-long PCF designed for the Subaru LGSAO system. Given that the fiber will carry a laser beam of about 30 W with a pulse width of less than 1 ns, we conclude that nonlinear scattering will pose no problems for this application.
Energy Spectra of the Soft X-Ray Diffuse Emission in Fourteen Fields Observed with Suzaku
Authors: Yoshino Tomotaka , Mitsuda Kazuhiasa , Yamasaki Noriko Y. , Takei Yoh , Hagihara Toshishige , Masui Kensuke , Bauer Michael , McCammon Dan , Fujimoto Ryuichi , Daniel Wang Q. , Yao Yangsen 
Published: March 2014

Abstract
The soft diffuse X-ray emission of twelve fields observed with Suzaku are presented together with two additional fields from previous analyses. All have galactic longitudes 65$^\circ $$\lt$$\ell$$\lt$ 295$^\circ $ to avoid contributions from the very bright diffuse source that extends at least 30$^\circ $ from the Galactic center. The surface brightnesses of the Suzaku nine fields for which apparently uncontaminated ROSAT All Sky Survey (RASS) were available were statistically consistent with the RASS values, with an upper limit for differences of 17 $\times$ 10$^{-6}$cs$^{-1}$arcmin$^{-2}$ in R45-band. The OVII and OVIII intensities are well correlated to each other, and OVII emission shows an intensity floor at $\sim$2 photonss$^{-1}$cm$^{-2}$str$^{-1}$ (LU). The high-latitude OVIII emission shows a tight correlation with excess of OVII emission above the floor, with (OVIII intensity) $=$ 0.5 $\times$ [(OVII intensity) $-$ 2LU], suggesting that temperatures averaged over different line-of-sight show a narrow distribution around $\sim$0.2 keV. We consider that the offset intensity of OVII arises from the Heliospheric solar wind charge exchange and perhaps from the local hot bubble, and that the excess OVII (2–7LU) is emission from more distant parts of the Galaxy. The total bolometric luminosity of this galactic emission is estimated to be 4 $\times$ 10$^{39}$ergs$^{-1}$, and its characteristic temperature may be related to the virial temperature of the Galaxy.
A Peculiar Jet and Arc of Molecular Gas toward the Rich and Young Stellar Cluster Westerlund 2 and a TeV Gamma Ray Source
Authors: Fukui Yasuo , Furukawa Naoko , Dame Thomas M. , Dawson Joanne R. , Yamamoto Hiroaki , Rowell Gavin P. , Aharonian Felix , Hofmann Werner , de Oña Wilhelmi Emma , Minamidani Tetsuhiro , Kawamura Akiko , Mizuno Norikazu , Onishi Toshikazu , Mizuno Akira , Nagataki Shigehiro 
Published: March 2014

Abstract
We have discovered remarkable jet- and arc-like molecular features toward the rich and young stellar cluster Westerlund 2. The jet has a length of $\sim$100 pc and a width of $\sim$10 pc, while the arc shows a crescent shape with a radius of $\sim$30 pc. These molecular features each have masses of $\sim$10$^{4}M_{\odot}$, and show spatial correlations with the surrounding lower density H i gas. The jet also shows an intriguing positional alignment with the core of the TeV gamma-ray source HESS J1023$-$575 and with the MeV/GeV gamma-ray source recently reported by the Fermi collaboration. We argue that the jet and arc are caused by an energetic event in Westerlund 2, presumably due to an anisotropic supernova explosion of one of the most massive member stars. While the origin of the TeV and GeV gamma-ray sources is uncertain, one may speculate that they are related to the same event via relativistic particle acceleration by strong shock waves produced at the explosion or by remnant objects, such as a pulsar wind nebula or a microquasar.
Effects of Mutual Transits by Extrasolar Planet–Companion Systems on Light Curves
Authors: Sato Masanao , Asada Hideki 
Published: March 2014

Abstract
We consider the effects of mutual transits by extrasolar planet–companion systems (in a true binary or a planet–satellite system) on light curves. We show that induced changes in light curves depend strongly on a ratio between a planet–companion’s orbital velocity around their host star and a planet–companion’s spin speed around their common center of mass. In both the slow and fast-spin cases (corresponding to long and short distances between them, respectively), a certain asymmetry appears in light curves. We show that, especially in the case of short distances, occultation of one faint object by the other, while the transit of the planet–companion system occurs in front of its parent star, causes an apparent increase in light curves, and characteristic fluctuations appear as important evidence of mutual transits. We show also that extrasolar mutual transits provide a complementary method for measuring the radii of two transiting objects, their separation and masses, and consequently for identifying the system as a true binary, a planet–satellite system, or others. Monitoring 10$^5$ stars for 3 yr with Kepler may lead to the discovery of a second Earth–Moon-like system if the fraction of such systems for an averaged star is larger than 0.05, or we may put an upper limit on the fraction as $f$$\lt$ 0.05.
Millimeter- and Submillimeter-Wave Observations of the OMC-2/3 Region. IV Interaction between the Outflow and the Dense Gas in the Cluster Forming Region of OMC-2 FIR 6
Authors: Shimajiri Yoshito , Takahashi Satoko , Takakuwa Shigehisa , Saito Masao , Kawabe Ryohei 
Published: March 2014

Abstract
We have conducted millimeter interferometric observations of the Orion Molecular Cloud-2 (OMC-2) FIR 6 region at an angular resolution of $\sim$ 4${}^{\prime\prime}$–7${}^{\prime\prime}$ with the Nobeyama Millimeter Array (NMA). In the 3.3-mm continuum emission we detected dusty core counterparts of previously identified FIR sources (FIR 6a, 6b, 6c, and 6d), and moreover resolved FIR 6a into three dusty cores. The size and mass of these cores are estimated to be 1100–5900 AU and 0.19–5.5$ M_{\odot}$, respectively. We found that in the $^{12}$CO ($J$$=$ 1–0) emission FIR 6b, 6c, and 6d eject molecular outflow, and that the FIR 6c outflow also exhibits at least two collimated jet-like components in SiO ($J$$=$ 2–1) emission. At the tip of one of the SiO components there appears an abrupt increase in the SiO line width ($\sim$ 15 km s$^{-1}$), where the three resolved cores in FIR 6a seem to delineate the tip. These results imply the presence of the interaction and a bowshock front between the FIR 6c molecular outflow and FIR 6a. If the interaction occurred after the formation of the FIR 6a cores, the influence of the FIR 6c outflow on the FIR 6a cores would be minimal, since the total gravitational force in the FIR 6a cores (1.0–7.7 $\times$ 10$^{-4} M_{\odot} $km s$^{-1}$yr$^{-1}$) is much larger than the outflow momentum flux (2.4 $\times$ 10$^{-5} M_{\odot} $km s$^{-1}$yr$^{-1}$). On the other hand, it is also possible that the interaction caused the gravitational instability in FIR 6a, and triggered the fragmentation into three cores, since the separation among these cores ($\sim$ 2.0 $\times$ 10$^{3} $AU) is on the same order of the Jeans length ($\sim$ 5.0–8.4 $\times$ 10$^{3} $AU). In either case, FIR 6a cores, with a mass of 0.18–1.6$ M_{\odot}$ and a density of 0.2–5.8 $\times$ 10$^{7} $cm$^{-3}$, might be potential formation sites of the next generation of cluster members.
Design of Corrective Beam Waveguide System for the ALMA/ACA 7-m Antenna
Authors: Sugimoto Masahiro , Carter Matthew , Inatani Junji , Sekimoto Yutaro , Iguchi Satoru 
Published: March 2014

Abstract
A beam waveguide system for connecting the ALMA front-end, which has been designed for the Cassegrain focus of the ALMA 12-m antenna, with the ALMA/ACA 7-m antenna was designed. The beam waveguide system, covering 30–950 GHz, consists of flat mirrors or prisms to modify the boresight tilt angle from the front-end, and recovers more than the half of the sensitivity loss caused by a misalignment between the front-end optics and the 7-m antenna. No mechanical alignment procedure is needed for installation of the beam waveguide system, and thus it does not impact on the maintenance/operation scheme of the front-end system. Beam-pattern measurements in the frequency ranges of ALMA bands 4 (144 GHz), 6 (252 GHz), and 8 (385 GHz) have confirmed that directions of the radiation patterns transmitted to the subreflector are successfully shifted by the beam waveguide system without any serious deformation of the beam. The aperture efficiencies calculated from the measured radiation patterns were determined to be 84.6% at 144 GHz, 86.1% at 252 GHz, and 84.8% at 385 GHz, which are consistent with those of a simulated radiation pattern.
Optical and Near-Infrared Photometric Observation during the Superoutburst of the WZ Sge-Type Dwarf Nova, V455 Andromedae
Authors: Matsui Risako , Uemura Makoto , Arai Akira , Sasada Mahito , Ohsugi Takashi , Yamashita Takuya , Kawabata Koji , Fukazawa Yasushi , Mizuno Tsumefumi , Katagiri Hideaki , Takahashi Hiromitsu , Sato Shuji , Kino Masaru , Yoshida Michitoshi , Shimizu Yasuhiro , Nagayama Shogo , Yanagisawa Kenshi , Toda Hiroyuki , Okita Kiichi , Kawai Nobuyuki 
Published: March 2014

Abstract
We report on optical and infrared photometric observations of a WZ Sge-type dwarf nova, V455 And during a superoutburst in 2007. These observations were performed with the KANATA ($V$, $J$, and $K_{\rm s}$ bands) and MITSuME ($g^\prime$, $R_{\rm C}$, and $I_{\rm C}$ bands) telescopes. Our 6-band simultaneous observations allowed us to investigate the temporal variation of the temperature and the size of the emitting region associated with the superoutburst and short-term modulations, such as early and ordinary superhumps. A hot ($&gt; $11000 K) accretion disk suddenly disappeared when the superoutburst finished, while blackbody emission, probably from the disk, still remained dominant in the optical region with a moderately high temperature ($\sim $8000 K). This indicates that a substantial amount of gas was stored in the disk even after the outburst. This remnant matter may be a sign of an expected mass-reservoir, which can trigger echo outbursts observed in several WZ Sge stars. The color variation associated with superhumps indicates that viscous heating in a superhump source stopped on the way to the superhump maximum, and a subsequent expansion of a low-temperature region made the maximum. The color variation of early superhumps was totally different from that of superhumps: the object was bluest at the early superhump minimum. The temperature of the early superhump light source was lower than that of an underlying component, indicating that the early superhump light source was a vertically expanded low-temperature region at the outermost part of the disk.
Origin of Thermal and Non-Thermal Hard X-Ray Emission from the Galactic Center
Authors: Dogiel Vladimir A. , Chernyshov Dmitrii O. , Yuasa Takayuki , Prokhorov Dmitrii , Cheng Kwong-Sang , Bamba Aya , Inoue Hajime , Ko Chung-Ming , Kokubun Motohide , Maeda Yoshitomo , Mitsuda Kazuhisa , Nakazawa Kazuhiro , Yamasaki Noriko Y. 
Published: March 2014

Abstract
We analyse new results of Chandra and Suzaku Observatories which found a flux of hard X-ray emission from the compact region around Sgr A$^\ast$ ($r$$\sim$ 100 pc). We suppose that this emission is generated by accretion processes onto the central supermassive blackhole when an unbound part of captured stars obtains an additional momentum. As a result a flux of subrelativistic protons is generated near the galactic center which heats the background plasma up to temperatures about 6–10 keV and produces by inverse bremsstrahlung a flux of non-thermal X-ray emission in the energy range above 10 keV.
Suzaku Observations of Abell 1795: Cluster Emission to r200
Authors: Bautz Marshall W. , Miller Eric D. , Sanders Jeremy S. , Arnaud Keith A. , Mushotzky Richard F. , Porter F. Scott , Hayashida Kiyoshi , Henry J. Patrick , Hughes John P. , Kawaharada Madoka , Makishima Kazuo , Sato Mitsuhiro , Tamura Takayuki 
Published: March 2014

Abstract
We report Suzaku observations of the galaxy cluster Abell 1795 that extend to $r_{200}$$\approx$ 2 Mpc, the radius within which the mean cluster mass density is 200 times the cosmic critical density. These observations are the first to probe the state of the intracluster medium in this object at $r$$&gt;$ 1.3 Mpc. We sample two disjoint sectors in the cluster outskirts (1.3 Mpc $\lt$$r$$\lt$ 1.9 Mpc) and detect X-ray emission in only one of them to a limiting (3$ \sigma$) soft X-ray surface brightness of $B_{0.5{\rm }2 {\rm keV}}$$=$ 1.8 $\times$ 10$^{-12} $erg s$^{-1} $cm$^{-2} $deg$^{-2} $, a level less than 20% of the cosmic X-ray background brightness. We trace the run of temperature with radius at $r$$&gt;$ 0.4 Mpc and find that it falls relatively rapidly ($T_{{\rm deprojected}}$$\propto$$r^{-0.9}$), reaching a value about one third of its peak at the largest radius we can measure it. Assuming the intracluster medium is in hydrostatic equilibrium and is polytropic, we find a polytropic index of $\Gamma$$=$ 1.3$^{+0.3}_{-0.2}$ and we estimate a mass of (4.1$^{+0.5}_{-0.3}$) $\times$ 10$^{14} M_{\odot}$ within 1.3 Mpc, somewhat (2.7$ \sigma$) lower than that reported by previous observers. However, our observations provide evidence for departure from hydrostatic equilibrium at radii as small as $r$$\sim$ 1.3 Mpc $\approx r_{500}$ in this apparently regular and symmetrical cluster.
Detection of a Sub-Keplerian Water Maser Disk at the Active Galactic Nucleus of the Galaxy IC 1481
Authors: Mamyoda Koichi , Nakai Naomasa , Yamauchi Aya , Diamond Philip , HurÉ Jean-Marc 
Published: March 2014

Abstract
We present a study of H$_{2}$O maser emission from the LINER, IC 1481, based on single-dish and highly sensitive VLBI observations. The Nobeyama 45-m telescope detected new maser features near the systemic velocity and blue-shifted by 124–205 km s$^{-1}$. In addition, the known features red-shifted by $\approx $97–155 km s$^{-1}$ were monitored. VLBI observations with the High Sensitivity Array (HSA) revealed that the maser features are distributed along a line, with a velocity gradient, strongly suggesting a nearly edge-on molecular gas disk. The radius and thickness of the disk are $r$$=$ 2.8–14.0 pc and 2$H$$=$ 1.5–4.2 pc, respectively, which are the largest among the maser disks detected in active galactic nuclei. The disk is rotating at $V_{{\rm rot}}$$=$ 124–168 km s$^{-1}$, having a large velocity dispersion of $\triangle V$$\approx $ 31 km s$^{-1}$. The rotation curve of the disk is sub-Keplerian ($V_{{\rm rot}}$$\propto$$r^{-0.19 \pm 0.04}$), indicating a massive disk. The disk mass is estimated to be (4.3$ \pm $0.3) $\times$ 10$^{7} M_{\odot }$ and the mass of a putative central black hole is $\lt $10$^{7} M_{\odot }$. The massive disk is gravitationally unstable. A radio continuum source was also detected to be offset from the maser disk by 1.6 pc.
Can Sodium Abundances of A-Type Stars Be Reliably Determined from Na I 5890/5896 Lines?
Authors: Takeda Yoichi , Kang Dong-Il , Han Inwoo , Lee Byeong-Cheol , Kim Kang-Min 
Published: March 2014

Abstract
An extensive non–LTE abundance analysis based on Na i 5890/5896 doublet lines was carried out for a large unbiased sample of $\sim $ 120 A-type main-sequence stars (including 23 Hyades stars) covering a wide $v_{\rm e}$sin $i$ range of $\sim $ 10–300 km s$^{-1}$, with an aim to examine whether the Na abundances in such A dwarfs can be reliably established from these strong Na$\;$i D lines. The resulting abundances ([Na$/$H]$_{58}$), which were obtained by applying the $T_{\rm eff}$-dependent microturbulent velocities of $\xi \sim$ 2–4 km s$^{-1}$ with a peak at $T_{\rm eff}$$\sim $ 8000 K (typical for A stars), turned out to be generally negative with a large diversity (from $\sim-$1 to $\sim $0), while showing a sign of $v_{\rm e}$sin $i$-dependence (decreasing toward higher rotation). However, the reality of this apparently subsolar trend is very questionable, since these [Na$/$H]$_{58}$ are systematically lower by $\sim $0.3–0.6 dex than more reliable [Na$/$H]$_{61}$ (derived from weak Na$\;$I 6154/6161 lines for sharp-line stars). Considering the large $\xi $-sensitivity of the abundances derived from these saturated Na$\;$I D lines, we regard that [Na$/$H]$_{58}$ must have been erroneously underestimated, suspecting that the conventional $\xi $ values are improperly too large, at least for such strong high-forming Na$\;$I 5890/5896 lines, presumably due to the depth-dependence of $\xi $ decreasing with height. The nature of the atmospheric turbulent velocity field in mid-to-late A stars needs to be further investigated before we can determine reliable sodium abundances from these strong resonance D lines.
Oxygen and Light-Element Synthesis by Neutron-Capture Reactions in Metal-Free and Extremely Metal-Poor AGB Stars
Authors: Nishimura Takanori , Aikawa Masayuki , Suda Takuma , Fujimoto Masayuki Y. 
Published: March 2014

Abstract
The metal-free (Population III: Pop. III) and extremely metal-poor (EMP) stars of low- and intermediate-masses experience mixing of hydrogen into the helium convection during the early TP-AGB phase, differently from the metal-rich stars. We have studied nucleosynthesis in the helium convective zone with ${}^{13}$C formed from mixed protons as a neutron source by using a nuclear network from H through S. In the absence or scarcity of pristine metals, neutron-recycling reactions, ${}^{12}$C ($n$, $\gamma$) ${}^{13}$C ($\alpha$, $n$) ${}^{16}$O and also ${}^{16}$O ($n$, $\gamma$) ${}^{17}$O ($\alpha$, $n$) ${}^{20}$Ne promote the synthesis of O and light elements, including their neutron-rich isotopes and the odd atomic number elements. Based on the results, we demonstrate that the peculiar abundance patterns of C through Al observed for the three most iron-deficient, carbon-rich stars can be reproduced in terms of nucleosynthesis in Pop. III, AGB stars in three different mass ranges. We argue that these three stars were born as low-mass members of Pop. III binaries, and later were subjected to surface pollution by mass transfer in the binary systems. It is also shown that AGB nucleosynthesis with hydrogen mixing explains the abundances of C, O, Na, Mg, and Al observed for most of carbon-enhanced EMP (CEMP) stars, including all CEMP-$s$ stars with s-process elements. In addition, the present results are used to single out nucleosynthetic signatures of the early generations of stars other than AGB stars.
Multiwavelength Photon Spectra from Microquasars
Authors: Zhang Jian-Fu , Zhang Li , Fang Jun 
Published: March 2014

Abstract
We have studied multiwavelength photon emission from microquasars based on the framework of a leptonic jet model. In this model, non-thermal photons are produced by synchrotron, relativistic Bremsstrahlung, and angular dependent inverse Compton processes; they suffer a periodic orbital modulation due to the effects of different accretion rates and a variation of the soft photon density at different orbital phases as well as the orbital-phase and angular dependence $\gamma$–$\gamma$ absorption and IC scattering. We applied this model to two possible microquasars, LS 5039 and LS I $+$61 303, and our results can roughly reproduce their observed spectral properties and the variability of these sources.
First Evidence of a Retrograde Orbit of a Transiting Exoplanet HAT-P-7b
Authors: Narita Norio , Sato Bun’ei , Hirano Teruyuki , Tamura Motohide 
Published: March 2014

Abstract
We present the first evidence of a retrograde orbit of a transiting exoplanet HAT-P-7b. The discovery is based on a measurement of the Rossiter–McLaughlin effect with the Subaru HDS during a transit of HAT-P-7b, which occurred on 2008 May 30 UT. Our best-fit model shows that the spin–orbit alignment angle of this planet is $\lambda$$=$$-132.^\circ 6^{+\timeform{10.^\circ 5}}_{-\timeform{16.^\circ3}}$. The existence of such a retrograde planet has been predicted by recent planetary migration models that consider planet–planet scattering processes, or Kozai migration. Our finding provides an important milestone that supports such dynamic migration theories.