bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence from the Extreme-Ultraviolet Imaging Spectrometer for Axial Filament Rotation before a Large Flare
Authors: Williams David R. , Harra Louise K. , Brooks David H. , Imada Shinsuke , Hansteen Viggo H.
Published: March 2014

In this article, we present observations made with the Extreme-ultraviolet Imaging Spectrometer on-board the Hinode solar satellite, of an active region filament in the HeII emission line at 256.32 $Å$. The host active region AR 10930 produces an X-class flare during these observations. We measure Doppler shifts with apparent velocities of up to 20 kms$^{-1}$, which are antisymmetric about the filament length and occur several minutes before the flare’s impulsive phase. This is indicative of a rotation of the filament, which is in turn consistent with expansion of a twisted flux rope due to the MHD helical kink instability. This is the first time that such an observation has been possible in this transition-region line, and we note that the signature observed occurs before the first indications of pre-flare activity in the GOES solar soft X-ray flux, suggesting that the filament begins to destabilise in tandem with a reorganization of the local magnetic field. We suggest that this expansion is triggered by the decrease of magnetic tension around, and/or total pressure above, the filament.
AKARI Far-Infrared Spectroscopic Observations of the Galactic Center Region
Authors: Yasuda Akiko , Kaneda Hidehiro , Nakagawa Takao , Okada Yoko , Kawada Mitsunobu , Murakami Noriko , Takahashi Hidenori , Ootsubo Takafumi
Published: March 2014

We have observed the Quintuplet- and Arches-cluster regions with the Fourier Transform Spectrometer (FTS) of the Far-Infrared Surveyor (FIS) aboard AKARI to investigate the physical conditions of interstellar matter around the clusters. The FIS-FTS mapping data reveal differences in the spatial distribution among the far-infrared [O iii], [N ii], and [C ii] line emissions near the Arches cluster; the emission of an ionic line with a higher ionization potential is distributed closer to the Arches cluster. This clearly indicates that UV photons from the Arches cluster are ionizing the surface of nearby molecular clouds, and penetrating deeper to dissociate the cloud. We have estimated the effective temperature of the Arches cluster to be about 34000 K from the ratio of the [O iii]$/$[N ii] lines.
SDSS J080434.20$+$510349.2: Eclipsing WZ Sge-Type Dwarf Nova with Multiple Rebrightenings
Authors: Kato Taichi , Pavlenko Elena P. , Maehara Hiroyuki , Nakajima Kazuhiro , Andreev Maksim , Shugarov Sergei Yu. , De Ponthière Pierre , Brady Steve , Klingenberg Geir , Shears Jeremy , Imada Akira , Yanagisawa Kenshi
Published: March 2014

We observed the 2006 superoutburst of SDSS J080434.20$+$510349.2 during its plateau phase, rebrightening phase, and post-superoutburst final decline. We found that this object is a grazing eclipsing system with a period of 0.0590048(2)d. Well-defined eclipses were only observed during the late stage of the superoutburst plateau and the depth decreased during the subsequent stages. We determined the superhump period during the superoutburst plateau to be 0.059539(11)d, giving a fractional superhump excess of 0.90(2)%. During the rebrightening and post-superoutburst phases, persisting superhumps have periods longer than those of superhumps during the plateau phase: 0.059632(6)d during the rebrightening phase and 0.05969(4)d during the final fading. This phenomenon is very well in line with the previously known long-period “late superhumps” in GW Lib, V455 And, and WZ Sge. The amplitudes of orbital humps between different states of rebrightenings suggest that these humps do not arise from the classical hot spot, but are more likely to be a result of projection effect in a high-inclination system. There was no clear evidence for an enhanced hot spot during the rebrightening phase. We also studied previously reported “mini-outbursts” in the quiescent state, and found evidence that superhumps were transiently excited during these mini-outbursts. The presence of grazing eclipses and distinct multiple rebrightenings in SDSS J080434.20$+$510349.2 would provide a unique opportunity for understanding the mechanism of rebrightenings in WZ Sge-type dwarf novae.
Observational Appearance of Luminous Relativistic Movers
Authors: Fukue Jun
Published: March 2014

We examine the observational appearance of optically thick luminous gaseous objects that move or rotate at a relativistic speed. In relativistic objects traveling at about the speed of light, Doppler and aberration effects influence their observational appearance. In gaseous objects with a hotter interior, furthermore, there exists a usual limb-darkening effect, which has a direction-dependency, and is therefore affected by the relativistic aberration. In addition, the emitted radiation suffers from a relativistic Doppler boost. Hence, the apparent photosphere of relativistic gaseous objects depends on their velocity and direction as well as the temperature distribution. We have derived the optical depth of the apparent photosphere of such relativistic movers under the plane-parallel approximation, and calculated several typical cases. When the velocity is almost parallel to the line of sight, the relativistic effect on the optical depth becomes important; otherwise, the limb-darkening effect dominates. In the case of a rotating sphere, except for some small fraction in the equatorial direction, the optical depth of the apparent photosphere becomes small due to the relativistic aberration. In the case of a geometrically thin disk, the optical depth becomes large in the left approaching part, whereas it becomes small in the right receding part. In the case of a geometrically thick disk, the projection effect becomes important, and the optical depth is large at the far side, while it is small at the near side. We have also examined light curves of luminous orbiters around a black hole and luminosities and spectra of accretion disks under special relativity, as applications. The light curve of the relativistic orbiter does deviate from a sinusoidal pattern due to the transverse Doppler effect. The pole-on luminosity of accretion disks is enhanced by the limb-dakening effect and reduced by the relativistic one, while the luminosity observed from the inclined direction is reduced by the limb-darkening effect.
Period Change and Possible Magnetic Braking in WY Cancri
Authors: Tian Yongpo , Xiang Fuyuan , Xie Wenli , Tao Xia
Published: March 2014

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

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

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

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

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

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

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

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

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 ($> $11000 K) accretion disk suddenly disappeared when the superoutburst finished, while blackbody emission, probably from the disk, still remained dominant in the optical region with a moderately high temperature ($\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

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

We report Suzaku observations of the galaxy cluster Abell 1795 that extend to $r_{200}$$\approx$ 2 Mpc, the radius within which the mean cluster mass density is 200 times the cosmic critical density. These observations are the first to probe the state of the intracluster medium in this object at $r$$>$ 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}}$$=$ 1.8 $\times$ 10$^{-12} $erg s$^{-1} $cm$^{-2} $deg$^{-2} $, a level less than 20% of the cosmic X-ray background brightness. We trace the run of temperature with radius at $r$$>$ 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

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

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

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

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

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.
Suzaku Observation of the Metallicity Distribution in the Elliptical Galaxy NGC 4636
Authors: Hayashi Katsuhiro , Fukazawa Yasushi , Tozuka Miyako , Nishino Sho , Matsushita Kyoko , Takei Yoh , Arnaud Keith A.
Published: March 2014

NGC 4636, an X-ray bright elliptical galaxy, was observed for 70 ks with Suzaku. Thanks to low background and good energy resolution of the XIS, we succeeded to estimate the foreground Galactic emission accurately, and, for the first time, measure the metal abundance distributions out to $\sim $28${}^\prime$ ($\simeq $140 kpc) for O, Mg, Si, and Fe. The metal abundances are as high as $\gt$1 solar within 4${}^\prime$, and decreases by $\sim $50% from the center toward the outer region. In addition, the O to Fe abundance ratio is about 0.6$\sim $1.0 solar in all analyzed regions, indicating that metal products by SNe II and SNe Ia have mixed and diffused to the outer region of the galaxy. Furthermore, comparing the O and Fe mass distributions with those of NGC 1399, we found the metal mass-to-light ratio (MLR) of NGC 4636 to be 2–3 times larger. Therefore, the metal distributions in NGC 4636 are less extended than those in NGC 1399, possibly due to environmental factors, such as frequency of galaxy interaction. We also found that MLRs of NGC 4636 at 0.1$ r_{180}$ are $\sim $5-times smaller than those of clusters of galaxies, possibly consistent with the correlation between temperature and MLR of other spherically symmetric groups of galaxies. We also confirmed a signature of the resonance scattering of the Fe xvii line in the central region, as reported based on the XMM-Newton RGS observation.
Resonant Excitation of Disk Oscillations in Two-Armed-Deformed Disks and Application to High-Frequency QPOs
Authors: Kato Shoji
Published: March 2014

In previous papers we showed that in one-armed deformed disks, p-mode and g-mode oscillations are resonantly excited by horizontal resonance, and applied it to high-frequency quasi-periodic oscillations (QPOs) observed in low-mass X-ray binaries. In that model, the observed time variation of kHz QPOs is regarded as being the result of a time-dependent precession of the deformation. In this paper we consider another possible cause of the time variation of kHz QPOs. That is, we demonstrate that in two-armed deformed disks, p-mode and g-mode oscillations are excited by a vertical resonance, not by a horizontal resonance (horizontal resonance dampens them). Furthermore, we show that in the case of a vertical resonance, the frequencies of excited disk oscillations can vary with time if the vertical disk structure changes with time. A brief application of these results to the time variation of observed kHz QPOs is discussed.
Secular Increase of the Astronomical Unit: a Possible Explanation in Terms of the Total Angular-Momentum Conservation Law
Authors: Miura Takaho , Arakida Hideyoshi , Kasai Masumi , Kuramata Shuichi
Published: March 2014

We give an idea and order-of-magnitude estimations to explain a recently reported secular increase of the Astronomical Unit ($AU$) by Krasinsky and Brumberg (2004, Celest. Mech. Dyn. Astron., 90, 267). The idea proposed is analogous to tidal acceleration in the Earth–Moon system, which is based on conservation of the total angular momentum; we apply this scenario to the Sun–planets system. Assuming the existence of some tidal interactions that transfer the rotational angular momentum of the Sun, and using a reported value of the positive secular trend in the Astronomical Unit, $\displaystyle\frac{d}{dt}{AU}$$=$ 15$ \pm $4 (m cy$^{-1}$), the suggested change in the period of rotation of the Sun is about 21 ms cy$^{-1}$ in the case that the orbits of the eight planets have the same “expansion rate.” This value is sufficiently small, and at present it seems there are no observational data that exclude this possibility. The effects of a change in the Sun’s moment of inertia is also investigated. It is pointed out that a change in the moment of inertia due to radiative mass loss by the Sun may be responsible for the secular increase of $AU$, if orbital “expansion” is happening only in the inner-planets system. Although the existence of some tidal interactions is assumed between the Sun and the planets, concrete mechanisms of angular-momentum transfer are not discussed in this paper, which remain to be pursued as future investigations.
Spectral Analyses of the Nearest Persistent Ultraluminous X-Ray Source M 33 X-8
Authors: Weng Shan-Shan , Wang Jun-Xian , Gu Wei-Min , Lu Ju-Fu
Published: March 2014

We provide a detailed analysis of 12 XMM observations of the nearest persistent extragalactic ultraluminous X-ray source (ULX), M33 X-8. No significant spectral evolution has been detected for the period of the observations, and therefore we combine the individual observations to increase the signal-to-noise ratio for a spectral fitting. The combined spectra are best fitted by a self-consistent $p$-free disk plus power-law component model with $p$$=$ 0.571$_{-0.030}^{+0.032}$, $kT_{\rm in}$ (inner disk temperature) $=$ 1.38$_{-0.08}^{+0.09}$ keV, and the flux ratio of the $p$-free disk component to the power-law component being 0.63 : 0.37 in the 0.3–10 keV band. The fitting indicates that the black hole in M 33 X-8 is of $\sim $10$ M_{\rm\odot}$, and accretes at a super-Eddington rate ($\sim $1.5$ L_{\rm Edd}$); also, the phase of the accretion disk is close to that of a slim disk ($p$$=$ 0.5). We report, for the first time, that an extra power-law component is required in addition to the $p$-free disk model for ULXs. In super-Eddington cases, the power-law component may possibly result from an optically thin inner region of the disk or a Comptonized corona, similar to that of a standard thin disk.
Advection-Dominated Accretion Disks: Geometrically Slim or Thick?
Authors: Gu Wei-Min , Xue Li , Liu Tong , Lu Ju-Fu
Published: March 2014

We revisit the vertical structure of black-hole accretion disks in spherical coordinates. By comparing the advective cooling with the viscous heating, we show that advection-dominated disks are geometrically thick, i.e., with a half-opening angle of $\Delta\theta$$>$ 2$\pi/$5, rather than being slim, as supposed previously in the literature.
Suzaku Observations across the Cygnus Loop from the Northeastern to the Southwestern Rim
Authors: Kimura Masashi , Tsunemi Hiroshi , Katsuda Satoru , Uchida Hiroyuki
Published: March 2014

We have observed the Cygnus Loop from the northeast (NE) rim to the southwest (SW) rim using Suzaku in 10 pointings just north of previous XMM-Newton observations. The observation data obtained were divided into 45 rectangular regions where the width was configured so that each region would hold 8000–12000 photons. The spectrum acquired from each region was fitted either with one-$kT_{\rm e}$-component non-equilibrium ionization (NEI) model or with a two-$kT_{\rm e}$-component NEI model. The two-$kT_{\rm e}$-component model yielded a significantly better fit in almost all of the non-rim regions. Judging from the abundances and the flux, the high-$kT_{\rm e}$-component (0.4–0.8 keV) must be the ejecta origin, while the low-$kT_{\rm e}$-component ($\sim$0.3 keV) comes from the swept-up matter. We found that the swept-up matter shell is very thin just southwest of center of the Loop. Together with previous observations, we estimated the diameter of this thin shell region to be 1$^{\circ}$. We also found that the ejecta distributions were asymmetric to the geometric center: the ejecta of O, Ne, and Mg were distributed more in the NE, while the ejecta of Si and Fe were distributed more in the SW of the Cygnus Loop. We calculated the masses for various metals and estimated the origin of the Cygnus Loop as the a 12–15$\,M_\odot$ core-collapse explosion.
Modeling and Reproducibility of Suzaku HXD PIN/GSO Background
Authors: Fukazawa Yasushi , Mizuno Tsunefumi , Watanabe Shin , Kokubun Motohide , Takahashi Hiromitsu , Kawano Naomi , Nishino Sho , Sasada Mahito , Shirai Hirohisa , Takahashi Takuya , Umeki Yudai , Yamasaki Tomonori , Yasuda Tomonori , Bamba Aya , Ohno Masanori , Takahashi Tadayuki , Ushio Masayoshi , Enoto Teruaki , Kitaguchi Takao , Makishima Kazuhiro , Nakazawa Kazuo , Uehara Yuichi , Yamada Shin’ya , Yuasa Takayuki , Isobe Naoki , Kawaharada Madoka , Tanaka Takaaki , Tashiro Makoto S. , Terada Yukikatsu , Yamaoka Kazutaka
Published: March 2014

Suzaku Hard X-ray Detector (HXD) achieved the lowest background level than any other previously or currently operational missions sensitive in the energy range of 10–600 keV, by utilizing PIN photodiodes and GSO scintillators mounted in BGO active shields to reject particle background and Compton-scattered events as much as possible. Because it does not have an imaging capability nor rocking mode for the background monitor, the sensitivity is limited by the reproducibility of the non X-ray background (NXB) model. We modeled the HXD NXB, which varies with time as well as other satellites with a low-Earth orbit, by utilizing several parameters, including particle monitor counts and satellite orbital/attitude information. The model background is supplied as an event file in which the background events are generated by random numbers, and can be analyzed in the same way as the real data. The reproducibility of the NXB model depends on the event selection criteria (such as cut-off rigidity and energy band) and the integration time, and the 1$\sigma$ systematic error is estimated to be less than 3% (PIN 15–40 keV) and 1% (GSO 50–100 keV) for more than 10 ks exposure.
Design and In-Orbit Performance of the Suzaku Wide-Band All-Sky Monitor
Authors: Yamaoka Kazutaka , Endo Akira , Enoto Teruaki , Fukazawa Yasushi , Hara Ryuji , Hanabata Yoshitaka , Hong Soojing , Kamae Tsuneyoshi , Kira Chie , Kodaka Natsuki , Kokubun Motohide , Maeno Shouta , Makishima Kazuo , Miyawaki Ryohei , Morigami Kouichi , Murakami Toshio , Nakagawa Yujin E. , Nakazawa Kazuhiro , Ohmori Norisuke , Ohno Masanori , Onda Kaori , Sato Goro , Sonoda Eri , Sugita Satoshi , Suzuki Masanobu , Suzuki Motoko , Tajima Hiroyasu , Takahashi Tadayuki , Takahashi Takuya , Tanaka Hiroki , Tamagawa Tohru , Tashiro Makoto S. , Terada Yukikatsu , Uehara Takeshi , Urata Yuji , Yamauchi Makoto , Yoshida Atsumasa , Hurley Kevin , Pal’shin Valentin , Sakamoto Takanori , Cummings Jay
Published: March 2014

The Suzaku Wide-band All-sky Monitor (WAM) consists of thick BGO anti-coincidence shields of the Hard X-ray Detectors (HXD). It views about half of the sky and has a geometrical area of 800 cm$^2$ per sdide and an effective area of 400 cm$^2$, even at 1 MeV. Hence, the WAM can provide unique opportunities to detect high-energy emission from GRBs and solar flares in the sub-MeV to MeV range. The WAM has detected more than 400 GRBs and 100 solar flares since its launch. This paper describes the in-flight performance of the HXD/WAM during the initial two years of operations, including the in-flight energy response, spectral and timing capabilities, and in-orbit background.
Deconvolution of Images Taken with the Suzaku X-Ray Imaging Spectrometer
Authors: Sugizaki Mutsumi , Kamae Tuneyoshi , Maeda Yoshitomo
Published: March 2014

We present a non-iterative method to deconvolve the point spread function (PSF) from images taken with the Suzaku X-ray Imaging Spectrometer (XIS). The method is optimized for analyses of extended sources with high photon statistics. Suzaku has four XIS detectors, each with its own X-ray CCD and X-Ray Telescope (XRT), and has been providing opportunities in spatially-resolved analyses of extended objects. The detectors, however, suffer from broad and position-dependent PSFs with their typical half-power diameter (HPD) of $\sim$110$^{\prime\prime}$. The present method is intended to recover spatial resolution to $\sim$15$^{\prime\prime}$ over a dynamic range of around 1:100 in the brightness without assuming any source model. Our deconvolution proceeds in two steps: An XIS image is multiplied by the inverse response matrix, calculated from its PSF after rebinning CCD pixels to larger-size tiles (typically 6$^{\prime\prime}$$\times$ 6$^{\prime\prime}$). The inverted image is then adaptively smoothed. The PSF is modeled on a ray-tracing program and an observed point-source image. The method has been applied to images of Centaurus A, PSR B1509$-$58 and RCW 89 taken by one XIS (XIS 1). The results have been compared with images taken with Chandra to conclude that the spatial resolution has been recovered to $\sim$20$^{\prime\prime}$ down to regions where the surface brightness is about 1:50 of the brightest tile. We believe the spatial resolution and the dynamic range can be improved with higher fidelity PSF modeling and higher precision pointing information.
A New Set of Variables in the Three-Body Problem
Authors: Kuwabara Kenji Hiro , Tanikawa Kiyotaka
Published: March 2014

We propose a set of variables of the general three-body problem both for two-dimensional and three-dimensional cases. The variables are ($\lambda, \theta, \Lambda, \Theta, k, \omega$), or equivalently ($\lambda, \theta, L, \dot{I},k,\omega)$ for the two-dimensional problem, and ($\lambda, \theta, L, \dot{I}, k, \omega, \phi, \psi$) for the three-dimensional problem. Here, ($\lambda, \theta$) and ($\Lambda, \Theta)$ specify the positions in the shape spheres in the configuration and momentum spaces, $k$ is the virial ratio, $L$ is the total angular momentum, $\dot{I}$ is the time derivative of the moment of inertia, and $\omega, \phi$, and $\psi$ are the Euler angles to bring the momentum triangle from the nominal position to a given position. This set of variables defines a shape space  of the three-body problem. This is also used as an initial-condition space. The initial condition of the so-called free-fall three-body problem is ($\lambda, \theta, k =$ 0, $L =$ 0, $\dot{I} =$ 0, $\omega =$ 0). We show that the hyper-surface $\dot{I} =$ 0 is a global surface of section.
Suzaku Constraints on Soft and Hard Excess Emissions from Abell 2199
Authors: Kawaharada Madoka , Makishima Kazuo , Kitaguchi Takao , Okuyama Sho , Nakazawa Kazuhiro , Fukazawa Yasushi
Published: March 2014

The nearby ($z =$ 0.03015) cluster of galaxies Abell 2199 was observed by Suzaku in X-rays, with five pointings for $\sim$ 20 ks each. From the XIS data, the temperature and metal abundance profiles were derived out to $\sim$ 700 kpc (0.4 times the virial radius). Both of these quantities decrease gradually from the center to peripheries by a factor of $\sim$ 2, while the oxygen abundance tends to be flat. The temperature within 12${}^\prime$ ($\sim$ 430 kpc) is $\sim$ 4 keV, and the 0.5–10 keV X-ray luminosity integrated up to 30${}^\prime$ is (2.9$\pm$0.1) $\times$ 10$^{44}$erg s$^{-1}$, in agreement with previous XMM-Newton measurements. Above this thermal emission, no significant excess was found either in the XIS range below $\sim$ 1 keV, or in the HXD-PIN range above $\sim$ 15 keV. The 90%-confidence upper limit on the emission measure of an assumed 0.2 keV warm gas is (3.7–7.5) $\times$ 10$^{62}$cm$^{-3}$arcmin$^{-2}$, which is 3.7–7.6 times tighter than the detection reported with XMM-Newton. The 90%-confidence upper limit on the 20–80 keV luminosity of any power-law component is 1.8 $\times$ 10$^{43}$erg s$^{-1}$, assuming a photon index of 2.0. Although this upper limit does not reject the possible 2.1$\sigma$ detection by the BeppoSAX PDS, it is a factor of 2.1 tighter than that of the PDS if both are considered upper limits. The non-detection of the hard excess can be reconciled with the upper limit on diffuse radio emission, without invoking very low magnetic fields ($<$ 0.073$\mu$G) which were suggested previously.
Study of the Large-Scale Temperature Structure of the Perseus Cluster with Suzaku
Authors: Nishino Sho , Fukazawa Yasushi , Hayashi Katsuhiro , Nakazawa Kazuhiro , Tanaka Takaaki
Published: March 2014

We report on a study of the large-scale temperature structure of the Perseus cluster with Suzaku, using observational data of four pointings of the 30$^{\prime}$ offset regions, together with data from the central region. Thanks to the Hard X-ray Detector (HXD-PIN: 10–60 keV), Suzaku can determine the temperature of hot galaxy clusters. We performed a spectral analysis by considering the temperature structure and the collimator response of the PIN correctly. As a result, we found that the upper limit of the temperature in the outer region is $\sim$14 keV, and an extremely hot gas, which was reported for RX J1347.5$-$1145 and Abell 3667, was not found in the Perseus cluster. This indicates that the Perseus cluster has not recently experienced a major merger.
Discovery of Multiple High-Velocity Narrow Circumstellar NaI D Lines in Nova V1280 Sco
Authors: Sadakane Kozo , Tajitsu Akito , Mizoguchi Sahori , Arai Akira , Naito Hiroyuki
Published: March 2014

We discovered multiple high-velocity (ranging from $-$900 to $-$650 km s$^{-1}$) and narrow (FWHM $\sim$ 15 km s$^{-1}$) absorption components corresponding to both the D2 and the D1 lines of Na I on a high-dispersion spectrum of V1280 Sco, observed on 2009 May 9 (UT), 814 d after the V band maximum. Subsequent observations carried out on 2009 June and July confirmed at least 11 distinct absorption components in both systems. Some components had deepened during the two-month period while their HWHMs and wavelengths remained nearly constant. We suggest that these high-velocity components originated in cool clumpy gas clouds moving on the line-of-sight, produced during interactions between pre-existing cool circumstellar gas and high-velocity gas ejected in the nova explosion. The optical region spectrum of V1280 Sco in 2009 is dominated by the continuum radiation, and exhibits no forbidden line characterizing the nebular phase of typical novae. Permitted Fe II lines show doubly peaked emission profiles, and some strong Fe II lines are accompanied by a blue-shifted ($\sim -$ 255 km s$^{-1}$) absorption component. However, no high-velocity and narrow components corresponding to those of Na I could be detected in Fe II lines nor in the Balmer lines. The 255 km s$^{-1}$ low-velocity absorption component most probably originates in the wind from the nova.