bluuebunny/crossref_metadata_2025_split huggingface dataset:
Astrometry of AGB Variables with VERA: Annual Parallax and the Orbit of SY Sculptoris in the Galaxy
Authors: Nyu Daisuke , Nakagawa Akiharu , Matsui Makoto , Imai Hiroshi , Sofue Yoshiaki , Omodaka Toshihiro , Kurayama Tomoharu , Kamohara Ryuichi , Hirota Tomoya , Honma Mareki , Shibata Katsunori M. , Kobayashi Hideyuki , Iwadate Kenzaburo , Miyaji Takeshi 
Published: March 2014

Abstract
We report on the results of astrometric observations of H$_{2}$O masers toward a Mira variable, SY Sculptoris (SY Scl), with the VLBI Exploration of Radio Astrometry (VERA) from 2006 October to 2008 October. We determined that SY Scl's annual parallax is 0.75$\ \pm\ $0.03 mas, corresponding to a distance of 1.33$\ \pm\ $0.05 kpc. SY Scl is 1.3 kpc south of the Galactic plane and moves approximately south from the plane with a velocity of 63$\ \pm\ $2 km s$^{-1}$ with respect to the LSR. From the present position and motion, we calculated SY Scl's orbit for the last 1 Gyr based on a parametrized model of the Galactic gravitational potential. SY Scl has an orbit as a member of the Galactic thick disk stars. Subtracting the averaged absolute proper motions of masers, we derived an internal motion of H$_2$O masers in SY Scl. The kinematics of the masers is consistent with motion in a single plane. The masers around SY Scl were found to be distributed in an area of 70 AU $\times$ 80 AU, corresponding to 15 times as large as the stellar photosphere diameter of 5 AU. Based on the measured distance and apparent magnitude of SY Scl, we find the absolute magnitude of SY Scl to be $M_K$$=$$-$8.07$\ \pm\ $0.08 mag. This is approximately consistent with the value of $-$8.09$\ \pm\ $0.07 mag, which was derived from the Galactic Mira period–luminosity relation (2008, MNRAS, 386, 313).
An Implicit Scheme for Ohmic Dissipation with Adaptive Mesh Refinement
Authors: Matsumoto Tomoaki 
Published: March 2014

Abstract
An implicit method for the ohmic dissipation is proposed. The proposed method is based on the Crank–Nicolson method and exhibits second-order accuracy in time and space. The proposed method has been implemented in the SFUMATO adaptive mesh refinement (AMR) code. The multigrid method on the grids of the AMR hierarchy converges the solution. The convergence is fast but depends on the time step, resolution, and resistivity. Test problems demonstrated that decent solutions are obtained even at the interface between fine and coarse grids. Moreover, the solution obtained by the proposed method shows good agreement with that obtained by the explicit method, which required many time steps. The present method reduces the number of time steps, and hence the computational costs, as compared with the explicit method.
Effect of Irradiation on the Disk of the Epsilon Aurigae System
Authors: Takeuti Mine 
Published: March 2014

Abstract
The epsilon Aurigae system consists of a luminous F star and a dusty disk surrounding an unseen object. The obscuring body for the eclipse, which occurs every 27 years, is the dusty disk. Light-variation and spectroscopic features are affected by the physical properties of the disk. To study the properties of the disk, a simplified model including the irradiation of the F star and the rotation of the disk is presented. The maximum temperature depends on the transmissivity of the edge toward the F star, and the heat capacity of irradiated portion determines the temperature of the dark side of disk. The large heat capacity of the edge produces remarkable asymmetry on the temperature of the edge, and also on the thickness of the irradiated edge. The observed asymmetry of the light curve and the absorption lines is comparable to the properties of the rotating-disk model.
The Millimeter Sky Transparency Imager (MiSTI)
Authors: Tamura Yoichi , Kawabe Ryohei , Kohno Kotaro , Fukuhara Masayuki , Momose Munetake , Ezawa Hajime , Kuboi Akihito , Sekiguchi Tomohiko , Kamazaki Takeshi , Vila-VilarÓ Baltasar , Nakagawa Yuki , Okada Norio 
Published: March 2014

Abstract
The Millimeter Sky Transparency Imager (MiSTI) is a small millimeter-wave scanning telescope with a 25-cm diameter dish operating at 183 GHz. MiSTI is installed at Atacama, Chile, and it measures emission from atmospheric water vapor and its fluctuations to estimate atmospheric absorption in the millimeter to submillimeter range. MiSTI observes the water vapor distribution at a spatial resolution of 0$^\circ\!\!\!.$5, and it is sensitive enough to detect an excess path length of $\lesssim\ $0.05 mm for an integration time of 1 s. By comparing the MiSTI measurements with those by a 220 GHz tipper, we validated that the 183 GHz measurements of MiSTI are correct, down to the level of any residual systematic errors in the 220 GHz measurements. Since 2008, MiSTI has provided real-time (every 1 hr) monitoring of the all-sky opacity distribution and atmospheric transmission curves in the (sub)millimeter through the internet, allowing us to know the (sub)millimeter sky conditions at Atacama.
Rotation Modulations and Distributions of the Flare Occurrence Rates on the Surface of Five UV Ceti Type Stars
Authors: Dal Hasan Ali , Evren Serdar 
Published: March 2014

Abstract
In this study, we considered stellar spots, stellar flares, and also the relation between these two magnetic proccesses that take place on UV Cet stars. In addition, the hypothesis about slow flares described by Gurzadyan (1986 Ap&SS, 125, 127) was investigated. All of these discussions were based on the results of three years of observations of UV Cet-type stars: AD Leo, EV Lac, V1005 Ori, EQ Peg, and V1054 Oph. First of all, the results show that stellar spot activity occurs on the stellar surface of EV Lac, V1005 Ori, and EQ Peg, while AD Leo does not show any short-term variability and V1054 Oph does not exhibit any variability. We report on new ephemerides for EV Lac, V1005 Ori, and EQ Peg, obtained from time-series analyses. The phases, computed at intervals of 0.10 phase length, where the mean flare occurence rates to obtain maximum amplitude; also, the phases of rotational modulation were compared in order to investigate whether there is any longitudinal relation between stellar flares and spots. Although the results show that flare events are related with spotted areas on stellar surfaces during some of the observing seasons, we did not find any clear correlation among them. Finally, it was tested whether slow flares are fast flares occurring on the opposite side of the stars according to the direction of the observers, as mentioned in a hypothesis developed by Gurzadyan (1986). The flare occurence rates reveal that both slow and fast flares can occur in any rotational phases. The flare occurence rates of both fast and slow flares vary in the same way along the longitudes for all program stars. These results are not expected based on the case mentioned in the hypothesis.
Early Results of the 3 mm Spectral Line Survey toward the Lynds 1157 B1 Shocked Region
Authors: Sugimura Mika , Yamaguchi Takahiro , Sakai Takeshi , Umemoto Tomofumi , Sakai Nami , Takano Shuro , Aikawa Yuri , Hirano Naomi , Liu Sheng-Yuan , Millar T. J. , Nomura Hideko , Su Yu-Nung , Takakuwa Shigehisa , Yamamoto Satoshi 
Published: March 2014

Abstract
We have conducted a sensitive 3 mm observation toward the shocked region, Lynds 1157 B1, which is an interaction spot between a molecular outflow and its ambient gas. We have successfully detected the CH$_3$CHO, HCOOCH$_3$, and HCOOH lines, as well as the CH$_2$DOH line. The abundances of these molecules relative to CH$_3$OH are found to be lower than those in the low-mass star-forming core, IRAS 16293$-$2422. Since these molecules are thought to evaporate from grain mantles, the observational results mean that complex molecules are less abundant in grain mantles residing in the ambient cloud surrounding a prestellar/protostellar core. Instead, efficient formation of the complex organic species and deuterated species should take place in a prestellar/protostellar core. The present result verifies the importance of an unbiased line survey of this source.
Absorption-Line Survey of H$_3^\textbf{+}$ toward the Galactic Center Sources. III. Extent of Warm and Diffuse Clouds
Authors: Goto Miwa , Usuda Tomonori , Geballe Thomas R. , Indriolo Nick , Mccall Benjamin J. , Henning Thomas , Oka Takeshi 
Published: March 2014

Abstract
We present a follow-up observation on Geballe and Oka (2010, ApJ, 709, L70), who found high column densities of H$_3^+$ $\sim$ 100 pc apart from the Galactic center on the lines of sight to 2MASS J17432173$-$2951430 (J1743) and 2MASS J17470898$-$2829561 (J1747). The wavelength coverages on these sightlines have been extended in order to observe two key transitions of H$_3^+$ — $R$(3, 3)$^l$ and $R$(2, 2)$^l$ — which constrain the temperature and density of the environment. The profiles of the H$_3^+$ $R$(3, 3)$^l$ line, which is due only to gas in the Galactic center, closely match the differences between the H$_3^+$ $R$(1, 1)$^l$ and CO line profiles, just as they do for previously studied sightlines in the Galactic center. Absorption in the $R$(2, 2)$^l$ line of H$_3^+$ is present in J1747 at velocities of between $-$60 and $+$100 km s$^{-1}$. This is the second clear detection of this line in the interstellar medium after GC IRS 3 in the Central cluster. The temperature of the absorbing gas in this velocity range is 350 K, significantly warmer than that of diffuse clouds in other parts of the Central Molecular Zone. This indicates that the absorbing gas localizes on the Sgr B molecular cloud complex. The warm and diffuse gas revealed by Oka et al. (2005, ApJ, 632, 882) apparently extends to $\sim$100 pc, but there is a hint that its temperature is somewhat lower in the line of sight to J1743 than elsewhere in the Galactic center. The observation of H$_3^+$ toward J1747 is compared with the recent Herschel observation of H$_2$O$^+$ toward Sgr B2, and their chemical relation and remarkably similar velocity profiles are discussed.
Photopolarimetric Monitoring of Blazars in the Optical and Near-Infrared Bands with the Kanata Telescope. I. Correlations between Flux, Color, and Polarization
Authors: Ikejiri Yuki , Uemura Makoto , Sasada Mahito , Ito Ryosuke , Yamanaka Masayuki , Sakimoto Kiyoshi , Arai Akira , Fukazawa Yasushi , Ohsugi Takashi , Kawabata Koji S. , Yoshida Michitoshi , Sato Shuji , Kino Masaru 
Published: March 2014

Abstract
We report on the correlation between the flux, color, and polarization variations on time scales of days–months in blazars, and discuss their universal aspects. We performed monitoring of 42 blazars in the optical and near-infrared bands from 2008 to 2010 using TRISPEC attached to the ``Kanata'' 1.5-m telescope. We found that 28 blazars exhibited ``bluer-when-brighter'' trends in their whole or a part of time-series data sets. This corresponds to 88% of objects that were observed for $\gt\ $10 days. Thus, our observation unambiguously confirmed that the ``bluer-when-brighter'' trend is common in the emission from blazar jets. This trend was apparently generated by a variation component with a constant and relatively blue color and an underlying red component. Prominent short-term flares on time scales of days–weeks tended to exhibit a spectral hysteresis; their rising phases were bluer than their decay phases around the flare maxima. In contrast to the strong flux–color correlation, the correlation of the flux and polarization degree was relatively weak; only 10 objects showed significant positive correlations. Rotations of polarization were detected only in three objects: PKS 1510$-$089, 3C 454.3, and PKS 1749$+$096, and possibly in S5 0716$+$714. We also investigated the dependence of the degree of variability on the luminosity and the synchrotron peak frequency, $\nu _{\rm peak}$. As a result, we found that lower luminosity and higher $\nu _{\rm peak}$ objects had smaller variations in their amplitudes both in the flux, color, and polarization degree. Our observation suggests the presence of several distinct emitting sources, which have different variation time-scales, colors, and polarizations. We propose that the energy injection by, for example, internal shocks in relativistic shells is a major factor for blazar variations on time scales of both days and months.
Annual Parallax Measurements of an Infrared Dark Cloud, MSXDC G034.43+00.24 with VERA
Authors: Kurayama Tomoharu , Nakagawa Akiharu , Sawada-Satoh Satoko , Sato Katsuhisa , Honma Mareki , Sunada Kazuyoshi , Hirota Tomoya , Imai Hiroshi 
Published: March 2014

Abstract
We have measured the annual parallax of the H$_{2}$O maser source associated with an infrared dark cloud, MSXDC G034.43$+$00.24, from observations with VERA (VLBI Exploration of Radio Astrometry). The parallax is 0.643$\ \pm\ $0.049 mas, corresponding to a distance of 1.56$^{+0.12}_{\-0.11}\ $kpc. This value is less than half of the previous kinematic distance of 3.7 kpc. We revised the core-mass estimates of MSXDC G034.43$+$00.24, based on the virial masses, LTE masses and dust masses, and showed that the core masses decrease from the previous estimations of $\sim\ $1000$\ M_\odot$ to hundreds of $\ M_\odot$. The spectral type derived from the luminosity also changes from O9.5 to B1 in the case of MM1. This spectral type is still consistent with that of the massive star. The radial velocity derived from the flat rotation model is smaller than the observed velocity, which corresponds to a peculiar motion of $\sim\ $40 km s$^{-1}$ in the line-of-sight direction.
X-Ray Spectrum of a Peculiar Supernova Remnant, G 359.1-0.5
Authors: Ohnishi Takao , Koyama Katsuji , Tsuru Takeshi Go , Masai Kuniaki , Yamaguchi Hiroya , Ozawa Midori 
Published: March 2014

Abstract
We present Suzaku results of a supernova remnant (SNR), G 359.1$-$0.5, in the direction of the Galactic center region. From the SNR, we have found prominent K-shell lines of highly ionized Si and S ions, together with unusual structures at 2.5–3.0 and 3.1–3.6 keV. No canonical SNR plasma model, in either ionization equilibrium or under-ionization, can explain the structures. The energies and shapes of the structures are similar to those of the radiative transitions of free electrons to the K-shell of He-like Si and S ions (radiative recombination continuum: RRC). The presence of strong RRC structures indicates that the plasma is in over-ionization. In fact, the observed spectrum has been well-fitted with an over-ionized plasma model. The best-fit electron temperature of 0.29 keV is far smaller than the ionization temperature of 0.77 keV, which means that G 359.1$-$0.5 is in an extreme condition of over-ionization. We report some cautions on the physical parameters, and comment about possible origins for the over-ionized plasma.
K-Shell Emission of Neutral Iron Line from Sagittarius B2 Excited by Subrelativistic Protons
Authors: Dogiel Vladimir , Chernyshov Dmitrii , Koyama Katsuji , Nobukawa Masayoshi , Cheng Kwong-Sang 
Published: March 2014

Abstract
We investigated the emission of the K$\alpha$ iron line from massive molecular clouds in the galactic center (GC). We assumed that at present the total flux of this emission consists of a time-variable component generated by primary X-ray photons ejected by Sagittarius A$^\ast$ (Sgr A$^\ast$) in the past, and a relatively weak quasi-stationary component excited by the impact of protons that were generated by star accretion onto the central black hole. The level of background emission was estimated from a rise of the 6.4 keV line intensity in the direction of several molecular clouds, which we interpreted as being a stage when the X-ray front ejected by Sgr A$^\ast$ entered into these clouds. Regarding the 6.4 keV emission before this intensity jump, we interpreted it as emission generated by subrelativistic cosmic rays there. The cross-section of K$\alpha$ vacancies produced by protons differs from that of electrons or X-rays. Therefore, we expect that this processes can be distinguished from an analysis of the equivalent width of the iron line; also, the time variations of the width can be predicted. The line intensity from the clouds depends on their distance from Sgr A$^\ast$ and the coefficient of spatial diffusion near the galactic center. We expect that in a few years the line intensity for the cloud G 0.11$-$0.11, which is relatively close to Sgr A$^\ast$, will decrease to a level of $\lesssim\ $10% from its present value. For the cloud Sagittarius B2 (Sgr B2) the situation is more intricate. If the diffusion coefficient is $D$$\gtrsim$ 10$^{27}\ $cm$^{2}\ $s$^{-1}$, the expected stationary flux should be about 10% of its level in 2000. In the opposite case the line intensity from Sgr B2 should drop down to zero because the protons do not reach the cloud.
Running Umbral Waves Observed with Hinode
Authors: Liang Hongfei , Ma Li , Yang Rujuan , Li Haidong , Zhao Li 
Published: March 2014

Abstract
Observations of the main sunspot of NOAA 10953 were carried out with the Solar Optical Telescope aboard Hinode with the line Ca II H on 2007 April 30. The high-cadence (up to 10 s) Ca II H intensity images permit us to elaborate on the nature of umbral oscillations. It is found there are 19 wave sources within the sunspot and 82 running umbral waves that periodically appear at the wave sources, and propagate outward while forming ellipses or partial arcs. Due to their own expansion, the running waves become more diffused, and eventually disappear at the edge of the umbra. On the basis of the time-interval distribution between adjacent running waves being centered close to 144 s, we observed an approximate oscillation period of 142 s. By tracing the fronts of the running waves, the propagation speed of the running waves ranges from 30 to 45 km s$^{-1}$. The distribution for all running waves has an average propagation speed of $\sim$ 37.4 km s$^{-1}$. Furthermore, we have found an interesting phenomenon that implies there may be interaction of a microflare with some running umbral waves.
A New Method of Dark-Current Estimation for Diffuse Sky Measurements with the AKARI Infrared Camera
Authors: Tsumura Kohji , Wada Takehiko 
Published: March 2014

Abstract
We developed a new method for estimating the dark current of near-infrared (NIR) data from the Infra-Red Camera (IRC) aboard the AKARI satellite. The existing method of dark-current estimation is insufficient because the dark current is enhanced by charged particles hitting the detector in the South Atlantic Anomaly (SAA). We could trace this dark-current drift even during astronomical observations by monitoring the dark current in the masked region on the focal plane of IRC. We analyzed approximately 4500 dark frames, and found a relation in the integrated dark charge between the masked region and the exposed one of the detector array. Using this relation, we can estimate the integrated dark charge at each pixel from the average integrated dark charge in the masked region even during astronomical observations. Residuals in our new method were shown to be approximately 1 ADU (corresponding to 3 nW m$^{-2}$sr$^{-1}$ for the N2 band), even for the SAA-enhanced case, which is better than those in any existing methods by five or more times.
Temperature Variations of Cold Dust in the Triangulum Galaxy M 33
Authors: Komugi Shinya , Tosaki Tomoka , Kohno Kotaro , Tsukagoshi Takashi , Nakanishi Kouichiro , Sawada Tsuyoshi , Kawabe Ryohei , Ezawa Hajime , Kuno Nario , Onodera Sachiko , Tamura Yoichi , Wilson Grant W. , Yun Min S. , Scott Kimberly S. , Perera Thushara A. , Austermann Jason E. , Hughes David H. , Aretxaga Itziar , Tanaka Kunihiko , Muraoka Kazuyuki , Miura Rie , Egusa Fumi 
Published: March 2014

We present wide-field 1.1 mm continuum imaging of the nearby spiral galaxy M 33, conducted with the AzTEC bolometer camera on ASTE. We show that the 1.1 mm flux traces the distribution of dust with $T$ $\sim$ 20 K. Combined with far-infrared imaging at 160$\ \mu$m, we derived the dust temperature distribution out to a galactic radius of $\sim$ 7 kpc with a spatial resolution of $\sim$ 150 pc. Although the 1.1 mm flux was observed predominantly near star-forming regions, we found a smooth radial temperature gradient declining from $\sim$ 20 K to $\sim$ 13 K consistent with recent results from the Herschel satellite. Further comparisons of individual regions show a strong correlation between the cold dust temperature and the $K_{\rm S}$ band brightness, but not with the ionizing flux. The observed results imply that the dominant heating source of cold dust at few hundred parsec scales is due to non-OB stars, even when associated with star-forming regions.
Trajectory of HAYABUSA Reentry Determined from Multisite TV Observations
Authors: Ueda Masayoshi , Shiba Yasuo , Yamamoto Masa-yuki , Fujita Kazuhisa , Watanabe Jun-ichi , Sato Mikiya , Abe Shinsuke , Kakinami Yoshihiro , Uehara Satoshi , Okamoto Sadao , Fujiwara Yasunori , Tanabe Tsutomu 
Published: March 2014

Abstract
The asteroid explorer HAYABUSA reentered into the Earth's atmosphere on 2010 June 13. We made simultaneous TV (television) observations at seven ground sites in order to calculate the trajectories of HAYABUSA and its sample return capsule (SRC), which both reentered into the atmosphere. Our TV observations showed that, after HAYABUSA reentered the atmosphere, the beginning time of its light emission on video was 13:51:57.4 UT at a height of 101.0$\ \pm\ $0.2 km. The end time was 13:52:42.0 UT at a height of 38.6$\ \pm\ $0.2 km. The initial velocity at the beginning was 12.1$\ \pm\ $0.3 km s$^{-1}$, and the entry angle was 9$^{\circ}$. After identifying SRC as separated light emission independent of the mother spacecraft, we analyzed the trajectory of SRC from a height of 52.9 km to 35.7 km based on video images. The actual trajectory of the capsule, determined from the TV observations, was almost the same as the predicted trajectory in terms of the position, velocity, and time. We then calculated the fall spots of the SRC heat shields from the multisite TV observations.
Black-Hole Shadow Has Infinite Optical Depth
Authors: Fukue Jun 
Published: March 2014

Abstract
When a black hole is surrounded by a geometrically thin standard disk, we would observe a black-hole silhouette, whose edge is an innermost stable circular orbit. When it is surrounded by a geometrically thick supercritical disk, the central black hole would be self-occulted by the disk itself and massive winds. When it is covered by an optically thin plasma, on the other hand, a black-hole shadow would be seen, and observations of the black-hole shadow is now desired. If the optically thin plasma is freely infalling, however, we find that the optical depth in the radial direction becomes infinite due to the relativistic effect. Hence, the physical meanings of the black-hole shadow should be re-interpreted, although the shadow would be seen.