bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi-Line Observations of Molecular Gas in the Central Region of the Low Star-Formation Efficiency “Starburst” Galaxy NGC 4527
Authors: Shibatsuka Toshihito , Matsushita Satoki , Kohno Kotaro , Kawabe Ryohei 
Published: March 2014

Abstract
We performed high-resolution CO($J = 2 \hbox{--} 1$), CO($J = 1 \hbox{--} 0$), HCN($J = 1 \hbox{--} 0$), $\mathrm{HCO}^{+}$($J = 1 \hbox{--} 0$), and 3 mm continuum observations of the low star formation efficiency (SFE) “starburst” galaxy NGC 4527 with the Nobeyama Millimeter Array. From CO($J = 1 \hbox{--} 0$) observations, we found two offset ridges with non-circular motion and a central gas concentration. The distribution and kinematics of NGC 4527 are very similar to those of barred spiral galaxies. The distribution of CO($J = 2 \hbox{--} 1$) emission resembles the features of the concentrated component of CO($J = 1 \hbox{--} 0$). HCN($J = 1 \hbox{--} 0$) and $\mathrm{HCO}^{+}$($J = 1 \hbox{--} 0$) emissions concentrated toward the center have also been detected. The total mass of molecular gas detected in the central $r &lt; {30{}^{\mathrm {\prime \prime }}}$ is $2.5 \times 10^9 \,{{{M}_{\odot}}}$. The $\mathrm{HCN}\,(J = 1 \hbox{--} 0) / \mathrm{CO}\,(J = 1 \hbox{--} 0)$ integrated intensity ratio of $0.075 \pm 0.008$ in the central $r \lesssim {3{}^{\mathrm {\prime \prime }}} \hbox{--} {4{}^{\mathrm {\prime \prime }}}$ region of NGC 4527 could suggest that the fraction of dense molecular gas to the total molecular gas is small compared with those of prototypical starburst galaxies, such as NGC 253. This suggests that the small dense gas fraction is responsible for the low SFE in the center of NGC 4527, though this interpretation could depend on aperture sizes of the observations. The ratio of the dynamical mass to molecular gas mass is 13% within the central region ($r &lt; 500 \,\mathrm{pc}$). This suggests that molecular gas within the $r &lt; 500 \,\mathrm{pc}$ region could be in a state of gravitational instability. The low SFE, the small dense gas fraction, and the large amount of gravitationally unstable molecular gas can be explained if NGC 4527 is in the very early phase of starburst phenomena or a pre-starburst phase, and the formation of dense molecular gas will begin and the SFE will increase within a short time scale.
Application of a Self-Organizing State Space Model to the Leonid Meteor Storm in 2001
Authors: Takeuchi Tsutomu T. , Shiki Shigetomo , Miyamoto Daisuke , Fujiwara Hideaki , Kitazume Jun , Utsumi Yousuke 
Published: March 2014

AbstractThe Leonids show meteor storms with a period of 33 years, and are known as one of the most active meteor showers. It has recently shown a meteor stream consisting of several narrow dust trails made by meteoroids ejected from a parent comet. Hence, an analysis of the temporal behavior of the meteor flux is important to study the structure of the trails. However, statistical inference for the count data is not an easy task, because of its Poisson characteristics. We carried out a wide-field video observation of the Leonid meteor storm in 2001. We formulated a state-of-the-art statistical analysis, which is called a self-organizing state space model, to infer the true behavior of the dust density of the trails properly from the meteor count data. From this analysis, we found that the trails have a fairly smooth spatial structure, with small and dense clumps that cause a temporal burst of meteor flux. We also proved that the time behavior (trend) of the fluxes of bright meteors and that of faint meteors are significantly different. In addition we comment on some other application of the self-organizing state space model in fields related to astronomy and astrophysics.
Discovery of a Short Plateau Phase in the Early Evolution of a Gamma-Ray Burst Afterglow
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Yamaoka Hitoshi 
Published: March 2014

Abstract
We report on optical observations during the first hour of the gamma-ray burst (GRB) afterglow of GRB 021004. Our observations revealed the existence of a short plateau phase, in which the afterglow remained at almost constant brightness, before an ordinary rapid-fading phase. This plateau phase lasted for about 2 hours from 0.024 to 0.10 d after the burst, which corresponds to a missing blank of the early afterglow light curve of GRB 990123. We propose that the plateau phase can be interpreted as being the natural evolution of synchrotron emission from the forward shock region of a blast wave. The time when the typical frequency of the synchrotron emission passes through the optical range has been predicted to be about 0.1 d after the burst, which is consistent with the observed light curve. Our scenario hence implies that the observed feature in GRB 021004 is a common nature of GRB afterglows.
Superhumps in a Rarely Outbursting SU UMa-Type Dwarf Nova, HO Delphini
Authors: Kato Taichi , Nogami Daisaku , Moilanen Marko , Yamaoka Hitoshi 
Published: March 2014

Abstract
We observed the 1994, 1996, and 2001 outbursts of HO Del. From the detection of secure superhumps, HO Del is confirmed to be an SU UMa-type dwarf nova with a superhump period of 0.06453(6)d. Based on recent observations and past records, the outbursts of HO Del are found to be relatively rare, with the shortest intervals of superoutbursts being $\sim 740 \,\mathrm{d}$. Among SU UMa-type dwarf novae with similar outburst intervals, the outburst amplitude ($\sim 5.0 \,\mathrm{mag}$) is unusually small. HO Del showed a rather rapid decay of the superhump amplitudes, and no regrowth of the amplitudes during the later stage, in contrast to the commonly observed behavior in SU UMa-type dwarf novae with long outburst intervals. We positively identified HO Del with a ROSAT X-ray source, and obtained a relatively large X-ray luminosity of $10^{31.1 \pm 0.2} \,\mathrm{erg} \,\mathrm{s}^{-1}$. We also performed a literature survey of SU UMa-type dwarf novae and presented a new set of basic statistics. The SU UMa-type dwarf novae with a brightening trend or with a regrowth of superhumps near the termination of a superoutburst are found to be rather tightly confined in a small region on the (superhump period–supercycle length) plane. These features may provide a better observational distinction for the previously claimed subgroup of dwarf novae (Tremendous Outburst Amplitude Dwarf Novae).
43 GHz SiO Masers and Astrometry with VERA in the Galactic Center
Authors: Sjouwerman Loránt O. , Messineo Maria , Habing Harm J. 
Published: March 2014

Abstract
We present Very Large Array (VLA) observations of 43 GHz SiO ($J = 1 \hbox{--} 0, v=2$ and $v=1$) maser emission in a sub-sample of late-type stars in the Inner Galaxy selected on their relatively strong ($ \gt 0.5 \,\mathrm{Jy}$) 86 GHz SiO masers, and located within ${2\rlap {.}{}^{\mathrm {\circ }}5}$ of the galactic center. Furthermore we combine these results with a summary of previous surveys for 43 GHz SiO masers in the galactic center and comment on their use as calibrators for the Japanese “VLBI Exploration of Radio Astrometry” (VERA) network, which is intended to perform sub-milli-arcsecond astrometry in the Galaxy and the galactic center.
SiO Maser Survey of the Large-Amplitude Variables in the Galactic Center
Authors: Deguchi Shuji , Imai Hiroshi , Fujii Takahiro , Glass Ian S. , Ita Yoshifusa , Izumiura Hideyuki , Kameya Osamu , Miyazaki Atsushi , Nakada Yoshikazu , Nakashima Jun-ichi 
Published: March 2014

Abstract
We have surveyed $\sim 400$ known large-amplitude variables within $15'$ of the galactic center in the SiO ${J = 1 \hbox{--} 0} {v = 1}$ and 2 maser lines at 43 GHz, resulting in 180 detections. SiO lines were detected from 16 other sources located within $20''$ of the program objects. The detection rate of 48% is comparable to that in bulge IRAS surveys. Among the detections, five stars have radial velocities greater than $200 \,\mathrm{km} \,\mathrm{s}^{-1}$. The detection rate increases steeply with the period of light variation, particularly for stars with $P \gt 500 \,\mathrm{d} P \gt 500 \,\mathrm{d}$, where it exceeds 80%. At a given period, the SiO detection rate is approximately three-times that for OH. These facts suggest that the large-amplitude variables in the Nuclear Disk region are AGB stars similar in their overall properties to the inner and outer bulge IRAS/SiO sources. From the set of radial velocity data, the mass distribution within 30 pc of the galactic center was derived based on the collisionless Boltzmann equation integrated along the line of sight. The mass is about $6.5\,(\pm 0.7) \times 10^7 \,{{{M}_{\odot}}}$ and the mass of the central black hole is $2.7\,(\pm 1.3) \times 10^6 \,{{{M}_{\odot}}}$. From the line-of-sight velocity of each star and its potential energy we conclude that the five high-velocity stars come from galactocentric distances as far as 300 pc. A high-velocity subsample of stars with negative radial velocities exhibits a tendency to have brighter $K$ magnitudes than a subsample with positive velocities. The origin of these stars is discussed.
Energetics of a Black Hole-Accretion Disk System with Magnetic Connection: Limit of Low Accretion Rate
Authors: Li Li-Xin 
Published: March 2014

Abstract
We consider the energetics of a black hole-accretion disk system with magnetic connection: a Keplerian disk is connected to a Kerr black hole by a large-scale magnetic field. We assume that 1) the magnetic field is locked to the inner boundary of the disk and corotates with it, and 2) the accretion rate is low, but the accretion from the disk can still provide a sufficient amount of cold plasma particles in the transition region so that the magnetohydrodynamics approximation is valid. By finding solutions that smoothly pass the fast critical point near the equatorial plane, we find that a system with a fast rotating black hole and that with a slow rotating black hole behave very differently. For a black hole with $a \gt a_\mathrm{cr} \equiv 0.3594 \,M a &gt; a_\mathrm{cr} \equiv 0.3594 \,M$, where $M$ is the mass and $a$ is the specific angular momentum of the black hole, the spinning energy of the black hole is efficiently extracted and transported to the disk, thus increasing the radiation efficiency of the disk by orders of magnitude. For a black hole with $0 \leq a &lt; a_\mathrm{cr}$, the inner region of the disk is disrupted by the magnetic field and the inner boundary moves out to a radius where the angular velocity of the disk is equal to the spinning angular velocity of the black hole. As a result, the disk may have an extremely low radiation efficiency if $0\leq a/M \ll 1$.
Precise Differential Analysis of Stellar Metallicities: Application to Solar Analogs Including 16 Cyg A and B
Authors: Takeda Yoichi 
Published: March 2014

Abstract
A method is presented for very accurately establishing the differences of the atmospheric parameters (the effective temperature, the surface gravity, the microturbulent velocity, and the Fe abundance) between two similar stars by using the equivalent widths of Fe I and Fe II lines, which is a variant of the numerical solution-search approach developed by Takeda et al. (2002, PASJ, 54, 451), while being inspired by the spirit of the orthodox “differential curve-of-growth” procedure. By applying this technique to eight selected stars similar to the Sun [HD 20630, 76151, 134987, 181655, 186408 (16 Cyg A), 186427 (16 Cyg B), 195019, and 217014] along with the Sun itself, the parameter differences between any pairs of these stars could be successfully determined to precisions of $\sim 10 \,\mathrm{K}$ (in $\Delta T_{\mathrm{eff}}$), $\sim 0.02 \,\mathrm{dex}$ (in $\Delta\log g$), $\sim 0.02 \,\mathrm{km} \,\mathrm{s}^{-1}$ (in $\Delta v_{\mathrm{t}}$), and $\sim 0.01 \,\mathrm{dex}$ (in $\Delta A_{\mathrm{Fe}}$). Regarding 16 Cyg A and B, a well-known “solar twin” system where a planet has been detected only in B, the metallicities of these two components were concluded to be essentially the same to a level of $\lesssim 0.01 \,\mathrm{dex}$.
The Schmidt Law at High Molecular Densities
Authors: Komugi Shinya , Sofue Yoshiaki , Nakanishi Hiroyuki , Onodera Sachiko , Egusa Fumi 
Published: March 2014

Abstract
We combined $\mathrm{H}\alpha$ and recent high-resolution ${{12\atop} \mathrm{CO}}$ ($J = 1 \hbox{--} 0$) data to consider the quantitative relation between the gas mass and the star-formation rate, or the so-called Schmidt law in nearby spiral galaxies at regions of high molecular density. The relation between the gas quantity and the star-formation rate has not been previously studied for high-density regions, but using high-resolution CO data obtained at the Nobeyama Millimeter Array, we found that the Schmidt law is valid at densities as high as $10^3 \,{{{M}_{\odot}}} \,\mathrm{pc}^{-2}$ for sample spiral galaxies, which is an order of magnitude denser than what has been known to be the maximum density at which the empirical law holds for non-starburst galaxies. Furthermore, we obtained a Schmidt law index of $N = 1.33 \pm 0.09$ and a roughly constant star-formation efficiency over the entire disk, even within several hundred parsecs of the nucleus. These results imply that the physics of star formation does not change in the central regions of spiral galaxies. Comparisons with starburst galaxies are also given. We find a possible discontinuity in the Schmidt law between normal and starburst galaxies.
XMM-Newton Observation of IC 310 in the Outer Region of the Perseus Cluster of Galaxies
Authors: Sato Kosuke , Furusho Tae , Yamasaki Noriko Y. , Ishida Manabu , Matsushita Kyoko , Ohashi Takaya 
Published: March 2014

Abstract
We present results from an XMM-Newton observation of the head-tail radio galaxy IC 310 located in the southwest region of the Perseus cluster. The spectrum is well fitted by an absorbed power-law model with a photon index of $2.50 \pm 0.02$ without significant absorption excess. The X-ray image shows a point-like emission at IC 310 without any sign of a structure correlated with the radio halo tail. The temperature of the intracluster medium surrounding IC 310 declines as a function of distance from the cluster center, from $kT \sim 6 \,\mathrm{keV}$ in the northeast corner of the field of view to about 3 keV in the southwest region. Although we do not find any sharp edges in the surface brightness profile, a brightness excess of about 20% over a smooth $\beta$ model is seen. The temperature also rises by about 10% in the same region. This indicates that the IC 310 region is a subcluster probably infalling into the Perseus cluster, and the gas in front of IC 310 towards the Perseus cluster is likely to be compressed by the large-scale motion, which supports the view that the IC 310 system is undergoing a merger.
Strong Emission-Line Galaxies at Low Redshifts in the Field around the Quasar SDSSp J104433.04−012502.2
Authors: Ajiki Masaru , Shioya Yasuhiro , Taniguchi Yoshiaki , Murayama Takashi , Nagao Tohru , Sasaki Shunji S. , Sumiya Ryoko , Morioka Taichi , Hatakeyama Yuichiro , Yokouchi Asuka , Takahashi Mari I. , Koizumi Osamu 
Published: March 2014

Abstract
We discuss the observational properties of strong emission-line galaxies at low redshifts found by our deep imaging survey for high-redshift Ly$\alpha$ emitters. In our survey, we used a narrow-band filter, NB816 ($\lambda_{\mathrm{center}} = 8150 \,{Å}$ with $\mbox{FWHM} = 120 \,\mbox{Å}$ FWHM$= 120 \,{Å}$), and an intermediate-band filter, IA827 ($\lambda_{\mathrm{center}} = 8270 \,{Å}$ with $\mbox{FWHM} = 340 \,\mbox{Å}$ FWHM$= 340 \,{Å}$). In this survey, 62 NB816-excess ($\gt 0.9 \,\mathrm{mag} \gt 0.9 \,\mathrm{mag}$) and 21 IA827-excess ($\gt 0.8 \,\mathrm{mag} \gt 0.8 \,\mathrm{mag}$) objects were found. Among them, we found 20 NB816-excess and 4 IA827-excess Ly$\alpha$ emitter candidates. Therefore, it turns out that 42 NB816-excess and 17 IA827-excess objects are strong emission-line objects at lower redshifts. Since 4 objects in the two low-$z$ samples are common, the total number of strong low-$z$ emitters is 55. Applying our photometric redshift technique, we identified 7 $\mathrm{H}\alpha$ emitters at $z \approx 0.24$, 20 $\mathrm{H}\beta$–[O III] ones at $z \approx 0.65$, and 11 [O II] ones at $z \approx 1.19$. However, we could not determine reliable photometric redshifts of the remaining 17 emitters. The distributions of their rest frame equivalent widths are consistently understood based on recent studies of galaxy evolution from $z \sim 1$ to $z \sim 0$.
Reliability Checks on the Indo-US Stellar Spectral Library Using Artificial Neural Networks and Principal Component Analysis
Authors: Singh Harinder P. , Yuasa Manabu , Yamamoto Nawo , Gupta Ranjan 
Published: March 2014

Abstract
The Indo-US coudé feed stellar spectral library (CFLIB) made available to the astronomical community recently by Valdes et al. (2004, ApJS, 152, 251) contains spectra of 1273 stars in the spectral region 3460 to 9464 Å at a high resolution of 1 Å (FWHM) and a wide range of spectral types. Cross-checking the reliability of this database is an important and desirable exercise since a number of stars in this database have no known spectral types and a considerable fraction of stars has not so complete coverage in the full wavelength region of 3460–9464 Å resulting in gaps ranging from a few Å to several tens of Å. We use an automated classification scheme based on Artificial Neural Networks (ANN) to classify all 1273 stars in the database. In addition, principal component analysis (PCA) is carried out to reduce the dimensionality of the data set before the spectra are classified by the ANN. Most importantly, we have successfully demonstrated employment of a variation of the PCA technique to restore the missing data in a sample of 300 stars out of the CFLIB.
Three-Dimensional Simulation of Solar Emerging Flux Using the Earth Simulator I. Magnetic Rayleigh-Taylor Instability at the Top of the Emerging Flux as the Origin of Filamentary Structure
Authors: Isobe Hiroaki , Miyagoshi Takehiro , Shibata Kazunari , Yokoyama Takaaki 
Published: March 2014

Abstract
We present the results of three-dimensional magnetohydrodynamic simulations of solar emerging flux and its interaction with preexisting coronal field. In order to resolve the fine structures and the current sheets, we used high-resolution grids with up to $800 \times 400 \times 620$ points; the calculation was carried out using the Earth Simulator. The model set up is an extension of a previous two-dimensional simulation by Yokoyama and Shibata (1995) to include the variation along the third direction. Based on the same simulation result, we reported in our previous paper (Isobe et al. 2005): (1) Dense filaments similar to H$\alpha$ arch filament system are spontaneously formed in the emerging flux by the magnetic Rayleigh–Taylor type instability. (2) Filamentary current sheets are created in the emerging flux due to a nonlinear development of the magnetic Rayleigh-Taylor instability, which may cause an intermittent, nonuiform heating of the corona. (3) A magnetic reconnection between the emerging flux and preexisting coronal field occurs in a spatially intermittent way. In this paper we describe the simulation model and discuss the origin and the properties of the magnetic Rayleigh-Taylor instability in detail. It is shown that the top-heavy configuration that causes the instability is formed by the intrinsic dynamics of the emerging flux.
New Corroborative Evidence for the Overdensity of Galaxies around the Radio-Loud Quasar SDSS J0836+0054 at z = 5.8
Authors: Ajiki Masaru , Taniguchi Yoshiaki , Murayama Takashi , Shioya Yasuhiro , Nagao Tohru , Sasaki Shunji S. , Hatakeyama Yuichiro , Morioka Taichi , Yokouchi Asuka , Takahashi Mari I. , Koizumi Osamu 
Published: March 2014

Abstract
Recently, Zheng et al. (2006) found evidence for an overdensity of galaxies around a radio-loud quasar, SDSS J0836$+$0054, at $z = 5.8$ (a $5 \,\mathrm{arcmin}^2$ field). We examined our deep optical imaging data ($B, V, r^\prime, i^\prime, z^\prime$, and NB816) taken with the Suprime-Cam on the Subaru Telescope. The NB816 narrow-band filter ($\lambda_{\mathrm{c}} = 815 \,\mathrm{nm}$ and $\Delta\lambda = 12 \,\mathrm{nm}$) is suitable to search for Ly$\alpha$ emitters at $z \approx 5.7$. We found a new strong Ly$\alpha$ emitter at $z \approx 5.7$ close to object B, identified by Zheng et al. (2006). Further, the non-detection of nine objects selected by Zheng et al. (2006) in our $B, V$, and $r^{\prime}$ images provides corroborative evidence to indicate that they are high-$z$ objects.
Binary-Shaped Pupil Coronagraphs for High-Contrast Imaging Using a Space Telescope with Central Obstructions
Authors: Tanaka Shinichiro , Enya Keigo , Abe Lyu , Nakagawa Takao , Kataza Hirokazu 
Published: March 2014

Abstract
We present sets of configurations of binary-shaped pupil coronagraphs optimized for a realistic space telescope to directly detect extrasolar giant planets. For the purpose of mid-infrared observations, the target contrast ratio is set to $10^{-7}$. We made a systematic assessment of the performance of two recently proposed pupil shapes, “checkerboard” and “concentric ring” masks, where a large central obstruction due to a secondary mirror and its related support spiders was introduced into the telescope pupil. It turned out that, if the secondary mirror diameter is smaller than $\sim 15 \%$ of the diameter of the primary, the checkerboard-type masks are more promising in terms of the total high-contrast area. With such a small secondary, we propose to modify the original symmetrical checkerboard apodization function. This modification enables us to achieve a $10^{-7}$ contrast at an inner working angle (IWA) of $4.0 \,\lambda/D$. On the other hand, when the secondary mirror size cannot be reduced to that level, the concentric ring masks are preferable because of their larger transmission. It was also found that the transmission through the optimal binary masks exhibits two characteristic features as the IWA increases: firstly, abrupt increases and secondly, plateaus. We attribute this nature of the binary apodization functions to the existence of threshold IWAs that allow large openings in the pupil.
Spectropolarimetric Study on Circumstellar Structure of Microquasar LS I+61°303
Authors: Nagae Osamu , Kawabata Koji S. , Fukazawa Yasushi , Yamashita Takuya , Ohsugi Takashi , Uemura Makoto , Chiyonobu Shingo , Isogai Mizuki , Cho Toshinari , Suzuki Masaaki , Okazaki Akira , Okita Kiichi , Yanagisawa Kenshi 
Published: March 2014

AbstractWe present an optical linear spectropolarimetry study of the microquasar LS I$+61^{\circ}$303. The continuum emission is mildly polarized (up to 1.3%) and shows almost no temporal change. We found a distinct change of polarization across the $\mathrm{H}\alpha$ emission line, indicating the existence of a polarization component intrinsic to the microquasar. We estimated the interstellar polarization component from polarization of the $\mathrm{H}\alpha$ line and derived the intrinsic polarization component. The wavelength dependence of the intrinsic component is well explained by Thomson scattering in an equatorial disk of a Be-type mass donor. The position angle (PA) of the intrinsic polarization is $\sim 25^{\circ}$, and represents the rotational axis of the Be disk. This PA is nearly perpendicular to the PA of a radio jet found during quiescent phases. Assuming an orthogonal disk–jet geometry around the compact star, the rotational axis of the accretion disk is almost perpendicular to that of the Be disk. Moreover, according to the orbital parameters of the microquasar, the compact star is likely to get across the Be disk around their periastron passage. We discuss the peculiar circumstellar structure of this microquasar inferred based on our observation, and suggest a possible connection with its high-energy activities.