bluuebunny/crossref_metadata_2025 huggingface dataset:
Water-Vapor Maser Disk at the Nucleus of the Seyfert 2 Galaxy NGC 3079
Authors: Yamauchi Aya , Nakai Naomasa , Sato Naoko , Diamond Philip
Published: March 2014

We observed a Seyfert 2/LINER galaxy NGC 3079 using the NRO 45-m telescope from 1992 to 2002, and the Very Long Baseline Array (VLBA) in 2001 December, at 22 GHz. The 45-m telescope detected weak red-shifted and systemic features as well as strong blue-shifted features. High spatial resolution observations with the VLBA indicated that the $\mathrm{H_2O}$ maser spots are distributed along the north-south direction, showing blue-shifted velocities in the north and red-shifted in the south. We propose a nearly edge-on molecular gas disk in the nuclear region of NGC 3079, whose radius varies from 0.4 to 1.2 pc and whose thickness is 0.3 pc. The disk is rotating at $V_\mathrm{rot} = 200 \hbox{--} 100 \,\mathrm{km} \,\mathrm{s}^{-1}$, having a large velocity dispersion of $\Delta V \approx 50 \,\mathrm{km} \,\mathrm{s}^{-1}$. The binding mass within the disk is $\sim 10^6 \,{{{M}_{\odot}}}$. The disk is inclined such that the east side is nearest to us. The large luminosity of the maser emission and exceptionally strong blue-shifted features of NGC 3079 are probably the result of local shocks in the disk. Three continuum components are interpreted as jets emitted from the nucleus. The velocities of the components relative to the dynamical center of the masing disk are $(0.09 \hbox{--} 0.17) \,c, <0.005 \,c$, and $<0.05 \,c$.
H I Jet G40—15 from a Rotating Cloud in the 4-kpc Molecular Ring: Magnetized Outflow and Formation of a Dense Star Cluster
Authors: Sofue Yoshiaki , Kudoh Takahiro , Kawamura Akiko , Shibata Kazunari , Fujimoto Mitsuaki
Published: March 2014

A giant H I spur centered on $(l, b)=(40^{\circ},-15^{\circ})$, (G40$-$15) emanates from G30$-$00 toward negative high latitude. The spur is known as the Smith cloud and as a high-velocity cloud HVC 40$-$15$+$100, while we call it H I jet G40$-$15. The radial velocity ranges from 80 to $120 \,\mathrm{km} \,\mathrm{s}^{-1}$ with the center velocity at $\sim 100\,\mathrm{km} \,\mathrm{s}^{-1}$. Both the kinematical and positional coordinates are coincident with those of the tangential point of the 4-kpc molecular ring of the Galaxy. We interpret this spur as being a magnetized H I jet emanating from the 4-kpc molecular ring of the galactic disk. The kinematical distance is estimated to be 6.9 kpc from the Sun, and the jet’s top (G50$-$26) is $-3.4 \,\mathrm{kpc}$ high from the galactic plane. The whole extent is 4.4 kpc in length and 300 pc in width. The total H I mass is $\sim 3 \times 10^5 \,{{{M}_{\odot}}}$, and the energy to lift the mass from the galactic plane is $\sim 10^{52} \,\mathrm{erg}$. We propose an acceleration mechanism of such an extremely high-altitude coherent H I structure by a twisting magnetic jet associated with a collapsing molecular cloud in the galactic disk. We suggest a scenario for the formation of a dense star cluster, such as a globular cluster, from a collapsing cloud core with a twisting magnetic outflow.
Optical Observation of the 2003 Outburst of a Black Hole X-Ray Binary, V4641 Sagittarii
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Imada Akira , Nogami Daisaku , Monard Berto , Cook Lewis M. , Stubbings Rod , Kiyota Seiichiro , Nelson Peter , Beninger Jean-Yves , Bolt Greg , Heathcote Bernard
Published: March 2014

We report on the results of our optical photometric observations of a black hole X-ray binary, V4641 Sgr during an outburst in 2003 August. During the outburst, we detected several properties having noteworthy similarities to those observed during an outburst in 2002 May; the outburst lasted about 6 days, during which it exhibited flares and rapid fluctuations, having timescales of $10^{2\hbox{--}4} \,\mathrm{s}$. In complicated profiles of light curves, we identified several recurring patterns, which were also observed during the 2002 outburst. First, the object frequently experienced sudden temporary fadings, which we call “dips”, appearing just after the states characterized by strong short-term fluctuations. Second, we detected optical flashes, which are characterized by a brightening by $\sim 0.5 \,\mathrm{mag}$ within $\sim 50 \,\mathrm{s}$. Based on the similarity of the outbursts in 2002 and 2003, we conclude that they have the same nature. This is the first time that repetitive outburst phenomena have been confirmed in V4641 Sgr. The object probably has an outburst interval that can be as small as 1–2 years.
Probing Warm-Hot Intergalactic Medium Associated with the Virgo Cluster Using an Oxygen Absorption Line
Authors: Fujimoto Ryuichi , Takei Yoh , Tamura Takayuki , Mitsuda Kazuhisa , Yamasaki Noriko Y. , Shibata Ryo , Ohashi Takaya , Ota Naomi , Audley Michael D. , Kelley Richard L. , Kilbourne Caroline A.
Published: March 2014

To detect a warm-hot intergalactic medium (WHIM) associated with the large-scale structure of the universe, we observed a quasar behind the Virgo cluster with XMM-Newton. With 54 ks exposure, we marginally detected an O VIII $\mathrm{K}\alpha$ absorption line at $650.9^{+0.8}_{-1.9} \,\mathrm{eV}$ in the RGS spectra, with a statistical confidence of 96.4%. The observed line center energy is consistent with the redshift of M 87, and hence the absorber is associated with the Virgo cluster. From the curve of growth, the O VIII column density was estimated to be $\gtrsim 7 \times 10^{16} \,\mathrm{cm}^{-2}$. In the EPIC spectra, excess emission was found after evaluating the hot ICM in the Virgo cluster and various background components. We inspected the RASS map of the diffuse soft X-ray background, and confirmed that the level of the north and west regions just outside of the Virgo cluster is consistent with the background model that we used, while that of the east side is significantly higher and the enhancement is comparable with the excess emission found in the EPIC data. We consider a significant portion of the excess emission to be associated with the Virgo cluster, although a possible contribution from the North Polar Spur cannot be excluded. Using the column density and the emission measure and assuming an oxygen abundance of 0.1 and an ionization fraction of 0.4, we estimate that the mean electron density and the line-of-sight distance of the warm-hot gas are $\lesssim 6 \times 10^{-5} \,\mathrm{cm}^{-3}$ and $\gtrsim 9 \,\mathrm{Mpc}$. These strongly suggest detection of a WHIM in a filament associated with the Virgo cluster.
Photometric Observations of a Very Young Family-Member Asteroid (832) Karin
Authors: Yoshida Fumi , Dermawan Budi , Ito Takashi , Sawabe Yu , Haji Masashige , Saito Ryoko , Hirai Masanori , Nakamura Tsuko , Sato Yusuke , Yanagisawa Toshifumi , Malhotra Renu
Published: March 2014

The asteroid (832) Karin is the largest member of the Karin family, which is thought to have been formed by a catastrophic collision 5.8 Myr ago. We performed photometric observations of Karin from 2003 July to September, and we report here on its lightcurve and colors in several visible bands. The rotational synodic period of Karin was determined to be $18.35 \pm0.02 \,\mathrm{hr}$. Its absolute magnitude ($H$) and the slope parameter ($G$) of the solar phase curve were $11.49 \pm 0.02$ and $0.19 \pm 0.04$, respectively. Based on our color observations, we confirmed that Karin is an S-type asteroid. In addition, we found that there is likely to be a color variation over the surface of Karin. We infer that the color variation is due to the difference between the fresh surface, excavated by the family-forming disruption, and the weathered surface, exposed to space radiation and particle bombardment over a long period.
ASCA Compilation of X-Ray Properties of Hot Gas in Elliptical Galaxies and Galaxy Clusters: Two Breaks in the Temperature Dependences
Authors: Fukazawa Yasushi , Makishima Kazuo , Ohashi Takaya
Published: March 2014

Utilizing ASCA archival data of about 300 objects of elliptical galaxies, groups, and clusters of galaxies, we performed systematic measurements of the X-ray properties of hot gas in their systems, and compiled them in this paper. The steepness of the luminosity-temperature (LT) relation, $L_\mathrm{X} \propto (kT)^{\alpha}$, in the range of $kT \sim 1.5 \hbox{--} 15 \,\mathrm{keV}$ is $\alpha = 3.17 \pm 0.15$, consistent with previous measurements. In the relation, we find two breaks at around ICM temperatures of 1 keV and 4 keV: $\alpha = 2.34 \pm 0.29$ above 4 keV, $3.74 \pm 0.32$ in 1.5–5 keV, and $4.03 \pm 1.07$ below 1.5 keV. Such two breaks are also evident in the temperature and size relation. The steepness in the LT relation at $kT \gt 4 \,\mathrm{keV} kT \gt 4 \,\mathrm{keV}$ is consistent with the scale-relation derived from the CDM model, indicating that the gravitational effect is dominant in richer clusters, while poorer clusters suffer non-gravity effects. The steep LT relation below 1 keV is almost attributed to X-ray faint systems of elliptical galaxies and galaxy groups. We found that the ICM mass within the scaling radius $R_{1500}$ follows the relation of $M_\mathrm{gas} \propto T^{2.33\pm0.07}$ from X-ray faint galaxies to rich clusters. Therefore, we speculate that even such X-ray faint systems contain a large-scale hot gas, which is too faint to detect.
Inversion Formula for Determining the Parameters of an Astrometric Binary
Authors: Asada Hideki , Akasaka Toshio , Kasai Masumi
Published: March 2014

It is believed that some numerical technique must be employed for determining the system parameters of a visual binary or a star with a planet, because the relevant equations are not only highly nonlinear, but also transcendental owing to Kepler’s equation. Such common sense, however, is not true; we have discovered an analytic inversion formula, in which the original orbital parameters are expressed as elementary functions of the observable quantities, such as the location of four observed points and the time interval between these points. The key thing is that we use the time interval, but not the time of each observation, in order to avoid treating Kepler’s equation. The present formula can be applied even in cases where the observations cover a short arc of the orbit during less than one period. Thus, the formula will be useful in future astrometric missions, such as SIM, GAIA, and JASMINE.
Variable Star Network: World Center for Transient Object Astronomy and Variable Stars
Authors: Kato Taichi , Uemura Makoto , Ishioka Ryoko , Nogami Daisaku , Kunjaya Chatief , Baba Hajime , Yamaoka Hitoshi
Published: March 2014

Variable Star Network (VSNET) is a global professional-amateur network of researchers in variable stars and related objects, particularly in transient objects, such as cataclysmic variables, black-hole binaries, supernovae, and gamma-ray bursts. The VSNET has been playing a pioneering role in establishing the field of transient object astronomy, by effectively incorporating modern advances in observational astronomy and global electronic networks, as well as collaborative progress in theoretical astronomy and astronomical computing. The VSNET is now one of the best-featured global networks in this field of astronomy. We review the historical progress, design concept, associated technology, and a wealth of scientific achievements powered by VSNET.
Outburst and Post-Outburst Active Phase of the Black Hole X-Ray Binary V4641 Sagittarii in 2002
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Tanabe Kenji , Torii Ken’ichi , Santallo Roland , Monard Berto , Markwardt Craig B. , Swank Jean H. , Sault Robert J. , Macquart Jean-Pierre , Linnolt Michael , Kiyota Seiichiro , Stubbings Rod , Nelson Peter , Richards Tom , Bailyn Charles , West Doug , Masi Gianluca , Miyashita Atsushi , Sano Yasuo , Scarmato Toni
Published: March 2014

The black hole X-ray binary V4641 Sgr experienced an outburst in 2002 May, which was detected at X-ray, optical, and radio wavelengths. The outburst lasted for only 6 days, but the object remained active for the next several months. Here, we report on the detailed properties of light curves during the outburst and the post-outburst active phase. We reveal that rapid optical variations of $\sim 100 \,\mathrm{s}$ became more prominent when a thermal flare weakened and the optical spectrum flattened in the $I_{\mathrm{c}}$, $R_{\mathrm{c}}$, and $V$-band regions. In conjunction with the flat spectrum in the radio range, this strongly indicates that the origin of rapid variations is not thermal emission, but synchrotron emission. Just after the outburst, we detected repeated flares at optical and X-ray wavelengths. The optical and X-ray light curves exhibited a strong correlation with the X-rays lagging by about 7 min. The X-ray lag can be understood in terms of a hot region propagating into the inner region of the accretion flow. The short X-ray lag, however, requires modifications of this simple scenario to account for the short propagation time. We also detected high-amplitude rapid variations 50 days after the outburst, which we call optical flashes. During the most prominent optical flash, the object brightened by 1.2 mag only within 30 s. The released energy indicates that the emission source should be at the innermost region of the accretion flow.
Stellar Parameters and Photospheric Abundances of Late-G Giants: Properties of the Targets of the Okayama Planet Search Program
Authors: Takeda Yoichi , Sato Bun’ei , Kambe Eiji , Izumiura Hideyuki , Masuda Seiji , Ando Hiroyasu
Published: March 2014

Towards clarifying the properties of late-G giants, for which we are currently conducting a planet-search project at Okayama Astrophysical Observatory, an extensive spectroscopic study has been performed for our first target sample of fifty-seven G6–G9 III stars, in order to establish the atmospheric parameters ($T_{\mathrm{eff}}, \log g, v_\mathrm{t}$, and $\mathrm{[Fe/H]}$), the stellar mass along with the evolutionary status, and the photospheric abundances of various elements. It was confirmed that the conventional spectroscopic method of parameter determination using Fe I / II lines with the assumption of LTE works successfully for these evolved stars. We determined the abundances (relative to the Sun) of 19 elements, and examined how their $\mathrm{[X/Fe]}$ ratios behave themselves with the run of $\mathrm{[Fe/H]}$. While the trends appear to be similar to those exhibited by disk dwarfs for a number of elements, some elements (C, O, Na) showed appreciable anomalies, which may be interpreted as being due to a dredge-up of nuclear-processed material. Since the $\mathrm{[Fe/H]}$ values of these stars tend to be somewhat biased towards a subsolar regime, some mechanism of slightly reducing the metallicity might be suspected.
Black Hole Shadows of Charged Spinning Black Holes
Authors: Takahashi Rohta
Published: March 2014

We propose a method for measuring the black hole charge by imaging a black hole shadow in a galactic center by future interferometers. Even when the black hole is uncharged, it is possible to confirm the charge neutrality by this method. We first derive the analytic formulae of the black hole shadow in an optically thin medium around a charged spinning black hole, and then investigate how contours of the black hole shadow depend on the spin and the charge of the black hole for several inclination angles between the rotation axis of the black hole and the observer. This method only assumes a stationary black hole and general relativity. By fitting the formula of the contours of the shadow to the observed image of the shadow, in addition to the black hole charge, one can also determine the black hole spin and the inclination angle without any degeneracy among the charge, the spin, and the inclination angle unless the inclination angle is null. If the maximum width of a shadow smaller than $4 \, (1+2^{1/2})M$ or the minimum width of a shadow smaller than $9M$ is measured observationally, we can safely conclude that the black hole is charged. Here, $M$ is the gravitational radius, i.e. the half of the Schwarzschild radius.
Time Evolution of Relativistic Force-Free Fields Connecting a Neutron Star and its Disk
Authors: Asano Eiji , Uchida Toshio , Matsumoto Ryoji
Published: March 2014

We study the magnetic interaction between a neutron star and its disk by solving the time-dependent relativistic force-free equations. At the initial state, we assumed that the dipole magnetic field of the neutron star connects the neutron star and its equatorial disk, which deeply enters into the magnetosphere of the neutron star. Magnetic fields were assumed to be frozen to the star and the disk. The rotations of the neutron star and the disk were imposed as boundary conditions. We applied the Harten–Lax–van Leer (HLL) method to simulate the evolution of the star-disk system. We carried out simulations for (1) a disk inside the corotation radius, in which the disk rotates faster than the star, and (2) a disk outside the corotation radius, in which the neutron star rotates faster than the disk. The numerical results indicate that for both models, the magnetic field lines connecting the disk and the star inflate as they are twisted by the differential rotation between the disk and the star. When the twist angle exceeds $\pi$ radian, the magnetic field lines expand with a speed close to the speed of light. This mechanism can be the origin of the relativistic outflows observed in binaries containing a neutron star.
Time-Series Analysis of Terrestrial Impact Crater Records
Authors: Chang Heon-Young , Moon Hong-Kyu
Published: March 2014

A database of impact craters becomes available with more accurate and more precise age estimates due to a new decay constant. This motivates us to revisit the periodicity hypothesis for the terrestrial impact cratering rate, using the new data set. We present a new way to analyze the impact cratering rate as an oscillator in the time domain. This technique aims to produce an accurate frequency of an oscillator whose phase is modulated, and to reveal the slowly varying phase function. Having applied the technique to recent cratering records, which are grouped into 6 subsamples by criteria on the age and diameter of impact craters, we found the presence of a $\sim 26 \,\mathrm{Myr}$ periodicity in the impact cratering rate over the last $\sim 250 \,\mathrm{Myr}$. Such a periodicity can be found consistently in subsamples regardless of the lower limit of the diameter up to $D \sim 35 \,\mathrm{km}$. We have also calculated the period of the impact cratering rate using the Lomb–Scargle periodogram method. The Lomb–Scargle periodogram method yields slightly more scattered periods, implying that our technique is more robust and stable than the Lomb-Scargle periodogram analysis. As reproducing $f(t)$, we found that its typical magnitude of $\epsilon\, \overline{f(t)}$ is much smaller than that of the frequency. Therefore, we conclude that the impact cratering rate may be regarded as unimodal.
Giant Flare of SGR 1806−20 from a Relativistic Jet
Authors: Yamazaki Ryo , Ioka Kunihito , Takahara Fumio , Shibazaki Noriaki
Published: March 2014

The Japanese magnetospheric explorer GEOTAIL recorded a detailed light curve during the initial 600 msec of a giant flare from SGR 1806$-$20 on 2004 December 27. We show that the observed light curve is well explained by emission from relativistically expanding fireballs, like those of gamma-ray bursts (GRBs). Especially, the observed rapid fading after 500 msec suggests that ejecta were collimated in a jet. We derived an upper limit on the jet opening half-angle of 0.2 rad, which is as narrow as those of GRBs.
Terminal Speed of On-Axis Jets from a Supercritical Accretion Disk
Authors: Fukue Jun
Published: March 2014

For on-axis jets from a luminous supercritical accretion disk, we examine equilibrium speeds without gravity and terminal speeds with gravity, taking account of radiative flux as well as radiation drag. We assume a self-similar model for the supercritical disk. The equilibrium speed approaches the speed of light far from the disk, since the luminous region is centrally condensed. The terminal speed, on the other hand, is generally less than the speed of light due to the existence of gravity. In addition, it uniquely depends on the accretion rate, since the terminal speed depends on the size, shape, and luminosity of the disk, which are uniquely determined by the accretion rate. We found a fitting formula for the terminal speed ($v_\infty$) at infinity, as a function of the accretion rate or disk luminosity in the case of electron–proton normal plasmas. The first one is $v_\infty/c \sim 1-\pi / \sqrt{\dot{m}}$, where $\dot{m}$ is the normalized accretion rate. The other is $\gamma_\infty \sim 1 + 0.223 \Gamma$, where $\gamma_\infty = 1 / \sqrt{1-(v_\infty/c)^2}$, and $\Gamma$ is the normalized disk luminosity. These relations can be tested observationally. Under the present model, in the case of SS 433, where the jet speed is about $0.26 \,c$, the normalized accretion rate is about 20, while it is about 2000 in the case of GRS 1915$+$105 and GRO J1655$-$40, where the jet speed is about $0.92 \,c$.
Influence of a Non-Dipole Magnetic Field on the Peak Energies of Cyclotron Absorption Lines
Authors: Nishimura Osamu
Published: March 2014

We calculate cyclotron lines in a neutron star slab assuming a non-dipole surface magnetic field. We consider the influences of a non-dipole surface field on the properties of the cyclotron resonant scattering lines. When the magnetic field strength decreases with height in the line-forming region, the ratios of the higher harmonics to the fundamental at the peak energies of the cyclotron lines become less than classical harmonic ratios, $1 : 2 : 3 \dots$. On the other hand, when the magnetic field strength increases with height in the line-forming region, the ratios at the peak energies of the cyclotron lines become more than the classical harmonic ratios. The deviation from the harmonic ratios, which has actually been observed in some accretion-powered X-ray pulsars, is more significant than that expected from a relativistic effect in the cyclotron resonant energy. This may suggest the line-forming region is threaded by a strong non-dipole magnetic field in some accreting X-ray pulsars. In observations, the ratios are more or less than the classical harmonic ratios. This could imply that the magnetic field strength in the line-forming region decreases or increases with the altitude or the horizontal distance from an emission region.
Vectorization and Parallelization of the Adaptive Mesh Refinement N-Body Code
Authors: Yahagi Hideki
Published: March 2014

We describe our vectorized and parallelized adaptive mesh refinement (AMR) $N$-body code with shared time steps, and report its performance on a Fujitsu VPP5000 vector-parallel supercomputer. Our AMR $N$-body code puts hierarchical meshes recursively where higher resolution is required and the time step of all particles are the same. The parts that are the most difficult to vectorize are loops that access the mesh data and particle data. We vectorized such parts by changing the loop structure, so that the innermost loop steps through the cells instead of the particles in each cell, in other words, by changing the loop order from the depth-first order to the breadth-first order. We also parallelized our code for distributed memory machines. The important part of parallelization is data decomposition. We sorted the hierarchical mesh data by the Morton order, or the recursive N-shaped order, level by level and split and allocated the mesh data to the processors. Particles are allocated to the processor to which the finest refined cells including the particles are also assigned. Our timing analysis using $\Lambda$-dominated cold dark matter simulations shows that our parallel code speeds up almost ideally up to 32 processors, the largest number of processors in our test.
Phoenicids in 1956 Revisited
Authors: Watanabe Jun-ichi , Sato Mikiya , Kasuga Toshihiro
Published: March 2014

The outburst of the Phoenicids observed in 1956 was investigated on the basis of the dust trail theory by using a newly linked orbit, which was estimated from the asteroid 2003 WY25 and comet D/1819 W1 (Blanpain). We found that a bundle of the trails formed from the late 18th through the early 19th centuries came close to the Earth’s orbit at the epoch of the outburst in 1956. According to similar calculations for 1950–2030, the situation in 1956 was proven to be the best epoch for a strong display in the Phoenicids. This result shows not only a definite association of the objects to the Phoenicids, but also a clear reason for the sudden outburst in 1956. Although future activity is expected in 2014, it depends on the cometary activity of the parent object, because the related trails are expected to be relatively new.
On Multipolar Analytical Potentials for Galaxies
Authors: Vogt Daniel , Letelier Patricio S.
Published: March 2014

We present analytical potential-density pairs in three dimensions for the gravitational field of galaxies, obtained by thickening the multipolar expansion up to the quadrupole term. These may be interpreted as generalizations of the Miyamoto and Nagai potential-density pairs. With a suitable restriction on the possible values of the multipole moments, the density distributions are positive and monotone decreasing functions of the radial and axial coordinates.
Photometric Investigations of Three Short-Period Binary Systems: GSC 0763−0572, RR Centauri, and ϵ Coronae Australis
Authors: Yang Yuan-Gui , Qian Sheng-Bang , Zhu Li-Ying , He Jia-Jia , Jin-Zhao Yuan
Published: March 2014

CCD photometric observations of the short-period eclipsing binary GSC 0763–0572 were carried out in the $B$ and $V$ bands at Yunnan Observatory in China. Three light minimum times were determined from the observations and the orbital period of this system was revised. Photometric solutions for three W UMa-type stars (i.e., GSC 0763–0572, RR Cen, and $\epsilon$ CrA) were deduced by the 2003 version of the Wilson–Devinney code with and without third lights. All three systems are found to be A-type eclipsing binaries with low mass ratios. Combining with the radial-velocity curves for RR Cen (King, Hilditch 1984, MNRAS, 209, 645) and $\epsilon$ CrA (Goecking, Duerbeck 1993, A&A, 278, 463), the absolute parameters for those two binaries were redetermined. Based on all minimum times of RR Cen, it is found that the orbital period shows a long-term increase superimposed on a cyclic variation. The secular change with a rate of $dP/dt = +1.21 \times 10^{-7} \,\mathrm{d} \,\mathrm{yr}^{-1}$ may suggest that RR Cen is undergoing mass transfer from the secondary component to the primary one with $dm/dt = +3.12 \times10^{-8} \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1}$. The cyclic oscillation with a period of $65.1 \,(\pm 0.4) \,\mathrm{yr}$ and an amplitude of $0.0124 \,(\pm 0.0007) \,\mathrm{d}$ may be explained by the presence of a third body, which can be identified by the revised photometric solution. It is believed that if the orbital period increases for those systems is true, this kind of binary may evolve into a rapid-rotating single star.
The 2003/2004 Superoutburst of SDSS J013701.06−091234.9
Authors: Imada Akira , Kato Taichi , Kubota Kaori , Uemura Makoto , Ishioka Ryoko , Kiyota Seiichiro , Kinugasa Kenzo , Maehara Hiroyuki , Nakajima Kazuhiro , Monard L. A. G. Berto , Starkey Donn R. , Oksanen Arto , Nogami Daisaku
Published: March 2014

We report on time-resolved photometry of the superoutburst of an SU UMa-type dwarf nova, SDSS J013701.06$-$091234.9, in 2003 December–2004 January. The obtained light curves definitely show superhumps with a period of 0.056686(12)d, which is one of the shortest superhump periods among those of SU UMa-type dwarf novae ever observed. Considering quiescent photometric studies, we estimated the fractional superhump excess to be 0.024. Spectroscopic observations by Szkody et al. (2003, AJ, 126, 1499) provided evidence for TiO bands despite the short orbital period, implying that the system has a luminous secondary star. We have drawn a color-color diagram of SU UMa-type dwarf novae in quiescence using 2MASS archives, revealing that the location of this star in the color-color diagram deviates from the general trend. The distance to the system was roughly estimated to be $300 \pm 80 \,\mathrm{pc}$, using the empirical period–absolute magnitude relation and based on the proper motion.
Quasi-Periodic Oscillations of Microwave Emission in Solar Active Regions
Authors: Gelfreikh George B. , Nagovitsyn Yury A. , Nagovitsyna Elena Yu.
Published: March 2014

In this paper we discuss QPOs registered at microwaves using the Nobeyama Radioheliograph (NoRH). Our main conclusions concerning the QPO, found from NoRH observations, include: In addition to widely known 3-min oscillations and comparatively less investigated shorter fluctuations, we have registered over sunspots at microwave range also a diversity of more long-term periodic processes having typical periods of tens and hundreds of minutes. In some sunspots these periods are dominating. In a single active region, different plasma structures can simultaneously oscillate within a long-term range with different periods. Most of the different plasma structures of the solar atmosphere registered at the Nobeyama radio maps at a wavelength of 1.76 cm at all heliographic latitudes show the presence of the long-term QPO. In observations of the QPO at microwaves, we have dealt mostly with nonstationary processes. We have thus used wavelet analysis to estimate the quality of proper plasma resonators responsible for QPOs. In our interpretation, three types of plasma oscillators were proposed to be of importance: resonators that coincide with the emitting region; resonators that are outside, but close to the radio emitter; and resonators of the global solar nature. We conclude that NoRH has opened a new era in the study of different quasi-periodic oscillations and waves in the plasma structures of the solar atmosphere.
Self-Similar Solutions for ADAF with Toroidal Magnetic Fields
Authors: Akizuki Chizuru , Fukue Jun
Published: March 2014

We examined the effect of toroidal magnetic fields on a viscous gaseous disk around a central object under an advection-dominated stage. We found self-similar solutions for the radial infall velocity, rotation velocity, and sound speed, with an additional parameter, $\beta \; [=c_{\mathrm{A}}^2/(2 \,c_{\mathrm{s}}^2)$], where $c_{\mathrm{A}}$ is the Alfvén speed and $c_{\mathrm{s}}$ is the isothermal sound speed. Compared with the non-magnetic case, in general the disk becomes thick due to the magnetic pressure, and the radial infall velocity and rotation velocity become fast. In a particular case, where the magnetic field is dominant, on the other hand, the disk becomes to be magnetically supported, and the nature of the disk is significantly different from that of the weakly magnetized case.
Sequential Formation of Low-Mass Stars in the BRC 14 Region*
Authors: Ikuko Matsuyanagi , Itoh Yoichi , Sugitani Koji , Oasa Yumiko , Mukai Tadashi , Tamura Motohide
Published: March 2014

We carried out a deep near-infrared survey of a bright-rimmed molecular cloud, BRC 14 (IC 1848A). The $10\,\sigma$ limiting magnitude of the survey is 17.7 mag at the $K$-band. Seventy-four sources are classified as young stellar object (YSO) candidates based on a near-infrared color–color diagram. The faintest YSO candidates may have masses on the order of tenths of the solar mass, assuming an age of 1 Myr. We examined three values as indicators of star formation: fraction of the YSO candidates, extinctions of all sources, and near-infrared excesses of the YSO candidates. All indicators increase from outside of the rim to the center of the molecular cloud, which suggests that the formation of the low-mass stars in the BRC 14 region proceeds from outside to the center of the cloud.
Dynamical Effects of Cold Dark Matter Subhalos on a Galactic Disk
Authors: Hayashi Hirohito , Chiba Masashi
Published: March 2014

We have investigated the dynamical interaction between a galactic disk and numerous surrounding dark subhalos as expected for a galaxy-sized halo in the cold dark matter models. Our particular interest is to what extent accretion events of subhalos into a disk are allowed in light of the observed thinness of a disk. Several models of subhalos were considered in terms of their internal density distribution, mass function, and spatial and velocity distributions. Based on a series of $N$-body simulations, we find that disk thickening, quantified by the change of its scale height, $\Delta z_{\mathrm{d}}$, depends strongly on the individual mass of an interacting subhalo, $M_\mathrm{sub}$. This is described by the relation $\Delta z_{\mathrm{d}} / R_{\mathrm{d}} \simeq 8 \sum_{j=1}^N (M_{\mathrm{sub},j} / M_{\mathrm{d}})^2$, where $R_{\mathrm{d}}$ is the disk scale length, $M_{\mathrm{d}}$ is the disk mass, and $N$ is the total number of accretion events of subhalos inside a disk region ($\le 3 R_{\mathrm{d}}$). Using this relation, we find that an observed thin disk has never interacted with subhalos with a total mass of more than 15% of the disk mass. Also, a less-massive disk with a smaller circular velocity, $V_{\mathrm{c}}$ is more affected by subhalos than a disk with a larger $V_{\mathrm{c}}$, in agreement with observations. Further implications of our results for the origin of a thick disk component are also discussed.
Three-Dimensional Distribution of the ISM in the Milky Way Galaxy: II. The Molecular Gas Disk
Authors: Nakanishi Hiroyuki , Sofue Yoshiaki
Published: March 2014

We created a three-dimensional distribution map of molecular gas throughout the Milky Way galaxy using the latest ${{12\atop} \mathrm{CO}}$ ($J = 1 \hbox{--} 0$) survey data cube and the rotation curve based on the kinematic distance. The radial distribution of the molecular gas shows a central peak and a second peak around $0.5 \,R_0$ ($R_0$: the solar Galactocentric distance). The thickness of the molecular disk slightly increases from 48 pc to 160 pc with the Galactocentric distance within a radius range of 0–11 kpc. We were able to trace the Outer, the Perseus, the Sagittarius–Carina, the Scutum–Crux, and the Norma arms as logarithmic spiral arms with pitch angles of $11 {{}^{\circ }} \hbox{--} 15^\circ$. Considering that the pitch angles of the spiral arms are within this range, the Norma and the Outer arms seem to be identified as the same spiral arm. We could also trace a midplane displacement, whose amplitude is nearly constant inside a 10 kpc radius and increases beyond this radius. The ridges of the midplane displacement form the leading spiral arms.
Analysis of Adiabatic Dipolar Oscillations of Stars
Authors: Takata Masao
Published: March 2014

We theoretically discuss adiabatic dipolar oscillations of stars, fully taking into account the variation in the gravitational field. By suitably choosing the dependent variables, and using the first integral specific to dipolar oscillations, we derive the second-order system of ordinary differential equations, which is the same in form as that obtained by neglecting the Eulerian perturbation to the gravitational potential. The derived system suggests that the conventional expressions of the critical frequencies should be corrected. In addition, we present a rigorous scheme to classify the dipolar eigenmodes of linear adiabatic oscillations of spherically symmetric stars.
Radiative Transfer and Limb Darkening of Accretion Disks
Authors: Fukue Jun , Akizuki Chizuru
Published: March 2014

The transfer equation in a geometrically thin accretion disk is reexamined under the plane-parallel approximation with a finite optical depth. The emergent intensity is analytically obtained in cases with or without internal heating. For large or infinite optical depth, the emergent intensity exhibits the usual limb-darkening effect, where the intensity changes linearly as a function of the direction cosine. For a small optical depth, on the other hand, the angle-dependence of the emergent intensity changes drastically. In the case without heating, but with uniform incident radiation at the disk equator, the emergent intensity becomes isotropic for a small optical depth. In the case with uniform internal heating, limb brightening takes place for a small optical depth. We also emphasize and discuss the limb-darkening effect in an accretion disk for several cases.
A CO J = 3–2 Survey of the Galactic Center
Authors: Oka Tomoharu , Makoto Nagai , Kazuhisa Kamegai , Kunihiko Tanaka , Nobuyuki Kuboi
Published: March 2014

We have surveyed the central molecular zone (CMZ) of our Galaxy in the CO J$=$3–2 line with the Atacama Submillimeter-wave Telescope Experiment (ASTE). Molecular gas in the Galactic center shows a high J$= 3-2/J = 1-0$ intensity ratio ($\sim 0.9$), while gas in the spiral arms of the Galactic disk shows a lower ratio ($\sim 0.5$). The high-velocity compact cloud CO $0.02-0.02$ and the hyperenergetic shell CO 1.27$+$0.01, as well as gas in the Sgr A region, exhibit high J$=$3–2$/J=$1–0 intensity ratios exceeding 1.5. We also found a number of small spots of high-ratio gas. Some of these high-ratio spots have large velocity widths and some seem to be associated with nonthermal threads or filaments. These could be spots of hot molecular gas shocked by unidentified supernovae, which may be abundant in the CMZ.
Photometric Observation and Numerical Simulation of Early Superhumps in BC Ursae Majoris during the 2003 Superoutburst
Authors: Maehara Hiroyuki , Hachisu Izumi , Nakajima Kazuhiro
Published: March 2014

We carried out time-resolved photometric observations of an SU UMa-type dwarf nova, BC UMa, during its superoutburst in 2003 February. The period of early superhumps is 0.06258(13)d and the amplitude is 0.04 mag. After the early superhump phase, common superhumps with an amplitude of 0.3 mag and a period of 0.064466(16) d developed. The change rate of the superhump periods ($\dot{P}_{\rm SH}/P_{\rm SH}$) ($P_{\rm SH}$: superhump period) was positive throughout the superoutburst. The superhump period excess ($\varepsilon \equiv P_{\rm SH}P_{\rm orb}^{-1}-1$) is 3% and we derived a mass ratio of 0.13. We have modeled early superhump light curves including irradiation effects of the accretion disk and secondary star. The observed early superhumps can be reproduced when two-armed spirals appear on the accretion disk. The long-term data taken from AAVSO, VSOLJ, and VSNET indicate that BC UMa shows normal outbursts and two types of superoutbursts (short-faint and long-bright). BC UMa is the first example to show such two types of superoutbursts. The supercycle of BC UMa is between 600 d and 1000d. This suggests that BC UMa is an intermediate type of dwarf novae between WZ Sge and SU UMa.
ASTE CO (3–2) Observations of the Barred Spiral Galaxy M 83: I. Correlation between CO (3–2)/CO (1–0) Ratios and Star Formation Efficiencies
Authors: Muraoka Kazuyuki , Kohno Kotaro , Tosaki Tomoka , Kuno Nario , Nakanishi Kouichiro , Sorai Kazuo , Okuda Takeshi , Sakamoto Seiichi , Endo Akira , Hatsukade Bunyo , Kamegai Kazuhisa , Tanaka Kunihiko , Cortes Juan , Ezawa Hajime , Yamaguchi Nobuyuki , Sakai Takeshi , Kawabe Ryohei
Published: March 2014

We present CO ($J = 3$–2) emission observations with the ASTE toward the $5' \times 5'$ (or 6.6 kpc $\times$ 6.6 kpc at the distance $D$ = 4.5 Mpc) region of the nearby barred spiral galaxy M 83. We successfully resolved the major structures, i.e., the nuclear starburst region, bar, and inner spiral arms at a resolution of $22''$ (480 pc), showing a good spatial coincidence between CO and 6 cm continuum emissions. We found a global luminosity, $L'_{\rm CO(3-2)}$, of $5.1 \times 10^8$ K km s$^{-1}$ pc$^2$ within the observed region. We also found $L'_{\rm CO(3-2)}$ in a disk region ($0.5 < r < 3.5$ kpc) of $4.2 \times 10^8$ K km s$^{-1}$ pc$^2$, indicating that ($J = 3$–2) emission in the disk region significantly contributes to the global $L'_{\rm CO(3-2)}$. From a comparison of CO ($J = 3$–2) data with CO ($J = 1$–0) intensities measured with the Nobeyama 45-m telescope, we found that the radial profile of the CO ($J = 3$–2)$/$CO ($J = 1$–0) integrated intensity ratio, $R_{3-2/1-0}$, is almost unity in the central region ($r < 0.25$ kpc), whereas it drops to a constant value, 0.6–0.7, in the disk region. The radial profile of star formation efficiencies (SFEs), determined from 6 cm radio continuum and CO ($J = 1$–0) emission, shows the same trend as that of $R_{3-2/1-0}$. At the bar-end ($r \sim 2.4$ kpc), the amounts of molecular gas and the massive stars are enhanced when compared with other disk regions, whereas there is no excess of $R_{3-2/1-0}$ and SFE in that region. This means that a simple summation of the star-forming regions at the bar-end and the disk cannot reproduce the nuclear starburst of M 83, implying that the spatial variation of the dense gas fraction traced by $R_{3-2/1-0}$ governs the spatial variation of SFE in M 83.
Bispectrum and Nonlinear Biasing of Galaxies: Perturbation Analysis, Numerical Simulation, and SDSS Galaxy Clustering
Authors: Nishimichi Takahiro , Kayo Issha , Hikage Chiaki , Yahata Kazuhiro , Taruya Atsushi , Jing Yi Peng , Sheth Ravi K. , Suto Yasushi
Published: March 2014

We consider nonlinear biasing models of galaxies with particular attention to a correlation between the linear and quadratic biasing coefficients, $b_1$ and $b_2$. We first derive perturbative expressions for $b_1$ and $b_2$ in halo and peak biasing models. We then discuss our computations of the power spectra and bispectra of dark matter particles and halos using $N$-body simulation data and of volume-limited subsamples of Sloan Digital Sky Survey (SDSS) galaxies, and determine their $b_1$ and $b_2$. We find that the values of those coefficients at linear regimes ($k<0.2$$h$ Mpc$^{-1}$) are fairly insensitive to the redshift-space distortion and the survey volume shape. The resulting normalized amplitudes of the bispectra, $Q$, for equilateral triangles are insensitive to the values of $b_1$, implying that $b_2$ indeed correlates with $b_1$. The present results explain the previous finding of Kayo et al. (2004, PASJ, 56, 415) for the hierarchical relation of three-point correlation functions of SDSS galaxies. While the relations between $b_1$ and $b_2$ are quantitatively different for specific biasing models, their approximately similar correlations indicate a fairly generic outcome of the biasing due to the gravity in primordial Gaussian density fields.
Probing the Disk–Jet Connection of the Radio Galaxy 3C 120 Observed with Suzaku
Authors: Kataoka Jun , Reeves James N. , Iwasawa Kazushi , Markowitz Alex G. , Mushotzky Richard F. , Arimoto Makoto , Takahashi Tadayuki , Tsubuku Yoshihiro , Ushio Masayoshi , Watanabe Shin , Gallo Luigi C. , Madejski Greg M. , Terashima Yuichi , Isobe Naoki , Tashiro Makoto S. , Kohmura Takayoshi
Published: March 2014

We report on deep (40ks $\times$ 4) observations of the bright broad line radio galaxy 3C 120 using Suzaku. The observations were spaced one week apart, and sampled a range of continuum fluxes. An excellent broadband spectrum was obtained over two decades of frequency (0.6 to 50 keV) within each 40ks exposure. We clearly resolved the iron K emission-line complex, finding that it consists of a narrow K$\alpha$ core ($\sigma \simeq$ 110 eV or an EW of 60 eV), a 6.9 keV line, and an underlying broad iron line. Our confirmation of the broad line contrasts with the XMM-Newton observation in 2003, where the broad line was not required. The most natural interpretation of the broad line is iron K line emission from a face-on accretion disk that is truncated at ~ 10 rg. Above 10 keV, a relatively weak Compton hump was detected (reflection fraction of R$\simeq$ 0.6), superposed on the primary X-ray continuum of $\Gamma \simeq$ 1.75. Thanks to the good photon statistics and low background of the Suzaku data, we clearly confirm the spectral evolution of 3C 120, whereby the variability amplitude decreases with increasing energy. More strikingly, we discovered that the variability is caused by a steep power-law component of $\Gamma \simeq$ 2.7, possibly related to non-thermal jet emission. We discuss our findings in the context of similarities and differences between radio-loud/quiet objects.
Multi-Slit Imaging Spectroscopy Technique: Catalog of Intracluster Planetary Nebulae in the Coma Cluster
Authors: Arnaboldi Magda , Gerhard Ortwin , Okamura Sadanori , Kashikawa Nobunari , Yasuda Naoki , Freeman Kenneth C.
Published: March 2014

With a new multi-slit imaging spectroscopy (MSIS) technique pioneered at the 8.2 m Subaru telescope and the Faint Object Camera and Spectrograph, we detect and measure the line-of-sight velocities of 40 intracluster planetary nebula candidates associated with the diffuse intracluster population of stars in the Coma cluster core, at nearly 100 Mpc distance. We describe the method for extracting the single two-dimensional spectra from the MSIS image, discuss the criteria for the identification of the emission line objects, and describe the procedure to compute their $\alpha, \delta$ (J2000) coordinates. We present the catalog of the intracluster planetary nebula candidates, their spatial location in the surveyed field, and their distribution in the velocity–magnitude plane. Finally, we comment on possible population effects and the use of these planetary nebulae to confirm the distance to the Coma cluster.
An SiO Maser Search off the Galactic Plane
Authors: Deguchi Shuji , Fujii Takahiro , Ita Yoshifusa , Imai Hiroshi , Izumiura Hideyuki , Kameya Osamu , Matsunaga Noriyuki , Miyazaki Atsushi , Mizutani Arihiro , Nakada Yoshikazu , Nakashima Jun-ichi , Winnberg Anders
Published: March 2014

We searched for the SiO $J=1$-0, $v= 1$ and 2 maser lines at $\sim 43$ GHz in 277 2 MASS/MSX/IRAS sources off the Galactic plane ($\vert b\vert\gtrsim 3^{\circ}$), which resulted in 119 (112 new) detections. Among the new detections, two are very faint objects with MSX 12$\mu$m flux densities below 2 Jy. These are likely to be O-rich AGB-stars associated with dwarf-galaxy tidal tails. The sample also includes medium bright MSX objects at moderately high galactic latitudes ($3^{\circ}<\vert b\vert<5^{\circ}$) and in the IRAS gap at higher latitudes. A signature of a warp of the inner Galactic disk is found for a disk subsample. This warp appears relatively strongly in the area of $0^{\circ}<l<45^{\circ}$ and $3^{\circ}<\vert b\vert<5^{\circ}$. We also found a group of stars that does not follow to the Galactic rotation. This feature appears in the Galactic disk at $l\sim 27^{\circ}$, and extends more than $15^{\circ}$ in the galactic latitude, like a stream of tidal debris from a dwarf galaxy.
HETE-2 Observations of the X-Ray Flash XRF 040916
Authors: Arimoto Makoto , Kawai Nobuyuki , Suzuki Motoko , Sato Rie , Pazmino Nicolas Vasquez , Shimokawabe Takashi , Ishimura Takuto , Kotoku Jun’ichi , Yoshida Atsumasa , Tamagawa Toru , Shirasaki Yuji , Matsuoka Masaru , Nakagawa Yujin , Ishikawa Nobuyuki , Kobayashi Akina , Sugita Satoshi , Takahashi Ichiro , Kuwahara Makoto , Yamauchi Makoto , Takagishi Kunio , Hatsukade Isamu , Atteia Jean-Luc , Pelangeon Alexandre , Vanderspek Roland , Graziani Carlo , Prigozhin Gregory , Villasenor Joel , Jernigan J. Garrett , Crew Geoffrey B. , Hurley Kevin , Sakamoto Takanori , Ricker George R. , Woosley Stanford E. , Butler Nat , Levine Al , Doty John P. , Donaghy Timothy Q. , Lamb Donald Q. , Fenimore Edward E. , Galassi Mark , Boer Michel , Dezalay Jean-Pascal , Olive Jean-François , Braga Joao , Manchanda Ravi , Pizzichini Graziella
Published: March 2014

A long X-ray flash was detected and localized by instruments aboard the High Energy Transient Explorer II (HETE-2) at 00:03:30 UT on 2004 September 16. The position was reported to the GRB Coordinates Network (GCN) approximately 2 hours after the burst. This burst consisted of two peaks separated by $\sim 200$ s, with durations of about 110 s and 60 s. We analyzed the energy spectra of the 1st and 2nd peaks observed with the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE). We discuss the origin of the 2nd peak in terms of the flux variabilities and timescales. We find that it is most likely to be part of prompt emission, and is explained by a long-acting engine model. This feature is similar to some bright X-ray flares detected in the early afterglow phase of bursts observed by the Swift satellite.