bluuebunny/crossref_metadata_2025 huggingface dataset:
Virgo High-Resolution CO Survey: IV. Spiral-Driven Gas Dynamics in the Non-Barred Seyfert Galaxy NGC 4501
Authors: Onodera Sachiko , Koda Jin , Sofue Yoshiaki , Kohno Kotaro
Published: March 2014

We report on high-resolution interferometer observations of the ${{12\atop} \mathrm{CO}}$ ($J = 1 \hbox{--} 0$) emission in the central 5 kpc region of the Seyfert 2 galaxy NGC 4501. The observations were made using the Nobeyama Millimeter Array during a long-term CO line survey of Virgo spirals. The major features are: (1) a nuclear concentration with a radius of $r\sim 5^{\prime\prime}$ (390 pc), which is resolved into double peaks, and (2) spiral arms which extend out from the nuclear region. The nuclear component has a mass of $1.3 \times 10^8 \,{{{M}_{\odot}}}$, which corresponds to $\sim 3.5\%$ of the dynamical mass, and shows a slight non-circular motion. The double peaks are separated by $\sim {4\rlap {.}{}^{\mathrm {\prime \prime }}7}$ ($370 \:\mathrm{pc}$), and located on the root of optical spiral arms in a HST image. The gas arms are associated with the spiral dust lanes, and are linked to the central double peaks. The non-circular motions along the molecular arms indicate the fact that the gas is driven by the density wave, rather than the stochastic processes. We calculated the gas cloud orbits in a stellar spiral potential, and explained the observed CO spiral arms and non-circular motions. We suggest that the central gas condensation arises from spiral-driven gas transfer. We estimated and compared the effect of two possible mechanisms of angular-momentum transfer: galactic shock and gravitational torques. We discuss that the galactic shock is dominant.
Radiative Shocks in Rotating Accretion Flows around Black Holes
Authors: Okuda Toru , Teresi Vincenzo , Toscano Elena , Molteni Diego
Published: March 2014

It is well known that rotating inviscid accretion flows with adequate injection parameters around black holes could form shock waves close to the black holes, after the flow passes through the outer sonic point and can be virtually stopped by the centrifugal force. We numerically examined such shock waves in 1D and 2D accretion flows, while taking account of the cooling and heating of the gas and the radiation transport. The numerical results show that the shock location shifts outward compared with that in adiabatic solutions, and that a more rarefied ambient density leads to a more outward shock location. In 2D-flow, we find an intermediate frequency QPO behavior of the shock location, as is observed in the black hole candidate GRS 1915$+$105.
Partial Covering Interpretation of the X-Ray Spectrum of the NLS1 1H 0707−495
Authors: Tanaka Yasuo , Boller Thomas , Gallo Luigi , Keil Ralph , Ueda Yoshihiro
Published: March 2014

The X-ray spectrum of 1H 0707$-$495 obtained with XMM-Newton showing a deep flux drop at $\sim 7 \,\mathrm{keV}$ (Boller et al. 2002) is studied based on the partial covering concept. The previously inferred extreme iron overabundance can be reduced down to ${}\sim 3\times$ solar if the hard component gradually steepens at high energies. The spectral shape supports that 1H 0707$-$495 is an AGN analogue of the galactic black-hole binaries in the soft state. Interpreting the soft excess as the emission from an optically-thick disk, the minimum black hole mass $M$ is estimated to be $2 \cdot 10^6 \,{{{M}_{\odot}}}$ from the intrinsic luminosity corrected for partial covering. Based on the slim disk model, the observed disk temperature implies that the luminosity is close to the Eddington limit. The rapid and large flux variations with little change in the spectral shape can also be explained, if not all, as due to changes in the partial covering fraction. Partial covering may account for the large variability characteristics of NLS1.
A Search for H
$\alpha$
Absorption in the Exosphere of the Transiting Extrasolar Planet HD 209458b
Authors: Winn Joshua N. , Suto Yasushi , Turner Edwin L. , Narita Norio , Frye Brenda L. , Aoki Wako , Sato Bun’ei , Yamada Toru
Published: March 2014

There is evidence that the transiting planet HD 209458b has a large exosphere of neutral hydrogen, based on a 15% decrement in Lyman- $\alpha$ flux that was observed by Vidal-Madjar et al. during transits. Here we report upper limits on $\mathrm{H}\alpha$ absorption by the exosphere. The results are based on optical spectra of the parent star obtained with the Subaru High Dispersion Spectrograph. Comparison of the spectra taken inside and outside of transit reveals no exospheric $\mathrm{H}\alpha$ signal greater than 0.1% within a 5.1?Åband (chosen to have the same $\Delta\lambda/\lambda$ as the 15% $\mathrm{Ly}\alpha$ absorption). The corresponding limit on the column density of $n=2$ neutral hydrogen is $N_2 \lesssim 10^9 \,\mathrm{cm}^{-2}$ . This limit constrains proposed models involving a hot ( $\sim 10^4 \,\mathrm{K}$ ) and hydrodynamically escaping exosphere.
General Relativity and the Pseudo-Newtonian Potential
Authors: Fukue Jun
Published: March 2014

We propose a metric correction on velocities calculated from the Paczyński and Wiita (1980) pseudo-Newtonian potential, in order to avoid the divergence to infinity at the Schwarzschild radius. Cold disk flows onto a black hole are briefly discussed.
Sunyaev-Zel’dovich Effect toward Distant Galaxy Clusters at 43 GHz; Observation and Data
Authors: Tsuboi Masato , Miyazaki Atsushi , Kasuga Takashi , Kuno Nario , Sakamoto Akihiro , Matsuo Hiroshi
Published: March 2014

We have observed the Sunyaev–Zel’dovich (SZ) effect on eight X-ray bright galaxy clusters from $z = 0.18$ to 0.55 at 43 GHz using a newly developed 6-beam receiver installed on the Nobeyama 45-m telescope. The SZ effects were detected for all clusters as temperature decrements of 0.5–1 mK at the center. The Hubble constant is estimated to be $H_{0} = 64 \pm 17 \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{Mpc}^{-1}$ for a flat $\Lambda$CDM cosmology, which shows good agreement with other SZ effect observations. Although most of the observed profiles should be described by the isothermal spherical $\beta$-model density distribution, the deviation from the model seems to be larger for clusters with an irregular distribution in the X-ray image than those without such an irregularity.
A Period Study of the Near-Contact Binary IR Cassiopeiae
Authors: Li-Ying Zhu , Sheng-Bang Qian , Fu-Yuan Xiang
Published: March 2014

The near-contact binary IR Cas was observed in 2003 October. Two new observed times of the primary minimum were derived. All of the available eclipse times, including the new ones, spanning 90 years were analyzed. It was shown that the period change of the system is very complex. A period oscillation with a period of 53.24 years and an amplitude of about 0.0133 days were found, while it undergoes a secular decrease at a rate of $dP/dt =-1.18 \times 10^{-7} (\pm0.09) \,\mathrm{d} \,\mathrm{yr}^{-1}$. The mechanisms that could explain the period changes and the evolutionary state of the system are discussed.
2003 Mars Report from Cooperative Observation Networks. I. Pre-Opposition
Authors: Nakakushi Takashi , Adachi Makoto , Iga Yuichi , Tokimasa Noritaka
Published: March 2014

We have two networks for cooperative Mars observations in Japan: Nishi-Harima Astronomical Observatory Mars Cooperative Observation and Association of Lunar and Planetary Observers in Japan. This paper is a summary of 3515 images collected by the two networks during the first half of the last apparition from 2002 October 18 through 2003 August 31, corresponding to the period of $L_{\mathrm{s}} \sim {83{}^{\mathrm {\circ }}} \hbox{--} {252{}^{\mathrm {\circ }}}$ ($L_{\mathrm{s}}$ is the areocentric longitude of the Sun). During this period, many interesting phenomena were observed. (1) Two local dust storms appeared about $L_{\mathrm{s}} = {214{}^{\mathrm {\circ }}}$ and $L_{\mathrm{s}} = {231{}^{\mathrm {\circ }}}$. (2) Hellas was obscured just before the occurrence of the first dust storm. This may be relevant to the dust storm. (3) Blue clearings were observed. The phenomena in this apparition may be attributed to the optical properties of the ground for the scattering of light. (4) Dark markings in the south polar cap (SPC) developed as the SPC receded in mid-spring of the southern hemisphere. Also, some bright spots appeared on the SPC. (5) The south polar hood receded polewards and SPC began to be observed at about $L_{\mathrm{s}} \sim {185{}^{\mathrm {\circ }}}$ (mid-May). (6) The north polar hood was not detected until $L_{\mathrm{s}} \sim {180{}^{\mathrm {\circ }}}$ in this apparition. (7) The low-latitude cloud belt had been observed until mid-May. In the dissipation phase, a less cloud area appeared in longitudes of 170${{}^{\mathrm {\circ }}}$-200${{}^{\mathrm {\circ }}}$ W.
A Shape-and-Density Model of the Putative Binary EKBO 2001QG298
Authors: Takahashi Shigeru , Ip Wing-Huen
Published: March 2014

Recent observations of the Edgeworth-Kuiper belt object (EKBO) 2001 $\mathrm{QG}_{298}$ (Sheppard, Jewitt 2004) have shown that the lightcurve of this object has a very large amplitude ($1.14 \pm 0.04 \,\mathrm{mag}$), indicating that it is either of an elongated shape or of a binary structure with two components of similar sizes nearly in contact with each other. On the basis of these interesting published data, we employed Roche binary lightcurve simulations to construct a shape model of EKBO 2001 $\mathrm{QG}_{298}$. The shape parameters of the best-fitted model were $260\ (164) \times 205 (130) \times 185\ (116) \,\mathrm{km}$ for the primary, and $265 (168)\times 160\ (102) \times 150\ (94) \,\mathrm{km}$ for the secondary in the case of an albedo of 0.04 (0.10). An additional result of this calculation is that the average bulk density of the contact binary system could be estimated to be $630 \,\mathrm{kg} \,\mathrm{m}^{-3}$. This value is similar to that of several icy moons of Saturn with a diameter of less than 200 km. We have also used the Jacobi ellipsoidal approximation to compute the shape of one of the largest EKBOs, Varuna. The corresponding shape parameters are $a : b : c = 1.00 : 0.76 : 0.50$. The lower limit of the bulk density is $\rho \ge 1000 \,\mathrm{kg} \,\mathrm{m}^{-3}$. These results are in good agreement with the published values of Jewitt and Sheppard (2002), and are consistent with their suggestion that larger icy bodies have higher densities (Sheppard, Jewitt 2002).
Offsets between Hα and CO Arms of a Spiral Galaxy, NGC 4254: A New Method for Determining the Pattern Speed of Spiral Galaxies
Authors: Egusa Fumi , Sofue Yoshiaki , Nakanishi Hiroyuki
Published: March 2014

We examined the offsets between H II regions and molecular clouds belonging to spiral arms of a late-type spiral galaxy, NGC 4254 (M99). We used a high-resolution ${{12\atop} \mathrm{CO}}$ ($J = 1 \hbox{--} 0$) image obtained by Nobeyama Millimeter Array (NMA) and an $\mathrm{H}\alpha$ image. We derived angular offsets ($\theta$) in the galactic disk, and found that they show a linear dependence on the angular rotation velocity of the gas ($\Omega_{\mathrm{G}}$). This linear relation can be expressed by the equation $\theta = (\Omega_{\mathrm{G}}-\Omega_{\mathrm{P}}) \cdot t_{\mathrm{H}\alpha}$, where $\Omega_{\mathrm{P}}$ and $t_{\rm H\alpha}$ are constant. Here, $\Omega_{\mathrm{P}}$ corresponds to the pattern speed of the spiral arms and $t_{\mathrm{H}\alpha}$ is interpreted as being the timescale between the peak compression of the molecular gas in the spiral arms and the peak of massive star formation. We could thus determine $\Omega_{\mathrm{P}}$ and $t_{\mathrm{H}\alpha}$ simultaneously by fitting a line to our $\theta \hbox{--} \Omega_{\mathrm{G}}$ plot, if we assume they are constant. From the plot for NGC4254, we obtained $t_{\mathrm{H}\alpha} = (4.8 \pm 1.2) \times 10^6 \,\mathrm{yr}$ and $\Omega_{\mathrm{P}} = 26^{+10}_{-6} \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{kpc}^{-1}$, which are consistent with previous studies. We suggest that this $\theta \hbox{--} \Omega_{\mathrm{G}}$ plot can be a new tool to determine the pattern speed and the typical timescale needed for star formations.
Periods of Activity Cycle of Polar Faculae
Authors: Li Kejun , Qiu Jiong , Su Tongwei , Irie Makoto , Gao Pengxin
Published: March 2014

The periodicity of the high-latitude solar activity has been studied using monthly-averaged polar facula counts obtained at the National Astronomical Observatory of Japan (NAOJ) and the annual number of polar faculae observed by Mount Wilson Observatory (MWO). The complex Morlet wavelet was utilized to analyze the periodicity in the two data sets. For the NAOJ and MWO data, the most eminent period is 10.89 and 10.48 years, respectively, which is the Schwabe period of the high-latitude solar activity. All possible periods detected at the low-latitude solar activity were also detected in the two data sets, and we found no distinct periods existing just in the two data sets of the high-latitude solar activity. The periodicity of the high-latitude solar activity is inferred to be the same as that of the low-latitude solar activity.
A Deeply Eclipsing SU UMa-Type Dwarf Nova with the Shortest Orbital Period, XZ Eridani
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Bolt Greg , Cook Lewis M. , Monard Berto , Stubbings Rod , Torii Ken’ichi , Kiyota Seiichiro , Nogami Daisaku , Tanabe Kenji , Starkey Donn R. , Miyashita Atsushi
Published: March 2014

We discovered superhumps in an eclipsing dwarf nova, XZ Eridani, during an outburst in 2003 January–February. We determined the orbital and average superhump periods to be $0.061159602 \pm 0.000000044 \,\mathrm{d}$ and $0.062808\pm 0.000017 \,\mathrm{d}$, respectively. Our observations thus established that XZ Eri belongs to a rare class of deeply eclipsing SU UMa-type dwarf novae. The object has the shortest orbital period among seven known objects in this class. The superhump period decreased with time during a mid-plateau phase of the superoutburst, as observed in a number of ordinary, long-period SU UMa stars. During an early phase of the superoutburst, however, the superhump period increased, as observed in several short-period systems. XZ Eri is a unique object with which we can study the evolution of accretion-disk structures through eclipses during the phase of the superhump period increase.
Light Curves of Novae on VSNET
Authors: Kiyota Seiichiro , Kato Taichi , Yamaoka Hitoshi
Published: March 2014

We present a comprehensive atlas of light curves of 41 classical novae based on VSNET data, which contains many observations of these objects contributed from worldwide. The objects include all well-established classical novae discovered between 1993 and 2003 June, as well as a summary of basic data of these novae.
V803 Centauri: Helium Dwarf Nova Mimicking a WZ Sge-Type Superoutburst
Authors: Kato Taichi , Stubbings Rod , Monard Berto , Butterworth Neil D. , Bolt Greg , Richards Tom
Published: March 2014

We observed the long-term behavior of the helium dwarf nova V803 Cen, and clarified the existence of at least two distinct states (a state with 77-d supercycles and a standstill-like state) that interchangeably appeared with a time-scale of 1–2 yr. We also conducted a time-resolved CCD photometry campaign during a bright outburst in 2003 June. The overall appearance of the outburst closely resembles that of the late stage of the 2001 outburst of WZ Sge, consisting of the initial peak stage (superoutburst plateau), the dip, and the oscillating (rebrightening) states. During the initial peak stage, we detected a large-amplitude superhump-type variation with a period of $0.018686(4) \,\mathrm{d} = 1614.5(4) \,\mathrm{s}$, and during the oscillation stage we detected variations with a period of $0.018728(2) \,\mathrm{d} = 1618.1(2) \,\mathrm{s}$. We consider that the former period better represents the superhump period of this system, and the latter periodicity may be better interpreted as arising from late superhumps. The overall picture of the V803 Cen outburst resembles that of a WZ Sge-type outburst, but apparently with a higher mass-transfer rate than that in hydrogen-rich WZ Sge-type stars. We suggest that this behavior may be either the result of difficulty in maintaining the hot state in a helium disk, or the effect of an extremely low tidal torque resulting from the extreme mass ratio.
AGN Black Hole Masses and Methods to Estimate the Mass
Authors: Xie Guang-Zhong , Chen Luo-En , Xie Zhao-Hua , Ma Li , Zhou Shu-Bai
Published: March 2014

The black hole mass, along with the ratio of the accretion rate to the Eddington accretion rate, is a fundamental parameter of active galactic nuclei. Using our new method to estimate the black hole mass, we developed our sample and estimated black hole masses, indicated by $M_\mathrm{H}$ for 12 blazars. We compared 12 cases, for each of which the relevant black hole mass was also estimated by the $L_\mathrm{5100} \hbox{--} R_\mathrm{BLR}$ relation or the $M_\mathrm{BH} \hbox{--} \sigma$ correlation method, which is indicated by $M_\mathrm{\sigma}$. We also found that (1) $M_\mathrm{H}$ values are systematically lower than $M_\mathrm{\sigma}$, but the differences between $M_\mathrm{\sigma}$ and $M_\mathrm{H}$ are very small for most sources; (2) there is a significant correlation between $M_\mathrm{\sigma}$ and $M_\mathrm{H}$, the correlation coefficient being $r = 0.66$ with a chance probability of $p \sim 1.9 \times 10^{-2}$. Based on these properties mentioned above, we have shown that the small systematical difference between $M_\mathrm{\sigma}$ and $M_\mathrm{H}$ is probably due to some systematic errors in our method.
Development of Real-Time Frame Selector 2 and the Characteristic Convective Structure in the Emerging Flux Region
Authors: Kozu Hiromichi , Kitai Reizaburo , Funakoshi Yasuhiro
Published: March 2014

A new image-grabbing system, Real-Time Frame Selector 2 (RTFS2), was developed and installed in the Domeless Solar Telescope at Hida Observatory. The purpose of this system is to acquire high-quality images in ground-based observations. We observed the emerging flux region NOAA 8582 in the G-band wavelengths from 20:59 UT to 23:32 UT on 1999 June 11 with RTFS2. Simultaneous $\mathrm{H}\alpha$ line center and wing wavelength observations with a Lyot filter system showed emerging flux loops and surge activities in this region. We applied a Local Correlation Tracking Method to the G-band data set in order to derive the horizontal convective structure in the upper convective zone. In addition to a meso-scale convective structure, we found divergent-flow structures under emerging flux loops, which were stable during the whole observation period, and located at the middle of the foot points of each flux loop. We suggest that the divergent-flow structure is a newly found characteristic of emerging flux regions.
VSOP Observations of the Gamma-Ray Sources J1733−1304, J1625−2527, and J1015+4926
Authors: Nakagawa Akiharu , Edwards Philip G. , Murata Yasuhiro , Wajima Kiyoaki , Omodaka Toshihiro
Published: March 2014

We present images from VSOP (VLBI Space Observatory Programme) and VLBA (Very Long Baseline Array) observations of the active galactic nuclei J1733$-$1304, J1625$-$2527, and J1015$+$4926. These three sources have been identified as possible counterparts to gamma-ray sources in the third EGRET catalog. In general, the counterparts to extragalactic EGRET sources have very compact structure, with brightness temperatures ($T_{\mathrm{b}}$) greater than $10^{11} \hbox{--} 10^{12} \,\mathrm{K}$. Evidence for compactness in gamma-ray emitting AGNs is also given by the variability seen from gamma-ray to radio frequencies. In this report, we compare the images of the three sources with previously published images and also examine jet motions and spectral indices. The measured $T_{\mathrm{b}}$ of J1733$-$1304 are an order of magnitude lower than previous $T_{\mathrm{b}}$ measurements, suggesting that the VSOP observations were made while the source was in a relatively quiescent state after the radio outburst of 1995–1997. The relatively low $T_{\mathrm{b}}$ of J1625$-$2527 is also consistent with the highly variable nature of this source. A comparison of the VSOP observation of J1015$+$4926 with a VLBA image made 2.2 yr earlier suggests the existence of stationary jet components in this source.
Photometric Study of the Binary System V397 Cephei
Authors: Bulut Ibrahim , Demircan Osman , Budding Edwin , Erdem Ahmet , Çiçek Caner , Esenoğlu Hasan , Soydugan Faruk , Soydugan Esin , Değirmenci Ömer L. , Bozkurt Zeynep , Yakut Kadri
Published: March 2014

The first ground-based $UBV$ observations (2001, Inf. Bull. Variable Stars, 5129) of V397 Cep were analyzed by using the Wilson–Devinney method, and the results were compared with others in the literature. A consistent geometry with a photometric mass-ratio close to unity and an eccentric orbit of $e \simeq 0.13$ was found. The longitude of the periastron ($\omega$) was found significantly different for two different light curves, which is strongly suggestive of an apsidal motion with a period of about 300 yr. This makes V397 Cep an important candidate for studies of apsidal motion.
Polytropic Model of Pulsars with a Strongly Magnetized Core and Their Spin Evolutions
Authors: Takahashi Koichi
Published: March 2014

A model of pulsar that has a magnetized core is presented and the behavior in evolution of spin and luminosity is analyzed. The stars are supposed to be polytropes, thereby rendering all physical quantities calculable with any desired precision. The mechanism of energy dissipation consists of interactions between the magnetic core and a shell as well as the magnetic dipole radiation. Owing to a huge electronic conductivity, the interaction between the core and the shell can be so weak that differential rotation of the two stellar components is allowed over very long terms. Identifying the rotation period of the magnetized core as the pulse-period of pulsar, we find that there exists an almost stationary era in the evolution of the pulse-period, during which the luminosity is dominated not by the dipole radiation but by the core-shell interaction. Implications of the model on anomalous X-ray pulsars 1E 1841$-$045 and 1E 2259$+$586 are discussed.
Three-Mirror Anastigmat Telescope with an Unvignetted Flat Focal Plane
Authors: Nariai Kyoji , Iye Masanori
Published: March 2014

A new optical design concept of telescopes to provide an aberration-free, wide field, unvignetted flat focal plane is described. The system employs three aspheric mirrors to remove aberrations, and provides a semi-circular field of view with minimum vignetting. The third mirror reimages the intermediate image made by the first two-mirror system with a magnification factor on the order of unity. The present system contrasts with the Korsch system where the magnification factor of the third mirror is usually much larger than unity. Two separate optical trains can be deployed to cover the entire circular field, if necessary.
Spectral Evolution of a Luminous Compact X-Ray Source in NGC 253 with Chandra and XMM-Newton Observatories
Authors: Tanaka Takaaki , Sugiho Masahiko , Kubota Aya , Makishima Kazuo , Takahashi Tadayuki
Published: March 2014

Spectral studies of a luminous X-ray source, NGC 253 X21, are presented based on archival Chandra and XMM-Newton data. The Chandra observation on 1999 December 16 detected the source at a bolometric luminosity of $0.3 \times 10^{39} \,\mathrm{erg} \,\mathrm{s}^{-1}$ (assuming isotropic emission), while an XMM-Newton observation on 2000 June 3 revealed a short-term source variation in the range of $(0.6 \hbox{--} 1.3) \times 10^{39} \,\mathrm{erg} \,\mathrm{s}^{-1}$. All spectra from these observations were successfully modeled by emission from an optically thick accretion disk. The average inner disk radius was kept constant at $63 \cdot (\cos60^\circ/\cos i)^{1/2} \,\mathrm{km}$, where $i$ is the disk inclination, and did not vary significantly, while the disk inner temperature changed in the range of 0.9–1.4 keV. Assuming that this object is an accreting Schwarzschild black hole, and that the disk inner radius coincides with its last stable orbit, the mass of the black hole is estimated to be $\sim 7\,{{{M}_{\odot}}}$. The disk luminosity corresponds to $(30 \hbox{--} 120) \cdot(\cos60^\circ/\cos i)\%$ of the Eddington limit of this black hole. Therefore, this luminous X-ray source, NGC 253 X21, is understood consistently to be an accreting stellar mass black hole in the standard disk state.
A Resonance Model of Quasi-Periodic Oscillations of Low-Mass X-Ray Binaries
Authors: Kato Shoji
Published: March 2014

We try to understand the quasi-periodic oscillations (QPOs) in low-mass neutron-star and black-hole X-ray binaries by a resonance model in warped disks with precession. Our main concern is high-frequency QPOs, hectohertz QPOs, and horizontal-branch QPOs in the z sources and the atoll sources, and the corresponding QPOs in black-hole X-ray binaries. Our resonance model can qualitatively, but systematically, explain these QPOs by regarding hectohertz QPOs as a precession of warp.
An Equilibrium Dark Matter Halo with the Burkert Profile
Authors: Liu Wen-Hao , Fu Yan-Ning , Deng Zu-Gan , Huang Jie-Hao
Published: March 2014

In this paper a prescription for generating an equilibrium spherical system depicted with cuspy density profiles is extended to a core density profile, the Burkert profile, which is observationally more suitable to dwarfs. By using a time-saving Monte Carlo method instead of $N$-body simulations, we show that the Burkert halo, which is initialized with a distribution function that depends only on energy, is in a practically stable equilibrium. The one generated with the local Maxwellian approximation is unstable, where the flat core density structure tends to steepen. This is fundamentally different from a previous study on a halo with a cuspy density profile. The deviation of the unstable “Burkert” from the initial Burkert profile is found to be closely related to taking a Gaussian as the velocity distribution at any given point. The significance of not using the local Maxwellian approximation is further demonstrated by exploring the dynamical evolution of compact super star clusters (SSCs) in the Burkert halo. In particular, the local Maxwellian approximation results in underestimating the dynamical friction and overestimating sinking time scale. Accordingly, this leads to a lower probability of forming massive bulges and young nuclear star clusters in bulgeless galaxies.
Secular Evolution of Barred Galaxies with Massive Central Black Holes
Authors: Hozumi Shunsuke , Hernquist Lars
Published: March 2014

The influence of central black holes on the dynamical evolution of bars in disk galaxies was examined. Once a bar formed by a dynamical instability in an infinitesimally thin stellar disk was fully developed, a black hole (BH) was adiabatically added at the center of the disk. Our results indicate that a bar can be completely destroyed, in a practical sense, in a time much smaller than the Hubble time if the central BH mass exceeds about 0.5% of the disk mass. Since this implied minimum BH mass for bar destruction is on the order of $10^{8.5} \,{{{M}_{\odot}}}$ for a typical disk galaxy, this process could occur in the real Universe. The bar amplitude decreases gradually with time after the BH has grown up to its full mass. Surface-of-section plots indicate that the bar dissolution originates from the chaotic behavior of bar-supporting orbits. In addition, the scale length and the radial velocity dispersion of the disk after bar dissolution become much larger than those of the initial axisymmetric disk. This finding suggests that it is possible to discriminate between genuine non-barred galaxies and bar-dissolved galaxies induced by massive central BHs from the viewpoint of structural properties.
PGPG: An Automatic Generator of Pipeline Design for Programmable GRAPE Systems
Authors: Hamada Tsuyoshi , Fukushige Toshiyuki , Makino Junichiro
Published: March 2014

We have developed PGPG (Pipeline Generator for Programmable GRAPE), software that generates the low-level design of the pipeline processor and communication software for FPGA-based computing engines (FBCEs). An FBCE typically consists of one or multiple FPGA (Field-Programmable Gate Array) chips and local memory. Here, the term “Field-Programmable” means that one can rewrite the logic implemented to the chip after the hardware is completed, and therefore a single FBCE can be used to calculate various functions, for example pipeline processors for gravity, SPH interaction, or image processing. The main problem with FBCEs is that the user needs to develop the detailed hardware design for the processor to be implemented to FPGA chips. The PGPG software generates all necessary design descriptions, except for the application software, itself, from a high-level design description of the pipeline processor in the PGPG language. The PGPG language is a simple language, specialized to the description of pipeline processors. Thus, the design of a pipeline processor in PGPG language is much easier than the traditional design. For real applications, such as the pipeline for gravitational interactions, the pipeline processor generated by PGPG has achieved a performance similar to that of hand-written code.
A Survey of NB921 Dropouts in the Subaru Deep Field
Authors: Shioya Yasuhiro , Taniguchi Yoshiaki , Ajiki Masaru , Nagao Tohru , Murayama Takashi , Sasaki Shunji S. , Sumiya Ryoko , Hatakeyama Yuichiro , Morioka Taichi , Yokouchi Asuka , Koizumi Osamu , Takahashi Mari I. , Kashikawa Nobunari
Published: March 2014

In order to search for high-redshift galaxies beyond $z = 6.6$ in the Subaru Deep Field, we investigated NB921-dropout galaxies where NB921 is a narrowband filter centered at 919.6 nm with FWHM of 13.2 nm for the Suprime-Cam on the Subaru Telescope. There are no secure NB921-dropout candidates brighter than $z^\prime = 25.5$. Based on this result, we discuss the UV luminosity function of star-forming galaxies at $z \gt 6.6$.
Detection of the Velocity Drift of High-Velocity Water Maser Features of a LINER NGC 4258: Evidence of a Spiral Maser Disk
Authors: Yamauchi Aya , Sato Naoko , Hirota Akihiko , Nakai Naomasa
Published: March 2014

We monitored the velocities of high-velocity features for a $\mathrm{H}_2 \mathrm{O}$ megamaser, NGC 4258, using the 45-m telescope of the Nobeyama Radio Observatory. The spiral shock model of maser disks predicts that the red-shifted features of observed maser spectra decelerate and the blue-shifted features accelerate for trailing arms. To confirm this model, we measured the velocity drift rates. Using the data of 1992–2005, the drift rate was detected to be ${\overline{a} =-0.036 \pm 0.007 \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{yr}^{-1}}$ on the average for 10 red-shifted features. The drift rate of a blue-shifted feature was $a = 0.20 \pm 0.10 \,\mathrm{km} \,\mathrm{s}^{-1} \,\mathrm{yr}^{-1}$. These results are consistent with a prediction of the spiral shock model. The pitch angles of the spirals were obtained to be $\overline{\theta_{\mathrm{p}}} = {2{}^{\mathrm {\circ }}} \pm {1{}^{\mathrm {\circ }}}$ on the average for the red-shifted features and $\theta_{\mathrm{p}} = {13{}^{\mathrm {\circ }}} \pm {7{}^{\mathrm {\circ }}}$ for the blue-shifted feature from the measured drift rates.
An Intermediate-Band Imaging Survey for High-Redshift Lyman Alpha Emitters: The Mahoroba-11
Authors: Yamada Sanae F. , Sasaki Shunji S. , Sumiya Ryoko , Umeda Kazuyoshi , Shioya Yasuhiro , Ajiki Masaru , Nagao Tohru , Murayama Takashi , Taniguchi Yoshiaki
Published: March 2014

We present results of our intermediate-band optical imaging survey for high-$z$ Ly$\alpha$ emitters (LAEs) using the prime focus camera, Suprime-Cam, on the 8.2 m Subaru telescope. In our survey, we used eleven filters: four broad-band filters ($B, R_{\mathrm{C}}, i^\prime$, and $z^\prime$) and seven intermediate-band filters covering from 500 nm to 720 nm. We call this imaging program the Mahoroba-11. The seven intermediate-band filters were selected from a series of IA filters, which is the Suprime-Cam intermediate-band filter system, whose spectral resolution is $R = 23$. Our survey was made in a $34^\prime \times 27^\prime$ sky area in the Subaru XMM Newton Deep Survey Field. We found 409 IA-excess objects, which provided us with a large photometric sample of strong emission-line objects. Applying the photometric redshift method to this sample, we obtained a new sample of 198 LAE candidates at $3 < z < 5$. We found no evidence for evolutions of the number density and the star-formation rate density (SFRD) for LAEs with $\log L(\mathrm{Ly}\alpha) (\,\mathrm{erg} \,\mathrm{s}^{-1}) \gt 42.67 \log L(\mathrm{Ly}\alpha) (\,\mathrm{erg} \,\mathrm{s}^{-1}) \gt 42.67$ between $z \sim 3$ and $z \sim 5$.
Virgo High-Resolution CO Survey: V. Circumnuclear Elliptical Ring in NGC 4569
Authors: Nakanishi Hiroyuki , Sofue Yoshiaki , Koda Jin
Published: March 2014

We present high-resolution (${1\rlap {.}{}^{\mathrm {\prime \prime }}8}$–${4\rlap {.}{}^{\mathrm {\prime \prime }}5}$) CO data of the Virgo spiral galaxy NGC 4569, obtained using the Nobeyama Millimeter Array. We found that the molecular gas is highly concentrated in the circumnuclear region with two off-center peaks. A CO image with the highest angular resolution of $ {2\rlap {.}{}^{\mathrm {\prime \prime }}0} \times {1\rlap {.}{}^{\mathrm {\prime \prime }}8}$ shows that six blobs likely form a circumnuclear elliptical ring (CER) with a semimajor axis of 720 pc. The CER shows a strongly twisted velocity field, and the Position–velocity diagram shows significant forbidden velocity components. These kinetic features are understood as being non-circular motion due to a bar-potential. We found that the CER coincides with the $\mathrm{H}\alpha$ bright central core and that the mass ratio of the molecular gas to the dynamical mass is about 18%. These results support a gaseous inflow scenario induced by a weak bar potential and self-gravity of the gas.
Properties of Stars in the Subaru Deep Field
Authors: Richmond Michael
Published: March 2014

We investigate the properties of objects in the Subaru Deep Field (SDF), using public catalogs constructed from images in several optical passbands. Using a small subset of objects most likely to be stars, we construct a stellar locus in three-dimensional color space. We then compare the position of all objects relative to this locus to create larger samples of stars in the SDF with rough spectral types. The number counts of stars defined in this way are consistent with those of current models of the Galaxy.
An Orbital Period Study of the W UMa-Type Binary RZ Comae Berenicis
Authors: Qian Sheng-Bang , He Jia-Jia
Published: March 2014

New photoelectric and CCD photometry observations of a short-period W UMa-type binary system, RZ Com, are presented. The light curves of Broglia (1960, Contr. Milano-Merate, 165) were symmetric in $V$ band, while the present light curve shows a typical O’Connell effect, with Maximum I brighter than Maximum II by 0.015 mag. It is found that the light curve of the binary star has changed from W-subtype to A-subtype according to Binnendijk’s classification. This variation may be caused by the activity of dark spot on the primary component. Combining four newly determined times of the light minimum with others published in the literature, the orbital period change of the system was investigated. A small-amplitude oscillation ($A = 0.0058 \,\mathrm{d}$), with a period of 44.8 yr has been discovered to be superimposed on a long-term period increase with a rate of $dP/dt = + 4.12 \times 10^{-8} \,\mathrm{d} \,\mathrm{yr}^{-1}$. The period oscillation can be explained either by the light-time effect via the presence of an unseen third body or by magnetic-activity cycles of the components. The mass ratio of RZ Com is $q = 0.43$. The secular period variation is in agreement with the conclusions of Qian (2001, MNRAS, 328, 914; 2003, MNRAS, 342, 1260). This indicates that it is on the TRO-controlled stage of the evolutionary scheme proposed by Qian.
Chandra and ROSAT Observations of NGC 5044: Profile of Dark Halos in Galaxy Groups
Authors: Betoya-Nonesa Jelly Grace , Fukazawa Yasushi , Ohsugi Takashi
Published: March 2014

We combined spatially resolved Chandra data with the ROSAT data to constrain the dark-matter distribution in the galaxy group NGC 5044. Within $250 \, h^{-1}_{50} \,\mathrm{kpc}$, the total mass is found to be $\sim 1.6 \times10^{13} \,{{{M}_{\odot}}}$, 12% of which constitutes baryonic mass. Within the inner central regions, the total mass profile exhibits a double structure, typical for groups containing a cD galaxy. Following previous studies of mostly rich galaxy clusters, we studied in detail the nature of such a double structure, whereby we inferred likely interface between the cD galaxy and the surrounding galaxies. For this interesting group, we determined for the first time the galaxy-group interface, which is around 7.5 kpc from the peak of the X-ray emission. The total mass internal to this interface radius is found to be ${\sim 7.1 \times10^{10} \,{{{M}_{\odot}}}}$. Beyond this radius, the total mass profile becomes DM-dominated and the corresponding DM profile is reasonably fitted with the NFW model, yielding results consistent with the observed scatter expected for CDM halos. A power-law fit to the DM mass profile gives $\alpha = 1.88 \pm 0.32$, a slope that is within the observed range, but is significantly larger than that of low surface brightness galaxies and self-interacting DM halos.
Low-Mass X-Ray Binary as the Progenitor of PSR J1713 + 0747
Authors: Chen Wen Cong , Li Xiang Dong , Wang Zhen Ru
Published: March 2014

We have calculated the evolution of low-mass X-ray binaries that lead to the formation of the binary radio pulsars, like PSR J1713$+$0747. We showed that the mass transfer is most likely to be nonconservative, due to unstable disk accretion, to account for the mass of PSR J1713$+$0747, which is close to its initial value. We assumed that part of the lost material from the binary may form a circumbinary disk, and found that it can significantly influence the mass-transfer processes. We briefly discuss the implications of the circumbinary disks on the evolution of low-mass X-ray binaries and the formation of low-mass binary pulsars.
Three-Dimensional Motion of Plasmas Associated with a Coronal Mass Ejection Observed with NOrikura Green-Line Imaging System (NOGIS)
Authors: Suzuki Isao , Sakurai Takashi , Ichimoto Kiyoshi
Published: March 2014

In order to investigate the structure and the driving mechanism of Coronal Mass Ejections (CMEs), it is important to examine in detail the magnetic field structure in the low corona. NOrikura Green-line Imaging System, with its unique capability of Doppler imaging, was used to study a CME and its source region on 1999 May 7. Prior to the CME, a small loop at the north-east limb moved toward a neighboring larger loop in the plane of the sky. Then, the small loop apparently destabilized the large loop, resulting in the CME with a red-shifted motion. The CME propagated non-radially in the plane of the sky. These observations indicate that two loop systems were involved in this CME, and the direction of mass ejection was determined by the magnetic field configuration around the source region and the location of the initial energy release in the magnetic field structure. A brief discussion is given on the loop oscillation phenomenon observed during this event.
Polarization of Light from Warm Clouds above an Accretion Disk: Effects of Strong Gravity near a Black Hole
Authors: Horák Jirí , Karas Vladimír
Published: March 2014

We consider polarization from the scattering of light on a cloud in radial motion along the symmetry axis of an accretion disk. Radiation drag from the disk and gravitational attraction of the central black hole are taken into account, as well as the effect of the cloud cooling in the radiation field. This provides us with a self-consistent toy-model for predicted lightcurves, including the linear polarization that arises from the scattering. Strong gravitational lensing creates indirect images; these are formed by photons that originate from the disk, become backscattered onto the photon circular orbit and eventually redirected toward an observer. Under suitable geometrical conditions the indirect photons may visibly influence the resulting magnitude of the polarization and light-curve profiles. Relevant targets are black holes in active galactic nuclei and stellar-mass Galactic black-holes exhibiting episodic accretion/ejection events.
Source Structures of the 1998 November 28 X-Class Flare and Electron Acceleration
Authors: Huang Guangli , Nakajima Hiroshi , Masuda Satoshi , Kobayashi Ken , Kubo Masahito
Published: March 2014

We studied the 1998 November 28 X-class flare, which showed long-duration, two-ribbon $\mathrm{H}\alpha$ emission. (1) A soft X-ray loop system developed along the major magnetic neutral line in the impulsive phase. Hard X-ray and microwave emissions due to nonthermal electrons were located in some limited regions. While the compact hard X-ray loop was associated with weak, diffuse soft X-ray emission, two large microwave loops did not have soft X-ray counterparts. (2) Time profiles of two large microwave loops were similar to that of hard X-ray total emission, which emanated mostly from the compact source, even in the fine time structure in the rising phase. (3) A super-hot thermal hard X-ray source appeared around the impulsive peak and was located along the major magnetic neutral line in the declining phase, coinciding with the bright soft X-ray emission. The thermal component can be explained within the standard reconnection model to the extent that the super-hot thermal plasma was heated in the large soft X-ray loop. However, the nonthermal electrons were accelerated in a localized region where three loops interacted with each other. The inferred configuration may be a more complicated form of the double-loop interaction model proposed by Hanaoka (1996) and Nishio et al. (1997).
Possibility of Ultra High-Energy Cosmic Rays from the Giant Flare in Soft Gamma Repeater 1806−20
Authors: Asano Katsuaki , Yamazaki Ryo , Sugiyama Naoshi
Published: March 2014

On 2004 December 27, a giant flare from the soft gamma repeater 1806$-$20 was observed. The radiation mechanism of the initial peak of the flare would be controversial. In this letter we point out that very high-energy cosmic rays would be produced in the case that the flare was caused by internal shocks, as is usually considered for gamma-ray bursts. The highest energy of cosmic rays can reach $10^{19} \,\mathrm{eV}$, if the Lorentz factor of the shocks is sufficiently high. Future observations of cosmic rays will inform us about the mechanism of the giant flare.
VSOP Monitoring of the Compact BL Lac Object AO 0235+164
Authors: Sándor Frey , Gurvits Leonid I. , Gabuzda Denise C. , Salter Chris J. , Altschuler Daniel R. , Perillat Phil , Aller Margo F. , Aller Hugh D. , Hirabayashi Hisashi , Davis Michael M.
Published: March 2014

In 1999, the highly compact and variable BL Lac object AO 0235$+$164 was identified as the highest brightness temperature active galactic nucleus observed with the VLBI Space Observatory Programme (VSOP), with ${T_{\mathrm{B}} \gt 5.8 \times10^{13} \,\mathrm{K}} {T_{\mathrm{B}} \gt 5.8 \times10^{13} \,\mathrm{K}}$ (Frey et al. 2000). The sub-milliarcsec radio structure of this source has been studied with dual-frequency (1.6 and 5 GHz), polarization-sensitive VSOP observations during 2001 and 2002. Here we present the results of this monitoring campaign. At the time of these observations, the source was weakly polarized and characterized by a radio core that is clearly resolved on space–ground baselines.
Milliarcsecond-Scale Structure in the Gamma-Ray Loud Quasar PKS 1622−297
Authors: Wajima Kiyoaki , Bignall Hayley E. , Kobayashi Hideyuki , Hirabayashi Hisashi , Murata Yasuhiro , Edwards Philip G. , Tsuboi Masato , Fujisawa Kenta
Published: March 2014

We made a high-resolution VLBI observation of the gamma-ray loud quasar PKS 1622$-$297 with the HALCA spacecraft and ground radio telescopes at 5 GHz in 1998 February, almost 3 yr after the source exhibited a spectacular GeV gamma-ray flare. The source shows an elongated structure toward the west on the parsec scale. The visibility data are well modeled by three distinct components: a bright core and two weaker jet components. Comparison with previous observations confirms that the jet components have an apparent superluminal motion up to $12.1 \,h^{-1} \, c$, with the inner jet components having lower superluminal speeds. We applied the inverse Compton catastrophe model and derived a Doppler factor, $\delta$, of 2.45, which is rather lower than those of other gamma-ray loud active galactic nuclei (AGNs), suggesting that the source was in a more quiescent phase at the epoch of our observation. As an alternative probe of the subparsec-scale structure, we also present the results from multiepoch ATCA total flux monitoring, which indicate the presence of persistent intraday variability consistent with refractive interstellar scintillation. We examined the gamma-ray emission mechanism in light of these observations.
The Relative Neighborhood Graph for Estimating Two-Dimensional Voids in the Cold Dark Matter Universe
Authors: Ueda Haruhiko , Takeuchi Tsutomu T.
Published: March 2014

A new technique based on a graph-theoretical approach is proposed for identifying and estimating voids in two-dimensional galaxy distributions. A relative neighborhood graph is utilized for identifying two-dimensional voids. The loop angle that characterizes the size of the voids is defined, and the distribution function as well as the average of loop angles are used for estimating the voids statistically. We applied our new technique to two-dimensional voids in Cold Dark Matter (CDM) simulations. Low-density, middle-density, and high-density CDM models were adopted for examining the nature of two-dimensional voids. From our analyses, we found that the average of the loop angle in the low-density CDM model is apparently larger than that in the middle-density or the high-density CDM models. However, the difference between the middle-density and the high-density CDM models is subtle. We also analyzed the observational two-dimensional galaxy distributions and compared the two-dimensional mock samples that are constructed from CDM simulations. From our analyses, we succeeded to restrict the density parameter of our universe.
The 2005 July Superoutburst of the Dwarf Nova 2QZ J021927.9−304545: the SU UMa Nature Confirmed
Authors: Imada Akira , Kato Taichi , Monard L. A. G. , Retter Alon , Liu Alex , Nogami Daisaku
Published: March 2014

We report on the time-resolved photometry of the 2005 July superoutburst of a dwarf nova, 2QZ J021927.9$-$304545. The resultant light curves showed conspicuous superhumps with a period of 0.081113(19) days, confirming the SU UMa nature of the object. Although we missed the maximum phase of the outburst, the amplitude of the superoutburst well exceeded 5 mag. This value is slightly larger than that of typical SU UMa-type dwarf novae. The superhump period decreased as the time elapsed, as can be seen in most SU UMa-type dwarf novae. Based on the archive of ASAS-3, the recurrence time of a superoutburst of the variable turned out to be about 400 days. This value is typical of well-known SU UMa stars. The distance to this system was roughly estimated as $370\,(+20,-60) \,\mathrm{pc}$ using an empirical relation.