bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
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

Abstract
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

Abstract
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

Abstract
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 $3 &lt; z &lt; 5$. 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.
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

Abstract
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

Abstract
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 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

Abstract
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.
Discovery of a Promising Candidate of WZ Sge-Type Dwarf Novae, ASAS 160048−4846.2: Evidence for Double-Peaked Humps
Authors: Imada Akira , Monard L. A. G. Berto 
Published: March 2014

Abstract
We report on time-resolved CCD photometry during the 2005 June outburst of a dwarf nova, ASAS 160048$-$4846.2. The observed light curves unambiguously showed embryonic humps with a period of 0.063381(41) days, after which genuine superhumps emerged with a period of 0.064927(3) days. Based on evidence for double-peaked humps in the earlier stage of the outburst, this object might be qualified as the seventh member of WZ Sge-type dwarf novae after Var Her 04. If the former period is the same as, or very close to the orbital period of the system, as in other WZ Sge systems, the fractional superhump excess is about 2.4%. This value is unexpectedly larger than that of other WZ Sge-type dwarf novae. The early phase of our observing run provided evidence for the transition from chaotic humps to genuine superhumps, together with increasing the amplitude.
Soft X-Ray Transmission Spectroscopy of a Warm/Hot Intergalactic Medium with XEUS
Authors: Kawahara Hajime , Yoshikawa Kohji , Sasaki Shin , Suto Yasushi , Kawai Nobuyuki , Mitsuda Kazuhisa , Ohashi Takaya , Yamasaki Noriko Y. 
Published: March 2014

Abstract
We discuss the detectability of a Warm/Hot Intergalactic Medium (WHIM) via absorption lines toward bright point sources with a future X-ray satellite mission, XEUS. While we consider bright QSOs as specific examples, the methodology can be applied to bright gamma-ray burst afterglows. We created mock absorption spectra for bright QSOs (more than 20 QSOs over all sky) using the light-cone output of a cosmological hydrodynamic simulation. We assumed that the WHIM is under collisional and photo-ionization equilibrium. If WHIM has a constant metallicity of $Z = 0.1 \,Z_{ {\odot }}$, approximately 2 O VII absorption line systems with $ \gt 3 \,\sigma \gt 3 \,\sigma$ will be detected on average along a random line-of-sight toward bright QSOs up to $z=0.3$ for a 30 ks exposure.