bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chandra Observations of a Young Embedded Magnetic B Star in the $\rho$ Ophiuchus Cloud
Authors: Hamaguchi Kenji , Corcoran Michael F. , Imanishi Kensuke 
Published: March 2014

Abstract
This paper reports on an analysis of two Chandra X-ray observations of the young magnetic B star $\rho$ Ophiuchus S1. X-ray emission from the star was detected in both observations. The average flux was almost the same in both, but during each observation the flux showed significant time variations by a factor of two on time-scales of 20–40 ks. Each spectrum could be fit by either an absorbed power-law model with a photon index of $\sim 3$ or a thin-thermal plasma model with a temperature of $\sim 2 \,\mathrm{keV}$ and an extremely low metal abundance ($\lesssim 0.1$ solar). The spectrum of the first observation has a weak-line feature at about 6.8 keV, which might correspond to highly ionized iron $\mathrm{K}\alpha$. In contrast, the spectrum of the second observation apparently shows a weak edge absorption component at $E \sim4 \,\mathrm{keV}$. The continuum emission and $\log (L_\mathrm{X} / L_{\mathrm{bol}}) \sim-6$ are similar to those of young intermediate-mass stars (Herbig Ae/Be stars), although the presence of a strong magnetic field (inferred from the detection of non-thermal radio emission) has drawn an analogy between $\rho$ Ophiuchus S1 and magnetic chemically peculiar (MCP) stars. If the X-ray emission is thermal, the small abundances that we derived might be related to the inverse first-ionization potential (FIP) effect, though there is no significant trend as a function of FIP from our model fits. If the emission is non-thermal, it might be produced by high-energy electrons in the magnetosphere.
Evolution of Elliptical Galaxies at $z \gtrsim 1$ Revealed from a Large, Multicolor Sample of Extremely Red Objects
Authors: Miyazaki Masayuki , Shimasaku Kazuhiro , Kodama Tadayuki , Okamura Sadanori , Furusawa Hisanori , Ouchi Masami , Nakata Fumiaki , Doi Mamoru , Hamabe Masaru , Kimura Masahiko , Komiyama Yutaka , Miyazaki Satoshi , Nagashima Chie , Nagata Tetsuya , Nagayama Takahiro , Nakajima Yasushi , Nakaya Hidehiko , Pickles Andrew J. , Sato Shuji , Sekiguchi Kazuhiro , Sekiguchi Maki , Sugitani Koji , Takata Tadafumi , Tamura Motohide , Yagi Masafumi , Yasuda Naoki 
Published: March 2014

Abstract
We studied the evolution of elliptical galaxies at $z \gtrsim 1$ using a sample of 247 Extremely Red Objects (EROs) with $R-K_\mathrm{s} \ge 3.35$ (AB) and $K_\mathrm{s} \le 22.1$ (AB) constructed from $BVR \, i'z'JHK_\mathrm{s}$ multicolor data of a $114 \,\mathrm{arcmin}^2$ area in the Subaru/XMM-Newton Deep Field taken with the Subaru Telescope and the UH 2.2 m telescope. By fitting template spectra of old galaxies (OGs) and young, dusty starbursts (DSs) to the multicolor data, we classified EROs into these two classes and estimated their redshifts. We found that 58% of the EROs in our sample belong to the OG class and that these OGs have a wide range of colors at any redshift. We derived rest-frame $B$-band luminosity functions of OGs in our sample at $z=1 \hbox{-} 1.5$ and $1.5 \hbox{-} 2.5$, and found that the number density of galaxies obeying passive evolution drops at $z \gtrsim 1.5$ by a factor of three or more. The spatial correlation length of OGs is estimated to be $r_0 \gtrsim 8 \,h^{-1} \,\mathrm{Mpc}$, which is comparable to, or larger than, those of present-day early-type galaxies of similar luminosities. We also discussed properties of DSs in our data.
SDSS J1335+0118: A New Two-Image Gravitational Lens
Authors: Oguri Masamune , Inada Naohisa , Castander Francisco J. , Gregg Michael D. , Becker Robert H. , Ichikawa Shin-ichi , Pindor Bartosz , Brinkmann Jonathan , Eisenstein Daniel J. , Frieman Joshua A. , Hall Patrick B. , Johnston David E. , Richards Gordon T. , Schechter Paul L. , Schneider Donald P. , Szalay Alexander S. 
Published: March 2014

Abstract
We report on the discovery of the two-image gravitationally lensed quasar SDSS J1335$+$0118. The object was selected as a lens candidate from the Sloan Digital Sky Survey. The imaging and spectroscopic follow-up observations confirm that the system exhibits two gravitationally lensed images of a quasar at $z=1.57$. The image separation is ${1\rlap {.}{}^{\mathrm {\prime \prime }}56}$. We also detect an extended component between the two quasar images, likely to be a lensing galaxy. Preliminary mass modeling predicts a differential time delay, $\Delta t$ of $\sim30 \, h^{-1} \mathrm{day}$, assuming the redshift of the lens galaxy to be $0.5$.
The Anisotropic Transfer of Resonance Photons in Hot Plasmas on Magnetized White Dwarfs
Authors: Terada Yukikatsu , Ishida Manabu , Makishima Kazuo 
Published: March 2014

Abstract
In order to confirm the anisotropic effect of resonance photons in hot accretion columns on white dwarfs in magnetic cataclysmic variables, proposed by Terada et al. (2001), systematic studies with ASCA of 7 polars and 12 intermediate polars were performed. The equivalent widths of He-like Fe $\mathrm{K}\alpha$ lines of polars were found to be systematically modulated at their spin periods in such a way that it increases at the pole-on phase. This implies that the anisotropic mechanism is commonly operating among polars. On the other hand, those of intermediate polars are statistically consistent with being unmodulated with an upper limit of 1.5-times modulation. This may be due to a different accretion manner, like an aurora curtain (Rosen et al. 1988), so that the plasma also becomes optically thin along the horizontal axis for the resonance lines, or because of larger optical depths for Compton scattering if the emission regions have the same coin-like shapes as polars.
The Evolution of Galaxies in and around Clusters at High-Redshift
Authors: Fujita Yutaka , Goto Tomotsugu 
Published: March 2014

Abstract
In this paper, we focus on ram-pressure stripping and evaporation of disk galaxies in and around a cluster. We show that the evolution of the disk surface density affects the efficiency of ram-pressure stripping of galaxies at $z\gtrsim 1$. We also consider the saturation of thermal conduction in detail and show that it cannot be ignored at larger radii of a cluster, which makes the time-scale of the evaporation larger. Both the ram-pressure stripping and evaporation could affect the evolution of galaxies even around a cluster. In particular, the observed gradual decline of the star-formation rates of galaxies in and around clusters could be explained by evaporation without resorting to speculative strangulation (stripping of warm gas in galactic halos).
The Peculiar 2004 Superoutburst in the Helium Dwarf Nova, 2003aw
Authors: Daisaku Nogami , Monard Berto , Retter Alon , Liu Alex , Uemura Makoto , Ishioka Ryoko , Imada Akira , Kato Taichi 
Published: March 2014

Abstract
We conducted a time-resolved photometric campaign of helium dwarf nova, 2003aw, in 2004 May–June. 2003aw stayed at 14.7–15.7 mag for the first several days during this campaign, which is the plateau phase of this superoutburst. This variable then rapidly decayed to $\sim 18.0 \,\mathrm{mag}$, still brighter by about 2 mag than its quiescence magnitude, and maintained this brightness for about 20 days, having short flares of $\sim 2 \,\mathrm{mag}$. A long fading tail followed it. We detected superhumps with a period of 0.02357(4)d [= 2036(3)s] during the plateau phase. The whole light curve of the superoutburst in 2003aw, taking into account the present data and those in the literature, perfectly resembles that of the 1996–1997 superoutburst of the peculiar WZ Sge-type hydrogen-rich dwarf nova, EG Cnc.
Search for CCH—, NCO—, and NCS— Negative Ions in Molecular Clouds
Authors: Morisawa Yusuke , Hoshina Hiromichi , Kato Yoshiyasu , Simizu Zenzo , Kuma Susumu , Sogoshi Norihito , Fushitani Mizuho , Watanabe Shiori , Miyamoto Yuki , Momose Takamasa , Kasai Yasuko , Kawaguchi Kentarou 
Published: March 2014

Abstract
Despite several suggestions concerning the existence of negatively charged molecules and negative atomic ions in molecular clouds, few attempts have been made to search for negative ions in molecular clouds. In the present study, we extensively searched for three negative molecular ions ($\mathrm{CCH}^{-}, \mathrm{NCO}^{-}$, and $\mathrm{NCS}^{-}$) in a dark cloud, L134N, using the Nobeyama 45-m radio telescope. The three negative ions are molecules whose rotational constants have been reported based on laboratory experiments. After a long accumulation, a trace amount of an unidentified emission line was detected at a frequency close to the theoretical prediction of the $J = 1 \hbox{--} 0$ transition of $\mathrm{CCH}^{-}$. If this unidentified line is attributable to $\mathrm{CCH}^{-}$, the observed emission intensity would provide an estimation of the column density of $\mathrm{CCH}^{-}$ in L134N to be $1.0 \times 10^{11} \,\mathrm{cm}^{-2}$, which corresponds to a fractional abundance of $5 \times 10^{-12}$ relative to hydrogen. However, our recent observation using the IRAM 30-m telescope did not reproduce the $J = 1 \hbox{--} 0$ signal, nor detect any trace of the $J = 2 \hbox{--} 1$ transition. Thus, the identification of $\mathrm{CCH}^{-}$ in L134N is not yet confirmed. As for other ions, signals of neither $\mathrm{NCO}^{-}$ nor $\mathrm{NCS}^{-}$ were detected in L134N. Although we also searched for the three negative ions in a translucent cloud, CB228, and a star-forming region, SgrB2, no signals were detected. The upper limit abundances of the ions in these clouds are discussed.
Geometrical Effect of Supercritical Accretion Flows: Observational Implications of Galactic Black-Hole Candidates and Ultraluminous X-Ray Sources
Authors: Watarai Ken-ya , Ohsuga Ken , Takahashi Rohta , Fukue Jun 
Published: March 2014

Abstract
We consider the dependence of the viewing angle in supercritical accretion flows and discuss the observational implications of galactic black-hole candidates and ultraluminous X-ray sources. Model spectra of supercritical accretion flows strongly depend on the inclination angle. For example, the maximum temperature of the supercritical disk (the accretion rate and the black-hole mass are $\dot{M} = 1000 \,L_{\mathrm{E}}/c^2$ and $M = 10 \,{{{M}_{\odot}}}$, respectively) is $kT_{\mathrm{in}} \sim 2.0 \,\mathrm{keV}$ for a low-inclination angle, $i \lesssim 40^\circ$, while $k T_{\mathrm{in}} \sim 0.6 \,\mathrm{keV}$ for a high-inclination angle, $i \gtrsim 60^\circ$. This spectral softening originates from self-occultation of the disk, i.e., the outer disk blocks emission from the disk inner region, even if we take into account the effect of general relativity (light bending, Doppler boosting). This is because, when the mass accretion rate exceeds the critical rate, then the shape of the disk is geometrically thick due to enhanced radiation pressure. We also find that the spectral properties of low-$i$ and low accretion-rate disks are very similar to those of high-$i$ and high accretion-rate disks. That is, if an object has a high $i$ and a high accretion rate, such a system suffers from self-occultation and the spectrum will be extremely soft. Therefore, we cannot distinguish these disks by only the difference in their spectrum shapes. Conversely, if we use the self-occultation properties, we could constrain the inclination angle of the system. We suggest that some observed high-temperature ultraluminous X-ray sources have low-inclination angles, i.e., near face-on geometry, $i \lesssim 40^{\circ}$, and the Galactic black-hole candidate XTE J1550$-$564 possesses relatively high-inclination angles, $i \gtrsim 60^{\circ}$.
Extremely High-Velocity Gas in the Galaxy Arp 220, Revealed with Ammonia Absorption Lines
Authors: Takano Shuro , Nakanishi Kouichiro , Nakai Naomasa , Takano Toshiaki 
Published: March 2014

Abstract
We observed ammonia $(J, K) = (1, 1), (2, 2), (3, 3)$, and $(4, 4)$ transitions at a wavelength of 1.3 cm toward a prototypical ultraluminous infrared galaxy, Arp 220, with the Nobeyama 45-m radio telescope. We detected extremely wide absorption lines at the $(1, 1)$ and $(3, 3)$ transitions. The maximum total velocity width was $\sim 1800 \,\mathrm{km} \,\mathrm{s}^{-1}$. Such wide molecular absorption lines were detected for the first time in galaxies. The absorption lines are formed by ammonia only in front of the central compact continuum emission ($\sim {1{}^{\mathrm {\prime \prime }}} = 370 \,\mathrm{pc}$). The present results clearly indicate the existence of extremely high-velocity motion in the central compact region of Arp 220. A possible origin of such motion is rapidly rotating gas, suggesting the existence of an active galactic nucleus, or outflowing or inflowing gas.
Three-Dimensional Magnetohydrodynamic Simulation of Nonlinear Magnetic Buoyancy Instability of Flux Sheets with Magnetic Shear
Authors: Nozawa Satoshi 
Published: March 2014

Abstract
A series of three-dimensional magnetohydrodynamic simulations is used to study the nonlinear evolution of the magnetic buoyancy instability of a magnetic flux sheet with magnetic shear. A horizontal flux sheet that is initially placed below the solar photosphere is susceptible to both the interchange instability and the Parker instability (the undular mode of the magnetic buoyancy instability). The growth rate in the linear stage of the instability in the numerical simulation is consistent with that predicted by linear theory. In the nonlinear stage, the development depends on the initial perturbation as well as the initial magnetic field configuration (i.e., the presence of magnetic shear). When an initial perturbation is assumed to be periodic, the emerging flux rises to the corona and the magnetic field expands like a potential field, as observed in 2D simulations. When an initial non-periodic perturbation or random perturbations are assumed, the magnetic flux expands horizontally when the magnetic field emerges a little into the photosphere. The distribution of the magnetic field and gas tends to be in a new state of magnetohydrostatic equilibrium. When magnetic shear is present in the initial magnetic flux sheets, the interchange mode is stabilized so that the emerging loop is higher than in the no magnetic shear case. We discuss how the presented results are related to the emerging flux observed on the Sun.
Chandra Observations of A 2670 and A 2107: A Comet Galaxy and cDs with Large Peculiar Velocities
Authors: Fujita Yutaka , Sarazin Craig L. , Sivakoff Gregory R. 
Published: March 2014

Abstract
We present an analysis of Chandra observations of the galaxy clusters A 2670 and A 2107. Their cD galaxies have large peculiar velocities ($\gt200 \,\mathrm{km} \,\mathrm{s}^{-1} \gt200 \,\mathrm{km} \,\mathrm{s}^{-1}$) and thus the clusters appear to be undergoing mergers. In A 2670, we find a comet-like structure around one of the brightest galaxies. At the leading edge of the structure, there is a cold front. The mass of the X-ray gas in the comet-like structure suggests that the galaxy was in a small cluster or group, and its intracluster medium is being stripped by ram-pressure. The regions of cool interstellar medium of the cD galaxies in A 2670 and A 2107 are very compact. This is similar to the brightest galaxies in the Coma cluster, which is also a merging cluster. In each galaxy, the short cooling time of the ISM requires a heating source; the compact nature of the ISM makes it unlikely that the heating source is a central active galactic nucleus.
Dual-Frequency VSOP Imaging of the Jet in S5 0836+710
Authors: Lobanov Andrei P. , Krichbaum Thomas P. , Witzel Arno , Zensus J. Anton 
Published: March 2014

Abstract
The luminous high-redshift ($z=2.17$) quasar S5 0836$+$710 was observed in 1997 October with the VSOP at 1.6 GHz and 5 GHz. We report here a previously unpublished image made from the data at 1.6 GHz, and compare the structure of a relativistic jet in this quasar at two frequencies. We present a spectral index image tracing the spectral properties of the jet up to $\sim 40$ milliarcsec distance from the nucleus. The curved jet ridge line observed in the images and the spectral index distribution can be described by a Kelvin–Helmholtz instability developing in a relativistic outflow with a Mach number of $\sim 6$. In this description, the overall ridge line of the jet is formed by the helical surface mode of the Kelvin–Helmholtz instability, while areas of flatter spectral index embedded into the flow correspond to pressure enhancements produced by the elliptical surface mode of the instability. An alternative explanation involving a sequence of slowly dissipating shocks cannot be ruled out at this point.
MOIRCS Deep Survey. I: DRG Number Counts
Authors: Kajisawa Masaru , Konishi Masahiro , Suzuki Ryuji , Tokoku Chihiro , Uchimoto Katsuno Yuka , Yoshikawa Tomohiro , Akiyama Masayuki , Ichikawa Takashi , Ouchi Masami , Omata Koji , Tanaka Ichi , Nishimura Tetsuo , Yamada Toru 
Published: March 2014

Abstract
We used very deep near-infrared imaging data taken with the Multi-Object InfraRed Camera and Spectrograph (MOIRCS) on the Subaru Telescope to investigate the number counts of Distant Red Galaxies (DRGs). We observed a $4' \times 7'$ field in the Great Observatories Origins Deep Survey-North (GOODS-N), and our data reached $J=24.6$ and $K=23.2$ ($5\,\sigma$, Vega magnitude). The surface density of DRGs selected by $J-K \gt 2.3 J-K \gt 2.3$ is $2.35 \pm 0.31 \,\mathrm{arcmin}^{-2}$ at $K &lt; 22$ and $3.54 \pm 0.38 \,\mathrm{arcmin}^{-2}$ at $K &lt; 23$, respectively. These values are consistent with those in the GOODS-South and FIRES. Our deep and wide data suggest that the number counts of DRGs turn over at $K \sim 22$, and the surface density of the faint DRGs with $K \gt 22$ is smaller than that expected from the number counts at the brighter magnitude. The result indicates that while there are many bright galaxies at $2 &lt; z &lt; 4$ with the relatively old stellar population and/or heavy dust extinction, the number of faint galaxies with a similar red color is relatively small. Different behavior patterns of the number counts of the DRGs and bluer galaxies with $2 &lt; z_{\mathrm{phot}} &lt; 4$ at $K \gt 22$ suggest that the mass-dependent color distribution, where most of the low-mass galaxies are blue, while more massive galaxies tend to have redder colors, had already been established at that epoch.
Steady Models of Optically Thin, Magnetically Supported Black Hole Accretion Disks
Authors: Oda Hiroshi , Machida Mami , Nakamura Kenji E. , Matsumoto Ryoji 
Published: March 2014

Abstract
We obtained steady solutions of optically thin, single-temperature, magnetized black hole accretion disks, assuming thermal bremsstrahlung cooling. Based on the results of 3D MHD simulations of accretion disks, we assumed that the magnetic fields inside the disk are turbulent and dominated by an azimuthal component. We decomposed the magnetic fields into an azimuthally averaged mean field and fluctuating fields. We also assumed that the azimuthally averaged Maxwell stress is proportional to the total pressure. The radial advection rate of the azimuthal magnetic flux, $\dot \Phi$, is prescribed as being proportional to $\varpi^{-\zeta}$, where $\varpi$ is the radial coordinate and $\zeta$ is a parameter that parameterizes the radial variation of $\dot \Phi$. We found that when the accretion rate, $\dot M$, exceeds the threshold for the onset of the thermal instability, a magnetic pressure-dominated new branch appears. Thus, the thermal-equilibrium curve of an optically thin disk has a ‘Z’-shape in the plane of the surface density and temperature. This indicates that as the mass accretion rate increases, a gas pressure-dominated optically thin hot accretion disk undergoes a transition to a magnetic pressure dominated, optically thin cool disk. This disk corresponds to the X-ray hard, luminous disk in black hole candidates observed during the transition from a low/hard state to a high/soft state. We also obtained global steady transonic solutions containing such a transition layer.
A Multiband Study of the Optically Dark GRB 051028
Authors: Urata Yuji , Huang Kui-Yun , Kuo Ping-Hung , Ip Wing-Huen , Qiu Yulei , Masuno Keisuke , Tashiro Makoto , Abe Keiichi , Onda Kaori , Kodaka Natsuki , Kuwahara Makoto , Tamagawa Toru , Usui Fumihiko , Ioka Kunihito , Lee Yi-Hsi , Wei Jianyan , Deng Jinsong , Zheng Weikang , Makishima Kazuo 
Published: March 2014

Abstract
Observations were made of the optical afterglow of GRB 051028 with the Lulin observatory 1.0m telescope and the Wide-Field Telescope for GRB Early Timing (WIDGET) robotic telescope system. $R$-band photometric data were obtained on 2005 October 28 (UT), or 0.095–0.180 d after the burst. There is a possible plateau in the optical light curve around 0.1 d after the burst; the afterglow of GRB 051028 resembles optically bright afterglows (e.g., GRB 041006, GRB 050319, GRB 060605) in shape of the light curve, but not in brightness. The brightness of the GRB 051028 afterglow is 3 mag fainter than that of one of the dark events, GRB 020124. Optically dark GRBs have been attributed to dust extinction within the host galaxy or a high redshift. However, a spectrum analysis of the X-rays implies that there is no significant absorption by the host galaxy. Furthermore, according to a theoretical calculation of the Ly$\alpha$ absorption to find the limit of the GRB 051028’s redshift, the expected $R$-band absorption is not high enough to explain the darkness of the afterglow. The present results disfavor either the high-redshift hypothesis or the high-extinction scenario for optically dark bursts; rather, they are consistent with the possibility that the brightness of the optical afterglow is intrinsically dark.
A Possible Estimate of the Doppler Factors for Blazars
Authors: Xiang Yang , Dai Ben-Zhong 
Published: March 2014

Abstract
We have studied the beaming effect and multi-band properties of blazars using a sample of 31 blazars. In the sample, the observed variability timescale, the mass of the central super-massive black hole (SMBH), and the flux densities at 4 energy bands (radio, optical, X-ray, and $\gamma$-ray) of each object were compiled from the literature. The Doppler factor was estimated in two cases: (1) considering that the Doppler factor is the same throughout the entire energy band, and calculating by using the observed variability timescale; (2) the Doppler factor is a function of frequency, i.e., the Doppler factor is variable in a different energy band. Based on the Doppler factor estimated in both cases, we find that the intrinsic flux densities at different energy bands are significantly correlated with each other.
BRIDGE: A Direct-Tree Hybrid $N$-Body Algorithm for Fully Self-Consistent Simulations of Star Clusters and Their Parent Galaxies
Authors: Fujii Michiko , Iwasawa Masaki , Funato Yoko , Makino Junichiro 
Published: March 2014

Abstract
We developed a new direct-tree hybrid $N$-body algorithm for fully self-consistent $N$-body simulations of star clusters in their parent galaxies. In such simulations, star clusters need high accuracy, while galaxies need a fast scheme because of the large number of particles required to model it. In our new algorithm, the internal motion of the star cluster is calculated accurately using the direct Hermite scheme with individual timesteps, and all other motions are calculated using the tree code with a second-order leapfrog integrator. The direct and tree schemes are combined using an extension of the mixed variable symplectic (MVS) scheme. Thus, the Hamiltonian corresponding to everything other than the internal motion of the star cluster is integrated with the leapfrog, which is symplectic. Using this algorithm, we performed fully self-consistent $N$-body simulations of star clusters in their parent galaxy. The internal and orbital evolutions of the star cluster agreed well with those obtained using the direct scheme. We also performed fully self-consistent $N$-body simulation for large-$N$ models ($N=$ 2$\times$10$^6$). In this case, the calculation speed was seven-times faster than what would be if the direct scheme was used.