bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observations of Prominence Eruptions with Two Radioheliographs, SSRT, and NoRH
Authors: Grechnev Victor V. , Uralov Arkadiy M. , Zandanov Vasily G. , Baranov Nikolai Y. , Shibasaki Kiyoto 
Published: March 2014

Abstract
We address simultaneous observations of eruptive prominences with two radioheliographs, SSRT at 5.7 GHz and NoRH at 17 and 34 GHz. Three events are presented: 1997 September 27, 2000 September 4, and 2001 January 14. We analyze them using images observed in microwaves, $\mathrm{H}\alpha$, images from Extreme ultraviolet Imaging Telescope on board Solar and Heliospheric Observatory (SOHO), and white-light images from Large Angle and Spectrometric Coronagraph (SOHO/LASCO). We address three stages of the eruptive process: 1) pre-eruptive ascent, 2) rapid acceleration, 3) free expansion, and the overall kinematics of the ejecta. We estimate the densities and kinetic temperatures of prominences, and also the velocities and accelerations of ejecta. The main body of a prominence is surrounded by low-density cool extensions mixed with the coronal plasma, but the transition from the cool prominence to the hot plasma is sharp. From microwave and LASCO observations with overlapping fields of view we identify a radio prominence and a core of a coronal mass ejection (CME). Their temperature remains at about 5000 K, while the brightenings observed in extreme ultraviolet are probably due to only skin-heating. We discuss the observations in terms of our Dual-Filament CME initiation model.
The Expanding Radio Lobe of 3C 84 Revealed by VSOP Observations
Authors: Asada Keiichi , Kameno Seiji , Shen Zhi-Qiang , Horiuchi Shinji , Gabuzda Denise C. , Inoue Makoto 
Published: March 2014

Abstract
The expansion and inner proper motions of a young radio lobe associated with the bright radio source 3C 84 in the Seyfert galaxy NGC 1275 have been detected by VSOP observations. These proper motions are consistent with the evolution scenario of classical double radio sources. The apparent expansion velocity is $(0.50 \pm 0.09) \:c$. The age of the radio lobe is estimated to be $(45.7 \pm 8.9) \:\mathrm{yr}$ in 2001, which is in agreement with the age previously estimated by Romney et al. (1982). The total flux density at 5 GHz increased at the end of the 1950’s, marked several peaks in the middle of the 1980’s, and is presently in a decay phase. The decay of the total flux density can naturally be explained by an adiabatic cooling due to expansion of the radio lobe, and previously measured spectral indices suggest that the emission comes from the surface of the radio lobe.
Lyα Emitters at z = 5.7 in the Subaru Deep Field
Authors: Shimasaku Kazuhiro , Kashikawa Nobunari , Doi Mamoru , Ly Chun , Malkan Matthew A. , Matsuda Yuichi , Ouchi Masami , Hayashino Tomoki , Iye Masanori , Motohara Kentaro , Murayama Takashi , Nagao Tohru , Ohta Kouji , Okamura Sadanori , Sasaki Toshiyuki , Shioya Yasuhiro , Taniguchi Yoshiaki 
Published: March 2014

Abstract
We present the properties of Ly$\alpha$ emitters (LAEs) at $z=5.7$ in the Subaru Deep Field. A photometric sample of 89 LAE candidates was constructed from narrow-band data down to $\mathit{NB816} = 26.0$ (AB) in a continuous $725 \,\mathrm{arcmin}^2$ area. Spectra of 39 objects satisfying the photometric selection criteria for LAEs were obtained with Subaru and Keck II Telescopes, among which 28 were confirmed LAEs, one was a nearby galaxy, and eight were unclassified. We also obtained spectra of another 24 NB816-excess objects in the field, identifying six additional LAEs. We find that the Ly$\alpha$ luminosity function derived from the photometric sample is reproduced well by a Schechter function with $L^\star = 7.9^{+3.0}_{-2.2} \times 10^{42} \,\mathrm{erg} \,\mathrm{s}^{-1}$ and $\phi^\star = 6.3^{+3.0}_{-2.0} \times 10^{-4} \,\mathrm{Mpc}^{-3}$ for $\alpha =-1.5$ (fixed) over the whole luminosity range of $L \simeq 3 \times 10^{42} \hbox{--} 3 \times 10^{43} \,\mathrm{erg} \,\mathrm{s}^{-1}$. We then measured the rest-frame Ly$\alpha$ equivalent widths for the confirmed LAEs, to find that the median among the 28 objects satisfying the photometric selection criteria is $W_{0}^{\mathrm{i}} = 233 \,{Å}$. We infer that 30%-40% of LAEs at $z=5.7$ exceed $W_{0}^{\mathrm{i}} = 240 \,{Å}$. These large-EW objects probably cannot be accounted for by ordinary star-forming populations with a Salpeter IMF. We also find that LAEs with fainter far-UV luminosities have larger EWs. Finally, we derived the far-UV luminosity function of LAEs down to $M_{\mathrm{UV}} \simeq-19.6$ using the photometric sample, and compared it with that of Lyman-break galaxies (LBGs). We find that as high as about 80% of LBGs at $z \sim 6$ have $W_{0}^{\mathrm{i}} \ge 100 \,{Å}$, in sharp contrast to lower-$z$ counterparts.
On the Spectroscopic Determination of Atmospheric Parameters and O/Fe Abundances of RR Lyrae Stars
Authors: Takeda Yoichi , Honda Satoshi , Aoki Wako , Takada-Hidai Masahide , Zhao Gang , Chen Yu-Qin , Shi Jian-Rong 
Published: March 2014

Abstract
In order to study how the conventional spectroscopic method based on the equivalent widths of the Fe I and Fe II lines effectively applies to determining the atmospheric parameters ($T_{\mathrm{eff}}, \log g, v_{\mathrm{t}}, [\mathrm{Fe/H}]$) of RR Lyrae variables and how accurately the abundances can be established from such constructed model atmospheres, we analyzed 15 high-dispersion spectrograms of RR Lyr, DX Del, DH Peg, and VY Ser taken at several different phases by using the HDS spectrograph of the Subaru Telescope, and examined the consistency of the resulting phase-to-phase abundances. Taking oxygen as the target element along with Fe, we determined its non-LTE abundance from the O I 6155–8 and 7771–5 triplets. It was found that consistent abundances were obtained for O as well as Fe to a level of $\sim 0.1 \,\mathrm{dex}$, irrespective of the pulsation phase, except for the special near-maximum high-temperature phase. This suggests that classical model atmospheres are reliably applicable to abundance determinations of RR Lyrae stars in most cases. While the oxygen abundances derived from O I 7771–5 well correlate with those from O I 6155–8, the former tends to be systematically larger by 0.1–0.2 dex than the latter, which may be interpreted as being due to the depth-dependence of the microturbulence increasing with height; i.e., the $v_{\mathrm{t}}$ value derived from deep-forming Fe lines of weak/medium-strength may not be simply applied to higher forming strong lines, such as O I 7771–5.
Core Structure of Intracluster Gas: Effects of Radiative Cooling on Core Sizes
Authors: Akahori Takuya , Masai Kuniaki 
Published: March 2014

Abstract
We investigated the core structure of radiatively cooling intracluster gas using a hydrodynamics code. We calculated the evolution of model clusters of the initial core radii, 160–300 Kpc, until the initial central cooling time, and analyzed the resultant clusters using double $\beta$-model, as was done by observational studies. It was found that the thus-obtained core-size distribution shows two peaks at $\sim 30 \hbox{--} 100 \,\mathrm{kpc}$ and $\sim 100 \hbox{--} 300 \,\mathrm{kpc}$, and can marginally reproduce the observed distribution, which exhibits two distinct peaks at around $\sim 50 \,\mathrm{kpc}$ and $\sim 200 \,\mathrm{kpc}$. This result may suggest a radiative-cooling origin for small cores, while cooling is still insignificant in clusters of large cores. It should be noted that the small core peak is reproduced by clusters that are still keeping quasi-hydrostatic balance before the initial central cooling time has elapsed.
SiO Maser Survey of the Inner Bar of the Galactic Bulge
Authors: Fujii Takahiro , Deguchi Shuji , Ita Yoshifusa , Izumiura Hideyuki , Kameya Osamu , Miyazaki Atsushi , Nakada Yoshikazu 
Published: March 2014

Abstract
We surveyed 291 MSX/2 MASS infrared objects in the $7^{\circ} \!\times 2^{\circ}$ area of the galactic center in the 43 GHz SiO $J = 1 \hbox{--} 0 v=1$ and 2 maser lines, obtaining accurate radial velocities of 163 detected objects. The surveyed area is the region where the IRAS catalog is incomplete due to contamination by high source density. The objects in the present MSX/2 MASS sample were chosen to have similar infrared characteristics to those of the previous SiO-maser-survey samples based on the color-selected IRAS sources. The sampling based on the 2 MASS catalog causes a bias to the foreside objects of the bulge due to heavy obscuration by interstellar dust; the detections considerably leaned on the $V_{\mathrm{lsr}}&lt;0$ side. The $l \hbox{--} V$ diagram reveals two conspicuous features, which were not present or tenuous in the previous studies: one feature indicating a linear velocity increase with longitude with $\vert l\vert &lt; {1\rlap {.}{}^{\mathrm {\circ }}5}$, which is likely to be associated with the inner bar, and the other feature having considerably eccentric velocities, more than those of the normal $x_1$-orbit family feature. The extinction-corrected $K$ magnitudes (if used as a distance modulus) tend to show a sequential deposition of these objects along the line of sight toward the galactic center, depending on their radial velocities. The tendency that appeared in the distance measures is consistent with the bulge–bar dynamical model utilizing the periodic orbit families in the bar potential.
Soft X-Ray Absorption Due to the Photo-Ionized Plasma in the Low-Mass X-Ray Binary EXO 0748−676 Observed with XMM-Newton Observatory
Authors: Asai Kazumi , Dotani Tadayasu 
Published: March 2014

Abstract
We analyzed an effect of the photo-ionization on the continuum spectra using the XMM-Newton archive data of the low-mass X-ray binary EXO 0748$-$676. We found that the ionization degree of the circumstellar plasma, which modifies the soft X-ray spectrum through absorption, changes largely in association with the X-ray bursts and the dips. The burst light curve below $\sim 1 \,\mathrm{keV}$ is found to have a major contribution from the persistent emission, which temporary increased during the burst due to a reduction of the opacity of the absorber. We utilized a correlation diagram of the count rates (0.5–1.0 keV vs. 2.0–4.0 keV) to study the effect of photo-ionization during the dips. We found that the correlation can be much better reproduced if we take into account the photo-ionization of the absorber. No partial covering absorption was required, except for the residual flux in the deepest dips.
Non-Equilibrium Ionization State of a Warm-Hot Intergalactic Medium
Authors: Yoshikawa Kohji , Sasaki Shin 
Published: March 2014

Abstract
The time evolution of the ionization state of metals in cosmic baryons is considered in a cosmological context without the assumption of ionization equilibrium. We find that a significant fraction of ionized oxygen (O VII and O VIII) in a warm–hot intergalactic medium (WHIM) is not in the ionization equilibrium state at a redshift of $z \simeq0 $. We also investigate the effect on the detectability and observables of WHIM as a consequence of such a deviation from ionization equilibrium. It is found that the detectability of WHIM is not altered very much both through its emission and absorption signatures, but the line ratios between O VII and O VIII are significantly different from those in the ionization equilibrium state.
Detailed XMM-Newton Observation of the Cluster of Galaxies Abell 1060
Authors: Hayakawa Akira , Hoshino Akio , Ishida Manabu , Furusho Tae , Yamasaki Noriko Y. , Ohashi Takaya 
Published: March 2014

Abstract
We present results from an XMM-Newton observation of the non-cooling flow cluster Abell 1060. The large effective area of XMM-Newton enabled us to investigate the nature of this cluster in unprecedented detail. From the observed surface brightness distribution, we found that the gravitational mass distribution is well described by the Navarro–Frenk–White (1997, ApJ, 490, 493) profile, but with a central density slope of $\sim 1.5$. We undoubtedly detected a radial temperature decrease of as large as $\sim 30\%$ from the center to the outer region ($r \sim 13'$), which seems to be much larger than that expected from the temperature profile averaged over nearby clusters. We established that the temperature of a region $\sim 7'$ southeast of the center is higher than the azimuthally averaged temperature of the same radius by $\sim 20\%$. Since the pressure of this region already reaches equilibrium with the environment, the temperature structure can be interpreted as having been produced between $4 \times 10^{7} \,\mathrm{yr}$ (the sound-crossing time) and $3 \times 10^{8} \,\mathrm{yr}$ (the thermal conduction time) ago. We found that a high-metallicity blob located at $\sim {1\rlap {.}{}^{\mathrm {\prime }}5}$ northeast of NGC 3311 is more extended, and its iron mass of $1.9 \times 10^{7} \,{{{M}_{\odot}}}$ is larger by an order of magnitude than that estimated from our Chandra observation. The amount of iron can still be considered as being injected solely from the elliptical galaxy NGC 3311.
First Integrals of Adiabatic Stellar Oscillations
Authors: Takata Masao 
Published: March 2014

Abstract
We consider the equations of linear adiabatic oscillations of stars analytically. There are two known first integrals of nonradial oscillations of spherically symmetric stars, which exist for any stellar structure. One is obtained by integrating the linearized Poisson equation in the case of radial oscillations. The other is derived from momentum conservation in the case of dipolar oscillations. Both of these integrals reduce the order of the differential equations from four to two, which is not trivial. We find that this property can be understood from the fact that the problem of adiabatic stellar oscillations can be formulated as a Hamiltonian system. We then examine the symmetry of the system that corresponds to these first integrals. We finally show that there is no other first integral that is valid for arbitrary structures of stars.
An Optically Dark GRB Observed by HETE-2: GRB 051022
Authors: Nakagawa Yujin E. , Yoshida Atsumasa , Sugita Satoshi , Tanaka Kaoru , Ishikawa Nobuyuki , Tamagawa Toru , Suzuki Motoko , Shirasaki Yuji , Kawai Nobuyuki , Matsuoka Masaru , Atteia Jean-Luc , Pelangeon Alexandre , Vanderspek Roland , Crew Geoffrey B. , Villasenor Joel S. , Butler Nat , Doty John P. , Ricker George R. , Pizzichini Graziella , Donaghy Timothy Q. , Lamb Donald Q. , Graziani Carlo , Sato Rie , Maetou Miki , Arimoto Makoto , Kotoku Jun’ichi , Jernigan J. Garrett , Sakamoto Takanori , Olive Jean-François , Boer Michel , Fenimore Edward E. , Galassi Mark , Woosley Stanford E. , Yamauchi Makoto , Takagishi Kunio , Hatsukade Isamu 
Published: March 2014

Abstract
GRB 051022 was detected at 13:07:58 on 2005 October 22 UT by HETE-2. The location of GRB 051022 was determined immediately by the flight localization system. This burst contained multiple pulses, and had a rather long duration of about 190 s. The detections of candidate X-ray and radio afterglows were reported, whereas no optical afterglow was found. Optical spectroscopic observations of the host galaxy revealed a redshift of $z = 0.8$. Using data derived by a HETE-2 observation of the prompt emission, we found absorption of $N_{\mathrm{H}} = (8.8_{-2.9}^{+3.1}) \times 10^{22} \,\mathrm{cm}^{-2}$ and visual extinction of $A_{V} = 49_{-16}^{+17}$ mag in the host galaxy. If this is the case, no detection of any optical transient would be quite reasonable. The absorption derived by Swift XRT observations of the afterglow is fully consistent with those obtained from an early HETE-2 observation of the prompt emission. Our analysis implies an interpretation that the absorbing medium may be outside the external shock at $R \sim 10^{16} \,\mathrm{cm}$, which could be a dusty molecular cloud.
Threshold between Spontaneous and Cloud-Collisional Star Formation
Authors: Shinya Komugi , Sofue Yoshiaki , Egusa Fumi 
Published: March 2014

Abstract
Based on simple physical and geometric assumptions, we have calculated the mean surface molecular density of spiral galaxies at the threshold between star formation induced by cloud-cloud collision and spontaneous gravitational collapse. The calculated threshold is approximately $\log \Sigma_\mathrm{crit} \sim 2.5$, where $\Sigma \;[{{{M}_{\odot}}} \,\mathrm{pc}^{-2}]$ is the observed surface mass density of an assumed flat gas disk. Above this limit, the rate of molecular cloud collisions dominates over spontaneous molecular cloud collapse. This model may explain the apparent discontinuity in the Schmidt law found recently at $2 \lesssim \log \Sigma \lesssim 3$.
Optical Photometrical Observations and Variability for Quasar 4C 29.45
Authors: Fan Jun Hui , Tao Jun , Qian Bo Chen , Gupta Alok C. , Liu Yi , Yuan Yu-Hai , Yang Jiang-He , Wang Hong Guang , Huang Y. 
Published: March 2014

Abstract
We reported the result of the long-term optical variability of the blazar 4C 29.45s (QSO 1156$+$295, Ton 599), carried out by optical photometric observations in the Johnson $V$, Cousins $RI$ passbands during 1997 April to 2002 March. We used the 1.56-m telescope of the Shanghai Astronomical Observatory at Sheshan, China, and compiled the post-1974 optical photometric data of the blazar by combining our new observations with the published optical data, and found maximum variations in different passbands: $\Delta U = 4.41 \,\mathrm{mag}, \Delta B = 5.55 \,\mathrm{mag}, \Delta V = 4.53 \,\mathrm{mag}, \Delta R = 5.80 \,\mathrm{mag}$, and $\Delta I = 5.34 \,\mathrm{mag}$. The average color indices are: $U-B =-0.54 \pm 0.18 \,\mathrm{mag}, B-V = 0.56 \pm 0.21 \,\mathrm{mag}, B-R = 0.93 \pm 0.18 \,\mathrm{mag}, B-I = 1.51 \pm 0.24 \,\mathrm{mag}, V-R = 0.44 \pm 0.15 \,\mathrm{mag}$, and $V-I = 1.03 \pm 0.23 \,\mathrm{mag}$. The post-1974 data give us an excellent opportunity to search for the existence of a possible periodicity in the light curve. In searching for periodicity in the $R$ passband light curve, we performed a Jurkevich test and power spectral (Fourier) analysis methods, as well as CLEANest algorithms to remove false signals. We found possible periods of 3.55 and 1.58 years. A possible mechanism for the periodic variability was analyzed.
An Extrasolar Planet Transit Search with Subaru Suprime-Cam
Authors: Urakawa Seitaro , Yamada Toru , Suto Yasushi , Turner Edwin L. , Itoh Yoichi , Mukai Tadashi , Tamura Motohide , Wang Yiping 
Published: March 2014

Abstract
We report the results of a prototype photometric search for transiting extrasolar planets using Subaru Suprime-Cam. Out of about 100000 stars monitored around the Galactic plane ($l=90^{\circ}, b=0^{\circ}$), we find that 7700 show photometric precision better than 1% for 60s exposures, which is required to detect extrasolar planets by the transit method. Thus, Suprime-Cam has the photometric stability and accuracy necessary for a transiting planet survey. During this observing run, we detected three objects (around 18.5 mag for $i'$-band) that exhibit a single full transit-like light curve with a fractional depth of $&lt; 5\%$. While a spectroscopic follow-up remains to be done using future telescopes in the 20–30 m class, the estimated parameters for the three systems are consistent with the planetary size companions around main-sequence stars. We also found two eclipsing binary candidates and eleven variable stars exhibiting W UMa-like light curves.
Do Ultraluminous X-Ray Sources Really Contain Intermediate-Mass Black Holes?
Authors: Vierdayanti Kiki , Mineshige Shin , Ebisawa Ken , Kawaguchi Toshihiro 
Published: March 2014

Abstract
An open question remains whether Ultraluminous X-ray Sources (ULXs) really contain intermediate-mass black holes (IMBHs). We carefully investigated the XMM-Newton EPIC spectra of four ULXs that were claimed to be strong candidates of IMBHs by several authors. We first tried fitting by the standard spectral model of disk blackbody (DBB) ${+}$ power-law (PL), finding good fits to all of the data, in agreement with others. We, however, found that the PL component dominates the DBB component at $\sim 0.3$ to 10keV. Thus, the black hole parameters derived solely from the minor DBB component are questionable. Next, we tried to fit the same data by the “$p$-free disk model” without the PL component, assuming an effective temperature profile of $T_{\mathrm{eff}} \propto r^{-p}$, where $r$ is the disk radius. Interestingly, in spite of one less free-model parameter, we obtained similarly good fits with much higher innermost disk temperatures, $1.8 &lt; kT_{\mathrm{in}} &lt; 3.2 \,\mathrm{keV}$. More importantly, we obtained $p \sim 0.5$, just the value predicted by the slim (super-critical) disk theory, rather than $p = 0.75$ that is expected from the standard disk model. The estimated black hole masses from the $p$-free disk model are much smaller; $M \lesssim 40 \,{{{M}_{\odot}}}$. Furthermore, we applied a more sophisticated slim-disk model by Kawaguchi (2003, ApJ, 593, 69), and obtained good fits with roughly consistent black hole masses. We thus conclude that the central engines of these ULXs are super-critical accretion flows to stellar-mass black holes.
Overdensity of X-Ray Sources in the Field of Two Nearby Clusters of Galaxies: XMM-Newton View of A 194 and A 1060
Authors: Hudaverdi Murat , Kunieda Hideyo , Tanaka Takeshi , Haba Yoshito , Furuzawa Akihiro , Tawara Yuzuru , Ercan E. Nihal 
Published: March 2014

Abstract
Two nearby clusters of galaxies, A194 ($z = 0.018$) and A1060 ($z = 0.0114$), have been analyzed for their X-ray point-source properties with XMM-Newton EPIC-PN data. A multi-band source detection technique was applied to both of the clusters, resulting in 46 sources from the A194 field and 32 sources from the A1060 field, respectively. The cumulative $\log (N) \hbox{--} \log(S)$ for a flux limit of $F_{\mathrm{X}} \geq 1 \times 10^{-14} \,\mathrm{erg} \,\mathrm{cm}^{-2} \,\mathrm{s}^{-1}$ was calculated and compared with that of the Lockman Hole. A $\sim 3\,\sigma$ excess of X-ray sources was found for the cluster regions. Considering the higher fraction observed in optical studies from the clusters, we estimate that the cluster source density is 6-times higher than the blank-field source density, and 15-times higher than the local group. Our X-ray selected sources have luminosity values of $10^{39.6} \leq L_{\mathrm{X}} \leq 10^{41.4} \,\mathrm{erg} \,\mathrm{s}^{-1}$, in which X-ray emission from LMXBs, hot halos and starburst galaxies becomes noticeable. The significance of the source-density excess gradually vanishes for sources with $L_{\mathrm{X}} \geq 10^{40.5} \,\mathrm{erg} \,\mathrm{s}^{-1}$, at which point the source density becomes comparable to that of the blank-field level. Considering this confined low-luminosity range and the X-ray to optical luminosity ratios ($L_{\mathrm{X}} / L_{\mathrm{B}}$), the observed overdensity is ascribed to AGN fueling by its infall into cluster environment for $L_{\mathrm{X}} \leq 10^{40.5} \,\mathrm{erg} \,\mathrm{s}^{-1}$ in the X-ray luminosity function. However, the quenching of AGN activity by the deep cluster potential explains why the excess of the source density vanishes for brighter sources.