bluuebunny/crossref_metadata_2025_split huggingface dataset:
A RIAF Interpretation for the Past Higher Activity of the Galactic Center Black Hole and the 511 keV Annihilation Emission
Authors: Totani Tomonori 
Published: March 2014

Abstract
There are several lines of evidence to show that the supermassive black hole at the Galactic center had higher activities in the past than directly observed at present. It is shown here that these lines of evidence can quantitatively and consistently be explained if the mean accretion rate during the past $\sim 10^7 \,\mathrm{yr}$ has been $\sim 10^{3\hbox{--}4}$ times higher than the current rate, based on the picture of radiatively inefficient accretion flow (RIAF) and associated outflow that has been successfully applied to Sgr $\mathrm{A}^{*}$. We argue that this increased rate and its duration are theoretically reasonable in the Galactic center environment, while the accretion rate suddenly dropped about 300 yr ago, most likely because of the shell passage of the supernova remnant Sgr A East. The chance probability of witnessing Sgr $\mathrm{A}^{*}$ in such a low state is not extremely small ($\sim 0.5\%$). The outflow energetics is sufficient to keep the hot ($\sim 8 \,\mathrm{keV}$) diffuse gas observed in the Galactic center region. It is then shown that a significant amount of positrons should have been created around the event horizon during the higher activity phase, and injected into interstellar medium by the outflow. The predicted positron production rate and propagation distance are close to those required to explain the observed 511 keV annihilation line emission from the Galactic bulge, giving a natural explanation for the large bulge-to-disk ratio of the emission. The expected injection energy into interstellar medium is $\sim \mathrm{MeV}$, which is also favorable for an explanation of the 511 keV line emission.
HOCO+ toward the Galactic Center
Authors: Deguchi Shuji , Miyazaki Atsushi , Minh Young Chol 
Published: March 2014

Abstract
We have identified a weak thermal line, U42.767, which has been detected only in the directions toward Sgr A and Sgr B2, as the $\mathrm{HOCO}^{+} 2_{02} \hbox{--}1_{01}$ transition. Because of the proximity of this line to the SiO maser line at 42.821 GHz ($J = 1 \hbox{--} 0 v = 2$), it was observable simultaneously in $\sim 43 \,\mathrm{GHz}$ SiO maser searches at Nobeyama. From the past data of SiO maser surveys of infrared objects in the Galactic center, we created a map of emission distribution of $\mathrm{HOCO}^{+}$ in the Sgr A molecular cloud as well as maps of the ${{29\atop} \mathrm{SiO}} J = 1 \hbox{--} 0 v=0$ thermal emission and H53$\alpha$ emission. The emission distribution of $\mathrm{HOCO}^{+}$ was quite similar to that of ${{29\atop} \mathrm{SiO}}$ emission. This suggests that an enhancement of the $\mathrm{HOCO}^{+}$ abundance in the galactic center is induced by shock activities, which release $\mathrm{CO}_2$ molecules frozen on grains into gases.
First Results from the XMM-Newton Slew Survey
Authors: Read Andrew , Saxton Richard , Esquej Pilar , Freyberg Michael , Altieri Bruno 
Published: March 2014

Abstract
We have attempted to analyse all the available data taken by XMM-Newton as it slews between targets. This slew survey, the resultant source catalogue, and the analysis procedures used are described in an accompanying paper. In this letter we present the initial science results from the survey. To date, detailed source searching has been performed in three X-ray bands (soft, hard, and total) in the EPIC-pn 0.2–12keV band over $\sim 6300 \,\mathrm{deg}^2$ ($\sim 15\%$ of the sky), and approximately 4000 X-ray sources have been detected ($\sim 55\%$ of which have IDs). A great variety of sources are seen, including AGN, galaxies, clusters and groups, active stars, SNRs, low–and high-mass XRBs, and white dwarfs. In particular, as this survey constitutes the deepest ever hard-band 2–12keV all-sky survey, a large number of hard sources are detected. Furthermore, the great sensitivity and low background of the EPIC-pn camera are especially suited to emission from extended sources, and interesting spatial structure is observed in many supernova remnants and clusters of galaxies. The instrument is very adept at mapping large areas of the X-ray sky. Also, as the slew survey is well matched to the ROSAT all-sky survey, long-term variability studies are possible, and a number of extremely variable X-ray sources, some possibly due to the tidal disruption of stars by central supermassive black holes, have been discovered.
Dust in Hot Plasma of Nearby Dusty Elliptical Galaxies Observed with the Spitzer Space Telescope
Authors: Kaneda Hidehiro , Onaka Takashi , Kitayama Tetsu , Okada Yoko , Sakon Itsuki 
Published: March 2014

Abstract
We report on mid- and far-IR Spitzer observations of 7 nearby dusty elliptical galaxies by using the Multiband Imaging Photometer for Spitzer (MIPS) and Infrared Spectrograph (IRS). Our sample galaxies are known to contain excessive amounts of interstellar dust against sputtering destruction in hot plasma filling the interstellar space of elliptical galaxies. In order to study the origin and the properties of the excess dust in the hot plasma, we selected galaxies with a wide range of X-ray luminosities, but similar optical luminosities for our Spitzer Guest Observers (GO1) program. The 7 galaxies were detected at the MIPS 24$\mu$m, 70$\mu$m, and 160$\mu$m bands; the far- to mid-IR flux ratios of relatively X-ray-bright elliptical galaxies are lower than those of X-ray-faint galaxies. From the IRS spectra, polycyclic aromatic hydrocarbon (PAH) emission features were detected significantly from 5 of the 7 galaxies; the emission intensities are weaker as the X-ray luminosity of the galaxy is larger. We have found a correlation between the far- to mid-IR flux ratio and the equivalent width of the PAH emission feature. We have obtained an apparent spatial correspondence between the mid-IR and X-ray distributions in the outer regions for the three X-ray-brightest galaxies in our sample. Possible interpretations for our observational results are discussed.
Hard X-Ray Properties of Groups of Galaxies as Observed with ASCA
Authors: Nakazawa Kazuhiro , Makishima Kazuo , Fukazawa Yasushi 
Published: March 2014

Abstract
X-ray spectra of groups of galaxies, obtained with the GIS instrument onboard ASCA, were investigated for diffuse hard X-rays in excess of the soft thermal emission from their inter-galactic medium (IGM). In total, 18 objects with IGM temperatures of 0.7–1.7 keV were studied, including HCG 62 in particular. Non X-ray backgrounds in the GIS spectra were carefully estimated and subtracted. The IGM emission was represented by up to two temperature thermal models, which was determined in a soft energy band below 2.5 keV, mainly by the SIS data. When extrapolated to a higher energy range of 4–8 keV, this thermal model under-predicted the background-subtracted GIS counts in HCG 62 and RGH 80 by $\gt$ 2$\sigma$ significance, even though the background uncertainties and the IGM modeling errors were carefully accounted. A hard excess could also be present in NGC 1399. The excess was successfully explained by a power-law model with a photon index of $\sim 2$, or a thermal emission with a temperature exceeding $\sim3$keV. In HCG 62, the 2–10 keV luminosity of the excess hard component was found to be $5.5\times10^{41}$erg s$^{-1}$ at 2–10 keV, which is $\sim 30\%$ of the thermal IGM luminosity in 0.7–2.5 keV. Non-thermal and thermal interpretations of this excess components are discussed.
X-Ray Emission-Line Profiles of Three Early-Type Stars Observed with Chandra
Authors: Yamamoto Norimasa , Takano Haruko , Kitamoto Shunji , Kohmura Takayoshi 
Published: March 2014

Abstract
We analyzed the X-ray emission-line profiles of three early-type stars ($\zeta$ Pup, $\delta$ Ori, and $\tau$ Sco) obtained with Chandra. A phenomenological model, where X-ray sources are distributing in wind above some lower limit radius, can fit the line profiles of $\zeta$ Pup and $\delta$ Ori; however, the fitting requires a much smaller absorption than expected from the mass-loss rate. This suggests that, if this phenomenological model represents the real X-ray emission region, there is substantial ionization or clumping of the stellar wind. The parameters derived from the line profile of $\tau$ Sco indicate that the X-ray-emitting plasma is concentrated on the stellar surface, suggesting the existence of a confined plasma on the stellar surface.
High-Resolution and High-S/N Spectrum Atlas of Vega
Authors: Takeda Yoichi , Kawanomoto Satoshi , Ohishi Naoko 
Published: March 2014

Abstract
We present a digital spectral atlas of Vega covering from violet to the near-IR region ($\sim$ 3900–8800 $\rmÅ$), which has such a high resolution ($R \sim 100000$) and high signal-to-noise ratio (typically $\sim$ 1000–2000 on the average) as to allow a detailed line-profile analysis. In addition, theoretically simulated spectra and lists of lines predicted to have appreciable strengths are also provided, which may be useful for identifying or searching lines on the atlas. Besides, the spectra of Regulus (a representative rapid rotator) obtained at the same night are appended as a reference of telluric lines.
Giant Molecular Association in Spiral Arms of M 31: I. Evidence for Dense Gas Formation via Spiral Shock Associated with Density Waves?
Authors: Tosaki Tomoka , Shioya Yasuhiro , Kuno Nario , Hasegawa Takashi , Nakanishi Kouichiro , Matsushita Satoki , Kohno Kotaro 
Published: March 2014

Abstract
We present observations of $^{12}$CO ($J$ = 1–0), $^{13}$CO ($J$ = 1–0), and $^{12}$CO ($J$ = 3–2) emissions toward a Giant Molecular Association (GMA) in the southern spiral arm of M 31 using the NRO 45 m and the ASTE 10 m telescopes. Observed regions are 3$^\prime \times$ 4$^\prime$ (0.6 kpc $\times$ 0.8 kpc) with an angular resolution of 16$^{\prime\prime}$–17$^{\prime\prime}$ for $^{12}$CO (1–0) and $^{13}$CO (1–0), and 1.$^\prime$2 $\times$ 1.$^\prime$4 with 23$^{\prime\prime}$ for $^{12}$CO (3–2). The GMA has a size of a few 100 pc and a mass of 5.6$\times 10^6 M_\odot$. The $^{12}$CO (1–0) to $^{13}$CO (1–0) integrated intensity ratio ($R_{12/13}$) and the $^{12}$CO (3–2) to $^{12}$CO (1–0) ratio ($R_{3-2/1-0}$), averaged over the entire region of the GMA, are $\sim 10$ and 0.3, respectively. These line ratios suggest gas densities of (3–6) $\times 10^2$ cm$^{-3}$ at a temperature of 15–25 K, which are similar to, or slightly larger than, those of GMCs in the Galactic disk. We found a radial gradient of $R_{12/13}$ within the GMA, ranging from 6 at the center to 14 at the edges. The distribution of $R_{12/13}$ shows a smooth structure with an overall density gradient. The GMA consists of two velocity components, blue ($\sim-505$ km s$^{-1}$) and red ($\geq-490$ km s$^{-1}$). In both the $^{12}$CO (1–0) and $^{13}$CO (1–0) profiles, the blue component shows a strong peak intensity and a narrow velocity width, while the red is weaker and wider. The $R_{12/13}$ value of the red component is 5 and that of the blue is 16, indicating that the red component has a higher gas density. Moreover, we suggest that the red component is “post-shock” dense gas decelerated by shock due to the density wave.
Effects of Smoothing Functions in Cosmological Counts-in-Cells Analysis
Authors: Murata Yoshitaka , Matsubara Takahiko 
Published: March 2014

Abstract
A method for a counts-in-cells analysis of the galaxy distribution is investigated with arbitrary smoothing functions for obtaining the galaxy counts. We explore the possiblity of optimizing the smoothing function, while considering a series of $m$-weight Epanechnikov kernels. The popular top-hat and Gaussian smoothing functions are two special cases in this series. In this paper, we mainly consider the second moments of counts-in-cells as a first step. We have analytically derived the covariance matrix among different smoothing scales of cells, while taking into account possible overlaps between cells. We find that the Epanechnikov kernel of $m=1$ is better than top-hat and Gaussian smoothing functions in estimating cosmological parameters. As an example, we estimated expected parameter bounds that come only from an analysis of the second moments of the galaxy distributions in a survey that is similar to the Sloan Digital Sky Survey.
The Complex Structure of the Mg II $\lambda\lambda$ 2795.523, 2802.698 ${\rmÅ}$ Regions of 64 Be Stars
Authors: Evaggelia LYRATZI , Danezis Emmanouel , Popović Luka Č. , Dimitrijević Milan S. , Nikolaidis Dimitris , Antoniou Antonis 
Published: March 2014

Abstract
Here we consider the presence of absorption components shifted to the violet or red side of the main spectral line (satellite or discrete absorption components, i.e., SACs or DACs) in the regions of the Mg II resonance lines in Be stars as well as their kinematical characteristics. Namely, our objective is to check whether there exists a common physical structure for the atmospheric regions creating SACs or DACs of the Mg II resonance lines. In order to do this, a statistical study of the Mg II $\lambda\lambda$ 2795.523, 2802.698 Å lines in the spectra of 64 Be stars of all spectral subtypes and luminosity classes was performed. We found that the atmospherical absorption regions where the Mg II resonance lines originated may be formed of several independent density layers of matter that rotate with different velocities. It was also attempted to separate SACs and DACs according to low or high radial velocity. The emission lines were detected only in the earliest and latest spectral subtypes.
Oblique Shocks in the Magnetic Reconnection Jet in Solar Flares
Authors: Tanuma Syuniti , Shibata Kazunari 
Published: March 2014

Abstract
Strong radio emission of energetic electrons is observed in some solar flares. The origin of energetic electrons is, however, not fully known. In this letter we suggest that oblique shocks are created in reconnection jets in solar flares, and that energetic electrons are accelerated by shocks. We examine 2D MHD simulations of magnetic reconnection with high spacial resolution by assuming an anomalous resistivity model. As a result, magnetic reconnection is found to occur after a secondary tearing instability at the current sheet. We find that, during nonsteady Petschek reconnection, oblique shocks are created by an even mode of the Kelvin–Helmholtz-like instability in the reconnection jet when we assume an anomalous resistivity model. Furthermore, bursty, time-dependent reconnection ejects many plasmoids from the diffusion region, and creates shocks. We suggest that these shocks can be possible sites of particle acceleration in solar flares.
Near-Infrared Polarization Images of the Orion Molecular Cloud 1 South Region
Authors: Jun Hashimoto , Tamura Motohide , Kandori Ryo , Kusakabe Nobuhiko , Nakajima Yasushi , Sato Shuji , Nagashima Chie , Kurita Mikio , Nagata Tetsuya , Nagayama Takahiro , Hough James H. 
Published: March 2014

Abstract
We present the polarization images in the $J, H$, and $K_{\rm s}$ bands of the Orion Molecular Cloud 1 South region. The polarization images clearly show at least six infrared reflection nebulae (IRNe) which are barely seen or invisible in the intensity images. Our polarization vector images also identify the illuminating sources of the nebulae; IRN 1 and 2, IRN 3, 4, and 5, and IRN 6 are illuminated by three IR sources, Source 144–351, Source 145–356, and Source 136–355, respectively. Moreover, our polarization images suggest the candidate driving sources of the optical Herbig-Haro objects for the first time; HH 529, a pair of HH 202 and HH 528 or HH 203/204, and HH 530 and HH 269 are originated from Source 144–351, Source 145–356, and Source 136–355, respectively.
Long-Term Monitoring of the Short Period SU UMa-Type Dwarf Nova, V844 Herculis
Authors: Oizumi Shota , Omodaka Toshihiro , Yamamoto Hiroyuki , Tanada Shunsuke , Yasuda Tatsuki , Arao Yoshihiro , Kodama Kie , Suzuki Miho , Matsuo Takeshi , Maehara Hiroyuki , Nakajima Kazuhiro , Dubovsky Pavol A. , Kato Taichi , Imada Akira , Kubota Kaori , Sugiyasu Kei , Morikawa Koichi , Torii Ken’ichi , Uemura Makoto , Ishioka Ryoko , Tanabe Kenji , Nogami Daisaku 
Published: March 2014

Abstract
We report on the time-resolved CCD photometry of four outbursts of a short-period SU UMa-type dwarf nova, V844 Herculis. We successfully determined the mean superhump periods to be 0.05584(64) d, and 0.055883(3) d for a 2002 May superoutburst, and a 2006 April–May superoutburst, respectively. During the 2002 October observations, we confirmed that the outburst was a normal outburst, which was the first recorded normal outburst in V844 Her. We also examined superhump period changes during the 2002 May and 2006 April–May superoutbursts, both of which showed an increasing superhump period over the course of the plateau stage. In order to examine the long-term behavior of V844 Her, we analyzed archival data over the past ten years since the discovery of this binary. Although photometry is not satisfactory for some superoutbursts, we found that V844 Her showed no precursors or rebrightenings. Based on the long-term light curve, we further confirmed that V844 Her has shown almost no normal outbursts despite the fact that the supercycle of the system is estimated to be about 300 d. In order to explain the long-term light curves of V844 Her, evaporation in the accretion disk may play a role in the avoidance of several normal outbursts, which does not contradict with the relatively a large X-ray luminosity of V844 Her.
A Comprehensive Study of Short Bursts from SGR1806$-$20 and SGR1900$+$14 Detected by HETE-2
Authors: Nakagawa Yujin E. , Yoshida Atsumasa , Hurley Kevin , Atteia Jean-Luc , Maetou Miki , Tamagawa Toru , Suzuki Motoko , Yamazaki Tohru , Tanaka Kaoru , Kawai Nobuyuki , Shirasaki Yuji , Pelangeon Alexandre , Matsuoka Masaru , Vanderspek Roland , Crew Geoff B. , Villasenor Joel S. , Sato Rie , Sugita Satoshi , Kotoku Jun’ichi , Arimoto Makoto , Pizzichini Graziella , Doty John P. , Ricker George R. 
Published: March 2014

Abstract
Temporal and spectral studies of short bursts ($\lesssim$ a few hundred milliseconds) are presented for the soft gamma repeaters (SGRs) 1806$-$20 and 1900$+$14 using the HETE-2 samples. In five years from 2001 to 2005, HETE-2 localized 50 bursts from SGR1806$-$20 and 5 bursts from SGR 1900 $+$14. The cumulative number–intensity distribution of SGR 1806$-$20 in the active year 2004 is well described by a power-law model with an index of $-$1.1$\pm$0.6. It is consistent with previous studies, but burst data taken in other years clearly give a steeper distribution. This may suggest that more energetic bursts could occur more frequently in periods of greater activity. From the data, the spectral evolution during bursts with a time scale of $\gtrsim$ 20 ms does not seem to be common in the HETE-2 sample. The spectra of all short bursts are well reproduced by a two blackbody function with temperatures of $\sim 4$ and $\sim 11$keV. From a timing analysis to the SGR 1806$-$20 data, a time lag of 2.2$\pm$0.4 ms is found between the 30–100 keV and 2–10 keV radiation bands. This may imply (1) a very rapid spectral softening and energy reinjection, (2) diffused (elongated) emission plasma along the magnetic field lines in pseudo-equilibrium with multi-temperatures, or (3) a separate (located at $\lesssim$ 700 Km) emission region of a softer component (say, $\sim$ 4 keV), which could be reprocessed X-rays by higher energy ($\gtrsim$ 11 keV) photons from an emission region near the stellar surface.
Radiative Transfer in Accretion-Disk Winds
Authors: Fukue Jun 
Published: March 2014

Abstract
The radiative transfer equation in an accretion-disk wind is examined both analytically and numerically under a plane-parallel approximation in the subrelativistic regime of $(v/c)^1$, where $v$ is the wind vertical velocity. The emergent intensity is analytically obtained for the case of a large optical depth, where the flow speed and the source function are almost constant. The usual limb-darkening effect, which depends on the direction cosine at the zero-optical depth surface, does not appear, since the source function is constant. Because of the vertical motion of winds, however, the emergent intensity exhibits a velocity-dependent limb-darkening effect, which comes from Doppler and aberration effects. Radiative moments and emergent intensity were also numerically obtained. When the flow speed is small ($v \leq 0.1c$), the radiative structure resembles that of a static atmosphere, where the source function is proportional to the optical depth, and the usual limb-darkening effect exists. When the flow speed becomes large, on the other hand, the flow speed attains the constant terminal one, and the velocity-dependent limb-darkening effect appears. We thus carefully treat and estimate the wind luminosity and limb-darkening effect, when we observe an accretion-disk wind.
Origin of Warm High-Velocity Dense Gas in Ultraluminous Infrared Galaxies
Authors: Wada Keiichi 
Published: March 2014

Abstract
Possible origins of molecular absorption discovered in some ultraluminous infrared galaxies (ULIRGs) are investigated, based on a 3-D hydrodynamic model of star-forming interstellar gas in a galactic central region. The blueshifted, warm ($\sim$ 200–300 K), dense ($\gt10^6$ cm$^{-3}$) molecular gas suggested by the CO absorption in IRAS 08572$+$3915 could be caused by the innermost region of the inhomogeneous interstellar medium (ISM) around a supermassive black hole. The infrequent observations of dense gas with absorption in ULIRGs and type-2 Seyfert galaxies could simply suggest that the high-density regions occupy only a very small volume fraction of the obscuring material. This is naturally expected if the inhomogeneous structure of the ISM is caused by a nonlinear development of instabilities. Since the model predicts a turbulent velocity field in the obscuring material, blue- and red-shifted gases should be observable with nearly the same probability for sufficiently large statistical samples.
A Pole-on Bipolar Outflow from the AGB Star WX Piscium
Authors: Inomata Noritomo , Imai Hiroshi , Omodaka Toshihiro 
Published: March 2014

Abstract
We report on H$_{2}$O masers around the asymptotic giant branch (AGB) star WX Piscium (WX Psc $=$ IRC $+$10011), observed with the Japanese VLBI Network (JVN) at three epochs during a span of 2 months. The H$_{2}$O maser spectrum of WX Psc consists of double peaks with a separation of $\sim$ 30 km s$^{-1}$ centered at the systemic velocity of the star. The maser features are found to split roughly in two concentrations separated by about 60 mas from north to south. The northern concentration involves both blueshifted and redshifted components from both of the double peaks, suggesting that it is near the star driving the outflow. The maser spatiokinematics is well approximated by a radial expansion of a thick shell, except for the blueshifted features in the southern concentration. The spatiokinematics is compared with a fan-shaped morphology found in near-infrared emission, suggesting the existence of a bipolar outflow. Two different models are proposed for explaining the observed maser proper motions: one is a biconically expanding flow with a large opening angle ($2\theta_{\rm cone}=$70${}^\circ$–120${}^\circ$); the other is a collimated outflow with precession. The complicated spatiokinematics of the H$_{2}$O maser features indicates that the star is currently in the process of launching a bipolar outflow in the final stage of the AGB phase, shaping a planetary nebula in the next stage.