bluuebunny/crossref_metadata_2025 huggingface dataset:
Core Structure of Intracluster Gas: Effects of Radiative Cooling on Core Sizes
Authors: Akahori Takuya , Masai Kuniaki
Published: March 2014

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

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 $V_{\mathrm{lsr}}<0$ 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 $\vert l\vert < {1\rlap {.}{}^{\mathrm {\circ }}5}$, 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

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

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

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.
Chandra and XMM-Newton Observations of a Group of Galaxies, HCG 62
Authors: Morita Umeyo , Ishisaki Yoshitaka , Yamasaki Noriko Y. , Ota Naomi , Kawano Naomi , Fukazawa Yasushi , Ohashi Takaya
Published: March 2014

We present results from Chandra and XMM-Newton observations of a bright group of galaxies, HCG 62. There are two cavities at about $30{}^{\prime\prime}$ northeast and $20{}^{\prime\prime}$ southwest of the central galaxy in the Chandra image. The energy spectrum shows no significant change in the cavity compared with that in the surrounding region. The radial X-ray profile is described by the sum of the 3-$\beta$ components with core radii of about 2, 10, and 160 kpc. We studied the radial distributions of the temperature and the metal abundance with a joint spectral fit for both data; two temperatures were required in the inner $r< 2'$ (36 kpc) region. A sharp drop of the temperature at $r \sim 5'$ implies a gravitational mass density even lower than the gas density, suggesting that the gas may not be in hydrostatic equilibrium. The Fe and Si abundances are 1–2 solar at the center, and drop to about 0.1 solar at $r \sim 10'$. The O abundance is less than 0.5 solar, and shows a flatter profile. The observed metal distribution supports the view that iron and silicon are produced by type Ia supernova (SN Ia) in the central galaxy, while galactic winds by SN II have caused a wide distribution of oxygen. The supporting mechanism of the cavity is discussed. The pressure for the sum of electrons and the magnetic field is too low to displace the hot group gas, and the required pressure due to high-energy protons is nearly 700-times higher than the electron pressure. This leaves the origin of the cavities a puzzle; we also discuss other possible origins of the cavities.
[C I] 809 GHz Imaging of the NGC 6334 Complex
Authors: Kim Sungeun , Narayanan Desika
Published: March 2014

We present Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) observations of submillimeter emissions from the NGC 6334 complex for both the $^{12}[\mathrm{C {I}}] \; {{3\atop} \mathrm{P}}_2 \rightarrow {{3\atop} \mathrm{P}}_1$ fine-structure line of atomic carbon and the ${{12\atop} \mathrm{CO}} J = 4 \rightarrow 3$ rotational transition of CO. We detected strong $^{12}[\mathrm{C {I}}] \; {{3\atop} \mathrm{P}}_2 \rightarrow {{3\atop} \mathrm{P}}_1$ emission from the entire star-forming NGC 6334 complex, and present maps of $^{12}[\mathrm{C {I}}] \; {{3\atop} \mathrm{P}}_2 \rightarrow {{3\atop} \mathrm{P}}_1$ emission and ${{12\atop} \mathrm{CO}} J = 4 \rightarrow 3$ emission. Comparing these maps with archival ASCA data, we show that, to the south of NGC 6334, the [C I] emissions are likely to be associated with strong X-ray emissions from the FIR sources. However, the calculation using the X-ray dissociation region model shows that the majority of the [C I] emission can not arise from X-ray dissociation of the cloud. Alternatively, far-ultraviolet radiation produced in the photodissociation regions is expected to contribute to dissociate the carbon monoxide in the NGC 6334 complex.
First Integrals of Adiabatic Stellar Oscillations
Authors: Takata Masao
Published: March 2014

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

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

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

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

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 $< 5\%$. 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

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, $1.8 < kT_{\mathrm{in}} < 3.2 \,\mathrm{keV}$. 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.
λ Bootis-Like Abundances in the Vega-Like, γ Doradus Type-Pulsator HD 218396
Authors: Sadakane Kozo
Published: March 2014

The elemental abundances of 16 elements in the Vega-like and $\gamma$ Doradus-type variable star HD 218396 have been determined. A model atmosphere with $T_{\mathrm{eff}} = 7250 \,\mathrm{K}, \log g = 4.30$, and a metallicity of $[\mathrm{M/H}] =-0.50$ was used. A moderate, but definite, deficiency in the abundance of iron, $[\mathrm{Fe/H}] =-0.55 \pm 0.1$, has been confirmed. Other elements, Na through Ba, are also as under-abundant as Fe. On the other hand, two light elements, C and O, show solar abundances. These findings confirm the $\lambda$ Bootis nature of this star, which had been so classified based on a low-resolution optical spectrum. The observed abundance pattern provides a constraint in understanding the nature of this interesting object, which shows excess emission in the infrared region, implying that the star is accompanied by a dusty-debris disk, and at the same time shows photometric and spectroscopic variations arising from non-radial high-order g-mode pulsations.
On the X-Ray and Mass Distribution in the Merging Galaxy Cluster 1E 0657−56: Ram Pressure-Stripping in Substructures with an NFW Density Profile
Authors: Takizawa Motokazu
Published: March 2014

We investigated the X-ray and mass distribution in the merging galaxy cluster 1E 0657$-$56. We also studied head-on collisions of two virialized clusters with an NFW density profile in the $\Lambda$CDM universe using an $N$-body plus hydrodynamical code. A clear off-set of an X-ray peak from a mass peak, which is like what is reported in Clowe, Gonzalez, and Markevitch (2004), was first reproduced in $N$-body plus hydrodynamical simulations. We estimated the ram pressure-stripping conditions of the substructure in mergers of two NFW dark halos using a simple analytical model. We find that the ram pressure dominates the gravity of the substructure when the smaller cluster’s mass is less than approximately one tenth of the larger cluster’s mass. The characteristic X-ray and mass structures found in 1E 0657$-$56 suggest that neither the ram pressure nor the gravitational bound force overwhelms the other, and that the mass ratio between the progenitors is near the critical value mentioned above.
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

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.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
SuprimeCam Observation of Sporadic Meteors during Perseids 2004
Authors: Iye Masanori , Tanaka Mikito , Yanagisawa Masahisa , Ebizuka Noboru , Ohnishi Kouji , Hirose Chikako , Asami Naoko , Komiyama Yutaka , Furusawa Hisanori
Published: March 2014

We report on serendipitous findings of 13 faint meteors and 44 artificial space objects by SuprimeCam imaging observations during 2004 August 11–16. The meteors, at about 100 km altitude, and artificial satellites/debris in orbit, at 500 km altitude or higher, were clearly discriminated by their apparent defocused image sizes. We defined a peak video-rate magnitude by comparing the integrated photon counts from the brightest portion of the track traversed within 33 ms to those from a 0-mag star during the same time duration. The magnitudes thus defined for the meteors, including 1 Perseid, 1 Aquarid, and 11 sporadic meteors, were in the range 4.0 $< V_{\rm vr} <$ 6.4 and 4.1 $< I_{\rm vr} <$ 5.9. Although the spatial resolution is insufficient to resolve the source size of anything smaller than about 1 m, we developed a new estimate of the collisionally excited column diameter of these meteors. A diameter as small as a few mm was derived from their collisionally excited [O I] 5577 photon rates, meteor speed, and the volume density of the oxygen atoms at an altitude of 100 km. The actual column diameter of the radiating zone, however, could be as large as few 100 m because the excited oxygen atoms travel that distance before they emit forbidden lines in 0.7 s of its average lifetime.
Dependence of Temporal Properties on Energy in Long-Lag, Wide-Pulse Gamma-Ray Bursts
Authors: Zhang Fu-Wen , Qin Yi-Ping , Zhang Bin-Bin
Published: March 2014

We employed a sample by Norris et al. (2005, ApJ, 625, 324) to study the dependence of the pulse temporal properties on energy in long-lag, wide-pulse gamma-ray bursts. Our analysis shows that the pulse peak time, rise time scale, and decay time scale are power-law functions of energy, which is a preliminary report on the relationships between the three quantities and energy. The power-law indexes associated with the pulse width, rise time scale, and decay time scale are correlated, and the correlation between the indexes associated with the pulse width and the decay time scale is more obvious. In addition, we have found that the pulse peak lag is strongly correlated with the CCF lag, but the centroid lag is less correlated with the peak lag and the CCF lag. Based on these results and some previous investigations, we tend to believe that all energy-dependent pulse temporal properties may come from the joint contribution of both the hydrodynamic processes of the outflows and the curvature effect, where the energy-dependent spectral lag may be mainly dominated by the dynamic process, and the energy-dependent pulse width may be mainly determined by the curvature effect.