bluuebunny/crossref_metadata_2025 huggingface dataset:
X-Ray Study of Rekindled Accretion in the Classical Nova V2491 Cygni
Authors: Takei Dai , Ness Jan-Uwe , Tsujimoto Masahiro , Kitamoto Shunji , Drake Jeremy J. , Osborne Julian P. , Takahashi Hiromitsu , Kinugasa Kenzo
Published: March 2014

We conducted an X-ray spectroscopic study of the classical nova V2491 Cygni using our target-of-opportunity observation data with the Suzaku and XMM-Newton satellites as well as archived data with the Swift satellite. Medium-resolution ( $R$$\sim$ 10–50) spectra were obtained using the X-ray CCD spectrometers at several post-nova epochs on days 9, 29, 40, 50, and 60–150 in addition to a pre-nova interval between days $-$ 322 and $-$ 100, all relative to the time when the classical nova was spotted. We found remarkable changes in the time series of the spectra: (a) In the pre-nova phase and on day 9, the 6.7 keV emission line from Fe XXV was significantly detected. (b) On day 29, no such emission line was found. (c) On day 40, the 6.7 keV emission line emerged again. (d) On days 50 and 60–150, three emission lines at 6.4, 6.7, and 7.0 keV, respectively, from quasi-neutral Fe, Fe XXV, and Fe XXVI were found. Statistically significant changes of the Fe K line intensities were confirmed between days 29 and 50. Based on these phenomena, we conclude that: (1) the post-nova evolution can be divided into two different phases, (2) ejecta is responsible for the X-ray emission in the earlier phase, while rekindled accretion is responsible for the later phase, and (3) the accretion process is considered to be reestablished as early as day 50 when the quasi-neutral Fe emission line emerged, which is a common signature of accretion from magnetic cataclysmic variables.
The Suzaku Discovery of A Hard Power-Law Component in the Spectra of Short Bursts from SGR 0501+4516
Authors: Nakagawa Yujin E. , Makishima Kazuo , Enoto Teruaki
Published: March 2014

Using data with the Suzaku XIS and HXD, spectral studies of short bursts from the soft gamma repeater SGR 0501 $+$ 4516 were performed. In total, 32 bursts were detected during the $\sim\ $ 60 ks of observation conducted in the 2008 August activity. Excluding the strongest one, the remaining 31 bursts showed an average 2–40 keV fluence of $\left(1.0_{-0.5}^{+0.3}\right)$$\times$ 10 $^{-9}\ $ erg cm $^{-2}$ . A 1–40 keV spectrum summed over them leaves significant positive residuals in the HXD-PIN band with $\chi^{2}/$ d.o.f. $=$ 74 $/$ 50, when fitted with a two-blackbody function. By adding a power-law model, the fit became acceptable with $\chi^2/$ d.o.f. $=$ 56 $/$ 48, yielding a photon index of $\Gamma$$=$ 1.0 $_{-0.3}^{+0.4}$ . This photon index is comparable to $\Gamma$$=$ 1.33 $_{-0.16}^{+0.23}$ (Enoto et al. 2010, ApJ, 715, 665) for the persistent emission of the same object obtained with Suzaku. The two-blackbody components showed very similar ratios, both in the temperature and the emission radii, to those comprising the persistent emission. However, the power-law to two-blackbody flux ratio was possibly higher than that of the persistent emission at the 2.6 $\ \sigma$ level. Based on these measurements, average wide-band properties of these relatively weak bursts are compared with those of the persistent emission.
Suzaku View of the Supernova Remnant RCW 86: X-Ray Studies of Newly-Discovered Fe-Rich Ejecta
Authors: Yamaguchi Hiroya , Koyama Katsuji , Uchida Hiroyuki
Published: March 2014

We report on results of imaging and spectral analysis of the supernova remnant (SNR) RCW 86 observed with Suzaku. The SNR is known to exhibit K-shell emission of low ionized Fe, possibly originating from supernova ejecta. We revealed the global distribution of the Fe-rich plasma in the entire remnant, for the first time; the Fe-K emission was clearly detected from the west, north, and south regions, in addition to the X-ray brighter shells of southwest and northeast, where the presence of the Fe-rich ejecta has already been reported. The spectrum of each region is well represented by a three-component model consisting of low- and high-temperature thermal plasmas and non-thermal emission. The lower-temperature component, with elemental abundances of near the solar values, likely originates from the forward shocked interstellar medium, while the Fe-rich ejecta is described by the hotter plasma. From the morphologies of the forward and reverse shocks in the west region, the total ejecta mass is estimated to be 1–2 $\ M_{\odot}$ for the typical explosion energy of $\sim\ $ 1 $\times$ 10 $^{51}\ $ erg. The integrated flux of the Fe-K emission from the entire SNR roughly corresponds to a total Fe mass of about 1 $\ M_{\odot}$ . Both of these estimates suggest a Type Ia supernova origin of this SNR. We also find possible evidence of an Fe-rich clump located beyond the forward-shock front in the north rim, which is reminiscent of ejecta knots observed in the Tycho and Vela SNRs.
Suzaku and XMM-Newton Observations of the Fornax Cluster: Temperature and Metallicity Distribution
Authors: Murakami Hideyoshi , Komiyama Madoka , Matsushita Kyoko , Nagino Ryo , Sato Takuya , Sato Kosuke , Kawaharada Madoka , Nakazawa Kazuhiro , Ohashi Takaya , Takei Yoh
Published: March 2014

Suzaku observed a central region and five offset regions within 0.2 $\ r_{180}$ in the Fornax cluster, a nearby poor cluster, and XMM-Newton mapped the cluster with 15 pointings out to 0.3 $\ r_{180}$ . The distributions of O, Mg, Si, S, and Fe in the intracluster medium (ICM) were studied with Suzaku, and those of Fe and temperature were studied with XMM. The temperature of the ICM gradually decreases with the radius from 1.3 keV at 0.04 $\ r_{180}$ to 1 keV at 0.2–0.3 $\ r_{180}$ . If the new solar abundances of Lodders et al. (2003), ApJ, 591, 1220) and a single-temperature plasma model are adopted, O, Mg, Si, S, and Fe show similar abundances: 0.4–0.6 solar within 0.02–0.2 $\ r_{180}$ . This Fe abundance is similar to those at 0.1–0.2 $\ r_{180}$ in rich clusters and other groups of galaxies. At 0.2–0.3 $\ r_{180}$ , the Fe abundance becomes 0.2–0.3 solar. A two-temperature plasma model yields ICM abundances that are higher by a factor of 1.2–1.5, but give similar abundance ratios among O, Mg, Si, S, and Fe. The northern region has a lower ICM temperature and higher brightness and Fe abundance, whereas the southern region has a higher ICM temperature and lower brightness and Fe abundance. These results indicate that the cD galaxy may have traveled from the north because of recent dynamical evolution. The cumulative oxygen- and iron-mass-to-light ratios (OMLR and IMLR) within 0.3 $\ r_{180}$ are an order of magnitude lower than those of rich clusters and some relaxed groups of galaxies. Past dynamical evolution might have hindered the strong concentration of hot gas in the Fornax cluster's central region. Scatter in the IMLR and similarity in the element abundances in the ICM of groups and clusters of galaxies indicate early metal synthesis.
Brightness of HAYABUSA Spacecraft Reentry: Artificial Fireball
Authors: Ohkawa Takuya , Iijima Yutaka , Sato Mikiya , Ohnishi Kouji , Kagaya Yutaka , Tanabe Tsutomu , Watanabe Jun-ichi
Published: March 2014

During reentry of the HAYABUSA spacecraft, the main body became a bright fireball of full-moon class. While the images were being taken by a team of ground-based observations, it was too bright to saturate the detectors in most of our instruments. In order to estimate the brightness quantitatively, we utilized ghost images of the main body together with the spectral data. We managed to estimate the time variation of the brightness, which had several peaks of flare ups possibly due to a rapid increase of the total cross section of the fragments. The maximum brightness obtained was $-$13.1$\ \pm\ $0.1, the apparent magnitude at 13$^{\rm h}$52$^{\rm m}$19$.\!\!\!^{\rm s}$8 UT, which corresponds to a height of 57.2 km above sea level. The corresponding absolute magnitude is $-$13.7$\ \pm\ $0.1.
13CO(J = 1–0) On-the-Fly Mapping of the Giant H II Region NGC 604: Variation in Molecular Gas Density and Temperature due to Sequential Star Formation
Authors: Muraoka Kazuyuki , Tosaki Tomoka , Miura Rie , Onodera Sachiko , Kuno Nario , Nakanishi Kouichiro , Kaneko Hiroyuki , Komugi Shinya
Published: March 2014

We present $^{13}$CO($J$$=$ 1–0) line emission observations with the Nobeyama 45-m telescope toward the giant H II region NGC 604 in the spiral galaxy M 33. We detected $^{13}$CO($J$$=$ 1–0) line emissions in 3 major giant molecular clouds (GMCs) labeled as GMC-A, B, and C beginning at the north. We derived two line intensity ratios, $^{13}$CO($J$$=$ 1–0)$/$$^{12}$CO($J$$=$ 1–0), $R_{13/12}$, and $^{12}$CO($J$$=$ 3–2)$/$$^{12}$CO($J$$=$ 1–0), $R_{31}$, for each GMC at an angular resolution of 25$”$ (100 pc). The averaged values of $R_{13/12}$ and $R_{31}$ are 0.06 and 0.31 within the whole GMC-A, 0.11 and 0.67 within the whole GMC-B, and 0.05 and 0.36 within the whole GMC-C, respectively. In addition, we obtained $R_{13/12}$$=$ 0.09$\ \pm\ $0.02 and $R_{31}$$=$ 0.76$\ \pm\ $0.06 at the $^{12}$CO($J$$=$ 1–0) peak position of the GMC-B. Under the Large Velocity Gradient approximation, we determined a gas density of 2.8 $\times$ 10$^{3}\ $cm$^{-3}$ and a kinetic temperature of 33$^{+9}_{-5}\ $K at the $^{12}$CO($J$$=$ 1–0) peak position of the GMC-B. Moreover, we determined 2.5 $\times$ 10$^{3}\ $cm$^{-3}$ and 25$\ \pm\ $2 K as the averaged values within the whole GMC-B. We concluded that dense molecular gas is formed everywhere in the GMC-B because the derived gas density not only at the peak position of the GMC, but also averaged over the whole GMC, exceeds 10$^{3}\ $cm$^{-3}$. On the other hand, the kinetic temperature averaged over the whole GMC-B, 25 K, is significantly lower than that at the peak position, 33 K. This is because the H II regions are lopsided to the northern part of the GMC-B; thus, OB stars can heat only the northern part, including the $^{12}$CO($J$$=$ 1–0) peak position, of this GMC.
X-Ray Groups of Galaxies at 0.5 1 in zCOSMOS: Increased AGN Activities in High Redshift Groups
Authors: Tanaka Masayuki , Finoguenov Alexis , Lilly Simon J. , Bolzonella Micol , Carollo C. Marcella , Contini Thierry , Iovino Angela , Kneib Jean-Paul , Lamareille Fabrice , Le Fevre Olivier , Mainieri Vincenzo , Presotto Valentina , Renzini Alvio , Scodeggio Marco , Silverman John D. , Zamorani Gianni , Bardelli Sandro , Bongiorno Angela , Caputi Karina , Cucciati Olga , De La Torre Sylvain , De Ravel Loic , Franzetti Paolo , Garilli Bianca , Kampczyk Pawel , Knobel Christian , Kovac Katarina , Le Borgne Jean-Francois , Le Brun Vincent , LÓPez-Sanjuan Carlos , Maier Christian , Mignoli Marco , Pello Roser , Peng Yingjie , Perez-Montero Enrique , Tasca Lidia , Tresse Laurence , Vergani Daniela , Zucca Elena , Barnes Luke , Bordoloi Rongmon , Cappi Alberto , Cimatti Andrea , Coppa Graziano , Koekemoer Anton M. , Mccracken Henry J. , Moresco Michele , Nair Preethi , Oesch Pascal , Pozzetti Lucia , Welikala Niraj
Published: March 2014

We present a photometric and spectroscopic study of galaxies at 0.5 $\lt$${z}$$\lt$ 1 as a function of the environment based on data from the zCOSMOS survey. There is a fair amount of evidence that galaxy properties depend on the mass of groups and clusters, in the sense that quiescent galaxies prefer more massive systems. We base our analysis on a mass-selected environment using X-ray groups of galaxies, and define the group membership using a large number of spectroscopic redshifts from zCOSMOS. We show that the fraction of red galaxies is higher in groups than in the field at all redshifts probed in our study. Interestingly, the fraction of [O II] emitters on the red sequence increases at higher redshifts in groups, while the fraction does not strongly evolve in the field. This is due to increased dusty star-formation activities and/or increased activities of active galactic nuclei (AGNs) in high-redshift groups. We investigate these possibilities using the 30-band photometry and X-ray data. We find that the stellar population of the red [O II] emitters in groups is old, and there is no clear hint of dusty star-formation activities in those galaxies. The observed increase of red [O II] emitters in groups is likely due to increased AGN activities. However, since our overall statistics are poor, any firm conclusions need to be drawn from a larger statistical sample of ${z}$$\sim$ 1 groups.
Processing of Polycyclic Aromatic Hydrocarbons in Molecular-Loop Regions near the Galactic Center Revealed by AKARI
Authors: Kaneda Hidehiro , Ishihara Daisuke , Mouri Akio , Oyabu Shinki , Yamagishi Mitsuyoshi , Kondo Toru , Onaka Takashi , Fukui Yasuo , Kawamura Akiko , Torii Kazufumi
Published: March 2014

We present an AKARI mid-infrared diffuse map of an area of about 4$^{\circ}$$\times$ 3$^{\circ}$ near the Galactic center in the 9 $\mu$m band. The band intensity is mostly attributed to aromatic hydrocarbon infrared emissions of carbonaceous grains at wavelengths of 6.2, 7,7, 8.6, and 11.3 $\mu$m. We detected 9 $\mu$m emission structures extending from the Galactic plane up to a latitude of $\sim$ 2$^\circ\!\!\!.$5, which have spatial correspondence to molecular loops revealed by NANTEN $^{12}$CO ($J$$=$ 1–0) observations. We have found that the surface brightness at 9 $\mu$m is suppressed near the foot points of the CO loops. The ratios of the 9 $\mu$m to the IRAS 100 $\mu$m brightness show significant depression near such bright regions in CO emission. With AKARI near-infrared 2.5–5 $\mu$m spectroscopy, we find that the 3.3 $\mu$m aromatic hydrocarbon emission is absent in the region associated with the loop, suggesting the processing and destruction of carbonaceous grains in the CO molecular loops.
Combined Spectral and Timing Analysis of the Black Hole Candidate MAXI J1659−152, Discovered by MAXI and Swift
Authors: Yamaoka Kazutaka , Allured Ryan , Kaaret Philip , Kennea Jamie A. , Kawaguchi Toshihiro , Gandhi Poshak , Shaposhnikov Nicholai , Ueda Yoshihiro , Nakahira Satoshi , Kotani Taro , Negoro Hitoshi , Takahashi Ichiro , Yoshida Atsumasa , Kawai Nobuyuki , Sugita Satoshi
Published: March 2014

We report on X-ray spectral and timing results of a new black hole candidate (BHC), MAXI J1659$-$152, with an orbital period of 2.41 hr (shortest among BHCs) in a 2010 outburst from 65 Rossi X-ray Timing Explorer (RXTE) observations and 8 simultaneous Swift and RXTE observations. According to the definitions of the spectral states in Remillard and McClintock (2006, ARA&A, 44, 49), most of the observations have been classified into the intermediate state. All of the X-ray broadband spectra can be modeled by a multi-color disk plus a power-law with an exponential cutoff or a multi-color disk plus a Comptonization component. During the initial phase of the outburst, a high-energy cutoff was visible at 30–40 keV. The innermost radius of the disk gradually decreased by a factor of more than 3 from the onset of the outburst, and reached a constant value of 35$\ d_{10}$cos$\ i$$^{-1/2}$ km, where $\ d_{10}$ is the distance in units of 10 kpc and $\ i$ is the inclination. The type-C quasi-periodic oscillation (QPO) frequency varied from 1.6 Hz to 7.3 Hz in association with a change of the innermost radius, while the innermost radius remained constant during the type-B QPO detections at 1.6–4.1 Hz. Hence, we suggest that the origin of the type-B QPOs is different from that of type-C QPOs, the latter of which would originate from the disk truncation radius. Assuming the constant innermost radius in the latter phase of the outburst as the innermost stable circular orbit, the black hole mass in MAXI J1659$-$152 is estimated to be 3.6–8.0$\ M_{\odot}$ for a distance of 5.3–8.6 kpc and an inclination angle of 60$^{\circ}$–75$^{\circ}$.
A Method of Identifying AGNs Based on Emission-Line Excess and the Nature of Low-Luminosity AGNs in the Sloan Digital Sky Survey. II. The Nature of Low-Luminosity AGNs
Authors: Tanaka Masayuki
Published: March 2014

We have developed a new method of identifying active galactic nuclei (AGNs) and studied the nature of low-luminosity AGNs in the Sloan Digital Sky Survey. This is the latter part of a series of papers in which we consider correlations between the AGN activities and the host-galaxy properties. Based on a sample of AGNs identified by a new method developed in the former part (2012, PASJ, 64, 36), we found that AGNs typically show extinction of $\tau_V$$=$ 1.2, and exhibit a wide range of ionization levels. The finding of ionization levels motivated us to use [O II] $+$ [O III] as an indicator of AGN power. We found that AGNs are preferentially located in massive, red, early-type galaxies. Taking into account a selection bias of the Oxygen-excess method, we showed that strong AGNs are located in active star-forming galaxies, and that rapidly growing super-massive black holes are located in rapidly growing galaxies, which clearly shows the coevolution of super-massive black holes and their host galaxies. This is a surprising phenomenon, given that the growths of black holes and host galaxies occur on their respective physical scales which are very different. Interestingly, the AGN power does not strongly correlate with the host-galaxy mass. It seems that the mass works as a ``switch'' for activating AGNs. The absence of AGNs in low-mass galaxies might be due to the absence of super-massive black holes there, but a dedicated observation of the nuclear region of nearby low-mass galaxies would be necessary to obtain a deeper insight into it.
OAO/ISLE Near-IR Spectroscopy of IRAS Galaxies
Authors: Matsuoka Yoshiki , Yuan Fang-Ting , Takeuchi Yoshitaka , Yanagisawa Kenshi
Published: March 2014

We present the results of the near-infrared (IR) spectroscopy of nine IRAS galaxies (NGC 1266, NGC 1320, NGC 2633, NGC 2903, NGC 3034, Mrk 33, NGC 7331, NGC 7625, NGC 7714) with the ISLE imager and spectrograph mounted on the Okayama Astrophysical Observatory 1.88-m telescope. [Fe II] 1.257$\ \mu$m and Pa$\beta$ emission lines were observed for the whole sample, while H$_2$ 2.121$\ \mu$m and Br$\gamma$ lines were additionally obtained for two sources, whose flux ratios were used as a diagnostic tool of dominant energy sources of the galaxies. We found that the nucleus of NGC 1266 is most likely a low-ionization nuclear emission-line region (LINER), while NGC 2633 and NGC 2903 possibly harbor active galactic nuclei (AGNs). No AGN or LINER signal is found for other objects. In addition, we found the spectral features, which are indicative of some unusual phenomena occurring in the galaxies, such as the large [Fe II] line widths compared to the local escape velocity in NGC 1266. The present work shows the potential ability of ISLE to shed new light on the nature of infrared galaxies, either through a statistical survey of galaxies or an exploration of spectral features found in individual objects.
Data-Oriented Diagnostics of Pileup Effects on the Suzaku XIS
Authors: Yamada Shin’ya , Uchiyama Hideki , Dotani Tadayasu , Tsujimoto Masahiro , Katsuda Satoru , Makishima Kazuo , Takahashi Hiromitsu , Noda Hirofumi , Torii Shunsuke , Sakurai Soki , Enoto Teruaki , Yuasa Takayuki , Koyama Shu , Bamba Aya
Published: March 2014

We present the results of a systematic study of pileup phenomena seen in the X-ray Imaging Spectrometer, an X-ray CCD instrument, onboard the Suzaku observatory. Using a data set of observed sources in a wide range of brightness and spectral hardness, we characterized the pileup fraction, spectral hardening, and grade migration as a function of the observed count rate in a frame per pixel. Using the pileup fraction as a measure of the degree of pileup, we found that the relative spectral hardening (the hardness ratio normalized to the intrinsic spectral hardness), branching ratio of split events, and that of detached events increase monotonically as the pileup fraction increases, despite the variety of brightness and hardness of the sample sources. We derived the pileup fraction as a function of radius used for event extraction. Upon practical considerations, we found that events outside of the radius with a pileup fraction of 1% or 3% are useful for spectral analysis. We present relevant figures, tables, and software for the convenience of users who wish to apply our method for their data reduction of piled-up sources.
Detection of CO (J = 1–0) Emission from Barred Spiral Galaxies at z$\boldsymbol{\sim}$ 0.1
Authors: matsui Kana , sorai Kazuo , watanabe Yoshimasa , kuno Nario
Published: March 2014

We present the results of CO ($J$$=$ 1–0) observations toward nine barred spiral galaxies at z$=$ 0.08–0.25 using the 45 m telescope at Nobeyama Radio Observatory. This survey is the first one specializing in barred spiral galaxies in this redshift range. We detected CO emission in six galaxies out of nine, whose CO luminosities ($L_{\rm {CO}}'$) ranged (1.09–10.8) $\times$ 10$^{9}$ K km s$^{-1}$ pc$^{2}$. These six are the infrared dimmest galaxies that have ever been detected in CO at z$\sim$ 0.1 to date. They follow the $L_{\rm {CO}}'$–$L_{\rm {IR}}$ (IR luminosity) relation among such galaxies as local spiral galaxies, luminous infrared galaxies, ultra-luminous infrared galaxies, and submillimeter galaxies. Their $L_{\rm {CO}}'$ and $L_{\rm {IR}}$ are higher than those of local spiral galaxies, which have been detected in CO so far; $L_{\rm {IR}}/L'_{\rm {CO}}$, which is a measure of the star-formation efficiency, is comparable to, or slightly higher than, that of local ones. This result suggests that these six galaxies are forming stars more actively than local spiral galaxies simply because they have more fuel.
Star Formation and AGN Activity in Galaxies Classified Using the 1.6 μm Bump and PAH Features at z = 0.4–2
Authors: Hanami Hitoshi , Ishigaki Tsuyoshi , Fujishiro Naofumi , Nakanishi Kouichiro , Miyaji Takamitsu , Krumpe Mirko , Umetsu Keiichi , Ohyama Youichi , Shim Hyunjin , Im Myungshin , Lee Hyoung Mok , Lee Myung Gyoon , Serjeant Stephen , White Glenn J. , Willmer Christopher N. , Goto Tomotsugu , Oyabu Shinki , Takagi Toshinobu , Wada Takehiko , Matsuhara Hideo
Published: March 2014

We studied the star-formation and AGN activity of massive galaxies in the redshift range $ z$  $ =$ 0.4–2, which were detected in a deep survey field using the AKARI InfraRed (IR) astronomical satellite and Subaru telescope toward the North Ecliptic Pole (NEP). The AKARI/IRC Mid-InfraRed (MIR) multiband photometry was used to trace the star-forming activities with Polycyclic Aromatic Hydrocarbon (PAH) emission, which is effective not only to distinguish between star-forming and AGN galaxies, but also to estimate the Star Formation Rate (SFR) with converting its flux to the total emitting IR (TIR) luminosity. In combination with the analyses of the stellar components, we studied the MIR SED features of star-forming and AGN-harboring galaxies, which we summarize below: (1) The rest-frame 7.7-$ \mu $ m and 5-$ \mu $ m luminosities are good tracers of star-forming and AGN activities from their PAH and dusty tori emissions, respectively. (2) For dusty star-forming galaxies without AGN, their SFR shows a correlation that is nearly proportional to their stellar mass, and their specific SFR (sSFR) per unit stellar mass increases with redshift. Extinctions estimated from their TIR luminosities are larger than those from their optical SED fittings, which may be caused by geometric variations of dust in them. (3) Even for dusty star-forming galaxies with AGN, SFRs can be derived from their TIR luminosities with subtraction of the obscured AGN contribution, which indicates that their SFRs were possibly quenched around $ z$  $ \simeq$ 0.8 compared with those without AGN. (4) The AGN activity from their rest-frame 5-$ \mu $ m luminosity suggests that their Super Massive Black Holes (SMBHs) could already have grown to $ \simeq$ 3 $ \times$ 10$ ^{8}$  $ M_{\odot}$ in most massive galaxies with 10$ ^{11}$  $ M_{\odot}$ at $ z$  $ \lt$ 1.2, and the mass relation between SMBHs and their host galaxies has already become established by $ z$  $ \simeq$ 1–2.
Early Evolution of Spherical Ejecta Expanding into the Circumstellar Matter at Ultra-Relativistic Speeds
Authors: Shigeyama Toshikazu , Suzuki Akihiro , Nakamura Ko
Published: March 2014

We present a new self-similar solution describing the early evolution of an ultra-relativistic flow resulting from a collision of homologously expanding spherical ejecta with the circumstellar matter, in which a shock wave propagates in the circumstellar matter, while a weak discontinuity propagates in the ejecta at the sound speed.
Suzaku X-Ray Observation of the Dwarf Nova Z Camelopardalis at the Onset of an Optical Outburst
Authors: Saitou Kei , Tsujimoto Masahiro , Ebisawa Ken , Ishida Manabu
Published: March 2014

We present the result of a Suzaku X-ray spectroscopic observation of the dwarf nova Z Cam, which was conducted by chance at the onset of an optical outburst. We used the X-ray Imaging Spectrometer (a 38 ks exposure) and the Hard X-ray Detector (34 ks) to obtain a 0.35–40 keV spectrum simultaneously. Spectral characteristics suggest that the source was in the X-ray quiescent state, despite being in the rising phase of an outburst in the optical band. The spectrum shows a clear signature of circumstellar absorption in excess of interstellar absorption and the reprocessed-emission features of Fe fluorescence and Compton scattering. The extra absorption is explained as being due to partial covering by either neutral or ionized matter. We found a spectral change during the observation, which is attributable only to a change in the circumstellar absorption. Such an X-ray spectral variation was reported for the first time in the case of dwarf novae. We speculate that the variation in the circumstellar absorption is interpreted as a time-varying disk wind, or geometrically flaring disk around the white dwarf during the propagation of a heat wave along inward the accretion disk at the beginning of the outburst, in which optical outburst and X-ray quiescent states co-exist.
Fragmentation of Primordial Filamentary Clouds under Far-Ultraviolet Radiation
Authors: Bessho Shinji , Tsuribe Toru
Published: March 2014

The collapse and fragmentation of uniform filamentary clouds under isotropic far-ultraviolet external radiation are investigated. Especially, the impact of the photodissociation of hydrogen molecules during collapse is considered. The dynamical and thermal evolutions of collapsing filamentary clouds are calculated by solving the virial equation and the energy equation while taking into account non-equilibrium chemical reactions. It is found that thermal evolution is hardly affected by external radiation if the initial density is high ($ n_0$$ \gt$ 10$ ^{2}$ cm$ ^{-3}$ ). On the other hand, if the line mass of the filamentary cloud is moderate and the initial density is low ($ n_0$$ \le$ 10$ ^{2}$ cm$ ^{-3}$ ), the thermal evolution of the filamentary cloud tends to be adiabatic, owing to the effect of external dissociation radiation. In this case, the collapse of the filamentary cloud is suppressed, and the filamentary cloud fragments into very massive clouds ($ \sim$ 10$ ^{4-5}\ M_\odot$ ) in the early stage of collapse. The analytic criterion for the filamentary clouds to fragment into such massive clouds is discussed. We also investigate the collapse and fragmentation of the filamentary clouds with an improved model. This model can partly capture the effect of run-away collapse. Also, in this model filamentary clouds with low initial density ($ n_0$$ \le$ 10$ ^{2}$ cm$ ^{-3}$ ) fragment into massive clouds ($ \sim$ 10$ ^{4}\ M_\odot$ ) owing to the effect of external radiation.
Near-Infrared Imaging Polarization Study of M 17
Authors: Chen Zhiwei , Jiang Zhibo , Wang Yuan , Chini Rolf , Tamura Motohide , Nagayama Takahiro , Nagata Tetsuya , Nakajima Yasushi
Published: March 2014

We conducted wide-field ($ \sim$ 8$ '$$ \times$ 8$ '$ ) $ \textit{JHK}_{\rm s}$ imaging polarimetric observations toward the massive star-formation region M 17. The southern H II bar is identified as large-scale infrared reflection nebula (IRN) illuminated by OB stars in the cluster center, while the northern bar shows polarization originating from dichroic extinction. Three small-scale bipolar IRN with centro-symmetric polarization patterns were identified, and their illuminating sources, embedded young stellar objects (YSOs), are most likely the driving sources of bipolar outflows. $ \textit{JHK}_{\rm s}$ polarizations of point sources in M 17 show a wavelength dependence of the polarization of dichroic extinction in the general interstellar medium, indicating $ \alpha$$ \sim$ 1.8 for the empirical relation $ P$$ \propto$$ \lambda^{-\alpha}$ of interstellar polarization. The distribution of the polarization angle shows two peaks at 170$ ^{\circ}$ and 110$ ^{\circ}$ , indicating a non-uniform magnetic field structure in M 17. The direction of the magnetic field in the cluster region is south-north. However, the magnetic field in the H II region is roughly between 100$ ^{\circ}$ –140$ ^{\circ}$ , roughly perpendicular to the Galactic disk. Such a configuration indicates that the magnetic field in the cluster region is twisted from the primordial orientation in the cluster formation. The magnetic field in the southern bar has a total strength of $ \sim$ 230$ \ \mu$ G, and is 40$ ^{\circ}$ inclined to the plane of the sky. The outflows driven by YSOs in M 17 show a poor relation with the surrounding magnetic fields. This fact implies that the magnetic field in M 17 does not dominate the orientations of protostars formed inside.
Conditions of Gravitational Instability in Protoplanetary Disks
Authors: Kimura Shigeo S. , Tsuribe Toru
Published: March 2014

Gravitational instability is one of the considerable mechanisms to explain the formation of giant planets. We have studied the gravitational stability in protoplanetary disks around a protostar. The temperature and Toomre's $ Q$ value were calculated by assuming local equilibrium between viscous heating and radiative cooling (local thermal equilibrium). We assumed a constant $ \alpha$ viscosity and used a cooling function with realistic opacity. Then, we derived the critical surface density, $ \Sigma_{\rm {c}}$ , that is needed in order for a disk to become gravitationally unstable as a function of $ r$ . This critical surface density, $ \Sigma _{\rm c}$ , is strongly affected by the temperature dependence of the opacity. At a radius of $ r_{\rm c}$$ \sim$ 20 AU, where ices form, the value of $ \Sigma _{\rm c}$ changes discontinuously by one order of magnitude. This $ \Sigma _{\rm c}$ is determined only by a local thermal process and the criterion of gravitational instability. By comparing a given surface density profile with $ \Sigma _{\rm c}$ , one can discuss the gravitational instability of protoplanetary disks. As an example, we discuss the gravitational instability of two semianalytic models for protoplanetary disks. One is a steady state accretion disk, which is realized after viscous evolution. The other is a disk that has the same angular-momentum distribution as its parent cloud core, which corresponds to the disk that has just formed. As a result, it is found that the disk tends to become gravitationally unstable for $ r$$ \ge$$ r_{\rm c}$ because ices make the disk temperature low. In a region closer to the protostar than $ r_{\rm c}$ , it is difficult for a typical protoplanetary disk to fragment because of the high temperature and the large Coriolis force. Based on this result, we conclude that fragmentation near the central star is possible, but difficult.
Optimization by Smoothed Bandpass Calibration in Radio Spectroscopy
Authors: Yamaki Haruka , Kameno Seiji , Beppu Hirohisa , Mizuno Izumi , Imai Hiroshi
Published: March 2014

We have developed the Smoothed Bandpass Calibration (SBC) method and the best suitable scan pattern to optimize radio spectroscopic observations. Adequate spectral smoothing is applied to the spectrum toward OFF-source blank sky adjacent to a target source for the purpose of bandpass correction. Because the smoothing process reduces noise, we can reduce the integration time for OFF-source scans while keeping the signal-to-noise ratio. Since smoothing is not applied to ON-source scans, the spectral resolution for line features is maintained. An optimal smoothing window is determined by the bandpass flatness evaluated by the spectral Allan variance (SAV). An efficient scan pattern is designed for OFF-source scans within the bandpass-stability time scale estimated by the time-based Allan variance (TAV). We tested the SBC using a digital spectrometer, VESPA, at the VERA Iriki station. For a targeted noise level of 5 $ \times$10$ ^{-4}$ as its ratio to the system noise, the optimal smoothing window was 32–60 channels (ch) over the whole bandwidth of 1024 ch, and the optimal scan pattern was designed as a sequence of 70 s ON $ +$ 10 s OFF scan pairs. The noise level by the SBC has been improved by a factor of 1.74, compared with that by the conventional method. The total telescope-time to reach our target with the SBC was 400 s, which is 1$ /$ 3 of 1200 s required in the conventional way. Improvements in the telescope-time efficiency with the SBC were calculated to be 3$ \times$ (for single-beam scans), 2$ \times$ (dual-beam), and 1.3$ \times$ (on-the-fly). The SBC is useful for optimizing scan patterns for observations from now on, and also for improving the signal-to-noise ratios of archival data if ON- and OFF-source spectra are separately recorded, though the efficiency depends on the spectral stability of the receiving system.
Chromospheric Running Wave from a Solar Cyclone Produced through the Emergence of a Twisted Magnetic Flux Tube
Authors: Magara Tetsuya , An Jun-Mo , Lee Hwanhee , Kang Jihye , Inoue Satoshi , Choe Gwangson
Published: March 2014

An innovative solar observing satellite, Hinode, has successfully observed the detailed evolution of an emerging magnetic field, starting from its appearance at the solar surface, to forming a developed bipolar region. The high spatial and temporal resolutions provided by the satellite has enabled us to capture prominent dynamic phenomena caused by the emerging magnetic field, such as a running wave in a chromospheric layer and the rotation of a magnetic polarity region on the Sun, which is reminiscent of a cyclone on Earth. A possible mechanism for producing the chromospheric running wave spreading from a solar cyclone has been demonstrated with a three-dimensional magnetohydrodynamic simulation for the emergence of a twisted flux tube. The simulation shows that as the emergence proceeds, an arc-shaped region with enhanced plasma density propagates outwards from the site of emergence.
Orbital Period Investigation of the RS CVn-Type Binary CG Cygni
Authors: Shi Xiao-Min , Xiang Fu-Yuan , Lu Ye
Published: March 2014

We collected all minima times of the RS CVn-type binary CG Cyg that we were able to find in the literature and databases. The orbital period variations of the system were examined by analyzing its $ O$$-$$ C$ curves (1) through the weighted least-squares method, and (2) through the first continuous method. It was found that the results obtained from the two methods are different. We compared our results with the former author's work, and drew the orbital-period variation of CG Cyg, which indicates that it undergoes a long-term period increase at a rate of $ dP/dt$$ =$$ +$ 2.48 $ \times$ 10$ ^{-8}$ d yr$ ^{-1}$ . We discuss the implications of the result regarding the link between the orbital-period variation and the mass transfer of the system.
Nonlinear Behaviors of Pulsating Stars with Convective Zones
Authors: Tanaka Yasuo , Saha Lal M.
Published: March 2014

We discuss the role of convective zones in the treatment of coupled pulsation and convection. In particular, we have investigated behaviors of the convective depth, $ \eta$ , and of the ratio between the convective and total luminosities, $ \gamma_{\rm c}$ . In deep convection, additional fixed points appear, the values of which increase with the depth of zone, and become larger than unity. A diagram of stability criteria derived from the linearized model has been drawn, which shows stable regions fitting each criterion. Then, various flow patterns have been obtained by means of numerical simulations for sets of $ \gamma_{\mathrm{c}}$ and $ \eta$ , and the structure of the mode has been discussed. The results of simulations are shown in tables and figures with a fixed set of parameters other than the set of $ \gamma_{\mathrm{c}}$ and $ \eta$ , which show that deep convective zones cause chaotic solutions and long-period oscillations. Some suggestions are made based on these findings in stellar pulsation within the convective zone.
The Light and Period Variations of the Eclipsing Binary BX Draconis
Authors: Park Jang-Ho , Lee Jae Woo , Kim Seung-Lee , Lee Chung-Uk , Jeon Young-Beom
Published: March 2014

New CCD photometric observations of BX Dra were carried out on 26 nights during the period from 2009 April to 2010 June. The long-term photometric behaviors of the system are obtained from detailed studies of the period and light variations, based on historical data and our new observations. All available light curves display total eclipses at secondary minima and inverse O'Connell effects with Max I fainter than Max II, which were satisfactorily modeled by adding a slightly time-varying hot spot on the primary star. A total of 87 times of minimum lights spanning over $ \sim$ 74 yr, including our 22 timing measurements, were used for ephemeris computations. A detailed analysis of the $ O$$-$$ C$ diagram disclosed that the orbital period shows an upward parabola in combination with a sinusoidal variation. The continuous increase of period at a rate of $ +$ 5.65 $ \times$ 10$ ^{-7}$ d yr$ ^{-1}$ is consistent with that calculated from the Wilson–Devinney synthesis code. It can be interpreted as a mass transfer from the secondary star to the primary at a rate of 2.74 $ \times$ 10$ ^{-7}$$ M_{\odot}$ yr$ ^{-1}$ , which is one of the largest rates between components of the contact system. The most likely explanation of the sinusoidal variation having a period of 30.2 yr and a semiamplitude of 0.0062 d is a light-travel-time effect due to the existence of a circumbinary object. We suggest that BX Dra is probably a triple system, consisting of a primary star with a spectral type of F0, its secondary component of spectral type F1–2, and an unseen circumbinary object with a minimum mass of $ M_3$$ =$ 0.23 $ M_{\odot}$.
Collapse of Primordial Filamentary Clouds under Far-Ultraviolet Radiation
Authors: Bessho Shinji , Tsuribe Toru
Published: March 2014

The collapse and fragmentation of primordial filamentary clouds under isotropic dissociation radiation was investigated with one-dimensional hydrodynamical calculations. We investigate the effect of the dissociation photon on the filamentary clouds by calculating non-equilibrium chemical reactions. With the external radiation assumed to turn on when the filamentary cloud forms, a filamentary cloud with low initial density ($n_0$$\le$ 10$^{2}\ $ cm$^{-3}$ ) suffers a photodissociation of hydrogen molecules. In such a case, since the main coolant is lost, the temperature increases adiabatically enough to suppress the collapse. As a result, the filamentary cloud fragments into very massive clouds ($\sim$ 10$^{5}\ M_\odot$ ). On the other hand, the evolution of the filamentary clouds with high initial density ($n_0$$>$ 10$^{2}\ $ cm$^{-3}$ ) is hardly affected by the external radiation. This is because the filamentary cloud with high initial density shields itself from the external radiation. It is found that the fragment mass increases owing to the external radiation. This result is consistent with previous results with one-zone models. It is also found that the fragment mass decreases owing to the external dissociation radiation in the case with a sufficiently large line mass.
A New Galactic Extinction Map in High Ecliptic Latitudes
Authors: Kohyama Tsunehito , Shibai Hiroshi , Fukagawa Misato , Sumi Takahiro , Hibi Yasunori
Published: March 2014

In this study, we derived a galactic extinction map in high ecliptic latitudes for $ \mid{\beta}\mid$$ >$ 30$ ^\circ$ . The dust temperature distribution was derived from the intensities at 100 and 140 $ \mu$ m with a spatial resolution of 5$ '$ . The intensity at 140 $ \mu$ m was derived from the intensities at 60 and 100 $ \mu$ m of the IRAS data, assuming two tight correlations between the intensities at 60, 100, and 140 $ \mu$ m of the COBE/DIRBE data. We found that these correlations can be separated into two correlations by the antenna temperature of the radio continuum at 41 GHz. Because the present study can trace the 5$ '$-scale spatial variation in the dust temperature distribution, it has an advantage over the extinction map derived by Schlegel, Finkbeiner, and Davis (1998, ApJ, 500, 525), who used the DIRBE maps to derive the dust temperature distribution with a spatial resolution of 1$ ^\circ$ . We estimated the accuracy of our method by comparing it with that of Schlegel, Finkbeiner, and Davis (1998, ApJ, 500, 525). The spatial-resolution difference was found to be significant. The area in which the significant difference is confirmed occupies 28% of the region for $ \mid{\beta}\mid$$ >$ 30$ ^\circ$ . With respect to the estimated extragalactic reddening, the present study has an advantage over the extinction map derived by Dobashi (2011, PASJ, 63, 1), which was based on the 2MASS Point Source Catalog, because our extinction map was derived based on far-infrared emission. Dobashi's extinction map exhibits a maximum value that is lower than that of our map in the galactic plane, and a signal-to-noise ratio that is lower than that of our map in high galactic latitudes. This significant difference is confirmed in 81% of the region for $ \mid{\beta}\mid$$ >$ 30$ ^\circ$ . In the areas where the significant differences are confirmed, the extinction should be estimated using our method, rather than the previous methods.
Properties of Molecular Gas in Galaxies in Early and Mid Stages of the Interaction. I. Distribution of Molecular Gas
Authors: Kaneko Hiroyuki , Kuno Nario , Iono Daisuke , Tamura Yoichi , Tosaki Tomoka , Nakanishi Koichiro , Sawada Tsuyoshi
Published: March 2014

We present the results of $ ^{12}$ CO (J$ =$ 1–0) mapping observations toward four interacting galaxies in early and mid stages of the interaction in order to understand the behavior of molecular gas in galaxy–galaxy interactions. The observations were carried out using the 45-m telescope at Nobeyama Radio Observatory (NRO). We compared our CO total flux to those previously obtained with single-dish observations, and found that there is no discrepancy between them. By applying a typical CO–H$ _{2}$ conversion factor, it was found that all constituent galaxies have molecular gas mass of more than 10$ ^{9}$ . Comparisons to H I, K$ _{\rm s}$, and tracers of star formation, such as H$ \alpha$ , FUV, 8 $ \mu$ m, and 24 $ \mu$ m, revealed that the distribution of molecular gas in interacting galaxies in the early stage of the interaction differs from atomic gas, stars, and star-forming regions. These differences can not be explained without the result of the interaction. The central concentration of molecular gas of interacting galaxies in the early stage of the interaction is lower than that of isolated galaxies, which suggests that molecular gas is distributed off-centre, and/or extends in the beginning of the interaction.
Measurements of an Antenna Surface for a Millimeter-Wave Space Radio Telescope. II. Metal Mesh Surface for Large Deployable Reflector
Authors: Kamegai Kazuhisa , Tsuboi Masato
Published: March 2014

Large deployable antennas with a mesh surface woven by fine metal wires are an important technology for communications satellites and space radio telescopes. However, it is difficult to make metal mesh surfaces with sufficient radio-frequency (RF) performance for frequencies higher than millimeter waves. In this paper, we present the RF performance of metal mesh surfaces at 43 GHz. For this purpose, we developed an apparatus to measure the reflection coefficient, transmission coefficient, and radiative coefficient of the mesh surface. The reflection coefficient increases as a function of the metal mesh surface tension, whereas the radiative coefficient decreases. The anisotropic aspects of the reflection coefficient and the radiative coefficient are also clearly seen. They depend on the front and back sides of the metal mesh surface and the rotation angle. The transmission coefficient was measured to be almost constant. The measured radiative coefficients and transmission coefficients would cause significant degradation of the system noise temperature. In addition, we carried out an astronomical observation of a well-known SiO maser source, R Cas, by using a metal mesh mirror on the NRO 45-m radio telescope Coudé system. The metal mesh mirror considerably increases the system noise temperature, and slightly decreases the peak antenna temperature. These results are consistent with laboratory measurements.
The Nature of Stable Soft X-Ray Emissions in Several Types of Active Galactic Nuclei Observed by Suzaku
Authors: Noda Hirofumi , Makishima Kazuo , Nakazawa Kazuhiro , Uchiyama Hideki , Yamada Shin'ya , Sakurai Soki
Published: March 2014

To constrain the origin of the soft X-ray excess phenomenon seen in many active galactic nuclei, the intensity-correlated spectral analysis, developed by Noda et al. (2011, PASJ, 63, S925) for Markarian 509, was applied to wide-band (0.5–45 keV) Suzaku data of five representative objects with a relatively weak reflection signature. They are the typical bare-nucleus type 1 Seyfert Fairall 9, the bright and typical type 1.5 Seyfert MCG $-$ 2–58–22, 3C 382, which is one of the X-ray brightest broad line radio galaxies, the typical Seyfert-like radio loud quasar 4C $ +$ 74.26, and the X-ray brightest radio quiet quasar MR 2251$-$ 178. In all of them, soft X-ray intensities in energies below 3 keV were tightly correlated with that in 3–10 keV, but with significant positive offsets. These offsets, when calculated in finer energy bands, define a stable soft component in 0.5–3 keV. In each object, this component successfully explained the soft excess above a power-law fit. These components were interpreted in several alternative ways, including a thermal Comptonization component that is independent of the dominant power-law emission. This interpretation, considered physically most reasonable, is discussed from a viewpoint of Multi-Zone Comptonization, which was proposed for the black hole binary Cygnus X-1 (Makishima et al. 2008, PASJ, 60, 585).
X-Ray and Optical Monitoring of a Gamma-Ray-Emitting Radio Galaxy, NGC 1275
Authors: Yamazaki Syoko , Fukazawa Yasushi , Sasada Mahito , Itoh Ryosuke , Nishino Sho , Takahashi Hiromitsu , Takaki Katsutoshi , Kawabata Koji S. , Yoshida Michitoshi , Uemura Makoto
Published: March 2014

We performed monitoring observations of a gamma-ray-emitting radio galaxy, NGC 1275, in the X-ray and optical bands with the Suzaku/XIS, Kanata telescope, and the Okayama telescope. The X-ray flux of the nucleus was estimated by imaging spectroscopy in the hard X-ray band. In the optical band, a continuum flux, a broad H$ \alpha$ line flux, and the polarization degree were measured. We could not find any time variability of the X-ray (2006–2011) and optical continuum (2010–2011) within 30%, regardless of the recent radio and gamma-ray variability by a factor of 3. The observed optical polarization was very small at $ \sim$ 0.4% and showed little variability; it would be mostly of interstellar origin within our Galaxy. Furthermore, we confirmed with the XMM-Newton data that the X-ray spectrum of NGC 1275 in 2006 exhibited the Fe-K line, whose equivalent width was typical for other radio and Seyfert galaxies. These results indicate that the jet emission is not a major component in the optical and X-ray bands. Following these results, we discuss the jet emission of NGC 1275.