bluuebunny/crossref_metadata_2025_split huggingface dataset:
NRO M 33 All-Disk Survey of Giant Molecular Clouds (NRO MAGiC). I. H I to H2 Transition
Authors: Tosaki Tomoka , Kuno Nario , Onodera Sachiko , Miura Rie , Sawada Tsuyoshi , Muraoka Kazuyuki , Nakanishi Kouichiro , Komugi Shinya , Nakanishi Hiroyuki , Kaneko Hiroyuki , Hirota Akihiko , Kohno Kotaro , Kawabe Ryohei 
Published: March 2014

Abstract
We present the results of the Nobeyama Radio Observatory (NRO) M 33 All-Disk (30$'$ $\times$ 30$'$ or 7.3 kpc $\times$ 7.3 kpc) Survey of Giant Molecular Clouds (NRO MAGiC) based on $^{12}$CO ($J$ $=$ 1–0) observations using the NRO 45 m telescope. The spatial resolution of the resultant map is 19$''\!\!\!.$3, corresponding to 81 pc, which is sufficient to identify each Giant Molecular Cloud (GMC) in the disk. We found clumpy structures with a typical spatial scale of $\sim\ $100 pc, corresponding to GMCs, and no diffuse, smoothly distributed component of molecular gas at this sensitivity. The overall distribution of molecular gas roughly agrees with that of H I. However, a closer inspection of the CO and H I maps suggests that not every CO emission is associated with local H I peaks, particularly in the inner portion of the disk ($r \lt$ 2 kpc), although most of the CO emission is located at the local H I peaks in the outer radii. We found that most uncovered GMCs are accompanied by massive star-forming regions, although the star-formation rates (SFRs) vary widely from cloud to cloud. The surface density of the azimuthally averaged H I gas exhibits a flat radial distribution. However, the CO radial distribution shows a significant enhancement within the central 1–2 kpc region, which is very similar to that of the SFR. We obtained a map of the molecular fraction, $f_{\rm mol}$ $=$ $\Sigma_{\rm H_2}/$($\Sigma_{\rm H~{ I}}$ $+$ $\Sigma_{\rm H_2}$), with a resolution of 100 pc. This is the first $f_{\rm mol}$ map covering an entire galaxy with a GMC-scale resolution. We found that $f_{\rm mol}$ tends to be high near the center. The correlation between $f_{\rm mol}$ and gas surface density shows two distinct sequences. The presence of two correlation sequences can be explained by a difference of metallicity; i.e., higher ($\sim\ $ 2-fold) metallicity in the central region ($r$ $\lt$ 1.5 kpc) than in the outer parts. Alternatively, difference in the scale height can also account for the two sequences; i.e., the scale height increases at the outer disk.
Stochastic Acceleration of Cosmic Rays in the Central Molecular Zone of the Galaxy
Authors: Amano Takanobu , Torii Kazufumi , Hayakawa Takahiro , Fukui Yasuo 
Published: March 2014

Abstract
Particle acceleration in the inner $\sim $200 pc of the Galaxy is discussed, where diffuse TeV $\gamma$-rays have been detected by High Energy Stereoscopic System observations. Diffuse $\gamma$-ray emission has a strong correlation with molecular clouds with large velocity dispersion, indicating the presence of turbulence. It is argued that turbulence may contribute to the acceleration of cosmic rays via stochastic acceleration. Stochastic acceleration may energize cosmic-ray protons up to $\sim $100 TeV and electrons to $\sim $1 TeV in a relatively tenuous medium. The difference in the efficiency between protons and electrons supports the hadronic scenario of diffuse TeV $\gamma$-ray emission.
Discovery of Gas Bulk Motion in the Galaxy Cluster Abell 2256 with Suzaku
Authors: Tamura Takayuki , Hayashida Kiyoshi , Ueda Shutaro , Nagai Masaaki 
Published: March 2014

Abstract
The results from Suzaku observations of the galaxy cluster Abell 2256 are presented. This cluster is a prototypical and well-studied merging system, exhibiting substructures both in the X-ray surface brightness and in the radial velocity distribution of member galaxies. There are main and sub components separated by 3 $'\!\!.$ 5 in the sky and by about 2000 km s $^{-1}$ in radial-velocity peaks of the member galaxies. In order to measure the Doppler shifts of iron K-shell lines from the two gas components by the Suzaku XIS, the energy scale of the instrument was carefully evaluated and found to be calibrated well. A significant shift of the radial velocity of the sub component gas with respect to that of the main cluster was detected. All three XIS sensors show the shift independently and consistently among the three. The difference is found to be 1500 $\ \pm\ $ 300 (statistical) $\ \pm\ $ 300 (systematic) km s $^{-1}$ . The X-ray determined absolute redshifts of, and hence the difference between, the main and sub components are consistent with those of member galaxies in the optical band. The observation indicates robustly that the X-ray emitting gas is moving together with galaxies as a substructure within the cluster. These results along with other X-ray observations of gas bulk motions in merging clusters are discussed.
Peculiarly Narrow SED of GRB 090926B with MAXI and Fermi/GBM
Authors: Serino Motoko , Yoshida Atsumasa , Kawai Nobuyuki , Nakagawa Yujin E. , Mihara Tatehiro , Ueda Yoshihiro , Nakahira Satoshi , Eguchi Satoshi , Hiroi Kazuo , Ishikawa Masaki , Isobe Naoki , Kimura Masashi , Kitayama Hiroki , Kohama Mitsuhiro , Matsumura Takanori , Matsuoka Masaru , Morii Mikio , Nakajima Motoki , Negoro Hitoshi , Shidatsu Megumi , Sootome Tetsuya , Sugimori Kousuke , Sugizaki Mutsumi , Suwa Fumitoshi , Toizumi Takahiro , Tomida Hiroshi , Tsuboi Yohko , Tsunemi Hiroshi , Ueno Shiro , Usui Ryuichi , Yamamoto Takayuki , Yamaoka Kazutaka , Yamauchi Makoto , Yamazaki Kyohei 
Published: March 2014

Abstract
The monitor of the all-sky X-ray image (MAXI) Gas Slit Camera (GSC) on the International Space Station (ISS) detected a gamma-ray burst (GRB) on 2009, September 26, GRB 090926B. This GRB had extremely hard spectra in the X-ray energy range. Joint spectral fitting with the Gamma-ray Burst Monitor on the Fermi Gamma-ray Space Telescope shows that this burst had a peculiarly narrow spectral energy distribution, which can be represented by a Comptonized blackbody model. This spectrum can be interpreted as photospheric emission from a low baryon-load GRB fireball. Calculating the parameter of the fireball, we found the size of the base of the flow to be $r_0$$=$ (4.3 $\ \pm\ $ 0.9) $\times$ 10 $^{9}\ Y'^{-3/2}\ $ cm, the Lorentz factor of the plasma is $\Gamma$$=$ (110 $\ \pm\ $ 10) $\ Y'^{\ 1/4}$ , where $Y'$ is a ratio between the total fireball energy and the energy in the blackbody component of the gamma-ray emission. This $r_0$ is a factor of a few times larger, and the Lorentz factor of 110 is smaller by also factor of a few than other bursts that have blackbody components in the spectra.
Cross Spectral Calibration of Suzaku, XMM-Newton, and Chandra with PKS 2155304 as an Activity of IACHEC
Authors: Ishida Manabu , Tsujimoto Masahiro , Kohmura Takayoshi , Stuhlinger Martin , Smith Michael , Marshall Herman L. , Guainazzi Matteo , Kawai Kohei , Ogawa Taiki 
Published: March 2014

Abstract
We report on comparisons of the energy responses of the Suzaku XIS, the Chandra HRC and ACIS with the LETG, and the XMM-Newton MOS and pn using simultaneous data of the BL Lac object PKS 2155 $-$ 304 taken in 2005, 2006, and 2008. From power-law fits to individual spectra, we have found that the photon index agrees among all instruments within $\simeq\ $ 0.1, and that the resultant hydrogen column density values of the Chandra and XMM-Newton instruments differ from the value for PKS 2155 $-$ 304 only by $\lesssim\ $ 1 $\times$ 10 $^{20}\ $ cm $^{-2}$ , while that of Suzaku bears a larger systematic error of 4 $\times$ 10 $^{20}\ $ cm $^{-2}$ , at most. We have carried out flux cross-calibration in seven small segments of energy bands between 0.5 keV and 10 keV. In the bands above 2 keV, the Suzaku fluxes are larger than those of XMM-Newton by $\simeq\ $ 20%, $\simeq\ $ 10%, and $\lesssim\ $ 5% in 2005, 2006, and 2008, respectively, although the 20% difference in 2005 is still preliminary. The fluxes of the LETG $+$ HRC in 2006 coincide with those of Suzaku below 2 keV. The fluxes of the LETG $+$ ACIS are compared with those of Suzaku and XMM-Newton with the 2008 data, and are systematically larger than those of Suzaku and XMM-Newton by 10%. These results are in general consistent with those presented in one of the precedent papers from International Astronomical Consortium for High Energy Calibration (IACHEC) using G21.5 $-$ 0.9.
A New X-Ray Spectro-Temporal Analysis Method and Its Application to the Suzaku MCG −6–30–15 Data
Authors: Inoue Hajime , Miyakawa Takehiro , Ebisawa Ken 
Published: March 2014

Abstract
A new X-ray spectro-temporal data-analysis method, which we call “the difference variation function method”, is introduced. It can analyze spectral and temporal variations of X-ray sources, and its merits are discussed in comparison with conventional data-analysis methods. The new method is being applied to Suzaku observation data of the Seyfert 1 galaxy MCG $-$ 6–30–15. Consequently, it has been found that the observed spectral and temporal variations on a time scale of $\approx$ 10–100 ks are mostly ascribed to variable partially absorbers in front of the central X-ray source, whereas the X-ray source is intrinsically variable mainly on time scales shorter than $\approx$ 10 ks.
Observation of the Cygnus OB2 Association with Suzaku and Long-Term Light Curves
Authors: Yoshida Masaki , Kitamoto Shunji , Murakami Hiroshi 
Published: March 2014

Abstract
We obtained a Suzaku 41-ks observation of the four brightest early type stars in the Cygnus OB2 association (Cyg OB2 Nos. 5, 8a, 9, and 12). The spectra of two of the stars, Nos. 9 and 12, could be fitted by a two-temperature thin-thermal collisional-ionization equilibrium model, while those of Nos. 5 and 8a required a three-temperature model. Star No. 8a showed a time variation both above 3 keV and below 1.5 keV. The time scale of the variation of the soft X-rays is $\sim$ 8 $\times$ 10 $^{4}$ s, while that above 3 keV is $\sim$ 2 $\times$ 10 $^{4}$ s. We found that the variation above 3 keV can be explained by temperature changes in the hottest plasma of the three-temperature model. This result restricts the size and density of the hottest component of the three-temperature model. We also produced long-term light curves of the four stars for over 30 yr. We confirmed the orbital modulation in the intensity of No. 8a, and discovered a possible orbital modulation of 2.35 yr in the light curve of No. 9.
Discovery of a Cyclotron Resonance Feature in the X-Ray Spectrum of GX 304−1 with RXTE and Suzaku during Outbursts Detected by MAXI in 2010
Authors: Yamamoto Takayuki , Sugizaki Mutsumi , Mihara Tatehiro , Nakajima Motoki , Yamaoka Kazutaka , Matsuoka Masaru , Morii Mikio , Makishima Kazuo 
Published: March 2014

Abstract
We report on the discovery of a cyclotron resonance scattering feature (CRSF) in the X-ray spectrum of GX 304 $-$ 1, obtained by RXTE and Suzaku during major outbursts detected by MAXI in 2010. The peak intensity in August reached 600 mCrab in the 2–20 keV band, which is the highest ever observed from this source. The RXTE observations on more than twenty occasions and one Suzaku observation revealed a spectral absorption feature at around 54 keV, which is the first CRSF detection from this source. The estimated strength of the surface magnetic field, 4.7 $\times$ 10 $^{12}$ G, is one of the highest among binary X-ray pulsars from which CRSFs have ever been detected. The RXTE spectra taken during the August outburst also suggest that the CRSF energy changed over 50–54 keV, possibly in a positive correlation with the X-ray flux. The behavior is qualitatively similar to that observed from Her X-1 on long time scales, or from A 0535 $+$ 26, but different from the negative correlation observed from 4U 0115 $+$ 63 and X 0331 $+$ 53.
X-Ray and Near-Infrared Observations of GX 339−4 in the Low/Hard State with Suzaku and IRSF
Authors: Shidatsu Megumi , Ueda Yoshihiro , Tazaki Fumie , Yoshikawa Tatsuhito , Nagayama Takahiro , Nagata Tetsuya , Oi Nagisa , Yamaoka Kazutaka , Takahashi Hiromitsu , Kubota Aya , Cottam Jean , Remillard Ronald , Negoro Hitoshi 
Published: March 2014

X-ray and near-infrared ( $J$ – $H$ – $K_{\rm s}$ ) observations of the galactic black-hole binary GX 339 $-$ 4 in the low/hard state were performed with Suzaku and IRSF in 2009 March. The spectrum in the 0.5–300 keV band is dominated by thermal Comptonization of multicolor disk photons, with a small contribution from a direct disk component, indicating that the inner disk is almost fully covered by hot corona with an electron temperature of $\approx$ 175 keV. The Comptonizing corona has at least two optical depths, $\tau$ $\approx$ 1, 0.4. Analysis of the iron-K line profile yields an inner-disk radius of (13.3 $^{+6.4}_{-6.0}$ ) $\ R_{\rm g}$ ( $\ R_{\rm g}$ represents the gravitational radius $GM/c^2$ ), with the best-fit inclination angle of $\approx$ 50 $^\circ$ . This radius is consistent with that estimated from the continuum fit by assuming the conservation of photon numbers in Comptonization. Our results suggest that the standard disk of GX 339 $-$ 4 is likely truncated before reaching the innermost stable circular orbit (for a non-rotating black hole) in the low/hard states at $\sim\ $ 1% of the Eddington luminosity. The one-day averaged near-infrared light curves are found to be correlated with hard X-ray flux with $F_{\rm Ks}$ $\propto$ $F_{\rm X}^{0.45}$ . The flatter near-infrared $\nu F_{\nu}$ spectrum than the radio one suggests that the optically thin synchrotron radiation from the compact jets dominates the near-infrared flux. Based on a simple analysis, we estimate the magnetic field and size of the jet base to be 5 $\times$ 10 $^{4}\ $ G and 6 $\times$ 10 $^{8}\ $ cm, respectively. The synchrotron self Compton component is estimated to be approximately 0.4% of the total X-ray flux.
MAXI GSC Monitoring of the Crab Nebula and Pulsar during the GeV Gamma-Ray Flare in 2010 September
Authors: Morii Mikio , Sugizaki Mutsumi , Kawai Nobuyuki , Serino Motoko , Yamamoto Takayuki , Usui Ryuichi , Daikyuji Arata , Ebisawa Ken , Eguchi Satoshi , Hiroi Kazuo , Ishikawa Masaki , Isobe Naoki , Kawasaki Kazuyoshi , Kimura Masashi , Kitayama Hiroki , Kohama Mitsuhiro , Matsumura Takanori , Matsuoka Masaru , Mihara Tatehiro , Nakagawa Yujin E. , Nakahira Satoshi , Nakajima Motoki , Negoro Hitoshi , Ozawa Hiroshi , Shidatsu Megumi , Sootome Tetsuya , Sugimori Kousuke , Suwa Fumitoshi , Tomida Hiroshi , Tsuboi Yohko , Tsunemi Hiroshi , Ueda Yoshihiro , Ueno Shiro , Uzawa Akiko , Yamaoka Kazutaka , Yamazaki Kyohei , Yoshida Atsumasa 
Published: March 2014

Abstract
We report on the MAXI GSC X-ray monitoring of the Crab nebula and pulsar during the GeV gamma-ray flare for the period of 2010 September 18–24 (MJD 55457 $-$ 55463), detected by AGILE and Fermi-LAT. There were no significant variations on the pulse phase averaged and pulsed fluxes during the gamma-ray flare on time scales from 0.5 to 5 days. The pulse profile also showed no significant change during this period. The upper limits on the variations of the pulse phase averaged and pulsed fluxes for the period MJD 55457.5 $-$ 55462.5 in the 4–10 keV band were derived to be 1% and 19%, respectively, at the 90% confidence limit of the statistical uncertainty. The lack of variations in the pulsed component over the multi-wavelength range (radio, X-ray, hard X-ray, and gamma-ray) supports not a pulsar, but a nebular origin for the gamma-ray flare.
Suzaku Detection of Diffuse Hard X-Ray Emission outside Vela X
Authors: Katsuda Satoru , Mori Koji , Petre Robert , Yamaguchi Hiroya , Tsunemi Hiroshi , Bocchino Fabrizio , Bamba Aya , Miceli Marco , Hewitt John W. , Temim Tea , Uchida Hiroyuki , Yoshii Rie 
Published: March 2014

Abstract
Vela X is a large, 3 $^{\circ}$$\times$ 2 $^{\circ}$ , radio-emitting pulsar wind nebula (PWN) powered by the Vela pulsar in the Vela supernova remnant. Using four Suzaku/XIS observations pointed just outside Vela X, we have found hard X-ray emission extending throughout the fields of view. The hard X-ray spectra are well represented by a power-law. The photon index was measured to be constant at $\Gamma$$\sim$ 2.4, similar to that of the southern outer part of Vela X. The power-law flux decreases with increasing distance from the pulsar. These properties lead us to propose that the hard X-ray emission is associated with the Vela PWN. The larger X-ray extension found in this work strongly suggests that distinct populations of relativistic electrons form the X-ray PWN and Vela X, as was recently inferred from multiwavelength spectral modeling of Vela X.
No X-Ray Excess from the HESS J1741−302 Region, except for a New Intermediate Polar Candidate
Authors: Uchiyama Hideki , Koyama Katsuji , Matsumoto Hironori , Tibolla Omar , Kaufmann Sarah , Wagner Stefan 
Published: March 2014

Abstract
With the Suzaku satellite, we observed an unidentified TeV gamma-ray source, HESS J1741 $-$ 302, and its surroundings. No diffuse or point-like X-ray sources have been detected from the bright southern emission peak of HESS J1741 $-$ 302. From its neighborhood, we found a new intermediate polar candidate at the position of ( $\alpha$ , $\delta$ ) $_{\rm J2000.0}$$=$ (17 $^{\rm h}$ 40 $^{\rm m}$ 35 $.\!\!\!^{\rm s}$ 6, $-$ 30 $^\circ$ 14 $^{\rm m}$ 16 $^{\rm s}$ ), which is designated as Suzaku J174035.6 $-$ 301416. The spectrum of Suzaku J174035.6 $-$ 301416 exhibits emission lines at energy of 6.4, 6.7, and 7.0 keV, which can be assigned as the K $\alpha$ lines from neutral, He-like, and H-like iron, respectively. A coherent pulsation is found at a period of 432.1 $\ \pm\ $ 0.1 s. The pulse profile is quasi-sinusoidal in the hard X-ray band (4–8 keV), but is more complicated in the soft X-ray band (1–3 keV). The moderate period of pulsation, the energy flux, and the presence of the iron K $\alpha$ lines indicate that Suzaku J174035.6 $-$ 301416 is likely to be an intermediate polar, a subclass of magnetized white dwarf binaries (cataclysmic variables). Based on these discoveries, we give some implications on the origin of Galactic center diffuse X-ray emission and brief comments on HESS J1741 $-$ 302 and PSR B1737 $-$ 30.
Detection of X-Ray Emission from the Unidentified TeV Gamma-Ray Source TeV J2032+4130
Authors: Murakami Hiroshi , Kitamoto Shunji , Kawachi Akiko , Nakamori Takeshi 
Published: March 2014

Abstract
We observed the first unidentified TeV $\gamma$ -ray source TeV J2032 $+$ 4130 with Suzaku. Owing to Suzaku's high sensitivity for the detection of diffuse X-ray emission, we found two small structures in the TeV emitting region. One of them is coincident with a $\gamma$ -ray pulsar, PSR J2032 $+$ 4127, which was discovered by the Fermi Gamma-ray Space Telescope. By subtracting the contribution of point sources estimated by Chandra data, we obtained the diffuse X-ray spectrum. The X-ray spectrum can be reproduced by a power-law model with a photon index of $\sim\ $ 2, and an X-ray flux of 2 $\times$ 10 $^{-13}\ $ erg s $^{-1}\ $ cm $^{-2}$ . The ratio of the $\gamma$ -ray flux to the X-ray flux is about 10. If the origin of the TeV $\gamma$ -rays is inverse Compton scattering of the microwave background by high-energy electrons, the ratio corresponds to a magnetic field strength of $\sim\ $ 1 $\ \mu$ G. However, the smaller size of the X-ray emission than that of the TeV emission suggests that the energy loss of the electrons can explain the large ratio of the $\gamma$ -ray flux with a reasonable magnetic field strength of a few microgauss.
A New Candidate of an X-Ray Luminous Cluster of Galaxies behind the Galactic Plane
Authors: Yamauchi Shigeo , Bamba Aya , Koyama Katsuji 
Published: March 2014

Abstract
We present Suzaku results of an X-ray source, AX J185905 $+$ 0333, discovered in the ASCA galactic plane survey. The radial profile of AX J185905 $+$ 0333 is larger than that of the point-spread function. No intensity variation was found during the observation. These facts indicate that AX J185905 $+$ 0333 is an extended source. A large low-energy absorption, equivalent to $N_{\rm H}$ of (8–10) $\times$ 10 $^{22}\ $ cm $^{-2}$ , was found, which supports that AX J185905 $+$ 0333 is an extragalactic object behind the galactic plane. The X-ray spectrum exhibits a clear emission line at 4.82 keV, and is represented by a thin-thermal plasma model of 6.6 keV temperature with a redshift of 0.391. Then, the X-ray luminosity was calculated to be 2.7 $\times$ 10 $^{45}\ $ erg s $^{-1}$ . These results strongly support that AX J185905 $+$ 0333 is an X-ray luminous cluster of galaxies behind the galactic plane.
Isolated Millimeter Flares of Cyg X-3
Authors: Tsuboi Masato , Kamegai Kazuhisa , Miyazaki Atsushi , Nakanishi Kouichiro , Kotani Taro 
Published: March 2014

Abstract
Cygnus X-3 (Cyg X-3) is a well-known microquasar with relativistic jets. It is especially famous for its giant radio outbursts, which have been observed once every few years since their first discovery. Each giant outburst presumably consists of a series of short-duration flares. The physical parameters of the flares in the giant outbursts are difficult to derive because the successive flares overlap. Here, we report on isolated flares in the quiescent phase of Cyg X-3, as observed at 23, 43, and 86 GHz with the 45-m radio telescope at Nobeyama Radio Observatory. The observed flares have small amplitude (0.5–2 Jy) and short duration (1–2 hr). The millimeter fluxes rapidly increase, and then exponentially decay. The lifetime of the decay is shorter at higher frequency. The radio spectrum of Cyg X-3 during the flares is flat or inverted around the peak flux density. After that, the spectrum gradually becomes steeper. The observed characteristics are consistent with those of an adiabatic expanding plasma. The brightness temperature of the plasma at the peak is estimated to be $T_{\rm B}$ $\gtrsim$ 1 $\times$ 10$^{11}\ $K. The magnetic field in the plasma is calculated to be 0.2 $\lesssim$ $H$ $\lesssim$ 30 G.
Non-Equilibrium Ionization State and Two-Temperature Structure in the Bullet Cluster 1E 0657−56
Authors: Akahori Takuya , Yoshikawa Kohji 
Published: March 2014

Abstract
We investigate a non-equilibrium ionization state and an electron–ion two-temperature structure of the intracluster medium in the merging galaxy cluster, 1E 0657$-$56 (Bullet cluster), using a series of $N$-body and hydrodynamic simulations. We find that the electron temperature at the shock layer associated with the X-ray sub-peak (bullet) is quite different depending on the thermal relaxation model between electrons and ions; $\sim $25 keV for the Coulomb thermal relaxation model and $\sim $45 keV for the instantaneous thermal relaxation model in the simulations which reproduce the observed X-ray morphology. Furthermore, both of Fe XXV and Fe XXVI are overabundant compared with the ionization equilibrium state around the shock layer, and thus, the intensity ratio between Fe XXV and Fe XXVI K$\alpha$ lines are significantly altered from that in the ionization equilibrium state. We also carry out the simulations with various sets of merger parameters, and discuss a possible range of the non-equilibrium effects in this system. Our results could be tested with future X-ray observations such as Astro-H with better sensitivity in high energy band.